Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 10, 1999
Publication Date: N/A
Interpretive Summary: Infections with the single celled parasite, Toxoplasma gondii are widely prevalent in man and animals. It causes mental retardation and loss of vision in congenitally infected children and abortion in livestock. Rats are considered one of the resistant hosts of Toxoplasma, and they are a suitable animal model for human toxoplasmosis. Scientists at the Beltsville Agricultural Research Center have found that rats can be infected with 1 live Toxoplasma. Rats vaccinated with a few parasites became resistant to lethal infections. The results will be of use to parasitologists and biologists in the study of the biology of Toxoplasma.
Technical Abstract: Infection and immunity to toxoplasmosis induced by the RH strain of Toxoplasma gondii was compared in Sprague Dawley and Wistar rats and in outbred Swiss Webster mice. All rats injected with up to 1,000,000 RH strain tachyzoites remained clinically normal whereas mice injected with only 1 live tachyzoite died of acute toxoplasmosis. Rats could be infected dwith 1 tachyzoite of the RH strain as shown by antibody development and by bioassay in mice. However, after 8 days, RH strain organisms were recovered only inconsistently from Sprague Dawley and Wistar rat brains. Contrary to a report of sterile immunity to T. gondii infection in rats after immunization with live RH tachyzoites, we found infection-immunity after challenge with the VEG strain. Toxoplasma gondii tissue cysts of the VEG strain could be recovered from most Sprague Dawley and Wistar rats, first injected with live RH strain tachyzoites and then challenged with oocysts of the VEG strain.