Korrelation zwischen rektaler Temperaturmessung und Oberflächentemperaturmessung mittels Thermografiekamera bei Pferden – Potenzieller Nutzen für Schutzkonzepte bei Infektionskrankheiten
Correlation between rectal and surface temperature measurements in horses – investigating thermography for infection disease screening protocols
Lutz R, Monod A, Delalay G, Wampfler B, Fürst A, Montavon S
DOI: 10.21836/PEM20240301
Jahr: 2024
Volume: 40
Ausgabe: 3
Seiten: 204–212
Body temperature in the horse is a reference measurement that is considered to be an excellent health indicator. During the COVID-19 pandemic, the use of infrared thermal imaging for fever screening became widespread to detect changes in human body temperature. During the 2021 outbreak of EHV in southern Europe, quarantine and confinement were quickly imposed as the main control measures. This impacted equestrian sport for many months and caused relevant damage. To prevent repetition of these events, the equine sport sector introduced rules to monitor the temperature of the horses before, during and after competitions. The first objective of this study is to assess whether Infrared Thermography (IRT) measurement of either the anus or forehead surface temperature using a FLIR thermal imaging camera is an appropriate alternative to rectal measurements using a thermometer for determining body temperature in horses. The second objective is to assess the possibility of using IRT body temperature measurement on a large scale, for example in the case of an infectious disease epidemic such as EHV-1. 40 healthy geldings from the Swiss Armed Forces with a median age of 7.5 years (range: 4 to 17 years, SD 3.83 years) were used. The study was divided into three periods. The first was the pilot study with 13 horses during the summer. The second was during the winter with 16 horses and the third with 11 horses in early spring. 10 horses in the second study period and 4 horses in the third wore a blanket, while the other 26 horses did not. A conventional veterinary digital thermometer and the FLIR E86 thermal imaging camera were used. The anal IRT measurement was made at a distance of 10 cm centred on the middle of the anus. The forehead measurement was made on the midline between the eyes at distances of 20 and 30 cm. All measurements were taken three times a day (early morning, midday and late afternoon). The same location was used over all three testing periods. The median difference between measurements of rectal temperature and surface anal temperature was 0.9 °C (SD = 0.96 °C – p value: <2.2 ×10–16). There was a variation between summer and winter (p value: <2.2 ×10–16). The ambient temperature was an important parameter influencing the surface anal temperature in our data (p value = 6.34 ×10–29). The median difference between measurements of rectal temperature and surface forehead temperature was 15.2 °C (SD = 2.83) at 20 cm and 15.3 °C (SD = 2.84 °C) at 30 cm. Repeated measurements of the surface anal temperature with the FLIR showed that the method is reproducible, with only small differences between the measurements. Neither the surface temperature of the anus nor the forehead as measured with the FLIR allowed efficient prediction of equine rectal temperature. The precision of the methodology applied both to the anus and the forehead was too low to allow the effective implementation of this technology to evaluate equine body temperature. In addition, this method is also insufficiently accurate for measuring body temperatures on a large-scale during events with a large number of horses.