Comparison of immunoperoxidase monolayer assay, polymerase chain reaction and haemadsorption tests in the detection of African swine fever virus in cell cultures using Ugandan isolates

Abstract

African swine fever (ASF) is a devastating viral disease of pigs and is among the major hindrances to pig industry in sub-Saharan Africa including Uganda. The aim of this study was to compare immunoperoxidase monolayer assay (IPMA) to PCR in detection of ASF virus in infected macrophage cultures and to categorize ASF viral isolates in Uganda by haemadsorption assay. Field strains of ASF virus were isolated from infected pigs into swine alveolar macrophages culture. The effect of the inocula on the cell culture was monitored daily and the presences of ASF virus in the inoculated macrophages were detected using PCR and IPMA. The isolates were then categorized by haemadsorption assay. 58.8% of the samples had ASF virus DNA and ASF virus was isolated from 27% of the samples. IPMA detected ASF viral antigens in 80% of the inoculated macrophages culture 48 h post infection compared to the 100% by PCR. 95% of the virulent ASF viral isolates from Uganda were haemadsorbing. This study makes the first attempt to use IPMA and haemadsorption assay for the detection of ASF virus and categorization of the African swine fever virus (ASFv) field isolates into haemadsorbing and non-heamadsorbing in Uganda, respectively. The study demonstrates that IPMA is an appropriate option to PCR and could be used to detect ASF virus in cell cultures. It is recommended that the genome of the non-haemadsorbing ASF viral isolates could be sequenced and compared with that of haemadsorption (HAD) isolates to identify molecular peculiarities and markers of these two categories of ASFv. Key words: African swine fever (ASF), African swine fever virus (ASFv), Immunoperoxidase Monolayer Assay (IPMA), swine alveolar macrophages, haemadsorption (HAD) Polymerase Chain Reaction (PCR).