Using Canine Olfaction to Detect Bovine Respiratory Disease: A Pilot Study

Abstract

Bovine respiratory disease (BRD) is the leading cause of morbidity and mortality in feedlot cattle and is a major welfare and economic concern. Identification of BRD-affected cattle using clinical illness scores is problematic, and speed and cost constraints limit the feasibility of many diagnostic approaches. Dogs can rapidly identify humans and animals affected by a variety of diseases based on scent. Canines' olfactory systems can distinguish between patterns of volatile organic compounds produced by diseased and healthy tissue. In this pilot study, two dogs (“Runnels” and “Cheaps”) were trained for 7 months to discriminate between nasal swabs from cattle that developed signs of BRD within 20 days of feedlot arrival and swabs from cattle that did not develop BRD signs within 3 months at the feedlot. Nasal swabs were collected during cattle processing upon arrival to the feedlot and were stored at −80°C. Dogs were presented with sets of one positive and two negative samples and were trained using positive reinforcement to hold their noses over the positive sample. The dogs performed moderately well in the final stage of training, with accuracy for Runnels of 0.817 and Cheaps of 0.647, both greater than the 0.333 expected by chance. During a double-blind detection test, dogs evaluated 123 unique and unfamiliar samples that were presented as 41 sets (3 samples per set), with both the dog handler and data recorder blinded to the positive sample location. Each dog was tested twice on each set of samples. Detection test accuracy was slightly better than chance for Cheaps at 0.451 (95% CI: 0.344–0.559) and was no better than chance for Runnels at 0.390 (95% CI: 0.285–0.496. Overall accuracy was 0.421 (95% CI: 0.345–0.496). When dogs' consensus response on each sample set was considered, accuracy was 0.537 (95% CI: 0.384–0.689). Detection accuracy also varied by sample lot. While dogs showed some ability to discriminate between BRD-affected and healthy cattle using nasal swabs, the complexity of this task suggests that more testing is needed before determining whether dogs could be effective as a screening method for BRD.

Dogs' ability to detect an inflammatory immune response in cattle via olfaction

“…Two dogs, Runnels and Cheaps, were included in a prior study of dogs' ability to detect BRD ( 10 ). At the time of the current study, Runnels was 8 years old, and had resided at the kennel facility for 7 years, and Cheaps was 6 years old, and had resided at the kennel facility for 5 years.…”

“…Dog training and testing was conducted in the same facility as a previous study ( 10 ). The training room was 3.66 m × 4.27 m and was maintained between 16 and 27°C.…”

“…The basis for olfactory detection of disease is that there are differences in the pattern of volatile organic compounds (VOCs) produced by sick compared to healthy animals. In a prior study, an attempt was made to train two dogs to detect cattle at risk of developing bovine respiratory disease ( 10 ). Dogs were trained using positive reinforcement to produce a nose hold alert on a station containing a nasal swab from a bull or steer that was subsequently treated multiple times for BRD or died, while alerts on stations containing a sample from an animal that was not subsequently treated for BRD were not reinforced.…”

“…Samples were collected as cattle entered the feedlot, and BRD status was determined based on whether the animal was treated for BRD within 20 days of arrival. Consequentially, samples designated positive may have been taken prior to initiation of an inflammatory response, and samples designated negative could include asymptomatic BRD-affected cattle, resulting in ineffective training ( 10 ). Lack of consistency in sample handling have been shown to affect disease detection learning in canines ( 11 ).…”

“…Sample type is also associated with differences in detection success; however, the use of nasal mucus or saliva samples for canine medical detection is relatively rare ( 6 ). Another factor that may have impaired dogs' success in the previous pilot study of canines' ability to detect BRD was potential sample contamination with dirt or other substances (e.g., pollen, seasonal differences in feedstuffs) present in cattle's noses ( 10 ). To evaluate the effects of sample type on BRD detection success, this study will include both nasal swabs and saliva samples as detection targets.…”