Epidemiological Investigation Of Sheep Brucellosis In Three Counties Of Gansu Province In 2014

Brucellosis is a zoonosis caused by Brucella. In recent years, there is an upward trend of sheep brucellosis outbreaks in Gansu province. As a consequence, sheep farming and people?s health are under threat. So in this study, epidemiological investigation of sheep brucellosis in three counties of Gansu Province was carried out in 2014.1.To evaluate the performance of Rose Bengal Test(RBT) and indirect ELISA(I-ELISA) in the absence of a gold standard, 176 serum samples of sheep somewhere were tested in parallel by RBT and I-ELISA and data were analyzed by building Bayesian model. The sensitivities of RBT and I-ELISA were calculated as76.5 % and 89.6 % with corresponding specificities of 95.1 % and 93.4 %respectively. The results showed that I-ELISA was more reliable in diagnosing ovine brucellosis.2.A total of 1536 serums sampled from 54 farms in Jingyuan County, Kongtong District and Yongchang County were tested by I-ELISA. The results showed that 55 serums were positive and individual positive rate was 3.58%. 14 farms were positive and group positive rate was 25.93%. The individual positive rates of Jingyuan County,Kongtong District and Yongchang County were 3.35%(18/538), 6.02%(30/498) and1.40 %(7/500) respectively, and the group positive rates of Jingyuan County,Kongtong District and Yongchang County were 22.22%(2/9), 33.33%(11/33) and8.30%(1/12) respectively.3.Three isolates, named GS0250, GS2620 and GS2638, were isolated from aborted fetuses collected from Jingyuan County, Kongtong District and Yongchang County. Traditional typing, AMOS-PCR and MLVA-16 were used to identify the isolates. Quite surprisingly, all the three isolates were determined the same as B.melitensis biovar 3 by traditional method, as B.melitensis by AMOS-PCR based on the same amplified 731 bp special fragment, and as type 0063(1- 5- 3- 13- 2- 2- 3-2- 4- 23- 8- 3- 4- 3- 8- 5) by MLVA typing which was different from all the types of other ninety-three isolates. The present identified type 0063 showed a distantrelationship from others by cluster analysis, suggesting that all the three isolates were introduced from elsewhere and pointed to the same geographic position.