Risk factors of highly pathogenic avian influenza outbreaks in domestic poultry
05 august 2010 - Since late 2003, 62 countries around the world have reported cases of highly pathogenic avian influenza virus A subtype H5N1 (H5N1 HPAI) in poultry and wild birds. Up to July 2010, the cumulative number of confirmed human cases of H5N1 HPAI reported to the World Health Organization is 502, of which 298 have resulted in death.
The H5N1 HPAI global disease situation is now relatively stable, but still alarming in some countries where the disease is considered entrenched. In these locations, pockets of infections are closely associated to well-known risk factors, such as high human and chicken densities, large free-grazing duck populations, poor biosecurity in smallholder units and culturally-determined food market habits linked to poor poultry hygiene.
In 2007, the use of spatial cluster analysis revealed the presence of more specific risk factors supporting the spread of infections in selected geographical clusters, such as the higher percentage of surface water which would support higher densities of domestic and wild water birds compared with other adjacent regions.
For instance, in Southeast Asia the presence of agro-livestock farming systems involving the combination of paddy rice production, domestic water birds and poultry in the river deltas is ubiquitous. These specific mixtures of factors are likely to be important for maintenance of infection given that H5N1 HPAI thrives in the presence of water, bird faeces, ducks and chickens.
More recently, a study published in the International Journal of Infectious Diseases found that two risk factors - poultry density and road density - had a statistically significant correlation with the number of H5N1 HPAI outbreaks in poultry at district levels in West Java Province, Indonesia.
Both the medical and veterinary professions recognize the vital roles played by identifying and understanding disease risk determinants. Such knowledge underpins a multilayered approach to proactive disease risk management; one that combines the interlocking elements of foresight, prevention, impact mitigation, early detection, and swift and effective reaction.
To accomplish its mandate of achieving food security for all, the Food and Agriculture Organization of the United Nations (FAO) is undertaking various studies to better understand the root causes that underpin pathogen evolution, establishment and persistence. These studies could potentially reveal viable options to address high-impact transboundary diseases that are emerging and re-emerging globally, thereby affecting animal and human health.