Isolation and molecular genetics of Foot- and-Mouth Disease virus from clinical infections in Nigeria

Abstract

SUMMARY Foot and Mouth Disease virus typed and characterized from field suspected cases was confirmed using RT-PCR, antigen detection ELISA and Cell culture. Total of 54 samples comprising of 12 epithelial tissues and 42 oral swabs were obtained from clinical and recovering cases reported in Abia, Cross- River and Taraba States. Positive samples for RT-PCR were tested on tissue culture. Out of 19 RT-PCR positive samples, 4 grew on cell culture and 15 were negative. Of these15 negative specimen on cell culture 12 were tested with Antigen-detection ELISA and 3 positives were FMDV serotype A, SAT-1 and SAT-2. Positive samples of FMD virus serotypes A and O were grown on tissue culture using IB-RS-2 commercial cell line. On RT-PCR only serotype A was identified, viral genome was extracted and amplified then amplicon submitted for sequencing. Four FMD viruses were isolated and characterized using percentage identity matrix (alignments Clustal W2). They were closely related to one another to the range of 53- 99 % but could not be termed identical viruses. The phylogenetic analysis revealed relatedness to historical isolates from Nigeria (2006), Cameroon 2000, Sudan and Egypt Viruses. This finding reaffirms the nomadic cattle movements in disease transmission and the need for countries to jointly coordinate efforts in FMD control. Non identical virus isolates reveal the diversification of FMD virus types and topotypes in circulation and the complexity of FMD situation. This may be an indication for a more frequent update of the vaccine strains used in local FMD vaccine and adoption of multiple and different strain vaccine in specific areas to progressively reduce the types of circulating viruses.