Human parechovirus genotypes -10, -13 and -15 in Pakistani children with acute dehydrating gastroenteritis

Abstract

Human parechoviruses are known to cause asymptomatic to severe clinical illness predominantly respiratory and gastroenetric infections. Despite their global prevalence, epidemiological studies have not been performed in Pakistan. In this study, we retrospectively analyzed 110 fecal specimen and found 26 (24%) positive for viral RNA with HPeV-10 (n = 3, 23%), HPeV-13 (n = 4, 31%) and HPeV-15 (n = 6, 46%) genotypes. Clinical features of patients with different HPeV genotypes were compared. All HPeV positive children were aged ≤4 years (mean 13.92 months). The male-to-female ratio was 1: 1.17 (46.2 vs 53.8%) with significant association (p = .031) to HPeV infectivity. HPeV-10 and -13 were found during summer while HPeV-15 was only detected during late winter season. Disease symptoms were more severe in children infected with HPeV-10 and -13 as compared to HPeV-15. Fever and vomiting were observed in 100% cases of HPeV-10 and -13 while only 17% patients of HPeV-15 had these complaints. Phylogenetic analyses showed that HPeV-10, -13 and -15 strains found in this study have 9-13%, 16.8% and 21.8% nucleotide divergence respectively from the prototype strains and were clustered to distinct genetic lineages. This is the first report of HPeV-15 infection in humans although first identified in rhesus macaques. The arginine-glycine-aspartic acid (RGD) motif present at the C-terminal of VP1 responsible for the viral attachment to cellular integrins was not found in all of these strains. In conclusion, these findings enhance our knowledge related to the epidemiology and genetic diversity of the HPeV in Pakistan and support the need for continued laboratory based surveillance programs especially in infants and neonatal clinical settings. Further, the parechovirus pathogenesis, cross-species transmission and disease reservoirs must be ascertained to adopt better prevention measures.

Figure 1. The distribution of HPeV infections in Pakistan during 2008 is presented with months given on X-axis.

The data labels on Y-axis indicate the number of total and positive samples for each genotype across the year. Total number of cases is indicated by solid black line indicating typical peak season for gastroenteritis in summer (monsoon/rainy season) months. The number of cases positive for each genotype is indicated with different bar-style.

Figure 2. Phylogenetic analysis of human parechovirus strains identified in this study based on the partial VP1 region.

The reference strains and closest match isolates detected through BLAST are given for genetic comparison. The phylogenetic tree with 1000 bootstrap replicates was reconstructed using neighbor joining method and the K-2P model through MEGA 4.0. Taxa with arrow head indicate the prototype strains within each serotype. Black circles indicate the strains found under this study in Pakistan. HPeV-12 and HPeV-7 previously reported from Pakistan are highlighted.