Anthropogenic factors and the risk of highly pathogenic avian influenza H5N1: prospects from a spatial-based model

Paul, Mathilde; Tavornpanich, Saraya; Abrial, David; Gasqui, Patrick; Charras-Garrido, Myriam; Thanapongtharm, Weerapong; Xiao, Xiangming; Gilbert, Marius; Roger, Francois; Ducrot, Christian

To tackle the outbreaks, Thai authorities implemented different control measures which evolved over time, but the initial plan aimed to control poultry product movement countrywide. Beginning in July 2004, in addition to pre-emptive culling, the movement of poultry and avian products was restricted within a 5-km radius of an infected flock; these restrictions were extended during the second wave. The whole country was also zoned into 5 areas, and poultry movements were strictly controlled through 32 check points between zones [4] . This helped to contain the disease from spreading countrywide. In addition to this set of control measures, and because free-grazing ducks were suspected of being H5N1 HPAI reservoirs, the Thai Government encouraged duck producers to change their practices from a free-grazing to a housed system. However, farmers were not able to change their practices in a short period of time [23] . In 2005, ducks were still allowed to graze in paddy fields, but the DLD prohibited long-distance movements.The free-ranging practice became illegal in March 2006, obliging farmers to house every duck flock [23] . However, by this time the epidemic was already under control: the number of outbreaks had dropped from 1 717 during the second wave to 75 during the third wave (1 July 2005 to 9 November 2005). Thus, while the housing of all free-grazing ducks took time to achieve, restrictions on the long-distance movements of free-grazing ducks had already contributed largely to limiting HPAI spread in Thailand.