Abstract
Prevalence of brucellosis was studied in unvaccinated Changra goats in their native breeding tract of Changthang in the Indian Trans-Himalayan area of Ladakh which represents the western extension of the Tibetan Plateau, an important highland grazing ecosystem. A total of 680 serum samples were collected from 8 different areas including Kharnak, Sumdho, Chushul, Mughlib and Kargyam in the traditional Changra rearing belt, and Digger, Turtuk and Stakna in non-traditional belt. Brucellosis was diagnosed using serological tests viz RBPT, STAT, Dot-ELISA and Plate-ELISA, and serum based PCR. Apparent prevalence was calculated and true prevalence worked out on the basis of sensitivity and specificity for each test. The flock-level prevalence of brucellosis was 80% to 100%. The overall apparent prevalence by RBPT, STAT, Dot-ELISA, Plate ELISA and serum PCR, respectively was 24.85 (95% CI 21.65-28.28), 13.97 (95% CI 11.49-16.80), 26.03 (95% CI 22.83-29.46), 12.21 (95% CI 9.87-14.88) and 14.71 (95% CI 12.15-17.54) and true prevalence worked out on the basis of sensitivity and specificity for each test was 29.45 (95% CI 25.49-33.68), 23.16 (95% CI 18.73-28.21), 18.38 (95% CI 13.05-24.10), 17.19 (95% CI 13.90-20.96) and 15.16 (95% CI 12.53-18.08). The respective overall apparent and true prevalences were higher in traditional areas than in non-traditional areas. Prevalence was significantly (P≤0.05) higher in adult goats (>1 year) when compared with young (

Key words: Changra goats, Brucellosis, RBPT, ELISA, PCR