Avian Influenza Viruses Detected in Birds in Sub-Saharan Africa: A Systematic Review

Abstract

In the recent past, sub-Saharan Africa has not escaped the devastating effects of avian influenza virus (AIV) in poultry and wild birds. This systematic review describes the prevalence, spatiotemporal distribution, and virus subtypes detected in domestic and wild birds for the past two decades (2000-2019). We collected data from three electronic databases, PubMed, SpringerLink electronic journals and African Journals Online, using the Preferred Reporting Items for Systematic reviews and Meta-Analyses protocol. A total of 1656 articles were reviewed, from which 68 were selected. An overall prevalence of 3.0% AIV in birds was observed. The prevalence varied between regions and ranged from 1.1% to 7.1%. The Kruskal-Wallis and Wilcoxon signed-rank sum test showed no significant difference in the prevalence of AIV across regions, χ²(3) = 5.237, p = 0.1553 and seasons, T = 820, z = -1.244, p = 0.2136. Nineteen hemagglutinin/neuraminidase subtype combinations were detected during the reviewed period, with southern Africa recording more diverse AIV subtypes than other regions. The most detected subtype was H5N1, followed by H9N2, H5N2, H5N8 and H6N2. Whilst these predominant subtypes were mostly detected in domestic poultry, H1N6, H3N6, H4N6, H4N8, H9N1 and H11N9 were exclusively detected in wild birds. Meanwhile, H5N1, H5N2 and H5N8 were detected in both wild and domestic birds suggesting circulation of these subtypes among wild and domestic birds. Our findings provide critical information on the eco-epidemiology of AIVs that can be used to improve surveillance strategies for the prevention and control of avian influenza in sub-Saharan Africa.

Keywords: Orthomyxoviridae; avian influenza; avian influenza virus; ecology; epidemiology; poultry; sub-Saharan Africa; subtype; wild waterfowl.

Figure 1

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow chart of the literature search, screening, assessing eligibility and article selection.

Figure 2

Number of selected articles per quarter from 2000 to 2019.

Figure 3

Scatter plot showing the correlation between years and number of publications.

Figure 4

Reviewed articles according to countries.

Figure 5

Geographical distribution of highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI) subtypes in sub-Saharan Africa. Color codes: red denotes countries reporting either HPAI only or both HPAI and LPAI; orange denotes countries reporting H5 or H7, but whose pathogenicity was not determined; yellow denotes countries reporting LPAI; green denotes countries reporting AIV whose subtypes and pathogenicity were not determined; black denotes countries in sub-Saharan Africa with no reports of AIV in birds in the study period; gray denotes North African countries not included in the study; blue denotes major water bodies.