The tropical habitat is home to approximately 40% of the world’s population. Tropical medicine deals with tropical infectious diseases and other health problems in the tropics. It thus serves the inhabitants of tropical habitats and travelers passing through these areas. Malaria is probably the best known tropical disease. Chagas disease and dengue fever are other tropical diseases. The AIDS-causing HI viruses also originally came from the tropics and now occur worldwide. Great fear is caused by the Ebola virus.
What is tropical medicine?
Tropical medicine deals with tropical infectious diseases and other health problems in the tropics. Tropical medicine is important in the tropics themselves and also outside the tropics, because long-distance travelers often do not feel infectious and noninfectious diseases until they leave the tropics. The part of tropical medicine that deals with infectious diseases is very much related to the specialties of epidemiology, microbiology, virology, bacteriology, and parasitology. Parts of travel and aviation medicine are also part of tropical medicine. Hygiene medicine tries to improve general hygiene conditions in the tropics. Veterinary medicine helps to improve the hygienic keeping of farm animals in the tropics. Medical entomology and zoology are important auxiliary disciplines of tropical medicine: many animal and especially insect species are hosts and often vectors of tropical pathogens.
Treatments and therapies
Malaria is the most common tropical disease. Worldwide, 2 billion people live in areas that are at risk for malaria. Malaria patients are treated with antimalarial drugs, which in mild cases kill the single-cell pathogens of the genus Plasmodium and lead to cure. In severe cases, however, the side effects of the drugs are great. Since the parasites are resistant, the drugs then still do not lead to success. Therefore, prophylaxis is important. Through exposure prophylaxis, people avoid mosquito bites from the disease-carrying Anopheles mosquitoes. Mosquito nets, long-sleeved clothing and insect repellents are helpful. Authorities control mosquitoes extensively with pesticides and by draining unnecessary water accumulations. Those traveling temporarily through malaria areas take antimalarial medication for a short time as a preventive measure. Mosquitoes also play a role in dengue fever, which is transmitted by flaviviruses. In Brazil, authorities educate the population not to leave water lying around openly in flower vases or rain barrels unnecessarily. Small accumulations of water serve as a habitat for the larvae of the mosquito Aedes aegyoti. These mosquitoes transmit the viral disease, which is difficult to diagnose. Science is still faced with a great mystery as to the origin and spread of the AIDS-causing HI virus. Of course, AIDS exists today in all climatic zones and among all groups of people. But originally the virus came from tropical Africa and was somehow transmitted from monkeys to humans. Today, in some African countries, the percentage of the population infected with HIV is particularly high. In the development service, medical personnel who have contact with blood samples have a special responsibility to avoid self-infection and infection of patients by working carefully, sterilely and hygienically. Much headline news comes from the Ebola virus: in 2014, West Africa experienced an Ebola epidemic. The disease, which may have originally been transmitted to humans by bats, is transmissible from person to person through physical contact and contact with blood and body fluids. Actually, there is no successful treatment method for Ebola hemorrhagic fever. Therapy for the often fatal disease is aimed only at alleviating symptoms. In South America, the protozoan Trypanosoma cruzi causes Chagas disease. The disease runs chronically for years and weakens the heart and circulation. Small mammals, for example dogs and armadillos, form a reservoir for the Trypanosoma parasites. Predatory bugs, or insects, transmit the disease. Very simple hygiene measures could drastically reduce the incidence of this disease among the rural population: Smooth, crack-free walls and roofs provide fewer hiding places for the predatory bugs, and consistently keeping dogs out of farmers’ living areas reduces disease transmission from the pathogen reservoir to humans.
Diagnosis and examination methods
Malaria disease caused by unicellular parasites of the genus Plasmodium appears in the blood picture. Blood cells stained with special staining methods reveal the malaria pathogens. Most often, the red blood cells are affected. It is important to determine the malaria species. All malaria pathogens belong to the genus Plasmodium. But in this genus there are different species that cause different severity of malaria disease. Dengue fever is not as easily detectable in blood work. Since the disease is caused by viruses, a reliable diagnosis can only be made by molecular biological detection of the genetic material of the flaviviruses. This is done using the DNA amplifying polymerase chain reaction (PCR). With the ELISA rapid test, an infection by HIV viruses can nowadays be detected cheaply and quickly. However, the rapid test also provides false positive results that falsely suggest HIV infection. Therefore, if a positive rapid test result is obtained, a more expensive detection test is necessary. The Ebola virus is only detectable by a sophisticated molecular biology analysis based on the polymerase chain reaction. Chagas disease is diagnosable in the blood count during the initial phase. When chronic disease progression has occurred, antibodies can be detected. In xenodiagnosis, parasite-free predatory bugs take a blood meal on the patient. Afterwards, the unicellular parasites in the predatory bugs can be detected. Besides the mentioned tropical diseases, there are many other tropical diseases. The problem with diagnosis is that doctors may not know that patients are tropical returnees. However, with today’s mobility, it is always important to consider a tropical disease as a diagnostic possibility and to question patients about their travels.
