neglected tropical diseases neglected tropical diseases neglected tropical diseases (ntds) are a diverse group of tropical infections that are common in low-income populations in developing regions of africa, asia, and the americas. they are caused by a variety of pathogens, such as viruses, bacteria, protozoa, and parasitic worms (helminths). these diseases are contrasted with the "big three" infectious diseases (hiv/aids, tuberculosis, and malaria), which generally receive greater treatment and research funding. in sub-saharan africa, the effect of neglected tropical diseases as a group is comparable to that of malaria and tuberculosis. ntd co-infection can also make hiv/aids and tuberculosis more deadly. neglected tropical diseasesnumber of people requiring interventions against neglected tropical diseases in 2015specialtyinfectious disease some treatments for ntds are relatively inexpensive. for example, the treatment for schistosomiasis is us$0.20 per child per year. nevertheless, in 2010 it was estimated that control of neglected diseases would require funding of between us$2 billion and $3 billion over the subsequent five to seven years. some pharmaceutical companies have committed to donating all the drug therapies required, and mass drug administration efforts (for example, mass deworming) have been successful in several countries. while preventive measures are often more accessible in the developed world, they are not universally available in poorer areas. within developed countries, neglected tropical diseases affect the very poorest in society. in the united states, there are up to 1.46 million families, including 2.8 million children, living on less than two dollars a day. in developed countries, the burdens of neglected tropical diseases are often overshadowed by other public health issues. however, many of the same issues put populations at risk in developed as well as developing nations. for example, other problems stemming from poverty, such as lack of adequate housing, can expose individuals to the vectors of these diseases. twenty neglected tropical diseases are prioritized by the world health organization (who), though other organizations define ntds differently. chromoblastomycosis and other deep mycoses, scabies and other ectoparasites, and snakebite envenomation were added to the list in 2017. these diseases are common in 149 countries, affecting more than 1.4 billion people (including more than 500 million children) and costing developing economies billions of dollars every year. they resulted in 142,000 deaths in 2013—down from 204,000 deaths in 1990. reasons for neglect the importance of neglected tropical diseases has been underestimated since many are asymptomatic and have long incubation periods. the connection between death and a neglected tropical disease that has been latent for a long period is not often realized. areas of high endemicity are often geographically isolated, making treatment and prevention much more difficult. these diseases have been overlooked because they mainly affect the poorest countries of the developing world and because of the recent emphasis on decreasing the prevalence of hiv/aids, tuberculosis, and malaria. far more resources are given to those three diseases because of their higher mortality and public awareness rates. neglected tropical diseases do not have a prominent cultural figure to champion the cause. stigma neglected tropical diseases are often associated with social stigma, making their treatment more complex. public health research has only recently begun to focus on stigma as a component of the issue. from the 1960s onward, approximately one citation a year related to social stigma. in 2006, there were 458. stigma greatly affects disease control by decreasing help-seeking and treatment adherence. disease control programs, starting as early as the 1980s, have begun to integrate stigma mitigation into their offerings. in india, a leprosy program prioritized the message that "leprosy is curable, not hereditary" in order to inspire optimism in highly affected communities. the goal was to make leprosy a disease "like any other", so as to reduce stigma. at the same time, medical resources were optimized to fulfill the promise that the disease could be cured. economic incentives neglected tropical diseases are not commercial, and consequently, patents and profit play no role in stimulating innovation. like all non-commercial areas, these diseases are the responsibility of governments and philanthropy (including industry philanthropy). currently, the pharmaceutical industry views research and development as highly risky. for this reason, resources are not often put into the field of ntds, and new chemical products are often expensive. a review of public and private initiatives found that of the 1,393 new chemical products that were marketed between 1975 and 1999, only 16 were related to tropical diseases and tuberculosis. the same review found that there was a 13-fold greater chance of a newly marketed drug being for central nervous system disorders or cancer than for an ntd. because of a lack of economic incentives for the pharmaceutical industry, successful ntd treatment programs have often relied on donations. the mectizan donation program has donated over 1.8 billion tablets of ivermectin. while developed countries often rely on government-run and private partnerships to fund such projects, developing nations frequently have significantly lower per-person spending on these diseases. a 2006 report found that the gates foundation funded most extra activities to counter these diseases. developed nations since 2008, the concept of "neglected diseases of poverty" has been developed and explored. this group of diseases overlaps with neglected tropical diseases, which also pose a threat to human health in developed nations. in the united states alone, there are at least 12 million people with neglected parasitic infections. they make up a hidden disease burden among the poorest people in wealthy societies. in developed nations, lack of knowledge in the healthcare industry and lack of conclusive diagnostic tests perpetuate the neglect of this group of diseases. in the united states, high rates of parasitic infection can be distributed along geographic, racial, and socio-economic lines. among african-americans, there may be up to 2.8 million cases of toxocariasis. toxocariasis, trichomoniasis, and other neglected infections occur in the united states at the same rate as in nigeria. within the hispanic community, neglected infections are concentrated near the us–mexico border. vector-borne illnesses are especially high, with some rates approaching those of latin america. chagas disease was found in the us as early as the 1970s. however, in the developed world, diseases that are associated with poverty are often not addressed comprehensively. this may be due to a lack of economic incentives and public policy failings. a lack of awareness prevents effective policy generation and leaves healthcare services unequipped to address the issue. additionally, little effort is put into creating and maintaining large data sets on neglected diseases in the united states and other developed nations. the first summit on the issue was held by the adler institute on social exclusion in the united states in 2009. in europe, a similar trend is seen. neglected tropical diseases are concentrated in eastern and southern europe, where poverty levels are highest. the most prevalent diseases in this region are ascariasis, trichuriasis, zoonotic helminth infections, and visceral leishmaniasis. migration paths to europe, most notably to spain, have brought diseases to europe as well. as many as 6,000 cases of chagas disease have been introduced in this way. in response to a growing awareness of the burden on these populations, the european centre for disease prevention and control has laid out ten public health guidelines. they cover a variety of topics, from health education and promotion to community partnerships and the development of a minority healthcare workforce. list of diseases there is some debate among the who, cdc, and infectious disease experts over which diseases are classified as neglected tropical diseases. feasey, a researcher in neglected tropical diseases, notes 13 neglected tropical diseases: ascariasis, buruli ulcer, chagas disease, dracunculiasis, hookworm infection, human african trypanosomiasis, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis, trachoma, and trichuriasis. fenwick recognizes 12 "core" neglected tropical diseases: the same as above, excluding hookworm. these diseases result from four classes of causative pathogens: (i) protozoa (for chagas disease, human african trypanosomiasis, and leishmaniasis); (ii) bacteria (for buruli ulcer, leprosy, trachoma, and yaws), (iii) helminths or metazoan worms (for cysticercosis/taeniasis, dracunculiasis, echinococcosis, foodborne trematodiases, lymphatic filariasis, onchocerciasis, schistosomiasis, and soil-transmitted helminthiasis); and (iv) viruses (for dengue, chikungunya, and rabies). the world health organization recognizes the twenty diseases below as neglected tropical diseases. who/cdc plosmajor ntds buruli ulcerchagas diseasedengue & chikungunya*dracunculiasisechinococcosisyawsfascioliasisafrican trypanosomiasisleishmaniasisleprosylymphatic filariasisonchocerciasisrabiesschistosomiasissoil-transmitted helminthiasiscysticercosistrachomascabies and other ectoparasitessnakebite envenomingmycetoma and deep mycoses protozoan infections: entamoeba histolytica and naegleria fowleri (both pathogenic amoeba)babesiosisbalantidiasischagas diseasegiardiasishuman african trypanosomiasisleishmaniasisplasmodium vivax and other non-p. falciparum malarias helminth infections: dracunculiasisechinococcosisfood-borne trematodiasesloiasislymphatic filariasisonchocerciasisother food-borne helminthiases (trichinosis, anisakiasis, gnathostomiasis)schistosomiasissoil-transmitted helminthiases (ascariasis, hookworm diseases, trichuriasis, strongyloidiasis)taeniasis-cysticercosistoxocara and baylisascaris (visceral larva migrans) viral infections: arboviral infections (dengue, chikungunya, zika, japanese encephalitis, jungle yellow fever and others)enterovirus 71 and related viruseshtlv-1, htlv-2 and other non-hiv retrovirus infectionsrabiesrift valley feverviral hemorrhagic fevers bacterial infections: bartonella spp.atypical mycobacteria (including mycobacterium bovis and buruli ulcer)cholera and other enteric bacteria (shigella, salmonella, e. coli)leprosyleptospirosismelioidosisnomarelapsing fevertrachomayaws and other nonvenereal treponematoses (bejel and pinta)q fever fungal infections: mycetoma, chromoblastomycosis, and other deep tissue mycosesparacoccidioidomycosis ectoparasites: scabiesmyiasis non-infectious diseases caused by toxin exposure: podoconiosissnakebite envenoming * only who the world health organization's 2010 report on neglected tropical diseases offers an expanded list including dengue, rabies, yaws, cysticercosis, echinococcosis, and foodborne trematode infections. neglected tropical diseases worldwide burden diseasedalys (million)deaths/yrglobal prevalence (million)population at risk (million) schistosomiasis4.5280,000207780 hookworm22.165,0005763200 ascariasis10.560,0008074200 leishmaniasis2.151,00012350 trypanosomiasis1.548,0000.360 chagas disease0.714,000825 trichuriasis6.410,0006043200 leprosy0.26,0000.4not determined lymphatic filariasis5.801201300 trachoma2.3084590 onchocerciasis0.503790 cryptococcosis12400,00018 buruli ulcer main article: buruli ulcer buruli ulcer is caused by the bacterium mycobacterium ulcerans. it is related to the family of organisms that cause tuberculosis and leprosy, but mycobacterium ulcerans produces a toxin, mycolactone, that destroys tissue. the prevalence of buruli ulcer is unknown. the risk of mortality is low, although secondary infections can be lethal. morbidity takes the form of deformity, disability, and skin lesions, which can be prevented through early treatment with antibiotics and surgery. it is found in africa, asia, and latin america. chagas disease main article: chagas disease a young boy from panama with chagas disease. it has manifested as an acute infection with swelling of one eye (chagoma). chagas disease is also known as american trypanosomiasis. there are approximately 15 million people infected with chagas disease. morbidity rates are higher for immunocompromised individuals, children, and the elderly, but can be very low if the disease is treated early. chagas disease does not kill victims rapidly, instead causing years of debilitating chronic symptoms. it is caused by a vector-borne protozoa and spread by contact with trypanosoma cruzi-infected feces of the triatomine (assassin bug). the protozoan can enter the body via the bug's bite, skin breaks, or mucous membranes. infection can result from eating infected food or coming into contact with contaminated bodily fluids. there are two phases of chagas disease. the acute phase is usually asymptomatic. the first symptoms are usually skin chancres, unilateral purplish orbital oedema, local lymphadenopathies, and fever accompanied by a variety of other symptoms depending on the infection site. the chronic phase occurs in 30 percent of total infections and can take three forms: asymptomatic (most prevalent), cardiac, and digestive lesions. chagas disease can be prevented by avoiding insect bites through insecticide spraying, home improvement, bed nets, hygienic food, medical care, laboratory practices, and testing. it can be diagnosed through a serological test, although the test is not very accurate. treatment is with medication, which may have severe side effects. dengue and chikungunya main article: dengue fever there are 50–100 million dengue virus infections annually. dengue fever is usually not fatal, but infection with one of four serotypes can increase later susceptibility to other serotypes, resulting in a potentially fatal disease called severe dengue. dengue fever is caused by a flavivirus and is spread mostly by the bite of the aedes aegypti mosquito. no treatment for either dengue or severe dengue exists beyond palliative care. the symptoms are high fever and flu-like symptoms. it is found in asia, latin america, and northern australia. chikungunya is an arboviral disease transmitted by a. albopictus and a. aegypti mosquitoes. the virus was first isolated from an outbreak in tanzania in 1952. chikungunya virus is a member of the genus alphavirus and family togaviridae. the word "chikungunya" is from the makonde language and means "that which bends up", referring to the effect of debilitating joint pain on the patient. symptoms, generally appearing 5–7 days after exposure, can be confused with dengue and include fever, rash, headache, joint pain, and swelling. the disease mainly occurs in africa and asia.