Iraqi Journal of Veterinary Sciences, Vol. 35, No. 4, 2021 (657-662) 657 Iraqi Journal of Veterinary Sciences www.vetmedmosul.com Serological and molecular investigations of brucellosis in dairy cows at certain areas of Al-Sulaymaniyah governorate, Iraq K.M. Ridhae 1 and S.A. Hussein 2 1 Directorate of Veterinary Hospital, 2 Department of Basic Sciences, College of Dentistry, University of Sulaimani, Al-Sulaimaniyah, Iraq Article information Abstract Article history: Received July 18, 2020 Accepted April 16, 2021 Available online October 1, 2021 This study aimed to detect Brucella antibodies in the sera of dairy cows and to identify Brucella species in the milk of seropositive cows. A total of 100 sera and 100 milk samples were collected from two 50-cows groups (group 1 with and group 2 without a history of reproductive problems and/or decreased milk production). Rose Bengal plate test and indirect ELISA were used to explore Brucella antibodies in the serum samples and thereafter milk samples of seropositive cows were undergone PCR analysis using Brucella genus specific primers and 3 pairs of species specific primers for identification of B. abortus, B. melitensis and B. suis. The RBPT showed 22 cows were carriers for the Brucella antibodies, 18 in group 1 and 4 in group 2 whereas the iELISA showed only 10 cows out of these 22 cows were positive, 9 in group 1 and only 1 cow in group 2. The PCR assay, which was performed on milk samples of the RBPT positive cows, revealed 18 samples were positive for the Brucella genus and the Brucella abortus species and were negative for Brucella melitensis and Brucella suis species. As a conclusion, the results of this study showed that brucellosis has been encountered in cows with or without a history of reproductive problems, and the RBPT followed by PCR assay for milk samples of the seropositive cows could provide more specific detection than performing either test alone and could be more useful for rapid screening of brucellosis in dairy cows. Keywords: Brucellosis iELISA PCR RBPT Correspondence: S.A. Hussein suha.hussein@univsul.edu.iq DOI: 10.33899/ijvs.2021.127688.1520, ©Authors, 2021, College of Veterinary Medicine, University of Mosul. This is an open access article under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/). Introduction Brucellosis is an animal disease with a significant zoonotic potential worldwide (1) and in Erbil (2). It causes considerable economic losses in the field of animal production due to abortion or the full-term birth of dead or weak neonates and due to the marked reduce in the levels of fertility and milk production (3). It is caused by gram- negative, non-motile, coccobacilli bacterial of the genus Brucella which includes B. abortus, B. melitensis, B. suis, B. canis, B. ovis, and B. neotomae (4). In addition, 2 more species have been reported in marine mammals including B. cetaceae in dolphins and whales and B. pinnipediae in seals (5). There are various serological tests used as screening tests for detection of brucellosis such as Rose Bengal Plate Test (RBPT), Standard Tube Agglutination Test (STAT), Enzyme Linked Immuno Sorbent Assay (ELISA) and several other serological tests (6). However, because of limitations of using these conventional serological tests for confirmatory detection of the fastidious Brucella pathogens, nucleic acid amplification techniques such as the polymerase chain reaction (PCR) offers a reliable diagnostic tool for the detection of brucellosis. This technique is characterized by high sensitivity and specificity, promptness and safety (7). Few studies were conducted on brucellosis in our region (Al- Sulaimaniyah Governorate, Iraq), therefore, the current study may represent a new addition to the information on