Location: Animal Parasitic Diseases LaboratoryTitle: Toxoplasma gondii abortion storm in sheep on a Texas farm and isolation of mouse virulent atypical genotype T. gondii from an aborted lamb from a chronically infected ewe Author
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2012
Publication Date: 2/1/2013
Citation: Edwards, J.F., Dubey, J.P. 2013. Toxoplasma gondii abortion storm in sheep on a Texas farm and isolation of mouse virulent atypical genotype T. gondii from an aborted lamb from a chronically infected ewe. Veterinary Parasitology. 192:129-136. 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 under-cooked meat from infected animals, as well as food and water contaminated with oocysts. The authors report abortions in sheep in Texas associated with toxoplasmosis for the first time. The results will be of interest to biologists, parasitologists, and public health workers.
Technical Abstract: Sheep are commonly infected with the protozoan parasite, Toxoplasma gondii. Infection may cause early embryonic death and resorption, fetal death and mummification, abortion, stillbirth, and neonatal death. Most sheep acquire T. gondii infection after birth. Recent studies reported that repeat ovine transmission of T. gondii may be more common than previously believed, but these findings are solely based on PCR data and require confirmation using other techniques to verify the findings. In the present study, during the lambing season of 2005 a toxoplasmosis abortion storm occurred in a flock of purebred Suffolk ewes on a farm in Texas; only 14 healthy lambs were born, and 38 abortuses, mummies and weak or stillborn lambs were delivered. Another 13 fetuses identified by ultrasound were presumably resorbed or were aborted undetected. Antibodies to T. gondii were found in 35 (94.5%) of the 37 ewes and 29 of them had high titers (1:3200 or higher) when tested in the modified agglutination test (MAT). In the next lambing season in 2006, only one ewe that had a MAT titer of 1:3200 aborted due to toxoplasmosis; viable T. gondii (designatedTgShUs55) was isolated from the brain and heart of the aborted fetus. TheTgShUs55 had an atypical genotype using 10 PCR-RFLP markers, and was 100% lethal for Swiss Webster mice, irrespective of the dose or the stage of the parasite inoculated. In subsequent lambings, ewes lambed normally. The results of the present study support the hypothesis that most sheep that have aborted due to T. gondii develop protection against future toxoplasmosis induced abortion.