Submitted to: Journal of Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/4/2008
Publication Date: 2/10/2009
Citation: Dubey, J.P., Mergl, J., Gehring, E., Sundar, N., Velmurugan, G., Kwok, O.C., Grigg, M., Su, C., Martineau, D. 2009. Toxoplasmosis in captive dolphins (Tursiops truncatus) and walrus (Odobenus rosmarus). Journal of Parasitology. 95:82-85. Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. Scientists at the Beltsville Agricultural Research Center and University of Tennessee report on Toxoplasma infection in dolphins from Canada. The results will be of interest to biologists, parasitologists, and veterinarians.
Technical Abstract: Toxoplasma gondii infection in marine mammals is intriguing and indicative of contamination of the ocean environment and coastal waters with oocysts. Toxoplasma gondii infection was detected in captive marine mammals at a seaquarium in Canada. Antibodies to T. gondii were found in all 7 bottlenose dolphins (Tursiops truncatus) tested. Two of these dolphins, as well as a walrus (Odobenus rosmrus) at the facility died. Encephalitis and T. gondii tissue cysts were identified in histological sections of the brain of 1 dolphin (dolphin 1). Another dolphin (dolphin 2) had mild focal encephalitis without visible organisms, but viable T. gondii was isolated by bioassay in mice and cats from its brain and skeletal muscle; this strain was designated TgDoCA1. The PCR-RFLP typing using 11 markers (B1, SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) identified a Type II strain. The DNA sequencing of B1 and SAG1 alleles amplified from TgDoCA1 and directly from the brain of dolphin 1, and the brain of the walrus showed archetypal alleles consistent with infection by a Type II strain. No unique polymorphisms were detected. This is apparently the first report of isolation of T. gondii from a marine mammal in Canada.