Serological and molecular investigation of canine influenza virus in Plateau State, Nigeria

Canine influenza is a highly contagious respiratory infection of dogs caused by the Influenza A Virus (IAV), characterized by cough, sneeze, nasal secretions, and inappetence. Infections can be mild, severe or fatal. Aquatic birds constitute a natural reservoir for IAV, which is transmitted to terrestrial birds, including poultry. IAV has also emerged in other mammalian species, including humans, swine, horses, and dogs. IAV epidemics in dogs are a recent development. Commonly detected Canine Influenza Virus (CIV) strains are A/H3N2 and A/H3N8 from avian and equine influenza, respectively. Nigeria’s agro-ecology witnessed widespread circulation of avian influenza since 2006, and recent outbreaks of equine influenza in 2018/2019 raise the possibility of inter-species transmission to dogs. To investigate canine Influenza in Plateau State, we collected 113 nasal swabs and 270 sera samples from dogs in clinics, live dog markets, and during dog vaccination campaigns. After extracting nucleic acid with the Qiagen kit, RT-PCR analysed swabs for the Influenza A matrix gene. Sera samples were screened by Enzyme-Linked Immunosorbent Assay before subtyping a cross-section for H3 antibody by Hemagglutination Inhibition. No matrix gene was amplified from extracted nucleic acid from the nasal swabs. Though few sera were reactive to influenza A nucleoprotein, none was positive for influenza A/H3. The H3N8 strain of equine influenza virus first caused an epidemic in dogs in 1999 in the United States. Subsequently, avian-origin H3N2 CIV emerged in dogs in China and South Korea in 2005. Past CIV epidemics arose from a single cross-species transmission of H3N8 subtype from a mammalian intermediate host and the H3N2 subtype from an avian reservoir. Even though this limited investigation did not detect CIV in Plateau State, the potential remains because of the persistent circulation of avian, swine, and equine Influenza in Nigeria, which requires more extensive virological and serological surveillance.