Treatment of Malaria: Guidelines For Clinicians (United States)
Malaria is a nationally notifiable disease. We encourage clinicians to report all cases of laboratory-confirmed malaria to their state health department to help CDC’s surveillance efforts. Refer to our information on the Malaria Case Surveillance Report Form.
Because malaria cases are relatively rare in North America, misdiagnosis by clinicians and laboratorians has been a reoccurring issue. However, malaria is a common cause of febrile illness in areas where it is transmitted; therefore, the diagnosis and management of malaria should routinely be considered for any febrile person who has traveled to an area with known malaria transmission in the several months preceding symptom onset. The CDC’s Algorithm for Diagnosis and Management of Malariapdf icon provides guidance on the recommended steps to adequately assess and treat malaria patients.
Symptoms of malaria are generally non-specific and most commonly consist of fever, headache, malaise, weakness, gastrointestinal complaints (nausea, vomiting, diarrhea), neurologic complaints (dizziness, confusion, disorientation, coma), back pain, myalgia, chills, and/or cough. The diagnosis of malaria should also be considered in any person with fever of unknown origin regardless of travel history.
Patients suspected of having malaria infection should be urgently evaluated. Treatment for malaria should not be initiated until the diagnosis has been confirmed by laboratory testing. “Presumptive treatment”, i.e., without the benefit of prior laboratory confirmation, should be reserved for extreme circumstances, such as strong clinical suspicion or severe disease in a setting without availability of prompt laboratory confirmation, usually by microscopy.
Laboratory diagnosis of malaria can be made through microscopic examination of thick and thin blood smears. Thick blood smears are more sensitive in detecting malaria parasites because the blood is more concentrated allowing for a greater volume of blood to be examined; however, thick smears are more difficult to read. Thin smears aid in parasite species identification and quantification. Blood films need to be read immediately; off-hours, qualified personnel who can perform this function should always be on-call. A negative blood smear makes the diagnosis of malaria unlikely. However, because non-immune individuals may be symptomatic at very low parasite densities that initially may be undetectable by blood smear, blood smears should be repeated every 12–24 hours for a total of three sets before the diagnosis of malaria can be ruled out.
After malaria parasites are detected on a blood smear, the parasite density should then be estimated. The parasite density can be estimated by looking at a monolayer of red blood cells (RBCs) on the thin smear using the oil immersion objective at 100x. The slide should be examined where the RBCs are more or less touching (approximately 400 RBCs per field). The parasite density can then be estimated from the percentage of infected RBCs, after counting 500 to 2,000 RBCs. Gametocytes should not be counted when determining parasitemia. More information on diagnostic procedures on malaria can be found on CDC’s DPDx website.
In addition to microscopy, other laboratory diagnostic tests are available. Several antigen detection tests (rapid diagnostic tests or RDTs) using a “dipstick” or cassette format exist, but only one, BinaxNOW™, is approved for general diagnostic use in the United States. RDTs can more rapidly determine that the patient is infected with malaria, but they are less sensitive than microscopy and cannot confirm the species or the parasite density. Therefore, microscopy should also be done as soon as possible to confirm RDT results, and determine both species and parasite density. Laboratories that do not provide in-house on-the-spot microscopy services should maintain a stock of malaria RDTs, so they will be able to perform malaria diagnostic testing urgently when needed.
Parasite nucleic acid detection using polymerase chain reaction (PCR) is more sensitive and specific than microscopy but can be performed only in reference laboratories. Therefore, PCR results are often not available quickly enough for routine diagnosis. However, PCR is a very useful tool for confirmation of species and detecting of mutations associated with drug resistance. CDC offers malaria–drug-resistance testing for all malaria diagnosed in the United States free of charge. Serologic tests, also performed in reference laboratories, are not practical for routine diagnosis of acute malaria. Your state health department or CDC can be contacted for more information on utilizing one of these tests.
It is preferable that treatment for malaria not be initiated until the diagnosis has been established by laboratory testing. “Presumptive treatment”, i.e., without the benefit of prior laboratory confirmation, should be reserved for extreme circumstances, such as strong clinical suspicion or severe disease in a setting where prompt laboratory diagnosis is not available.
Once the diagnosis of malaria has been made, appropriate antimalarial treatment must be initiated immediately. Treatment should be guided by the following four main factors:
- Infecting Plasmodium species;
- Clinical status of the patient;
- Expected drug susceptibility of the infecting parasite as determined by the geographic area where the infection was acquired; and
- Previous use of antimalarials, including those taken for malaria chemoprophylaxis.
Infecting Plasmodium species: Determination of the infecting Plasmodium species for treatment purposes is important for three main reasons. Firstly, P. falciparum and P. knowlesi infections can cause rapidly progressive severe illness or death, while the other species, P. vivax, P. ovale, and P. malariae, are less likely to cause severe disease. Secondly, P. vivax and P. ovale infections also require treatment for the hypnozoites, which remain dormant in the liver and can cause relapsing episodes. Thirdly, P. falciparum and P. vivax species have different drug resistance patterns in different geographic regions of the world. Finally, for P. falciparum and P. knowlesi infections, the urgent initiation of appropriate therapy is especially critical.
Clinical status of the patient: Patients diagnosed with malaria are generally categorized as having either uncomplicated or severe malaria. Patients diagnosed with uncomplicated malaria can be effectively treated with oral antimalarials. However, patients who have one or more of the following clinical criteria (impaired consciousness/coma, severe anemia [hemoglobin <7 g/dL], acute kidney injury, acute respiratory distress syndrome, circulatory collapse/shock, disseminated intravascular coagulation, spontaneous bleeding, acidosis, jaundice [along with at least one other sign of severe malaria]) and/or parasite density of ≥5% are considered to have manifestations of severe disease and should be treated aggressively with intravenous antimalarial therapy.
Drug susceptibility of the infecting parasites: Knowledge of the geographic area where the infection was acquired provides information on the likelihood of drug resistance of the infecting parasite and enables the treating clinician to choose an appropriate drug or drug combination. If the diagnosis of malaria is suspected and cannot be confirmed or if the diagnosis of malaria is confirmed but species determination is not possible, antimalarial treatment effective against chloroquine-resistant P. falciparum must be initiated immediately and revisited once confirmatory results become available.
Previous use of antimalarials: It is important to consider if a malaria infection occurred while an individual was taking a drug for malaria chemoprophylaxis. In this case, the treatment regimen should not involve the drug or drug combination used for prophylaxis.
The Malaria Treatment Tablepdf icon can be used as a guide for treatment of malaria in the United States. The drug or drug combination recommended for each specific situation are listed in bold on the first line of each box in the adult and pediatric dosing columns. It is important to note that the base/salt conversions for antimalarials are a recurrent source of confusion and can contribute to treatment errors. In the treatment tablepdf icon, where appropriate, the antimalarial dose is expressed in base with the salt equivalency noted in parentheses.
After initiation of treatment, the patient’s clinical and parasitological status should be monitored. In infections with P. falciparum, P. knowlesi, or suspected chloroquine-resistant P. vivax, blood smears should be repeated every 12–24 hours to monitor parasitological response to treatment, i.e., decrease in parasite density. Gametocytes should not be counted in assessing parasite density.
CDC clinicians are on call 24/7 to provide advice to healthcare providers on the diagnosis and treatment of malaria and can be reached through the CDC Malaria Hotline (770) 488-7788 (toll free: (855) 856-4713) Monday–Friday, 9 am to 5 pm EST. Off-hours, weekends, and federal holidays, call (770) 488-7100 and ask to have the malaria clinician on call paged.
P. falciparum or Species Not Identified — Acquired in Areas With Chloroquine Resistance
For P. falciparum infections acquired in areas with chloroquine resistance, four treatment options are available. These include artemether-lumefantrine (Coartem™), which is the preferred option if readily available, and atovaquone-proguanil (Malarone™). These are fixed-dose combination therapies that can be used for pediatric patients ≥5 kg. Quinine sulfate plus doxycycline, tetracycline, or clindamycin is the next treatment option. For the quinine sulfate combination options, quinine sulfate plus either doxycycline or tetracycline is generally preferred to quinine sulfate plus clindamycin because there are more data on the efficacy of quinine plus doxycycline or tetracycline. Quinine should be given for 3 days, except for infections acquired in Southeast Asia where 7 days of treatment is required. The fourth option, mefloquine, is associated with rare but potentially severe neuropsychiatric reactions when used at treatment dose. We recommend this fourth option only when the other options cannot be used. In addition, mefloquine is not recommended for infections acquired in certain parts of Southeast Asia due to drug resistance. Options for treatment of pregnant women is presented in the “Alternatives for Pregnant Women” section below. Due to the risk of progression to severe disease, uncomplicated malaria treatment should be initiated as soon as possible with the regimen that is most readily available. In addition, clinicians should hospitalize patients with P. falciparum infection to monitor clinical response and check parasitemia every 12–24 hours. Then, clinicians can consider outpatient completion of treatment for patients with improved clinical symptoms and decreasing parasitemia.
For pediatric patients, the treatment options are the same as for adults except the drug dose is adjusted by patient weight, and artemether-lumefantrine (Coartem™) and atovaquone-proguanil (Malarone™) can only be used in children ≥5 kg. The pediatric dose should never exceed the recommended adult dose. Pediatric dosing with quinine may be difficult due to unavailability of non-capsule forms of this antimalarial. If unable to provide pediatric doses of quinine, consider one of the other three options. If using a quinine-based regimen for children less than 8 years old, doxycycline and tetracycline are generally not indicated; therefore, quinine can be given in combination with clindamycin as recommended above. In rare instances, doxycycline or tetracycline can be used in combination with quinine in children less than 8 years old if other treatment options are not available or are not tolerated, and the benefit of adding doxycycline or tetracycline is judged to outweigh the risk.
For infections attributed to “species not identified” in areas with chloroquine resistance that are subsequently diagnosed as being due to P. vivax or P. ovale, additional treatment with primaquine or tafenoquine should be administered (see P. vivax and P. ovale, section below).
P. falciparum or Species Not Identified — Acquired in Areas Without Chloroquine Resistance
For P. falciparum infections acquired in areas without chloroquine-resistant strains, which include Central America west of the Panama Canal, Haiti, and the Dominican Republic, patients can be treated with oral chloroquine. Alternatively, hydroxychloroquine may be used at recommended doses.
In addition, any of the regimens listed for the treatment of chloroquine-resistant malaria may be used for the treatment of chloroquine-sensitive P. falciparum malaria. Prompt initiation of an effective regimen is vitally important, so using any one of the effective regimens that is readily available would be the preferred strategy. Due to the risk of progression to severe disease in patients with P. falciparum infection, patients should be hospitalized to monitor clinical response, and check parasite density every 12–24 hours until clinical presentation improves and a decrease in parasite density becomes apparent. Then, clinicians can consider outpatient completion of treatment for patients with improved clinical symptoms and decreasing parasitemia. If infections initially attributed to “species not identified” are subsequently diagnosed as being due to P. vivax or P. ovale, additional treatment with primaquine or tafenoquine should be administered (see P. vivax and P. ovale section below).
P. malariae and P. knowlesi
There has been no widespread evidence of chloroquine resistance in P. malariae and P. knowlesi species; therefore, chloroquine (or hydroxychloroquine) may still be used for both of these infections. In addition, any of the regimens listed above for the treatment of chloroquine-resistant P. falciparum may be used for the treatment of P. malariae and P. knowlesi infections. Due to the risk of complications among patients with P. knowlesi, clinicians should consider hospitalization to monitor clinical response and check parasite density every 12–24 hours until clinical presentation improves and a decrease in parasite density becomes apparent.
P. vivax and P. ovale
Chloroquine (or hydroxychloroquine), remains an effective choice for P. vivax and P. ovale infections except for P. vivax infections acquired in Papua New Guinea or Indonesia as there is high prevalence of chloroquine-resistant P. vivax in these countries. Rare cases of chloroquine-resistant P. vivax have also been documented in Burma (Myanmar), India, and Central and South America. Persons acquiring P. vivax infections from regions other than Papua New Guinea or Indonesia should initially be treated with chloroquine. Note that, if chloroquine is not available, antimalarial regimens composed of artemether-lumefantrine, atovaquone-proguanil, quinine sulfate plus doxycycline or tetracycline or clindamycin, or mefloquine are effective. While the first three regimens are equally recommended, mefloquine should be used as a last resort due to its side effect profile. If chloroquine is given and the patient has an inadequate response including persistence or worsening of clinical symptoms or no decrease in parasite density, treatment should be changed to one of the regimens recommended for chloroquine-resistant P. vivax infections (see below), and your state health department and CDC should be notified (CDC Malaria Hotline: (770) 488-7788, Monday–Friday, 9 am to 5 pm EST; (770) 488-7100 after hours, weekends, and holidays).
Persons acquiring P. vivax infections in Papua New Guinea or Indonesia should initially be treated with a regimen recommended for chloroquine-resistant P. vivax infections. These include artemether-lumefantrine, atovaquone-proguanil, or quinine sulfate plus doxycycline or tetracycline or clindamycin, and are equally recommended. Mefloquine can be used if no other options are available, because of rare but potentially severe neuropsychiatric reactions when used at treatment dose.
In addition to requiring the acute phase treatment of blood stage parasites, P. vivax and P. ovale infections can relapse due to hypnozoites, which are dormant forms that remain in the liver. To eradicate the hypnozoites, patients should be treated with either tafenoquine (KrintafelTM) or primaquine phosphate. Tafenoquine can be used in patients 16 years old and over and is given as a single dose. If primaquine phosphate is used, CDC recommends a dose of 30 mg (base) by mouth daily for 14 days. Due to reduced efficacy of primaquine in patients ≥70 kg, the total dose of primaquine should be adjusted in these patients to 6 mg/kg. This total dose should be given in daily doses of 30 mg for the number of days needed to complete the total dose. A daily dose >30 mg is not recommended due to safety concerns. Because both tafenoquine and primaquine can cause hemolytic anemia in persons with glucose-6-phosphate-dehydrogenase (G6PD) deficiency, quantitative G6PD testing must occur prior to starting treatment with these drugs.
For persons with intermediate G6PD deficiency, clinicians could consider giving primaquine at 45 mg (base) by mouth once per week for 8 weeks with close monitoring for hemolysis. Consultation with an expert in infectious disease and/or tropical medicine is advised if this alternative regimen is considered in intermediate G6PD-deficient individuals. Primaquine and tafenoquine must not be used during pregnancy (see section on alternatives for pregnant women below). Tafenoquine must not be used in children less than 16 years old, or in those with a history of a psychotic disorder. Patients with G6PD deficiency who are not expected to tolerate primaquine or tafenoquine should be put on chloroquine prophylaxis (300 mg [base] po once a week) for 1 year from the acute infection, as most of the relapses resulting from hypnozoite reactivation occur within this timeframe.
For pediatric patients ≥5 kg, the treatment options for the acute phase are the same as for adults except the drug dose is adjusted by patient weight. The pediatric dose should never exceed the recommended adult dose. In addition, for children <8 years of age, doxycycline and tetracycline are generally not indicated; therefore, the other treatment options should be used. For pediatric patients <5 kg, either mefloquine or quinine plus clindamycin are the only options. If those are not available or tolerated and if the treatment benefits outweigh the risks, atovaquone-proguanil or artemether-lumefantrine could be used in those instances. Primaquine should be given to pediatric patients only after they have been screened for G6PD deficiency, and tafenoquine can only be used in patients 16 years or older.
Malaria infection in pregnant women is associated with high risks of both maternal and perinatal morbidity and mortality. While the mechanism is poorly understood, pregnant women have a reduced immune response and, therefore, less effectively clear malaria infections. In addition, 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 area. Malaria infection during pregnancy can lead to miscarriage, premature delivery, low birth weight, congenital infection, and/or perinatal death.
For pregnant women diagnosed with uncomplicated malaria caused by P. malariae, P. ovale, chloroquine-sensitive P. vivax, or chloroquine-sensitive P. falciparum infection, prompt treatment with chloroquine or hydroxychloroquine (treatment schedule as for non-pregnant adult patients) is recommended. For chloroquine-resistant P. vivax infections, quinine plus clindamycin, or mefloquine should be given instead. For women in their second or third trimesters, artemether-lumefantrine is an additional option.
For P. vivax or P. ovale infections, primaquine phosphate and tafenoquine for radical treatment of hypnozoites should not be given during pregnancy. Pregnant patients with P. vivax or P. ovale infections should be maintained on chloroquine prophylaxis for the duration of their pregnancy. The chemoprophylactic dose of chloroquine phosphate is 300 mg base (=500 mg salt) orally once per week. After delivery, for pregnant patients with P. vivax or P. ovale infections who are not G6PD deficient, subsequent treatment with primaquine phosphate or tafenoquine is needed, but will depend on breastfeeding. If not breastfeeding, either drug can be used. For women who are breastfeeding, infants should be tested for G6PD deficiency and if found to have normal activity, oral primaquine phosphate can be given to the mother. Tafenoquine is not recommended during breastfeeding. Women who after delivery cannot take primaquine or tafenoquine should be maintained on weekly chloroquine prophylaxis for a total of 1 year after the acute malaria episode.
Pregnant women diagnosed with uncomplicated malaria caused by chloroquine-resistant P. falciparum infection in the second and third trimesters can be treated with artemether-lumefantrine. Artemether-lumefantrine may be used during the first trimester if other treatment options are not available, and if the potential benefit is judged to outweigh the potential risks. In addition, pregnant women of all gestational ages can be treated with mefloquine or a combination of quinine sulfate and clindamycin. Quinine treatment should continue for 7 days for P. falciparum infections acquired in Southeast Asia and for 3 days for infections acquired elsewhere; clindamycin treatment should continue for 7 days regardless of where the infection was acquired.
Pregnant women diagnosed with severe malaria should be treated aggressively with parenteral antimalarial therapy as described below.
Doxycycline and tetracycline are generally not indicated for use in pregnant women. However, in rare instances, doxycycline or tetracycline can be used in combination with quinine if other treatment options are not available or are not being tolerated, and the benefit of adding doxycycline or tetracycline is judged to outweigh the risks.
Atovaquone-proguanil is not indicated for use in pregnant women because of the paucity of data on its safety in pregnant women. However, for pregnant women diagnosed with uncomplicated malaria caused by chloroquine-resistant P. falciparum infection, atovaquone-proguanil may be used if other treatment options are not available or are not being tolerated, and if the potential benefit is judged to outweigh the potential risks.
Patients with manifestations of severe malaria should be treated promptly and aggressively with parenteral antimalarial therapy regardless of the species of malaria seen on the blood smear. If severe malaria is strongly suspected but a laboratory diagnosis cannot be made at that time, blood should be collected for diagnostic testing to be done as soon as it becomes available and parenteral antimalarial drugs should be started.
All patients with severe malaria, regardless of infecting species, should be treated with intravenous (IV) artesunate. Clinicians caring for patients with suspected severe malaria should call CDC to obtain IV artesunate, which is available through CDC as part of an expanded-use investigational new drug (IND) protocol. The CDC Malaria Hotline, (770) 488-7788 or toll free (855) 856-4713, is available Monday–Friday, 9 am–5 pm EST. Outside those hours, providers should call (770) 488-7100 and ask to speak with the CDC Malaria Branch clinician on call.
Severe malaria can progress to a fatal outcome rapidly, so its treatment should be initiated as soon as possible. While timely delivery of IV artesunate is anticipated, healthcare providers should consider treating the patient with an oral treatment while waiting for IV artesunate to arrive. If patient is unable to tolerate oral medications, healthcare providers will need to decide the most feasible strategy to administer oral medicines while awaiting IV artesunate. For example, if this intolerance is due to nausea and vomiting, an anti-emetic preceding the antimalarial may help, and, for comatose patients, a nasogastric tube can be considered.
The preferred antimalarial for interim oral treatment is artemether-lumefantrine (Coartem™) because of its fast onset of action. Other oral options include atovaquone-proguanil (Malarone™), quinine, and mefloquine. Intravenous clindamycin and IV tetracyclines, such as doxycycline, are not recommended. These drugs are slow-acting antimalarials that would not take effect until well after 24 hours, and they are not effective antimalarials for treatment of severe malaria when used alone.
When IV artesunate arrives, immediately discontinue the oral medication and start parenteral treatment. Three doses of IV artesunate should be given as follows:
- Adults and children ≥20 kg: 2.4 mg/kg at 0, 12, and 24 hours;
- Children <20 kg: 3.0 mg/kg at 0, 12, and 24 hours.
The slightly higher dose in children <20 kg is in line with the World Health Organization (WHO) recommendations based on the larger volume of distribution in these children. Patients on treatment for severe malaria should have one set of blood smears (thick and thin smear) performed every 12–24 hours until a negative result (no Plasmodium parasites are detected) is reported.
After the course of IV artesunate is completed, if parasite density is ≤1% (assessed on a blood smear collected 4 hours after the last dose of IV artesunate) and patient can tolerate oral treatment, a full treatment course with a follow-on regimen must be administered. Artemether-lumefantrine (Coartem™) is the preferred follow-on treatment but adequate alternatives are atovaquone-proguanil (Malarone™), quinine plus doxycycline or clindamycin, or mefloquine. Because of a risk of severe neuropsychiatric adverse events at treatment doses, mefloquine should only be used if other options are not available. If the patient received oral treatment prior to receiving IV artesunate, the same medication can be used as follow-on treatment, but a full regimen is required. As for any malaria treatment, the regimen selection should not include the medication used for chemoprophylaxis.
If, after the 3rd IV artesunate dose, the patient’s parasite density is >1%, IV artesunate treatment should be continued with the recommended daily dose until parasite density ≤1% for a maximum 7 days. Doses given at 0, 12, and 24 hours count as 1 day, which means up to 6 additional days. Clinicians should proceed with full-dose oral follow-on treatment as above as soon as parasite density ≤1% and the patient is able to tolerate oral medications. Clinicians can consider placement of nasogastric tube or use of antiemetics to facilitate administration of oral treatment. Call CDC Malaria Hotline if additional artesunate is needed and/or advice on treatment
For those patients with parasite density ≤1% but who still cannot tolerate oral medications after completing IV artesunate treatment, clinicians can (1) continue IV artesunate, 1 dose daily not to exceed a total course of 7 days, or (2) switch to treatment with IV doxycycline (up to 7 days) or IV clindamycin (up to 7 days) and give quinine via nasogastric tube or with antiemetic. Placement of nasogastric tube or use of antiemetics should be considered to facilitate administration of oral treatment. Patients should then receive a full course of the oral follow-on treatment as above. Call CDC Malaria Hotline if additional artesunate is needed and/or advice on treatment.
Intravenous artesunate is safe in infants, children, and pregnant women in the second and third trimesters. There are limited clinical data on women taking IV artesunate in the first trimester of pregnancy, but no harmful effects have been observed. Given that severe malaria is especially life threatening for pregnant women and their fetuses, and the lack of other treatment options for severe malaria in the United States, the benefits of treatment with IV artesunate outweigh the risks and IV artesunate should not be withheld. The only formal contraindication to IV artesunate treatment is known allergy to IV artemisinins.
In addition, IV artesunate is well tolerated. While rare, delayed post-artemisinin hemolytic anemia has been noted in published case reports following treatment of severe malaria with IV artesunate. Persons with higher parasite density seem to have a higher likelihood of delayed hemolytic anemia after treatment with IV artesunate. All persons treated for severe malaria with IV artesunate should be monitored weekly for up to four weeks after that treatment for evidence of hemolytic anemia. Weekly laboratory evaluation should include hemoglobin, reticulocyte count, haptoglobin, lactate dehydrogenase (LDH), and total bilirubin. Depending on the intensity of hemolysis, blood transfusion may be needed.
Previously, CDC recommended exchange transfusion be considered for certain severely ill persons. However, exchange transfusion has not been proven beneficial in an adequately powered randomized controlled trial. In 2013, CDC conducted an analysis of cases of severe malaria treated with exchange transfusion and was unable to demonstrate a survival benefit of the procedure. Considering this evidence, CDC no longer recommends the use of exchange transfusion as an adjunct procedure for the treatment of severe malaria.