Comparison of Tissue Digestion Techniques for Detecting Toxoplasma gondii in Cockles (Anadora granosa) along the Coast of Thailand

Abstract

Toxoplasma gondii is a parasite in the phylum Apicomplexa that causes an infection called toxoplasmosis in a majority of endothermic vertebrates. It is believed that felids, such as domestic cats, are the only definitive host used by this parasite; this is where sexual reproduction of unsporulated oocysts occurs (Figure 1). The oocysts are released and passed into the environment through feces, developing into an infectious stage in order to invade the intermediate host, often marine animals and livestock. The infection will remain asymptomatic in immunocompetent bodies, but once the immune system is suppressed, many symptoms may occur. Due to a decreased number of sea otters (Enhydra lutris nereis) in California as a result of this parasitic infection, it is assumed that cockles (Anadara granosa), which otters prey upon, may act as vehicles carrying the parasite. To test this assumption, we conducted an analysis of cockles along the coast of Thailand. In this study, we compared two digesting methods- pepsin digestion and fat extraction by ethyl acetate using gill and digestive tract tissue (the locations where the parasites are most likely to be found; Figure 2) and observe whether which technique has a higher sensitivity to the parasites.