Surveillance for Influenza Viruses in Poultry and Swine, West Africa, 2006–2008

Materials and Methods

Results

Discussion

Acknowledgments

References

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Table 1

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Suggested Citation

Emmanuel Couacy-Hymann, Viviane A. Kouakou, Gilbert L. Aplogan, Felix Awoume, Casimir K. Kouakou, Lamidi Kakpo, Bridgett R. Sharp, Laura McClenaghan, Pamela McKenzie, Robert G. Webster, Richard J. Webby, and Mariette F. Ducatez¹

Author affiliations: Central Laboratory for Animal Diseases, Bingerville, Côte d’Ivoire (E. Couacy-Hymann, V.A. Kouakou, C.K. Kouakou); Laboratoire de Diagnostic Vétérinaire et de Sérosurveillance, Parakou, Benin (G.L. Aplogan, L. Kakpo); Laboratoire Vétérinaire de Lomé, Lomé, Togo (F. Awoume); and St Jude Children’s Research Hospital, Memphis, Tennessee, USA (B.R. Sharp, L. McClenaghan, P. McKenzie, R.G. Webster, R.J. Webby, M.F. Ducatez)

Abstract

To determine the extent of animal influenza virus circulation in Côte d’Ivoire, Benin, and Togo, we initiated systematic year-round active influenza surveillance in backyard birds (predominantly chickens, guinea fowl, and ducks) and pigs. A total of 26,746 swab specimens were screened by using reverse transcription PCR. Animal influenza prevalence was estimated at 0 (95% CIs for each of the 2 study years 0–0.04% to 0–1.48% [birds] and 0–0.28% to 0–5% [pigs]). In addition, 2,276 serum samples from the same populations were negative for influenza-specific antibodies. These data indicate that the environments and host populations previously identified as harboring high levels of influenza virus in Southeast Asia do not do so in these 3 countries. The combination of climate and animal density factors might be responsible for what appears to be the absence of influenza virus in the backyard sector of the 3 countries.

Relatively little is known about the emergence, prevalence, and circulation of animal influenza viruses in Africa. There is no recent evidence of influenza infection in pigs in West Africa. In 2007, Gaidet et al. (1) found a 3.5% prevalence of avian influenza virus in wild birds in Africa; the highest prevalence in Mauritania and Senegal, and the most frequently infected species were Eurasian and African ducks. In addition, low-pathogenic avian influenza viruses of subtypes H1N8, H3N8, H4N2, H4N6, H4N8, H5N1, H5N2, H5N8, H6N2, H7N7, H9N1, and H11N9 have now been detected in wild birds in Nigeria, Egypt, Zambia, and South Africa (2–7).
Even less is known about avian influenza in domestic poultry in Africa. South Africa has had numerous outbreaks of many distinct influenza subtypes in chickens and ostriches, including H5N2, H5N3, H6N2, H9N2, H10N7, and H6N8 (3,8–11). Egypt is still facing recurrent highly pathogenic avian influenza (HPAI) (H5N1) outbreaks (12). In contrast, none of the other affected African countries have reported the pathogen since July 2008 (13).
We performed a systematic active surveillance study of animal influenza in Côte d’Ivoire, Benin, and Togo. These 3 West African countries reported cases of HPAI (H5N1) only in 2006, 2007, or 2008 (13,14). We aimed to confirm the current absence of HPAI (H5N1) from the region and determine whether any other influenza virus strains might circulate in domestic birds and pigs.