PCR associated with agar gel immunodiffusion assay improve caprine arthritis-encephalitis (CAEV) control

Abstract

Caprine arthritis-encephalitis (CAE) is a multi-systemic viral syndrome in goats caused by small ruminant lentivirus (CAEV). The control measures prescribed for CAEV control are based on the identification of infected animals through a suitable serological test. The aim of this work was to improve the CAE control measures through the association of indirect (agar gel immunodiffusion-AGID) and direct (PCR) assays to CAEV diagnosis. Thirty-nine kids born to AGID-seropositive dairy goats were separated from their dams immediately after birth, fed heat-treated colostrum from AGID-seronegative goats and then after pasteurized goat milk. AGID was performed at birth before colostrum, at 9 and 12 months, and the AGID-seropositive animals were segregated. Seronegative goats were also submitted to PCR to detect proviral DNA in blood, and the positives were isolated. A study of accumulated residual negativity was performed using a 95% confidence limit rate. During the 12 month experimental period no clinical signs of CAEV were observed. At the end of that period 34 animals remained ACID-seronegative to CAEV, corresponding to 87% accumulated residual negativity. When submitted to PCR, 4 of the 34 ACID-seronegative animals showed positive results, leading to a 77% final accumulated negativity rate with 64-90% confidence limits. We conclude that the classical management practices recommended for CAEV control are insufficient in CAEV eradication programs and that PCR may be a useful tool for decreasing the risk of breeding AGID false negative animals (CAEV carriers). (C) 2008 Elsevier B.V. All rights reserved.