Bovine Leukemia Virus Infection in Dairy Cows in Egypt

Abstract

2 Abstract: Bovine leukemia virus (BLV) is a lymphotropic virus that affects cattle. In the current study 240 Holstein, Holstein Friesian and Red Sindhi dairy Cows in Kafr El Shekh, Alexandria and Monofia governorates of Egypt from five dairy farms and at small holder breeders were examined for the presence of BLV. The sera of tested dairy cows were subjected to commercial Agar Gel Immuno-Diffusion (AGID) and ELISA kits specific for BLV antibodies. Also the milk samples were subjected to another commercial ELISA kit for detection of BLV antibodies in milk. Meanwhile, PCR technique was conducted on serum samples for the specific identification of the viral genome. Clinical examination revealed lymph node enlargement which was a predominant sign in 6.25% of animals. In some cases protrusion of conjunctival membrane was found in 1.67% of animals. Lameness and respiratory manifestations, such as rale and dry cough and emaciation appeared in a few cases representing 0.42, 0.83 and 1.25%, respectively. Laboratory results showed that 15.83% of cows were serologically by both tests positive where 4.17% of animals which belonged to different cow's farms were infected with BLV, 11.67% of animals which belonged to small animal holders were infected by BLV. Concerning the disease risk factors, 7.08% of infected animals were 4-6 years and 5.42% were 2-4 years, while 3.33% were less than two years, pointing out that the occurrence of the disease increases with age. ELISA tests in blood showed the same or even upper limit of detection than the same test in milk samples, when the analytical sensitivities were checked reactivity, dilutions of 1:64 and 1:32. PCR confirmed the results of serology but considered more accurate forit detects the viral genome and is more sensitive than serological tests especially in high dilutions which is a serious problem in the used methods.