Avian influenza, Newcastle and Gumboro disease antibodies and antigens in apparently healthy wild birds in Kaduna state, Nigeria
Studies on avian influenza and Newcastle disease focus on waterfowls, considered natural reservoirs of these viruses. This study surveyed avian influenza (AI), Gumboro and Newcastle disease antibodies and antigens in birds in live wild bird markets (LWBMs), live poultry markets (LPMs) and free flying in Kaduna State from March to June, 2012. Enzyme linked immunoabsorbent assay (ELISA) and hemagglutination inhibition (HI) tests were used to detect AI viral nucleoprotein and H5- and H7- subtype antibody while Newcastle disease (ND) antibody were detected using HI test. Gumboro disease (GD) antibody was detected by agar gel immunodiffusion test (AGID). Polymerase chain reaction (PCR) was used in the detection of ND and AI viral antigens. Of the 157 birds tested by ELISA, representing 35 species of 27 families 9.2 % had influenza A antibody. About 23.1 % families and 17.6 % species had Influenza A antibody. The families with influenza A antibodies were Anatidae, Ardeidae, Ciconiidae, Columbidae, Numididae and Pynonotidae; and the species were Pychonotus barbatus, Ardea cinerea, Numida meleagris, Streptopelia senegalensis, Anas platyrhynchos and Ciconia ciconia. The AI antibody prevalence was 4.4 % in free flying birds; 17.1 % in LPM and 20 % in LWBM. The AI antibodies prevalence in Kaduna was 14.3 % while carnivorous bird’s prevalence was 16.7 %. All samples positive for influenza A antibodies were negative for H5- and H7- subtype antibodies. None of the 98 birds tested for GD antibodies, comprising 20 families and 26 species had GD antibodies. Of the 196 birds tested for ND antibodies comprising 31 families and 50 species the prevalence was 20.4 % with a mean titre of 8.03 ± 0.27 log2 and 75.0 % of sero-positive birds having antibody titre ≥ 7 log2. Family and species ND antibody prevalence was 45.2 % and 34 %, respectively. Newcastle disease antibodies sero-positive families were Anatidae, Ciconiidae, Cisticolidae, Columbidae, Coraciidae, Jacanidae, Numididae, Passeridae, Phasianidae, Pyenonotidae, Rallidae and Sturdidae. Among the ND sero-positive families, 85.7 % (12/13) had ND antibody titre ≥7 log2. The species with ND antibodies were Coracias abyssinicus, Amaurornis flavirostra, Actophilornis africanus, Porphyrio alleni, Pychonotus barbatus, Francolinus bicalcaratus, Camaroptera brachyura, Numida meleagris, Streptopelia senegalensis, Anas platyrhynchos, Passer griseus, Ciconia ciconia, Torgos tracheliotus, Lamprotornis chloropterus, Buphagus africanus. Newcastle disease antibody prevalence was 14.6 % in free flying birds, 9.8 % in LPM and 27.8 % in LWBMs. Of the 300 birds tested for AI and ND antigen comprising 35 families and 62 species neither antigen was detected. This is the first report of AI antibody in Pychonotus barbatus, Ardea cinerea, Streptopelia senegalensis and Ciconia ciconia in Nigeria. The study concludes that wild birds in Kaduna State were exposed and responded to AI and ND antigens with Numida meleagris, Pychonotus barbatus and Streptopelia senegalensis likely to act as bridge species. Ciconia ciconia and Ardea cinerea are likely to play a role in the introduction of AI into Nigeria. Wild birds are likely to play a role in epidemiology of ND in Nigeria. Surveillance programs for monitoring and identification of AIV in wild birds in Nigeria should thus not focus solely on waterfowls, commercial farms and LPM but LWBMs and free flying birds should be included.
Key Words: Avian influenza, bridge species, Free flying wild birds, Gumboro disease, Live wild bird markets, Newcastle disease, Nigeria.