Use of thermographic images to detect external parasite load in cattle

The aim of this study was to compare standard visual methods with infrared thermography combined with a program that contrasted points in the image analysis for automatic counting of ectoparasites (ticks and horn flies) in cattle under pasture conditions. Twenty Holstein cows, 10 Devon cows and 10 Braford bulls were used. External parasites were visually counted and thermographic images taken with a FLIR® T300 camera. Images were processed in Quick report® and parasites also were counted using ImageJ®. Ectoparasites were cooler than the body of the animals in the thermographic images and therefore were easily highlighted by Quick report® program. In the case of ticks, they were especially visible when gravid female ticks were engorged but difficult to observe when hair was long. Horn flies stood out perfectly on thermographic images and were seen down to 3 mm in length. The correlation between visual and thermographic combined with a program counts method was 0.82 for horn flies. The correlation between these methods was 0.32 for the ticks on the lateral of the animal and 0.84 for the ticks on the distal of the animal. The regression between visual and thermographic measures for horn fly was highly significant for the three breeds. The use of thermographic images combined with a program for automatic counting was a useful tool and more accurate than the standard visual methods for counting external ectoparsites in cattle.