Tropical disease

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Tropical diseases are diseases that are prevalent in or unique to tropical and subtropical regions. [1] 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. However, many were present in northern Europe and northern America in the 17th and 18th centuries before modern understanding of disease causation. The initial impetus for tropical medicine was to protect the health of colonial settlers, notably in India under the British Raj. [2] 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.

Tropics region of the Earth surrounding the Equator

The tropics are the region of the Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at 23°26′12.2″ (or 23.43674°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′12.2″ (or 23.43674°) S; these latitudes correspond to the axial tilt of the Earth. The tropics are also referred to as the tropical zone and the torrid zone. The tropics include all the areas on the Earth where the Sun contacts a point directly overhead at least once during the solar year - thus the latitude of the tropics is roughly equal to the angle of the Earth's axial tilt.

Subtropics Geographic and climate zone

The subtropics are geographic and climate zones located roughly between the tropics at latitude 23.5° and temperate zones north and south of the Equator.

Temperate climate hovers around the same temperature

In geography, the temperate or tepid climates of Earth occur in the middle latitudes, which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout the year and more distinct seasonal changes compared to tropical climates, where such variations are often small. They typically feature four distinct seasons, Summer the warmest, Autumn the transitioning season to Winter, the colder season, and Spring the transitioning season from winter back into summer. In the northern hemisphere, the year starts with winter, transitions in the first halfyear through spring into summer, which is in mid-year, then at the second halfyear through autumn into winter at year-end. In the southern hemisphere, the seasons are swapped, with summer in between years and winter in mid-year.


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]

Tropical rainforest specific ecosystem

Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as lowland equatorial evergreen rainforest. True rainforests are typically found between 10 degrees north and south of the equator ; they are a sub-set of the tropical forest biome that occurs roughly within the 28 degree latitudes. Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest that also includes the more extensive seasonal tropical forests.

Deforestation Conversion of forest to non-forest for human use

Deforestation, clearance, clearcutting or clearing is the removal of a forest or stand of trees from land which is then converted to a non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated deforestation occurs in tropical rainforests. About 31% of Earth's land surface is covered by forests.

Immigration Movement of people into another country or region to which they are not native

Immigration is the international movement of people into a destination country of which they are not natives or where they do not possess citizenship in order to settle or reside there, especially as permanent residents or naturalized citizens, or to take up employment as a migrant worker or temporarily as a foreign worker.

Health programmes

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.

Neglected tropical diseases A diverse group of tropical infection diseases which are common in developing countries

Neglected tropical diseases (NTDs) are a diverse group of tropical infections which 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 helminths. These diseases are contrasted with the big three infectious diseases, which generally receive greater treatment and research funding. In sub-Saharan Africa, the effect of these diseases as a group is comparable to malaria and tuberculosis. NTD co-infection can also make HIV/AIDS and tuberculosis more deadly.

Africa The second largest and second most-populous continent, mostly in the Northern and Eastern Hemispheres

Africa is the world's second largest and second most-populous continent, being behind Asia in both categories. At about 30.3 million km2 including adjacent islands, it covers 6% of Earth's total surface area and 20% of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Isthmus of Suez and the Red Sea to the northeast, the Indian Ocean to the southeast and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognised sovereign states (countries), nine territories and two de facto independent states with limited or no recognition. The majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere.

Asia Earths largest and most populous continent, located primarily in the Eastern and Northern Hemispheres

Asia is Earth's largest and most populous continent, located primarily in the Eastern and Northern Hemispheres. It shares the continental landmass of Eurasia with the continent of Europe and the continental landmass of Afro-Eurasia with both Europe and Africa. Asia covers an area of 44,579,000 square kilometres (17,212,000 sq mi), about 30% of Earth's total land area and 8.7% of the Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilizations. Asia is notable for not only its overall large size and population, but also dense and large settlements, as well as vast barely populated regions. Its 4.5 billion people constitute roughly 60% of the world's population.

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.

Diseases of poverty are diseases that are more prevalent in low-income populations. They include infectious diseases, as well as diseases related to malnutrition and poor health behaviors. Poverty is one of the major social determinants of health. The World Health Report, 2002 states that diseases of poverty account for 45% of the disease burden in the countries with high poverty rate which are preventable or treatable with existing interventions. Diseases of poverty are often co-morbid and ubiquitous with malnutrition.

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: [5]

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: [20]

DiseaseCausative AgentComments
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, Zika 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.[ 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. [21] [22] 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. [23] 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

Disability-adjusted life year for tropical diseases per 100,000 inhabitants. These include trypanosomiasis, chagas disease, schistosomiasis, leishmaniasis, lymphatic filariasis, onchocerciasis.
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Disability-adjusted life year for tropical diseases per 100,000 inhabitants. These include trypanosomiasis, chagas disease, schistosomiasis, leishmaniasis, lymphatic filariasis, onchocerciasis.
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Some of the strategies for controlling tropical diseases include:

See also

Related Research Articles

African trypanosomiasis parasitic disease

African trypanosomiasis, also known as sleeping sickness, is an insect-borne parasitic disease of humans and other animals. It is caused by protozoa of the species Trypanosoma brucei. There are two types that infect humans, Trypanosoma brucei gambiense (TbG) and Trypanosoma brucei rhodesiense (TbR). TbG causes over 98% of reported cases. Both are usually transmitted by the bite of an infected tsetse fly and are most common in rural areas.

<i>Loa loa</i> species of worm

Loa loa is the filarial nematode (roundworm) species that causes Loa loa filariasis. Loa loa actually means "worm worm", but is commonly known as the "eye worm", as it localizes to the conjunctiva of the eye. Loa loa is commonly found in Africa. It mainly inhabits rain forests in West Africa and has native origins in Ethiopia. The disease caused by Loa loa is called loiasis and belongs to the so-called neglected diseases.

Diethylcarbamazine chemical compound

Diethylcarbamazine (DEC) is a medication used in the treatment of filariasis including lymphatic filariasis, tropical pulmonary eosinophilia, and loiasis. It may also be used for prevention of loiasis in those at high risk. While it has been used for onchocerciasis, ivermectin is preferred. It is taken by mouth.

Schistosomiasis Human disease caused by parasitic worms called schistosomes

Schistosomiasis, also known as snail fever and bilharzia, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody stool, or blood in the urine. Those who have been infected for a long time may experience liver damage, kidney failure, infertility, or bladder cancer. In children, it may cause poor growth and learning difficulty.

Onchocerciasis Human helminthiasis

Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm Onchocerca volvulus. Symptoms include severe itching, bumps under the skin, and blindness. It is the second-most common cause of blindness due to infection, after trachoma.

Filariasis Parasitic disease caused by a family of nematode worms

Filariasis is a parasitic disease caused by an infection with roundworms of the Filarioidea type. These are spread by blood-feeding diptera such as black flies and mosquitoes. This disease belongs to the group of diseases called helminthiases.

Helminthiasis Macroparasitic disease in which a part of the body is infected with parasitic worms

Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic worms, known as helminths. There are numerous species of these parasites, which are broadly classified into tapeworms, flukes, and roundworms. They often live in the gastrointestinal tract of their hosts, but they may also burrow into other organs, where they induce physiological damage.

Liverpool School of Tropical Medicine

The Liverpool School of Tropical Medicine (LSTM) is a higher education institution with degree awarding powers and registered charity located in Liverpool, United Kingdom. Established in 1898, it was the first institution in the world dedicated to research and teaching in tropical medicine. The school has a research portfolio of over £220 million, assisted by funding from organisations such as the Bill & Melinda Gates Foundation, Wellcome Trust and Department for International Development (DFID).

Tropical medicine medical specialty

Tropical medicine is an interdisciplinary branch of medicine that deals with health issues that occur uniquely, are more widespread, or are more difficult to control in tropical and subtropical regions.

<i>Brugia malayi</i> species of parasitic worm

Brugia malayi is a nematode (roundworm), one of the three causative agents of lymphatic filariasis in humans. Lymphatic filariasis, also known as elephantiasis, is a condition characterized by swelling of the lower limbs. The two other filarial causes of lymphatic filariasis are Wuchereria bancrofti and Brugia timori, which both differ from B. malayi morphologically, symptomatically, and in geographical extent.

<i>Onchocerca volvulus</i> species of parasitic nematode, cause of river blindness in humans

Onchocerca volvulus is a nematode that causes onchocerciasis, and is the second-leading cause of blindness worldwide after trachoma. It is one of the 20 neglected tropical diseases listed by the World Health Organization, with elimination from certain countries expected by 2020.

Acanthocheilonemiasis is a rare tropical infectious disease caused by a parasite known as Acanthocheilonema perstans. It can cause skin rashes, abdominal and chest pains, muscle and joint pains, neurological disorders and skin lumps. It is mainly found in Africa. The parasite is transmitted through the bite of small flies. Studies show that there are elevated levels of white blood cells.

Lymphatic filariasis tropical helminthiasis

Lymphatic filariasis, also known as elephantiasis, is a human disease caused by parasitic worms known as filarial worms. Most cases of the disease have no symptoms. Some people, however, develop a syndrome called elephantiasis, which is marked by severe swelling in the arms, legs, breasts, or genitals. The skin may become thicker as well, and the condition may become painful. The changes to the body have the potential to harm the person's social and economic situation.

Globalization, the flow of information, goods, capital, and people across political and geographic boundaries, allows infectious diseases to rapidly spread around the world, while also allowing the alleviation of factors such as hunger and poverty, which are key determinants of global health. The spread of diseases across wide geographic scales has increased through history. Early diseases that spread from Asia to Europe were bubonic plague, influenza of various types, and similar infectious diseases.

Medical entomology study of insect impacts on human health

The discipline of medical entomology, or public health entomology, and also veterinary entomology is focused upon insects and arthropods that impact human health. Veterinary entomology is included in this category, because many animal diseases can "jump species" and become a human health threat, for example, bovine encephalitis. Medical entomology also includes scientific research on the behavior, ecology, and epidemiology of arthropod disease vectors, and involves a tremendous outreach to the public, including local and state officials and other stake holders in the interest of public safety, finally in current situation related to one health approach mostly health policy makers recommends to widely applicability of medical entomology for disease control efficient and best fit on achieving development goal and to tackle the newly budding zoonotic diseases. Thoughtful to have and acquaint with best practice of Med. Entomologist to tackle the animal and public health issues together with controlling arthropods born diseases by having Medical Entomologists’ the right hand for bringing the healthy world [Yon w].

Vector (epidemiology) agent that carries and transmits an infectious pathogen into another living organism

In epidemiology, a disease vector is any agent which carries and transmits an infectious pathogen into another living organism; most agents regarded as vectors are organisms, such as intermediate parasites or microbes, but it could be an inanimate medium of infection such as dust particles.

Lorenzo Savioli is a senior United Nations civil servant and the director of the Department of Control of Neglected Tropical Diseases at the World Health Organization Headquarters in Geneva, Switzerland.

Mosquito-borne disease

Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. They can transmit disease without being affected themselves. Nearly 700 million people get a mosquito-borne illness each year resulting in over one million deaths.

Filarioidea superfamily of spirurian roundworms

The Filarioidea are a superfamily of highly specialised parasitic nematodes. Species within this superfamily are known as filarial worms or filariae. Infections with parasitic filarial worms cause disease conditions generically known as filariasis. Drugs against these worms are known as filaricides.


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Further reading