Understanding internal parasite diagnostics

In this interview with dvm360, Susan E. Little, DVM, PhD, DACVM, Krull-Ewing professor of parasitology at the Center for Veterinary Health Sciences at Oklahoma State University in Stillwater, talks about different internal parasites of dogs. Specifically, she discusses different diagnostic tests available, and what parasites certain tests are better at identifying.

Below is a partial transcript which has been lightly edited for clarity

Susan E. Little, DVM, PhD, DACVM: ‘How common are the different…internal parasites and dogs?’ is a really great question because we don't always have good data to answer that question, it depends on the quality of the diagnostic tests that we have at our disposal, right? And so there can be challenges in diagnosing particularly tapeworms, heartworm and whipworm. Hookworms and roundworms absolutely matter, as does Giardia and coccidia, but…the diagnostic tests are better at identifying those infections than...heartworms. And we have good diagnostic tests for all parasites, but they just all have limitations.

So, tapeworms is probably the most challenging internal parasite to diagnose with fecal flotation alone, and so that's what we're used to doing in practice is the fecal flotation, you know, direct microscopic examination of a preparation. And that works for hookworms and roundworms. It's a little more challenging for whipworms. For tapeworms, it's all but useless. We have sensitivity values of like maybe less than 50% for Taenia tapeworms and for something like Dipylidium flea tapeworm…the odds that you actually detect an infection with a flea tapeworm in a dog by fecal flotation alone is less than 5%. So they're just not helpful, and that's one of the reasons that antigen tests have been developed for flea tapeworms. So we've got better strategies now to find those infections and we're certainly finding them. We're seeing that we were overlooking them before, which means that the dog comes into the veterinary practice with a tapeworm infection and goes back home with a tapeworm infection if the right diagnostic test isn't done, or if it’ not anticipated, that that infection is present.