Raccoon Roundworm Management

Investigations of zoonotic pathogens/parasites carried by human-adapted wild species (synanthropes) are critical for informed management of current or future public health threats. Baylisascariasis is an emerging zoonosis caused by Baylisascaris procyonis, the raccoon roundworm. Raccoons with patent infections can potentially shed millions of eggs in their feces and contaminate the environment. Eggs embryonate and become infective within 2-4 weeks, and are extremely stable in the environment across a range of temperatures. These larval stages have the potential to cause clinical infections with high morbidity and mortality in many vertebrate species including humans. For effective management of an emerging zoonosis like baylisascariasis, it is necessary to first realistically assess the threats posed by the parasite. Alternative host and/or parasite management strategies can then be evaluated. We know that macroparasites like Baylisascaris procyonis are aggregated across their host populations, so that the majority of the parasite population is concentrated into a minority of the host population. Our investigations revealed a highly aggregated distribution of B. procyonis in raccoons from Missouri and Arkansas: prevalence 44.3 % (95%CI 31.9 - 57.4), mean intensity 9.9 (95% CI 5.44 - 17.22; range 1 to 54), variance:mean ratio 29.65, k = 0.17 (Al-Warid et. al., 2017). Such high variability in the number of parasites per host is thus typical, and should be accounted for while undertaking surveillance or designing parasite management interventions. We have developed an agent-based model to support Baylisascaris procyonis surveillance and management strategies.