Evaluation of a Voluntary Control Program for the Detection of Bovine Leukemia Virus Antibodies Based on Agar Gel Immunodiffusion Test in Dairy Farms in Costa Rica

摘要

Cattle from 20 dairy farms were serologically tested over a five-year period using agar gel immunodiffusion test (AGIDT) as part of a voluntary Bovine Leukemia Virus (BLV) control program. After five years of removing infected animals from the herds based on BLV-AGIDT serological status, blood samples from 332 cattle in these farms were collected and analyzed side by side by AGIDT and enzyme-linked immunosorbent assay (ELISA) to detect antibodies against BLV. AGIDT detected 29.2% (97) and 16.0% (53) of the animals as positive and weak positive respectively, whereas ELISA detected 58.2% (193) cattle as positive. The prevalence of BLV-antibodies determined with AGIDT in the dairy farms oscillated between 0% and 86%, whereas prevalence determined by ELISA ranged between 28% and 100% in the same farms. Although both techniques showed similarly results in farms with high BLV-prevalence, ELISA detected a larger proportion of BLV-positive, especially in farms with low or no BLV-prevalence based on AGIDT, leading to wrong assumptions in terms of farm level control efforts. Our results strongly suggest that AGIDT alone is inadequate to implement BLV control programs and ELISA is a more adequate test for BLV surveillance and control programs.