Phylogenetic analysis of Newcastle disease viruses isolated from asymptomatic guinea fowls (Numida meleagris) and Muscovy ducks (Cariana moscata) in Nigeria.

Four Newcastle disease virus isolates were recovered from asymptomatic guinea fowl (Numida meleagris galeata) and Muscovy ducks (Cariana moscata). For the purpose of molecular identification and phylogeny, phylogenetic characterization was performed to identify the pathotypes. All four viruses had a cleavage motif (112)RRQKRF(117) which is characteristic of virulent strains. The isolates grouped with viruses previously reported as sub-lineage 5 g from chickens in Nigeria. This study report for the first time the identification of the virulent sub-lineage 5 g Newcastle disease virus from apparently healthy guinea fowl and domestic ducks in Nigeria, and since infections were sub-clinical, it suggest that these species could play a role in the spread and transmission of virulent Newcastle disease virus that can infect other poultry. The isolation and identification of virulent Newcastle disease virus in these unusual hosts and the high sequence similarity (99.3-100 %) between viruses in this study with strains reported for Niger and Cameroun gives insights into the ecology of virulent Newcastle disease viruses and suggests some cross-border movement and trade in live poultry.

Virulent Newcastle disease virus in Nigeria: identification of a new clade of sub-lineage 5f from livebird markets.

Newcastle disease (ND), caused by Avian Paramyxovirus Type 1, is a highly contagious and devastating viral disease of poultry of worldwide distribution with an enormous economic impact. Although ND is reported to be endemic in Nigeria, little information exists on the molecular epidemiology and the lineage distribution of the Newcastle disease viruses (NDVs) in the country, especially in the live bird markets (LBMs). Recent studies reported the identification of three unique sub-lineages. namely; 5f, 5g and 5h in West Africa, and sub-lineages 5f and 5g in particular in non-commercial farms in Nigeria. In this study, 33 NDV isolates, which included NDVs recovered from LBMs in Nigeria, during active surveillance from 2007 to 2008 and viruses recovered from outbreaks in backyard and commercial chicken farms within the same period were analysed. Based on determination of the F(0) cleavage site amino acid sequence and phylogenetic analysis, the isolates were classified as virulent; 16 strains were identified as sub-lineage 5g and 17 as sub-lineage 5f. Interestingly, 13 strains from the 5f group formed a distinct cluster that was not identified by other groups in similar studies. The close genetic similarities identified, provided evidence for the first time of the epidemiological link between the viruses circulating in the LBMs and those recovered from outbreaks in backyard and commercial chicken farms in Nigeria between 2007 and 2008. The emergence and identification of new sub-lineages provide an insight into the high rate of genetic drift occurring in NDV strains in Nigeria, and raises a lot of concerns about the efficacy of current ND control measures in the country.

Rapid antigen detection in the diagnosis of highly pathogenic avian influenza (H5N1) virus in Nigeria.

Highly pathogenic avian influenza (AI) is an infectious disease of agroeconomic and public health importance. The outbreak that occurred in Nigeria (2006-2008) was devastating to the poultry industry and raised public health concerns. In the course of its control, rapid laboratory confirmation of suspected cases in poultry was essential for prompt mobilization of control logistics for depopulation and decontamination of affected premises. Commercial rapid test kit was evaluated in the diagnosis of highly pathogenic AI (HPAI) as a preliminary to virus isolation. Between 2006 and 2007, 382 cases were tested out of which 149 were positive by rapid antigen detection. Virus isolation yielded 171 positive cases. The relative diagnostic sensitivity of Anigen Rapid AIV Ag test was 84.3% (95% confidence interval [CI], 78.1-88.9%), whereas the relative diagnostic specificity was 97.7% (95% CI, 94.2-99.1%). Rapid antigen detection is a useful technique for prompt diagnosis of HPAI for early detection and containment.

Field and laboratory findings of the first incursion of the Asian H5N1 highly pathogenic avian influenza virus in Africa.

In mid-January 2006 an outbreak of avian influenza in domestic birds was recorded in Kaduna State, Nigeria. The virus responsible for the outbreak was characterized as a highly pathogenic avian influenza H5N1 (A/chicken/Nigeria/641/06), belonging to the Qinghai lineage. The index case occurred on a farm containing mixed avian species including free-range birds. Clinical signs and mortality were observed in chickens, geese and ostriches. The present paper describes the clinical, pathological and virological findings of this outbreak.