Incidence and distribution of foot-and-mouth disease in Asia, Africa and South America; Combining expert opinion, official disease information and livestock populations to assist risk assessment

Risk assessment procedures frequently require quantitative data on the prevalence of the disease in question. Although most countries are members of the World Organization for Animal Health (OIE), the importance attached to foot-and-mouth disease (FMD) reporting or surveillance for infection varies enormously between infected countries. There is a general consensus that FMD outbreaks in endemic countries are greatly under-reported, to a degree related either to the economic or the political development level of the country. This exploratory study was first undertaken by FAO, but thereafter extended and reviewed by the working group on FMD risk co-ordinated by the European Food Safety Authority (EFSA). The paper attempts to overcome the lack of reporting through using expert opinion to extrapolate incidence indices from countries considered to have 'representative' levels of FMD. These were combined with livestock density distributions to provide maps of prevalence indices, which were found to be highest in China (pigs), India (cattle), the Near East (small ruminants) and the Sahel (small ruminants and cattle). Similar patterns were found when weighted expert rankings of a range of additional ranked disease parameters were also produced, and then combined with susceptible animal densities to produce a weighted multi-species density. Results suggest that the methods can provide useful information at both national and sub-national resolution, even for countries for which quantitative FMD data is currently unavailable: two of the regions identified provide little or no data on a regular basis to the OIE and therefore may be overlooked if the level of officially reported FMD is only used. As the estimated prevalences are based on recent disease history and expert opinion, they are most likely to be inaccurate where FMD incursions are infrequent as a result of the preventive measures and geographical and trade isolation. This study, therefore, highlights the need for specific detailed country risk assessments where livestock trade is under consideration. Validating the approach including ground truthing, will require collaboration between a number of agencies and institutions, in critical countries, particularly those with high disease burdens that share borders or trade livestock with currently FMD-free nations.