Tropical medicine

Around 40% of the world's population live in the tropics. The Tropical medicine deals with tropical infectious diseases and other health problems in the tropics. It serves the inhabitants of tropical habitats and travelers who move through these areas. Malaria is probably the best known tropical disease. Chagas disease and dengue fever are other tropical diseases. The HI viruses that cause AIDS originally came from the tropics and are now found worldwide. The Ebola virus causes great fear.

What is tropical medicine?

Tropical medicine is important in the tropics themselves and outside the tropics, as long-distance travelers often feel infectious and non-infectious diseases only after they have left the tropics. The part of tropical medicine that deals with infectious diseases is very closely related to the fields of epidemiology, microbiology, virology, bacteriology and parasitology.

Parts of travel and aviation medicine also belong to tropical medicine. Hygiene medicine tries to improve the 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 in tropical medicine: many animal and especially insect species are hosts and often carriers of tropical pathogens.

Treatments & therapies

Malaria is the most common tropical disease. Worldwide, 2 billion people live in areas prone to malaria. Malaria patients are treated with anti-malarial drugs, which in mild cases kill the unicellular pathogens of the Plasmodium genus and lead to healing. In severe cases, however, the side effects of the drugs are great. Since the parasites are resistant, the drugs are still not successful. That is why prophylaxis is important.

Through exposure prophylaxis, people avoid mosquito bites from the disease-transmitting Anopheles mosquitoes. Mosquito nets, long-sleeved clothing, and insect repellents can help. Authorities fight the mosquitoes extensively with pesticides and by draining unnecessary accumulations of water. Anyone who temporarily travels through malaria areas takes anti-malarial drugs for a short period of time.

Mosquitoes also play a role in flavivirus-borne dengue fever. In Brazil, authorities are educating the population not to leave water standing around unnecessarily in flower vases or rain barrels. Small pools of water serve as a habitat for the larvae of the mosquito Aedes aegyoti. These mosquitoes transmit the virus disease, which is difficult to diagnose.

There is still a great mystery to science as to the origin and spread of the HIV virus that causes AIDS. Of course there is AIDS today in all climates and among all groups of people. The virus originally came from tropical Africa and was somehow transmitted from monkeys to humans. Nowadays, the percentage of the population infected with HIV is particularly high in some countries in Africa. In the development service, medical staff who come into contact with blood samples have a special responsibility to avoid self-infection and infection of patients through careful, sterile and hygienic working methods.

The Ebola virus makes a lot of headlines: in 2014, an Ebola epidemic broke out in West Africa. The disease, which may originally have been transmitted from bats to humans, can be transmitted from person to person through physical contact and contact with blood and body fluids. Actually there is no successful treatment method for hemorrhagic Ebola. The therapy of the often fatal disease is only aimed at alleviating the symptoms.

In South America, the single cell Trypanosoma cruzi causes Chagas disease. The disease is chronic for years and weakens the heart and circulation. Small mammals, such as dogs and armadillos, are a reservoir for the Trypanosoma parasites. Predatory bugs, i.e. insects, transmit the disease. Very simple hygiene measures were able to drastically reduce the incidence of this disease among the rural population: smooth, crack-free walls and roofs offer the predatory bugs fewer opportunities to hide, and the consistent locking out of dogs from the living areas of the farmers reduces the disease transmission from the pathogen reservoir to humans.

Diagnosis & examination methods

The malaria disease caused by unicellular parasites of the genus Plasmodium appears in the blood count. Blood cells stained with special staining methods make the malaria pathogens visible. Most of the time the red blood cells are affected. It is important to determine the type of malaria. All malaria pathogens belong to the genus Plasmodium. But in this genus there are different species that cause malaria diseases of different severity.

Dengue fever is not so easily detectable in the blood count. Since the disease is caused by viruses, a reliable diagnosis is only the molecular biological proof of the genome of the flaviviruses. This happens via the DNA-replicating polymerase chain reaction (PCR). With the ELISA rapid test, an infection by HIV viruses can now be determined cheaply and quickly. However, the rapid test also provides false positive results that incorrectly suggest an HIV infection. If a positive rapid test result is available, a more expensive detection test is therefore necessary.

The Ebola virus can only be detected by a complex, molecular biology analysis based on the polymerase chain reaction. Chagas disease can be diagnosed in the initial phase in the blood count. If the disease has become chronic, antibodies can be detected. In xenodiagnosis, parasite-free predatory bugs eat a blood meal on the patient. Then the unicellular parasites can be detected in the predatory bugs.

In addition to the tropical diseases mentioned, there are many other tropical diseases. The problem with diagnosis is that doctors may not know that patients are returning from the tropics. With today's mobility, however, it is always important to consider a tropical disease as a diagnostic option and to ask patients about their travels.