SEROLOGICAL AND MOLECULAR EPIDEMIOLOGY OF HEPATITIS E VIRUS IN PIGS, PLATEAU STATE, NIGERIA
Globally, there are increasing concerns for the public health implications of Hepatitis E virus (HEV) infection. The disease which was thought to be endemic only in African and Asian countries is now being established to be endemic in developed nations of Europe, America, Australia and Oceania. Animal reservoirs are incriminated in the maintenance and spread of HEV; pigs being the major reservoir.The occurrence of HEV, dynamics of viral shedding and the circulating genotype(s) were examined in this research study. Genomic sequences of Open Reading Frame 2 (ORF2) were analyzed for unique characteristics. Serum and fresh faecal samples from domestic pigs in 10 Local Government Areas (LGAs) were analyzed for the presence of anti-HEV antibodies and viral RNA. In total 500 serum samples were collected from slaughter age pigs at three separate slaughter houses in Plateau state. Anti-HEV antibodies (IgM and IgG) were assessed. Fifty faecal samples each were collected from the following LGAs: Bassa, Barkin-Ladi, Bokkos, Jos-North, Jos-South, Mangu, Shendam, Pankshin, Langtang-North and Langtang-South. In Jos abattoir, 89.1% of the pigs were anti-HEV IgM positive while only 45.3% were IgG seropositive. When stratified by age, pigs <9 months of age were more likely to be IgM seropositive (P>0.05) and but less likely to be IgG positive (P>0.05). By sex, female pigs were less likely to be IgM positive (P>0.05) and there was no association between sex and detection of IgG (P>0.05). By breed, indigenous breeds were less likely to be IgM positive and also less likely to be IgG positive (P>0.05). In Mangu slaughter area, 93.9% of pigs were IgM seropositive while only 51.5% were IgG seropositive. Pigs <9 months old were more likely to be IgM positive (P>0.05) but less likely to be IgG positive. Based on sex, female pigs were more likely to be IgM positive (P>0.05) but less likely to be IgG positive.In Langtang area, 91% of the pigs tested were positive for IgM and 55% positive for IgG. However, pigs <9 months were less ix likely to be both IgM and IgG positive (P>0.05). Based on sex, female pigs were more likely to be IgM and IgG positive (P>0.05). A comparison between breeds could not be performed for IgM, but indigenous breeds were found to be more likely to be IgG positive.HEV RNA was detected in pigs from all LGAs sampled by qPCR, the highest being Langtang-South with 62.8% and Jos-South the least with 2.4%. Quantitatively, Ct ranged between 23.35 and 44.65. In all, 114 faecal samples were HEV RNA positive (25.7%); sequel to nested PCR, only 22 samples displayed clear discreet bands of expected size. Of the 22 samples, 19 partial sequences of the ORF2 were returned; three could not be sequenced. Blast homology searches confirmed the 19 sequences to be HEV and were 92% homologous to a Japanese strain swJ8-5 and 91% with Hungarian strain HEV072/sw/HUN-05. Intra-country HEV sequence diversity was observed among isolates recovered from this study, but all viral isolates were confirmed to be genotype 3 clustering closely to genotype 3 reference strains from the GenBank. Further characterization grouped all sequences from this study to belong to subgenotype 3e together with French, Hungarian, Japanese and UK strains. Amino acid sequence analysis revealed only a few conserved residues and 2 conserved motifs; functional implications of the amino acid residues are unknown as this was not assayed for. The evolutionary divergence of the sequences from Plateau state was estimated and discovered that maximum distance among the strains from Plateau state was 0.8, being the distance between strains from Langtang-South and Bokkos LGAs. The study concludes that HEV is widely spread in Plateau state and the strains identified are the zoonotic genotype 3 strains. It is also concluded that the HEV strains circulating in Plateau state may have been imported from Europe or Asia.