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Uptake and transmission of Toxoplasma gondii oocysts by migratory filter-feeding fish
Massie, G. N., M. W. WARE, E. VILLEGAS, AND M. W. Black. Uptake and transmission of Toxoplasma gondii oocysts by migratory filter-feeding fish. Veterinary Parasitology. Elsevier, Shannon, Ireland, 169(3-4):296-303, (2010).
The overall objective of this task is the development of improved occurrence detection methods for protozoan parasites and Microsporidia. Since this work is a primary focus of the Branch, this task supports several individual projects related to sample preparation and protozoan detection. Together these projects will lead to complete methods able to support the UCMR and the CCL2 and CCL3.
Toxoplasma gondii is a ubiquitous parasitic protozoan known to cause disease and death in warm-blooded animals. Bottlenose dolphins, walruses, sea otters, and other marine animals worldwide have died from toxoplasmosis, but the source of this parasite in the marine environment has not been determined. Migratory filter feeders, specifically northern anchovies (Engraulis mordax) and Pacific sardines (Sardinops sagax), may serve as paratenic hosts for T. gondii within the marine environment. If these fish are capable of filtering oocysts from seawater in the nearshore environment, it is possible that they could serve as biotic vectors as they migrate to pelagic environments. In this study, northern anchovies and Pacific sardines were experimentally exposed to T. gondii oocysts under laboratory conditions. Following exposure, the fish alimentary canals were harvested by necropsy and assayed for the presence of T. gondii by PCR and a mouse bioassay. Results showed that the majority of these samples tested positive for T. gondii by PCR and 7 out of 23 (30%) of the mice developed toxoplasmosis when fed sucrose-purified contents of the alimentary canals of fish exposed to 100,000 ooccysts/ L. These results demonstrated that northern anchovies and Pacific sardines can accumulate T. gondii oocysts that remain infectious.