Baylisascaris procyonis

Page, L. Kristen, 2013, Parasites and the conservation of small populations: The case of Baylisascaris procyonis, International Journal for Parasitology: Parasites and Wildlife 2 (1), pp. 203-210 : 204

2. Baylisascaris procyonis life cycle

Baylisascaris procyonis is an intestinal nematode of raccoons, the definitive host ( Kazacos, 2001). Infections are common among raccoons and prevalence of infection can be as high as 82% ( Kazacos, 2001). Juveniles are susceptible to direct infection via ingestion of eggs; therefore, prevalence can reach>90% among young raccoons ( Kazacos and Boyce, 1989). Prevalence of infection among adult raccoons is lower (37–55%) because they become infected primarily via ingestion of paratenic hosts ( Kazacos, 2001). Seasonal changes in prevalence have been noted in some regions ( Evans, 2002b; Page et al., 2005; Page et al., 2009b) with marked declines during late winter months suggesting a self-cure ( Kazacos, 2001). New infections occur in the spring resulting in highest measurements of prevalence in the fall ( Kazacos, 2001; Evans, 2002b). Mature female worms produce, on average, over 100,000 eggs/day resulting in an infected raccoon shedding as many as 20,000 – 26,000 eggs/g feces (Kazacos, 1982, 2001; Snyder and Fitzgerald, 1985). Under optimum conditions, eggs embryonate to the infective stage within 11–14 days, and can remain viable in the environment for years ( Kazacos and Boyce, 1989; Kazacos, 2001). When small mammals or birds ingest eggs, the larvae emerge and begin an aggressive somatic migration ( Kazacos, 2001), with a low percentage (5%) entering the central nervous system (CNS) causing damage, clinical disease and death ( Tiner, 1953; Sheppard and Kazacos, 1997). Larvae within the CNS or encapsulated in visceral or somatic tissues of paratenic hosts will infect raccoons when the tissue is consumed ( Kazacos, 2001).