Dogs can serve as alternative definitive hosts for Baylisascaris procyonis, the raccoon roundworm, but prevalence and geographic distribution of canine infections is poorly studied. In a previous study in the United States (US) from 2013 to 2016, 0.005 % of ∼9.5 million canine fecal samples from the United States (US) were positive for Baylisascaris. To better understand the current prevalence and distribution of Baylisascaris in dogs, fecal floatation results from commercial and academic veterinary diagnostic laboratories from the United States and Canada from 2017 to 2023 were analyzed. Baylisascaris eggs were detected in 2927 of 61,129,486 (0.0048 %) fecal samples. Positive samples originated from 47 US states, Washington D·C, and Ontario, Canada. While many positives originated in regions with high B. procyonis prevalence in raccoons, infections were also identified in several states where B. procyonis has not been reported suggesting a previously unreported presence or expanding geographic range. Higher prevalence was associated with younger dogs, large breeds, and Northeastern and Midwestern US regions. Although overall prevalence was low, Baylisascaris eggs in canine feces pose a public health risk. These eggs are highly resistant to common disinfection methods and can adhere to dog fur, increasing risk of human exposure. Given the zoonotic potential of B. procyonis, regular parasitic screening and deworming and efforts to curb coprophagy should be emphasized. Finally, given the One Health importance aspect of this parasite, public health and veterinary initiatives should continue to investigate Baylisascaris distribution in domestic and wildlife populations to better understand and mitigate risks to humans, wildlife, and exotic animals.
Keywords: Ascaridoidea; Eosinophilic meningoencephalitis; Fecal examination; Neural larval migrans; Raccoon roundworm; Zoonotic.
© 2025 The Authors. Published by Elsevier B.V.