Anticoagulant rodenticide toxicosis in nutria (Myocastor coypus) in Thailand

Anticoagulant rodenticide toxicosis in nutria (Myocastor coypus) in Thailand | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Anticoagulant rodenticide toxicosis in nutria (Myocastor coypus) in Thailand Piyarat Chansiripornchai, Supawit Weeramontharop, Somporn Techangamsuwan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7336734/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Nov, 2025 Read the published version in Veterinary Research Communications → Version 1 posted 11 You are reading this latest preprint version Abstract Nutria ( Myocastor coypus ) is a large, herbivorous rodent found in Africa, Europe, North America, and Asia. Anticoagulant rodenticide (AR) toxicosis was diagnosed in nutrias based on history taking, clinical signs and chemical analysis, marking the first confirmed case in this species in Thailand. Six out of the eight nutrias in the same herd died, showing initial clinical signs such as abnormal bleeding and abortion in pregnant individuals. The carcasses of the dead nutrias were analysed for exposure to rodenticides and insecticides. Screening tests on liver specimens, using thin-layer chromatography and spectrophotometry, confirmed the presence of AR. In contrast, the two survival nutrias were clinically observed and remained healthy during an 18-month follow-up period. To date, there have been no reports of nutrias with diagnosed AR poisoning. This case likely resulted from rodenticide contamination in agricultural settings, underscoring the importance of proper rodenticide management to protect nontarget species and prevent environment contamination. contamination Myocastor coypus nutria poisoning rodenticide toxicosis Figures Figure 1 Figure 2 Background The nutria, or coypu ( Myocastor coypus ), is a large, semiaquatic herbivorous rodent originally native to South America but now found in Africa, Europe, North America, and Asia (Carter and Leonard 2002 ; Pedruzzi et al. 2022 ). Nutrias are mammals belonging to the order Rodentia and the family Myocastoridae (Wood et al. 1992). They have a robust, highly arched body covered in fur that varies in color from light brown to reddish, or from greyish dark brown to black. Nutrias have short legs and a long, rounded tail (Fig. 1 a). Their head is large and nearly triangular, with small ears and long vibrissae (Wood et al. 1992). Adult nutrias typically weigh between 5 and 10 kg and have an external body length ranging from approximately 472 to 575 mm (Wood et al. 1992; Guichon et al. 2003 ). They are well adapted to aquatic ecosystems and are known to consume large quantities of aquatic plants. In the past, the nutria was widely recognized as one of the most invasive alien mammals globally, with significant impacts on natural ecosystems, agricultural crops and, potentially human health (Pedruzzi et al. 2022 ). By the early 1800s, the nutria pelt trade had become a major industry in South America, with pelts and furs exported to Europe for use in fashion accessories such as hats and collars (Saadoun and Cabrera 2019 ). However, when the nutria fur market collapsed in the 1940s and again between 1990 and 2000, many ranchers, unable to afford the costs of feeding and housing the animals, released thousands of nutrias into the wild. Combined with accidental escapes from farms over time, these events likely contributed to the invasive spread of nutrias in regions where they were originally introduced by the pelt and fur industry (Saadoun and Cabrera 2019 ). Countries affected include the USA, Russia, Poland, France, and Spain, as well as Japan, Korea, and Iran (Farashi and Najafabadi 2015 ; Hong et al. 2015 ). Today, nutrias are primarily farmed through selectively bred animals known as “nutria mutations”, which have been developed through breeding programs in many countries, particularly in Poland (Saadoun and Cabrera 2019 ). In addition to the standard fur color, nutria mutations exhibit a variety of fur colors, including black, blue, albino, yellow, silver, and multicolored varieties (Tumova et al. 2015 ). In Thailand, nutrias were imported from China and Taiwan in the 1990s for their fur and meat, and were also used in hunting, which led to the establishment of wild populations a few years later (Carter and Leonard 2002 ; Pedruzzi et al. 2022 ). These nutrias began to live freely in agricultural areas, where their populations were controlled through the use of rodenticides and hunting. Today, selectively bred nutria mutations are introduced as exotic pets in Thailand, and a few nutria farms are located in the central region of Thailand. In general, nutria mutations are healthy and relatively easy to raise. They are housed on farms and fed with rabbit food, guinea pig food, grass, hay, fruits, and vegetables. However, nutrias display natural behaviors such as curiousity-driven exploration, burrowing, and digging (Kang et al. 2022 ), which may expose them to toxic substances present in the soil or surrounding environment, including rodenticides and insecticides. Recent studies have highlighted the environmental contamination caused by anticoagulant rodenticides (ARs), which can result in morbidity or mortality in nontarget animal species (Chansiripornchai et al. 2024 ; Chansiripornchai et al. 2025 ; Nakayama et al. 2019 ). ARs have been widely used worldwide since the mid-20th century to control rodent populations in urban settings, agricultural environments, and habitat conservation areas (Vicedo et al. 2024). ARs are classified into first-generation compounds, such as warfarin and diphacinone, and second-generation compounds, such as brodifacoum, difenacoum and bromadiolone (Hovda et al. 2024 ). Second-generation ARs are persistent, bioaccumulative, and highly toxic compounds, and they are currently the most widely used products for rodent control (Vicedo et al. 2024 ; Watt et al. 2005 ). Both generations of ARs disrupt vitamin K-dependent clotting factor synthesis in the liver, potentially leading to life-threatening coagulopathy (Hovda et al. 2024 ). Although ARs are intended for use against rodents, toxicosis in nontarget species−either through accidental or intentional exposure−is a growing global concern (Caloni et al. 2016 ). Between 1998 and 2015, 30 studies reported primary or secondary exposure to, and poisoning by, ARs in nontarget animals (Nakayama et al. 2019 ). Data from animal poison control centers indicate that rodenticides are among the top toxins to which pets are exposed, accounting for 3.8% of reported cases in Europe and 7% in the USA (ASPCA 2024; VPIS 2022). Exposure to ARs can occur through primary routes, such as the direct ingestion of toxic baits, or through secondary routes, including the consumption of contaminated materials or prey animals previously exposed to the compounds (Nakayama et al. 2019 ; Vicedo et al. 2024 ). Given the significant risks associated with AR exposure, it is crucial to study and document cases of AR toxicosis to improve our understanding of their impact on various animal species and to inform appropriate mitigation strategies. This report describes a fatal case of toxicosis in nutria, likely caused by AR exposure due to environmental contamination, marking the first documented case in Thailand. The findings are particularly significant given the widespread use of ARs in both agricultural and urban environments. The diagnosis is supported by through clinical observations, chemical analyses, and pathological examinations, which collectively strengthen the conclusion of AR-induced toxicosis. Case presentation Case history A 15-month-old female nutria, raised on a farm in central Thailand, was found dead and submitted for routine necropsy at the Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Thailand. A liver specimen was subsequently sent to the Department of Veterinary Pharmacology (DVPCU) for analysis of AR exposure. Since 1990, the DVPCU has served as one of Thailand’s toxicological centers, providing toxicant analysis such as rodenticides, insecticides, herbicides, and mycotoxins for animal hospitals, veterinarians, general practitioners, and the general public. According to the provided history, the farm housed seven female and one male nutria. All eight nutrias were housed in both indoor and outdoor enclosures. In January 2024, six of the female nutrias died within 1–2 days following the onset of clinical signs. The owner reported that prior to the incident, all nutrias appeared healthy, exhibiting normal eating, drinking, and behavioral patterns. Their diet consisted of commercial rabbit or guinea pig food, grass, hay, and fresh fruits and vegetables. Additionally, recognizing the species’ natural tendency to dig and burrow, the owner had provided access to an outdoor area with a soil-based ground surface to support this behavior. However, several days prior to the onset of clinical signs, six of the nutrias were exposed to newly purchased soil and mud from a commercial supplier. These six individuals actively engaged in digging and burrowing within the new soil, whereas the remaining two nutrias−housed separately−had no contact with it. The owner initially observed symptoms including anorexia, followed by ataxia, seizures, abnormal bleeding, abortion, and death within 1–2 days (Fig. 1 b-e). Notably, the two nutrias that were not exposed to the new soil remained healthy and exhibited no clinical signs. Sample analysis for AR screening For the chemical investigation of ARs, the nutria liver specimen was analyzed using thin-layer chromatography (TLC) and derivative spectrophotometry, as previously described by Kaewamatawong et al. ( 2011 ). Briefly, the liver specimen was homogenized and extracted with chloroform under vaporous conditions. The extract was filtered, and the remaining residue was re-extracted and re-filtered. The final residue was then reconstituted in 1 ml of chloroform. TLC separation was performed using silica gel G plates (Merck, USA) as the stationary phase and a mobile phase consisting of a methyl ethyl ketone and benzene mixture (6:120, v/v). Standard solutions and control extracts from animal samples were prepared. Quantification was achieved by spiking the test sample extracts with AR standards−namely warfarin, coumatetralyl, difenacoum, and bromadiolone (Sigma-Aldrich, USA)−and analyzing them according to the standard TLC protocol. For spot detection, TCL plates were oversprayed sequentially with hydrogen peroxide and ferric chloride solutions. A sample was considered AR-positive when both TLC and spectrophotometric analyses yielded positive results. Clinical findings Gross pathological examination of the dead nutrias revealed moderate autolysis, with a body condition score of 3 out of 5. There were no remarkable lesions on the external appearance, except for subcutaneous hemorrhage in the caudal region (Fig. 1 b). The lungs showed approximately 60–70% diffuse redness with scattered firm areas and regions of pale emphysema. The uterus revealed dark red to brown discoloration with marked congestion of the uterine blood vessels. A single mummified fetus was evident at the cervical opening (Fig. 1 c-d). The right uterine horn was enlarged and contained several fetal sac-like structures attached to the endometrial lining. No significant gross lesions were observed in the liver, kidneys, spleen, or gastrointestinal tract. Chemical analysis of the liver specimen confirmed AR intoxication. TLC and derivative spectrophotometry identified AR compounds by matching the sample’s peak points with those of known AR standards (Fig. 2 a-e). Although no obvious hemorrhagic lesions were observed in the liver during gross examination (Fig. 1 e), AR exposure was clearly confirmed through the positive results obtained from both TLC and spectrophotometric analyses. Discussion The nutria ( Myocastor coypus ), a prolific herbivorous rodent native to South America, is farmed in many countries primarily for its pelt, using selectively bred individuals known as nutria mutations. Its meat is often considered a by-product of the fur industry (Saadoun and Cabrera 2019 ). In Thailand, nutrias are kept primarily as exotic pets and zoo animals. As their presence in captivity increases, understanding the health concerns and disease profiles of nutrias become essential for effective husbandry, veterinary care and long-term population management. ARs are widely used to control rodent populations in both urban and agricultural environments. While these compounds are effective in reducing health risks to humans and mitigating economic losses, their widespread application has led to unintended and sometimes severe consequences for nontarget species across multiple countries (Chansiripornchai et al. 2025 ; Lohr 2018 ; Nakayama et al. 2019 ). Despite the growing presence of nutrias in various regions, there is limited literature on their health status, particularly regarding non-infectious diseases. Notably, rodenticide-induced toxicosis in nutria has not been previously reported. In this case, AR intoxication was identified in the liver specimen of a nutria. Chemical analysis using TLC and spectrophotometry confirmed the presence of ARs. Although advanced analytical techniques such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) are often preferred for the precise identification and quantification of ARs, TLC and spectrophotometry provide reliable, accessible alternatives for screening (Chansiripornchai et al. 2024 ; Kaewamatawong et al. 2011 ). Given that ARs do not occur naturally in mammalian tissues and that supporting clinical and environmental data suggest exposure, a qualitative diagnostic approach remains suitable for confirming AR intoxication (Gallocchio et al. 2014 ). Accordingly, our laboratory employs qualitative analysis via TLC and spectrophotometry to determine the presence of ARs in liver specimens. Both techniques are simple, cost-effective, and valuable tools for confirming AR intoxication, particularly in cases where ingestion was not witnessed. Therefore, a positive result indicates that the animal was exposed to some quantity of ARs, supporting a diagnosis of AR intoxication (Chansiripornchai et al. 2024 ; Chansiripornchai et al. 2025 ). The clinical signs observed in the affected nutria in this report, such as anorexia, lethargy, and ataxia, were consistent with the typical manifestations of AR intoxication. Notably, anorexia is often the first visible sign of AR poisoning in rodents (Chansiripornchai et al. 2024 ; Fisher et al. 2019 ). In addition, subcutaneous hemorrhage was observed in all deceased nutrias, aligning with gross pathological findings commonly associated with AR intoxication in mammals, including rodents (Chansiripornchai et al. 2024 ; Hovda et al. 2024 ). Although hemorrhagic lesions were not obviously seen in the liver specimen of the nutria examined, AR exposure was definitively confirmed through positive results from both TLC and spectrophotometry analyses. This highlights the importance of chemical diagnostics in detecting AR toxicosis, especially when classical lesions are not apparent during necropsy. During gross pathological inspection, the pathologists (SW and ST) identified fetal abortion in the nutria carcass. According to the owner’s report, all four pregnant nutrias experienced abortion accompanied by massive hemorrhage prior to death. This observation aligns with previous studies reporting that ARs can induce abortion in various mammalian species, including humans, dogs, and mares (Chetot et al. 2020 ; Fitzgerald et al. 2018 ; Zakian et al. 2019 ). Pregnancy represents a critical physiological period during which females, early embryos, and developing fetuses are particularly vulnerable to the toxic effects of anticoagulants. As such, ARs may result in adverse fetal outcomes, including spontaneous abortion, fetal death (fetotoxicity), or other forms of teratogenic effects through transplacental transfer (Chetot et al. 2020 ; Fitzgerald et al. 2018 ; Hovda et al. 2024 ). Following the incident, the surviving female and male nutrias were relocated to a different area of the farm and placed under close veterinary observation. During the 18-month follow-up period, both nutrias remained healthy, and the female nutria successfully gave birth to healthy offspring. The exact source of ARs detected in this case remains uncertain but is most likely attributable to environmental contamination. According to the history provided by the owners, all nutrias consumed the same feed; however, a new environmental variable was introduced−soil. The owners had recently purchased soil from a local supplier to develop a new farming area. This soil was reportedly obtained from post-harvest rice fields. All of the affected nutrias had direct contact with the newly introduced soil through digging and burrowing activities prior to developing clinical signs and dying. In contrast, the only surviving nutria had been housed separately and did not come into contact with this soil, and notably exhibited no clinical abnormalities. These observations strongly suggest that the newly acquired soil may have been the source of AR exposure. Pesticides, including rodenticides, are routinely used in agricultural settings to protect crops and control rodent pests. Although testing the suspected soil for AR residues was not possible due to its unavailability by the time of investigation, the circumstantial evidence supports the likelihood of soil-based contamination. Despite national efforts to promote organic farming practices in Thailand, many farmers continue to rely heavily on chemical pesticides, including rodenticides (Angsoongnern, 2015 ). These compounds are known to persist in the environment for extended periods, contributing to soil and water contamination through direct application or surface runoff. Consequently, rodenticides not only pose a threat to target pests but may also adversely affect nontarget animals, local ecosystems, and even human health (Angsoongnern, 2015 ; Chansiripornchai et al. 2025 ). These findings highlight the importance of judicious use of rodenticides to minimize risks and ensure the safety of humans, animals, and the environment. Our findings suggest that the use of ARs may unintentionally poison nontarget animals. Recent studies have highlighted that ARs can contribute to environmental contamination through residues, leading to mortality or morbidity in nontarget species. Additionally, the presence of these substances in the environment poses a significant risk to public health (Chansiripornchai et al. 2025 ; Nakayama et al. 2019 ; Vicedo et al. 2024 ). The results emphasize the urgent need for improved rodenticide regulation, environmental monitoring, and responsible pest management strategies to safeguard animal health, biodiversity, and public health. Conclusion This case represents the first reported diagnosis of AR poisoning in nutria, based on clinical history, observed clinical signs, and confirmation through chemical analysis using TLC and spectrophotometry. The findings suggest that environmental contamination, likely through AR residues in newly introduced soil, may have been a critical factor contributing to the mortality of the affected animals. This underscores the importance of responsible AR use and the need for greater awareness of its potential ecological impacts. Careful management and regulation of AR application are essential to prevent unintended harm to nontarget species, protect environmental health, and support sustainable farming practices. Declarations Acknowledgments The authors would like to thank the nutria owners for their kind cooperation during data collection. We also extend our thanks to Assistant Professor Simon Jeremy Peter Wright, Faculty of Arts, Chulalongkorn University, for his assistance with English language editing. Authors’ contributions PC contributed to the design, performed clinical studies, collected animal patient data, analyzed the data and prepared the manuscript. SW contributed to pathological investigation. ST contributed to pathological study and manuscript preparation. All authors have read and approved the final manuscript. Funding Not applicable. Data availability All data generated or analyzed during this study are included in this published article. Ethics approval and consent to participate Not applicable for specimens from the carcass. Consent for publication was obtained from the owners. Competing interests The authors declare no competing interests. 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Supplementary Files VetResCom.Nutria.additionalfile.docx Cite Share Download PDF Status: Published Journal Publication published 03 Nov, 2025 Read the published version in Veterinary Research Communications → Version 1 posted Editorial decision: Revision requested 24 Aug, 2025 Reviews received at journal 23 Aug, 2025 Reviews received at journal 23 Aug, 2025 Reviews received at journal 20 Aug, 2025 Reviewers agreed at journal 14 Aug, 2025 Reviewers agreed at journal 13 Aug, 2025 Reviewers agreed at journal 12 Aug, 2025 Reviewers invited by journal 12 Aug, 2025 Editor assigned by journal 12 Aug, 2025 Submission checks completed at journal 12 Aug, 2025 First submitted to journal 10 Aug, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7336734","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":501906367,"identity":"05bd040b-0259-4d06-a939-e4e03b608cf2","order_by":0,"name":"Piyarat Chansiripornchai","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIiWNgGAWjYFACxgYwxS8BpiRkiNYiITkDzJLgIdouCYMbEM2EtcjPbm6T+LnHrs74dvPxRzdqLHgY2A8f3YBPi8Gdg22SPc+SJczuHEtszjkGdBhPWtoNvFokEtskeA4wS5jdyDFszmEDapHgMcOrRX5GYpvknwP1EsYzQFr+EaGF4UZimzTPgcMSBhJALbltRGgB+qXZWubAcckZN9ISZ+f2SfCwEfKL/Oz2hzffHKjm55+RfOBzzrc6OX72w8fwO0yCgUUCRYANr3KIFuYPBBWNglEwCkbByAYAAb5Hki0h0iAAAAAASUVORK5CYII=","orcid":"","institution":"Chulalongkorn University","correspondingAuthor":true,"prefix":"","firstName":"Piyarat","middleName":"","lastName":"Chansiripornchai","suffix":""},{"id":501906368,"identity":"fe858498-7cd8-4733-8995-ea95ad94a4db","order_by":1,"name":"Supawit Weeramontharop","email":"","orcid":"","institution":"Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Supawit","middleName":"","lastName":"Weeramontharop","suffix":""},{"id":501906369,"identity":"8db09146-3f6b-4ff0-a472-ba1e6623075f","order_by":2,"name":"Somporn Techangamsuwan","email":"","orcid":"","institution":"Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Somporn","middleName":"","lastName":"Techangamsuwan","suffix":""}],"badges":[],"createdAt":"2025-08-10 04:23:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7336734/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7336734/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11259-025-10957-9","type":"published","date":"2025-11-03T15:56:50+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":89464377,"identity":"fdef2824-9154-4dac-a1eb-a05a7f75a877","added_by":"auto","created_at":"2025-08-20 08:22:40","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1941302,"visible":true,"origin":"","legend":"\u003cp\u003e(a)\u003cstrong\u003e \u003c/strong\u003eNutria raised on the farm. (b) Subcutaneous bleeding in the sick nutria. (c) Nutria’s uterus specimen. (d) Aborted fetus from a nutria’s uterus. (e) Nutria liver specimens.\u003c/p\u003e","description":"","filename":"VetResCom.Nutria.Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7336734/v1/88128370ad6f682599bbf453.jpg"},{"id":89463756,"identity":"849f0939-8743-4c65-acc9-35d5b3c4422d","added_by":"auto","created_at":"2025-08-20 08:14:40","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":4066059,"visible":true,"origin":"","legend":"\u003cp\u003eSpectrophotometry data of standard anticoagulant rodenticides (ARs) and the liver specimen of a nutria. Arrows show the peak points of warfarin (a), coumatetralyl (b), difenacoum (c), bromadiolone (d) and liver specimen (e). X - axis: optical density (OD).\u003c/p\u003e\n\u003cp\u003eY - axis: wavelength (nanometers).\u003c/p\u003e","description":"","filename":"VetResCom.Nutria.Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7336734/v1/5db59e1e6b84aee8d1ebd41e.jpg"},{"id":95563849,"identity":"4f384004-fb7a-4d8f-8e5b-c7a29528a984","added_by":"auto","created_at":"2025-11-10 15:59:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6447432,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7336734/v1/780ce19b-4d9d-411a-9018-c370ea7ba046.pdf"},{"id":89463750,"identity":"138606f6-8ea7-4bee-a645-925a516fc6fe","added_by":"auto","created_at":"2025-08-20 08:14:40","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":31960,"visible":true,"origin":"","legend":"","description":"","filename":"VetResCom.Nutria.additionalfile.docx","url":"https://assets-eu.researchsquare.com/files/rs-7336734/v1/593476bd8a9816a97623ee9c.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Anticoagulant rodenticide toxicosis in nutria (Myocastor coypus) in Thailand","fulltext":[{"header":"Background","content":"\u003cp\u003eThe nutria, or coypu (\u003cem\u003eMyocastor coypus\u003c/em\u003e), is a large, semiaquatic herbivorous rodent originally native to South America but now found in Africa, Europe, North America, and Asia (Carter and Leonard \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Pedruzzi et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Nutrias are mammals belonging to the order \u003cem\u003eRodentia\u003c/em\u003e and the family \u003cem\u003eMyocastoridae\u003c/em\u003e (Wood et al. 1992). They have a robust, highly arched body covered in fur that varies in color from light brown to reddish, or from greyish dark brown to black. Nutrias have short legs and a long, rounded tail (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Their head is large and nearly triangular, with small ears and long vibrissae (Wood et al. 1992). Adult nutrias typically weigh between 5 and 10 kg and have an external body length ranging from approximately 472 to 575 mm (Wood et al. 1992; Guichon et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). They are well adapted to aquatic ecosystems and are known to consume large quantities of aquatic plants.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the past, the nutria was widely recognized as one of the most invasive alien mammals globally, with significant impacts on natural ecosystems, agricultural crops and, potentially human health (Pedruzzi et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). By the early 1800s, the nutria pelt trade had become a major industry in South America, with pelts and furs exported to Europe for use in fashion accessories such as hats and collars (Saadoun and Cabrera \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). However, when the nutria fur market collapsed in the 1940s and again between 1990 and 2000, many ranchers, unable to afford the costs of feeding and housing the animals, released thousands of nutrias into the wild. Combined with accidental escapes from farms over time, these events likely contributed to the invasive spread of nutrias in regions where they were originally introduced by the pelt and fur industry (Saadoun and Cabrera \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Countries affected include the USA, Russia, Poland, France, and Spain, as well as Japan, Korea, and Iran (Farashi and Najafabadi \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Hong et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Today, nutrias are primarily farmed through selectively bred animals known as \u0026ldquo;nutria mutations\u0026rdquo;, which have been developed through breeding programs in many countries, particularly in Poland (Saadoun and Cabrera \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In addition to the standard fur color, nutria mutations exhibit a variety of fur colors, including black, blue, albino, yellow, silver, and multicolored varieties (Tumova et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn Thailand, nutrias were imported from China and Taiwan in the 1990s for their fur and meat, and were also used in hunting, which led to the establishment of wild populations a few years later (Carter and Leonard \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Pedruzzi et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). These nutrias began to live freely in agricultural areas, where their populations were controlled through the use of rodenticides and hunting. Today, selectively bred nutria mutations are introduced as exotic pets in Thailand, and a few nutria farms are located in the central region of Thailand. In general, nutria mutations are healthy and relatively easy to raise. They are housed on farms and fed with rabbit food, guinea pig food, grass, hay, fruits, and vegetables. However, nutrias display natural behaviors such as curiousity-driven exploration, burrowing, and digging (Kang et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), which may expose them to toxic substances present in the soil or surrounding environment, including rodenticides and insecticides. Recent studies have highlighted the environmental contamination caused by anticoagulant rodenticides (ARs), which can result in morbidity or mortality in nontarget animal species (Chansiripornchai et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Chansiripornchai et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Nakayama et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eARs have been widely used worldwide since the mid-20th century to control rodent populations in urban settings, agricultural environments, and habitat conservation areas (Vicedo\u003c/p\u003e\u003cp\u003eet al. 2024). ARs are classified into first-generation compounds, such as warfarin and diphacinone, and second-generation compounds, such as brodifacoum, difenacoum and bromadiolone (Hovda et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Second-generation ARs are persistent, bioaccumulative, and highly toxic compounds, and they are currently the most widely used products for rodent control (Vicedo et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Watt et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Both generations of ARs disrupt vitamin K-dependent clotting factor synthesis in the liver, potentially leading to life-threatening coagulopathy (Hovda et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAlthough ARs are intended for use against rodents, toxicosis in nontarget species\u0026minus;either through accidental or intentional exposure\u0026minus;is a growing global concern (Caloni et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Between 1998 and 2015, 30 studies reported primary or secondary exposure to, and poisoning by, ARs in nontarget animals (Nakayama et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Data from animal poison control centers indicate that rodenticides are among the top toxins to which pets are exposed, accounting for 3.8% of reported cases in Europe and 7% in the USA (ASPCA 2024; VPIS 2022). Exposure to ARs can occur through primary routes, such as the direct ingestion of toxic baits, or through secondary routes, including the consumption of contaminated materials or prey animals previously exposed to the compounds (Nakayama et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Vicedo et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Given the significant risks associated with AR exposure, it is crucial to study and document cases of AR toxicosis to improve our understanding of their impact on various animal species and to inform appropriate mitigation strategies.\u003c/p\u003e\u003cp\u003eThis report describes a fatal case of toxicosis in nutria, likely caused by AR exposure due to environmental contamination, marking the first documented case in Thailand. The findings are particularly significant given the widespread use of ARs in both agricultural and urban environments. The diagnosis is supported by through clinical observations, chemical analyses, and pathological examinations, which collectively strengthen the conclusion of AR-induced toxicosis.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eCase history\u003c/h2\u003e\u003cp\u003eA 15-month-old female nutria, raised on a farm in central Thailand, was found dead and submitted for routine necropsy at the Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Thailand. A liver specimen was subsequently sent to the Department of Veterinary Pharmacology (DVPCU) for analysis of AR exposure. Since 1990, the DVPCU has served as one of Thailand\u0026rsquo;s toxicological centers, providing toxicant analysis such as rodenticides, insecticides, herbicides, and mycotoxins for animal hospitals, veterinarians, general practitioners, and the general public.\u003c/p\u003e\u003cp\u003eAccording to the provided history, the farm housed seven female and one male nutria. All eight nutrias were housed in both indoor and outdoor enclosures. In January 2024, six of the female nutrias died within 1\u0026ndash;2 days following the onset of clinical signs. The owner reported that prior to the incident, all nutrias appeared healthy, exhibiting normal eating, drinking, and behavioral patterns. Their diet consisted of commercial rabbit or guinea pig food, grass, hay, and fresh fruits and vegetables. Additionally, recognizing the species\u0026rsquo; natural tendency to dig and burrow, the owner had provided access to an outdoor area with a soil-based ground surface to support this behavior.\u003c/p\u003e\u003cp\u003eHowever, several days prior to the onset of clinical signs, six of the nutrias were exposed to newly purchased soil and mud from a commercial supplier. These six individuals actively engaged in digging and burrowing within the new soil, whereas the remaining two nutrias\u0026minus;housed separately\u0026minus;had no contact with it. The owner initially observed symptoms including anorexia, followed by ataxia, seizures, abnormal bleeding, abortion, and death within 1\u0026ndash;2 days (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb-e). Notably, the two nutrias that were not exposed to the new soil remained healthy and exhibited no clinical signs.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eSample analysis for AR screening\u003c/h3\u003e\n\u003cp\u003eFor the chemical investigation of ARs, the nutria liver specimen was analyzed using thin-layer chromatography (TLC) and derivative spectrophotometry, as previously described by Kaewamatawong et al. (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Briefly, the liver specimen was homogenized and extracted with chloroform under vaporous conditions. The extract was filtered, and the remaining residue was re-extracted and re-filtered. The final residue was then reconstituted in 1 ml of chloroform. TLC separation was performed using silica gel G plates (Merck, USA) as the stationary phase and a mobile phase consisting of a methyl ethyl ketone and benzene mixture (6:120, v/v). Standard solutions and control extracts from animal samples were prepared. Quantification was achieved by spiking the test sample extracts with AR standards\u0026minus;namely warfarin, coumatetralyl, difenacoum, and bromadiolone (Sigma-Aldrich, USA)\u0026minus;and analyzing them according to the standard TLC protocol. For spot detection, TCL plates were oversprayed sequentially with hydrogen peroxide and ferric chloride solutions. A sample was considered AR-positive when both TLC and spectrophotometric analyses yielded positive results.\u003c/p\u003e\n\u003ch3\u003eClinical findings\u003c/h3\u003e\n\u003cp\u003eGross pathological examination of the dead nutrias revealed moderate autolysis, with a body condition score of 3 out of 5. There were no remarkable lesions on the external appearance, except for subcutaneous hemorrhage in the caudal region (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The lungs showed approximately 60\u0026ndash;70% diffuse redness with scattered firm areas and regions of pale emphysema. The uterus revealed dark red to brown discoloration with marked congestion of the uterine blood vessels. A single mummified fetus was evident at the cervical opening (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec-d). The right uterine horn was enlarged and contained several fetal sac-like structures attached to the endometrial lining. No significant gross lesions were observed in the liver, kidneys, spleen, or gastrointestinal tract.\u003c/p\u003e\u003cp\u003eChemical analysis of the liver specimen confirmed AR intoxication. TLC and derivative spectrophotometry identified AR compounds by matching the sample\u0026rsquo;s peak points with those of known AR standards (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-e). Although no obvious hemorrhagic lesions were observed in the liver during gross examination (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee), AR exposure was clearly confirmed through the positive results obtained from both TLC and spectrophotometric analyses.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe nutria (\u003cem\u003eMyocastor coypus\u003c/em\u003e), a prolific herbivorous rodent native to South America, is farmed in many countries primarily for its pelt, using selectively bred individuals known as nutria mutations. Its meat is often considered a by-product of the fur industry (Saadoun and Cabrera \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In Thailand, nutrias are kept primarily as exotic pets and zoo animals. As their presence in captivity increases, understanding the health concerns and disease profiles of nutrias become essential for effective husbandry, veterinary care and long-term population management.\u003c/p\u003e\u003cp\u003eARs are widely used to control rodent populations in both urban and agricultural environments. While these compounds are effective in reducing health risks to humans and mitigating economic losses, their widespread application has led to unintended and sometimes severe consequences for nontarget species across multiple countries (Chansiripornchai et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Lohr \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Nakayama et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Despite the growing presence of nutrias in various regions, there is limited literature on their health status, particularly regarding non-infectious diseases. Notably, rodenticide-induced toxicosis in nutria has not been previously reported. In this case, AR intoxication was identified in the liver specimen of a nutria. Chemical analysis using TLC and spectrophotometry confirmed the presence of ARs.\u003c/p\u003e\u003cp\u003eAlthough advanced analytical techniques such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) are often preferred for the precise identification and quantification of ARs, TLC and spectrophotometry provide reliable, accessible alternatives for screening (Chansiripornchai et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Kaewamatawong et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Given that ARs do not occur naturally in mammalian tissues and that supporting clinical and environmental data suggest exposure, a qualitative diagnostic approach remains suitable for confirming AR intoxication (Gallocchio et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Accordingly, our laboratory employs qualitative analysis via TLC and spectrophotometry to determine the presence of ARs in liver specimens. Both techniques are simple, cost-effective, and valuable tools for confirming AR intoxication, particularly in cases where ingestion was not witnessed. Therefore, a positive result indicates that the animal was exposed to some quantity of ARs, supporting a diagnosis of AR intoxication (Chansiripornchai et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Chansiripornchai et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe clinical signs observed in the affected nutria in this report, such as anorexia, lethargy, and ataxia, were consistent with the typical manifestations of AR intoxication. Notably, anorexia is often the first visible sign of AR poisoning in rodents (Chansiripornchai et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Fisher et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In addition, subcutaneous hemorrhage was observed in all deceased nutrias, aligning with gross pathological findings commonly associated with AR intoxication in mammals, including rodents (Chansiripornchai et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Hovda et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Although hemorrhagic lesions were not obviously seen in the liver specimen of the nutria examined, AR exposure was definitively confirmed through positive results from both TLC and spectrophotometry analyses. This highlights the importance of chemical diagnostics in detecting AR toxicosis, especially when classical lesions are not apparent during necropsy.\u003c/p\u003e\u003cp\u003eDuring gross pathological inspection, the pathologists (SW and ST) identified fetal abortion in the nutria carcass. According to the owner\u0026rsquo;s report, all four pregnant nutrias experienced abortion accompanied by massive hemorrhage prior to death. This observation aligns with previous studies reporting that ARs can induce abortion in various mammalian species, including humans, dogs, and mares (Chetot et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Fitzgerald et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Zakian et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Pregnancy represents a critical physiological period during which females, early embryos, and developing fetuses are particularly vulnerable to the toxic effects of anticoagulants. As such, ARs may result in adverse fetal outcomes, including spontaneous abortion, fetal death (fetotoxicity), or other forms of teratogenic effects through transplacental transfer (Chetot et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Fitzgerald et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Hovda et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Following the incident, the surviving female and male nutrias were relocated to a different area of the farm and placed under close veterinary observation. During the 18-month follow-up period, both nutrias remained healthy, and the female nutria successfully gave birth to healthy offspring.\u003c/p\u003e\u003cp\u003eThe exact source of ARs detected in this case remains uncertain but is most likely attributable to environmental contamination. According to the history provided by the owners, all nutrias consumed the same feed; however, a new environmental variable was introduced\u0026minus;soil. The owners had recently purchased soil from a local supplier to develop a new farming area. This soil was reportedly obtained from post-harvest rice fields. All of the affected nutrias had direct contact with the newly introduced soil through digging and burrowing activities prior to developing clinical signs and dying. In contrast, the only surviving nutria had been housed separately and did not come into contact with this soil, and notably exhibited no clinical abnormalities. These observations strongly suggest that the newly acquired soil may have been the source of AR exposure.\u003c/p\u003e\u003cp\u003ePesticides, including rodenticides, are routinely used in agricultural settings to protect crops and control rodent pests. Although testing the suspected soil for AR residues was not possible due to its unavailability by the time of investigation, the circumstantial evidence supports the likelihood of soil-based contamination. Despite national efforts to promote organic farming practices in Thailand, many farmers continue to rely heavily on chemical pesticides, including rodenticides (Angsoongnern, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). These compounds are known to persist in the environment for extended periods, contributing to soil and water contamination through direct application or surface runoff. Consequently, rodenticides not only pose a threat to target pests but may also adversely affect nontarget animals, local ecosystems, and even human health (Angsoongnern, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Chansiripornchai et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThese findings highlight the importance of judicious use of rodenticides to minimize risks and ensure the safety of humans, animals, and the environment. Our findings suggest that the use of ARs may unintentionally poison nontarget animals. Recent studies have highlighted that ARs can contribute to environmental contamination through residues, leading to mortality or morbidity in nontarget species. Additionally, the presence of these substances in the environment poses a significant risk to public health (Chansiripornchai et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Nakayama et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Vicedo et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The results emphasize the urgent need for improved rodenticide regulation, environmental monitoring, and responsible pest management strategies to safeguard animal health, biodiversity, and public health.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis case represents the first reported diagnosis of AR poisoning in nutria, based on clinical history, observed clinical signs, and confirmation through chemical analysis using TLC and spectrophotometry. The findings suggest that environmental contamination, likely through AR residues in newly introduced soil, may have been a critical factor contributing to the mortality of the affected animals. This underscores the importance of responsible AR use and the need for greater awareness of its potential ecological impacts. Careful management and regulation of AR application are essential to prevent unintended harm to nontarget species, protect environmental health, and support sustainable farming practices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the nutria owners for their kind cooperation during data collection. We also extend our thanks to Assistant Professor Simon Jeremy Peter Wright, Faculty of Arts, Chulalongkorn University, for his assistance with English language editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePC\u003c/strong\u003e contributed to the design, performed clinical studies, collected animal patient data, analyzed the data and prepared the manuscript. \u003cstrong\u003eSW\u003c/strong\u003e contributed to pathological investigation. \u003cstrong\u003eST\u0026nbsp;\u003c/strong\u003econtributed to\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003epathological study and manuscript preparation. All authors have read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable for specimens from the carcass.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ewas obtained from the owners.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAngsoongnern S (2015) Environmental impact from pesticide utilization. EAU Heritage J Sci Tech 9: 50 \u0026ndash; 63 \u003c/li\u003e\n\u003cli\u003eASPCA Animal Poison Control Center (2024) Top 10 toxins of 2024 https://www.aspcapro.org/resource/top-10-toxins-2024. Accessed 5 August 2025.\u003c/li\u003e\n\u003cli\u003eCaloni F, Cortinovis C, Rivolta M, Davanzo F (2016) Suspected poisoning of domestic animals by pesticides Sci Total Environ 539: 331 \u0026ndash; 336https://doi.org/10.1016/j.scitotenv.2015.09.005\u003c/li\u003e\n\u003cli\u003eCarter J, Leonard BP (2002) A review of the literature on the worldwide distribution, spread of, and efforts to eradicate the coypu (\u003cem\u003eMyocastor coypus\u003c/em\u003e) Wildl Soc Bull 30: 162\u0026ndash;175 \u003c/li\u003e\n\u003cli\u003eChansiripornchai P, Hunprasit V, Techangamsuwan S (2025) First report on the occurrence of anticoagulant rodenticides toxicosis in nontarget animals in Thailand BMC Vet Res 21: 337 https://doi.org/10.1186/s12917-025-04789-7\u003c/li\u003e\n\u003cli\u003eChansiripornchai P, Kesdangsakonwut S, Techangamsuwan S (2024) Anticoagulant rodenticide poisoning in farmed Patagonian mara (\u003cem\u003eDolichotis patagonum\u003c/em\u003e) BMC Vet Res 20: 83 https://doi.org/10.1186/s12917-024-03943-x\u003c/li\u003e\n\u003cli\u003eChetot T, Taufana S, Benoit E, Lattard V (2020) Vitamin K antagonist rodenticides display different teratogenic activity Repro Tox 93: 131 \u0026ndash; 136. https://doi.org/10.1016/j.reprotox.2020.02.003\u003c/li\u003e\n\u003cli\u003eFarashi A, Najafabadi MS (2015) Modeling the spread of invasive nutrias (\u003cem\u003eMyocastor coypus\u003c/em\u003e) over Iran Ecol Complex 22: 59\u0026ndash;64\u003c/li\u003e\n\u003cli\u003eFisher P, Campbell KJ, Howald GR, Warburton B (2019) Anticoagulant rodenticides, islands and animal welfare accountancy Animals doi:10.3390/ani9110919 https://doi.org/10.3390/ani9110919\u003c/li\u003e\n\u003cli\u003eFitzgerald SD, Martinez J, Buchweitz JP (2018) An apparent case of brodifacoum toxicosis in a whelping dog J Vet Diag Invest 30: 169 \u0026ndash; 171 https://doi.org/10.1177/1040638717741664\u003c/li\u003e\n\u003cli\u003eGallocchio F, Basilicata L, Benetti C, Angeletti R, Binato G (2014) Multi \u0026ndash; residue determination of eleven anticoagulant rodenticides by high - performance liquid chromatography with diode array / fluorimetric detection: Investigation of suspected animal poisoning in the period 2012 - 2013 in north - eastern Italy Forensic Sci Inter 244: 63 \u0026ndash; 69\u003c/li\u003e\n\u003cli\u003eGuichon ML, Benitez VB, Abba A, Borgnia M, Cassini MH (2003) Foraging behaviour of coypus \u003cem\u003eMyocastor coypus\u003c/em\u003e: Why do coypus consume aquatic plants? Acta Oecologica 24: 241\u0026ndash;246\u003c/li\u003e\n\u003cli\u003eHong S, Do Y, Kim JY, Kim D, Joo G (2015) Distribution, spread and habitat preferences of nutria (\u003cem\u003eMyocastor coypus\u003c/em\u003e) invading the lower Nakdong River, South Korea Biol Invas 17: 1485\u0026ndash;1496\u003c/li\u003e\n\u003cli\u003eHovda LR, Brutlag AG, Poppenga RH, Epstein SE (2024) Anticoagulant Rodenticides In: Small Animal Toxicology. 3\u003csup\u003erd\u003c/sup\u003e ed. Wiley Blackwell, New Jersey, USA pp 787 \u0026ndash; 794\u003c/li\u003e\n\u003cli\u003eKaewamatawong T, Lohavanijaya A, Charoenlertkul P, Srichairat S (2011) Retrospective histopathological study of hemorrhagic lesion of coumarin intoxication in dogs Thai J Vet Med 41: 239 \u0026ndash; 244 https://doi.org/10.56808/2985-1130.2302\u003c/li\u003e\n\u003cli\u003eKang W, Kim G, Park Y (2022) Habitat suitability and connectivity modeling predict genetic population structure and priority control areas for invasive nutria (\u003cem\u003eMyocastor coypus\u003c/em\u003e) in a temperate river basin PLoS ONE 17: e0279082\u003c/li\u003e\n\u003cli\u003eLohr MT (2018) Anticoagulant rodenticide exposure in an Australian predatory bird increases with proximity to developed habitat Sci Total Environ 643: 134\u0026ndash;144 https://doi.org/10.1016/j.scitotenv.2018.06.207\u003c/li\u003e\n\u003cli\u003eNakayama SM, Morita A, Ikenaka Y, Mizukawa H, Ishizuka M (2019) A review: Poisoning by anticoagulant rodenticides in non - target animals globally. J Vet Med Sci 81: 298 - 313\u003c/li\u003e\n\u003cli\u003ePedruzzi L, Schertler A, Giuntini S, Leggiero I, Mori E (2022) An update on the distribution of the coypu, \u003cem\u003eMyocastor coypus\u003c/em\u003e, in Asia and Africa through published literature, citizen-science and online platforms Mamm Biol 102: 109\u0026ndash;118\u003c/li\u003e\n\u003cli\u003eSaadoun A, Cabrera MC (2019) A Review of productive parameters, nutritive value and technological characteristics of farmed nutria meat (\u003cem\u003eMyocastor coypus\u003c/em\u003e) Meat Sci 148: 137\u0026ndash;149\u003c/li\u003e\n\u003cli\u003eTumova E, Chodova D, Svobodova J, Uhlirova L, Volek Z (2015) Carcass composition and meat quality of Czech genetic resources of nutrias (\u003cem\u003eMyocastor coypus\u003c/em\u003e) Czech J Anim Sci 60: 479\u0026ndash;486\u003c/li\u003e\n\u003cli\u003eVicedo T, Navas I, Maria-Mojica P, Garc\u0026iacute;a-Fernandez AJ (2024) Widespread use of anticoagulant rodenticides in agricultural and urban environments. A menace to the viability of the endangered Bonelli\u0026rsquo;s eagle \u003cem\u003e(Aquila fasciata) \u003c/em\u003epopulations Environ Poll 358: 124530. https://doi.org/10.1016/j.envpol.2024.124530\u003c/li\u003e\n\u003cli\u003eVPIS Veterinary Poisons Information Service (2022) Annual Report 2022. https://www.vpisglobal.com/annual-reports. Accessed 5 August 2025.\u003c/li\u003e\n\u003cli\u003eWatt BE, Proudfoot AT, Bradberry SM, Vale JA (2005) Anticoagulant rodenticides Toxicol Rev 24: 259 \u0026ndash; 269 https://doi.org/10.2165/00139709-200524040-00005\u003c/li\u003e\n\u003cli\u003eWoods CA, Contreras L, Willner-Chapman G, Whidden P (1992) \u003cem\u003eMyocastor coypus\u003c/em\u003e Mamm Spec 398: 1 \u0026ndash; 8\u003c/li\u003e\n\u003cli\u003eZakian A, Mami S, Nouri M, Jalali SM, Tehrani-Sharif M (2019) Brodifacoum toxicosis and abortion in an Arabian mare Vet Res Forum 10: 173 \u0026ndash; 176 doi:10.30466/vrf.2018.85534.2115\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"veterinary-research-communications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"verc","sideBox":"Learn more about [Veterinary Research Communications](https://www.springer.com/journal/11259)","snPcode":"11259","submissionUrl":"https://submission.nature.com/new-submission/11259/3","title":"Veterinary Research Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"contamination, Myocastor coypus, nutria, poisoning, rodenticide, toxicosis","lastPublishedDoi":"10.21203/rs.3.rs-7336734/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7336734/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNutria (\u003cem\u003eMyocastor coypus\u003c/em\u003e) is a large, herbivorous rodent found in Africa, Europe, North America, and Asia. Anticoagulant rodenticide (AR) toxicosis was diagnosed in nutrias based on history taking, clinical signs and chemical analysis, marking the first confirmed case in this species in Thailand. Six out of the eight nutrias in the same herd died, showing initial clinical signs such as abnormal bleeding and abortion in pregnant individuals. The carcasses of the dead nutrias were analysed for exposure to rodenticides and insecticides. Screening tests on liver specimens, using thin-layer chromatography and spectrophotometry, confirmed the presence of AR. In contrast, the two survival nutrias were clinically observed and remained healthy during an 18-month follow-up period. To date, there have been no reports of nutrias with diagnosed AR poisoning. This case likely resulted from rodenticide contamination in agricultural settings, underscoring the importance of proper rodenticide management to protect nontarget species and prevent environment contamination.\u003c/p\u003e","manuscriptTitle":"Anticoagulant rodenticide toxicosis in nutria (Myocastor coypus) in Thailand","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-20 08:14:35","doi":"10.21203/rs.3.rs-7336734/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-24T06:55:16+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-24T02:45:07+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-23T14:08:32+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-20T19:14:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"52749201395819308010666807568181635308","date":"2025-08-14T23:41:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"27556518869555821140998887539046654869","date":"2025-08-13T07:38:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"175829840209037647395771694115113157148","date":"2025-08-12T15:49:38+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-12T14:58:02+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-12T12:27:10+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-12T12:26:43+00:00","index":"","fulltext":""},{"type":"submitted","content":"Veterinary Research Communications","date":"2025-08-10T04:20:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"veterinary-research-communications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"verc","sideBox":"Learn more about [Veterinary Research Communications](https://www.springer.com/journal/11259)","snPcode":"11259","submissionUrl":"https://submission.nature.com/new-submission/11259/3","title":"Veterinary Research Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"33179fe1-3303-45fe-b269-3303b19d02b3","owner":[],"postedDate":"August 20th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-10T15:58:29+00:00","versionOfRecord":{"articleIdentity":"rs-7336734","link":"https://doi.org/10.1007/s11259-025-10957-9","journal":{"identity":"veterinary-research-communications","isVorOnly":false,"title":"Veterinary Research Communications"},"publishedOn":"2025-11-03 15:56:50","publishedOnDateReadable":"November 3rd, 2025"},"versionCreatedAt":"2025-08-20 08:14:35","video":"","vorDoi":"10.1007/s11259-025-10957-9","vorDoiUrl":"https://doi.org/10.1007/s11259-025-10957-9","workflowStages":[]},"version":"v1","identity":"rs-7336734","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7336734","identity":"rs-7336734","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}