The ecological basis of melioidosis

[Truncated] Melioidosis is a potentially fatal bacterial infection of populations in the tropical belt, particularly Southeast Asia and northern Australia. This infection is caused by Burkholderia pseudomallei, a facultative intracellular bacterial pathogen, and usually occurs after exposure to contaminated soil or water. Person-to-person spread of the disease is very uncommon. The principal determinants of infection up to the point of exposure are therefore likely to be environmental. After exposure, the known determinants of infection are mainly pre-existing disease co-morbidities such as diabetes mellitus and renal failure.This study was prompted by a small cluster of acute septicaemic melioidosis cases in northwestern Australia during the dry season. The unusual nature of this case-cluster led to the identification of a collection of environmental events whose collusion created the conditions necessary to sustain a short-lived focus of disease in the affected community. Subsequent field investigations led to the identification of a potential upstream amplifier of B. pseudomallei in an aerator used to treat the drinking water supply in the affected community. Field studies in locations where cases of melioidosis had occurred did not show B. pseudomallei to be widely dispersed, with the possible exception of recently cleared parts of the East Malaysian rainforest where B. pseudomallei was isolated from cultivated soils.