Heterobilharziasis (Trematoda: Schistosomatidae) in Raccoons (Procyon Lotor) of North-Central Texas (Report‪)‬

Abstract. - The mammalian schistosome Heterobilharzia americana was collected from a sample of 36 raccoons (Procyon lotor) in Archer and Wichita counties of north-central Texas, providing new county records and a northern range extension for the fluke in the state. Overall prevalence of adult flukes in raccoons was 47.2 %, suggesting that the fluke is well established in the region. Fluke parasite load (abundance) and infection rates were compared among host subgroups by sex, age class, and season of capture. No significant differences were found by host sex. Seasonal discrepancies in fluke infection rates and parasite loads were insignificant, though sporadic cercarial exposure in young raccoons and small sample size may have obscured seasonal trends. Host age played a significant role in fluke parasite load and infection rate, with older age class raccoons having greater infection rates, prevalence, and parasite loads, but smaller, less variable mean intensities than younger age class raccoons. While the results of this study concur with previous studies of H. americana in mammalian hosts, the reduced mean intensity of flukes in older age class raccoons may indicate a degree of acquired immunity in infected adult hosts, as is commonly seen with other schistosome species. Heterobilharzia americana (Trematoda: Schistosomatidae) is a common North American mammalian blood fluke. Naturally occurring H. americana have been found in a wide variety of mammalian hosts (Price 1929; Price 1943; Malek 1961; Kaplan 1964; Sponenberg 1976; Custer & Pence 1981; Goff & Ronald 1981; Schaffer et al. 1981; Shoop & Corkum 1982; Krotoski et al. 1984; Forrester et al. 1985; Fedynich et al. 1986; Yamini & Schillhorn van Veen 1988; McKown et al. 1991; Forrester et al. 1994; Flowers et al. 2002), and several additional mammalian species have developed patent infections experimentally (Lee 1962b; Malek 1970). However, the raccoon (Procyon lotor) appears to be the principle definitive host (Lee 1962a; Flowers et al. 2002).