| Summary: | 2012 Summer. Includes bibliographical references. A zoonotic disease that has killed millions over the course of at least three pandemics, plague remains a threat in regions where the etiologic agent, Yersinia pestis, persists in natural cycles involving small mammals and their fleas. Numerous flea species have been implicated as Y. pestis vectors, and some provide a "bridge" from zoonotic hosts to humans, particularly during the epizootics that decimate susceptible small mammal populations. In order to serve as a bridging vector, a flea species must be able to transmit Y. pestis, it must feed on infectious zoonotic hosts, and it must feed on humans. Identifying bridging vector species in plague-endemic regions can aid in the development of vector-control activities aimed at reducing the incidence of human plague. The West Nile region is an established plague focus in northwest Uganda. Since 1999, more than 2400 suspect human plague cases have been reported from Vurra and Okoro counties. The most likely source of infection for humans in this region is the black rat, Rattus rattus, which commonly infests human habitations and is highly susceptible to Y. pestis infection. Other potential zoonotic hosts include other rodent and shrew species that predominate in the peridomestic environment and occasionally enter huts. Two rat flea species, Xenopsylla cheopis and X. brasiliensis, both among the most efficient flea vectors of Y. pestis, are very likely to serve as bridging vectors to humans in Vurra and Okoro counties. Recent investigations, however, have found that the cat flea, Ctenocephalides felis, comprises more than 88% of host-seeking (off-host) fleas captured in huts in this region. Though an inefficient vector, this species is capable of transmitting Y. pestis. Given its dominance in human habitations and its catholic feeding habits in other regions, we hypothesized that C. felis might serve as a secondary bridging vector in Vurra and Okoro counties. In order to address this hypothesis, we sought to ...
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