Search Results
You are looking at 1 - 4 of 4 items for
- Author or Editor: S. K. Shen x
- Refine by Access: All Content x
Summary
Three Jersey cows were inoculated sc and IM with 26 million Neospora caninum tachyzoites at 129 (cow 1), 126 (cow 2), and 81 (cow 3) days after mating. Cows remained clinically normal for at least 1 month after inoculation of N caninum. Cow 1 was euthanatized 32 days after inoculation because of gangrenous mastitis. Cow 1 had a live fetus with no gross lesions; however, microscopic lesions were seen in the fetus and consisted of severe nonsuppurative necrotizing encephalitis of the cerebral white matter. Neospora caninum was identified in lesions by staining with anti-N caninum serum in an immunohistochemical test, by bioassays in mice, and by inoculation of bovine monocyte cultures with fetal tissue homogenate. Neither N caninum nor lesions were associated with infection with the protozoon identified in tissues of cow 1. Cows 2 and 3 aborted small autolysed fetuses 101 and 74 days, respectively, after inoculation with N caninum; the fetuses and attached placenta were unsuitable for laboratory investigations. Cows 2 and 3 remained clinically normal 4 months after abortion. Results of this study indicated that N caninum can be transmitted transplacentally in cattle.
Summary
Persistence of the vaccine RH strain of Toxoplasma gondii was studied by bioassay and histologically in 14 pigs. Pigs were euthanatized 2, 4, 7, 8, 14, 15, 21, 29, 36, 42, 52, 57, and 76 days after im inoculation with 100,000 T gondii tachyzoites. Viable T gondii tachyzoites derived from the RH strain were isolated by bioassay in mice inoculated with tissues of pigs euthanatized up to 14 days after vaccination. Except for fever, pigs vaccinated im with the RH strain remained clinically normal. Two other pigs inoculated iv with 100,000 T gondii tachyzoites of the RH strain became ill, and 1 pig was comatose by 4 days after inoculation. These findings indicate that route of inoculation may influence the response of pigs to T gondii. To evaluate protective immunity in pigs vaccinated with the RH strain, 16 age-matched pigs were allotted to 4 groups (A-D) of 4 pigs each. Eight pigs (groups A and C) were vaccinated im with 100,000 RH strain tachyzoites and 8 pigs (groups B and D) were nonvaccinated controls. Pigs of groups A and C were challenge-inoculated orally with a lethal dose of T gondii oocysts (100,000 oocysts) 81 days after vaccination, pigs of groups B and D were inoculated similarly 220 days after vaccination. The concentration of T gondii at 3 days after challenge inoculationl of pigs vaccinated 81 days earlier was reduced 100,000-fold in mesenteric lymph nodes, compared with that in a nonvaccinated pig euthanatized at 3 days after challenge inoculation. Another nonvaccinated pig became comatose and had to be euthanatized at 7 days after challenge inoculation; numerous tachyzoites were in its mesenteric lymph nodes, intestines, and liver. The vaccinated pigs generally remained clinically normal after challenge inoculation with oocysts. Toxoplasma gondii was not isolated by bioassays from tissues of 5 of 8 vaccinated pigs, but was recovered from all nonvaccinated pigs. Results indicate that protective immunity persisted in pigs for at least 7 months after vaccination with the nonpersistent RH strain of T gondii.
Summary
Four-week-old chickens were inoculated orally with 1,000 or 100,000 oocysts of the ME-49 or GT- 1 strain of Toxoplasma gondii, and their antibody responses were measured, using the direct modified agglutination test, latex agglutination test, indirect hemagglutination test, elisa, and the Sabin-Feldman dye test. Antibodies against T gondii were detected by use of the modified agglutination test and elisa within 2 weeks of oocyst inoculation, and antibodies persisted until termination of the study by postinoculation day 68. The latex agglutination test was insensitive in detecting T gondii antibodies, and antibodies were not detected by use of the dye and indirect hemagglutination tests. Of tissues bioassayed in mice for tissue cysts by pepsin digestion of individual organs of chickens on postinoculation day 68, tissue cysts were found in the brain of all 5, heart of 3, and leg muscles of 2, but not in the liver and breast muscles. None of the birds developed clinical toxoplasmosis.
Summary
A serologic survey that tested for antibodies to Toxoplasma gondii was conducted, using the modified direct agglutination test, on 6,965 serum samples collected from swine in 179 herds in Illinois in 1992. In breeding swine, results for 1,057 of 5,080 (20.8%) sera tested were positive. In growing/finishing swine, results for 59 of 1,885 (3.1%) sera tested were positive, which was substantially lower than the seroprevalence rate estimated in a serosurvey of pigs from abattoirs in Illinois in 1983 and 1984. Data in the survey reported here were summarized for herds having at least 28 samples/herd. Among all herds, the median, mean, and maximum seroprevalence rates were 6.7, 16.1, and 96.8%, respectively, for breeding swine in 172 herds, and 0.0, 2.8, and 20.0%, respectively, for growing/finishing pigs in 44 herds. Among the 172 herds with breeding swine, 61 (35.5%) had no seropositive pigs. Among the 44 herds with growing/finishing swine, 28 (63.6%) had no seropositive pigs. A logistic regression model was used to estimate that the cumulative risk of T gondii infection for swine in herds containing seropositive pigs was 9.0% by 6 months of age for a herd that had the median seroprevalence rate. In contrast, for pigs in herds in the upper quartile of seroprevalence rates, risk of infection by 6 months of age was estimated to be greater than 20%. Analysis of these data would suggest that overall prevalence of T gondii infection in pigs from Illinois is low; nevertheless, there is a small proportion of farms for which the rate of T gondii infection in swine is moderately high.
