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- Author or Editor: P. Thulliez x
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SUMMARY
Four 1-year-old steers were each inoculated orally with 10,000 Toxoplasma gondii oocysts of the GT-1 strain and euthanatized on postinoculation days (pid) 350, 539, 1191, and 1201. Samples (500 g) of tongue, heart, semimembranosus and semitendinosus muscles (roast), intercostal muscles (ribs), longismus muscles (tenderloin), brain, kidneys, liver, and small intestine were bioassayed for T gondii by feeding to cats and examination of cat feces for shedding of oocysts. Toxoplasma gondii was recovered by bioassays in cats from the 3 steers necropsied pid 350, 539, and 1191, but not from the steer euthanatized on pid 1201. Cats shed oocysts after ingesting tongue from 2 steers, heart from 3 steers, liver from 2 steers, and roast, ribs, brain, and intestines from 1 steer each. Toxoplasma gondii was not isolated from any of the other bovine tissues. In addition to tissues bioassayed in cats, homogenates of mesenteric lymph nodes, lungs, spinal cord, spleen, and eyes were bioassayed in mice for T gondii infection. Toxoplasma gondii was not recovered from the 135 mice inoculated with tissue from each of the 4 steers. All 4 inoculated steers developed high T gondii antibody titers (≥ 1:8,000) in the agglutination test, using formalin-fixed whole tachyzoites. In the steer euthanatized on pid 1201, agglutinating T gondii antibody titers decreased from 1:4,000 to 1:320 between 2 and 5 months after inoculation and to 1:20 by 19 months after inoculation.
Summary
Sixteen pregnant queens were inoculated orally with tissue cysts of Toxoplasma gondii, and fetal membranes and offspring were examined for Τ gondii infection by bioassay in mice. Queens appeared clinically normal, although all shed Τ gondii oocysts. Toxoplasma gondii was isolated from tissues of 7 of 33 fetuses or kittens from 5 litters (at 13, 23, 26, 27, and 29 postinaculation days) from 8 queens euthanatized between 10 and 31 postinoculation days. Infection with Τ gondii was found In kittens from all 8 litters from the 8 queens that were allowed to undergo parturition and nurse their kittens. A total of 43 kittens were born to these 8 quean.
Toxoplasma gondii was isolated from tissues of 26 of 40 kittens bioassayed; in 3 kittens, tissues were not available for bioassay. Toxoplasmosis was severe in full-term kittens born to 5 queens; all 25 kittens from these litters died or were ill by 24 days of age. Anorexia, lethargy, hypothermia, and sudden death were the most common manifestations. Cytologic examination of peritoneal fluid aspirate samples and determination of hepatic-associated enzyme concentrations in affected kittens, as well as measurement of anti-T gondii antibodies in serum of kittens and queens, were helpful in the diagnosis of neonatal toxoplasmosis. Transplacental transfer of anti-T gondii antibodies was not observed in cats. Toxoplasma gondii oocysts were found in fecal samples of 3 kittens from different litters at 16, 24, and 63 days of age.
Abstract
Objective
To follow antibody responses measured by various serologic tests in pigs orally inoculated with low (≤ 10 oocysts) numbers of Toxoplasma gondii oocysts.
Animals
24, 2- to 3-month-old pigs.
Procedure
Pigs (n = 42) were inoculated orally with 10 (14 pigs) or 1 (28 pigs) infective oocysts, and 6 pigs served as uninoculated controls. Blood (serum) samples were obtained at 1- to 3-week intervals until euthanasia. At necropsy, the brain, heart, and tongue of pigs were bioassayed in mice and cats for isolation of T gondii. Modified agglutination test (MAT), using whole, fixed tachyzoites and mercaptoethanol; latex agglutination test (LAT); indirect hemagglutination test (IHAT); Sabin-Feldman dye test (DT); and ELISA were used to evaluate serologic responses to T gondii.
Results
T gondii was isolated from tissues of 13 of 14 pigs each fed 10 oocysts, 17 of 28 pigs each fed 1 oocyst, and 0 of 6 control pigs. 29 of 30 T gondii-infected pigs developed antibodies when measured by MAT, DT, and ELISA; the 1 seronegative-infected pig had been fed 10 oocysts and was euthanatized 69 days after inoculation. LAT detected antibodies in 26 of 30 T gondii-infected pigs. IHAT detected antibodies in 11 T gondii-infected pigs.
Conclusion
MAT, DT, and ELISA were more sensitive serologic assays than LAT and IHAT for detecting antibodies induced by low numbers of T gondii in pigs. (Am J Vet Res 1996;57:1733–1737)
SUMMARY
The sensitivity and specificity of various serologic tests for antibodies to Toxoplasma gondii were compared in 1,000 naturally exposed sows, using isolation of viable T gondii as the definitive test. Serum samples obtained from heart blood of 1,000 sows from Iowa were examined for T gondii antibodies by use of the modified agglutination test (mat), latex agglutination test (lat), indirect hemagglutination test (ihat), and elisa. Toxoplasma gondii was isolated from 170 hearts of 1,000 sows by bioassays in mice and cats. The percentage of samples diagnosed as positive for each of the serologic tests was: mat = 22.2% (titer ≥ 1:20), ihat = 6.4% (titer ≥ 1:64), lat = 10.4% (titer ≥ 1: 64), and elisa = 24.1% (OD > 0.360). The sensitivity and specificity of these tests were calculated respectively to be: 82.9 and 90.29% for mat, 29.4 and 98.3% for ihat, 45.9 and 96.9% for lat, and 72.9 and 85.9% for elisa. The dye test was run at 1:20 dilution on only 893 sera because of bacterial contamination and presence of anticomplement substances. Dye test antibodies were found in 17.8% of the sera, and sensitivity and specificity were 54.4 and 90.8%, respectively. Thus, the mat had the highest sensitivity among all serologic tests used.
Abstract
Objective
To examine cross-reactivity among Neospora caninum and closely-related apicomplexans.
Design
Sera from animals were examined for antibody production to N caninum and cross-reactivity to Toxoplasma gondii.
Animals
Cattle were experimentally infected with 3 tissue cyst-forming protozoan parasites N caninum, T gondii, and Sarcocystis sp, and calves were monospecifically inoculated with the intestinal coccidia, Eimeria bovis and Cryptosporidium parvum. Similar studies were done in laboratory rabbits inoculated with N caninum, T gondii, Hammondia hammondi, and Sarcocystis sp. Additionally, sera were obtained from ewes, lambs, goats, sows, cats, rats, and mice inoculated with N caninum tachyzoites.
Procedure
The indirect fluorescent antibody (IFA) and ELISA antibody tests (cattle only) were used to examine reactivity to N caninum; the modified direct agglutination, Sabin-Feldman dye, and IFA tests were used to evaluate reactivity to T gondii.
Results
Serologic cross-reactivity among N caninum, T gondii, and Sarcocystis sp was none or minimal by the IFA test. There was some reactivity to N caninum by the use of ELISA in cattle inoculated with Sarcocystis sp.
Conclusions
The IFA test for N caninum was specific for the diagnosis of neosporosis in animals.(Am J Vet Res 1996;57:329-336)
Summary
During the hunting season of 1992, 322 black bears from Pennsylvania were examined for Toxoplasma gondii- and Trichinella spp-induced infections. Toxoplasma gondii antibodies were found in 79.8% of 322 bears–titer < 1:25 in 65 (20.2%), 1:25 in 18 (5.6%), 1:50 in 11 (34.5%) and 1:500 in 128 (38.7%) bears –by use of the modified agglutination test. Muscle tissues from 89 of these bears were bioassayed for T gondii parasites. Muscles from 64 bears, including heart from 1 bear, and heart alone from another bear, were digested in pepsin, and the digested samples were bioassayed in mice. Toxoplasma gondii was isolated from 5 bears; from the heart of 1, heart and skeletal muscles of 1, and skeletal muscles of 3. The T gondii antibody titers for the 5 bears with detectable T gondii were: ≥ 1:25 in all 5 bears by use of the modified agglutination test; < 1:10 (3 bears, considered Toxoplasma-negative), 1:20 and 1:320 by use of the Sabin-Feldman dye test; < 1:64 (3 bears, considered Toxoplasma-negative), 1:128, 1:512 by use of the indirect hemagglutination test, and < 1:16 (2 bears, considered Toxoplasma-negative), 1:32, 1:64, and 1:512 by use of the latex agglutination test. Toxoplasma gondii was not isolated from feces of 5 cats fed muscles from the remaining 25 bears with T gondii antibody titer < 1:25. Tissue cysts of the 4 T gondii isolates from bears were rendered noninfective by freezing at – 13 C. Antibodies against Trichinella spp were found in 6 (1.8%) of 319 bear sera; Trichinella spp larvae were detected in muscle digests of 2 of 63 bears, and in histologic sections of muscles from 3 of 162 bears. Genetic typing indicated that the 2 Trichinella isolates from bears were a sylvatic genotype and were not the species found in domestic pigs.
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.
