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Title: RESPONSES OF NURSING PIGS TO INFECTION WITH DIFFERENT ISOLATES OF TOXOPLASMA GONDII

Author
item PINCKNEY R D - AUBURN UNIVERSITY
item LINDSAY D S - AUBURN UNIVERSITY
item BLAGBURN B L - AUBURN UNIVERSITY
item BOOSINGER T R - AUBURN UNIVERSITY
item MCLAUGHLIN S A - AUBURN UNIVERSITY
item DUBEY JITENDER P - 1265-55-00

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: Infections by the protozoan parasite, Toxoplasma gondii are widespread in livestock and humans in the U.S. It can cause abortion and neonatal mortality in livestock and mental retardation and loss of vision in congenitally infected children. Humans become infected by ingesting water contaminated with oocysts (resistant form of Toxoplasma) or meat infected with tissue cysts. There is no vaccine to reduce or prevent T. gondii infection in man or animals in the U.S. Scientists at the Beltsville Agricultural Research Center and the Auburn University report safety trials with a mutant strain (ts-4) of T. gondii in pigs. Pigs inoculated with the ts-4 strain remained clinically normal but developed protective immunity. These results will be useful in developing a vaccine for toxoplasmosis in pigs.

Technical Abstract: Two experiments were conducted to determine the responses of nursing pigs to inoculation with Toxoplasma gondii. Experiment 1 was conducted to determine the safety and host tissue distribution of the TS-4 mutant and its parent RH isolate in 3-day-old nursing pigs. Group 1 consisted of 2 pigs inoculated intravenously (i.v.) with Hanks' balanced salt solution (HBSS), group 2 consisted of 5 pigs inoculated i.v. with 3 x 100,000 tachyzoites of the TS-4 isolate of Toxoplasma gondii, group 3 consisted of 5 pigs inoculated i.v. with 3 x 100,000 tachyzoites of the RH isolate of Toxoplasma gondii, group 4 consisted of 3 pigs inoculated subcutaneously (s.c.) with 3 x 100,000 tachyzoites of the TS-4 isolate in the dorsal medial surface of the right ear, and group 5 consisted of 3 pigs inoculated with 3 x 100,000 tachyzoites of the RH isolate s.c. at the same site. Experiment 2 was conducted to determine if pigs (2 each from groups 1, 2 and 4) inoculated at 3 days-of-age (Day 0), and boosted 14 days postinoculation (PI), were protected against challenge orally with 8 x 10,000 oocysts of the GT-1 isolated of T. gondii at 33 days-of-age (day 30). In experiment 1, mild to no clinical signs of disease were observed in the groups 1, 2, or 4 pigs and microscopic lesions were either minimal or absent in these pigs. Severe disease developed in i.v. inoculated pigs but not in s.c. inoculated pigs. Previous exposure to the TS-4 isolate by i.v. or s.c. inoculation did not prevent tissue cyst formation in pigs following oocyst challenge. However, results of bioassays in mice indicated that pigs given the TS-4 isolate s.c. had fewer tissue cysts in their tissues after oocyst challenge.