Parasites in wildlife don't just pose a risk to their wild hosts - they can also spread to domestic animals and humans, making safe and reliable ways to screen for these pests critical to promote better health for all.
Justin Brown, associate teaching professor of veterinary and biomedical sciences in Penn State's College of Agricultural Sciences, said one such parasite is Echinococcus. It is a type of tapeworm that often causes no clinical signs in wild and domestic dogs but can lead to severe effects in humans.
Brown - along with a team including undergraduate students in the college and researchers from other institutions - performed a series of studies examining the prevalence of the tapeworm in wild canids such as coyotes and foxes, along with the best ways to detect it. They published their findings in the journal One Health.
"Echinococcus can pass from wild or pet dogs to humans, where it can cause infections, typically in the lungs or liver, that are complicated to diagnose or treat," Brown said. "Although the prevalence of infection in wild canids appears to be low in Pennsylvania, we think it is important that veterinarians, pet owners, and hunters and trappers know that this parasite is present in the commonwealth."
The researchers teamed up with Antech Diagnostics, a company specializing in diagnostic tools for animals. Antech had developed a test called the KeyScreen GI Parasite PCR, which tests for 20 different important gastrointestinal parasites of dogs and cats, some of which are zoonotic - or transmissible to humans.
In domestic dogs and cats, the KeyScreen GI Parasite PCR has been shown to be more sensitive than traditional ways to test for gastrointestinal parasites in fecal samples. Consequently, Brown and his team were interested in using it to compare parasite data among wild canids, pet dogs and hunting dogs in Pennsylvania.
They theorized that the results would include a spectrum of disease risk, with higher parasite levels in wildlife and lower levels in domestic dogs, and that they could then characterize the parasites in each of these categories of canids.
For the study, the researchers compared KeyScreen GI Parasite PCR data processed from samples they collected from 26,981 pet dogs, 59 hunting dogs and 262 wild canids from Pennsylvania to determine parasite diversity and prevalence.
As they expected, the researchers found higher levels of multiple parasites in wild canids than in pet dogs, as well as higher levels of parasites such as hookworms and whipworms in hunting dogs compared to pet dogs. But in the wild canids, they also found evidence of echinococcus, which was only recently identified in Pennsylvania.
"Diagnostically, Echinococcus is tricky, because traditional diagnostic approaches may not identify infections," Brown said. "Echinococcus eggs in feces look indistinguishable from other common tapeworms. In addition, Echinococcus is very small - 2 to 7 millimeters - and easy to miss with the naked eye. But when we started using this PCR test, which is very sensitive and identifies parasites by analyzing DNA, we started detecting Echinococcus more frequently."
Noelle Kuhn, a Penn State alum who is now attending veterinary school at Michigan State University, became involved in the research as a Shreyer Honors College scholar majoring in veterinary and biomedical sciences in the College of Agricultural Sciences.
"When I started to think about my thesis, I was interested in exploring wildlife health because I was also pursuing a wildlife and fisheries science minor," Kuhn said. "It was very coincidental that Dr. Brown was starting this project and I could hop on board."
For her project, Kuhn ran a study comparing the traditional test for gastrointestinal parasites - called a fecal float, the test involves placing fecal samples in liquid and examining for the presence of parasite eggs - with the KeyScreen GI Parasite PCR test in wild canids. She performed the fecal floats, sent additional samples to Antech Diagnostics for PCR testing and performed the statistical analysis before analyzing the results.
She found that the PCR test was indeed more sensitive in diagnosing the 20 parasites included on its panel. Additionally, it was able to distinguish between parasite eggs that visually look identical, making them typically hard to distinguish from each other.
However, Brown said there are also limitations to the PCR test, particularly for wildlife that harbor a wide diversity of parasites. Although the KeyScreen GI Parasite PCR can detect different important gastrointestinal parasites, there are still other parasites not included that could infect wildlife.
"Noelle's research helped highlight the value of this new diagnostic tool for surveying wildlife for these gastrointestinal parasites, but also emphasized that the best surveillance approach for wildlife likely involves a combination of contemporary and traditional diagnostic approaches," he said.
Kuhn said the experience of running the project all the way through from the beginning to the end was rewarding, especially as she heads into the next step of her academic career.
"Even as I move forward with becoming a small animal vet, the experience taught me that there are so many diseases - particularly infectious diseases - that are connected to wildlife, because many pathogens are zoonotic and can be passed back and forth," she said. "In my career, I hope to be able to understand and not forget that wildlife health is connected to domestic animal and human health. It's all intertwined."
Brown agreed and said that at its core, the project is a great example of research successfully incorporating a One Health approach.
"One Health is a concept that focuses on the interconnectedness of human, animal and environmental health and is dependent on collaboration across different sectors and disciplines," he said. "We were fortunate to have great partners, including those in industry, multiple academic institutions, state and federal agencies, hunters and pet owners, who all helped make this project a success."
