Tropical diseases: Wikis

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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 any of the diseases listed here.[2]

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.[3][4]

Contents

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

In 1975 the United Nations Children's Fund, the United Nations Development Programme, the World Bank and the World Health Organization established the Special Programme for Research and Training in Tropical Diseases (TDR) to focus on neglected infectious diseases which disproportionately affect poor and marginalized populations in developing regions of Africa, Asia, Central America and South America. The current TDR disease portfolio includes the following entries:[5]

  • Chagas disease
    (also called American trypanosomiasis) is a parasitic disease which occurs in the Americas, particularly in South America. Its pathogenic agent is a flagellate protozoan named Trypanosoma cruzi, which is [[Vector (epi
  • African trypanosomiasis
    or sleeping sickness, is a parasitic disease, caused by protozoa called trypansomes. The two responsible for African trypanosomiasis are Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense.These parasites are transmitted by the tsetse fly
  • Leishmaniasis
    caused by protozoan parasites of the genus Leishmania, and transmitted by the bite of certain species of sand fly.
  • Leprosy
    (or Hansen's disease) is a chronic infectious disease caused by Mycobacterium leprae. Leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions are the primary external symptom.[6] Left untreated, leprosy can be progressive, causing permanent damage to the skin, nerves, limbs, and eyes. Contrary to popular conception, leprosy does not cause body parts to simply fall off, and it differs from tzaraath, the malady described in the Hebrew scriptures and previously translated into English as leprosy.[7]
  • Lymphatic filariasis
    is a parasitic disease caused by thread-like parasitic filarial worms called nematode worms, all transmitted by mosquitoes. Loa loa is another filarial parasite transmitted by the deer fly. 120 million people are infected worldwide. It is carried by over half the population in the most severe endemic areas. [8] The most noticeable symptom is elephantiasis: a thickening of the skin and underlying tissues. Elephantiasis is caused by chronic infection by filarial worms in the lymph nodes. This clogs the lymph nodes and slows the draining of lymph fluid from a portion of the body.
  • Malaria
    Caused by a Protozoan parasites transmitted by female Anopheles mosquitoes, as they are the blood-feeders. The disease is caused by species of the genus Plasmodium. Malaria infects 300-500 million people each year, killing more than 1 million.[9]
  • Onchocerciasis
    (pronounced /ɒŋkoʊsɜrˈsaɪ.əsɪs/) or river blindness is the world's second leading infectious cause of blindness. It is caused by Onchocerca volvulus, a parasitic worm.[10] It is transmitted through the bite of a black fly. The worms spread throughout the body, and when they die, they cause intense itching and a strong immune system response that can destroy nearby tissue, such as the eye.[11 ] About 18 million people are currently infected with this parasite. Approximately 300,000 have been irreversibly blinded by it.[12 ]
  • Schistosomiasis
    (pronounced /ˌʃɪstoʊsɵˈmaɪ.əsɪs/) also known as schisto or snail fever, is a parasitic disease caused by several species of flatworm in areas with freshwater snails, which may carry the parasite. The most common form of transmission is by wading or swimming in lakes, ponds and other bodies of water containing the snails and the parasite. More than 200 million people worldwide are infected by schistosomiasis.[13]
  • Sexually transmitted infections
  • TB/HIV coinfection
  • Tuberculosis
    (abbreviated as TB), is a bacterial infection of the lungs or other tissues, which is highly prevalent in the world, with mortality over 50% if untreated. It is a communicable disease, transmitted by aerosol expectorant from a cough, sneeze, speak, kiss, or spit. Over one-third of the world's population has been infected by the TB bacterium.[14]
Although leprosy and tuberculosis are not exclusively tropical diseases, their high incidence in the tropics justifies their inclusion.

Other neglected tropical diseases

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

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.

Climate change, global warming caused by the greenhouse effect, and the resulting increase in global temperatures, are 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

Some of the strategies for controlling tropical diseases include:

  • Draining wetlands to reduce populations of insects and other 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.
  • 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.[19]

Epidemiology

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

References

  1. ^ "Guns, Germs, and Steel" by Jared Diamond
  2. ^ See the Wikipedia articles for the respective diseases
  3. ^ Deforestation Boosts Malaria Rates, Study Finds
  4. ^ UK 'faces tropical disease threat', BBC News
  5. ^ "Disease portfolio". Special Programme for Research and Training in Tropical Diseases. http://www.who.int/tdr/diseases/default.htm. Retrieved 2009-08-01.  
  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, IS; 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. ^ Frequently Asked Questions | CDC Malaria
  10. ^ http://www.worldbank.org/afr/gper/disease.htm The World Bank | Global Partnership to Eliminate Riverblindness. Accessed November 04, 2007.
  11. ^ "Causes of river blindness". http://www.sightsavers.org/What%20We%20Do/Eye%20Conditions/River%20Blindness/World1629.html. Retrieved 2008-01-28.  
  12. ^ "What is river blindness?". http://www.sightsavers.org/What%20We%20Do/Eye%20Conditions/River%20Blindness/World1622.html. Retrieved 2008-01-28.  
  13. ^ WHO | Schistosomiasis
  14. ^ World Health Organization (WHO). Tuberculosis Fact sheet N°104 - Global and regional incidence. March 2006, Retrieved on 6 October 2006.
  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. 17804846. ISSN 0028-4793. PMID 17804846. http://content.nejm.org/cgi/content/full/357/10/1018. 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
  19. ^ Jeffrey Sachs

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Travel guide

Up to date as of January 14, 2010

From Wikitravel

This article is a travel topic.

There are a number of Tropical diseases that present a health risk to travellers that are not present in their own countries. This article is meant as a travellers introduction to the more common aspects of the subject.

Hot humid environments provide ideal conditions for a number of diseases, or their vectors, to survive and spread. Some of these are transmitted by insects, others are water borne or may be carried by foods, often in meat. A number are transmitted by human contact.

Simple precautions — vaccinations, condoms, mosquito nets and insect repellents, and taking care with food and drink — can greatly reduce the risks.

Before travelling

Legal requirements

Many governments require visitors entering, or residents leaving, their countries to be vaccinated for a range of diseases. These requirements may often depend on what countries a traveller has visited or intends to visit. For example, if you have visited hot countries, most likely in Africa/Asia, then other countries may require evidence of Yellow fever vaccination before letting you in.

If you are bringing prescription medicine with you, carry a copy of the prescription.

Health requirements

For much travel, especially to tropical or "third world" countries, additional vaccinations or other precautions such as anti-malarial medication may be necessary.

Before starting your travels you should consult a doctor with experience in the field of travel medicine. You should do this at least 8 weeks before you plan to leave, to give time for vaccinations.

Heat and sun

Tropical sun is much stronger than at Northern latitudes. Sunglasses are almost essential. Many travellers need sunscreen. In places like China and India, many locals routinely carry parasols; consider emulating them. A hat can be a good idea, especially for balding men.

Consider Noel Coward's line "Only mad dogs and Englishmen go out in the noonday sun." You need to manage your time in the sun, avoiding the heat of the day. If partying until dawn is your style, do that, then sleep until 2. If not, consider rising around dawn to do your sightseeing before the crowds and the sun get too bad. Try a siesta, or a leisurely lunch in the shade, in the heat of the day.

Heatstroke can be a very serious illness. Drink plenty of bottled water. Consider carrying rehydration salts to replace what you lose by sweating. Soda water includes some salts.

See also Sunburn and sun protection.

Information sources

There are many sources of additional information for travelers:

  • Lice or mites
    • Ricketsial Infections - cause a broad range of diseases. Symptoms often include fever, headache and malaise as well as a rash. Antibiotic treatment is available.
      • Rocky Mountain spotted fever
      • Cat-scratch disease
      • Q fever - transmission by contact with soil and dust contaminated with carcasses from goat, sheep, and cattle and probably also by unpasteurized milk
      • (Epidemic) Typhus - transmitted by the human body louse, vaccine available.
  • Cryptosporidiosis/Cryptosporidium/Crypto. Found worldwide, this disease is an untreated and chlorine treated water risk. It can even be spread if an infected person bathes in a treated public swimming pool. It causes diarrhea, cramps and fever. Last about 10 days but feces carry infection for weeks. Prevention by avoiding mouth coming into contact with infected water or fecal matter and maintaining scrupulous toilet and bathing hygiene after being infected to prevent reinfection of self or others. There is no cure. Prevented by boiling all drinking water, including tap water, in infected areas.
  • Diarrhea, typically caused by some form of food poisoning. Also known as Delhi Belly, Montezuma's Revenge, and so on, this is the most common ailment of all for travellers. Extreme forms include cholera (watery massive diarrhea) and dysentery (bloody diarrhea). A cholera vaccine is available, but rarely used due to its ineffectiveness and the unlikeliness of the average traveller contracting the disease.
  • Hepatitis A. Can be spread by food contaminated with feces (unwashed hands), where the virus remains active for days. Symptoms may not appear for a month after infection, and may continue for as long as six months. Hepatitis A is common almost everywhere except in countries with a high standard of hygiene (see map of areas with high infection rates: US CDC FAQ). A vaccine is available for hepatitis A, but this will not protect against the more virulent forms of hepatitis, such as B C.
  • Typhoid fever. Caused by the bacterium Salmonella enterica Typhi. It causes high fever, headache, malaise as well as other symptoms and is a general health problem in all less developed countries. Transmission is by contaminated food and water, especially in rural areas. A vaccination is available but offers no absolute safety, so the best options are precautions with what you drink & eat. See also http://www.cdc.gov/travel/diseases/typhoid.htm.
  • Meat
    • Trichinosis - a tapeworm - from eating improperly cooked infected meats, particularly pork.
    • Hydatids - another tapeworm - from eating improperly cooked infected meats, particularly sheep/mutton. Can also be spread by dogs that have been eating infected meat.
  • Unpastuerized dairy products can transmit several diseases, including tuberculosis
  • Avian Influenza. A viral infection normally affecting birds but the Avian Influenza A virus has also been found, albeit extremely rarely, in some human infections. Current outbreaks among animals occurred in South-East Asia (Cambodia, China, Indonesia, Laos, Malaysia, Thailand, and Vietnam). The disease is transmitted to humans by contact with infected birds (esp. poultry) and their excrements and may cause serious disease. Precautions include avoiding contact to wild birds and their excrements (as fas as this is possible...). Avian influenza infection appears frequently in the news because it could be a source for new influenza strains to which no one has immunity and which have the potential to evolve to cause deadly epidemics. However, from the traveler's perspective the personal risk from avian influenza is extremely low. Travelers should obey recommendations on contact with poultry as a matter of civic duty, to prevent spreading the avian disease to birds in other countries. There is no vaccination available in the moment.
  • Ebola. Found largely in West Sub-Saharan Africa after contact with infected primates (human and non-human), this disease is fatal if not treated aggressively and early and has a 50-90% fatality rate. Get to a hospital immediately upon experiencing symptoms.
  • Hepatitis B and C. Can be spread by entry of blood or bodily fluids from an infected person into the body, such as through sexual contact, sharing of hypodermic needles, or blood transfusion or organ donation (theoretically, if screening were not performed). Unlike Hepatitis A, "Hepatitis B is not spread through food or water, sharing eating utensils, breastfeeding, hugging, kissing, coughing, sneezing or by casual contact" (US CDC FAQ) A vaccine is available to prevent Hepatitis B, but no vaccine is available to protect against Hepatitis C.
  • HIV (AIDS virus). HIV is transmitted in the same ways as hepatitis B. Abstinence or monogamy, safe sex, and an absolute ban on needle-sharing are wise precautions in any country of the world. Travellers should note that rare strains of HIV, such as HIV-2 or Group O HIV-1, occur predominantly in West Africa and may not be detected by some rapid HIV screening tests. Some strains of HIV prevalent in Africa and Asia may be more infectious by heterosexual intercourse (see avert.org for further information)
  • Influenza. The common Flu kills an estimated 36,000 Americans each year, and results in 200,000 hospitalizations per year. (CDC Flu Page) As a general precaution an annual vaccination is often recommended for the latest strains prevalent in the countries you are visiting.
  • Lassa fever. An acute viral illness that occurs in West Africa. In areas of Africa where the disease is endemic (that is, constantly present), Lassa fever is a significant cause of morbidity and mortality. While Lassa fever is mild or has no observable symptoms in about 80% of people infected with the virus, the remaining 20% have a severe multisystem disease. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50%.
  • Polio. Causes paralysis and nerve damage - easily preventable by an oral vaccination that should normally be given in early childhood. Although polio was nearly eradicated in recent years, it is currently experiencing a resurgence in several nations, so travelers should be sure that they have received proper vaccination and boosters.
  • SARS. Severe Acute Respiratory Syndrome - Caused by a common Corona virus that apparently crossed species and was highly infectious. Only a problem if undiagnosed travelers travel and spread the disease. Its control is an example of how unidentified (new) diseases are able to be controlled by simple but burdensome public health measures.
  • Tuberculosis. A third world disease due to poverty and poor health care. Can occur in first world countries where the health care system makes treatment expensive - generally responds to antibiotics but mis/incomplete treatment in some countries means antibiotic resistant strains are also problem.
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