Comparative Study On Conventional And Polymerase Chain Reaction Based Diagnosis Of Bovine Brucellosis

Brucellosis is a widespread zoonotic disease which is caused by species of the genus Brucella. Diagnosis of brucellosis is the basic of any control program. Many methods are widely used for the diagnosis of the disease. Recently molecular techniques were introduced in the field of brucellosis. This study was designed to isolate Brucella from milk samples and to evaluate the polymerase chain reaction as diagnostic method for brucellosis and to compare it with other conventional methods routinely used for the diagnosis of the disease. One hundred and sixty dairy cows from 12 farms from different localities in Khartoum State were examined for the presence of brucellosis. 160 milk samples and 160 serum samples were collected. All milk samples were examined bacteriologically for presence of the Brucella, 11 samples (6.9%) revealed colonial growth indicative to Brucella species. 149 (93.1%) showed no colonial growth. The 11 isolates were identified as B. abortus. To compare polymerase chain reaction (PCR) with other tests, all milks samples were examined by PCR, Milk ring test and Modified Ziehl Nielsen Stain (MZN). Twenty (12.5%) milk samples showed Brucella species under microscope using MZN, although only 11 (6.9%) showed growth onto tryptose soy agar and Brucella media. 54 (33.8%) samples were showed positive reaction by MRT, while PCR detected brucella DNA in 33 (20.63%) milk 16 samples. On the other hand, 29 (18.13%) serum samples showed agglutinations using Rose Bengal plate test. The sensitivity and specificity of these tests were evaluated. High sensitivity was reported for MRT and PCR (85% and 75%, respectively). While high specificity was obtained for PCR and RBPT (87.1% and 85.5%, respectively). The prevalence of bovine brucellosis was found to be 12.5% for all farms examined. Most of the cows examined appeared healthy (97.5%), however application of vaccination program was found very limited. Furthermore, the level of hygiene was poor in most farms. A positive correlation was found between mastitis and status of hygiene to the presence of bovine brucellosis (P< 0.05). In contrast, no relationship was observed between the disease and calving number (P> 0.05). It could be concluded that B. abortus could be isolated from milk samples and PCR showed high sensitivity and could be quick and useful method for diagnosis of bovine brucellosis