Serological and molecular surveillance for influenza A virus in dogs and their human contacts in Oyo State, Nigeria

Evidence of influenza A virus (IAV) infection in dogs, a major companion animal of humans, suggests the possibility that they may constitute a new source for transmission of novel influenza viruses to humans. The potential public health risk posed by this possibility of interspecies spread of IAV between dogs and humans necessitated surveillance for the virus in dogs and their human contacts. Sera from 239 asymptomatic pet and hunting dogs in Oyo state, Nigeria were screened for anti-IAV nucleoprotein antibodies using competitive enzyme-linked immunosorbent assay (ELISA) while haemagglutination inhibiting (HI) antibodies in the positive sera were detected using influenza virus H3 and H5 subtypespecific antigens. Suspensions prepared from 239 and 39 nasal swabs from dogs and human contacts, respectively were tested for presence of the highly conserved IAV matrix gene by reverse transcriptase-polymerase chain reaction (RT-PCR). Only 4 (1.7%) of the 239 sera tested were positive by the ELISA. The HI test confirmed the presence of H3 influenza virus subtype-specific antibodies in one (25.0%) of the 4 ELISA-positive sera with a titre of 1:128 while none was positive for H5 subtype-specific antibodies. All the nasal swabs assayed by RT-PCR were negative for IAV nucleic acid. The detection of IAV antibodies in pet and hunting dogs in this study, although at a low rate, suggests that these dogs could play a crucial role in the zoonotic transmission of influenza viruses especially considering the close interaction between them and their human contacts. Continuous surveillance for IAV among dog populations in Oyo State (and Nigeria) is therefore advocated to facilitate early detection of infection or emergence of novel influenza virus strains that could be potentially harmful to humans and or animals.