Plague risk in vulnerable community: assessment of Xenopsylla cheopis susceptibility to insecticides in Malagasy prisons

BACKGROUND Prisons in Madagascar are at high risk of plague outbreak. Occurrence of plague epidemic in prisons can cause significant episode of urban plague through the movement of potentially infected humans, rodents and fleas. Rodent and flea controls are essential in plague prevention, by reducing human contact with plague reservoirs and vectors. Insecticide treatment is the key step available for the control of rat fleas which transmit the disease from infected rodents to human. The implementation of an adapted flea control strategy should rely on the insecticide susceptibility status of the targeted population. For the purpose of plague prevention campaign in prisons, we conducted insecticide resistance survey on Xenopsylla cheopis, the rat flea. METHODS Fleas were collected on rats caught in six prisons of Madagascar. They were exposed to insecticide treated filter papers and mortality was recorded following World Health Organization protocol. RESULTS The fleas collected in the prisons had different resistance patterns, while a high level of resistance to insecticides tested was described in the Antanimora prison, located in the heart of Antananarivo, the capital of Madagascar. CONCLUSIONS This finding is alarming in the context of public health, knowing that the effectiveness of flea control could be jeopardized by insecticide resistance. In order to establish more accurate rat fleas control in prisons, the main recommendations are based on continuous monitoring insecticide susceptibility of flea, insecticide rotation, and the development of a new method for flea control.