Emergence of plague in the Ikongo district of Madagascar, 1998. 2. Reservoir and fleas involved.

Our survey of mammals and fleas arose as a result of an outbreak of bubonic plague at an usually low altitude in the Ikongo district (Madagascar), whi le a previous study had found anti-F1 antibodies in an endemic hedgehog. An imals were sampled with live traps in two hamlets (Antanambao-Vohidrotra, 5 40 m alt. and Ambalagoavy 265 m alt.) and with pitfall traps in a neighbour ing forest (750 m alt.). Rat fleas were collected by brushing the fur and f ree-living fleas by use of light traps. The introduced shrew Suncus murinus was found only in the village of Ambalagoavy while the black rat (Rattus r attus) was found in all three sites and the only seropositive rat was caugh t at Antanambao-Vohidrotra. In contrast, among the Tenrecidae (endemic shre ws and hedgehogs) found in the forest near the first village, four animals were found seropositive for anti-F1 antibodies. One of them was carrying th e endemic flea Paractenopsyllus pauliani, not yet reported as a vector of p lague, The endemic vector of plague, Synopsyllus fonquerniei, was found onl y in the first village of Antanambao-Vohidrotra, and the cosmopolite flea X enopsylla cheopis only in Ambalagoavy Although no Yersinia pestis could be isolated and no F1-antigen could be detected in these animals we found evid ence of, the recent transmission of plague in Antanambao-Vohidrotra and the nearby forest but not in Ambalagoavy. These data corroborate with the sylv atic plague cycle hypothesis in Madagascar and its involvement in the outco me of the bubonic plague outbreak in this district.