Ask the Infectious Disease Expert

How Have Recent Equine Disease Outbreaks Affected Your Practice, and What Technological Advances are You Seeing to Help Keep Horses Safe?

C. Scott Bailey, DVM, MS, DACT

In 2021, as rotavirus B spread widely among foals in central Kentucky, we were severely affected. Without knowing the cause of diarrhea, I quickly realized that I needed a more effective monitoring tool than simply observing clinical signs like diarrhea, depression and failure to nurse. At the same time, the biosecurity challenges of having two people enter every stall and handle the foals multiple times a day for rectal temperature monitoring were significant. I realized this challenge would extend to other situations where limited handling time and personnel were preferable for biosecurity or safety reasons.

Beginning in January 2022, we started placing Bio-Thermo® temperature-sensing microchips at the time of the initial post-foaling examination.

We started out checking temps daily on those first foals and noted that some foals initially were reading higher than we expected, but quickly fell back into a more normal range. Mean temperatures measured with the Bio-Thermo microchip in foals rose from 101.2 ± 1.1° F at the time of microchip placement on the morning after foaling to 102.4 ± 0.57° F on day three. They then gradually declined over 14 days in healthy foals, with a consistent standard deviation of approximately 0.6° F. Based on these data, we have set cutoffs for further investigation at 100.5 to 103.5° F for neonatal foals and 99.0 to 102.5° F in foals older than 10 days. Foals with systemic disease were more likely to have high or low temperatures.

Subsequently, we compared microchip and rectal temperatures taken simultaneously in older foals and yearlings and found a remarkable degree of overlap (Figure 1). Minor variations in healthy animals didn’t affect our decision making. More importantly, we were pleased with the performance of microchips in detecting fevers in sick horses and got more confident using the scanners as a screening tool.

For a large farm like ours, the microchips allowed our farm staff to easily scan the temperatures of animals as they went out to pasture or target individual animals that appeared “off.” This method saved time and decreased the risk of injury to personnel, particularly when dealing with weaned foals and yearlings. I can see wider applications in other farms, training facilities and larger boarding stables to routinely screen animals’ health status. The scanners easily pair with software that allows dissemination of the data, so that a veterinarian or manager who is off-site could easily review and identify individual animals that may need further workup.

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Visit the Bio-Thermo Microchip web page to learn more or talk to your Merck Animal Health sales representative.

1. Kang H, Sole-Guitart A, Mellor VA, Gaughan JB, Zsoldos RR. The use of percutaneous thermal sensing microchips for non-invasive measurement of body temperature in foals during summer seasons in a subtropical region. Animal. 2022 Sep;16(9):100620. doi: 10.1016/j.animal.2022.100620. Epub 2022 Aug 19. PMID: 35994970.

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