Abstract
The highly pathogenic avian influenza (H5N1 subtype) recurred in Nigeria after 9 months period of no reported case. A critical look at possible sources of the re-occurrence was desirable. The objective of this study was to determine whether avian influenza viruses were present at reasonably detectable levels (0.5%) in possible “bridge” species of wild and domestic birds. The study was conducted in 8 Nigerian states. A total of 403 birds from 40 species were sampled. Virus isolation was done in embryonated chicken eggs according to standard protocols. The test results were all negative for avian influenza viruses. The overall confidence interval (CI) calculated in R using the exact binomial confidence interval function was 0–0.007406. Tawny Eagle (Aquila rapax) was the lowest sampled 0.3% (1/403) and Red-billed Firefinch (Lagonosticta senegala) the highest 11.7% (47/403). The limitations of the sample size and possibly designing effects on the study, as to make concrete conclusions were acknowledged. Species of wild birds, so identified in the study could be useful in future surveys. Furthermore, multidisciplinary and community oriented approach, blending targeted and passive surveillances was suggested. This approach was envisaged to bring about wider coverage of “bridge” species and clearer insight of their possible roles in avian influenza re-occurrences and spread in Nigeria.
Highlights
Avian influenza (AI) is a highly contagious disease primarily of birds, and caused by influenza A viruses
A total of 403 birds made up of 40 species were sampled. 6 samples were positive for newcastle disease virus (NDV) but all tested samples were negative for avian influenza viruses
The study motivated by existing concerns on avian influenza has demonstrated surveillance for avian influenza viruses in wild and domestic birds’ species that might serve as “bridge” at the interfaces between migratory birds and domestic poultry
Summary
Avian influenza (AI) is a highly contagious disease primarily of birds, and caused by influenza A viruses. The exceptionally virulent viruses cause highly pathogenic avian influenza (HPAI), with mortality in affected flock as high as 100%. This group belongs to subtypes H5 and H7, but it is worth noting that not all H5 and H7 viruses’ infection lead to HPAI. All other subtypes cause a milder, primarily respiratory, disease, that is, low pathogenic avian influenza (LPAI) unless exacerbated by secondary infections [1]. Aquatic birds are the sources of avian influenza viruses [3, 4]. Geese, swans (Anseriformes), and gulls, terns (Charadriiforms) are thought to be natural reservoirs for avian influenza viruses and are capable of shading the viruses asymptomatically [5, 6]
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