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Home / Equine Research Bank / Equine Vet J / Risk factors for exertional heat illness in Thoroughbred rac...
Equine veterinary journal2019; 52(3); 364-368; doi: 10.1111/evj.13179

Risk factors for exertional heat illness in Thoroughbred racehorses in flat races in Japan (2005-2016).

Abstract: Exertional heat illness (EHI) is recognised in horses, but few reports have investigated its risk factors. Objective: To identify risk factors for EHI in racehorses participating in flat races in Japan. Methods: Descriptive epidemiology and retrospective unmatched case-control study. Methods: Between 2005 and 2016, veterinary records of horses diagnosed with EHI after flat races were reviewed retrospectively and data of the months from April to September were used for a case-control study. For each case, three control horses were randomly selected from starts between April and September. Race records of horses and estimated wet-bulb globe temperature (WBGT) indexes at the local meteorological observatory closest to the racecourse were investigated. To identify risk factors for EHI, univariable and multivariable logistic regression analysis was used. Results: Of 194 cases during the study period, 188 cases occurred between April and September. The highest incidence risk was in July (1.1 cases per 1000 starts, 95% confidence interval 0.84-1.45). In the final multivariable model, WBGT index, sex, race distance, age and bodyweight were associated with EHI. When WBGT index exceeded 28°C, the risk of EHI was considerably higher than <20°C (OR 28.5, 14.2-62.4, P<0.001). Compared with uncastrated males, geldings (OR 4.9, 1.8-13.3, p = 0.002) and females (OR 2.4, 1.5-3.7, P<0.001) were at high risk of EHI (P<0.01). Furthermore, races of >1600 m (OR 1.8, 1.2-2.8, P = 0.002), 4-year-old (OR 3.5, 1.6-7.9, P = 0.002) and ≥5-year-old (OR 3.9, 1.8-9.2, P = 0.001) horses and horses with low bodyweight (OR per 20 kg, 0.8, 0.7-1.0, P = 0.02) were associated with increased risk of EHI. Conclusions: The median straight-line distance between the racecourse and the local meteorological observatory was 14.2 km (range, 1.1-28.3 km). There was a lack of objective criteria of EHI due to the retrospective nature of the study. Conclusions: We identified specific risk factors for EHI in racehorses. These results may be useful to the equine industry for reducing EHI occurrence in racehorses.
© 2019 EVJ Ltd.
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Publication Date: 2019-10-06 PubMed ID: 31505059DOI: 10.1111/evj.13179Google Scholar: Lookup
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  • Journal Article

Summary

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The research article investigates potential risk factors for exertional heat illness (EHI) in racehorses during flat races in Japan, identifying factors such as wet-bulb globe temperature (WBGT) index, sex, race distance, age, and bodyweight.

Methodology

  • The researchers conducted a descriptive epidemiology and retrospective unmatched case-control study by reviewing veterinary records of horses diagnosed with EHI after flat races in Japan between 2005 and 2016.
  • They specifically used data from the months between April and September and for each case of EHI, three control horses were randomly selected from the same period.
  • Race records of the horses and the estimated WBGT indexes at the local meteorological observatory closest to the racecourse were also taken into consideration.
  • To identify the risk factors, both univariable and multivariable logistic regression analyses were performed.

Results

  • The study found 194 cases of EHI during the study period, of which 188 occurred between April and September.
  • The highest incidence risk was in July and significant risk factors for EHI included the WBGT index, sex of the horse, race distance, age of the horse, and its bodyweight.
  • The risk of EHI considerably increased when the WBGT index exceeded 28°C.
  • Geldings and female horses had a higher risk of EHI as compared to uncastrated males.
  • Horses participating in races over 1600m, horses aged four years and older, and horses with lower bodyweights were also associated with an increased risk of EHI.

Conclusions

  • Due to the retrospective nature of the study, there was a lack of objective criteria of EHI, however, the median straight-line distance between the racecourse and the local meteorological observatory was considered and recorded as 14.2 km.
  • The study succeeded in identifying specific risk factors for EHI in racehorses, highlighting important insight for the equine industry to implement necessary precautions and potentially reduce EHI occurrences in racehorses.

Cite This Article

APA
Takahashi Y, Takahashi T. (2019). Risk factors for exertional heat illness in Thoroughbred racehorses in flat races in Japan (2005-2016). Equine Vet J, 52(3), 364-368. https://doi.org/10.1111/evj.13179

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 52
Issue: 3
Pages: 364-368

Researcher Affiliations

Takahashi, Y
  • Sports Science Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.
Takahashi, T
  • Sports Science Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan.

MeSH Terms

  • Animals
  • Case-Control Studies
  • Female
  • Heat-Shock Response
  • Horses
  • Hot Temperature
  • Japan
  • Male
  • Retrospective Studies
  • Risk Factors

Grant Funding

  • Japan Racing Association

References

This article includes 35 references
  1. Hodgson DR, Davis RE, McConaghy FF. Thermoregulation in the horse in response to exercise.. Br. Vet. J. 150, 219-235.
  2. Takahashi T. The effect of age on the racing speed of Thoroughbred racehorses.. J. Equine Sci. 26, 43-48.
  3. Spence AJ, Thurman AS, Maher MJ, Wilson AM. Speed, pacing strategy and aerodynamic drafting in Thoroughbred horse racing.. Biol. Lett. 8, 678-681.
  4. Hodgson DR. Thermoregulation.. In: The Athletic Horse; Principles and Practice of Equine Sports Medicine, 2nd edn., Eds: D.R. Hodgson, K.H. McKeever and C.M. McGowan, Saunders-Elsevier, St Louis. pp 108-124.
  5. Brownlow MA, Dart AJ, Jeffcott LB. Exertional heat illness: a review of the syndrome affecting racing Thoroughbreds in hot and humid climates.. Aust. Vet. J. 94, 240-247.
  6. Kerr ZY, Casa DJ, Marshall SW, Comstock D. Epidemiology of exertional heat illness among U.S. high school athletes.. Am. J. Prev. Med. 44, 8-14.
  7. Cooper ER, Ferrara MS, Casa DJ, Powell JW, Broglio SP, Resch JE, Courson RW. Exertional heat illness in American football players: when is the risk greatest?. J. Athl. Train. 51, 593-600.
  8. Armstrong LE, Casa DJ, Millard-Stafford M, Moran DS, Pyne SW, Roberts WO. American College of Sports Medicine position stand. Exertional heat illness during training and competition.. Med. Sci. Sports Exerc. 39, 556-572.
  9. Casa DJ, DeMartini JK, Bergeron MF, Csillan D, Eichner ER, Lopez RM, Ferrara MS, Miller KC, O’Connor F, Sawka MN, Yeargin SW. National Athletic Trainers' Association position statement: exertional heat illnesses.. J. Athl. Train. 50, 986-1000.
  10. American College of Sports Medicine. Position stand on the prevention of thermal injuries during distance running.. Med. Sci. Sports Exerc. 19, 529-533.
  11. Schroter RC, Marlin DJ, Jeffcott LB. Use of the Wet Bulb Globe Temperature (WBGT) index to quantify environmental heat loads during three-day-event competitions.. Equine Vet. J. 28, Suppl. 22, 3-6.
  12. Racing New South Wales. Racing in hot weather policy.. Available at: http://racingnsw-prod-alb-v00-1971180292.ap-southeast-2.elb.amazonaws.com/wp-content/uploads/2017/09/racing-in-hot-weather.pdf. Accessed 17 October 2018.
  13. Jeffcott LB, Kohn CW. Contributions of equine exercise physiology research to the success of the 1996 Equestrian Olympic Games: a review.. Equine Vet. J. 31, Suppl. 30, 347-355.
  14. Kazman JB, Purvis DL, Heled Y, Lisman P, Atias D, Arsdale SV, Deuster PA. Women and exertional heat illness: identification of gender specific risk factors.. US. Army Med. Dep. J. 58-66.
  15. MacDonald DM, Wheeler DP, Guthrie AJ, Kok C, Pilgrim T. “Post race distress syndrome” in Thoroughbred racing in South Africa.. In: Proceedings of the 17th International Conference of Racing Analysts and Vetrinarians. Eds: E. Houghton, F. Ipek Keskin, J.F. Wade and N. Yazicioglu, R&W Communications, Newmarket. pp 310-314.
  16. Hosmer DW Jr, Lameshow S, Sturdivant RX. Interpretation of the fitted logistic regression model.. In: Applied Logistic Regression, 3rd edn., Willey, New York. pp 49-88.
  17. Ono M, Tonouchi M. Estimation of wet-bulb globe temperature using generally measured meteorological indices.. Jpn. J. Biometeorol. 50, 147-157.
  18. Kohn CW, Hinchcliff KW, McKeever KH. Evaluation of washing with cold water to facilitate heat dissipation in horses exercised in hot, humid conditions.. Am. J. Vet. Res. 60, 299-305.
  19. Geor RJ, McCutcheon LJ, Ecker GL, Lindinger MI. Thermal and cardiorespiratory responses of horses to submaximal exercise under hot and humid conditions.. Equine Vet. J. 27, Suppl. 20, 125-132.
  20. Bittel J, Henane R. Comparison of thermal exchanges in men and women under neutral and hot conditions.. J. Physiol. 250, 475-489.
  21. Inoue Y, Tanaka Y, Omori K, Kuwahara T, Ogura Y, Ueda H. Sex-and menstrual cycle-related differences in sweating and cutaneous blood flow in response to passive heat exposure.. Eur. J. Appl. Physiol. 94, 323-332.
  22. Garcia CK, Mattingly AJ, Robinson GP, Laitano O, King MA, Dineen SM, Leon LR, Clanton TL. Sex-dependent responses to exertional heat stroke in mice.. J. Appl. Physiol. (1985) 125, 841-849.
  23. Morley PS, Bromberek JL, Saulez MN, Hinchcliff KW, Guthrie AJ. Exercise-induced pulmonary haemorrhage impairs racing performance in Thoroughbred racehorses.. Equine Vet. J. 47, 358-365.
  24. Mukai K, Hiraga A, Takahashi T, Ohmura H, Jones JH. Effects of three warm-up regimens of equal distance on VO2 kinetics during supramaximal exercise in Thoroughbred horses.. Equine Vet. J. 42, Suppl. 38, 33-39.
  25. Hodgson DR, McCutcheon LJ, Byrd SK, Brown WS, Bayly WM, Brengelmann GL, Gollnick PD. Dissipation of metabolic heat in the horse during exercise.. J. Appl. Physiol. (1985) 74, 1161-1170.
  26. McKeever KH, Eaton TL, Geiser S, Kearns CF, Lehnhard RA. Age related decreases in thermoregulation and cardiovascular function in horses.. Equine Vet. J. 42, Suppl. 38, 220-227.
  27. McCutcheon LJ, Geor RJ, Ecker GL, Lindinger ML. Equine sweating responses to submaximal exercise during 21 days of heat acclimation.. J. Appl. Physiol. 87, 1843-1851.
  28. Geor RJ, McCutcheon LJ, Lindinger MI. Adaptations to daily exercise in hot and humid ambient conditions in trained Thoroughbred horses.. Equine Vet. J. 28, Suppl. 22, 63-68.
  29. Lindinger MI, McCutcheoun LJ, Ecker GL, Geor RJ. Heat acclimation improves regulation of plasma volume and plasma Na(+) content during exercise in horses.. J. Appl. Physiol. (1985) 88, 1006-1013.
  30. Hansen PJ. Effects of coat colour on physiological responses to solar radiation in Holsteins.. Vet. Rec. 127, 333-334.
  31. McNicholl J, Howarth GS, Hazel SJ. Influence of the environment on body temperature of racing greyhounds.. Front. Vet. Sci. 3, 53.
  32. Carter AJ, Hall EJ. Investigating factors affecting the body temperature of dogs competing in cross country (canicross) races in the UK.. J. Thermal. Biol. 72, 33-38.
  33. Armson D, Stringer P, Ennos AR. The effect of tree shade and grass on surface and globe temperatures in an urban area.. Urban For. Urban Green. 11, 245-255.
  34. Equestrian Australia. Hot weather policy.. Available at: http://www.equestrian.org.au/policies. Accessed 17 October 2018.
  35. Royston P, Altman DG, Sauerbrei W. Dichotomizing continuous predictors in multiple regression: a bad idea.. Stat. Med. 25, 127-141.

Citations

This article has been cited 11 times.
  1. Ohmura H, Ebisuda Y, Takahashi Y, Mukai K. Effects of pre-exercise cooling in hot environments on performance and physiological responses in Thoroughbred horses. J Equine Sci 2025;36(1):19-23.
    doi: 10.1294/jes.36.19pubmed: 40115731google scholar: lookup
  2. Ebisuda Y, Mukai K, Takahashi Y, Yoshida T, Matsuhashi T, Kawano A, Miyata H, Kuwahara M, Ohmura H. Heat acclimation improves exercise performance in hot conditions and increases heat shock protein 70 and 90 of skeletal muscles in Thoroughbred horses. Physiol Rep 2024 May;12(10):e16083.
    doi: 10.14814/phy2.16083pubmed: 38789393google scholar: lookup
  3. Munsters C, Siegers E, Sloet van Oldruitenborgh-Oosterbaan M. Effect of a 14-Day Period of Heat Acclimation on Horses Using Heated Indoor Arenas in Preparation for Tokyo Olympic Games. Animals (Basel) 2024 Feb 6;14(4).
    doi: 10.3390/ani14040546pubmed: 38396514google scholar: lookup
  4. Verdegaal EJMM, Howarth GS, McWhorter TJ, Delesalle CJG. Thermoregulation during Field Exercise in Horses Using Skin Temperature Monitoring. Animals (Basel) 2023 Dec 30;14(1).
    doi: 10.3390/ani14010136pubmed: 38200867google scholar: lookup
  5. Kang H, Zsoldos RR, Sole-Guitart A, Narayan E, Cawdell-Smith AJ, Gaughan JB. Heat stress in horses: a literature review. Int J Biometeorol 2023 Jun;67(6):957-973.
    doi: 10.1007/s00484-023-02467-7pubmed: 37060454google scholar: lookup
  6. Trigg LE, Lyons S, Mullan S. Risk factors for, and prediction of, exertional heat illness in Thoroughbred racehorses at British racecourses. Sci Rep 2023 Mar 14;13(1):3063.
    doi: 10.1038/s41598-023-27892-xpubmed: 36918525google scholar: lookup
  7. Verdegaal EJMM, Howarth GS, McWhorter TJ, Delesalle CJG. Is Continuous Monitoring of Skin Surface Temperature a Reliable Proxy to Assess the Thermoregulatory Response in Endurance Horses During Field Exercise?. Front Vet Sci 2022;9:894146.
    doi: 10.3389/fvets.2022.894146pubmed: 35711810google scholar: lookup
  8. Kang H, Zsoldos RR, Skinner JE, Gaughan JB, Mellor VA, Sole-Guitart A. The Use of Percutaneous Thermal Sensing Microchips to Measure Body Temperature in Horses during and after Exercise Using Three Different Cool-Down Methods. Animals (Basel) 2022 May 14;12(10).
    doi: 10.3390/ani12101267pubmed: 35625113google scholar: lookup
  9. Wang M, Liu Y, Bi X, Ma H, Zeng G, Guo J, Guo M, Ling Y, Zhao C. Genome-Wide Detection of Copy Number Variants in Chinese Indigenous Horse Breeds and Verification of CNV-Overlapped Genes Related to Heat Adaptation of the Jinjiang Horse. Genes (Basel) 2022 Mar 28;13(4).
    doi: 10.3390/genes13040603pubmed: 35456409google scholar: lookup
  10. Verdegaal EJMM, Howarth GS, McWhorter TJ, Boshuizen B, Franklin SH, Vidal Moreno de Vega C, Jonas SE, Folwell LE, Delesalle CJG. Continuous Monitoring of the Thermoregulatory Response in Endurance Horses and Trotter Horses During Field Exercise: Baselining for Future Hot Weather Studies. Front Physiol 2021;12:708737.
    doi: 10.3389/fphys.2021.708737pubmed: 34512382google scholar: lookup
  11. Klous L, Siegers E, van den Broek J, Folkerts M, Gerrett N, van Oldruitenborgh-Oosterbaan MS, Munsters C. Effects of Pre-Cooling on Thermophysiological Responses in Elite Eventing Horses. Animals (Basel) 2020 Sep 16;10(9).
    doi: 10.3390/ani10091664pubmed: 32947831google scholar: lookup
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