Isolation, Identification and sero conversion studies on BRSV in Egypt

ABSTRACT

In the present survey 250 nasal swabs and 400 sera samples were collected from calves, feed lot and diary cattle with different ages, seasons and different degree of respiratory signs, for BRSV isolation, identification and serodiagnosis. In addition to 150 calves apparently normal contact animals were examined. The collected samples represented six farms distributed throughout five Egyptian governorates. The obtained results proved that, 5 out 7 virus isolates were from calves 1-6 months old and another 2 isolates from unweaned calves 2-3 weeks old, 6 isolates were detected in spring season while, only one during winter season. Only 3 out of 7 titrated viral isolates were identified as BRSV by SNT and one more by direct FAT. The isolated strains were designated as RBSV Salhai 1994 and RBSV Alexandria 1994. The serodiagnosis results of 400 examined sera samples by SNT and ELISA revealed that 65 [16.25%] and 110 [27.5%] sera samples were positive, respectively. The antibodies titer ranged from 1/8 to 1/64. Maternal immunity through seroconversion study showed a fading of passive immunity completely at 5th month of age