What is the incubation period for malaria

malaria

Brief overview

  • What is malaria A tropical-subtropical infectious disease caused by single-cell parasites (plasmodia). Depending on the type of pathogen, different forms of malaria develop (malaria tropica, malaria tertiana, malaria quartana, Knowlesi malaria), although mixed infections are also possible.
  • Occurrence: tropical and subtropical regions worldwide (except Australia). Africa is particularly affected. Every year, an estimated 200 million people worldwide develop malaria, of which around 600,000 die (mostly children).
  • Infection: Usually through the bite of blood-sucking anopheles mosquitoes that are infected with malaria pathogens.
  • Symptoms: Fever attacks (hence the name intermittent fever), the rhythm of which depends on the type of malaria, are typical. Other possible symptoms are, for example, a general feeling of illness, headache and body aches, diarrhea, nausea, vomiting and dizziness.
  • Therapy: Among other things, it depends on the form of malaria. The pathogens are treated with anti-parasitic drugs. Symptoms and complications are also treated as required.
  • Forecast: In principle, all malaria can be cured. In the case of tropical malaria in particular, the prognosis depends on whether the patient is treated early and correctly.

Where does malaria occur?

Malaria occurs in tropical and many subtropical regions around the world, with the exception of Australia. The various malaria areas differ in part in the type of malaria pathogen that is common there. In addition, the number of new cases each year (incidence) varies in the individual malaria areas. The higher this incidence is in a region, the more likely it is that not only the local population but also travelers will become infected with malaria.

With regard to the risk of infection for malaria, the World Health Organization distinguishes between the following areas:

  • Areas without risk of malaria: e.g. Europe, North America, Australia, Sri Lanka
  • Areas with low (limited) malaria risk: e.g. certain areas in Mexico, Costa Rica and Thailand, Cape Verde
  • Areas with high risk of malaria: e.g. almost the entire tropical-subtropical region of Africa south of the Sahara, large parts of India and Indonesia

In recent years, people in southern Europe (such as Spain, Greece) have also contracted malaria with the mostly harmless variant malaria tertiana.

Below you will find information on the risk of malaria in selected regions worldwide:

Malaria areas in Africa

About 90 percent of all malaria cases are recorded in Africa. So for example exists in whole Kenya Below 2,500 meters above sea level, there is a high risk of infection all year round, also in the tourist areas on the coast and in the cities. In the vast majority of cases in Kenya, the most dangerous form of malaria - malaria tropica (caused by Plasmodium falciparum).

Other African countries with a high risk of malaria all year round are for example Malawi, Madagascar, Ghana, Gambia, Liberia, Republic of the Congo, Nigeria, Sierra Leone and the Comoros. In Tanzania the risk of infection for malaria is high year-round in regions below 1,800 meters (also in cities). The risk of malaria is low between 1,800 and 2,500 meters and on the island of Zanzibar.

South Africa also shows regional differences in terms of the risk of malaria infection: in the Northern Province, in the southeast and east of Mpumalanga Province (including the Kruger National Park and neighboring national parks) and in the north and northeast of Limpopo Province, it exists from September to May high risk of malaria and medium to low risk from June to August. In the rest of the north, the risk of malaria infection is low. The rest of South Africa and the cities are considered malaria free.

Namibia harbors a high risk of malaria all year round in the north and northeast (such as the Caprivi Strip, Kavango West, Kavango North, Ohangwena). In certain northeastern areas (Otjozondjupa District), the risk of malaria is high from September to May and low the rest of the year. In the rest of the country, the risk of infection is largely low. Some areas (such as the capital Windhoek, the coast and the Namib Desert) are even considered malaria-free. Almost all cases of illness in Namibia can be attributed to the dangerous malaria tropica - as in South Africa.

In Botswana There is a high risk of malaria all year round in the areas north of the city of Maun (including the Okavango Delta, Chobe National Park, etc.). From September to May this also applies to the rest of the northern half of the country below Maun. The rest of the year the risk of malaria infection is low in this area. There is a minimal risk of malaria almost everywhere in the southern half of the country, except in Gabarone - the capital is considered malaria-free.

In Egypt a very low risk of malaria is to be expected in the area around the city of El Faiyûm between June and October.

Malaria areas in Asia

In Asia There is a very different risk of infection for malaria depending on the region. Thailand For example, there is little malaria risk all year round in the border areas of the northern half (including the tourist areas in the Golden Triangle) and in the southern half of the country (including the coasts). The same goes for Khao Sok National Park and most of the islands (such as Ko Chang, Ko Mak). In contrast, the central areas in the northern half of Thailand, Bangkok, Chanthaburi, Chiang Mai, Chiang Rai, Pattaya, Phuket, Samet, Ko Samui and the islands of the Krabi Province are considered malaria-free. Incidentally, almost a quarter of the malaria pathogens in Thailand are responsible Plasmodium falciparum from, the causative agent of the dangerous malaria tropica.

In Indonesia the big cities are malaria free. In other regions, the risk of contracting malaria is minimal (e.g. Sumatra, Bali, Java), low (e.g. islands of the Moluccas) or high (Irian Jaya / West Papua and the island of Sumba). Plasmodium falciparum (Trigger of malaria tropica) is the most common malaria pathogen here.

In India there are clear regional and seasonal differences in terms of the risk of malaria infection: in the east and north-east of the country, at altitudes below 2,000 meters, there is a risk of contracting malaria all year round. This risk is highest between May and November. In the rest of the country, the risk of malaria is minimal all year round below 2,000 meters above sea level. This also applies to the cities of Delhi, Rajasthan and Mumbai as well as the Andaman and Nicobar Islands. Altitudes over 2,000 meters from Himachal Pradesh, Jammu and Kashmir, Sikkim, Arunchal Pradesh and the Laccadives are malaria free.

In Malaysia the malaria risk in the interior of the country is low to minimal all year round. The capital Kuala Lumpur and the state of Penang are considered malaria-free.

In China There is a low risk of malaria all year round in rural areas below 1,500 meters above sea level in the province of Yunnan on the border with Myanmar. The same is true for some areas in Eastern Tibet. The rest of the country, including Hong Kong, is malaria free.

Vietnam poses a high risk of malaria in the border regions with Cambodia and a minimal risk in the rest of the country. The big city centers are not malaria areas.

Sri Lanka is also not considered a malaria area.

Malaria areas in the Caribbean, Central and South America

In Haiti there is a high risk of malaria all year round in the provinces of GrandÁnse and Nippes. In the rest of the country (including the cities) the risk of infection is low. When someone develops malaria in Haiti, it is almost always the trigger Plasmodium falciparum (The causative agent of tropica malaria). In the Dominican Republic This pathogen is responsible for all malaria diseases. However, there is only a risk of infection in certain areas (e.g. in the western provinces) and this is also low all year round.

On Jamaica There are currently no documented cases of malaria infections acquired here. The vector - the Anopheles mosquito - is common on the island. That's why experts advise mosquito repellent to be on the safe side.

In Mexico regionally there is a minimal to low risk of becoming infected with malaria. Affected are among others the south of the province of Chihuahua, the province of Chiapas as well as some areas in the provinces of Cancun, Durango, Sonora and Tabasco. In all of these areas it is considered a malaria pathogen only Plasmodium vivax common, one of the two causes of tertian malaria.

In Guatemala In the Escuintla administrative district on the Pacific coast, the risk of malaria infection is high all year round. In most of the rest of the country, there is a medium to minimal risk year round. The cities of Guatemala City (capital) and Antigua as well as Lake Atitlán are considered malaria-free.

In El Salvador and Costa Rica there is a low risk of malaria in some areas.

In South America show, for example Amazon basin a high risk of malaria. Share in this region among others Brazil, Venezuela, Bolivia, Ecuador, Colombia, Peru, French Guiana and Guiana. In other regions and countries in South America, the risk of infection is moderate to minimal. Some areas are also considered malaria free. In Peru, for example, Machu Picchu, Lake Titicaca and the capital Lima. In Brazil, for example, there is no risk of infection in the cities of Brasilia and Rio de Janeiro or at the Iguacu Waterfalls, and all of Argentina is free from malaria.

Malaria areas in the Middle East

In the Turkey the tourist areas are considered malaria-free. In southeastern Anatolia and in the Amikova and Cukurova plains there is a low risk of contracting malaria from May to October. However, only the malaria pathogen is widespread Plasmodium vivax - The cause of the less dangerous malaria tertiana.

in the Iraq there is a minimal risk of malaria between May and November in the northeast below 1,500 meters above sea level and in the south of the country. in the Iran some regions in the south and south-east of the country show a minimal risk of infection between March and November.

in the Yemen Malaria can be infected year-round and across the country, with greater risk from north to south.

Malaria and Co .: souvenirs from vacation
Back sick from vacation? Swiss researchers have now investigated what the most common annoying souvenirs are and how you can protect yourself. By Larissa Melville

Malaria prophylaxis

There is no vaccine against malaria. But those who adhere to various protective measures can prevent infection. Above all, this includes measures that reduce the risk of mosquito bites in malaria areas. So, for example, you should be in such areas bright clothes wear that covers the body as comprehensively as possible (long sleeves, long pants, socks). If necessary, you can wear one of your clothes beforehand Mosquito repellent impregnate. One is also useful mosquito-proof sleeping place, for example with a fly screen in front of the window and a mosquito net over the bed.

In addition, in some cases there is also a Malaria prevention with medication (Chemoprophylaxis) possible and useful.

It is best to seek advice from a doctor (ideally a tropical or travel medicine specialist) in good time before starting your journey. He can recommend the right malaria prophylaxis for you - depending on the risk of malaria in the country you are traveling to, the duration of the trip and the type of trip (e.g. backpacking tour or hotel trip).

Read more about the different ways to prevent malaria in the text Malaria prophylaxis.

Malaria: causes and risk factors

Malaria is caused by small, unicellular parasites called plasmodia. There are around 200 different species. Five of them can cause illness in humans:

  • Plasmodium falciparum: Triggers tropica malaria, the most dangerous form of malaria. This type is found in most malaria areas. It is responsible for almost all malaria cases in Africa, half of all malaria cases in Southeast Asia, around 70 percent of all malaria cases in the eastern Mediterranean and 65 percent of all malaria cases in the western Pacific region.
  • Plasmodium vivax and Plasmodium oval: Triggers tertiana malaria. P. vivax is the predominant pathogen on the American continent and is responsible for three quarters of all malaria cases there. P. ovale on the other hand occurs mainly in West Africa.
  • Plasmodium malariae: Quartana malaria triggers. Occurs in tropical regions around the world.
  • Plasmodium knowlesi: Widespread only in Southeast Asia. Triggers malaria mainly in monkeys (macaques) and only occasionally in humans.

Malaria: ways of transmission

The malaria pathogens are most commonly caused by the Bite from a blood-sucking female mosquito of the genus anopheles transmitted that is infected with plasmodia. The Anopheles mosquito (colloquially: malaria mosquito) is exclusively crepuscular and nocturnal. This means: Malaria infection usually occurs through a bite in the evening or at night.

There is a simple formula for the risk of infection in a certain region: the more Anopheles mosquitoes in an area, the more people they infect. If these patients are not treated and are bitten again by an unaffected mosquito, it can absorb the pathogen and pass it on to another person with the next blood meal.

It is very rare for people outside of malaria areas to develop the tropical disease. For example, there is the so-called Airport malaria: Infected anopheles mosquitoes imported by plane can sting people on the plane, at the airport or in the immediate vicinity and infect them with the malaria pathogen.

A transmission of the malaria pathogen is also via a Blood transfusion or over infected needles (hypodermic needles, infusion needles) possible. Due to the strict safety regulations, this only happens extremely rarely in Germany. With blood transfusions in malaria areas, however, the risk of infection may be greater.

A transfer is also in rare cases from a pregnant woman to the unborn child possible: The pathogen can get from the mother's blood into the child's blood via the placenta.

Sickle cell anemia offers a certain protection against malaria. Malaria is much less common and much less pronounced in people with this hereditary disease. In sickle cell anemia, the shape of the red blood cells is changed in such a way that the malaria pathogen cannot attack them or can only attack them to a limited extent in order to reproduce in them. That is probably the reason why sickle cell anemia is particularly common in many malaria areas.

Life cycle of the malaria pathogen

The malaria pathogens are called so-called Sporozoites transmitted from mosquitoes to humans. Sporozoites are the infectious development stage of the pathogen. The parasites reach the liver via the bloodstream and penetrate liver cells there. Inside the cell, they transform into the next stage of development: Schizontswhich fill almost the entire liver cell. Thousands of ripe ones arise within them Merozoites. Their number depends on the type of malaria pathogen - at Plasmodium falciparum (Causative agent of the dangerous malaria tropica) it is highest.

Finally the schizont bursts open and releases the merozoites into the blood. They affect red blood cells (erythrocytes). As soon as a merozoite has penetrated, it grows into another huge schizont that fills practically the entire erythrocyte. Many new merozoites form inside the schizont. As soon as the schizont (and the surrounding red blood cells) burst, the merozoites are released and can in turn attack red blood cells.

In malaria tertiana, M. quartana and Knowlesi malaria, the infected erythrocytes burst open synchronously to release the merozoites. The consequences are rhythmic attacks of fever. In malaria tropica, the bursting of the erythrocytes does not occur synchronously, so irregular bouts of fever result.

At Plasmodium vivax and P. ovale (Causative agent of malaria tertiana) only some of the merozoites in the red blood cells develop into schizonts. The rest goes into a resting phase and remains in the form of so-called Hypnozoites Months to years in the red blood cells. At some point these forms of rest can become active again and transform themselves into schizonts (and further into merozoites). Therefore, tertiana malaria can relapse years after infection.

The following applies to all malaria pathogens: some merozoites do not turn into schizonts in the red blood cells, but into long-lived ones female and male sex cells (gametocytes). If the malaria patient is stung by an anopheles mosquito again, it ingests such gametocytes with the blood meal. In the mosquito stomach, female and male gametocytes fuse into one fertilized egg cell (oocyst). Numerous go out of it Sporozoites emerged. They are passed back to a person during the mosquito's next blood meal - the circle is complete.

Is Malaria Contagious?

The malaria pathogen cannot be transmitted directly from person to person - except through blood contact such as between an infected pregnant woman and her unborn child or through contaminated blood transfusions. Otherwise, there is no danger to other people from the sick.

Insect bites - which really helps

  • Toxic legacy

    Summer, sun, mosquito season: when the little bloodsuckers sting, they leave a little poison behind. The affected area of ​​skin itches like hell, swells and hurts. This also applies to stings and bites from other insects. This is how you can alleviate the agonizing discomfort.
  • Cold and acid

    The first measure: cooling! With frozen ice cubes or cold water that flows from every tap. Then it's best to grab a lemon or onion from the fruit and vegetable basket, cut it open and place it on the puncture site. The ingredients soothe itching, reduce swelling and inhibit possible bacterial inflammation. Vinegar is believed to have a similar effect.
  • Beneficial plant

    With a bit of luck you will also find the right antidote for insect bites in the grass next to you - ribwort. It is best to pluck a few leaves from the green plant with white flowers and rub them between your fingers. Or you can chew the leaves in your mouth. Put the pulp on the puncture site.
  • Gel and ointment

    Not every healing plant can simply be picked along the way. But you are sure to find what you are looking for in the pharmacy or drugstore: arnica ointment or aloe vera gel have anti-inflammatory and germ-inhibiting effects. Aloe vera gel also has a cooling effect.
  • Natural oils

    Nature has even more in store for you: Various oils can cool the reddened area, relieve itching and prevent inflammation. Tea tree oil, lavender oil, and clove oil are some examples of natural oils that help against insecticide. Put a few tropics on a cotton ball and use them to dab the bite and sting of the tormentors.
  • Healing heat

    Thermo stitch healer - have you heard of it? It's a small plastic pen with a gold plate on top. It transfers heat and is supposed to neutralize the poison. If you have such a pen, you should press it down on the puncture site for a few seconds as quickly as possible. Don't worry: you won't get any scars because the pen only generates a temperature of around 50 degrees Celsius.
  • Medical help

    If the sting continues to swell, if you feel sick, or if you develop breathing difficulties, you must see a doctor immediately! It could be a severe allergic reaction. The doctor can prescribe antiallergic medication to prevent worse from happening. You should also seek medical treatment if the sting becomes infected.
  • By Dr Varinka Voigt

Malaria: incubation period

Malaria does not break out immediately after becoming infected with the pathogen. Instead, some time elapses between infection and the onset of symptoms. The length of this incubation period depends on the type of pathogen. In general, the following incubation times apply:

  • Plasmodium falciparum (Triggers tropica malaria): 7 to 15 days
  • Plasmodium vivax and Plasmodium ovale (Trigger of M. tertiana): 12 to 18 days
  • Plasmodium malariae (Trigger of M. quartana): 18 to 40 days
  • Plasmodium knowlesi (Trigger of Knowlesi malaria): 10 to 12 days

Under certain circumstances, the incubation period can be much longer in some cases: Both Plasmodium vivax as well as P. ovale can, as mentioned above, form resting forms (so-called hypnozoites) in the liver. Even years later, these can leave the liver again, multiply in the red blood cells and cause symptoms. At P. vivax is this up to two years possible after infection, at P. ovaleup to five years after that.

Plasmodium malariae does not develop forms of rest (hypnozoites). The number of parasites in the blood can be so low that symptoms occur up to 40 years can perish.

Malaria: symptoms

In general, symptoms such as malaria appear fever, Headache and pain in the limbs as well as a general feeling of illness first on. Also diarrhea, nausea, Vomit and dizziness are possible. Some patients mistakenly attribute the symptoms to a simple flu-like infection or the flu.

In detail, there are some differences in the symptoms of the various forms of malaria:

Symptoms of tropical malaria

Malaria tropica is the most dangerous form of malaria. Symptoms appear here more violently than with other forms and weaken the organism considerably. The reason is that the pathogen (Plasmodium falciparum) affects both young and older red blood cells (unlimited parasitemia) and thus destroys a particularly large number of erythrocytes in the further course.

Symptoms of malaria tropica are mostly Headache and pain in the limbs, Exhaustion and irregular flare-ups or even continuous fever. Also Vomit as Diarrhea with fever can occur. Some patients also develop respiratory problems like one dry cough. In addition, the massive breakdown of red blood cells triggers one Anemia (Anemia).

Consequences & complications

In the course of the disease, the Enlarge spleen (Splenomegaly), because it has to do hard work with malaria: it has to break down the many red blood cells that are destroyed by the malaria pathogen. If the spleen exceeds a critical size, the surrounding spleen capsule can tear (rupture of the spleen, rupture of the spleen). This leads to heavy bleeding ("tropical splenomegaly syndrome").

Also one Enlargement of the liver (Hepatomegaly) as a result of malaria infection is possible. It can be accompanied by jaundice (jaundice).

The simultaneous enlargement of the liver and spleen is called hepatosplenomegaly.

In about one percent of the participants, the pathogens penetrate the central nervous system (cerebral malaria). This can, for example, trigger paralysis, seizures, impaired consciousness and even coma. Ultimately, those affected can die.

The malaria pathogens can also affect the lungs (pulmonary malaria). Frequent complications are pulmonary edema (water retention in the lungs). The heart can also be affected (cardiac malaria), which can lead to heart muscle damage, for example.

Other possible complications of tropical malaria are one impaired kidney function (acute kidney failure), Circulatory collapse, Anemia as a result of the increased breakdown of red blood cells (hemolytic anemia) and a "disseminated intravascular coagulopathy"(DIC): This activates blood clotting inside intact blood vessels, which means that massive amounts of blood platelets are consumed - a lack of blood platelets (thrombocytopenia) develops with an increased tendency to bleed.

Especially with pregnant women and children there is also the risk of malaria tropica with Hypoglycaemia (Hypoglycaemia). Possible signs include weakness, dizziness, cravings and seizures.

Symptoms of tertiary malaria

In this form of the disease, the malaria symptoms are usually much weaker. It starts with sudden fever and other unspecific complaints like a headache. In the further course, arise rhythmic attacks of fever a: They usually occur every second day on (i.e. every 48 hours). Hence the addition of "tertiana" to the name: day 1 with fever, day 2 without fever, day 3 with fever again. The fever attacks typically show the following course:

The patients get chills in the late afternoon and then very quickly a fever of around 40 degrees Celsius. After about three to four hours, the temperature quickly drops back to normal, accompanied by heavy sweating.

Complications and deaths are rare in tertian malaria. But relapses can still occur years later.

Symptoms of quartana malaria

Occur in this rare form of malaria Fever flare-ups every third day (i.e. every 72 hours). The temperature can rise up to 40 degrees and be accompanied by severe chills. After about three hours, the fever subsides with strong sweats.

Possible complications are kidney damage and ruptured spleen. In addition, relapses can occur up to 40 years after infection.

Symptoms at Plasmodium knowlesi-Malaria

This form of malaria, which is restricted to Southeast Asia, was previously only known to occur in certain monkeys (macaques). Transmission of Anopheles mosquitoes, however, it can also occur in humans in rare cases.

Sometimes this variant of malaria is confused with malaria tropica or malaria quartana. However, it works P. knowlesi-Malaria typically with daily bouts of fever hand in hand. Otherwise, as with the other forms of malaria, you may experience chills, headaches and body aches. The disease can be severe, but is rarely fatal.

You can also become infected with different Plasmodium species at the same time, so that the symptoms can be mixed.

Malaria: examinations and diagnosis

If you have stayed in a malaria risk area in the weeks before the symptoms appeared (or are still there), you should consult a doctor (family doctor, tropical medicine, etc.) at the slightest sign of the onset of illness (especially if you have a fever) .). Especially with the dangerous malaria tropica, a quick start of therapy can be life-saving!

Even months after a trip to a malaria risk area, any unexplained febrile illness should be examined accordingly. Because sometimes malaria breaks out only very slowly.

Doctor-patient conversation

The doctor will first talk to you about your Collect medical history (Anamnesis). Possible questions are:

  • Which complaints do you have exactly?
  • When did the symptoms first appear?
  • When was the last time you were abroad?
  • Where have you been and how long have you been there?
  • Have you been bitten by mosquitoes in your travel destination?
  • Did you take medicated malaria prophylaxis in the travel destination?

Blood tests

If there is the slightest suspicion of malaria (intermittent fever), your blood will be examined microscopically for malaria pathogens. For this purpose, a "thin blood smear" and / or "thick blood smear" ("thick drop") is made:

At the thin blood smear a drop of blood is spread thinly on a slide (small glass plate), air-dried, fixed, stained and viewed under the microscope. The staining is used to make any plasmodia present in the red blood cells visible. The advantage of this method is that the type of plasmodia can be easily determined. However, if only a few red blood cells are infected with plasmodia, the infection may be overlooked.

The more accurate detection method is therefore the thick blood smear, because here the plasmodia are enriched six to ten times: To do this, a thick drop of blood is placed on the slide, air-dried and stained without fixation. Due to the lack of fixation, the stain destroys the red blood cells, releasing the stained plasmodia.

The disadvantage of the thick blood smear is that it is not as easy to determine the type of plasmodia as it is with the thin smear. At most, the pathogens causing the life-threatening malaria tropica (Plasmodium falciparum) from the other malaria pathogens (such as P. vivax) differ. The thin blood smear is necessary for precise identification.

If no plasmodia can be detected in the blood test, malaria can still be present. In the early stages, the number of parasites in the blood can still be too low to be detected (even for the thick drop). So if the suspicion of malaria persists and symptoms persist, the blood should be tested repeatedly for plasmodia every 12 to 24 hours.

If the investigation is malaria infection by Plasmodium falciparum or P. knowlesi results, the amount of parasites in the blood is also determined. These Parasite density in the blood (Parasitemia) influences the therapy planning.

If the direct detection of the pathogen in the blood confirms the suspicion of malaria, help other blood valuesto estimate the severity of the disease. These include, for example, red and white blood cells, platelets (thrombocytes), C-reactive protein (CRP), blood sugar, creatinine, transaminases and bilirubin.