Acquired Malaria FAQ for Clinicians

In children, symptoms are often non-specific and mimic other childhood illnesses, including gastroenteritis, meningitis, or pneumonia. Symptoms may include high fever with chills, headache, malaise, weakness, nausea, vomiting and diarrhea. In severe cases, neurological symptoms, such as dizziness, confusion, disorientation, and coma may occur, but this is less common with Plasmodium vivax, the species of malaria most commonly identified to be locally acquired. However, one case of P. falciparum was reported to be locally acquired in Maryland in August 2023.

Malaria symptoms can develop as early as 7 days after being bitten by an infectious mosquito and as late as several months or more after exposure. Different species of parasites that cause malaria in humans can cause longer or shorter incubation periods. Some parasite species have the ability to remain dormant in the liver for months or years. When this occurs, your patients may not experience any symptoms until a year or more.

Most malaria cases have occurred through the bite of an infective female Anopheles mosquito to a human. Rarely, malaria may be transmitted congenitally from mother to fetus or to the neonate at birth, through blood transfusions, organ transplantation, or through unsafe needle-sharing practices. Mosquito activity can increase as temperatures increase, and infected mosquitoes can multiply rapidly in areas that experience “monsoon season” and/or flash floods after heavy rainstorms. Mosquitos potentially carrying diseases such as malaria can reproduce rapidly in standing water, where small children and animals can be exposed. CDC – Malaria – About Malaria – Malaria Transmission in the United States 

Individuals without prior immunity to malaria, young children, pregnant women, and immunocompromised patients are at highest risk for severe disease. Malaria in pregnant women is associated with high risks of both maternal and perinatal morbidity and mortality. Malaria parasites sequester and replicate in the placenta. Pregnant women are three times more likely to develop severe disease than non-pregnant women who acquire malaria in the same geographic area. Malaria infection during pregnancy can lead to miscarriage, premature delivery, low birth weight, congenital infection, and/or perinatal death. 2024- 2027 Red Book American Academy of Pediatrics (aap.org) 

Blood smear microscopy remains the most important method for malaria diagnosis. This is a rapid test with results available in less than 24 hours. Microscopy of a blood smear can provide immediate information about the presence of parasites, allow quantification of the density of the infection, and allow determination of the species of the malaria parasite—all of which are necessary for providing the most appropriate treatment. If the initial blood smear is negative but index of suspicion of malaria remains high, repeating the blood smear once a day for the next 2 days may be helpful. Rapid diagnostic tests (RDTs) are immunochromatographic tests that most often use a dipstick or cassette format and provide results in 2–15 minutes. RDTs offer a useful alternative to microscopy in situations where reliable microscopic diagnosis is not immediately available. Although RDTs can detect malaria antigens within minutes, they have several limitations. RDTs cannot distinguish between all Plasmodium species that affect humans, and they might be less sensitive than expert microscopy or PCR for diagnosis. PCR tests also are available to detect malaria parasites. These tests are more sensitive than routine microscopy, but results are not usually available as quickly as microscopy results. Malaria | CDC Yellow Book 2024

Malaria can be fatal even when treated, which is why prevention is always preferable to treating infections after they occur. The primary method of malaria prevention is to avoid mosquito bites. Anopheles mosquitoes primarily feed at night with transmission occurring mostly between dusk and dawn. Prevention strategies when traveling to countries with endemic malaria include personal protective measures such as using insecticide-treated bed nets, wearing clothes that minimize exposed skin, and applying mosquito-repelling chemicals. Not all mosquito repellents are safe for all children. The American Academy of Pediatrics provides guidance for how caregivers can choose a safe and effective insect repellent for their child.

All travelers to malaria-endemic regions should be prescribed antimicrobial prophylaxis. Prophylaxis is not necessary for people in the US, even in areas where local transmission of malaria has been identified. All prevention regimens involve beginning the medication before departure, taking the medication while in the high-risk area, and continuing the medication for a defined period after travel has ended. These regimens should be used concurrently with personal protective measures. Clinicians can remind patients and their families to prevent mosquito bites and control mosquitoes at home to protect them from mosquito-borne illnesses. Mosquito Control at Home | Mosquitoes | CDC

CDC provides recommendations for medications used for malaria prophylaxis for those traveling to regions with the highest rate of malaria transmission, these include sub-Saharan Africa, the Indian subcontinent, and Southeast Asia. Please review Table 4.10.2 from the CDC Malaria site to find regimens and dosing. Malaria contractability does vary with seasons; the highest risk is during or just after the rainy season, between May and December.

Malaria treatment should be initiated after the diagnosis has been confirmed. The drugs used vary depending on the species and/or area of acquisition. Presumptive treatment should be reserved for extreme circumstances, such as strong clinical suspicion of severe disease in a setting where prompt laboratory diagnosis is not available. Once diagnosed, malaria must be treated immediately. If not treated promptly, malaria may progress to severe disease, a life-threatening stage, in which mental status changes, seizures, renal failure, acute respiratory distress syndrome, coma, and death may occur. A CDC Malaria Hotline can be reached at 770-488-7788 or toll-free at 855-856-4713 from 9 a.m. to 5 p.m. Eastern Time. After hours, on weekends, or on holidays, call the CDC Emergency Operations Center at 770-488-7100 and ask the operator to contact the subject matter expert on call for the Malaria Branch. Table 4.10.1 from the CDC Malaria site contains guidance on medication regimens for the treatment of Malaria.