Neutralising antibody response in cattle after vaccination with monovalent modified-live vaccine against bluetongue...

The antibody response following bluetongue (BT) vaccination under both field and experimental conditions, and the duration of colostral antibodies in calves born from vaccinated dams, were evaluated. To this end, 1 005 animals of various breeds and ages were selected at random from 10 herds in the Sardinian province of Oristano. During the first year of the vaccination campaign, the animals selected were vaccinated against BT virus (BTV) serotype 2 between July and August 2002. Blood samples were taken from all animals monthly for three months after vaccination and tested for the presence of BT antibodies using the competitive enzyme-linked immunosorbent assay (c-ELISA) and the virus neutralisation (VN) test. Serological results from field vaccinated animals were compared with those obtained following the vaccination of five animals under experimental conditions. Out of 1,005 animals, 994 (98.1%) developed BT antibody following vaccination whereas antibody was detected in all cows vaccinated under experimental conditions. Both groups showed the highest median titres of 1:160 after two months. To assess the duration of colostral antibodies in calves born from vaccinated dams, the sera of 47 calves were screened using the c-ELISA and VN test. Calves were divided into three age groups: Group A included 22 calves aged 1 to 25 days, Group B 13 calves aged 26 to 39 days and Group C 12 calves aged 40 to 60 days. Antibody was detected in calves in Groups A and B (68.2% and 46.1%, respectively) whereas the calves in Group C were serologically negative.