Malaria is an infectious disease caused typically caused by the parasites Plasmodium falciparum or Plasmodium vivax. These parasites are usually transmitted by the Anopheles mosquito but may rarely be spread through the blood in situations such as sharing contaminated needles in injection drug users. The condition is typically found in most tropical areas around the world. P. falciparum predominates in regions such as sub-Saharan Africa, New Guinea, and Haiti. P. vivax frequently affects individuals living in the Americas. Patients with malaria often develop nonspecific flu-like symptoms such as chills, fatigue, sweating, headache, cough, abdominal pain, nausea/vomiting, and diarrhea.
Severe forms of the disease may result in anemia, hypoglycemia (low glucose levels), acidosis, renal impairment, and liver abnormalities. Malaria is responsible for more than 600,000 deaths annually.
Malaria is usually caused by the parasites Plasmodium falciparum or Plasmodium vivax. These parasites are most often transmitted by the bite of a female Anopheles mosquito. These mosquitoes are most active between sunset and sunrise. Other forms of transmission are exceedingly uncommon and may include blood transfusion, sharing needs in drug users, and organ transplantation.
Once the parasite enters the bloodstream, it invades liver cells and rapidly divides. Eventually, liver cells (hepatocytes) rupture, and the numerous parasites are released into the circulation. This leads to parasite invasion of red blood cells, breaking them down, resulting in anemia (hemolytic anemia).
Malaria affects over 3 billion people worldwide. Transmission occurs in approximately 95 countries and leads to more than 600,000 deaths annually. Each year, there are about 1500 cases of imported malaria in the United States. Infection typically requires referral to an infectious disease specialist.
Most malaria cases are caused by P. falciparum; however, P. vivax also contributes to a significant number of infections. P. falciparum is typically found in sub-Saharan Africa, New Guinea, Haiti, and the Dominican Republic. In contrast, P. vivax is more frequently seen in the Americas and western Pacific. Both species of Plasmodium are responsible for infection in areas such as the Indian subcontinent and eastern Asia.
Malaria is generally suspected in individuals with fever who have recently been exposed to an area endemic with malaria infection. Patients often develop flu-like symptoms, including:
- Malaise & fatigue
- Sweating – diaphoresis
- Abdominal pain
- Nausea & vomiting
- Body aches – myalgias & arthralgias
Severe forms of malaria can be complicated by low glucose levels (hypoglycemia), metabolic acidosis, kidney failure, fluid in the lungs (pulmonary edema), anemia, and liver abnormalities. Children often develop seizures and coma.
The diagnosis of malaria is suggested based on travel history, symptoms, and physical examination but typically confirmed with laboratory studies. Your doctor may visualize the parasites on stained blood samples using a light microscope. They may also order rapid diagnostic tests that detect parasite antigen or antibodies. There are also molecular techniques that analyze parasite DNA.
Commonly ordered routine blood tests include a CMP (comprehensive metabolic panel), CBC (complete blood cell count), urine analysis, and coagulation studies (PT/INR, PTT). If you have difficulty breathing or fluid in the lungs, your doctor will typically order a chest x-ray.
Malaria can generally be prevented using mosquito repellents to avoid being bitten by mosquitoes carrying Plasmodia. This typically involves applying synthetic chemicals such as DEET (N, N-diethyl-m-toluamide) to the skin. Individuals may also benefit from avoiding outdoor exposure between sunset and sunrise, wearing clothes to cover exposed skin, staying in air-conditioned rooms, and using sleeping nets – none of these methods are full proof.
Individuals traveling to endemic regions may also benefit from prophylactic treatment with antimalarial drugs. These drugs are used for chemoprophylaxis as well as treatment of malaria depends on the dosing schedule.
Various medications are used to treat malaria – the drug of choice often depends on the type of Plasmodium infection and whether or not the parasite is resistant to chloroquine.
Chloroquine sensitive malaria is typically treated with:
- Aralen (chloroquine)
- Plaquenil (hydroxychloroquine)
Individuals with confirmed or suspected chloroquine-resistant malaria typically receive treatment with:
- Artemisinin combination therapy such as Coartem (artemether-lumefantrine) or Camoquin (artesunate-amodiaquine)
- Malarone (atovaquone-proguanil)
- Qualaquin (quinine) combined with Vibramycin (doxycycline) or clindamycin
- Lariam (mefloquine)
Your doctor will typically monitor daily blood smears to ensure the medication is working and has eradicated the parasites.
- Schwartz E, Parise M, Kozarsky P, Cetron M. Delayed onset of malaria–implications for chemoprophylaxis in travelers. N Engl J Med 2003; 349:1510. – https://www.nejm.org/doi/full/10.1056/NEJMoa021592
- Wilson ME, Weld LH, Boggild A, et al. Fever in returned travelers: results from the GeoSentinel Surveillance Network. Clin Infect Dis 2007; 44:1560. – https://www.ncbi.nlm.nih.gov/pubmed/17516399
- Centers for Disease Control and Prevention. Malaria: Disease. http://www.cdc.gov/malaria/about/disease.html (Accessed on May 5, 2017). – https://www.cdc.gov/parasites/malaria/index.html