PCR fecal testing detects Echinococcus in Pennsylvania wild canids

A multi-institution team that screened more than 27,000 canine fecal samples from Pennsylvania detected Echinococcus species in wild canids but in none of the pet or hunting dogs tested, according to findings published in One Health.¹

Echinococcus is a zoonotic cestode that frequently produces no clinical signs in its canid definitive hosts but can cause serious disease in humans, who can serve as alternative intermediate hosts for both Echinococcus multilocularis and Echinococcus granulosus sensu lato.¹ Recent detections in the eastern United States and Canada prompted the investigators to survey the parasite’s distribution in the commonwealth.¹

“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,” said Justin Brown, DVM, PhD, associate teaching professor of veterinary and biomedical sciences in Penn State’s College of Agricultural Sciences, in a university news release.²

What the survey tested

Investigators analyzed 27,293 fecal samples using the KeyScreen GI Parasite PCR assay, a panel that detects and differentiates 20 gastrointestinal parasites of dogs and cats, several of them zoonotic.^1,2 The sample set comprised 26,979 pet dogs, 52 hunting dogs, and 262 wild canids, including coyotes, red foxes, and gray foxes.¹

The team hypothesized that parasite burden would fall along a gradient, with the highest levels in wildlife and the lowest in owned pets, allowing them to characterize the parasite communities in each group.² That pattern held and the release reports higher levels of multiple parasites in wild canids than in pet dogs, and higher levels of parasites such as hookworms and whipworms in hunting dogs compared with pet dogs.²

Where Echinococcus turned up

E multilocularis was detected in 4 animals: 2 gray foxes and 2 coyotes, and one additional coyote tested positive for Echinococcus canadensis (G8). No pet dog or hunting dog sample was positive for either Echinococcus species.¹

“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,” Brown said.²

Why fecal flotation can miss it

The detection challenge is as much diagnostic as epidemiologic. “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.”²

A companion project led by Noelle Kuhn, then an undergraduate scholar in Penn State’s Schreyer Honors College and now a veterinary student at Michigan State University, compared fecal flotation directly against the PCR panel in wild canids. Kuhn performed the flotations, submitted parallel samples for PCR testing, and ran the statistical analysis; she found the PCR assay more sensitive for the 20 parasites on the panel and able to distinguish between eggs that are visually identical under the microscope.²

Brown cautioned that the molecular panel is not a wholesale replacement, particularly in wildlife, which carry a broader range of parasites than the assay covers.²

“[Kuhn’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.²

Clinical relevance

For practitioners, the absence of positives among owned dogs is reassuring but not exculpatory: the parasite is established in local wildlife, canid definitive hosts are typically asymptomatic, and the diagnostic method most clinics rely on is poorly suited to finding it. Dogs with access to wildlife habitat, rodent prey, or hunting activity remain the plausible bridge between the sylvatic cycle and human exposure.

Brown framed the work as a One Health exercise. “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.”²

References

1. Garrett KB, Brown J, Jimenez Castro PD, et al. Prevalence and distribution of Echinococcus species in domestic dogs and wild canids in Pennsylvania: KeyScreen GI Parasite PCR testing of fecal samples. One Health. 2026;22:101323. doi:10.1016/j.onehlt.2026.101323
2. Bohn K. Diagnosing parasites that pose health risks for dogs, humans. News release. Penn State University; September 14, 2026. Accessed September 14, 2026. https://www.psu.edu/news/agricultural-sciences/story/diagnosing-parasites-pose-health-risks-dogs-humans