Reference intervals for eye temperature measured by infrared thermography and rectal temperature in dogs

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Woodruff, Abigail McBride, David R. Smith This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9372827/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective. To estimate a reference interval (RI) for eye temperature (ET) in apparently healthy shelter dogs using a robust method suitable for moderate sample sizes, and to provide a comparative reference interval for rectal temperature (RT). Methods. This cross-sectional study analyzed ET measurements from a field dataset collected in a municipal shelter. The study population consisted of 78 apparently healthy dogs. ET was obtained with a handheld thermal camera under standardized procedures. Rectal temperatures were obtained from the same dogs using a digital rectal thermometer. The central 95% RI was estimated using a robust statistical method with bootstrap-derived 90% confidence intervals (CIs) for the limits, an approach recommended for datasets with 40 ≤ n < 120 observations. Results. The estimated 95% RI for ET was 35.0-38.5°C with 90% CIs of 34.7–35.4°C (lower limit) and 38.2–38.8°C (upper limit). The 95% RI for RT was 37.5–39.7°C with 90% CIs of 37.3–37.8°C (lower limit) and 39.5–39.9°C (upper limit). Conclusions. These findings provide RIs for ET and RT in apparently healthy shelter dogs. Values approaching or exceeding these limits may warrant additional clinical evaluation. The intervals may serve as an initial benchmark for temperature assessment in similar populations. Clinical Relevance . Population-based RIs for eye and rectal temperatures of dogs are needed to assist veterinarians and shelter personnel in interpreting ET and RT measurements and identifying dogs that might require further clinical examination. Ocular thermography may offer a practical screening tool for body temperature assessment in shelter settings where rapid, low-stress evaluation is desirable. Veterinary Epidemiology Canine infrared thermography eye temperature rectal temperature reference interval shelter medicine. Figures Figure 1 Figure 2 Figure 3 Introduction Population-based reference intervals (RIs) are critical for interpreting physiological measurements because they describe the expected distribution of values in carefully defined healthy populations and thereby distinguish normal from abnormal observations. 1 , 2 In contrast to diagnostic decision limits, which are about clinical outcomes or risk and often derived from case-control data, RIs are descriptive, method- and population-specific constructs that must be established and reported with transparent attention to preanalytical, analytical, and statistical sources of variation. 1 – 3 In veterinary clinical pathology, the American Society for Veterinary Clinical Pathology (ASVCP) and the Clinical and Laboratory Standards Institute (CLSI) provide guidance for de novo RI development, verification, and reporting RI. 2,3 In veterinary clinical pathology, RIs are commonly defined to encompass the central 95% of values in a well-described reference population; their computation and reporting depend on sample size, distributional form, and the need for outlier handling. 2 Reference intervals allow clinicians to distinguish expected biological variation from potentially abnormal findings, but their credibility rests on transparent selection of reference subjects, independence of observations, appropriate estimation methods, and adequate presentation of distributional diagnostics. 2 For canine temperature assessment, rectal temperature (RT) remains the accepted reference for estimating core temperature, and a recent large-scale analysis has helped refine the distribution of RT in adult dogs. 4 However, eye temperature (ET) measured by infrared thermography (IRT) requires its own site and protocol-specific RIs rather than borrowing limits from RT. Establishing RIs for ET in apparently healthy shelter dogs is a necessary step before ET can be used as a screening parameter in intake or daily rounds, where rapid, noncontact measurements are desirable and repeated mass screening is routine. From the IRT perspective, emissivity assumptions, camera warm-up, and temporal stability, and environmental conditions (ambient temperature, humidity) all influence recorded temperatures. 5 – 7 Elias et al., demonstrate that region-of-interest (ROI) choice and humidity materially affect measured values. 7 In our previous study (Rostami et al under review) we identified a small positive association between relative humidity (RH) and ET under kennel conditions. These observations highlight the importance of clearly defining inclusion criteria for healthy animals, standardizing pre-analytical conditions, and thoroughly documenting the measurement protocol, because reference intervals are dependent on these methodological specifications. 1 , 2 , 7 In the shelter setting, additional variability arises from animal movement and kennel barriers. For moderate sample sizes (approximately 40 to < 120), ASVCP guidelines recommend a robust estimation approach for the 95% RI, coupled with 90% confidence intervals (CIs) on the lower and upper limits obtained by bootstrap resampling; this strategy performs well without requiring strict normality requirement. 2 The primary objective of this research was to estimate a reference interval for ocular temperature and RT in a general population of shelter dogs. We intentionally utilized a fast, non-contact measurement method that can be easily integrated into the daily routines. By establishing this baseline range, we aim to provide a practical tool to quickly identify thermal outliers. Material Methods Study design and data source All procedures involving animals were conducted with approval from the Mississippi State University Institutional Animal Care and Use Committee (IACUC). Shelter management provided permission for the participation of dogs under their care. Building upon the standardized imaging protocols established in our previous work, we collected all thermal data indoors while the dogs were unrestrained in their housing units. 8 Briefly, dogs were imaged in-kennel at a municipal shelter using a handheld infrared camera (Fotric 347A) under routine afternoon operating conditions; ambient temperature and relative humidity were recorded at each session. The camera was allowed to stabilize according to the manufacturer’s instructions before use. Emissivity was set at 0.98, and the distance from the dog’s eyes was maintained at approximately 60 cm. Eyes were the primary anatomical site of measurement. We have constructed a single-record, unique-dog dataset as required for RI estimation. Eligibility criteria reflected indicators of health indicators (no reported history of disease from the caretaker, no persistent cough or sneeze, and no visible nasal and ocular discharge). Immediately after the infrared measurements were concluded, RT was recorded for each dog while it stayed in its kennel. A digital thermometer, coated with lubricant, was carefully positioned in the rectum at a fixed depth. We gently supported the dog in a standing posture to maintain stability and minimize stress. We waited for the device to signal a completed reading with an electronic beep before removing it. This specific protocol ensured that all reference temperatures were gathered in a consistent and repeatable manner throughout the study. Statistical analysis Analyses were conducted in R using referenceintervals package, consistent with ASVCP recommendations. 2 , 9 Because the reference sample size comprised 78 unique dogs (40 ≤ n < 120), we followed ASVCP 2 guidance to estimate the central 95% RI using a robust method with 90% confidence intervals (CIs) on the limits derived by bootstrap. This approach is preferred for n between 40 and 120 and does not require strict Gaussian distribution. Data were screened for outliers, which were only removed when there was a documented reason, such as a measurement or recording error, to ensure the integrity of the reference interval estimation. Results In this study we had 78 unique, apparently healthy shelter dogs (Table 4.1). Humidity and ambient temperature during imaging spanned a range of 29%–85% and 20 to 27°C respectively. After careful review, no outliers were identified for either ET or RT, supporting the reliability of the dataset for reference interval estimation. Violin-box plots were used to depict the distributions of ET and RT across age categories and sexes, which provide a visual comparison of temperature variation among these categorical factors (Fig. 4.1). Reference interval analysis With a sample size in the 40–120 range, we estimated the central 95% RI for ET using the robust method with bootstrap confidence intervals. The robust 95% RI was 35.0–38.5°C. The 90% confidence interval (CI) for the lower limit was 34.7–35.4°C, and the 90% CI for the upper limit was 38.2–38.8°C. The 95% RI for RT was 37.5–39.7°C. The 90% confidence interval (CI) for the lower bound was 37.3–37.8°C, while the 90% CI for the upper bound was 39.5–39.9°C (Fig. 4.2 and 4.3). Discussion Using one measurement per dog from a prospective, kennel-side dataset, we established a robust 95% RI for ET in apparently healthy shelter, reporting the limits together with their confidence intervals gives a clear, repeatable standard for future studies. Thermal imaging captures radiative heat from superficial tissues. Measured ET reflects the interplay of local perfusion, tear-film evaporation, and heat exchange with the environment. 5 , 7 , 10 – 13 The ocular surface and medial canthus are richly vascularized and responsive to autonomic tone, making them attractive windows for thermal screening; several veterinary and comparative studies have emphasized these regions as physiologically informative and practically accessible. 7 , 14 – 16 In our study, all images were acquired at a standardized distance following device warm-up and with environmental parameters recorded, consistent with published best-practice recommendations for veterinary thermography. 17 Experimental and field data indicate that ET is linearly associated with RT, rising with activity level or fever. 18 – 21 As a result, site-specific intervals are appropriate and should not be interchanged with rectal RIs. Rectal thermometry is the clinical reference method for assessing body temperature in dogs and its intervals are commonly used as the physiological benchmark when evaluating alternative thermometry approaches. Previous reports indicate that RT in healthy dogs typically fall between approximately 37.9°C and 39.9°C. 22 However, the methodology used to define this range is not described, and it is unclear whether it reflects a statistically derived reference interval or an observational estimate. In a recent data-driven analysis of adult dogs presenting for care, the mean RT was ~ 38.6°C and the 95% RI was 37.7–39.5°C. 4 In our study population, which included both adult dogs and puppies, RT measured in the same animals used for ET assessment had a reference interval of 37.5–39.7°C, using robust method. The difference in the range could be due to age or environment. The close agreement between our findings and previously published adult dog intervals suggests that the dogs in our study were physiologically comparable to typical populations, supporting the validity of our ET reference intervals in this cohort. The RT interval estimated in this study was derived from measurements collected under routine shelter conditions. Establishing reference limits under these real-world conditions is valuable because factors such as mild excitement, recent movement, or kennel activity are unavoidable in municipal shelter environments. Another consideration when interpreting RT intervals is the influence of demographic and environmental variability within shelter populations. Dogs entering municipal shelters can vary widely in age, breed, body condition, and recent activity prior to intake. These factors introduce modest variability in measured temperatures, but that provides a robust estimate of RI for generalizable to all apparently healthy dogs. The statistical approach used in this study is designed to accommodate such heterogeneity while still producing reliable interval estimates for moderate sample sizes. As a result, the RT limits reported here may be particularly relevant for operational shelter medicine, where measurements must be interpreted across diverse dog populations rather than narrowly controlled experimental groups. In addition, the use of the same cohort of dogs to estimate both ET and RT intervals provides an internally consistent comparison between surface-based and core temperature measurements. The reported RT RI is greater than our estimated ET RI (35.0-38.5°C), as expected for a surface window subject to evaporative cooling and heat loss. 23 , 24 In contrast, the rectum is an internal site, protected by surrounding tissues, which helps maintain a more stable core temperature largely independent of surface heat exchange or evaporative cooling. In human and veterinary thermometry, similar relationships hold for axillary or tympanic sites versus core reference methods, reinforcing the interpretive principle that the normal range depends on the measurement site and acquisition protocol. 25 – 32 Noncontact imaging minimizes handling, preserves biosecurity, and is suitable for dogs that are reactive or difficult to restrain, and has practical advantages in municipal shelters. Values within the interval provide reassurance in routine checks; values near or outside the limits flag dogs for follow-up, for example, repeat measurement or confirmatory rectal thermometry. This integrated approach is consistent with the broader shelter-medicine literature that excitement and stress can transiently influence ET and short, calm imaging procedures help contain that variability. 7 , 33 The present interval therefore functions best as a screening aid that complements, rather than replaces, targeted clinical examination. This study provides a reference range for ET in dogs under shelter kennel conditions. When used for screening, it should be interpreted with care due to some limitations. Environmental conditions, recent activity, and minor handling stress could affect ET. Therefore, this reference range should be used carefully when applied outside similar shelter settings or in dogs with different physiological or environmental conditions. In addition, while this reference interval defines a normal range for ET under kennel conditions, its ability to detect clinically meaningful changes has not been tested. Determining whether values outside this range reliably indicate fever or other abnormalities will require further studies to determine diagnostic performance. While we did not perform specialized diagnostic testing or detailed ophthalmic exams, our screening process was designed to mirror the actual constraints of veterinary practice. The goal was to establish a normal temperature range using a simplified and realistic protocol that can be reliably performed. This approach ensures that the estimated reference intervals are applicable to real world conditions. In summary, this study reports a robust, reference interval for ET and RT in shelter dogs measured under real-world conditions. The interval’s placement relative to rectal norms is consistent with established thermometry principles. By coupling biologically informed acquisition with best-practice RI estimation, these results offer a practical, evidence-based tool for everyday decision-making in shelter medicine. Declarations Disclosures The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript. Funding This work was supported by funding from the United States Department of Agriculture Agricultural Research Service (USDA ARS) grant no. 58-6064-3-017. The opinions, findings, and conclusions expressed in this study are those of the authors and do not necessarily reflect the views of the USDA. Acknowledgements The authors would like to thank Dr. Jingyi Shi, Dr. W. Isaac Jumper and Dr. Guiming Wang for their valuable guidance and service as members of the doctoral committee during the development of this research. References Ozarda Y (2016) Reference intervals: current status, recent developments and future considerations. Biochemia Med 26(1):5–16. 10.11613/BM.2016.001 Friedrichs KR, Harr KE, Freeman KP et al (2012) ASVCP reference interval guidelines: determination of de novo reference intervals in veterinary species and other related topics. Vet Clin Pathol 41(4):441–453. 10.1111/vcp.12006 Ozarda Y, Higgins V, Adeli K (2019) Verification of reference intervals in routine clinical laboratories: practical challenges and recommendations. 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Comp Exerc Physiol 13(1):37–44. 10.3920/CEP160034 Konietschke U, Kruse BD, Müller R, Stockhaus C, Hartmann K, Wehner A (2018) Comparison of auricular and rectal temperature measurement in normothermic, hypothermic, and hyperthermic dogs. Tierärztliche Praxis Ausgabe K: Kleintiere / Heimtiere 42:13–19. 10.1055/s-0038-1623741 Lukkanawaraporn Y, Tiangtas N, Chaikornkij V et al (2022) Effects of environmental condition, size, coat type, and body condition score on rectal temperature prediction in dogs using infrared auricular and surface temperature. Vet World 15(5):1314–1322. 10.14202/vetworld.2022.1314-1322 Brinnel H, Cabanac M (1989) Tympanic temperature is a core temperature in humans. J Therm Biol 14(1):47–53. 10.1016/0306-4565(89)90029-6 Travain T, Colombo ES, Heinzl E, Bellucci D, Prato Previde E, Valsecchi P (2015) Hot dogs: Thermography in the assessment of stress in dogs ( Canis familiaris )—A pilot study. J Veterinary Behav 10(1):17–23. 10.1016/j.jveb.2014.11.003 Tables Table 1 — Demographic characteristics of the reference sample population. Unique dogs Age Puppy 26 Adult 52 Sex Male 35 Female 43 Size Small 29 Medium 39 Large 10 Coat length Short 59 Medium 14 Long 5 This table presents the frequency distribution of demographic characteristics for the apparently healthy shelter dogs (n = 78) that comprised the reference sample group. Data include age, sex, size, and coat length. This population served as the basis for determining the reference interval for eye temperature and rectal temperature. Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted 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-9372827","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":620586485,"identity":"553b89f6-422b-4cfa-bd29-8c774730ff6b","order_by":0,"name":"Sahar Rostami","email":"","orcid":"https://orcid.org/0009-0005-1023-0840","institution":"Mississippi State University","correspondingAuthor":false,"prefix":"","firstName":"Sahar","middleName":"","lastName":"Rostami","suffix":""},{"id":620586489,"identity":"f45daf45-18c1-488b-8408-82fbff62588b","order_by":1,"name":"Kimberly A. 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Smith","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6klEQVRIiWNgGAWjYBACe/4DDAcYG2zQhHnwaDGckcBw4GBDGoxvAFGNT4vBDSBxsOEwSVq4Ew9/3HFe3uDaAdaNP/78kbdnb2B88LYNj5bzZzccOHjmtuGG2wlst3nbDAx7eA4wG87Fp+VALlBL2+0EydlALYwNBow9Egls0ryEtZwDa7n544+BfY/8A/bfRGg5kMAvncB2g4fNILFHgoGNGZ8WwxlALWfbkg37pRPbgH4xTu45k9gsOeccbi32/Gc3f6hss5Nnk04+BnSYnG17++GDH96U4daCBBgb0BmjYBSMglEwCsgFADt+XLPy/jfrAAAAAElFTkSuQmCC","orcid":"","institution":"Mississippi State University","correspondingAuthor":true,"prefix":"","firstName":"David","middleName":"R.","lastName":"Smith","suffix":""}],"badges":[],"createdAt":"2026-04-09 23:16:15","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":true,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":true},"doi":"10.21203/rs.3.rs-9372827/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9372827/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106919497,"identity":"557948b0-0d8b-48cf-96fa-bbbf5f34ab99","added_by":"auto","created_at":"2026-04-14 19:10:27","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":263577,"visible":true,"origin":"","legend":"\u003cp\u003eDistributions of eye temperature (ET) and rectal temperature (RT) by age and sex in shelter dogs. This figure presents violin and box plots illustrating the distributions of ET and RT in shelter dogs by age and sex (n=78). Panels (A) and (B) show ET distributions by age group and sex, respectively, while panels (C) and (D) display RT distributions by the same factors. The boxplots indicate the median and interquartile range, the whiskers show the full data range, and the violin shapes represent kernel density estimates of the distribution.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9372827/v1/5519aeff619245d74167eb81.jpeg"},{"id":106961043,"identity":"16648906-0dee-4c98-bac2-c20621f89695","added_by":"auto","created_at":"2026-04-15 09:24:03","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":285272,"visible":true,"origin":"","legend":"\u003cp\u003eSorted values (caterpillar) with RI and 90% CIs. \u0026nbsp;The calculated 95% RI for ET was determined to be 35.0°C to 38.5 °C. This plot visualizes these reference limits in relation to the sorted distribution of the 78 temperature measurements from the reference population. The dashed lines indicate the 90% confidence intervals for the lower and the upper limits, demonstrating the precision of these estimates.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9372827/v1/70cf7abdfaa4385fc02fd049.jpeg"},{"id":106919504,"identity":"7b887dd0-6857-457b-a2ff-de9985ca035b","added_by":"auto","created_at":"2026-04-14 19:10:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":22014,"visible":true,"origin":"","legend":"\u003cp\u003eOrdered distribution of rectal temperature (RT) with reference interval and confidence limits. The caterpillar plot presents the ordered RT values along with the estimated 95% reference interval (37.5°C - 39.7°C). Dashed lines denote the 90% confidence intervals for the lower and upper limits, providing an indication of the precision of these estimates. The visualization shows how the reference boundaries relate to the distribution of temperatures obtained from 78 healthy dogs.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9372827/v1/b99dc220d55d2360e3dd9bf2.png"},{"id":106994160,"identity":"73ed701d-c36c-4048-b6c3-13dca7e81a79","added_by":"auto","created_at":"2026-04-15 15:05:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":982839,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9372827/v1/03bafe63-55b6-4a94-bc13-e5ad607c237e.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eReference intervals for eye temperature measured by infrared thermography and rectal temperature in dogs\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePopulation-based reference intervals (RIs) are critical for interpreting physiological measurements because they describe the expected distribution of values in carefully defined healthy populations and thereby distinguish normal from abnormal observations.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e In contrast to diagnostic decision limits, which are about clinical outcomes or risk and often derived from case-control data, RIs are descriptive, method- and population-specific constructs that must be established and reported with transparent attention to preanalytical, analytical, and statistical sources of variation.\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e In veterinary clinical pathology, the American Society for Veterinary Clinical Pathology (ASVCP) and the Clinical and Laboratory Standards Institute (CLSI) provide guidance for de novo RI development, verification, and reporting RI.\u003csup\u003e2,3\u003c/sup\u003e In veterinary clinical pathology, RIs are commonly defined to encompass the central 95% of values in a well-described reference population; their computation and reporting depend on sample size, distributional form, and the need for outlier handling.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e Reference intervals allow clinicians to distinguish expected biological variation from potentially abnormal findings, but their credibility rests on transparent selection of reference subjects, independence of observations, appropriate estimation methods, and adequate presentation of distributional diagnostics.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eFor canine temperature assessment, rectal temperature (RT) remains the accepted reference for estimating core temperature, and a recent large-scale analysis has helped refine the distribution of RT in adult dogs.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e However, eye temperature (ET) measured by infrared thermography (IRT) requires its own site and protocol-specific RIs rather than borrowing limits from RT. Establishing RIs for ET in apparently healthy shelter dogs is a necessary step before ET can be used as a screening parameter in intake or daily rounds, where rapid, noncontact measurements are desirable and repeated mass screening is routine.\u003c/p\u003e \u003cp\u003eFrom the IRT perspective, emissivity assumptions, camera warm-up, and temporal stability, and environmental conditions (ambient temperature, humidity) all influence recorded temperatures.\u003csup\u003e\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e Elias et al., demonstrate that region-of-interest (ROI) choice and humidity materially affect measured values.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e In our previous study (Rostami et al under review) we identified a small positive association between relative humidity (RH) and ET under kennel conditions. These observations highlight the importance of clearly defining inclusion criteria for healthy animals, standardizing pre-analytical conditions, and thoroughly documenting the measurement protocol, because reference intervals are dependent on these methodological specifications.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e In the shelter setting, additional variability arises from animal movement and kennel barriers.\u003c/p\u003e \u003cp\u003eFor moderate sample sizes (approximately 40 to \u0026lt;\u0026thinsp;120), ASVCP guidelines recommend a robust estimation approach for the 95% RI, coupled with 90% confidence intervals (CIs) on the lower and upper limits obtained by bootstrap resampling; this strategy performs well without requiring strict normality requirement.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e The primary objective of this research was to estimate a reference interval for ocular temperature and RT in a general population of shelter dogs. We intentionally utilized a fast, non-contact measurement method that can be easily integrated into the daily routines. By establishing this baseline range, we aim to provide a practical tool to quickly identify thermal outliers.\u003c/p\u003e"},{"header":"Material Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and data source\u003c/h2\u003e \u003cp\u003e All procedures involving animals were conducted with approval from the Mississippi State University Institutional Animal Care and Use Committee (IACUC). Shelter management provided permission for the participation of dogs under their care. Building upon the standardized imaging protocols established in our previous work, we collected all thermal data indoors while the dogs were unrestrained in their housing units.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e Briefly, dogs were imaged in-kennel at a municipal shelter using a handheld infrared camera (Fotric 347A) under routine afternoon operating conditions; ambient temperature and relative humidity were recorded at each session. The camera was allowed to stabilize according to the manufacturer\u0026rsquo;s instructions before use. Emissivity was set at 0.98, and the distance from the dog\u0026rsquo;s eyes was maintained at approximately 60 cm. Eyes were the primary anatomical site of measurement. We have constructed a single-record, unique-dog dataset as required for RI estimation. Eligibility criteria reflected indicators of health indicators (no reported history of disease from the caretaker, no persistent cough or sneeze, and no visible nasal and ocular discharge).\u003c/p\u003e \u003cp\u003eImmediately after the infrared measurements were concluded, RT was recorded for each dog while it stayed in its kennel. A digital thermometer, coated with lubricant, was carefully positioned in the rectum at a fixed depth. We gently supported the dog in a standing posture to maintain stability and minimize stress. We waited for the device to signal a completed reading with an electronic beep before removing it. This specific protocol ensured that all reference temperatures were gathered in a consistent and repeatable manner throughout the study.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAnalyses were conducted in R using \u003cem\u003ereferenceintervals\u003c/em\u003e package, consistent with ASVCP recommendations.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e Because the reference sample size comprised 78 unique dogs (40\u0026thinsp;\u0026le;\u0026thinsp;n\u0026thinsp;\u0026lt;\u0026thinsp;120), we followed ASVCP\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e guidance to estimate the central 95% RI using a robust method with 90% confidence intervals (CIs) on the limits derived by bootstrap. This approach is preferred for n between 40 and 120 and does not require strict Gaussian distribution. Data were screened for outliers, which were only removed when there was a documented reason, such as a measurement or recording error, to ensure the integrity of the reference interval estimation.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eIn this study we had 78 unique, apparently healthy shelter dogs (Table\u0026nbsp;4.1). Humidity and ambient temperature during imaging spanned a range of 29%\u0026ndash;85% and 20 to 27\u0026deg;C respectively. After careful review, no outliers were identified for either ET or RT, supporting the reliability of the dataset for reference interval estimation. Violin-box plots were used to depict the distributions of ET and RT across age categories and sexes, which provide a visual comparison of temperature variation among these categorical factors (Fig.\u0026nbsp;4.1).\u003c/p\u003e \u003cp\u003e \u003cb\u003eReference interval analysis\u003c/b\u003e \u003c/p\u003e \u003cp\u003eWith a sample size in the 40\u0026ndash;120 range, we estimated the central 95% RI for ET using the robust method with bootstrap confidence intervals. The robust 95% RI was 35.0\u0026ndash;38.5\u0026deg;C. The 90% confidence interval (CI) for the lower limit was 34.7\u0026ndash;35.4\u0026deg;C, and the 90% CI for the upper limit was 38.2\u0026ndash;38.8\u0026deg;C. The 95% RI for RT was 37.5\u0026ndash;39.7\u0026deg;C. The 90% confidence interval (CI) for the lower bound was 37.3\u0026ndash;37.8\u0026deg;C, while the 90% CI for the upper bound was 39.5\u0026ndash;39.9\u0026deg;C (Fig.\u0026nbsp;4.2 and 4.3).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eUsing one measurement per dog from a prospective, kennel-side dataset, we established a robust 95% RI for ET in apparently healthy shelter, reporting the limits together with their confidence intervals gives a clear, repeatable standard for future studies. Thermal imaging captures radiative heat from superficial tissues. Measured ET reflects the interplay of local perfusion, tear-film evaporation, and heat exchange with the environment.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e The ocular surface and medial canthus are richly vascularized and responsive to autonomic tone, making them attractive windows for thermal screening; several veterinary and comparative studies have emphasized these regions as physiologically informative and practically accessible.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e In our study, all images were acquired at a standardized distance following device warm-up and with environmental parameters recorded, consistent with published best-practice recommendations for veterinary thermography.\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eExperimental and field data indicate that ET is linearly associated with RT, rising with activity level or fever.\u003csup\u003e\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e As a result, site-specific intervals are appropriate and should not be interchanged with rectal RIs. Rectal thermometry is the clinical reference method for assessing body temperature in dogs and its intervals are commonly used as the physiological benchmark when evaluating alternative thermometry approaches. Previous reports indicate that RT in healthy dogs typically fall between approximately 37.9\u0026deg;C and 39.9\u0026deg;C.\u003csup\u003e22\u003c/sup\u003e However, the methodology used to define this range is not described, and it is unclear whether it reflects a statistically derived reference interval or an observational estimate. In a recent data-driven analysis of adult dogs presenting for care, the mean RT was ~\u0026thinsp;38.6\u0026deg;C and the 95% RI was 37.7\u0026ndash;39.5\u0026deg;C.\u003csup\u003e4\u003c/sup\u003e In our study population, which included both adult dogs and puppies, RT measured in the same animals used for ET assessment had a reference interval of 37.5\u0026ndash;39.7\u0026deg;C, using robust method. The difference in the range could be due to age or environment. The close agreement between our findings and previously published adult dog intervals suggests that the dogs in our study were physiologically comparable to typical populations, supporting the validity of our ET reference intervals in this cohort. The RT interval estimated in this study was derived from measurements collected under routine shelter conditions. Establishing reference limits under these real-world conditions is valuable because factors such as mild excitement, recent movement, or kennel activity are unavoidable in municipal shelter environments. Another consideration when interpreting RT intervals is the influence of demographic and environmental variability within shelter populations. Dogs entering municipal shelters can vary widely in age, breed, body condition, and recent activity prior to intake. These factors introduce modest variability in measured temperatures, but that provides a robust estimate of RI for generalizable to all apparently healthy dogs. The statistical approach used in this study is designed to accommodate such heterogeneity while still producing reliable interval estimates for moderate sample sizes. As a result, the RT limits reported here may be particularly relevant for operational shelter medicine, where measurements must be interpreted across diverse dog populations rather than narrowly controlled experimental groups. In addition, the use of the same cohort of dogs to estimate both ET and RT intervals provides an internally consistent comparison between surface-based and core temperature measurements. The reported RT RI is greater than our estimated ET RI (35.0-38.5\u0026deg;C), as expected for a surface window subject to evaporative cooling and heat loss.\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e In contrast, the rectum is an internal site, protected by surrounding tissues, which helps maintain a more stable core temperature largely independent of surface heat exchange or evaporative cooling. In human and veterinary thermometry, similar relationships hold for axillary or tympanic sites versus core reference methods, reinforcing the interpretive principle that the normal range depends on the measurement site and acquisition protocol.\u003csup\u003e\u003cspan additionalcitationids=\"CR26 CR27 CR28 CR29 CR30 CR31\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eNoncontact imaging minimizes handling, preserves biosecurity, and is suitable for dogs that are reactive or difficult to restrain, and has practical advantages in municipal shelters. Values within the interval provide reassurance in routine checks; values near or outside the limits flag dogs for follow-up, for example, repeat measurement or confirmatory rectal thermometry. This integrated approach is consistent with the broader shelter-medicine literature that excitement and stress can transiently influence ET and short, calm imaging procedures help contain that variability.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e The present interval therefore functions best as a screening aid that complements, rather than replaces, targeted clinical examination.\u003c/p\u003e \u003cp\u003eThis study provides a reference range for ET in dogs under shelter kennel conditions. When used for screening, it should be interpreted with care due to some limitations. Environmental conditions, recent activity, and minor handling stress could affect ET. Therefore, this reference range should be used carefully when applied outside similar shelter settings or in dogs with different physiological or environmental conditions.\u003c/p\u003e \u003cp\u003eIn addition, while this reference interval defines a normal range for ET under kennel conditions, its ability to detect clinically meaningful changes has not been tested. Determining whether values outside this range reliably indicate fever or other abnormalities will require further studies to determine diagnostic performance. While we did not perform specialized diagnostic testing or detailed ophthalmic exams, our screening process was designed to mirror the actual constraints of veterinary practice. The goal was to establish a normal temperature range using a simplified and realistic protocol that can be reliably performed. This approach ensures that the estimated reference intervals are applicable to real world conditions.\u003c/p\u003e \u003cp\u003eIn summary, this study reports a robust, reference interval for ET and RT in shelter dogs measured under real-world conditions. The interval\u0026rsquo;s placement relative to rectal norms is consistent with established thermometry principles. By coupling biologically informed acquisition with best-practice RI estimation, these results offer a practical, evidence-based tool for everyday decision-making in shelter medicine.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDisclosures\u003c/h2\u003e \u003cp\u003eThe authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by funding from the United States Department of Agriculture Agricultural Research Service (USDA ARS) grant no. 58-6064-3-017. The opinions, findings, and conclusions expressed in this study are those of the authors and do not necessarily reflect the views of the USDA.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003e The authors would like to thank Dr. Jingyi Shi, Dr. W. Isaac Jumper and Dr. Guiming Wang for their valuable guidance and service as members of the doctoral committee during the development of this research.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eOzarda Y (2016) Reference intervals: current status, recent developments and future considerations. 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Vet World 15(5):1314\u0026ndash;1322. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.14202/vetworld.2022.1314-1322\u003c/span\u003e\u003cspan address=\"10.14202/vetworld.2022.1314-1322\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrinnel H, Cabanac M (1989) Tympanic temperature is a core temperature in humans. J Therm Biol 14(1):47\u0026ndash;53. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/0306-4565(89)90029-6\u003c/span\u003e\u003cspan address=\"10.1016/0306-4565(89)90029-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTravain T, Colombo ES, Heinzl E, Bellucci D, Prato Previde E, Valsecchi P (2015) Hot dogs: Thermography in the assessment of stress in dogs (\u003cem\u003eCanis familiaris\u003c/em\u003e)\u0026mdash;A pilot study. J Veterinary Behav 10(1):17\u0026ndash;23. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jveb.2014.11.003\u003c/span\u003e\u003cspan address=\"10.1016/j.jveb.2014.11.003\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1\u003cstrong\u003e\u0026mdash;\u003c/strong\u003eDemographic characteristics of the reference sample population.\u003c/p\u003e\n\u003ctable\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eUnique dogs\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePuppy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAdult\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eSex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\"\u003e\n \u003cp\u003eSize\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSmall\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eLarge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\"\u003e\n \u003cp\u003eCoat length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eShort\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eLong\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThis table presents the frequency distribution of demographic characteristics for the apparently healthy shelter dogs (n = 78) that comprised the reference sample group. Data include age, sex, size, and coat length. This population served as the basis for determining the reference interval for eye temperature and rectal temperature.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[{"identity":"c80b5753-3faa-41df-9c80-d566e19909cc","identifier":"10.13039/100000199","name":"U.S. Department of Agriculture","awardNumber":"58-6064-3-017","order_by":0}],"hasAdminPriorityOnWorkflow":true,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Mississippi State University","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":"Canine, infrared thermography, eye temperature, rectal temperature, reference interval, shelter medicine.","lastPublishedDoi":"10.21203/rs.3.rs-9372827/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9372827/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective.\u003c/h2\u003e \u003cp\u003eTo estimate a reference interval (RI) for eye temperature (ET) in apparently healthy shelter dogs using a robust method suitable for moderate sample sizes, and to provide a comparative reference interval for rectal temperature (RT).\u003c/p\u003e\u003ch2\u003eMethods.\u003c/h2\u003e \u003cp\u003eThis cross-sectional study analyzed ET measurements from a field dataset collected in a municipal shelter. The study population consisted of 78 apparently healthy dogs. ET was obtained with a handheld thermal camera under standardized procedures. Rectal temperatures were obtained from the same dogs using a digital rectal thermometer. The central 95% RI was estimated using a robust statistical method with bootstrap-derived 90% confidence intervals (CIs) for the limits, an approach recommended for datasets with 40\u0026thinsp;\u0026le;\u0026thinsp;n\u0026thinsp;\u0026lt;\u0026thinsp;120 observations.\u003c/p\u003e\u003ch2\u003eResults.\u003c/h2\u003e \u003cp\u003eThe estimated 95% RI for ET was 35.0-38.5\u0026deg;C with 90% CIs of 34.7\u0026ndash;35.4\u0026deg;C (lower limit) and 38.2\u0026ndash;38.8\u0026deg;C (upper limit). The 95% RI for RT was 37.5\u0026ndash;39.7\u0026deg;C with 90% CIs of 37.3\u0026ndash;37.8\u0026deg;C (lower limit) and 39.5\u0026ndash;39.9\u0026deg;C (upper limit).\u003c/p\u003e\u003ch2\u003eConclusions.\u003c/h2\u003e \u003cp\u003eThese findings provide RIs for ET and RT in apparently healthy shelter dogs. Values approaching or exceeding these limits may warrant additional clinical evaluation. The intervals may serve as an initial benchmark for temperature assessment in similar populations.\u003c/p\u003e\u003ch2\u003eClinical Relevance\u003c/h2\u003e \u003cp\u003e. Population-based RIs for eye and rectal temperatures of dogs are needed to assist veterinarians and shelter personnel in interpreting ET and RT measurements and identifying dogs that might require further clinical examination. Ocular thermography may offer a practical screening tool for body temperature assessment in shelter settings where rapid, low-stress evaluation is desirable.\u003c/p\u003e","manuscriptTitle":"Reference intervals for eye temperature measured by infrared thermography and rectal temperature in dogs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-14 19:10:23","doi":"10.21203/rs.3.rs-9372827/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":"77a6fdd2-a984-408d-a3c3-9118dcc79c54","owner":[],"postedDate":"April 14th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":66046250,"name":"Veterinary Epidemiology"}],"tags":[],"updatedAt":"2026-04-14T19:10:23+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-14 19:10:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9372827","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9372827","identity":"rs-9372827","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}