Occurrence of the off-host life stages of Tunga penetrans (Siphonaptera) in various environments in Brazil

To explore the local transmission dynamics of Tunga penetrans in Brazil, 134 soil samples from various environments were collected in three different endemic regions of the country and checked for the presence of the flea's larvae, pupae and adults. The samples, which came from an urban slum in the north-east, a village of Xavante Indians in the central-west and a community of Yanomami Indians living in traditional longhouses (malocas) in the north, were categorized as indoor, outdoor or indoor-outdoor (the latter representing samples collected in the malocas). The proportion of samples found positive for T. penetrans was lowest in the slum (9.3%) and highest in the Yanomami village (32.0%; P=0.01). Soil samples collected below bedsteads or hammocks or from the indoor resting places of dogs were significantly more likely to be positive than the indoor samples collected at other sites (65.0% v. 35.0%; P=0.02). There was no evidence indicating that the presence of T. penetrans in a soil sample was markedly affected by soil temperature, air temperature or air humidity. As no life stages of T. penetrans were found in any outdoor sample, it seems likely that, in resource-poor settings in Brazil, most transmission of T. penetrans occurs indoors. Control measures against the off-host life stages of T. penetrans should therefore be targeted at particular indoor micro-environments.