Malaria is an infectious disease caused by protist parasites of the genus Plasmodium. It is carried by mosquitoes and transmitted through their bite. The effects of malaria on affected humans differ according to the Plasmodium species involved. Plasmodium falciparum causes the most severe effects of malaria and has the highest rate of mortality, while Plasmodium ovale, Plasmodium malariae, and Plasmodium vivax cause milder forms of the disease.
The most well-known and typical effects of malaria are chills and fever, which tend to repeat in cycles. These cycles occur about every other day in P. vivax and P. ovale infections, but every three days in P. malariae infections. The cycles caused by P. falciparum are a bit more frequent than those of the other parasites, and fever may be continuous. Other possible effects of malaria include vomiting, joint pain, convulsions, and damage to the retina. Cerebral malaria, in which the infection reaches the brain, may cause brain damage and cognitive impairments, especially in children, who are most susceptible to cerebral infection. Cerebral malaria is also associated with whitening of the retina.
P. falciparum is both the most prevalent form of malaria, and the most deadly. It is responsible for more child deaths around the world than any other infectious disease. The effects of P. falciparum-related malaria can include enlarged spleen or liver, restricted blood supply to the brain, hemoglobinuria or the presence of hemoglobin in the urine, severe headache, and hypoglycemia or abnormally low blood sugar. If untreated, it can cause kidney failure, coma, and death. It may also cause developmental disorders in children. P. vivax and P. ovale can both cause chronic malaria, in which the patient may relapse months or years after the original infection.
Malaria prevention efforts include mosquito population control, wearing protective clothing or mosquito repellent, and using mosquito nets. Antimalarial drugs such as chloroquine, primaquine, and quinacrine may be used to treat infection or as a prophylaxis to prevent infection. A vaccine for malaria is currently under development. Education focused on avoiding mosquito bites and controlling mosquito populations, as well as on recognizing early signs of malaria infection, is also essential in the fight against the disease.