Ciguatera on Ambae Island, Vanuatu: Trends, Epidemiology, and Indigenous Healing Practices (2015–2024)

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This study explores how combining biomedical (clinical data) and indigenous (community survey data) approaches can enhance ciguatera management on Ambae Island, Vanuatu. We employed a mixed-methods approach that included reviewing health facility records and conducting community surveys. We collected data from the island's three area councils (East, North, and West) and from seven health facilities serving these regions. Results show that between 2015 and 2024, CFP cases peaked in April, May, October, and November, with the highest annual cases in 2017 and 2024. Nduindui and Walaha Health Centres in the West Ambae reported the most CFP cases, followed by the Lolopuepue Health Centre in North Ambae. The West Ambae Area Council had the highest incidence rates (approximately 937 per 100,000 people per month and 765 per 100,000 people per year) compared to lower rates in the North and East Area Councils. Our community survey shows that out of the 97 people interviewed, 85% have experience symptoms of ciguatera and 23 local plants have been used to treat CFP symptoms. To deepened understanding of ciguatera (both in Vanuatu and throughout the Pacific), further on other islands in Vanuatu and the Pacific is recommended to compare incidence rates and improve CFP across the region. Epidemiology Tropical Medicine Ciguatera Fish Poisoning Trends Epidemiology and Indigenous Healing Practices Health Risk Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 INTRODUCTION Ciguatera Fish Poisoning (CFP) remains one of the most common seafood-related illnesses in tropical and subtropical regions (Chinain et al., 2021 a; Friedman et al., 2017 a). However, it is underreported and not well understood in many parts of the world. In Vanuatu, few detailed studies on CFP have been done despite increasing concern about its public health impact. The latest epidemiological research used data collected between 1986 and 1995 from Northern District Hospital and Lolowai Hospital (Goodman et al., 2003 ). In contrast, wider regional studies only included data from Vanuatu, covering 1998 to 2008 (Skinner et al., 2011 a). A more recent study examined combining traditional knowledge (TK), also called Indigenous knowledge (IK), with scientific early warning systems to better understand CFP outbreaks in the country. (Rarai et al., 2024 a). Despite its likely high incidence, the contemporary epidemiology of CFP in Vanuatu remains poorly characterized, hindering effective public health planning and resource allocation. This study aims to highlight ways forward for public health authorities in resource-limited areas to work with local communities to develop policies that recognize ITK as an alternative to managing ciguatera in remote communities. We situated our study within the One Health framework to combine biomedical data with community survey data. This approach recognizes the interconnectedness of human health, ecosystems factors and cultural knowledge (Assmuth et al., 2020 ). Numerous studies have demonstrated a strong alignment between traditional ecological knowledge to biomedical leading to human health (Bourdy et al., 1992 ; Friedman et al., 2017 b; Lako et al., 2023 a). Understanding ITK is essential for informing health authorities and communities in the management of public health risk such as ciguatera fish poisoning. Greater consultation and collaboration between health authorities and communities are needed to ensure mutual understanding and appreciation of their respective roles in the management of CFP. Ciguatera is caused by the consumption of reef fish contaminated by ciguatoxins, which originate from marine dinoflagellates that thrive in disturbed coral reef environments (Chinain et al., 2021 b). The illness can produce a wide range of gastrointestinal, neurological, and cardiovascular symptoms, typically within hours of eating toxic fish (Chan, 2015 a). Although many patients receive treatment at health facilities, others rely heavily on traditional remedies, especially in remote island communities where medical support is limited. While gastrointestinal symptoms such as vomiting and diarrhea are commonly reported, many patients also experience itching, tingling, muscle weakness, or a sensation of cold that may persist for days or even weeks (Friedman et al., 2017 c). Community health profiling with local remedies can improve health strategies and intervention in remote areas of the Pacific. Across the Pacific and other tropical regions, traditional knowledge systems have long included local remedies to manage the effects of fish poisoning. For instance, extracts from the aerial roots of the mulberry tree (Broussonetia papyrifera) in Fiji are mixed with the juice and flesh of a mature coconut ( Cocos nucifera ) (Lako et al., 2023 b). The bark and leaves of the golden apple tree ( Spondias cytherea Sonnerat) in New Caledonia are commonly used in traditional treatments of ciguatera fish poisoning as well (Bourdy et al., 1992 b; Kumar-Roiné et al., 2010 ; Kumar-Roiné et al., 2011 ). While these remedies have been used for generations, most have not yet undergone pharmacological testing to assess their clinical effectiveness. Nevertheless, community members continue to apply these treatments as a first line of defense, especially when symptoms are familiar and access to formal care is limited or delayed. We provide a critical public health update on CFP in Vanuatu, revealing high incidence, significant underreporting due to reliance on traditional medicine, and identifiable environmental risk factors that can inform surveillance. This research aims to present an updated epidemiological profile of CFP from 2015 to 2024, based on data from seven health facilities across three area councils: West, North, and East Ambae. This includes identifying patterns in the number and timing of reported cases and documenting the range of symptoms experienced by affected individuals. This also presents communities survey data on the experiences of ciguatera symptoms and the management of these symptoms through the use of local remedies. By capturing both biomedical data and lived experiences, this research contributes to a more holistic understanding of CFP and how local communities respond to it. It demonstrates the value of integrating traditional knowledge with scientific approaches in addressing environmental health risk management (Rarai et al., 2024 b). It also provides a foundation for future comparative studies across the Vanuatu and the wider Pacific region. MATERIALS AND METHODS Study Site Ambae is one of the islands in Vanuatu, with a total population of 9,856 people as per the 2020 national population census (VNSO, 2020a). The study area focused on three area councils on Ambae (East, North, and West), which collectively have 8,645 residents (about 88% of the island’s population). The East Area Council has 2,075 people (24% of the study population), the North has 3,249 (36%), and the West has 3,321 (38%) (VNSO, 2020b). These three councils were chosen because they historically reported the highest numbers of ciguatera cases, whereas the South Ambae Area Council had relatively few reported cases. More than 90% of Ambae’s inhabitants live along the coast and rely on subsistence farming and fishing for their livelihoods. Figure 1 shows the three study areas (East, North, and West) and the locations of the health facilities involved in the research. In 2017 and 2018, Ambae experienced two volcanic eruptions (Moussallam et al., 2019 a), which forced the government to evacuate the entire island population to the nearby islands of Santo, Maewo, and Pentecost. Transportation on Ambae is primarily by sea; only limited parts of the island (including the study areas) have road access. The few roads that do exist enable residents to transport agricultural products to semi-commercial centres for sale. “[ Insert Fig. 1 here]” Methods A mixed-methods approach was employed for data collection for this study. We administered a questionnaire (including both closed- and open-ended questions) to community members in the three selected area councils on Ambae. In parallel, records of monthly CFP case admissions from 2015 to 2024 were obtained from seven local health facilities: Walaha, Lolopuepue, Lolovange, Vandue, Naleleo, Nduindui, and Lolowai (see Fig. 1 for locations). Additional demographic and epidemiological information was gathered using two structured questionnaires (Research Questionnaire 1: Parts 1, 2, and 4; and Research Questionnaire 2: Part 1), which focused on community knowledge and monitoring of ciguatera outbreaks. The qualitative data were also used to interpret patterns in quantitative (Clinical data) on underreporting of ciguatera cases in the study area. Each method should be chosen for what it contributes to answering the overall question, and mixed-method studies require clarity about when each method is employed and how they complement each other (Cameron, 2011 ). The qualitative and quantitative provide an avenue to understand better the management of ciguatera fish poisoning in Ambae Island. The research ethics was approved by the University of the South Pacific Research Unit and Ethics Committee [Reference: SAGEONS/2023/07/S96004461], and all participants provided informed consent before taking part. Before each survey, the study's purpose was explained to participants, and they were informed of their right to withdraw at any time and assured of the confidentiality of their responses. In total, 97 individuals were surveyed during the two fieldwork visits, comprising 49 men (51%) and 48 women (49%). These surveys were conducted in October 2023 and June 2025; during the second visit, with the help of a local guide, a higher proportion of women (40 women, 67%) was recruited than men (20 men, 33%). This approach ensured a more balanced gender representation among the participants. Traditional knowledge holders and long-term residents were well represented among the participants. During the interviews, we collected information on each participant’s background, including how long they had lived in the area, how frequently they consumed fish, their knowledge of marine environmental management (such as traditional methods for predicting or monitoring ciguatera outbreaks), their ability to identify fish associated with ciguatera, and their use of local remedies to treat ciguatera symptoms. Over half of the interviewees (n = 53, 55%) were 50 years of age or older, another 20 (21%) were between 40 and 50 years old, and only one participant was younger than 20. Many had spent their entire lives in the community: 41 individuals (42%) had lived in the study area for over 40 years, while 18 (19%) had resided there for less than 20 years. Regarding dietary habits, 52 participants (54%) reported eating fish at least once per week, 38 (39%) ate it approximately once per month, and 7 (7%) ate it only a few times per year. The interviews were conducted by the lead author, with assistance from a local field guide who has experience with similar projects during both the 2023 and 2025 visits. Purposive sampling was used to recruit respondents for the interviews. All interviews took place at the participants’ homes to ensure privacy and comfort. Participant responses were recorded by hand on paper forms and later transcribed. Each interview was conducted in Bislama (the national language of Vanuatu) and subsequently translated into English by the lead author. The quantitative survey data were entered into Microsoft Excel for organization, and we used OriginPro software for statistical analysis and graphing for better quality (Asmundis, 2021 ). The questionnaires on unrecorded CFP consist of structured questions, while those on traditional remedies are open-ended, allowing the interviewer to gather in-depth information about their use. The interviewer wrote down the data. The qualitative information on traditional remedies was recorded in writing and later sorted. We calculated incidence rates of ciguatera fish poisoning for Ambae Island and for each area council over the 2015–2024 period. The incidence rate (per 100,000 people) was determined by dividing the number of CFP cases in a given time frame by the population at risk and multiplying by 100,000. This approach is consistent with methods used by other ciguatera researchers (Chan, 2015 b; Chinain et al., 2021 c; Friedman et al., 2017 d). In this calculation, the total number of cases represents all confirmed CFP cases recorded over the 10-year study period, and the population at risk corresponds to the study area's total population from the 2020 census. The multiplication factor of 100,000 normalizes the incidence rate, allowing comparison with CFP incidence rates reported in other regions. RESULTS Our results are divided into two parts: the seasonal and geographic patterns of Ciguatera and the community responses and remedies to treat the CFP symptoms. Seasonal and Geographic Patterns of Ciguatera A total of 549 (6% of the total population of the three area councils) cases of ciguatera fish poisoning were recorded from January 2015 through December 2024 across the seven health facilities on Ambae Island. Figures 2a and 2b depict the temporal distribution of these cases by month and by year, respectively. November had the highest number of admissions (76 cases), followed by May (64 cases), and then April and October (61 cases each). In all other months, fewer than 50 cases were reported, with July having the lowest CFP admission count. On an annual basis, 2024 had the most reported cases (117 admissions), followed by 2017 (91 cases). By contrast, in all other years of the decade, the number of ciguatera cases remained below 50, and 2018 saw the fewest cases (only 29 admissions recorded). This information is consistent with community observations regarding emergence of ciguatera cases. An elderly resident of Lolopuepue in the North Area Council noted that the area is characterized by numerous creeks, which become inundated with run-off during rainfall seasons particularly in December, January and February. Subsequently following the rainy seasons, there is a noticeable increase in ciguatera cases within the communities, especially among fishers. Similar cases have been reported by residents in the West Area Councils. The geographic distribution of cases reveals apparent clustering by facility and area. As shown in Figure 2c, the Nduindui Health Centre (West Ambae) reported the highest cumulative number of CFP admissions over the ten years, with 239 patients treated, far more than any other facility. The Lolopuepue dispensary in North Ambae had the second-highest total with 106 cases. In comparison, Lolowai Hospital (East Ambae) and Walaha dispensary (West Ambae) each recorded a similar number (approximately 72–73 cases each). All other local clinics recorded fewer than 50 cases in total; for example, the Lolovange health centre in the North reported only 3 cases over the entire decade. This low incidence aligns with local residents’ observations, as individuals experiencing early symptoms of CFP often rely traditional remedies as their first line of defense. Aggregating by area council (Figure 2d), West Ambae accounted for the majority of the island’s CFP hospitalizations with 305 cases, compared to 148 cases in North Ambae and 84 cases in East Ambae. This spatial pattern suggests a higher burden of ciguatera in the West Area Council. It should be noted that a mass evacuation of Ambae residents in 2017–2018 due to a volcanic eruption likely disrupted local reporting and temporarily reduced case numbers during those years. However, a resident of Lone Village in the West Area council reported there was a notable increase in cases of ciguatera within the community in 2017. This surge was associated with gradual onset of volcanic eruptions that ultimately resulted in a significant volcanic ash flow during rainfall heavy, adversely impacting the local marine ecosystem. “[Insert Figure 2 here]” Temporal trends at individual health facilities further highlight the concentration of cases in specific locations. Figure 3a shows that Nduindui not only had the highest overall caseload but also experienced a steady increase in admissions over time. By 2024, Nduindui alone had admitted around 60 patients with ciguatera, marking the peak for any single facility. An exception to Nduindui dominance occurred in 2019, when Lolowai Hospital in East Ambae recorded 33 cases, exceeding Nduindui count for that year. The Walaha dispensary also consistently treated CFP patients every year (and nearly every month) of the study period, although in lower numbers than Nduindui. Figure 3b reveals that in virtually every month across the decade, Nduindui reported the most CFP cases of any facility, peaking at 47 cases in November. The three main centres – Nduindui, Walaha, and Lolowai – all showed a persistent upward trend in monthly instances toward the end of the period. In contrast, the smaller clinics (Lolopuepue, Lolovange, Vandue, and Naleleo) often went for many months without reporting any cases. Two concluding remarks can be drawn based on the low patient turnout at these clinics, first, early symptoms of CFP experienced by the local population were often managed with traditional remedies rather than seeking formal medical care. Second, a significant number of ciguatera cases appeared to be managed primarily by a few key health facilities in the three area councils. “[ Insert Figure 3 here]” The incidence of ciguatera on Ambae Island during 2015–2024 was substantial, though slightly lower than historical levels. Over the study period, the mean annual incidence was approximately 635 cases per 100,000 people, compared with about 699 per 100,000 during 1998–2008, as reported in a previous study (Skinner et al., 2011b). The island’s mean monthly incidence rate for 2015–2024 was 517 cases per 100,000 people (Table 1). Notably, incidence rates spiked in certain years of our record: 2017 (the third year of the study) and especially 2024 (the final year), each of which showed markedly higher annual incidence rates than other years (Figure 4a). Marked differences in ciguatera risk were observed between the three area councils of Ambae (Table 2). West Ambae consistently had the highest incidence, with a mean annual incidence of 937 cases per 100,000 inhabitants over the ten years. In comparison, the North Ambae council had an average annual incidence of 474 per 100,000, and East Ambae had the lowest at 405 per 100,000. A similar ranking was seen in the mean monthly incidence rates: West Ambae averaged 765 cases per 100,000 per month, significantly higher than North Ambae (380) and East Ambae (333). These figures highlight that West Ambae faces an exceptionally high rate of ciguatera cases. Looking across the calendar year, the months of April, October, and November (Figure 4b) had the highest ciguatera incidence rates on Ambae; in most other months, incidence remained comparatively low (often below 50 cases per 100,000) during the study period. This seasonal pattern aligns with the admission data, underlining that late and beginning of wet season are peak times for CFP occurrences on the island. “[Insert Figure 4 here]” To integrative support the health facilities data and practices, we gathered information on ciguatera symptoms and treatment options from community members through an interview survey. A total of 97 residents (49 men and 48 women) were interviewed across the West, North, and East area councils during fieldwork in October 2023 and June 2025. Over half (approximately 55%) of these participants were over 50 years old (Figure 5b), and nearly all (over 90%) had lived in their community for more than 20 years (Figure 5c). All respondents were familiar with fish as a food source, though there were some gender differences in fish consumption. According to the survey, men reported eating fish more frequently (usually weekly), whereas women were more likely to eat it only monthly or a few times per year. In fact, every man interviewed had regular access to fish in his diet, whereas a handful of women either lacked access to fish or chose not to consume it for various reasons (Figure 5d). Based on the community survey, most participants interviewed had first-hand experience with ciguatera. In total, 82 out of 97 participants (approximately 85%) reported that they had suffered symptoms of ciguatera fish poisoning at least once in their lifetime and had used local remedies to treat these symptoms (Figure 5a). This affected group included 46 of the 49 men and 36 of the 48 women surveyed, meaning roughly 94% of the interviewed men and 75% of the interviewed women had experienced CFP (Figure 6b). Out of this figures, 58% (48) of the cases are reported from the North Area Council. The most commonly described symptoms were joint pain (especially in the elbows and knees, reported by 50 individuals) and muscle pain or weakness (47 individuals). Many participants also experienced intense itching or a prickling “needle-like” sensation in the skin (noted by 40 people), diarrhea (39 people), an abnormal cold sensation (37 people), and numbness or tingling around the mouth or nose (31 people) (Figure 6a). Several respondents additionally mentioned gastrointestinal symptoms such as vomiting, stomach pain, and even toothaches as part of their illness experience. Taken together, these accounts provide a detailed picture of the multi-system effects of ciguatera intoxication in the community. Community Responses and Remedies Our results showed that 85% of the people interviewed in the three area councils rely on local remedies as their first line of defences against CFP symptoms. These results suggest that many cases of ciguatera are not recorded in official clinic records, as affected individuals often treat themselves at home rather than seeking formal medical care. Indeed, many people reported preferring local (traditional) remedies for initial symptom relief when they suspected that the fish they had eaten was ciguatoxic. One interviewee from West Ambae noted that fish poisoning incidents have increased significantly in their area since residents returned after the 2017–2018 evacuation (following a volcanic eruption). However, few of these recent cases were reported to health facilities, as community members generally rely on customary treatments. Participants explained that most villagers use leaves, tree barks, and other plant-based preparations to address the early signs of ciguatera, only turning to clinics or hospitals if symptoms worsen (Figure 6c). Both men and women appeared equally likely to have experienced ciguatera at least once or twice in their lives, underscoring that CFP affects a broad cross-section of the community. The heavy reliance on home remedies also reflects a strong local knowledge of ciguatera management outside of the formal healthcare system. Based on the quantitative data, ciguatera cases remain underreported in health facilities on Ambae, particularly in the three area councils. Survey data show that 85% of the adult population has experienced CFP with no clinical records. This represents a substantial cumulative disease burden, amounting to thousands of cases over time. For example, in a community of 10,000 adults, approximately 8,500 individuals would have been affected, far exceeding the few hundred documented in clinical records. This disparity demonstrates that clinic-based surveillance captures only a small fraction of the total number of cases- the “tip of the iceberg”. Many affected individuals may not seek medical care due to mild or self-limiting symptoms, reliance on traditional remedies, or limited access to health services. These findings highlight the importance of integrating community-based surveys and population-level data to obtain a more accurate understanding of CFP patterns for effective public health interventions. “[Insert Figure 5 here]” “[Insert Figure 6 here]” A diverse range of traditional remedies for ciguatera fish poisoning was documented on Ambae Island. During our field study, we identified 23 different plants that locals use to alleviate symptoms of ciguatera. Various parts of these plants are utilized – including leaves, young shoots, inner tree bark, and even fruits – depending on the species and the symptom being treated. Both men and women in the community are actively involved in preparing and administering these remedies as a first response to suspected CFP cases. Table 3 provides a detailed list of all recorded remedies, noting each plant’s scientific and local name, the parts used and preparation methods, and the specific ciguatera symptoms that each remedy is believed to relieve. For example, one commonly used treatment involves extracting the juice from crushed tropical white weed leaves ( Ageratum conyzoides ) and drinking it to help relieve joint pain and muscle fatigue. This and other such practices highlight the extensive ethnobotanical knowledge present on Ambae for dealing with toxin-related fish illnesses. Several of the identified remedies were particularly common and frequently mentioned by participants. The most widely cited treatment was papaya ( Carica papaya ): 11 individuals reported using papaya leaves, fruits, or roots to help relieve muscle pain and restore strength during recovery from ciguatera. Another popular remedy is the seashore lily ( Crinum asiaticum ); its leaves or roots are typically boiled and the decoction consumed, and eight participants used this method to alleviate general body pain and weakness. The glue berry tree ( Cordia dichotoma ) was cited by 6 participants, who use its leaves and inner bark to ease joint pain and improve strength. The inner bark of the Tiger’s Claw tree ( Erythrina variegata ) and coconut milk were each used by 5 participants as treatments to reduce muscle pain, stop diarrhea and vomiting, and boost energy during CFP bouts. The milky sap from broken frangipani ( Plumeria ) leaves was reportedly used by four people, who described collecting it and drinking it to reduce muscle pain, increase strength, and ease gastrointestinal symptoms. These remedies were the first-line treatment for 85% of affected individuals, often administered repeatedly, with formal care sought only if symptoms worsened. In addition to these major treatments, a handful of other plants were mentioned by only a few respondents. For instance, wild yam ( Dioscorea villosa ), cut nut ( Barringtonia edulis ), and golden apple ( Spondias dulcis ) were each cited by three participants as helpful in relieving ciguatera symptoms. Most of the remaining remedies in our survey (such as certain herbs and bush medicines not detailed above) were mentioned by just one or two individuals. This suggests that knowledge of some of these more obscure treatments may be limited to certain families or villages. Overall, however, local remedies clearly represent an essential first line of defense against ciguatera on Ambae. The community’s extensive use of plant-based treatments complements the care provided by health facilities, and it highlights the value of indigenous knowledge in managing and recovering from CFP in Vanuatu’s rural islands. Engagement with traditional healers could be a novel strategy for syndromic surveillance, as they are often the first to see cases of CFP before referring to the health facilities. TABLE 3. Local Remedies used by local people on Ambae to treat symptoms of Ciguatera Fish Poisoning DISCUSSION Our findings indicate clear seasonality in ciguatera fish poisoning (CFP) incidences in Vanuatu, with higher case counts observed in April, May, October, and November between 2015 and 2024. This pattern mirrors trends reported in French Polynesia, where peak densities of Gambierdiscus were observed in January, April, and October from 1993 to 1997 (Chinain et al., 1999 ). Similarly, in Japan, Gambierdiscus densities increase during summer (June-August) and autumn (September-November), coinciding with higher sea surface temperatures and more CFP cases (Nishimura et al., 2018 ). Two key climatic factors likely contribute to the proliferation of Gambierdiscus during these months-warmer sea surface temperatures and coral reef disturbances caused by tropical cyclones. Damaged coral promotes algal growth, which attracts herbivorous fish that can subsequently accumulate ciguatoxins (Berdalet et al., 2017 ). In Vanuatu, the wet and cyclone season runs from November to April, corresponding to the local summer when sea surface temperatures are elevated, similar to Japan’s summer (June-August). Moreover, rainfall and runoff during these periods deliver nutrients and sediments that further enhance dinoflagellate growth (Comeros-Raynal et al., 2019 ; Fabricius et al., 2008 ). Public health authorities, local governments, and government agencies responsible for weather and climate forecasts should develop targeted public health messaging for months that record the highest CFP case counts. This includes integration of CFP awareness into climate adaptation and disaster response plans. Volcanic eruptions also appear to influence CFP dynamics. The 2017–2018 eruptions (Moussallam et al., 2019 b) may explain the peak in CFP cases observed in 2017. Volcanic activity can induce harmful algal blooms by releasing sulfur and iron into seawater, enriching nutrient levels (Kim, 2020 ). In the Northern Mariana Islands, volcanic ash has been shown to introduce diverse chemical compounds that alter benthic community composition, promoting dinoflagellate proliferation (Schils, 2012 ). Another notable CFP increase in 2014 is likely related to the strong 2023 El Niño event (Hu et al., 2024 ). Climate phenomena such as El Niño raise sea surface temperatures, expanding the distribution of toxic dinoflagellates and increasing the level of ciguatoxins in fish (Kibler et al., 2015 ; Zheng et al., 2020 ). Volcanic activity and elevated surface temperatures contribute indirectly to increased CFP incidences. Volcanic eruptions trigger post-disaster health alerts about increased CFP risk. Strengthening information-sharing mechanisms among agencies and communities is therefore essential for mitigating future outbreaks. The distribution of CFP cases across the three area councils reflects both population distribution and healthcare-seeking behaviour. A high reliance on local remedies for CFP symptom management suggests significant underreporting of cases, consistent with findings from Florida, United States of America, where incidence rates require adjustment for underreporting (Radke et al., 2015 ). Geographically, higher cases of CFP in the West and North Area Council compared to the East may be attributed to their proximity to the volcano (Fig. 1), and numerous creeks facilitate nutrient and sediment transport, and greater exposure to volcanic ash due to prevailing east and southeast winds (Loughlin et al., 2015 ; Tepe & Bau, 2014 ). Additionally, a mudflow in Walubue (North Area Council) in 2017 (Roy & Jong, 2018 ) and a volcanic sediment flow in Lone (West Area Council) in early 2018 further disturbed the marine ecosystem, likely contributing to CFP cases. Both human behaviour and natural hazards may contribute to the number of cases of ciguatera. This required the health authorities and the local government to increase awareness of the reporting of ciguatera cases across the island. Overall, CFP incidence in Vanuatu has risen steadily from 1970 to 2024. During this period, Penama Province – where our study site is located – recorded the highest rate among all six provinces (699 cases per 100,000). This aligns with observations from French Polynesia, where peaks in Gambierdiscus density during 1993–1996 corresponded with elevated CFP cases (Chinain et al., 1999 ), and with high CFP activity in the United States from 2001–2011 (Gingold et al., 2014 ). These patterns suggest that climate change and improved surveillance by the Vanuatu Ministry of Health have both contributed to the observed increase in CFP reporting. Community-based surveys of individuals affected by CFP and the local remedies they used to treat symptoms may complement clinical CFP data to help reduce underreporting by health facilities. Community-based data are easier to access and more geographically representative of the overall population (Gutilla et al., 2017 ). Furthermore, integrating clinical and survey data helps identify, monitor, and improve the range of medical, environmental, and social factors relevant to community health activities, and to gather in-depth, context-rich information about each case (Gamache et al., 2018 ; Matheson et al., 2018 ). This shows that qualitative data often enhanced alternative theoretical framework and measures alongside quantitative data (Muntaner & Gómez, 2003 ). Local remedies have been used for generations by communities, providing an option for public health intervention in cases where government health services are limited. A need for effective strategies to create platforms for greater dialogue between health authorities and indigenous knowledge practitioners of local medicines. No significant gender difference was detected in CFP incidents, despite men generally having greater access to fish. This is consistent with studies showing no significant difference in fish consumption between males and females in Vanuatu (Frackiewicz et al., 2023 ). Approximately 72% of rural households engage in fishing primarily for protein, while 39% depend on fisheries for income (Charlton et al., 2016 ). This high reliance on marine resources across genders likely explains the widespread risk of CFP (Chinain et al., 2020 ; Gillett, 2009 ). To mitigate this risk, collaborative communication and early-warning frameworks, such as the Gigila Framework (Rarai et al., 2024 c), should be promoted to enhance community awareness of CFP outbreaks. Local remedies remain a critical first-line response to CFP symptoms in remote and rural Vanuatu communities with limited access to healthcare. Many traditional treatments have demonstrated inhibitory activity against ciguatoxic effects (Bourdy et al., 1992 b; Kumar-Roiné et al., 2009 ). For example, the golden apple ( Spondias dulcis ) leaves and bark are used in New Caledonia, while coconut juice and flesh are traditional treatments in Fiji (Lako et al., 2023 b). Similarly, most respondents in our study reported using local remedies to alleviate CFP symptoms, highlighting their cultural and practical significance in community-based health responses. Collaborating with Indigenous knowledge holders could improve surveillance of ciguatera as they might notice environmental precursors to outbreaks (Rarai et al., 2024 d), or that recognizing traditional remedies could inform healthcare delivery by prompting formal testing of a popular herbal remedy for efficacy/safety. CONCLUSION Our findings underscore the need for integrated surveillance that incorporates community-level data and traditional knowledge to better gauge the true burden of CFP in Vanuatu. Our recommendations are to enhance surveillance through integrated reporting that captures cases from both health clinics and community-based reporting mechanisms, and to develop targeted public health awareness and campaigns before and during high–risk seasons (April-May, October to November). Furthermore, issue post-disaster warnings by issuing specific CFP warnings following volcanic activity, cyclones, and strong El Niño events. Collaborative research among scientists, local knowledge holders, and government agencies is essential to advance understanding of ciguatoxins. Further Pharmacological studies on the most cited traditional remedies (e.g., Carica papaya , Crinum asiaticum ) to explore potential supportive treatments. Strengthening scientific capacity in these fields will enhance the recognition, confirmation, and treatment of ciguatera poisoning, while also improving seafood safety and understanding of environmental factors that lead to CFP. References Asmundis, R. de. 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16:28:50","extension":"html","order_by":58,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":160790,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/f53dae20f0aa51f3241faac4.html"},{"id":97346047,"identity":"08f20fdc-39b2-463e-877d-cb46ecb289bf","added_by":"auto","created_at":"2025-12-03 11:47:26","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":84984,"visible":true,"origin":"","legend":"\u003cp\u003eA map showing the three Area Councils and health facilities on Ambae Island, and map of Vanuatu and South Pacific.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/855e4b312d5e35e0f4a7a4a0.jpg"},{"id":97346048,"identity":"a794a811-eead-4af0-acb4-794256c0ddb1","added_by":"auto","created_at":"2025-12-03 11:47:26","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":195139,"visible":true,"origin":"","legend":"\u003cp\u003eGraph demonstrating \u003cstrong\u003e(a)\u003c/strong\u003e Monthly Admission Pattern, \u003cstrong\u003e(b)\u003c/strong\u003e Annual Admission Pattern, \u003cstrong\u003e(c)\u003c/strong\u003e Admission to Health facilities, and \u003cstrong\u003e(d)\u003c/strong\u003e Admission by Area Councils with a diagnosis of ciguatera fish poisoning on Ambae Island, Vanuatu, 2015-2024. (\u003cem\u003en\u003c/em\u003e is the number of CFP cases)\u003c/p\u003e","description":"","filename":"Fig2final.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/23d5c3c4f5aeb869bcb7bf88.jpg"},{"id":97346051,"identity":"c6209f78-8c47-4ac5-b663-8298e48e98f9","added_by":"auto","created_at":"2025-12-03 11:47:27","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":244146,"visible":true,"origin":"","legend":"\u003cp\u003eGraph demonstrating the admission with diagnosis of fish poisoning for 2015 to 2024 on an \u003cstrong\u003e(a)\u003c/strong\u003e annual and \u003cstrong\u003e(b)\u003c/strong\u003e seasonal time scale for the health facilities.\u003c/p\u003e","description":"","filename":"Fig3Final.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/5a0e4ba56eecadf072c227d7.jpg"},{"id":97346049,"identity":"c6473a7f-571c-4742-9b91-85bd2c9efd8f","added_by":"auto","created_at":"2025-12-03 11:47:27","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":189204,"visible":true,"origin":"","legend":"\u003cp\u003eGraph showing the Ciguatera Fish Poisoning cases and mean \u003cstrong\u003e(a)\u003c/strong\u003e Annual \u003cstrong\u003e(b)\u003c/strong\u003e monthly incidence rate/100,000 combined for 3 area councils.\u003c/p\u003e","description":"","filename":"Fig4Final.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/af6b3a360a4fb374e7654549.jpg"},{"id":97370188,"identity":"a99432dc-de19-456c-a41f-71afc3c04fbf","added_by":"auto","created_at":"2025-12-03 16:26:52","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":184758,"visible":true,"origin":"","legend":"\u003cp\u003eGraph showing the\u003cstrong\u003e (a)\u003c/strong\u003e Number of Interviewees, \u003cstrong\u003e(b)\u003c/strong\u003e Age, \u003cstrong\u003e(c)\u003c/strong\u003e Duration of time, and \u003cstrong\u003e(d)\u003c/strong\u003e frequency of access to the fish for people of the 3 area councils.\u003c/p\u003e","description":"","filename":"Fig5Final.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/6a7017ee8d1beecfbc366ca7.jpg"},{"id":97346083,"identity":"b023b547-f5c1-472c-8995-a74604f6e9e6","added_by":"auto","created_at":"2025-12-03 11:47:27","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":417935,"visible":true,"origin":"","legend":"\u003cp\u003eGraphs demonstrating the \u003cstrong\u003e(a)\u003c/strong\u003e Symptoms of CFP, \u003cstrong\u003e(b)\u003c/strong\u003e CFP symptoms experienced based on gender, and \u003cstrong\u003e(c)\u003c/strong\u003eFrequency of people based on the local remedies used.\u003c/p\u003e","description":"","filename":"Fig6Final.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/a1eb7bae6f8404533272371b.jpg"},{"id":97664839,"identity":"7c0100c3-c654-48cc-9253-33d9ce7f2265","added_by":"auto","created_at":"2025-12-08 09:14:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1859033,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/80fa792c-fe80-458b-b885-2b8cbafd2bec.pdf"},{"id":97346055,"identity":"92d178a2-f335-482b-8784-83e8f32d69d2","added_by":"auto","created_at":"2025-12-03 11:47:27","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3449649,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-8250358/v1/e3773057dce54a8b1c21c4e2.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eCiguatera on Ambae Island, Vanuatu: Trends, Epidemiology, and Indigenous Healing Practices (2015–2024)\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eCiguatera Fish Poisoning (CFP) remains one of the most common seafood-related illnesses in tropical and subtropical regions (Chinain et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003ea; Friedman et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003ea). However, it is underreported and not well understood in many parts of the world. In Vanuatu, few detailed studies on CFP have been done despite increasing concern about its public health impact. The latest epidemiological research used data collected between 1986 and 1995 from Northern District Hospital and Lolowai Hospital (Goodman et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). In contrast, wider regional studies only included data from Vanuatu, covering 1998 to 2008 (Skinner et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2011\u003c/span\u003ea). A more recent study examined combining traditional knowledge (TK), also called Indigenous knowledge (IK), with scientific early warning systems to better understand CFP outbreaks in the country. (Rarai et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003ea). Despite its likely high incidence, the contemporary epidemiology of CFP in Vanuatu remains poorly characterized, hindering effective public health planning and resource allocation. This study aims to highlight ways forward for public health authorities in resource-limited areas to work with local communities to develop policies that recognize ITK as an alternative to managing ciguatera in remote communities.\u003c/p\u003e\u003cp\u003eWe situated our study within the One Health framework to combine biomedical data with community survey data. This approach recognizes the interconnectedness of human health, ecosystems factors and cultural knowledge (Assmuth et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Numerous studies have demonstrated a strong alignment between traditional ecological knowledge to biomedical leading to human health (Bourdy et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Friedman et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003eb; Lako et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003ea). Understanding ITK is essential for informing health authorities and communities in the management of public health risk such as ciguatera fish poisoning. Greater consultation and collaboration between health authorities and communities are needed to ensure mutual understanding and appreciation of their respective roles in the management of CFP.\u003c/p\u003e\u003cp\u003eCiguatera is caused by the consumption of reef fish contaminated by ciguatoxins, which originate from marine dinoflagellates that thrive in disturbed coral reef environments (Chinain et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003eb). The illness can produce a wide range of gastrointestinal, neurological, and cardiovascular symptoms, typically within hours of eating toxic fish (Chan, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2015\u003c/span\u003ea). Although many patients receive treatment at health facilities, others rely heavily on traditional remedies, especially in remote island communities where medical support is limited. While gastrointestinal symptoms such as vomiting and diarrhea are commonly reported, many patients also experience itching, tingling, muscle weakness, or a sensation of cold that may persist for days or even weeks (Friedman et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003ec). Community health profiling with local remedies can improve health strategies and intervention in remote areas of the Pacific.\u003c/p\u003e\u003cp\u003eAcross the Pacific and other tropical regions, traditional knowledge systems have long included local remedies to manage the effects of fish poisoning. For instance, extracts from the aerial roots of the mulberry tree \u003cem\u003e(Broussonetia papyrifera)\u003c/em\u003e in Fiji are mixed with the juice and flesh of a mature coconut (\u003cem\u003eCocos nucifera\u003c/em\u003e) (Lako et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003eb). The bark and leaves of the golden apple tree (\u003cem\u003eSpondias cytherea Sonnerat)\u003c/em\u003e in New Caledonia are commonly used in traditional treatments of ciguatera fish poisoning as well (Bourdy et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1992\u003c/span\u003eb; Kumar-Roin\u0026eacute; et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Kumar-Roin\u0026eacute; et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). While these remedies have been used for generations, most have not yet undergone pharmacological testing to assess their clinical effectiveness. Nevertheless, community members continue to apply these treatments as a first line of defense, especially when symptoms are familiar and access to formal care is limited or delayed.\u003c/p\u003e\u003cp\u003eWe provide a critical public health update on CFP in Vanuatu, revealing high incidence, significant underreporting due to reliance on traditional medicine, and identifiable environmental risk factors that can inform surveillance. This research aims to present an updated epidemiological profile of CFP from 2015 to 2024, based on data from seven health facilities across three area councils: West, North, and East Ambae. This includes identifying patterns in the number and timing of reported cases and documenting the range of symptoms experienced by affected individuals. This also presents communities survey data on the experiences of ciguatera symptoms and the management of these symptoms through the use of local remedies. By capturing both biomedical data and lived experiences, this research contributes to a more holistic understanding of CFP and how local communities respond to it. It demonstrates the value of integrating traditional knowledge with scientific approaches in addressing environmental health risk management (Rarai et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003eb). It also provides a foundation for future comparative studies across the Vanuatu and the wider Pacific region.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy Site\u003c/h2\u003e\u003cp\u003eAmbae is one of the islands in Vanuatu, with a total population of 9,856 people as per the 2020 national population census (VNSO, 2020a). The study area focused on three area councils on Ambae (East, North, and West), which collectively have 8,645 residents (about 88% of the island\u0026rsquo;s population). The East Area Council has 2,075 people (24% of the study population), the North has 3,249 (36%), and the West has 3,321 (38%) (VNSO, 2020b). These three councils were chosen because they historically reported the highest numbers of ciguatera cases, whereas the South Ambae Area Council had relatively few reported cases.\u003c/p\u003e\u003cp\u003eMore than 90% of Ambae\u0026rsquo;s inhabitants live along the coast and rely on subsistence farming and fishing for their livelihoods. Figure\u0026nbsp;1 shows the three study areas (East, North, and West) and the locations of the health facilities involved in the research. In 2017 and 2018, Ambae experienced two volcanic eruptions (Moussallam et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003ea), which forced the government to evacuate the entire island population to the nearby islands of Santo, Maewo, and Pentecost. Transportation on Ambae is primarily by sea; only limited parts of the island (including the study areas) have road access. The few roads that do exist enable residents to transport agricultural products to semi-commercial centres for sale.\u003c/p\u003e\u003cp\u003e\u003cb\u003e\u0026ldquo;[ Insert Fig.\u0026nbsp;1 here]\u0026rdquo;\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eMethods\u003c/h3\u003e\n\u003cp\u003eA mixed-methods approach was employed for data collection for this study. We administered a questionnaire (including both closed- and open-ended questions) to community members in the three selected area councils on Ambae. In parallel, records of monthly CFP case admissions from 2015 to 2024 were obtained from seven local health facilities: Walaha, Lolopuepue, Lolovange, Vandue, Naleleo, Nduindui, and Lolowai (see Fig.\u0026nbsp;1 for locations). Additional demographic and epidemiological information was gathered using two structured questionnaires (Research Questionnaire 1: Parts 1, 2, and 4; and Research Questionnaire 2: Part 1), which focused on community knowledge and monitoring of ciguatera outbreaks. The qualitative data were also used to interpret patterns in quantitative (Clinical data) on underreporting of ciguatera cases in the study area. Each method should be chosen for what it contributes to answering the overall question, and mixed-method studies require clarity about when each method is employed and how they complement each other (Cameron, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The qualitative and quantitative provide an avenue to understand better the management of ciguatera fish poisoning in Ambae Island.\u003c/p\u003e\u003cp\u003e The research ethics was approved by the University of the South Pacific Research Unit and Ethics Committee [Reference: SAGEONS/2023/07/S96004461], and all participants provided informed consent before taking part. Before each survey, the study's purpose was explained to participants, and they were informed of their right to withdraw at any time and assured of the confidentiality of their responses. In total, 97 individuals were surveyed during the two fieldwork visits, comprising 49 men (51%) and 48 women (49%). These surveys were conducted in October 2023 and June 2025; during the second visit, with the help of a local guide, a higher proportion of women (40 women, 67%) was recruited than men (20 men, 33%). This approach ensured a more balanced gender representation among the participants.\u003c/p\u003e\u003cp\u003eTraditional knowledge holders and long-term residents were well represented among the participants. During the interviews, we collected information on each participant\u0026rsquo;s background, including how long they had lived in the area, how frequently they consumed fish, their knowledge of marine environmental management (such as traditional methods for predicting or monitoring ciguatera outbreaks), their ability to identify fish associated with ciguatera, and their use of local remedies to treat ciguatera symptoms. Over half of the interviewees (n\u0026thinsp;=\u0026thinsp;53, 55%) were 50 years of age or older, another 20 (21%) were between 40 and 50 years old, and only one participant was younger than 20. Many had spent their entire lives in the community: 41 individuals (42%) had lived in the study area for over 40 years, while 18 (19%) had resided there for less than 20 years. Regarding dietary habits, 52 participants (54%) reported eating fish at least once per week, 38 (39%) ate it approximately once per month, and 7 (7%) ate it only a few times per year.\u003c/p\u003e\u003cp\u003eThe interviews were conducted by the lead author, with assistance from a local field guide who has experience with similar projects during both the 2023 and 2025 visits. Purposive sampling was used to recruit respondents for the interviews. All interviews took place at the participants\u0026rsquo; homes to ensure privacy and comfort. Participant responses were recorded by hand on paper forms and later transcribed. Each interview was conducted in Bislama (the national language of Vanuatu) and subsequently translated into English by the lead author. The quantitative survey data were entered into Microsoft Excel for organization, and we used OriginPro software for statistical analysis and graphing for better quality (Asmundis, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The questionnaires on unrecorded CFP consist of structured questions, while those on traditional remedies are open-ended, allowing the interviewer to gather in-depth information about their use. The interviewer wrote down the data. The qualitative information on traditional remedies was recorded in writing and later sorted.\u003c/p\u003e\u003cp\u003eWe calculated incidence rates of ciguatera fish poisoning for Ambae Island and for each area council over the 2015\u0026ndash;2024 period. The incidence rate (per 100,000 people) was determined by dividing the number of CFP cases in a given time frame by the population at risk and multiplying by 100,000. This approach is consistent with methods used by other ciguatera researchers (Chan, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2015\u003c/span\u003eb; Chinain et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003ec; Friedman et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003ed). In this calculation, the total number of cases represents all confirmed CFP cases recorded over the 10-year study period, and the population at risk corresponds to the study area's total population from the 2020 census. The multiplication factor of 100,000 normalizes the incidence rate, allowing comparison with CFP incidence rates reported in other regions.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eOur results are divided into two parts: the seasonal and geographic patterns of Ciguatera and the community responses and remedies to treat the CFP symptoms.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSeasonal and Geographic Patterns of Ciguatera\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 549 (6% of the total population of the three area councils) cases of ciguatera fish poisoning were recorded from January 2015 through December 2024 across the seven health facilities on Ambae Island. Figures 2a and 2b depict the temporal distribution of these cases by month and by year, respectively. November had the highest number of admissions (76 cases), followed by May (64 cases), and then April and October (61 cases each). In all other months, fewer than 50 cases were reported, with July having the lowest CFP admission count. On an annual basis, 2024 had the most reported cases (117 admissions), followed by 2017 (91 cases). By contrast, in all other years of the decade, the number of ciguatera cases remained below 50, and 2018 saw the fewest cases (only 29 admissions recorded). This information is consistent with community observations regarding emergence of ciguatera cases. An elderly resident of Lolopuepue in the North Area Council noted that the area is characterized by numerous creeks, which become inundated with run-off during rainfall seasons particularly in December, January and February. Subsequently following the rainy seasons, there is a noticeable increase in ciguatera cases within the communities, especially among fishers. Similar cases have been reported by residents in the West Area Councils.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe geographic distribution of cases reveals apparent clustering by facility and area. As shown in Figure 2c, the Nduindui Health Centre (West Ambae) reported the highest cumulative number of CFP admissions over the ten years, with 239 patients treated, far more than any other facility. The Lolopuepue dispensary in North Ambae had the second-highest total with 106 cases. In comparison, Lolowai Hospital (East Ambae) and Walaha dispensary (West Ambae) each recorded a similar number (approximately 72\u0026ndash;73 cases each). All other local clinics recorded fewer than 50 cases in total; for example, the Lolovange health centre in the North reported only 3 cases over the entire decade. This low incidence aligns with local residents\u0026rsquo; observations, as individuals experiencing early symptoms of CFP often rely traditional remedies as their first line of defense. Aggregating by area council (Figure 2d), West Ambae accounted for the majority of the island\u0026rsquo;s CFP hospitalizations with 305 cases, compared to 148 cases in North Ambae and 84 cases in East Ambae. This spatial pattern suggests a higher burden of ciguatera in the West Area Council. It should be noted that a mass evacuation of Ambae residents in 2017\u0026ndash;2018 due to a volcanic eruption likely disrupted local reporting and temporarily reduced case numbers during those years. However, a resident of Lone Village in the West Area council reported there was a notable increase in cases of ciguatera within the community in 2017. This surge was associated with gradual onset of volcanic eruptions that ultimately resulted in a significant volcanic ash flow during rainfall heavy, adversely impacting the local marine ecosystem. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026ldquo;[Insert Figure 2 here]\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTemporal trends at individual health facilities further highlight the concentration of cases in specific locations.\u0026nbsp;Figure 3a shows that Nduindui not only had the highest overall caseload but also experienced a steady increase in admissions over time. By 2024, Nduindui alone had admitted around\u0026nbsp;60 patients with ciguatera, marking the peak for any single facility. An exception to Nduindui dominance occurred in 2019, when\u0026nbsp;Lolowai Hospital\u0026nbsp;in East Ambae recorded\u0026nbsp;33 cases, exceeding Nduindui count for that year. The\u0026nbsp;Walaha\u0026nbsp;dispensary also consistently treated CFP patients every year (and nearly every month) of the study period, although in lower numbers than Nduindui. Figure 3b reveals that in virtually every month across the decade, Nduindui reported the most CFP cases of any facility, peaking at\u0026nbsp;47 cases\u0026nbsp;in November. The three main centres \u0026ndash; Nduindui, Walaha, and Lolowai \u0026ndash; all showed a persistent upward trend in monthly instances toward the end of the period. In contrast, the smaller clinics (Lolopuepue, Lolovange, Vandue, and Naleleo) often went for many months without reporting any cases. Two concluding remarks can be drawn based on the low patient turnout at these clinics, first, early symptoms of CFP experienced by the local population were often managed with traditional remedies rather than seeking formal medical care. Second, a significant number of ciguatera cases appeared to be managed primarily by a few key health facilities in the three area councils.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026ldquo;[ Insert Figure 3 here]\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe incidence of ciguatera on Ambae Island during 2015\u0026ndash;2024 was substantial, though slightly lower than historical levels. Over the study period, the\u0026nbsp;mean annual incidence\u0026nbsp;was approximately\u0026nbsp;635 cases per 100,000 people, compared with about\u0026nbsp;699 per 100,000\u0026nbsp;during 1998\u0026ndash;2008, as reported in a previous study (Skinner et al., 2011b). The island\u0026rsquo;s mean monthly incidence rate for 2015\u0026ndash;2024 was\u0026nbsp;517 cases per 100,000 people\u0026nbsp;(Table\u0026nbsp;1). Notably, incidence rates spiked in certain years of our record:\u0026nbsp;2017\u0026nbsp;(the third year of the study) and especially\u0026nbsp;2024\u0026nbsp;(the final year), each of which showed markedly higher annual incidence rates than other years (Figure 4a).\u003c/p\u003e\n\u003cp\u003eMarked differences in ciguatera risk were observed between the three area councils of Ambae (Table 2). West Ambae consistently had the highest incidence, with a mean annual incidence of 937 cases per 100,000 inhabitants over the ten years. In comparison, the North Ambae council had an average annual incidence of 474 per 100,000, and East Ambae had the lowest at 405 per 100,000. A similar ranking was seen in the mean monthly incidence rates: West Ambae averaged 765 cases per 100,000 per month, significantly higher than North Ambae (380) and East Ambae (333). These figures highlight that West Ambae faces an exceptionally high rate of ciguatera cases. Looking across the calendar year, the months of April, October, and November (Figure 4b) had the highest ciguatera incidence rates on Ambae; in most other months, incidence remained comparatively low (often below 50 cases per 100,000) during the study period. This seasonal pattern aligns with the admission data, underlining that late and beginning of wet season are peak times for CFP occurrences on the island.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026ldquo;[Insert Figure 4 here]\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo integrative support the health facilities data and practices, we gathered information on ciguatera symptoms and treatment options from community members through an interview survey. A total of\u0026nbsp;97 residents\u0026nbsp;(49 men and 48 women) were interviewed across the West, North, and East area councils during fieldwork in October 2023 and June 2025. Over half (approximately\u0026nbsp;55%) of these participants were over 50 years old (Figure 5b), and nearly all (over 90%) had lived in their community for more than 20 years (Figure 5c). All respondents were familiar with fish as a food source, though there were some gender differences in fish consumption. According to the survey, men reported eating fish more frequently (usually weekly), whereas women were more likely to eat it only monthly or a few times per year. In fact, every man interviewed had regular access to fish in his diet, whereas a handful of women either lacked access to fish or chose not to consume it for various reasons (Figure 5d).\u003c/p\u003e\n\u003cp\u003eBased on the community survey, most participants interviewed had first-hand experience with ciguatera. In total, 82 out of 97 participants (approximately 85%) reported that they had suffered symptoms of ciguatera fish poisoning at least once in their lifetime and had used local remedies to treat these symptoms (Figure 5a). \u0026nbsp;This affected group included 46 of the 49 men and 36 of the 48 women surveyed, meaning roughly 94% of the interviewed men and 75% of the interviewed women had experienced CFP (Figure 6b). \u0026nbsp;Out of this figures, 58% (48) of the cases are reported from the North Area Council. The most commonly described symptoms were joint pain (especially in the elbows and knees, reported by 50 individuals) and muscle pain or weakness (47 individuals). Many participants also experienced intense itching or a prickling \u0026ldquo;needle-like\u0026rdquo; sensation in the skin (noted by 40 people), diarrhea (39 people), an abnormal cold sensation (37 people), and numbness or tingling around the mouth or nose (31 people) (Figure 6a). Several respondents additionally mentioned gastrointestinal symptoms such as vomiting, stomach pain, and even toothaches as part of their illness experience. Taken together, these accounts provide a detailed picture of the multi-system effects of ciguatera intoxication in the community.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCommunity Responses and Remedies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOur results showed that 85% of the people interviewed in the three area councils rely on local remedies as their first line of defences against CFP symptoms. These results suggest that many cases of ciguatera are not recorded in official clinic records, as affected individuals often treat themselves at home rather than seeking formal medical care. Indeed, many people reported preferring local (traditional) remedies for initial symptom relief\u0026nbsp;when they suspected that the fish they had eaten was ciguatoxic. One interviewee from West Ambae noted that fish poisoning incidents\u0026nbsp;have increased significantly in their area since residents returned after the 2017\u0026ndash;2018 evacuation\u0026nbsp;(following a volcanic eruption). However, few of these recent cases were reported to health facilities, as community members generally rely on customary treatments. Participants explained that most villagers use\u0026nbsp;leaves, tree barks, and other plant-based preparations\u0026nbsp;to address the early signs of ciguatera, only turning to clinics or hospitals if symptoms worsen (Figure 6c). Both men and women appeared equally likely to have experienced ciguatera at least once or twice in their lives, underscoring that CFP affects a broad cross-section of the community. The heavy reliance on home remedies also reflects a strong local knowledge of ciguatera management outside of the formal healthcare system.\u003c/p\u003e\n\u003cp\u003eBased on the quantitative data, ciguatera cases remain underreported in health facilities on Ambae, particularly in the three area councils. Survey data show that 85% of the adult population has experienced CFP with no clinical records. This represents a substantial cumulative disease burden, amounting to thousands of cases over time. For example, in a community of 10,000 adults, approximately 8,500 individuals would have been affected, far exceeding the few hundred documented in clinical records. This disparity demonstrates that clinic-based surveillance captures only a small fraction of the total number of cases- the \u0026ldquo;tip of the iceberg\u0026rdquo;. Many affected individuals may not seek medical care due to mild or self-limiting symptoms, reliance on traditional remedies, or limited access to health services. These findings highlight the importance of integrating community-based surveys and population-level data to obtain a more accurate understanding of CFP patterns for effective public health interventions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026ldquo;[Insert Figure 5 here]\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026ldquo;[Insert Figure 6 here]\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA diverse range of traditional remedies for ciguatera fish poisoning was documented on Ambae Island. During our field study, we identified\u0026nbsp;23 different plants\u0026nbsp;that locals use to alleviate symptoms of ciguatera. Various parts of these plants are utilized \u0026ndash; including leaves, young shoots, inner tree bark, and even fruits \u0026ndash; depending on the species and the symptom being treated. Both men and women in the community are actively involved in preparing and administering these remedies as a first response to suspected CFP cases.\u0026nbsp;Table 3\u0026nbsp;provides a detailed list of all recorded remedies, noting each plant\u0026rsquo;s scientific and local name, the parts used and preparation methods, and the specific ciguatera symptoms that each remedy is believed to relieve. For example, one commonly used treatment involves extracting the juice from crushed\u0026nbsp;tropical white weed\u0026nbsp;leaves (\u003cem\u003eAgeratum conyzoides\u003c/em\u003e) and drinking it to help relieve joint pain and muscle fatigue. This and other such practices highlight the extensive ethnobotanical knowledge present on Ambae for dealing with toxin-related fish illnesses.\u003c/p\u003e\n\u003cp\u003eSeveral of the identified remedies were particularly common and frequently mentioned by participants. The most widely cited treatment was\u0026nbsp;papaya\u0026nbsp;(\u003cem\u003eCarica papaya\u003c/em\u003e):\u0026nbsp;11 individuals\u0026nbsp;reported using papaya leaves, fruits, or roots to help relieve muscle pain and restore strength during recovery from ciguatera. Another popular remedy is the\u0026nbsp;seashore lily (\u003cem\u003eCrinum asiaticum\u003c/em\u003e); its leaves or roots are typically boiled and the decoction consumed, and\u0026nbsp;eight participants\u0026nbsp;used this method to alleviate general body pain and weakness. The\u0026nbsp;glue berry\u0026nbsp;tree (\u003cem\u003eCordia dichotoma\u003c/em\u003e) was cited by\u0026nbsp;6 participants, who use its leaves and inner bark to ease joint pain and improve strength. The inner bark of the\u0026nbsp;Tiger\u0026rsquo;s Claw\u0026nbsp;tree (\u003cem\u003eErythrina variegata\u003c/em\u003e) and\u0026nbsp;coconut milk\u0026nbsp;were each used by\u0026nbsp;5 participants\u0026nbsp;as treatments to reduce muscle pain, stop diarrhea and vomiting, and boost energy during CFP bouts. The milky sap from broken\u0026nbsp;frangipani\u0026nbsp;(\u003cem\u003ePlumeria\u003c/em\u003e) leaves was reportedly used by four people, who described collecting it and drinking it to reduce muscle pain, increase strength, and ease gastrointestinal symptoms.\u0026nbsp;These remedies were the first-line treatment for 85% of affected individuals, often administered repeatedly, with formal care sought only if symptoms worsened.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn addition to these major treatments, a handful of other plants were mentioned by only a few respondents. For instance,\u0026nbsp;wild yam\u0026nbsp;(\u003cem\u003eDioscorea villosa\u003c/em\u003e),\u0026nbsp;cut nut\u0026nbsp;(\u003cem\u003eBarringtonia edulis\u003c/em\u003e), and\u0026nbsp;golden apple\u0026nbsp;(\u003cem\u003eSpondias dulcis\u003c/em\u003e) were each cited by three participants as helpful in relieving ciguatera symptoms. Most of the remaining remedies in our survey (such as certain herbs and bush medicines not detailed above) were mentioned by just one or two individuals. This suggests that knowledge of some of these more obscure treatments may be limited to certain families or villages. Overall, however, local remedies clearly represent an essential first line of defense against ciguatera on Ambae. The community\u0026rsquo;s extensive use of plant-based treatments complements the care provided by health facilities, and it highlights the value of indigenous knowledge in managing and recovering from CFP in Vanuatu\u0026rsquo;s rural islands. Engagement with traditional healers could be a novel strategy for syndromic surveillance, as they are often the first to see cases of CFP before referring to the health facilities.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTABLE 3. Local Remedies used by local people on Ambae to treat symptoms of Ciguatera Fish Poisoning\u0026nbsp;\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eOur findings indicate clear seasonality in ciguatera fish poisoning (CFP) incidences in Vanuatu, with higher case counts observed in April, May, October, and November between 2015 and 2024. This pattern mirrors trends reported in French Polynesia, where peak densities of \u003cem\u003eGambierdiscus\u003c/em\u003e were observed in January, April, and October from 1993 to 1997 (Chinain et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Similarly, in Japan, \u003cem\u003eGambierdiscus\u003c/em\u003e densities increase during summer (June-August) and autumn (September-November), coinciding with higher sea surface temperatures and more CFP cases (Nishimura et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Two key climatic factors likely contribute to the proliferation of \u003cem\u003eGambierdiscus\u003c/em\u003e during these months-warmer sea surface temperatures and coral reef disturbances caused by tropical cyclones. Damaged coral promotes algal growth, which attracts herbivorous fish that can subsequently accumulate ciguatoxins (Berdalet et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). In Vanuatu, the wet and cyclone season runs from November to April, corresponding to the local summer when sea surface temperatures are elevated, similar to Japan\u0026rsquo;s summer (June-August). Moreover, rainfall and runoff during these periods deliver nutrients and sediments that further enhance dinoflagellate growth (Comeros-Raynal et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Fabricius et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Public health authorities, local governments, and government agencies responsible for weather and climate forecasts should develop targeted public health messaging for months that record the highest CFP case counts. This includes integration of CFP awareness into climate adaptation and disaster response plans.\u003c/p\u003e\u003cp\u003eVolcanic eruptions also appear to influence CFP dynamics. The 2017\u0026ndash;2018 eruptions (Moussallam et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003eb) may explain the peak in CFP cases observed in 2017. Volcanic activity can induce harmful algal blooms by releasing sulfur and iron into seawater, enriching nutrient levels (Kim, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In the Northern Mariana Islands, volcanic ash has been shown to introduce diverse chemical compounds that alter benthic community composition, promoting dinoflagellate proliferation (Schils, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Another notable CFP increase in 2014 is likely related to the strong 2023 El Ni\u0026ntilde;o event (Hu et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Climate phenomena such as El Ni\u0026ntilde;o raise sea surface temperatures, expanding the distribution of toxic dinoflagellates and increasing the level of ciguatoxins in fish (Kibler et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Zheng et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Volcanic activity and elevated surface temperatures contribute indirectly to increased CFP incidences. Volcanic eruptions trigger post-disaster health alerts about increased CFP risk. Strengthening information-sharing mechanisms among agencies and communities is therefore essential for mitigating future outbreaks.\u003c/p\u003e\u003cp\u003eThe distribution of CFP cases across the three area councils reflects both population distribution and healthcare-seeking behaviour. A high reliance on local remedies for CFP symptom management suggests significant underreporting of cases, consistent with findings from Florida, United States of America, where incidence rates require adjustment for underreporting (Radke et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Geographically, higher cases of CFP in the West and North Area Council compared to the East may be attributed to their proximity to the volcano (Fig.\u0026nbsp;1), and numerous creeks facilitate nutrient and sediment transport, and greater exposure to volcanic ash due to prevailing east and southeast winds (Loughlin et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Tepe \u0026amp; Bau, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Additionally, a mudflow in Walubue (North Area Council) in 2017 (Roy \u0026amp; Jong, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and a volcanic sediment flow in Lone (West Area Council) in early 2018 further disturbed the marine ecosystem, likely contributing to CFP cases. Both human behaviour and natural hazards may contribute to the number of cases of ciguatera. This required the health authorities and the local government to increase awareness of the reporting of ciguatera cases across the island.\u003c/p\u003e\u003cp\u003eOverall, CFP incidence in Vanuatu has risen steadily from 1970 to 2024. During this period, Penama Province \u0026ndash; where our study site is located \u0026ndash; recorded the highest rate among all six provinces (699 cases per 100,000). This aligns with observations from French Polynesia, where peaks in \u003cem\u003eGambierdiscus\u003c/em\u003e density during 1993\u0026ndash;1996 corresponded with elevated CFP cases (Chinain et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1999\u003c/span\u003e), and with high CFP activity in the United States from 2001\u0026ndash;2011 (Gingold et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). These patterns suggest that climate change and improved surveillance by the Vanuatu Ministry of Health have both contributed to the observed increase in CFP reporting.\u003c/p\u003e\u003cp\u003eCommunity-based surveys of individuals affected by CFP and the local remedies they used to treat symptoms may complement clinical CFP data to help reduce underreporting by health facilities. Community-based data are easier to access and more geographically representative of the overall population (Gutilla et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Furthermore, integrating clinical and survey data helps identify, monitor, and improve the range of medical, environmental, and social factors relevant to community health activities, and to gather in-depth, context-rich information about each case (Gamache et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Matheson et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). This shows that qualitative data often enhanced alternative theoretical framework and measures alongside quantitative data (Muntaner \u0026amp; G\u0026oacute;mez, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Local remedies have been used for generations by communities, providing an option for public health intervention in cases where government health services are limited. A need for effective strategies to create platforms for greater dialogue between health authorities and indigenous knowledge practitioners of local medicines.\u003c/p\u003e\u003cp\u003eNo significant gender difference was detected in CFP incidents, despite men generally having greater access to fish. This is consistent with studies showing no significant difference in fish consumption between males and females in Vanuatu (Frackiewicz et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Approximately 72% of rural households engage in fishing primarily for protein, while 39% depend on fisheries for income (Charlton et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This high reliance on marine resources across genders likely explains the widespread risk of CFP (Chinain et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Gillett, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). To mitigate this risk, collaborative communication and early-warning frameworks, such as the Gigila Framework (Rarai et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003ec), should be promoted to enhance community awareness of CFP outbreaks.\u003c/p\u003e\u003cp\u003eLocal remedies remain a critical first-line response to CFP symptoms in remote and rural Vanuatu communities with limited access to healthcare. Many traditional treatments have demonstrated inhibitory activity against ciguatoxic effects (Bourdy et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1992\u003c/span\u003eb; Kumar-Roin\u0026eacute; et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). For example, the golden apple (\u003cem\u003eSpondias dulcis\u003c/em\u003e) leaves and bark are used in New Caledonia, while coconut juice and flesh are traditional treatments in Fiji (Lako et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003eb). Similarly, most respondents in our study reported using local remedies to alleviate CFP symptoms, highlighting their cultural and practical significance in community-based health responses. Collaborating with Indigenous knowledge holders could improve surveillance of ciguatera as they might notice environmental precursors to outbreaks (Rarai et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003ed), or that recognizing traditional remedies could inform healthcare delivery by prompting formal testing of a popular herbal remedy for efficacy/safety.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eOur findings underscore the need for integrated surveillance that incorporates community-level data and traditional knowledge to better gauge the true burden of CFP in Vanuatu. Our recommendations are to enhance surveillance through integrated reporting that captures cases from both health clinics and community-based reporting mechanisms, and to develop targeted public health awareness and campaigns before and during high\u0026ndash;risk seasons (April-May, October to November). Furthermore, issue post-disaster warnings by issuing specific CFP warnings following volcanic activity, cyclones, and strong El Ni\u0026ntilde;o events. Collaborative research among scientists, local knowledge holders, and government agencies is essential to advance understanding of ciguatoxins. Further Pharmacological studies on the most cited traditional remedies (e.g., \u003cem\u003eCarica papaya\u003c/em\u003e, \u003cem\u003eCrinum asiaticum\u003c/em\u003e) to explore potential supportive treatments. Strengthening scientific capacity in these fields will enhance the recognition, confirmation, and treatment of ciguatera poisoning, while also improving seafood safety and understanding of environmental factors that lead to CFP.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAsmundis, R. de. (2021). \u003cem\u003eLabVIEW: A Flexible Environment for Modeling and Daily Laboratory Use\u003c/em\u003e. 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Ability of certain plant extracts traditionally used to treat ciguatera fish poisoning to inhibit nitric oxide production in RAW 264.7 macrophages. \u003cem\u003eJournal of Ethnopharmacology\u003c/em\u003e, \u003cem\u003e123\u003c/em\u003e(3), 369\u0026ndash;377. https://doi.org/10.1016/j.jep.2009.03.039\u003c/li\u003e\n \u003cli\u003eKumar‐Roin\u0026eacute;, S., Taiana Darius, H., Matsui, M., Fabre, N., Haddad, M., Chinain, M., Pauillac, S., \u0026amp; Laurent, D. (2011). A Review of Traditional Remedies of Ciguatera Fish Poisoning in the Pacific. \u003cem\u003ePhytotherapy Research\u003c/em\u003e, \u003cem\u003e25\u003c/em\u003e(7), 947\u0026ndash;958. https://doi.org/10.1002/ptr.3396\u003c/li\u003e\n \u003cli\u003eLako, J. V., Naisilisili, S., Vuki, V. C., Kuridrani, N., \u0026amp; Agyei, D. (2023). Local and Traditional Ecological Knowledge of Fish Poisoning in Fiji. \u003cem\u003eToxins\u003c/em\u003e, \u003cem\u003e15\u003c/em\u003e(3), Article 3. https://doi.org/10.3390/toxins15030223\u003c/li\u003e\n \u003cli\u003eLoughlin, S. C., Sparks, R. S. J., Brown, S. K., Jenkins, S. F., \u0026amp; Vye-Brown, C. (2015). \u003cem\u003eGlobal Volcanic Hazards and Risk\u003c/em\u003e. Cambridge University Press.\u003c/li\u003e\n \u003cli\u003eMatheson, A., Walton, M., Gray, R., Lindberg, K., Shanthakumar, M., Fyfe, C., Wehipeihana, N., \u0026amp; Borman, B. (2018). Evaluating a community-based public health intervention using a complex systems approach. \u003cem\u003eJournal of Public Health\u003c/em\u003e, \u003cem\u003e40\u003c/em\u003e(3), 606\u0026ndash;613. https://doi.org/10.1093/pubmed/fdx117\u003c/li\u003e\n \u003cli\u003eMoussallam, Y., Rose-Koga, E. F., Koga, K. T., M\u0026eacute;dard, E., Bani, P., Devidal, J.-L., \u0026amp; Tari, D. (2019). Fast ascent rate during the 2017\u0026ndash;2018 Plinian eruption of Ambae (Aoba) volcano: A petrological investigation. \u003cem\u003eContributions to Mineralogy and Petrology\u003c/em\u003e, \u003cem\u003e174\u003c/em\u003e(11), 90. https://doi.org/10.1007/s00410-019-1625-z\u003c/li\u003e\n \u003cli\u003eMuntaner, C., \u0026amp; G\u0026oacute;mez, M. (2003). Qualitative and quantitative research in social epidemiology: Is complementarity the only issue? \u003cem\u003eGaceta Sanitaria\u003c/em\u003e, \u003cem\u003e17\u003c/em\u003e(Supl.3), 53\u0026ndash;57. https://doi.org/10.1157/13057792\u003c/li\u003e\n \u003cli\u003eNishimura, T., Tawong, W., Sakanari, H., Ikegami, T., Uehara, K., Inokuchi, D., Nakamura, M., Yoshioka, T., Abe, S., Yamaguchi, H., \u0026amp; Adachi, M. (2018). Abundance and seasonal population dynamics of the potentially ciguatera-causing dinoflagellate Gambierdiscus in Japanese coastal areas between 2007 and 2013. \u003cem\u003ePlankton and Benthos Research\u003c/em\u003e, \u003cem\u003e13\u003c/em\u003e(2), 46\u0026ndash;58. https://doi.org/10.3800/pbr.13.46\u003c/li\u003e\n \u003cli\u003eRadke, E. G., Reich, A., \u0026amp; Morris, J. G. (2015). Epidemiology of Ciguatera in Florida. \u003cem\u003eThe American Journal of Tropical Medicine and Hygiene\u003c/em\u003e, \u003cem\u003e93\u003c/em\u003e(2), 425\u0026ndash;432. https://doi.org/10.4269/ajtmh.14-0400\u003c/li\u003e\n \u003cli\u003eRarai, A., Weber, E., Ruben, J., \u0026amp; Parsons, M. (2024). Indigenous knowledge with science forms an early warning system for ciguatera fish poisoning outbreak in Vanuatu. \u003cem\u003eCommunications Earth \u0026amp; Environment\u003c/em\u003e, \u003cem\u003e5\u003c/em\u003e(1), 1\u0026ndash;11. https://doi.org/10.1038/s43247-024-01931-5\u003c/li\u003e\n \u003cli\u003eRoy, E. A., \u0026amp; Jong, E. de. (2018, April 25). Vanuatu: Landslide and flash flood hampers relief effort on Ambae. \u003cem\u003eThe Guardian\u003c/em\u003e. https://www.theguardian.com/world/2018/apr/25/vanuatu-landslide-and-flash-flood-hampers-relief-effort-on-ambae\u003c/li\u003e\n \u003cli\u003eSchils, T. (2012). Episodic Eruptions of Volcanic Ash Trigger a Reversible Cascade of Nuisance Species Outbreaks in Pristine Coral Habitats. \u003cem\u003ePLOS ONE\u003c/em\u003e, \u003cem\u003e7\u003c/em\u003e(10), e46639. https://doi.org/10.1371/journal.pone.0046639\u003c/li\u003e\n \u003cli\u003eSkinner, M. P., Brewer, T. D., Johnstone, R., Fleming, L. E., \u0026amp; Lewis, R. J. (2011). Ciguatera Fish Poisoning in the Pacific Islands (1998 to 2008). \u003cem\u003ePLOS Neglected Tropical Diseases\u003c/em\u003e, \u003cem\u003e5\u003c/em\u003e(12), e1416. https://doi.org/10.1371/journal.pntd.0001416\u003c/li\u003e\n \u003cli\u003eTepe, N., \u0026amp; Bau, M. (2014). Importance of nanoparticles and colloids from volcanic ash for riverine transport of trace elements to the ocean: Evidence from glacial-fed rivers after the 2010 eruption of Eyjafjallaj\u0026ouml;kull Volcano, Iceland. \u003cem\u003eScience of The Total Environment\u003c/em\u003e, \u003cem\u003e488\u0026ndash;489\u003c/em\u003e, 243\u0026ndash;251. https://doi.org/10.1016/j.scitotenv.2014.04.083\u003c/li\u003e\n \u003cli\u003eVSNO (2020) . \u003cem\u003eCensus Reports\u003c/em\u003e. Vanuatu Bureau of Statistics. https://vbos.gov.vu/index.php/en/census-and-surveys/census-report. Accessed online 18 October 2025.\u003c/li\u003e\n \u003cli\u003eZheng, L., Gatti, C. M. iti, Garrido Gamarro, E., Suzuki, A., \u0026amp; Teah, H. Y. (2020). Modeling the time-lag effect of sea surface temperatures on ciguatera poisoning in the South Pacific: Implications for surveillance and response. \u003cem\u003eToxicon\u003c/em\u003e, \u003cem\u003e182\u003c/em\u003e, 21\u0026ndash;29. https://doi.org/10.1016/j.toxicon.2020.05.001\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 3 are available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[{"identity":"9ec06fe0-21c3-413b-bfcb-95aa2d3cea3a","identifier":"10.13039/501100000531","name":"Association of Commonwealth Universities","awardNumber":"9574","order_by":0}],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Association of Commonwealth Universities","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ciguatera Fish Poisoning, Trends, Epidemiology, and Indigenous Healing Practices, Health Risk ","lastPublishedDoi":"10.21203/rs.3.rs-8250358/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8250358/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCiguatera Fish Poisoning (CFP) is a pervasive seafood-borne illness across the Pacific, yet surveillance is challenging and data are sparse. This study explores how combining biomedical (clinical data) and indigenous (community survey data) approaches can enhance ciguatera management on Ambae Island, Vanuatu. We employed a mixed-methods approach that included reviewing health facility records and conducting community surveys. We collected data from the island's three area councils (East, North, and West) and from seven health facilities serving these regions. Results show that between 2015 and 2024, CFP cases peaked in April, May, October, and November, with the highest annual cases in 2017 and 2024. Nduindui and Walaha Health Centres in the West Ambae reported the most CFP cases, followed by the Lolopuepue Health Centre in North Ambae. The West Ambae Area Council had the highest incidence rates (approximately 937 per 100,000 people per month and 765 per 100,000 people per year) compared to lower rates in the North and East Area Councils. Our community survey shows that out of the 97 people interviewed, 85% have experience symptoms of ciguatera and 23 local plants have been used to treat CFP symptoms. To deepened understanding of ciguatera (both in Vanuatu and throughout the Pacific), further on other islands in Vanuatu and the Pacific is recommended to compare incidence rates and improve CFP across the region.\u003c/p\u003e","manuscriptTitle":"Ciguatera on Ambae Island, Vanuatu: Trends, Epidemiology, and Indigenous Healing Practices (2015–2024)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-03 11:47:22","doi":"10.21203/rs.3.rs-8250358/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5eeb5c05-3ae0-4e96-9f6b-c3f169b8a8e8","owner":[],"postedDate":"December 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":58914007,"name":"Epidemiology"},{"id":58914008,"name":"Tropical Medicine"}],"tags":[],"updatedAt":"2025-12-03T11:47:22+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-03 11:47:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8250358","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8250358","identity":"rs-8250358","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}