You want to keep your dog healthy and fit for duty, but sometimes he is a little under the weather. Stress of travel, hard work in unfamiliar places, and disruption of routine can all lead to some less-than-desirable consequences such as diarrhea or gastric ulceration. One of the most common medications we prescribe to dogs for diarrhea and other mild gastrointestinal signs is an antibiotic and antiprotazoal medication called metronidazole. It's generally safe and effective and not very expensive, as far as medications go, so it's an ideal drug for treating these conditions...most of the time.
Dr. Eileen Jenkins, a veterinarian with the U.S. Army Veterinary Corps and her colleagues at Auburn University conducted a study a few years ago that found that about 50% of the explosive detection dogs in their study, when administered metronidazole at the high dose range, actually had decreased ability in detecting target odors for as much as ten days after getting the medication. You can read a summary of that study here: Metronidazole Study
This last week, Dr. Jenkins and her colleagues Mallory DeChant and Erin Perry, PhD. published an excellent review of medications, physical stressors, and nutrition on olfactory ability and GI health in dogs who use their sense of smell to save human lives. You can read that review here: When the Nose Doesn't Know: Olfaction Review. Very little is actually known about how medications and other health management practices affect scent detection ability in dogs. Over time, we'll discuss the various topics they reviewed in more detail and how that could affect your dog.
So what about metronidazole? Should you refuse this medication for your detection dog if your veterinarian recommends it? Keep in mind that while Dr. Jenkins' excellent study showed decreased detection ability in half of the dogs tested, more study is needed to understand all of the effects of this drug on scent detection. Many cases of diarrhea are self-limiting and don't require antibiotics like metronidazole to control, as long as they receive other appropriate supportive care, or there are other options for antibiotic treatment. Sometimes, however, your dog will be sick enough with a specific problem that metronidazole is the very best medication to treat his illness. So far we have no evidence to suggest decrease or loss of scent detection ability is permanent, so if your dog does have to receive metronidazole for a health issue, just be aware that his scent detection ability may not be 100% for a week or two, so test his abilities before putting him fully back to work. Your veterinarian can serve you and your dog best if they are up-to-date on research and other information regarding your dog's specific occupational health concerns. Feel free to provide these links to them so you can both make the best informed treatment decisions regarding your dog's healthcare needs.
--Janice L. Baker, DVM, MS, DACVPM