ANTIGEN DETECTION AND MOLECULAR CHARACTERIZATION OF FOOT AND MOUTH DISEASE VIRUS FROM OUTBREAK CASES IN ETHIOPIA
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2019-06
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Abstract
Foot and mouth disease is a highly contagious viral disease of cloven-hooved animals with significant economic impact. Outbreak investigation was conducted in Tigray, Oromia and SNNPs regional states of Ethiopia from September 2018 to May 2019. Purposive sampling was conducted in the respective districts and kebeles where the outbreaks occurred. A total of 215 animals were examined for the presence of typical clinical signs, 55 animals (25.58%) showed clinical signs and lesions suggestive of FMD. Totally 55 epithelial tissues and 8 oral swab samples were collected from suspected cases and submitted to the NAHDIC, Sebeta, Ethiopia for virus isolation, serotype identification and molecular characterization. Culture positive FMDV isolates were sent to WRLFMD, Pirbright, UK for sequencing. Of the 63 collected samples, 53 samples (84.13%) were positive for the FMDV genome by rRT-PCR with Ct values ranging from 15.06 to 31.19. Out of 34 cultured samples, 76.47% (n = 26) exhibited cytopathic effect in BHK-21 cell and the viruses were isolated. In the current study, serotypes of O (53.85%) and A (46.15%) were identified by antigen detection ELISA. Phylogenetic analysis of VP1 sequences from these viruses were used to determine the relationships from Ethiopia and other viruses retrieved from GenBank. Phylogenetic analysis of the VP1 nucleotide sequences showed that the type O viruses belonged to the EA-3 and EA-4 topotypes. Serotype A isolates belonged to genotype IV of African topotype. Amino acid substitutions were observed at critical residues of antigenic sites of serotype O at position 45 and 48 of VP1. Amino acid variations also identified in the main antigenic sites between the vaccine strain and field isolates of FMDV serotype A at positions 45, 140, 141, 143, 149 and 157. Similarly a total of 12.68% and 15.96% amino acid variations were observed in serotype O and A, respectively, in different sites of the VP1 gene with reference to the vaccine strain of the country. Therefore, regular investigation of FMD outbreaks to have more detailed information about the serotypes and topotypes circulating in Ethiopia is important for development of effective vaccine for the controlling of the disease.
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FMDV, molecular characterization, Outbreak investigation