THE PERFORMANCE OF BLOOD DIRECT AFRICAN SWINE FEVER POLYMERASE CHAIN REACTION DIAGNOSTIC METHOD IN AN ENDEMIC SETTING

Abstract

African swine fever (ASF) is a highly contagious viral swine disease. It’s lethality rates range between 90-100% in the affected animals. ASF outbreaks cause severe financial constraints for traders and farmers of swine. ASF has neither treatment nor vaccine interventions. Successful control of ASF in some areas has largely depended on accurate diagnosis and implementation of strict bio security measures. ASF is diagnosed using clinical symptoms, antibody detection in serum and virus detection in blood, serum or organ tissues. Polymerase Chain Reaction (PCR) is currently the most accurate recommended test for diagnosis of African swine fever virus (ASFV) according to the Office International des Epizooties. PCR methods are effective but are still expensive hence not regularly used for diagnosis work in laboratories in poor and endemic countries. This study evaluated the performance of the Blood Direct ASF PCR diagnostic assay in an ASF endemic country and compared results to two established PCR methods; the Real Time and Conventional ASF PCR methods. Samples were collected during an outbreak in eight districts of Uganda and tested for ASFV using the Blood Direct, Real Time and Conventional PCR assays. Selected positive samples were amplified for 3 different ASF fragments P72, P54 and CVR. Amplified samples were purified and sequenced. The sequences were compared with known ASFV genotypes. The Blood Direct PCR method was found to have the shortest procedural time, highly specific, and the cheapest of the PCR assays under comparison. Of the 135 samples,74 samples tested positive for the ASFV on all methods. 74, 6 and 22 samples were positive on the Blood Direct, Real Time PCR and Conventional methods respectively. 61 samples were negative on all methods. The sequences matched ASFV sequences causing previous outbreaks in Uganda and Kenya. However, they were different from those in other neighbouring countries.