the floor. Rate of incidence therefore is greatly increased in poor communities and populations because of the lack of adequate housing. This occurs in significantly higher proportions during the peak of the dry season in local communities. Reservoirs and transmission T. penetrans has been documented to use various warm-blooded animals as reservoir hosts, including humans, pigs, dogs, cats, rats, sheep, cattle, donkeys, monkeys, birds, and elephants. These hosts directly propagate the disease by being the origin of the next generation of fleas. Once the female flea expels 100–200 eggs, the cycle of transmission begins again. Lifecycle T. penetrans eggs, on average, are 604 μm long, The larva will hatch from the egg within one to six days, assuming the environmental conditions (e.g., moisture, humidity, etc.) are favorable. After hatching, the flea will progress through two instar phases. This is unique in that most fleas go through three, instead. Over the course of that development, the flea will first decrease in size from its just-hatched size of 1,500 μm to 1,150 μm (first instar) before growing to 2,900 μm (second instar). About 6 to 8 days after hatching, the larva pupates and builds a cocoon around itself. Because it lives mostly on and below the surface of the sand, sand is used to stabilize the cocoon and help to promote its development. An environmental disturbance such as rain or a lack of sand have been shown to decrease incidence, most likely due to decreasing the environmental factors (i.e., sand) on which the flea depends for overall growth. Barring any disturbances to the cocoon, an adult flea will emerge from the puparium after 9–15 days. In the adult phase, the flea will occasionally feed on unsuspecting animals. Only once the female burrows into the skin can reproduction occur, as the male and female show no interest in each other in the wild. The male flea dies after copulation. The female flea continues in vivo ectodevelopment, described in stages by the Fortaleza classification of tungiasis. Fortaleza classification In a seminal paper on the biology and pathology of Tunga penetrans, Eisele et al. (2003) provided and detailed the five stages of tungiasis, thereby detailing the in vivo development of the female chigoe flea for the first time. In dividing the natural history of the disease, the Fortaleza Classification formally describes the last part of the female flea's life cycle where it burrows into its