Malaria is a tropical infectious disease that is transmitted through the bite of the female anopheles mosquito. If left untreated, malaria can be fatal; prophylaxis and medication can help.
- Malaria is caused by a parasite of the genus Plasmodium, which is transmitted by the anopheles mosquito.
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Malaria is one of the most important infectious diseases in the world: The World Health Organization (WHO) estimates the number of malaria infections per year at around 219 million with 435,000 fatalities. The disease occurs in tropical and subtropical regions – mainly in Africa, Asia, Central and South America. Due to the increasing networking of the industrialized countries with the tropical countries, malaria has become the most important imported tropical disease in Europe. In Germany around 1,000 cases are currently reported each year.
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Safety when traveling: there is a risk of infection here
Cause: parasites and mosquito bites
Malaria is caused by a single-celled parasite of the genus Plasmodium. Five types of pathogens lead to four different forms of malaria in humans:
Malaria tropica is caused by Plasmodium falciparum. This type of malaria is the most common and can be fatal in a few days if treated too late or not at all.
Malaria tertiana is caused by Plasmodium vivax and Plasmodium ovale. Typical of this rarely life-threatening form of malaria are regular attacks of fever every other day.
Quartana malaria is caused by Plasmodium malariae. This non-life-threatening form of malaria is the rarest; fever attacks every third day are typical.
Knowlesi malaria is caused by Plasmodium knowlesi evoked. The so-called "monkey malaria" occurs only in Southeast Asia and mainly affects monkeys there, and more rarely humans.
The plasmodia are usually transmitted through the bite of a female anopheles mosquito. Occasionally, the pathogen is transmitted from the mother to the unborn child during pregnancy. Transmission through blood supplies or contaminated injection needles is also possible, but rarely. Other than that, malaria is not contagious.
When an infected mosquito bites, the infectious forms of the pathogen (sporozoites) enter the human bloodstream with the mosquito's saliva. They reach the liver with the blood and multiply there. Their descendants are called merozoites. These leave the liver after a few days and attack red blood cells (erythrocytes), where they continue to multiply, destroy blood cells and attack new ones. This process triggers the typical complaints.
Malaria: Incubation Period and Symptoms
Malaria usually occurs no earlier than seven days after infection. However, it can take weeks before the first signs become noticeable. The disease often manifests itself in a similar way to the flu with a high fever (over 38 degrees Celsius), chills, headaches and aching limbs. Sometimes people also have other symptoms such as dry cough, abdominal pain, and sometimes nausea, vomiting and diarrhea. In detail, the incubation period and symptoms differ depending on the respective form of malaria:
People with malaria tropica have an irregular fever rhythm and the shortest incubation period (seven to 15 days). Diarrhea, vomiting and respiratory problems are common.
The incubation period of malaria tertiana is between twelve and 18 days. Within a few days there is often a rhythmization of the fever attacks, which then occur every 48 hours. Typically chills occur in the late afternoon hours, during which the fever rises very quickly to values around 40 ° C. Relapses are possible for up to 40 years.
Quartana malaria takes the longest to break out (between 18 and 40 days). Here the fever occurs every 72 hours.
In Knowlesi malaria, the fever is often irregular or even constant.
Diagnosing malaria through blood tests
Malaria cannot be diagnosed on the basis of the symptoms alone, as its typical signs also occur in other illnesses such as flu, gastrointestinal infections, the onset of inflammation of the liver (hepatitis) and other blood diseases. Any unclear febrile illness after a stay in the tropics must therefore consider a malaria infection.
For a precise diagnosis, blood is taken from the person concerned: the pathogens can be detected in the blood under a microscope. Is there an infection with the life-threatening Plasmodium falciparum or Plasmodium knowlesi before, the next step is to determine the severity of the disease, as this helps determine the therapy. In addition to the parasite density, heart rate and blood pressure, blood values and urine volume are also determined. An EKG and a chest x-ray may also be necessary.
Rapid tests based on the detection of parasite-specific antigens have been available for some years. However, these cannot distinguish between the different types of plasmodia and incorrectly indicate negative results if the parasite density in the blood is too high or too low. Therefore, if there is a justified suspicion of malaria and a negative rapid test, further diagnostics must always be carried out.
If the parasite density is very low or if there is a mixed infection with different pathogens, a blood sample can also be examined for Plasmodia genetic material (DNA). However, this method is unsuitable for acute diagnosis because it takes a comparatively long time (several hours) and is very expensive.
Medicines: Malaria therapy with tablets
There are a number of drugs used to treat malaria. However, some of the parasites are resistant to the active ingredients, which makes treatment difficult. The medication the doctor uses depends on the type of malaria present and what medication may have been taken for malaria prophylaxis.
Immediate hospitalization is required if tropica malaria is suspected. Those affected with uncomplicated tropic malaria can usually be treated with tablets – mostly the active ingredient combinations atovaquone plus proguanil or artemether plus lumefantrine or dihydroartemisinin plus piperaquine are used. The duration of therapy is three days.
In complicated tropical malaria (for example, if the central nervous system, kidneys or other organs are affected), the affected person is given infusions with artesunate under intensive care conditions. Oral therapy with atovaquone plus proguanil follows.
If artesunate is not available, quinine infusions can be used (in combination with doxycycline or clindamycin). In addition, fever-lowering measures such as leg wraps and paracetamol are used. Drug treatment usually lasts over six days.
Tertiana and quartana malaria can generally be treated on an outpatient basis. The drug of choice for malaria tertiana is Artemether plus Lumefantrine or Atovaquon plus Proguanil – each in the form of tablets. This is usually followed by a two-week intake of primaquine to prevent relapses. Quartana malaria is usually treated with four doses of chloroquine within the first 48 hours.
The therapy of Knowlesi malaria is the same as for malaria tropica. Here, too, therapy in the hospital, possibly even in the intensive care unit, is necessary.
Malaria during pregnancy or breastfeeding should always be consulted with a tropical medicine institution – the disease can lead to life-threatening complications for both mother and child.
Course and prognosis
Tropica malaria and Knowlesi malaria are life-threatening infectious diseases that must be treated in a hospital. If they are treated correctly and in good time, they are basically curable.
If left untreated, they can cause damage to the central nervous system, heart, lungs and kidneys. Serious consequences are – depending on the organ affected – acute kidney failure, pulmonary edema or circulatory shock. In Germany, 0.5 to one percent of malaria cases brought in are fatal.
Malaria tertiana and malaria quartana heal mostly untreated. In tertian malaria, however, relapses are possible, especially if there was no follow-up treatment with primaquine.
After having overcome malaria, humans do not acquire any natural defenses (immunity), so a new infection is possible at any time. However, after multiple infections, residents of risk areas can become partially immune over time. This partial immunity does not prevent the infection, but has the effect that the symptoms of the disease are weakened or completely absent.
Prophylaxis instead of vaccination
So far there is no effective vaccination against malaria. Travelers in risk areas still have two options for malaria prophylaxis:
The doctor must decide in an individual consultation which type of prophylaxis makes sense in each individual case.
Protection against mosquito bites
If you travel to malaria-prone areas, you can do a lot yourself to protect yourself against infection with malaria from the anopheles mosquito. Travel during the rainy season is not recommended, and staying at local breeding grounds for the anopheles mosquito (for example ditches, water holes and barrels) is not recommended. Since the anopheles mosquito is nocturnal, it is recommended that you do not stay outdoors during this time.
It is also advisable to wear long pants and long-sleeved tops in light colors and to protect yourself with special mosquito repellants. Mosquito nets on windows and over the bed protect you while you sleep.
Malaria prophylaxis with tablets
Depending on the travel destination, time and style as well as the resistance level of the parasites, it may be necessary to take medication to prevent malaria. This chemoprophylaxis does not offer absolute protection – like a vaccination – against malaria, but increases safety. The most common drugs are atovaquone / proguanil and doxycycline, in certain cases also mefloquine. Depending on the drug, they are taken regularly a few days before to one or four weeks after the stay in a risk area.
Chemoprophylaxis is not absolutely necessary in areas with a low or medium risk of malaria. Here, however, a reserve medication should be carried with you, which can be taken in the event of symptoms suspecting malaria and unavailable medical help (standby therapy). However, this procedure is only an emergency measure until medical help is reached.
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