the infection that remain. there are only lingering symptoms at this time, described in the next section. morphology in a study of 1000 freshly ejected t. penetrans eggs, it was found that females are generally smaller than males for all criteria. in some cases, though, females had a bigger epipharynx and maxillar palpus. due to its burrowing activity, the chigoe flea has developed a well-developed lacinia and epipharynx that is used to penetrate the skin. overall, the fleas’ head is relatively flattened, which again aids in burrowing through the epidermal and dermal layers. investigators have also found that adult t. penetrans have different morphologies with respect to the shape of their head. some have a rounded head, others have head shapes that resemble ski ramps more than anything else; still, others demonstrate head shapes that are very linear with a slight bulge at the nose. these morphologies were seen to be host-specific, as only fleas of some head-types were found in specific hosts. this, along with genetic differences among the t. penetrans fleas that infect different host animals, may suggest that there are several species of closely related species have been grouped taxonomically under one binomial nomenclature. though the chigoe flea resembles most others in morphology, the flea has a hypertrophic region between tergites 2 and 3. as stated in eisele et al. (2003), tergites 2 and 3, as well as the abdominal sternites, stretch considerably and are bent apart. chitinous clasps that are built for the abdominal enlargement surround these regions and hold onto the hypertrophic zone, giving them the appearance of a three-leafed clover. (see image 7 of the life cycle diagram.) surprisingly, the rest of the flea, including the head and the thorax, do not change in shape., with the rapid expansion of the flea, the morphology of the flea is now vastly different. it has gone from the smallest flea in the world to a bulging mass that measures 5–10mm in diameter. this results in a volume that is 2000 to 3000 times what it used to be. reproduction females have a depression or groove at their abdominal end whereas the males have their protrusive copulatory organs in that same region. these morphological differences reflect the way the male and female copulate. in the first step toward copulation, the female penetrates an organism in an ungravid state. it is only there that the male will find her and copulate. copulation of adults has not been observed in the wild. with the female reproductive organs pointing outward, the male will place his reproductive organs "in direction to the upright abdominal end of the female" to copulate. having copulated for only a few seconds to 2 minutes, the male will then begin to search for another female. after copulation is complete, the male will die, although sometimes he will take a blood meal before doing so. eggs will be expelled whether or not they have been fertilized. the chigoe flea eggs’ average length is 604 μm and the just hatched larvae, in their first instar, have an average length of 1,500 μm. at the second and last instar (t. penetrans is unique among the fleas in that it only has two, instead of three, instars.) the larvae decrease in size to 1,150 μm after growing to at least 2,900 μm. the development from instar 1 to instar 2 lasts less than one day. on the whole, tunga penetrans does not do very well in terms of its darwinian fitness. in a laboratory setting in which different mediums were provided for larval growth, the rate of survival from egg to adult in the best medium was 1.05%. only 15% of the eggs were found to develop into larvae, and of those, only 14% formed a cocoon. moreover, only half of the pupae reached the adult phase, resulting in gender disequilibrium. although these results reflect a laboratory setting, the general lack of success for t. penetrans’s reproductive (opportunistic) r-strategy is surprising given the number of fleas that a single person can attract. the low survival rate suggests that a concentrated public health effort directed at any point in the flea’s life cycle is likely to deal a crippling blow to the overall population of the flea in the area. diagnosis there are no diagnostic tests for tungiasis. this is most likely because the parasite is ectoparasitic with visible symptoms. identification of the parasite through removal, and a patient’s traveling history, should suffice for diagnosis, though the latter is clearly more useful than the former. localization of the lesion may be a useful diagnostic method for the clinician. a biopsy may be done, though again, it is not required for diagnosis. prevention due to the high number of hosts, eradication of tungiasis is not feasible, at least not easily so. public health and prevention strategies should then be done with elimination as the target. better household hygiene, including having a cemented rather than a sand floor, and washing it often, would lower the rates of tungiasis significantly. though vaccines would be useful, due to the ectoparasitic nature of chigoe flea, they are neither a feasible nor an effective tool against tungiasis. nevertheless, due to the high incidence of secondary infection, those at risk of tungiasis should get vaccinated against tetanus. a better approach is to use repellents that specifically target the chigoe flea. one very successful repellent is called zanzarin, a derivative of coconut oil, jojoba oil, and aloe vera. in a recent study involving two cohorts, the infestation rates dropped 92% on average for the first one and 90% for the other. likewise, the intensity of the cohorts dropped by 86% and 87% respectively. the non-toxic nature of zanzarin, combined with its "remarkable regression of the clinical pathology" make this a tenable public health tool against tungiasis. the use of pesticide, like ddt, has also led to elimination of the tunga penetrans, but this control/prevention strategy should be utilized very carefully, if at all, because of the possible side effects such pesticides can have on the greater biosphere. in the 1950s, there was a worldwide effort to eradicate malaria. as part of that effort, mexico launched the campaña nacional para la erradicación de paludismo, or the national campaign for the eradication of malaria. by spraying ddt in homes, the anopheles a genus of mosquitoes known to carry the deadly plasmodium falciparum was mostly eliminated. as a consequence of this national campaign, other arthropods were either eliminated or significantly reduced in number, including the reduviid bug responsible for chagas disease (american trypanosomiasis) and t. penetrans. controlled, in-home spraying of ddt is effective as it gives the home immunity against arthropods while not contaminating the local water supplies and doing as much ecological damage as was once the case when ddt was first introduced. while other species gradually gained resistance to ddt and other insecticides that were used, t. penetrans did not; as a result, the incidence of tungiasis in mexico is very low when compared to the rest of latin america, especially brazil, where rates in poor areas have been known to be as high or higher than 50%. there was a 40-year period with no tungiasis cases in mexico. it was not until august 1989 that three mexican patients presented with the disease. though there were other cases of tungiasis reported thereafter, all were acquired in africa. treatment removed parasite as the disease is self-limiting, at least when exposure to the parasite is limited, management is mostly confined to treatment. due to the secondary infection that can cause serious medical issues, the recommended course of action upon diagnosis is a surgical extraction of the fleas followed by the application of a topical antibiotic. care should be taken to avoid tearing the flea during the extraction procedures as severe inflammation will result. the same will occur if part of the flea is left behind. sterile equipment should always be used, as contaminated instruments could act as mechanical vectors for pathogens to enter the body. there is no drug that has proven to be effective against embedded fleas. oral niridazole was once considered a therapeutic drug, but well-designed studies are lacking and, given the severe adverse effects, this is one drug that is likely to cause more harm than good. however, it has some anecdotal evidence of lysing the fleas altogether. oral ivermectin is considered by some in endemic areas to be a panacea against the fleas but studies using high doses have failed to validate this hypothesis. other drugs such as topical ivermectin and metrifonate have been somewhat successful, but not enough to be significant. for superinfections, trimethoprim, sulfamethoxazole, metronidazole, amoxicillin, (with/without clavulanate) have been used successfully, though these treat only secondary infections. successful topical treatments also include cryotherapy and electrodesiccation of the lesion. if formaldehyde, chloroform, or ddt are used topically, care should be taken when dealing with the resulting morbidity. the t. penetrans flea can also be suffocated using occlusive petrolatum, while vaseline will kill the organism as well, most likely due to suffocation as the stigmata would be covered. the gum of the mammee apple (mammea americana), a fruit that also goes by the name saint domingo apricot, has also been used to kill the chigoe flea, though this has not been reported in the main t. penetrans literature. even without treatment, the burrowed fleas will die within five weeks and are naturally sloughed off as the skin sheds. epidemiology for the most part, the chigoe flea lives 2–5 cm below the sand, an observation which helps explains 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 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.