Incidence of Highly Pathogenic Avian Influenza H5N1 in Nigeria, 2005-2008

Abstract

Outbreaks of highly pathogenic avian influenza (HPAI) H5N1 occurred in Nigeria between December 2005 and July 2008. We describe temporal and spatial characteristics of these outbreaks at State and Local Government Area (LGA) levels. A total of 25 of 37 States (67.6%; Exact 95% CI: 50.2-82.0%) and 81 of 774 LGAs (10.5%; Exact 95% CI: 8.4-12.8%) were affected by HPAI outbreaks over the period from 2005 to 2008. The incidence risk of HPAI outbreak occurrence at the State level was 5.6% (0.7-18.7%) for 2005, 50.0% (30.7-69.4%) for 2006, 54.5% (29.9-80.3%) for 2007 and 0% for 2008. Only very few LGAs experienced HPAI outbreaks within the affected States. The incidence risk of HPAI outbreak occurrence on a LGA level was 0.3% (0.0-0.9%) for 2005, 6.6% (4.9-8.6%) for 2006, 4.2% (2.9-6.0%) for 2007 and 0% for 2008. The mean period between farmers noticing HPAI outbreaks and reporting them to veterinary authorities, and between reporting HPAI outbreaks and the depopulation of infected premises, was for both 4.5 days; both periods also had medians of 1 day. We have estimated the spatially smoothed incidence risk for the whole outbreak period and identified the existence of a large corridor in the western part of Nigeria and a smaller corridor in south-eastern part, where the risk of HPAI occurrence was lower than in the rest of the country. The effect of HPAI control policies on the outbreaks patterns are discussed, as well as possible reasons why HPAI did not become endemic in Nigeria.

Estimating the sensitivity of passive surveillance for HPAI H5N1 in Bayelsa state, Nigeria

“…Control measures included; active surveillance in farms and Live Bird Markets (LBM), restriction of bird movements throughout the country, enlightenment of poultry farmers on the significance of bio-security, thorough decontamination of infected premises and rapid stamping out of all laboratory confirmed cases (Ekong et al, 2012). Confirmation of a farm positive for HPAI H5N1 within a village led to all birds within that village being culled (Henning et al, 2012).…”

“…Control measures included; active surveillance in farms and Live Bird Markets (LBM), restriction of bird movements throughout the country, enlightenment of poultry farmers on the significance of bio-security, thorough decontamination of infected premises and rapid stamping out of all laboratory confirmed cases (Ekong et al, 2012). Confirmation of a farm positive for HPAI H5N1 within a village led to all birds within that village being culled (Henning et al, 2012).Passive surveillance or the reporting of suspected cases of AI to the veterinary authorities was set up in 2006 with the aim to optimize rapid detection of the disease. Early detection can elicit a rapid response by the Nigerian government and is critical if disease eradication must be achieved (Salman et al, 2003).…”

Serologic evidence of avian influenza virus infections among Nigerian agricultural workers

“…Home to more than 170 million people within 36 states [CIA, 2012], Nigeria is comprised of diverse groups/ethnicities with many different agricultural practices. Since highly pathogenic avian influenza (HPAI) H5N1 virus was first detected and confirmed in Africa in Kaduna State in February 2006 [Joannis et al, 2006], several other states in Nigeria have reported HPAI virus infections among millions of domestic and wild birds [Henning et al, 2012]. One human case and death due to infection with H5N1 virus occurred in February 2007.…”

Transmission Rate and Reproductive Number of the H5N1 Highly Pathogenic Avian Influenza Virus During the December 2005-July 2008 Epidemic in Nigeria

“…An outbreak of H5N1 highly pathogenic avian influenza (HPAI) occurred in Nigeria between December 2005 and July 2008. It affected a total of 25 states including the Federal Capital Territory (Henning et al., ). The disease mostly affected backyard commercial layer farms and a few free‐range poultry.…”