Malaria
Malaria is a disease caused by unicellular parasites (plasmodia). It is still the most important tropical disease and is found in more than 100 countries worldwide. Malaria affects children in Africa in particular.
History
In 2015, according to WHO, there were 214 million new malaria cases worldwide. The most common diseases were in Africa, in areas of South-East Asia and in the Eastern Mediterranean.
In the fight against malaria, however, 50-75% of malaria cases in 18 affected countries have been reduced since 2000. Between 2000 and 2015, the number of malaria new diseases worldwide fell by 37%, the mortality rate fell by as much as 60%.
This success is attributed to better surveillance and better access to prevention, diagnosis, and treatment of malaria in recent years.
What is malaria?
Malaria is a tropical disease caused by so-called plasmodia in the blood. The infection with the pathogens (plasmodia) is transmitted by mosquitoes (mosquitoes of the genus Anopheles) and their occurrence is thus coupled to the occurrence of these insects. This explains a weather-dependent accumulation in certain regions.
The most important measure in the fight against malaria is the decimation of the carriers and the treatment of the patients, who are considered pathogen reservoirs. For this purpose, wetlands are drained and insecticides are used, but the most effective method of control is "ITN": "insecticide-treated nets" that break the chain of infection by blocking nocturnal mosquitoes directly in the household.
Malaria has now been eradicated in North America, Europe, and Russia. In many countries in Asia, as well as in South and Central America, the number of new infections with malaria has been reduced significantly. In the tropics, eradication has not been achieved despite great efforts.
An increasing problem is the development of resistance of Plasmodium against numerous standard preparations, which were used for the therapy and at the same time, with the exception of Artemisinin in the last years no new therapeutics market-ready.
This circumstance makes it difficult to have a treatment that is certainly effective and low in side effects.
In Austria, between 50 and 100 malaria cases occur each year. These are imported cases of illness - due to long-distance travel in malarial areas, usually due to refusal of prophylaxis or very rarely due to the failure of the drug.
How do you get malaria?
The pathogens (plasmodia) are usually transmitted to humans through the bite of the female Anopheles mosquito. Very rarely, malaria can also be transmitted to the child through blood transfusions, the use of used syringes, or in the context of a birth from an infected mother.
How is the onset of the disease?
The plasmodia - unicellular parasites - enter the bloodstream from the glandular glands of the mosquitoes, they undergo typical maturation and multiplication cycles in the human body.
On the bloodstream, they first reach the liver and penetrate into liver cells, where they multiply. There are up to 1000 daughter cells. As a result, the liver cells swell up and eventually burst, causing the pathogens to enter the bloodstream. Only at the stage of infection of the red blood cells (erythrocytes), the first tangible clinical symptoms occur.
In the benign (benign) forms are affected to about two percent of erythrocytes, in the malignant (malignant) form, the malaria tropica, up to 60 percent of the erythrocytes may be affected. In the erythrocytes, there is again an increase of the pathogens (six to 32 daughter cells), which burst erythrocytes and the released pathogens attack again new erythrocytes. It comes to malaria.
What different types of malaria are there?
So far, four different types of malaria pathogens (plasmodia) have been known to cause different clinical pictures, namely
Pathogen of malaria form
Plasmodium vivax →Malaria tertianaPlasmodium oval → malaria tertiana
Plasmodium malariae →malaria quartana
Plasmodium falciparum→ Malaria tropica
Recent research now shows that another strain from Southeast Asia, naturally occurring in macaques (primates), is transmissible to humans - the pathogen Plasmodium knowlesi. This pathogen may cause a clinical picture similar to malaria tertiana, but the severe disease is also possible.
All plasmodium pathogens differ significantly in terms of their geographical distribution and disease progression. Plasmodium falciparum, however, is the most significant and threatening pathogen.
Plasmodium falciparum is the causative agent of malaria tropica. The malaria tropica is usually more severe than the other forms, complications and deaths occur almost exclusively in this form. In a complicated course, it is therefore also referred to as Malaria malignant (malignant malaria).
Fevers
The other types of malaria - malaria tertiana and malaria quartan - are caused by Plasmodium vivax, ovale or malariae, they differ by the intervals between the fever episodes. This difference is due to a different duration of the (synchronized) multiplication cycle of the pathogens in the red blood cells.
The reproductive cycle is 48 hours for Plasmodium falciparum and vivax, 50 hours for Plasmodium ovale and 72 hours for Plasmodium malariae.
Consequently, in case of infection with Plasmodium malariae between the fevers each fever-free days, that is, the fever episodes occur every first and fourth day, hence the name malaria quartana.
Fever curve of malaria quartana
In malaria tertiana - by Plasmodium vivax and Plasmodium ovale - the fever episodes occur every third day, hence the name Malaria tertiana.
Fever curve of malaria tertiana
A special form is the malaria quotidian with attacks of fever at intervals of 24 hours, ie daily. Cause are two plasmodium generations of P. vivax or ovale, whose development cycle is postponed by 24 hours.
Fever episodes in malaria tropica
In the malaria tropica (by Plasmodium falciparum), the fever bouts are often irregular, which is due to the superposition of different cycles and Mehrfa.
Infections is conditional.
Who is particularly affected by malaria?
Malaria is endemic in most tropical and some subtropical regions of the world, which means that a large proportion of the population is infected with plasmodia and the likelihood of transmission is very high.
In sub-Saharan Africa, New Guinea, and Haiti, Plasmodium falciparum predominates
in Central America and India Plasmodium vivax, it is noted that in India the incidence of Plasmodium falciparum is increasing. In South America, Oceania and East Asia, Plasmodium falciparum and vivax are about equally common.
Plasmodium malaria and ovals are found in most areas of Africa, but they are extremely rare outside of Africa.
The distribution area for Plasmodium knowlesi is limited to Southeast Asia, especially in regions such as Borneo or the Malai Peninsula.
In addition to the permanent inhabitants of the tropics, especially travelers are at risk. In very rare cases, malaria parasites are also transmitted outside their distribution areas. Either by infected mosquitoes imported via air traffic (so-called "airport malaria") or by locally present mosquitoes that have become infected with a plasmodium-infested human.
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