Dye Test Antibodies Research Articles

Serologic prevalence of Toxoplasma gondii in horses slaughtered for food in North America

Serum samples from 1788 horses slaughtered for food in North America were tested for antibodies to Toxoplasma gondii using the modified direct agglutination test (MAT). Antibodies to T. gondii were found by the MAT in 124 (6.9%) of 1788 sera; the titers were 1 : 20 (69 horses), 1 : 40 (37 horses), 1 : 80 (9 horses), and ≥1 : 160 (9 horses). A total of 339 selected horses were also tested by the Sabin–Feldman dye test (DT). Dye test antibodies were found in 54 horses with titers of 1 : 10 (29 horses), 1 : 20 (12 horses), 1 : 40 (4 horses) and 1 : 80 (9 horses). There was no correlation between the DT and the MAT.

Toxoplasma gondii Antibodies in Naturally Exposed Wild Coyotes, Red Foxes, and Gray Foxes and Serologic Diagnosis of Toxoplasmosis in Red Foxes Fed T. gondii Oocysts and Tissue Cysts

Antibodies to Toxoplasma gondii were determined in sera from 222 coyotes (Canis latrans), 283 red foxes (Vulpes vulpes), and 97 gray foxes (Urocyon cinereoargenteus) from Indiana, Kentucky, Michigan, and Ohio during 1990-1993. Sera were examined in 1:25, 1:100, and 1:500 dilutions by the modified direct agglutination test (MAT) with formalinized whole tachyzoites plus mercaptoethanol. Antibodies were found in 131 (59.0%) of 222 coyotes, 243 (85.9%) of 283 red foxes, and 73 (75.3%) of 97 gray foxes. Antibodies were also measured by different serologic tests in 4 littermate T. gondii-free red foxes fed T. gondii tissue cysts or oocysts; the fifth littermate fox was not fed T. gondii. Antibodies were measured in fox sera obtained 0, 14, and 36-55 days after infection with T. gondii. All 4 foxes fed T. gondii developed MAT and dye test antibody titers of 1:200 or more 14 days later. The latex agglutination test (LAT) and indirect hemagglutination test (IHAT) were less sensitive than MAT for the diagnosis of T. gondii infection in foxes. Antibodies were not detected by LAT (titer 1:64) in the 2 foxes fed tissue cysts nor by IHAT in 1 of the foxes fed tissue cysts. Toxoplasma gondii was isolated by bioassay in mice from tissues of all 4 foxes fed T. gondii. The control fox had no T. gondii antibodies detectable by any of the serologic tests.

Vertical transmission of toxoplasma by human immunodeficiency virus–infected women

OBJECTIVE: Our goal was to determine the frequency of mother-to-child transmission of Toxoplasma gondii from human immunodeficiency virus–infected mothers who are also chronically infected with T. gondii. STUDY DESIGN: One hundred thirty-eight women were entered into a prospective study of human immunodeficiency virus infection in pregnancy. The women were seen at enrollment, during the third, sixth, and eighth months of pregnancy (except those enrolled later in pregnancy or at delivery), at 2 and 6 months post partum, and at 6-month intervals thereafter through 4 years after delivery. Standardized interviews and physical examinations were performed, and blood was drawn at each visit. Toxoplasma serologic testing was performed on the sample drawn earliest in pregnancy; the Sabin-Feldman dye test for immunoglobulin G antibodies and enzyme-linked immunoassays for immunoglobulins M, A, and E were used. Univariate analysis for categoric variables was performed with χ 2and two-tailed Fisher exact tests, and for continuous variables the Student t test was used. Statistical Analysis System procedures were followed. RESULTS: Twenty-eight of 138 (20.2%) women who had positive test results for human immunodeficiency virus had positive findings of the Sabin-Feldman dye test. Serologic status for T. gondii did not correlate with age, immune status, parity, or drug use. One of 27 children born to women who were seropositive for both human immunodeficiency virus and T. gondii (one child's serologic status for T. gondii was unknown) had Sabin-Feldman dye test antibodies beyond age 6 months (3.7%, 95% confidence interval 0.09% to 18.9%). Among the cohort of human immunodeficiency virus–infected mothers the rate of mother-to-child human immunodeficiency virus transmission did not vary with maternal Toxoplasma status. However, with sample sizes of 28 and 110, respectively, for the mothers who were T. gondii seropositive and seronegative, the power to detect a difference in the human immunodeficiency virus transmission rate between these groups would be relatively small. CONCLUSIONS: Transmission of T. gondii from a chronically infected mother can occur in the setting of a human immunodeficiency virus infection, but this is not a common phenomenon. In a small cohort of human immunodeficiency virus–infected women we did not observe its occurrence among those without severe immunocompromise.(Am J Obstet Gynecol 1997;167:555-9.)

False-positive results in immunoglobulin M (IgM) toxoplasma antibody tests and importance of confirmatory testing: the Platelia Toxo IgM test.

Although tests for detection of immunoglobulin M (IgM) toxoplasma antibodies have been reported to have a high degree of accuracy, it is well recognized by investigators in the United States and Europe that false-positive results may occur with many of these tests, at times to an alarming degree. Unfortunately, this information is not well documented in the literature. Studies on various toxoplasma IgM test kits are frequently flawed. The investigators often use reference tests which have not previously been carefully evaluated as well as sera that were not appropriate to answer the question of how often false-positive results might occur. We recently had the unique opportunity to evaluate the accuracy of the Platelia Toxo IgM test in 575 serum samples obtained during an outbreak of toxoplasmosis which occurred in 1995 in the Capital Regional District of British Columbia, Canada. When compared with results obtained in a reference IgM enzyme-linked immunosorbent assay (ELISA), the Platelia Toxo IgM test had a sensitivity of 99.4%, specificity of 49.2%, positive predictive value of 51.9%, negative predictive value of 99.3%, and an overall agreement of 67.0%. In an attempt to resolve discrepancies between these two tests, a serological profile (Sabin-Feldman dye test, IgA and IgE antibody tests, differential agglutination [AC/HS] test, and IgG avidity method) was performed. Of 153 serum samples that were positive in the Platelia Toxo IgM test and negative in the IgM ELISA, 71 (46.4%) were negative in the Sabin-Feldman dye test. Of the serum samples that were positive in the dye test, 77 (93.9%) had a serological profile most compatible with an infection acquired in the distant past. These results reveal high numbers of false-positive results in the Platelia Toxo IgM test and highlight the importance of appropriate evaluation of commercial tests that are currently being marked. Our results also emphasize the importance of confirmatory testing to determine whether the results of an IgM antibody test reflect the likelihood of a recently acquired infection.

Sensitivity and specificity of various serologic tests for detection of Toxoplasma gondii infection in naturally infected sows

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.

Prevalence of Viable Toxoplasma gondii Tissue Cysts and Antibodies to T. gondii by Various Serologic Tests in Black Bears (Ursus americanus) from Pennsylvania

During the hunting season of 1993, hearts from 28 black bears (Ursus americanus) from Pennsylvania were examined for Toxoplasma gondii infection. Serum samples from heart blood were examined for T. gondii antibodies by the use of the modified agglutination test (MAT), the Sabin-Feldman dye test (DT), the latex agglutination test (LAT), and the indirect hemagglutination test (IHA). One-hundred grams of myocardium from each bear were bioassayed in mice. Approximately 500 g of myocardium from 11 bears were fed to 11 cats, and feces from those cats were examined for T. gondii oocysts. Toxoplasma gondii MAT antibodies (> or = 1:40) were found in 22 bears in titers of 1:40 (4 bears), 1:80 (3 bears), 1:160 (7 bears), 1:320 (4 bears), and > or = 1:2,000 (4 bears). Antibodies to T. gondii by DT (> or = 1:10), LAT (> or = 1:32), and IHA (> or = 1:64) tests were found in 21, 9, and 6 bears, respectively. All 6 bears that did not have T. gondii antibodies in MAT were also negative in DT, IHA, and LAT. Viable T. gondii was isolated from 3 bears by bioassays in mice and from an additional 7 bears by bioassays in cats. All 10 bears that had viable T. gondii had MAT and DT antibodies but only 6 and 5 of them had antibodies by LAT and IHA, respectively.

Treatment and results of chronic toxoplasmosis. Analysis of 33 cases.

Women who grew up in Turkey, where undercooked meat is part of the usual diet, have an increased risk of toxoplasmosis. This study covers treatment and prognosis of 33 cases with chronic toxoplasmosis. The study group was selected among the patients with a history of repeated abortions, recurrent preterm labor, stillbirths and babies with congenital anomaly after all other causative reasons were ruled out. IgG and IgM antibody titers were detected by Sabin-Feldman's dye test and indirect fluorescence antibody test. 33 patients, who had negative IgM and IgG antibody titers above 1/64, were accepted as having chronic toxoplasmosis and were included in our study group. These patients were treated with our pyrimethamine treatment protocol (Dinçer Formula) for 36 days before their pregnancies. IgG antibody titers were repeated in the 8th and the 20th week of pregnancy. With the exception of 7 cases, 24 patients (72.7%) still had IgG antibody titers of more than 1/64 and were given the same treatment protocol in the 8th week of pregnancy. Very early abortions occurred in 2 cases. Of 24 patients, 8 had antibody titers still above 1/64 and were treated with spiramycine. While 28 cases (84.8%) had healthy and living infants, pregnancies of 3 cases are still continuing. No teratogenic effects of pyrimethamine on the fetuses were seen. As a result, we can say that a patient who presents with complaints of repeated abortions, recurrent preterm labor or stillbirth should be investigated for toxoplasmosis during pregnancy; even if the IgG antibody test is normal before pregnancy, she should be treated with the protocol mentioned above before pregnancy and in the 8th week of pregnancy when chronic toxoplasmosis is diagnosed.

Toxoplasmosis in sheep I. Effect of a killed vaccine on lambing losses caused by experimental challenge withToxoplasma gondii

A total of 50 two-tooth ewes were immunized pre-tupping using a killed vaccine of disintegrated Toxoplasma tachyzoites with Freunds incomplete adjuvant. At mid-pregnancy, the ewes were challenged intravenously with 1 x 10(4) live T. gondii tachyzoites. There was no difference in the lambing percentage between ewes vaccinated once and unvaccinated ewes. The lambing percentage for ewes vaccinated twice was significantly lower (p<0.05 normal score) than unvaccinated ewes. The serological response to vaccination and challenge was measured by the Toxoplasma dye test. The level of dye test antibodies at the time of challenge suggests that effective immunity to Toxoplasma n abortion is not dependent on dye test antibody titre. These results suggest that a killed vaccine would Toxoplasma on fertility and lambing performance in not be an effective tool to estimate the effects of commercial flocks.

The prevalence and public health significanceof Toxoplasma gondii in domestic cats in the Niger Delta

The prevalence of Toxoplasma gondii in domestic cats in the Niger Delta was assessedby both serological examination for antibody using the Sabin-Feldman dye-test and faecal examination for the presence of oocyst. Of the cats, 94·2% had dye-test antibody. No significant sex or age-linked variation was observed in the prevalence of the antibody. Of the faecal samples, 22·0% contained oocysts of Isospora felis, 12·4% Isospora rivolta and 32·0% Toxoplasma gondii. These observations are discussed in relation to public health.

Partially purified antigen preparations of Toxoplasma gondii protect against lethal infection in mice.

Antigens of Toxoplasma gondii eluted from polyacrylamide gels after electrophoresis under reducing conditions were examined for their capacity to react with antibodies from infected humans, to induce antibody formation, and to protect mice against T. gondii. Antigens with approximate molecular weights of 35,000 and 14,000 strongly reacted in an enzyme-linked immunosorbent assay of human immunoglobulin M (IgM) and IgG antibodies to T. gondii. Mice injected with the eluted antigen preparations formed antibodies that reacted differently in four serological tests for Toxoplasma antibodies. All mice formed antibodies that reacted in the IgG and IgM enzyme-linked immunosorbent assay. Antibodies reacting in the conventional indirect immunofluorescent antibody test were detected in all mice except those injected with low-molecular-weight (14,000 or less) antigens. Sabin-Feldman dye test antibodies were not detected in any of the mice. Antibodies reacting in the latex agglutination test were detected mainly in mice injected with antigens with an approximate molecular weight of 66,000. Challenge of the injected mice with a lethal inoculum of T. gondii revealed that the highest survival rate was in animals that received antigens with approximate molecular weights of 35,000 and 14,000.

Serologic evidence for acute toxoplasmosis in polymyositis-dermatomyositis: Increased frequency of specific anti-toxoplasma IgM antibodies

Several case reports have suggested an association between acquired toxoplasmosis and polymyositis-dermatomyositis. Because the presence of anti-Toxoplasma IgM antibodies suggests recent infection, 58 patients with polymyositis-dermatomyositis (from two medical centers) were examined for the presence of IgM antibodies using a specific indirect immunofluorescent technique. Serum samples were also examined for antibodies using the Sabin-Feldman dye test and complement fixation methods. Of 58 patients with polymyositis-dermatomyositis, 29 (50 percent) had positive Sabin-Feldman dye test results and 14 (24 percent) had positive IgM immunofluorescent findings. This is higher than the expected frequency. None of the patients with negative Sabin-Feldman dye test results had IgM immunofluorescent antibodies. Furthermore, IgM immunofluorescent antibodies were associated with the presence and titer of both Sabin-Feldman dye test and complement fixation antibodies. Evidence that the presence of antinuclear antibody and rheumatoid factor did not influence these results is presented. Patients with muscular dystrophy and systemic lupus erythematosus (with or without myositis) did not have an increased frequency of anti-Toxoplasma IgM immunofluorescent antibodies.

The prevalence ofToxoplasma gondiiin meat animals and cats in central Scotland

The prevalence of Toxoplasma gondii in meat animals and cats in central Scotl and was measured by serological examination for antibody using the Sabin-Feldman dye-test. Of 250 each of cattle, sheep and pigs, 2·8, 15·2 and 9·2%, respectively, possessed significant antibody titres: 28·0% of 100 stray cats and 19·4% of 36 domiciled cats also had dye-test antibody. No significant sex or age-linked variations were observed in the prevalence of antibody. In faecal samples collected from the stray cats, 12·0% contained oocysts of Isospora (= Levineia) felis, 2·4% I. rivolta and 2·0% T. gondii. The results are compared with those of similar surveys.

Oocyst formation in cats survived after intraperitoneal inoculation of Toxoplasma cysts.

In this experiment, 9 cats were inoculated intraperitoneally with 1 or 3 mouse brains containing Toxoplasma cysts. Four of them died of acute toxoplasmosis within 2 weeks after inoculation, and none of oocysts was excreted in the feces of these animals during the infection. The remaining 5 cats (1 cat inoculated with 3 mouse brains and 4 cats with 1 mouse brain) recovered from acute infection excreting oocysts during the convalescent phase of infection. The prepatent periods ranged between 19 and 24 days and the patent periods lasted 5 to 7 days. The prepatent periods of these animals were prolonged significantly compared with that of oral administration of cysts. All recovered cats developed dye test antibody during the prepatent period and the antibody attained peak in titer at the patent period. It is suggested that the dye test antibody does not affected directly against development of oocyst in the intestine of the cats.

Toxoplasmosis in farmed red deer (Cervus elaphus) in Scotland

Farming of red deer began in Scotland in 1970 when an experimental nucleus was established on a hill farm in Kincardineshire. From 1972 to 1977 sera from these animals were tested by the haemagglutination test (HA) and the Sabin-Feldman dye test (DT) for the presence of antibodies to Toxoplasma gondii. Overall, dye test antibodies (greater than or equal to 1/16) were detected in 32.5 per cent of sera and HA antibodies in only 9.8 per cent. On average 14.1 per cent of the deer tested in 1972, 1973 and 1975 were DT positive while a sharp rise to 51.4 per cent was noted in the 1974 animals. These antibody titres were not sustained nor were they reflected by the HA. Marked animals bled serially throughout the survey confirmed the general low level of antibody in the herd and the spasmodic rise in 1974. Experimentally infected deer showed a rise and subsequent fall in DT antibody levels with persistently low HA titres. Since the correlation between HA and DT antibody titres was generally poor the HA would be of limited value in screening for Toxoplasma antibody in farmed red deer sera. The direct agglutination test was used to examine selected sera and the results indicated its potential screening value.

Infants potentially at risk for congenital toxoplasmosis: a prospective study.

Fifty-two children were selected as being potentially at risk for congenital toxoplasmosis by serologic testing of 8,043 pregnant women in the Oslo area. These infants were then studied during the neonatal period and subsequently followed up for three years. Three were found to be congenitally infected with Toxoplasma gondii, and one infant was dysmature at birth. The diagnosis was confirmed by persistent dye-test antibodies and by recovery of parasites in placenta and/or amniotic fluid. The Toxoplasma indirect fluorescent IgM-antibody test remained negative, while measurements of cord IgM and IgA levels and serial estimations of specific antibody load supported an early diagnosis. The specific cell-mediated immunity, as measured by the in vitro lymphocyte stimulation test, turned positive at 1 year of age and then increased markedly during the second and third years. The lymphocyte responses of the uninfected children, however, remained negative. The infected children received pyrimethamine/sulfadiazine treatment during their first year, with no clinical signs of congenital toxoplasmosis.

The prevalence of toxoplasma antibodies among 11,736 pregnant women in Norway.

A serologic screening for toxoplasma antibodies by dye test (DT) and IgG indirect fluorescent antibody test (IgG-IFAT) has been carried out among 10729 pregnant women in the Oslo area and 1 007 pregnant women from the county of Møre and Romsdal situated on the west coast of Norway. The frequency of toxoplasma antibodies was found to be higher in women living in rural areas and a higher prevalence was observed among women living in the western districts of Oslo than among women from the eastern districts of the city. The mean frequency of DT antibodies was found to be 12.5% in the Oslo area and 13.3% in Møre and Romsdal, whereas the yearly incidence of acquired infections in the two areas was found to be 5 and 2.3%, respectively. The predicted incidence of congenital toxoplasmosis in the Oslo area, and presumably also in the whole country, would represent 2% of all pregnancies. No serologic differences were found when women with prior histories of either sporadic or habitual abortions were compared to a total group of multigravidae among the Oslo women.

The Prevalence of Toxoplasmosis on Pacific Islands, and the Influence of Ethnic Group

The prevalence of Toxoplasma dye-test antibody was determined in inhabitants of a number of Pacific islands, in Melanesia, Micronesia and Polynesia, and on Taiwan. With the exception of one island in French Polynesia, two Hawaiian islands, and Taiwan, Toxoplasma antibody prevalences were high, ranging between 84% and 100% in the adult populations tested. On the Hawaiian islands of Oahu and Hawaii, populated by several ethnic groups, and where about 50% of the total adult populations were estimated to have been infected with Toxoplasma gondii, a marked variation in prevalence of infection by ethnic group was observed. The lowest prevalence in the Hawaiian islands estimated at about 15% to 20% in adults, was observed in Japanese. On Taiwan, only 6% of adult ethnic Chinese and 1% of aborigines tested had Toxoplasma antibody.

Acquired toxoplasmosis. A neglected cause of treatable nervous system disease.

The neurological manifestations of six cases of acquired central nervous system toxoplasmosis are compared with the 39 well-documented cases from the literature. Half of the patients had underlying systemic diseases (18 malignant neoplasms, two renal transplants, three collagen vascular diseases) treated with intensive immunosuppressive therapy. The remainder had primary toxoplasmosis. Three major neurological patterns were seen: (1) diffuse encephalopathy with or without seizures, (2) meningoencephalitis, and (3) singular or multiple progressive mass lesions. Routine neurological diagnostic studies were not helpful. The Sabin-Feldman dye test or IgM indirect fluorescent antibody test or both were effective in confirming the diagnosis. Twenty-seven patients died without a clinical diagnosis of toxoplasmosis. The diagnosis was made terminally in four additional patients. Thirteen of fourteen patients who received a full course of sulfadiazine or pyrimethamine or both did well. Toxoplasmosis should be considered in the immunosuppressed patient who appears with neurological involvement.

Plate Hemolysin Test for the Rapid Screening of Toxoplasma Antibodies

A plate hemolysin test was developed to screen serum specimens for the presence of toxoplasma antibodies. When we tested 130 sera by both this test and the standard toxoplasma dye test, we found the plate hemolysin test to be a rapid, sensitive, and economical method for detecting toxoplasma antibodies. In all but one instance it paralleled the dye test. A comparison of the results of testing six sera by the hemolysin, hemagglutination, and dye-test techniques suggested that the hemolytic antibodies were more closely related to hemagglutinating antibodies than to dye-test antibodies. We could not store sheep erythrocytes sensitized with toxoplasma lysate for more than 3 days without altering the sensitivity of the test. Concanavalin A proved to be an effective coupling agent for binding toxoplasma antigens to red-cell membranes, a quality attributed to its affinity for specific polysaccharide-combining sites.

Sarcocystis in mice inoculated with toxoplasma-like oocysts from cat feces.

Sarcocysts morphologically similar to Sarcocystis muris were observed in mice after inoculation with Toxoplasma-like oocysts found in feces of a stray cat. Cats that were fed mice infected with the oocysts shed similar oocysts in their feces. Sarcocysts were found histologically in about 50 percent of mice inoculated with 40,000 or more oocysts and examined 42 days or longer after exposure. Most inoculated mice developed low Toxoplasma dye-test antibody titers 3 to 4 weeks after exposure, but Toxoplasma antibody was usually not detectable in infected cats.