Concentration and retention of Toxoplasma gondii surrogates from seawater by red abalone (Haliotis rufescens)

Abstract

Toxoplasma gondii is a pathogenic apicomplexan parasite and a significant cause of mortality in the threatened southern sea otter (Enhydra lutris nereis). Sea otter prey selection behavior has been linked to risk of exposure to T. gondii – specifically, marine snails have been identified as high-risk prey items, and abalone have been identified as low-risk prey items. Previous work evaluating snails as a potential paratenic host for T. gondii has demonstrated that they are capable of concentrating oocysts and oocyst surrogates from seawater by 2-3 orders of magnitude and retaining them in digestive tissues for as long as 11 days post-exposure; however, no such work has been done with abalone. This study aimed to determine 1) whether abalone are physiologically capable of concentrating T. gondii oocysts and 2) if they are, whether the abalone and snail differ with respect to their ability to concentrate and retain oocysts. Red abalone (Haliotis rufescens) were exposed to oocyst surrogates for 24 hours at concentrations of ~8.8 surrogates/ml in tubs furnished with fresh kelp (Macrocystis pyrifera) fragments. Fecal samples were collected for two weeks following exposure and examined by epifluorescent microscopy. Abalone were found to concentrate surrogates by 2-3 orders of magnitude and retain them for at least 14 days post-exposure, indicating that protection factor associated with prey preference for abalone is not the result of a reduced physiological ability to concentrate and retain oocysts.