its overall distribution. The temperature is generally too hot for the larvae to develop on the surface of the sand and the deeper sand does not have enough oxygen. This preferred ecological niche offers a way to decrease transmission among humans by investing in concrete grounds as opposed to the sand that is usually used in shacks and some favelas. Indeed, Nany et al. (2007) report that "In shacks with concreted ground being cleaned every day with water, Tunga [penetrans] larvae were hardly found." In a longitudinal study conducted from March 2001 to January 2002, incidence of tungiasis was found to vary significantly with the local seasons of an endemic community in Brazil. In particular, the study found that "occurrence of tungiasis varies throughout the year and seems to follow local precipitation patterns. Maximum and minimum prevalence rates differed by more than a factor of three." The authors suggest that the correlation is due to the high humidity in the soil impairing larval development during the rainy season, as well as the more obvious reason that rain may simply wash away all stages of T. penetrans due its small size of 1mm. Acting as both biological vectors and definitive hosts, humans have spread Tunga penetrans from its isolated existence in the West Indies to all of Latin America and most of Africa via sea travel. Since the chigoe flea technically has no reservoir species and the female will cause tungiasis to any mammalian organism it can penetrate, this means the flea will have a relatively large number of hosts and victims. Epidemiologically, this is important as tungiasis often causes secondary infections. History Tungiasis had been endemic in pre-Columbian Andean society for centuries before discovery of T. penetrans as native to the West Indies. The first case of tungiasis was described in 1526 by Gonzalo Fernández de Oviedo y Valdés, where he discussed the skin infection and its symptoms on crew members from Columbus's Santa Maria after they were shipwrecked on Haiti. Through ship routes and further expeditions, the chigoe flea was spread to the rest of the world, particularly to the rest of Latin America and Africa. The spread to greater Africa occurred throughout the 17th and 19th centuries, specifically in 1872 when the infected crewmen of the ship Thomas Mitchell introduced it into Angola by illegal dumping of sand ballast, having sailed from Brazil. References External links Arthropod infestations