75 Present address: 1 Senior Scientist (Veterinary Medicine) (asitmed2000@yahoo.com, 2 Senior Technical Officer (hussainmokhtar61@gmail.com), 3 SRF (lordchinmoy @gmail.com), 4,5,7,8,10 Scientist (sanjit.ndri@gmail.com, juwarvet_dol@yahoo.co.uk, jode.vet@gmail.com, sourabhd1 @rediffmail.com, drtapas007@rediffmail.com), 6 Principal Scientist (debasis63@rediffmail.com), 9 Senior Scientist (vpaul.nrcy@gmail.com), 11 Director (sm_deb@yahoo.com), ICAR-NRC on Yak. Yak (Poephagus grunniens L.), a unique multipurpose bovid, is reared mostly by the poor and marginal tribal farmers of rural and remote hilly regions at an altitude of 3000-4500m above sea level. In the Peoples Republic of China, Mongolia, Bhutan, Nepal, Russia and India, yaks are farmed even at 5000m above sea level (Weiner et al. 2003, Bandyopadhyay et al. 2007). About 90% of yak populations of the world inhabit the Qinghai-Tibetan Plateau in China, where they are of high economic importance to native herdsmen (Lie et al. 2008). Amongst infectious diseases brucellosis and infectious bovine rhinotracheitis (IBR) are known to cause reproductive problems in the form of abortions and subfertility in dairy animals worldwide. Brucellosis is a well-known zoonotic disease that causes huge economic losses to dairy farmers through abortion and other reproductive failure (Dhand et al. 2005). Infectious bovine rhinotracheitis (IBR) is an important emerging disease of livestock caused by bovine herpes virus- 1 (BHV-1). Infection by BHV-1 causes different clinical syndromes including vulvovaginitis, respiratory disease, pustular balanoposthitis, infertility, abortion (Radostits et al. 2000), keratoconjunctivitis (Bandyopadhyay et al. 2009a) in a range of domestic and wild cattle, yak, mithun, goat, sheep and camelid (Campos et al. 2009, Rahman et al. 2007, Rajkhowa et al. 2004). Previous studies have measured the sero-prevalence of brucellosis and BHV-1 in yak from India (Bandyopadhyay et al. 2007) and China (Xulong et al. 2011), however these studies did not correlate with the seroprevalence levels with cases of abortion in the different stages of pregnancy. In this study the levels of seroprevalence in yak for Brucella and BHV-1 were correlated to levels of abortion. Short Communications Indian Journal of Animal Sciences 85 (7): 751–754, July 2015/short communication High seroprevalence of bovine herpesvirus-1 and Brucella abortus in yak populations of Arunachal Pradesh, India, correlates with abortion A K BERA 1 , M HUSSAIN 2 , C MAJI 3 , S MAITI 4 , J DOLEY 5 , D BHATTACHARYA 6 , J BAM 7 , S DEORI 8 , V PAUL 9 , T K BISWAS 10 and S M DEB 11 ICAR-National Research Centre on Yak, Dirang, West Kameng, Arunachal Pradesh 790 101 India Received: 21 January 2015; Accepted: 8 March 2015 Key words: Abortion, Brucella, IBR, India, Seroprevalence, Yak Farmed and free-ranging yaks from the West Kameng and Tawang districts of Arunachal Pradesh, India were selected for the study. Serum samples (328) from yak (134 male and 194 female) that were collected for detection of antibodies against Brucella and BHV-1. A detailed history on abortion in these yaks revealed that 102 of the yaks had aborted for a total of 132 times in the past. Blood samples were collected from the yaks by venipuncture and serum was separated using standard procedures. Serum samples were stored at -20°C.Testing for antibodies to Brucella abortus and BHV-1were carried out using an AB-ELISA kit procured from the Project Directorate on Animal Disease Monitoring and Surveillance, Bengaluru, India. The AB- ELISA was performed following the methodology as described. Briefly, the test and control (strongly positive, moderately positive and negative) sera diluted in blocking buffer containing 1% gelatin and 0.1% Tween-20 in 0.01 M PBS were added to respective wells in duplicate and incubated at 37°C for 1 h with periodic shaking. The plates were washed and then 100ìL biotinylated anti-bovine IgG (1:30,000 diluted in blocking buffer) was added to each well and incubated for 1 h at 37°C. After washing, the plates were incubated with 100 ìl of avidin-horseradish peroxidase conjugate (1:15,000 diluted in blocking buffer) followed by incubation for 30 min and 20 min for brucellosis and BHV-1 respectively at 37°C. The plates were washed again and treated with 100 µl of substrate chromogen complex (100 µl of O-phenylene diamine dihydrochloride with 5 µl of 30% H 2 O 2 ) and were incubated for 10 min at room temperature. Finally, the reaction was stopped by 50 µl of 1 M H 2 SO 4 . Absorbance was taken at 492 nm and percentage positivity (PP) was calculated using the formula given below. PP (%) = OD of the test well × 100 Median OD of the strong positive sample A value greater than or equal to 40 was considered positive. Out of the 328 serum samples, 32.92% tested positive for Brucella, which comprised of 20.37% male and 79.63%