Vaccination of sheep with a live incomplete strain (S48) of Toxoplasma gondii and their immunity to challenge when pregnant

Sixty-four ewes were vaccinated with tachyzoites of an incomplete strain (S48) of Toxoplasma gondii grown either in the peritoneal cavity of mice (group 1) or vero cell culture (group 2) and 30 ewes (group 3) were not vaccinated. All the ewes were mated 77 days later and challenged orally with 2000 sporulated oocysts at 89 to 90 days of gestation. Ten additional unvaccinated (group 4) and 10 vaccinated (group 5) control ewes were not challenged. The unvaccinated ewes developed a characteristic febrile response to challenge while in the vaccinated ewes the fever commenced earlier but was less severe and of shorter duration. After challenge, the antibody titres against T gondii rose rapidly to high values in the vaccinated ewes while the ewes in group 3 responded more slowly. Only eight of the 45 fetuses/lambs (17.8 per cent) from group 3 were viable compared with 72.3 per cent of those in group 1 and 80.8 per cent of those in group 2. Gestation in the unvaccinated challenged ewes was shortened and the mean birthweight of their single, viable offspring was significantly lower than the weight of single lambs from the vaccinated (groups 1 and 2) and control ewes (groups 4 and 5). Examination of precolostral sera showed that almost two-thirds of the lambs from the vaccinated ewes were infected in utero. The 20 control ewes appeared clinically normal at all times and lambed normally. The two vaccine preparations were equally effective.     

Toxoplasma gondii-induced abortion in sheep

Twenty-nine of 200 (14.5%) ewes on a farm in Cobleskill, NY aborted or had dead lambs during the lambing seasons of 1985 and 1986. Thirteen of 15 ewes that aborted had high Toxoplasma gondii antibody titers (1,024), via the modified agglutination test, and T gondii was isolated from the tissues of 1 fetus. In the 1987 lambing season, 5 ewes aborted, but not because of T gondii infection. Toxoplasma gondii antibodies were detected in 73.8% of sera obtained from 592 ewes in January 1987, indicating enzootic toxoplasmosis on this farm. Seropositivity increased with age; 40.2% of 1-year-old ewes had detectable antibody vs 89.2% of 2-year-old ewes.     

Economic and public health considerations of congenital toxoplasmosis in lambs

Congenital toxoplasmosis was diagnosed in a flock of Hampshire sheep in South Dakota. The 80 ewes produced 144 lambs, 30 of which were born dead; toxoplasmosis was diagnosed in 11 of the dead lambs. The remaining 114 lambs grew normally, but 68 (40.3%) had agglutinating Toxoplasma gondii antibodies. Modified agglutination test T gondii antibody titers for 114 lambs were: less than 100 (n = 46), 64 (n = 2), 256 (n = 1), 1,024 (n = 12), and greater than or equal to 4,096 (n = 53). Tissues of 8 seropositive lambs were bioassayed for T gondii tissue cysts. Toxoplasma gondii was isolated from the tongue and lamb chops of 7, heart of 3, and legs of lamb of all 8 lambs.     

Intrauterine transmission of ovine progressive pneumonia virus

Ovine fetuses, newborn lambs, and ovine colostrum were examined for ovine progressive pneumonia virus. The lambs and colostrum were also examined for specific antibody. Virus was isolated from 1 fetus, from 2 newborn lambs, and from most samples of colostrum. The fetus was about 100 days old and was carried by a seronegative ewe in contact with seropositive sheep. Both newborn lambs were carried by seropositive ewes. One lamb was dead at birth; the other lamb was normal and had not nursed. Antibody specific for the virus was present in the colostrum of 12 of 14 seropositive ewes and in the serum of 8 of 11 lambs that had nursed seropositive ewes, but not in the serum of lambs that had not nursed.     

Response of immune and susceptible ewes to infection with Toxoplasma gondii

Inocula containing 75, 250 or 1000 Toxoplasma gondii tissue cysts were used to infect seronegative gimmers and seropositive ewes in the fourth month of pregnancy. The seronegative gimmers developed typical toxoplasma infections at all dose levels. Four of them aborted and the surviving lambs showed rising indirect haemagglutination titres in the first two to three months of life indicating congenital infection. The seropositive ewes showed no response to challenge, all their lambs survived and there was no serological evidence of congenital infection. Indirect haemagglutination titres in the seropositive ewes remained unchanged throughout the experiment, titres in the gimmers rose sharply from the 10th day after infection and by three months were the same as those in the ewes.     

Epidemiologic study of toxoplasmosis on a sheep ranch

An epidemiologic study was done on a ranch in northern California on a flock of ewes that had a history of abortions, mummified fetuses, weak or stillborn lambs, and failure to conceive. Of 56 ewes tested, 33 (59%) had serum agglutinating antibodies against Toxoplasma gondii, with an unusually high proportion of high titers. Over a 2-year-period, reproductive problems were higher (39% to 42%) among the seropositive ewes than among the seronegative ewes (9% to 33%). Of 89 sera received from persons and 7 species of animals on the ranch, 44 (49%) were found to be seropositive to T gondii, including seropositive members of a family of 6. The rancher's wife and teenage daughter, both of whom were involved with lambing, had serum titers exceeding 4,096. Other members of the family not involved with lambing were seronegative by the indirect hemagglutination test. The 2 infected persons are known to have come in contact with placentas, birth fluids, fetuses, and colostrums from these infected ewes.     

Trial of a novel experimental Toxoplasma iscom vaccine in pregnant sheep

Fifteen vaccinated ewes (group 1) and 13 unvaccinated ewes (group 2) were each challenged orally with 2000 sporulated Toxoplasma gondii oocysts at 91 (+/- 1) days' gestation. Another four pregnant ewes acted as unvaccinated unchallenged controls. Lamb mortality in group 1 was 36.4% after a mean gestation of 141 days while in group 2 it was 64.7% after a mean gestation of 131.5 days. These differences were not statistically significant. However, substantially more specific antibody was detected in precolostral sera from live lambs from vaccinated ewes than in live lambs from unvaccinated ewes in group 2.     

Colostrum-derived antibodies to Cowdria ruminantium in the serum of calves and lambs

Antibodies to Cowdria ruminantium were detected in the serum of calves born from artificially immunized heifers, by means of the indirect fluorescent antibody test, only for as long as 4 weeks after birth. Lambs born from artificially immunized ewes, however, were still serologically positive at 8-12 weeks of age. Much higher antibody titres were recorded in the sera of ewes and their lambs than in that of heifers and their calves.     

Leptospiral antibodies in the breeding goat population of Poland

In 2007, a survey was conducted on the prevalence of antibodies to 19 Leptospira serovars in goats in Poland . Sera were collected from adult females of all 49 breeding goat herds in Poland by applying simple random sampling. In total, 736 sera were tested by the microscopic agglutination test. A herd was considered seropositive if at least one goat with a titre of 100 or more was detected. Herd-level seroprevalence of Leptospira was 89.8 per cent and individual-level seroprevalence varied from less than 1.0 to 85.0 per cent among the herds. Antibodies to Leptospira serovars Zanoni, Bratislava, Autumnalis, Australis and Javanica were most frequently detected. Although 40.3 per cent of seropositive goats had high antibody titres (≥ 400), suggesting recent infection, no relationship with abortions or other clinical manifestation of leptospirosis in goats was detected.     

Survey of Toxoplasma antibodies among sheep in western United States

A survey was conducted to determine the prevalence of toxoplasma antibodies among breeding ewes and among lambs slaughtered for food in western United States. Each serum was tested by the indirect hemaglutination method, using microtiter technique. Agglutination (greater than or equal to 2 +) at the 1:64 dilution was considered to be a positive reaction. Of 2,164 ewes from 18 flocks tested in California, 523 (24%) were seropositive for Toxoplasma gondii, with prevalence rates among flocks ranging from 4 to 51%. In 9 of those flocks, 1,495 ewes were stratified by whether ewes had lambed or were barren. On an overall basis, the antibody prevalence was similar (about 25%) in both groups, but there was a significant difference (P less than 0.05) in 1 flock in which 30% of the nursing ewes were seropositive, compared with 21% of the barren ewes. Of 1,056 market lambs from 19 lots tested, 85 (8%) were seropositive. The antibody prevalence in lambs tested at slaughter in California, by state of origin, were: Oregon, 11/51 (22%); Nevada, 32/159 (20%); Idaho, 12/147 (5%), and California, 30/699 (4%).     

Toxoplasma gondii infection in sheep from Haute-Vienne, France: seroprevalence and isolate genotyping by microsatellite analysis

Ingesting meat of free-range livestock, mainly sheep, is associated with human toxoplasmosis in European countries. Data on Toxoplasma gondii infection in French ovine livestock are relatively scarce. Sera from 164 lambs and 93 ewes slaughtered in Haute-Vienne district, France, were tested by a direct agglutination test. Antibodies to T. gondii were found in 36 (22.0%) lambs and in 61 (65.6%) ewes. In addition, to attempt parasite isolation for genotyping, hearts from 50 other ewes were obtained from a local slaughterhouse, and were screened by a direct agglutination test. T. gondii was isolated in 8 of 30 seropositive hearts bioassayed in mice. All isolates were type II by genetic characterization at five microsatellite loci (TUB2, TgM-A, W35, B17, B18). These results indicate that bovines slaughtered in France may be highly infected by T. gondii with a potential risk of parasite transmission to humans by consumption of undercooked meat. Multilocus microsatellite analysis shows the predominance of type II in sheep as previously described in humans.     

Survey to determine the seroprevalence of Toxoplasma gondii infection in British sheep flocks

A serological survey of Toxoplasma gondii infection in adult breeding sheep in Great Britain was conducted using surplus sera taken during a seroprevalence study of Brucella melitensis in 2009. Of the 3539 sera collected from 227 flocks, 2619 (74 per cent) were found to be positive for T gondii specific antibody when tested using latex agglutination. Multilevel logistic modelling suggested that the likelihood of infection increased with age and this effect appeared to be amplified in animals vaccinated against T gondii. The model also indicated that the odds of sheep being seropositive were increased on premises where cattle were also kept. These results suggest a high level of Toxoplasma infection in breeding sheep in Great Britain and provide further evidence to suggest that postnatal infection is more common than congenital infection in sheep.     

Pestiviral infections in sheep and pigs in Northern Ireland

Serological surveys were carried out to determine the prevalence of pestiviral infections in sheep and pigs in Northern Ireland. Sera from 918 ewes in 92 flocks from 10 regions were tested by ELISA for antibodies to border disease virus and positive results were obtained from 49 ewes (5.3 per cent) in 28 flocks (30.4 per cent). There were highly significant geographical variations in its flock prevalence ranging from 0 per cent in the Enniskillen region to 70 per cent in the Coleraine region. There was no significant association between the proportion of seropositive flocks and the presence of cattle on the farm (P = 0.583). In the positive flocks, the average rate of seroprevalence was 17.5 per cent, and the highest was 40 per cent. Comparative neutralisation studies on 14 positive sera with bovine viral diarrhoea virus type I (BVDV I) and border disease virus revealed higher titres (> or = four-fold) to BVDV I in all cases. Only one positive result was obtained when fluids from 186 aborted ovine fetuses were tested for border disease virus by ELISA. Serum samples from 680 pigs in 46 herds were tested for virus neutralising antibodies to border disease virus. Twenty sera (2.9 per cent) were cytotoxic, and only one of the remaining 660 sera gave a positive result. This sample tested negative for classical swine fever by ELISA, and comparative neutralisation studies showed that it had a four-fold higher titre to BVDV I than to border disease virus.     

Experimental infection of the udder of ewes due to Mycoplasma bovis

Twelve freshly lactating ewes were experimentally infected with 2 Mycoplasma (M.) bovis strains via the teat canal in the left udder. The M. bovis infection produced a febrile clinical mastitis in all infected animals. M. bovis could be re-isolated regularly from the experimentally infected udder halves and the infection spread to the other halves. Some contact animals and 4 suckling lambs became naturally infected. Antibody titres were detected by means of the indirect hemagglutination test in blood sera 2 to 3 weeks post infectionem. The pathological lesions were similar to those of the M. bovis mastitis of cows. By the end of the trial the ewes had recovered from the clinical mastitis.     

Serodiagnosis of postnatally and prenatally induced toxoplasmosis in sheep

Nineteen pregnant (45 to 90 days of gestation) and 9 nonpregnant ewes were inoculated orally with 1,000 or 10,000 oocysts of Toxoplasma gondii. Pregnant ewes were euthanatized at days 14 (2 ewes), 21 (1 ewe), 23 (1 ewe), 28 (2 ewes), 35 to 42 (6 ewes), and 49 to 62 (6 ewes), and antibody titers in fetal and maternal sera were assayed, using the modified agglutination, latex agglutination, indirect hemagglutination, and dye tests. Although all ewes developed antibody titers of greater than or equal to 1,024 within 28 days after inoculation, fetuses were seronegative up to 28 days, using the modified agglutination test. Toxoplasma gondii antibodies were found in fetuses, using the modified agglutination and dye tests 35 days after ewes were inoculated. Latex agglutination and indirect hemagglutination tests were insensitive for detection of T gondii antibodies in ovine fetal sera. Toxoplasma gondii antibody titers in nonpregnant ewes were similar to those in pregnant ewes. Passively acquired T gondii antibodies from the colostrum decreased from 1,024 to less than 16 between 49 and 56 days of age in 1 lamb and between 62 and 106 days in its twin.     

ELISA for assessing Toxoplasma gondii antibodies in pigs

The ELISA technique was applied to assess Toxoplasma gondii antibodies in pigs. Among 925 swine examined 36.4 per cent of the animals were seropositive. Serum titres ranged from 100 to 3,200.     

Sarcocystosis in lambs]

We studied the problems of sarcocystosis of lambs in regard to the transfer of antibodies over ewes to lambs. Antibodies in the blood serum of 26 ewes found out by help of indirect immunofluorescent reaction (NFR) varied within the range from 640 to 5120 titres, while in six cases their level was higher than in blood. In none of new-born lambs there were proved antibodies to the sarcocystosis before the drinking of colostrum but three days later we already detected antibodies in the dilution 1:4 to 1:128. Then we studied the titre dynamics of antibodies in weaned lambs. In the age of 10-18 weeks we proved only low titres of antibodies, from the 20th to the 24th weeks the titres gradually increased and from the 26th to the 30th weeks the level of antibodies increased significantly (5120 titres) with its maximum on about the 28th week. Animals had no clinic symptoms of disease. In the other part of the work we examined the muscular substance of 342 lambs, killed in the slaughter house, by a digestive method and we carried out the blood serologic examination (NFR). Microcysts were found out in 35.67% of lambs while macrocysts were so in none of them. Specific antibodies of sarcocystosis were detected in 94.44% of young animals. A high discrepancy of the both methods (61.69%) in young animals is a result of a significant antibody reaction at still undeveloped muscular cysts.     

Placental transfer of specific antibodies during ovine congenital toxoplasmosis

The passage of non-Toxoplasma antibodies from dam to fetus through damaged placenta was studied in sheep inoculated with Toxoplasma gondii. Six ewes were inoculated with chicken globulins and Leptospira bacterins 2 months before oral inoculation with Toxoplasma gondii oocysts. Ewes were euthanatized between 42 and 62 days after T gondii inoculation. Antibody titers against chicken globulins, Leptospira spp, Haemonchus contortus, Sarcocystis spp, and T gondii were measured in the maternal and fetal sera. All ewes became infected with T gondii and had grossly visible necrotic foci in the placentas, and T gondii antibodies were found in the fetuses and the ewes. Appreciable amounts of antibodies to Haemonchus contortus, Sarcocystis sp, Leptospira spp, and chicken globulins did not cross the placental barrier. Seemingly, serologic examination of the fetus was reliable for the diagnosis of ovine congential toxoplasmosis.     

Seroprevalence of antibodies to Neospora caninum in Belgian dogs

Sera from 300 dogs from Ghent and Antwerp were tested for antibodies to Neospora caninurn using an Indirect fluorescent antibody test. Overall, 11 per cent (995 to 13 per cent; confidence interval of 95 per cent) of dogs were seropositive, at titres of 1:50 to 1:800. No sex or breed differences were detected, but there was an Increase In seropositivity with age.