Tropical disease

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Tropical diseases are diseases that are prevalent in or unique to tropical and subtropical regions. The diseases are less prevalent in temperate climates, due in part to the occurrence of a cold season, which controls the insect population by forcing hibernation.[1] Insects such as mosquitoes and flies are by far the most common disease carrier, or vector. These insects may carry a parasite, bacterium or virus that is infectious to humans and animals. Most often disease is transmitted by an insect "bite", which causes transmission of the infectious agent through subcutaneous blood exchange. Vaccines are not available for most of the diseases listed here, and many do not have cures.

Human exploration of tropical rainforests, deforestation, rising immigration and increased international air travel and other tourism to tropical regions has led to an increased incidence of such diseases.[2][3]

Special Programme for Research and Training in Tropical Diseases (TDR)[edit]

In 1975 the Special Programme for Research and Training in Tropical Diseases (TDR) was established to focus on neglected infectious diseases which disproportionately affect poor and marginalized populations in developing regions of Africa, Asia, Central America and South America. It was established at the World Health Organization, which is the executing agency, and is co-sponsored by the United Nations Children's Fund, United Nations Development Programme, the World Bank and the World Health Organization.

TDR's vision is to foster an effective global research effort on infectious diseases of poverty in which disease endemic countries play a pivotal role. It has a dual mission of developing new tools and strategies against these diseases, and to develop the research and leadership capacity in the countries where the diseases occur. The TDR secretariat is based in Geneva, Switzerland, but the work is conducted throughout the world through many partners and funded grants.

Some examples of work include helping to develop new treatments for diseases, such as ivermectin for onchocerciasis (river blindness); showing how packaging can improve use of artemesinin-combination treatment (ACT) for malaria; demonstrating the effectiveness of bednets to prevent mosquito bites and malaria; and documenting how community-based and community-led programmes increases distribution of multiple treatments. TDR history

The current TDR disease portfolio includes the following entries:[4]

Although leprosy and tuberculosis are not exclusively tropical diseases, their high incidence in the tropics justifies their inclusion.

Other neglected tropical diseases[edit]

Additional neglected tropical diseases include:[15]

Disease Causative Agent Comments
Hookworm Ancylostoma duodenale and Necator americanus
Trichuriasis Trichuris trichiura
Treponematoses Treponema pallidum pertenue, Treponema pallidum endemicum, Treponema pallidum carateum, Treponema pallidum pallidum
Buruli ulcer Mycobacterium ulcerans
Human African trypanosomiasis Trypanosoma brucei, Trypanosoma gambiense
Dracunculiasis Dracunculus medinensis
Leptospirosis Leptospira
Strongyloidiasis Strongyloides stercoralis
Foodborne trematodiases Trematoda
Neurocysticercosis Taenia solium
Scabies Sarcoptes scabiei
Flavivirus Infections Yellow fever virus, West Nile virus, dengue virus, Tick-borne encephalitis virus

Some tropical diseases are very rare, but may occur in sudden epidemics, such as the Ebola hemorrhagic fever, Lassa fever and the Marburg virus. There are hundreds of different tropical diseases which are less known or rarer, but that, nonetheless, have importance for public health.

Relation of climate to tropical diseases[edit]

The so-called "exotic" diseases in the tropics have long been noted both by travelers, explorers, etc., as well as by physicians. One obvious reason is that the hot climate present during all the year and the larger volume of rains directly affect the formation of breeding grounds, the larger number and variety of natural reservoirs and animal diseases that can be transmitted to humans (zoonosis), the largest number of possible insect vectors of diseases. It is possible also that higher temperatures may favor the replication of pathogenic agents both inside and outside biological organisms. Socio-economic factors may be also in operation, since most of the poorest nations of the world are in the tropics. Tropical countries like Brazil, which have improved their socio-economic situation and invested in hygiene, public health and the combat of transmissible diseases have achieved dramatic results in relation to the elimination or decrease of many endemic tropical diseases in their territory.[citation needed]

Climate change, global warming caused by the greenhouse effect, and the resulting increase in global temperatures, are possibly causing tropical diseases and vectors to spread to higher altitudes in mountainous regions, and to higher latitudes that were previously spared, such as the Southern United States, the Mediterranean area, etc.[16][17] For example, in the Monteverde cloud forest of Costa Rica, global warming enabled Chytridiomycosis, a tropical disease, to flourish and thus force into decline amphibian populations of the Monteverde Harlequin frog.[18] Here, global warming raised the heights of orographic cloud formation, and thus produced cloud cover that would facilitate optimum growth conditions for the implicated pathogen, B. dendrobatidis.

Prevention and treatment of tropical diseases[edit]

Some of the strategies for controlling tropical diseases include:

  • Draining wetlands to reduce populations of insects and other vectors, or introducing natural predators of the vectors.
  • The application of insecticides and/or insect repellents) to strategic surfaces such as clothing, skin, buildings, insect habitats, and bed nets.
  • The use of a mosquito net over a bed (also known as a "bed net") to reduce nighttime transmission, since certain species of tropical mosquitoes feed mainly at night.
  • Use of water wells, and/or water filtration, water filters, or water treatment with water tablets to produce drinking water free of parasites.
  • Sanitation to prevent transmission through human waste.
  • In situations where vectors (such as mosquitoes) have become more numerous as a result of human activity, a careful investigation can provide clues: for example, open dumps can contain stagnant water that encourage disease vectors to breed. Eliminating these dumps can address the problem. An education campaign can yield significant benefits at low cost.
  • Development and use of vaccines to promote disease immunity.
  • Pharmacologic pre-exposure prophylaxis (to prevent disease before exposure to the environment and/or vector).
  • Pharmacologic post-exposure prophylaxis (to prevent disease after exposure to the environment and/or vector).
  • Pharmacologic treatment (to treat disease after infection or infestation).
  • Assisting with economic development in endemic regions. For example, by providing microloans to enable investments in more efficient and productive agriculture. This in turn can help subsistence farming to become more profitable, and these profits can be used by local populations for disease prevention and treatment, with the added benefit of reducing the poverty rate.[citation needed]
Disability-adjusted life year for tropical diseases per 100,000 inhabitants. These include trypanosomiasis, chagas disease, schistosomiasis, leishmaniasis, lymphatic filariasis, onchocerciasis.
  no data
  ≤100
  100-200
  200-300
  300-400
  400-500
  500-600
  600-700
  700-800
  800-900
  900-1000
  1000-1500
  ≥1500

See also[edit]

References[edit]

  1. ^ "Guns, Germs, and Steel" by Jared Diamond
  2. ^ Deforestation Boosts Malaria Rates, Study Finds
  3. ^ UK 'faces tropical disease threat', BBC News
  4. ^ "Disease portfolio". Special Programme for Research and Training in Tropical Diseases. Retrieved 2009-08-01. 
  5. ^ Chagas Disease After Organ Transplantation --- United States, 2001
  6. ^ Kenneth J. Ryan and C. George Ray, Sherris Medical Microbiology Fourth Edition McGraw Hill 2004.
  7. ^ Leviticus 13:59, Artscroll Tanakh and Metsudah Chumash translations, 1996 and 1994, respectively.
  8. ^ Supali, T.; Ismid, I.S.; Wibowo, H.; Djuardi, Y.; Majawati, E.; Ginanjar, P.; Fischer, P. (Aug 2006). "Estimation of the prevalence of lymphatic filariasis by a pool screen PCR assay using blood spots collected on filter paper". Tran R Soc Trop Med Hyg 100 (8): 753–9. doi:10.1016/j.trstmh.2005.10.005. ISSN 0035-9203. PMID 16442578. 
  9. ^ http://www.cdc.gov/malaria/
  10. ^ http://www.worldbank.org/afr/gper/disease.htm The World Bank | Global Partnership to Eliminate Riverblindness. Retrieved 2007-11-04.
  11. ^ "Causes of river blindness". Archived from the original on 2007-12-29. Retrieved 2008-01-28. 
  12. ^ "What is river blindness?". Archived from the original on 2007-12-15. Retrieved 2008-01-28. 
  13. ^ WHO | Schistosomiasis
  14. ^ World Health Organization (WHO). Tuberculosis Fact sheet N°104 - Global and regional incidence. March 2006. Retrieved 2006-10-06.
  15. ^ Hotez, P. J.; Molyneux, DH; Fenwick, A; Kumaresan, J; Sachs, SE; Sachs, JD; Savioli, L (September 2007). "Control of Neglected Tropical Diseases". The New England Journal of Medicine 357 (10): 1018–1027. doi:10.1056/NEJMra064142. ISSN 0028-4793. PMID 17804846. 17804846. Retrieved 2008-01-21. 
  16. ^ Climate change brings malaria back to Italy The Guardian 6 January 2007
  17. ^ BBC Climate link to African malaria 20 March 2006.
  18. ^ Pounds, J. Alan et al. "Widespread Amphibian Extinctions from Epidemic Deisease Driven by Global Warming." Nature 439.12 (2006) 161-67

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