Malaria, an illness perpetuated by parasites infiltrating red blood cells, is predominantly transmitted to humans through the bite of the female Anopheles mosquito, a carrier of the Plasmodium parasite. Plasmodium falciparum, among the many various parasite species affecting humans, is notably linked to elevated fatality rates. The predominant symptom of malaria is fever, accompanied by additional symptomatology including headache, cough, nausea, vomiting, abdominal pain, diarrhea, and muscle or joint pain.
The disease mechanism involves the mosquito biting a human, introducing parasites from its saliva into the person’s liver. The parasites undergo initial growth and multiplication in liver cells, progressing to infiltrate red blood cells. Within the bloodstream, successive generations of parasites thrive within red cells, causing their destruction and releasing daughter parasites (“merozoites”) that perpetuate the cycle by invading other red cells.
Malaria is diagnosed by identifying Plasmodium parasites in a blood sample. Swift identification and treatment of uncomplicated malaria, primarily caused by Plasmodium falciparum, are crucial to prevent progression to severe malaria. Initial treatment involves the immediate use of artemisinin-based combination therapies (ACT). In the absence of ACTs, alternative options such as atovaquone-proguanil or quinine plus clindamycin can be used.
Severe malaria, often characterized by a high blood level of Plasmodium parasites, can lead to decreased consciousness, seizures, respiratory difficulties, severe anemia, and multiorgan failure. Vulnerable populations include young children, pregnant women, older individuals, and the immunosuppressed . Untreated severe malaria is almost always fatal, but timely and effective treatment reduces the malaria-related death rate in the US to less than 2%. Intravenous artesunate is recommended for treating severe cases, with close monitoring in the ICU.
Malaria prevention involves controlling mosquito populations in endemic areas, utilizing measures like mosquito nets, insecticides, and eliminating standing water as breeding grounds. For travelers, precautions such as DEET-containing insect repellents, insecticide-treated clothing, and avoiding outdoor activities between dusk and dawn mitigate the risk of travel-associated malaria. Chemoprophylaxis is advised for individuals traveling to malaria-endemic regions without prior exposure or after losing immunity. The choice of prophylactic drugs, frequency of administration, and duration depend on the specific drug used. Vaccination with the 4-dose RTS,S/AS01 malaria vaccine has seen a reduction in malaria deaths in children by 30%.
In 2019, approximately 229 million malaria cases occurred globally, resulting in almost a half a million deaths, with the highest incidence and mortality rates in sub-Saharan Africa. In the US, around 2,000 malaria cases are diagnosed annually, primarily among travelers who visited malaria-endemic countries.
