Enzyme-linked immunosorbent assays using antigens extracted from Brucella abortus with n-lauroylsarcosine differentiated natural Brucella-infected animals from Brucella-vaccinated or Yersinia enterocolitica O9-infected animals. A field trial in Mongolia showed cattle, sheep, goat, reindeer, camel, and human sera without infection could be distinguished from Brucella-infected animals by conventional serological tests.Brucellosis is a worldwide infectious disease of domestic animals, and the causative agent, Brucella spp., is transmitted to humans by contact with infected animals or by contaminated dairy products (4). Serodiagnosis of acute and recent infections with Brucella and Yersinia enterocolitica O9 by using the commonly used microagglutination assay is seriously impaired by the well-documented and strong serological cross-reactivity between these bacteria (2, 6-11, 13, 14). The Rose Bengal test and complement fixation test are the most accepted tests worldwide (5). These tests are based on a reaction between a Brucella whole-cell antigen and antibodies produced in response to the infection. Differentiating between animals infected with Brucella and animals vaccinated against Brucella is too difficult by conventional serological tests, such as the Rose Bengal test, tube agglutination test, and complement fixation test (13), because vaccinated animals have a high titer against Brucella antigens. Therefore, we tried to find an easy serological method to differentiate Brucella-infected animals from vaccinated or Y. enterocolitica O9-infected animals.To differentiate natural Brucella-infected animals from Y. enterocolitica O9-infected animals, antigens extracted from the virulent Brucella abortus strain 544 (15) with n-lauroylsarcosine were used for an enzyme-linked immunosorbent assay (ELISA), and the specificity of the ELISA was tested. The antigens were extracted as follows. B. abortus strain 544 cells were grown to A 600 ϭ 3.0 in brucella broth (Becton Dickinson, Sparks, Md.), and bacterial cells were harvested by centrifugation and washed once with distilled water (DW). For whole bacterial cell antigens, bacteria were inactivated by formalin (0.5% final concentration) and were concentrated to 1.5 (the optical density at 600 nm [OD 600 ]) in DW at this step. For n-lauroylsarcosine-extracted antigens, n-lauroylsarcosine (0.5% final concentration) was added to the bacterial suspension and the cells were incubated at room temperature for 30 min with shaking. The bacterial suspension was centrifuged and filtrated, and then the supernatant was transferred to a new centrifuge tube for use with the antigens. The protein concentration of antigen was checked by Bio-Rad protein assay, and the antigen was also checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining. Western blotting was done with anti-B. abortus or anti-Y. enterocolitica O9 rabbit serum for each preparation. To coat the antigens on Immuno plates for the ELISA, 50 l of the antigens (sarcosine extracts; 4 g/ml...
Brucellosis is an important zoonosis, and serological surveillance is essential to its control. However, cross‐reactions of attenuated live cells of Brucella abortus strain S‐19 and B. melitensis strain Rev‐1 with Yersinia enterocolitica O9 or vaccinated animal sera interfere with accurate serological diagnosis by the Rose Bengal test (RBT). Therefore, we used ELISA with sarcosine extracts from the virulent B. abortus strain 544 to eliminate false‐positives among RBT positive‐sera. A total of 697 serum samples were collected in Mongolia from humans and animals in 23 nomadic herds. The herds were classified into three groups as brucellosis‐endemic (BE), brucellosis‐suspected (BS), or Brucella‐vaccinated (BV). The number of 295 animals (43.0%) was positive by RBT, but 206 (69.8%) of these were positive according to ELISA; therefore, 30.2% of the RBT‐positive sera were found to be false positives. The false positive samples for RTB represent 4.1%, 27.4%, and 68.2% of the animals from the BE, BS, and BV herds, respectively. In addition, 32% of RBT‐positive human sera were also false positives. Thus, our ELISA would be more specific than RTB and useful for epidemiological surveillance for brucellosis.
because of the poor surveillance systems for recording animal casualities. Most of the reported animal cases were in domestic goats and only a lesser number were in domestic cows and dogs. In addition, two cases of deaths in humans and eight cases of deaths in animals, which were attributed to rabies virus infection had history of stray dog bites. Among the animal deaths due to rabies, there were five goats, two cows and one domestic dog.Conclusion: Unless the local civic bodies undertake adequate measures to control the numbers of stray dogs, changing the public perception as well as opinion against the mass killings will remain an uphill task.
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