Qualitative release and exposure assessment on the risk of HPAI transmission between sector 4 farms and between sector 3 and sector 4 farms in Kenya

This study assessed the risk of transmission of highly pathogenic avian influenza (HPAI) between backyard poultry (S4) farms and between S4 and semi-commercial (S3) farms in Kenya. It was designed to complement findings of a study that had been conducted in 2007 by the DVS and FAO to evaluate the risk of introduction of the disease into the country. It followed the OIE risk analysis framework where release, exposure and consequence assessments are done successively and their risk parameter estimates combined to obtain an overall risk estimate for a given pathway. Risk questions were formulated in a stakeholder workshop that was convened at ILRI in Nairobi on 2-3 October 2008.

A total of nine risk pathways were formulated (4 for the first question, 3 for the second and 2 for the third as indicated by the roman numerals above). Risk parameters were estimated using qualitative methods because data needed for quantitative analyses were not available. Data and information used in the analysis were obtained from an expert elicitation survey, project reports or published literature. The expert elicitation survey used structured questionnaires. For each question raised, respondents were expected to give the most likely answer, its minimum and maximum value, the level of confidence on the answer given (in a scale of 1 to 5 with 1= not confident, 5= very confident) and the source of the information used for reference. Risk estimates were determined as very high, high, medium, low, very low or negligible. Overall risk estimates for each pathway were obtained by combining estimates for each step of the pathway using a combination matrix described by Zepeda (1998). The level of uncertainty for each risk parameter estimate was described as low, medium or high.