In the case of malaria, causes of the disease involve infection with parasites belonging to the genus Plasmodium. While there are more than 100 species of Plasmodium, only 4 of them can infect humans with malaria. The disease is transmitted to humans most often from a bite from an Anopheles mosquito. Other ways that malaria may be transmitted include through blood transfusions, organ transplants, and from mother to child in "congenital malaria."
The cause of malaria is an infection with a malaria parasite. There are several types of malaria parasites, each belonging to the genus Plasmodium.
Malaria parasites (Plasmodium) are tiny organisms that can only be seen under a microscope. There are more than 100 species of Plasmodium, which can infect many animal species, including:
- Various mammals.
Only four species of Plasmodium infect humans in nature. These four types of Plasmodium include:
- Plasmodium falciparum
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae.
While an infection with a Plasmodium parasite actually causes malaria, there is another important species in malaria transmission. This is the Anopheles mosquito. Anopheles mosquitoes are important because they actually transmit Plasmodium to humans through a bite. No other types of mosquitoes are known to transmit malaria.
Factors that determine the occurrence of malaria are those that influence the three components of the malaria life cycle:
- Anopheles mosquitoes (the "malaria mosquito") must be present and in contact with humans. Within the Anopheles mosquitoes, the Plasmodium parasites can complete the "invertebrate host" half of their life cycle.
- Humans must be present and in contact with Anopheles mosquitoes. Within the human host, Plasmodium parasites can complete the "vertebrate host" half of their life cycle.
- Malaria parasites must be present.
Less commonly, malaria transmission may occur through contact with infected blood, such as:
- A blood transfusion
- An organ transplant
- From mother to child in "congenital malaria."
In these cases, the cause of malaria is still a Plasmodium parasite; but how the parasite spreads differs.
Malaria causes a wide variety of symptoms, ranging from absent or very mild symptoms to severe disease, and even death. Malaria disease can be categorized as uncomplicated or severe (complicated). In general, malaria is a curable disease if diagnosed and treated promptly and correctly.