Surveillance for Avian Influenza H5 Antibodies and Viruses in Commercial Chicken Farms in Kano State, Nigeria

摘要

Outbreaks of highly pathogenic Avian Influenza occurred previously for 3 consecutive years, 2006, 2007 and 2008, in Kano State, Nigeria, causing heavy economic losses to farmers and the government. It was against this background that Avian Influenza (AI) surveillance study in commercial poultry farms in the State was conducted. Haemagglutination Inhibition (HI) test was conducted to determine the presence of AI H₅ antibodies in 1,160 sera obtained from flocks in 33 Avian influenza affected (AF) and 25 Non Avian influenza-affected (NAF) farms. To complement the study, 320 cloacal swabs obtained from flocks in farms that were serologically positive for AI H₅antibodies, were further subjected to Reverse Transcription-Polymerase Chain Reaction (RT-PCR), to determine if the chickens were shedding AI viruses. Of the 1,160 sera tested, 150 (12.9%) were positive for AI H5 antibodies, with flocks in 16 (27.6%) of the farms being positive. Prevalence rates of 14.1 and 11.4% and mean antibody titres of 5.4±0.2 and 4.6±0.1 log2 for AI H₅ antibodies were obtained for AF and NAF farms, respectively. The RT-PCR results showed that all the 320 cloacal swabs tested were negative for AI H₅ viruses. The antibodies detected between flocks in the AF and NAF farms might be attributed to vaccination and the titres determined were above the minimum protection level recommended by the OIE. It was recommended that vaccination of chickens against AI should be discouraged because it may interfere with the stamping out policy adopted by Nigeria in the control and eradication of the disease.