Seroprevalence of antibodies to Neospora caninum and associated abortion in dairy cattle from central Thailand.

A total of 904 sera from dairy cattle in 11 provinces of central Thailand were tested for antibodies to Neospora caninum employing the indirect fluorescent antibody test (IFAT). Fifty four (6%) cattle were positive in IFAT, titres of 1:200 (16 cattle), 1:400 (9 cattle), 1:800 (14 cattle), 1:1600 (7 cattle), 1:3200 (6 cattle) and two positives. No significant difference was observed among the provinces. The seropositivity for Toxoplasma gondii by a commercial latex agglutination test was 4% (2 out of 50) in positive sera, 2.9% (2 out of 69) in negative sera for anti-Neospora antibodies and 3.4% (4 out of 119) in total. The results of the IFAT were not associated with the presence of antibodies to T. gondii in bovine sera. Furthermore, the cause of abortions experienced in neighbouring three areas in the northeast, where pregnant heifers were newly introduced into small-scale farms from the central region, was investigated. The positive rates for anti-N. caninum antibody were 12, 28 and 44% at a cut-off titre of 1:200, and cattle were suspected to be infected after the introduction. In the area with the highest rate, seven out of eight aborting cattle were positive for antibodies to N. caninum while other two areas had similar abortion rates in both negative and positive cattle. However, in the latter two areas, positive rates for Trypanosoma evansi antigen along with parasitaemic animals were observed by an antigen-detection ELISA, but not for the former area. Considering the endemic diseases of the areas, Neospora was presumed to be responsible for the abortions in the former area while the examination results pointed out T. evansi as the most probable cause in the latter two areas. This is the first report of Neospora-associated abortion in Southeast Asia.

Preliminary study of nematode infections of cattle in the six provinces of Thailand in the dry season.

Fecal nematode egg counts and serum pepsinogen concentrations of cattle were determined in six Provinces of the northern (Chiangrai and Lampang), north-eastern (Khonkaen, Mahasarakham and Nakhonratchasima) and eastern (Chonburi) parts of Thailand in the dry season. Nematode eggs were detected in 82% of animals examined. Serum pepsinogen concentrations ranged from 78 to 2,951 (mean 934) mU tyrosine. Animals in Chonburi Province had higher mean values for both egg counts and serum pepsinogen concentrations than animals in the other Provinces. Two calves in Khonkaen and Mahasarakham Provinces were found to be heavily infected with Strongyloides papillosus, with 10,840 and 9,593 eggs/g feces. The source and route of S. papillosus infections remained unknown.

Diagnosis of cattle fasciolosis by the detection of a circulating antigen using a monoclonal antibody.

A monoclonal antibody (MoAb) 1C12 that reacts with a 66 kDa surface tegumental (ST) antigen of adult worms of Fasciola gigantica was used to detect circulating antigen in sera of experimentally and naturally infected cattle. A combination of rabbit anti ST-antigens and MoAb 1C12 were used to capture and detect the circulating antigen in sandwich ELISA. The dilutions of 1:1,000 of rabbit anti ST-antigens and 1:100 for MoAb 1C12 were used to reduce cross-reactivity with other trematodes' antigens. The circulating antigen of F. gigantica was demonstrated in sera of all experimentally infected animals as early as the first week after the infection, and it remained detectable until the experiment was terminated at week 32 after the infection. Of the 97 serum samples from naturally infected cattle, the sensitivity of 86.6% was observed when the cut-off point was calculated from 32 serum specimens from uninfected control calves. The sensitivity increased to 100% when the commercial fetal calf and trematode-free baby calves sera were used for calculation of the control cut-off point. Based on these results, the combination of rabbit anti ST-antigens and MoAb 1C12 sandwich ELISA appeared to be sensitive, specific, and applicable in the immunodiagnosis of fasciolosis in cattle for epidemiological study and monitoring of chemotherapeutic efficacy.