An infectious disease transmitted by the bite of infected mosquitoes carrying any of the four different protozoa of the Plasmodium (P) genus, and is characterized causing intense, periodic chills, fever, sweating, and enlarged spleen.

All species have the same life cycle. Transmission occurs when a female Anopheles mosquito feeds on a person with malaria and ingests blood-containing gametocytes. Following this, gametocytes inside the mosquito reproduce and develop into infective spores. When the mosquito feeds on another human, it releases these sporozoites, and liver cells quickly become infected. This does not produce clinical illness. However, schizogony occurs within infected liver cells; 1 to 2 weeks later they rupture and release organisms that invade red blood cells (RBC). Repeated cycles of invasion that rupture RBCs are responsible for the clinical symptoms. Simultaneously, a separate cycle of development results in the formation of malarial cells in RBCs. These are clinically irrelevant; however, they do infect anopheline mosquitoes and thus maintain the parasite's life cycle. This type of malaria is protective against P. falciparum infection; sickle cell disease or trait; glucose-6-phosphate dehydrogenase (G6PD) deficiency; and hereditary ovalocytosis. It is resistant to P. vivax infection.

P. vivax has an incubation period of 10 to 20 days; the period for P. falciparum is 12 to 14 days; and the period for P. malariae is about a month. In temperate climates, some strains of P. vivax may not demonstrate clinical illness for a year. A person who has taken chemoprophylaxis may have an atypical course of the disease, and the incubation may extend for weeks after the drug is stopped. Instead of periodic chills and fever, the person may have headache, backache, and irregular fever; and parasites may be difficult to find in blood samples. Common manifestations in all forms of malaria include anemia, jaundice, enlarged spleen, enlarged liver, and the sudden recurrence of symptoms which coincides with the release of merozoites from ruptured RBCs. A sudden recurrence starts with the following manifestations: discomfort; abrupt chills and fever rising to 39 to 41° C (102 to 106° F); rapid and thready pulse; polyuria; and increasing headache and nausea. The fever drops, and profuse sweating occurs over a period of 2 to 3 hours. Recurrences typically occur about every 48 hours with P. vivax, P. falciparum, and P. ovale, and about every 72 hours with P. malariae. These intervals can vary in mixed infections, or early in the course of infection (especially with P. falciparum).

During pregnancy, the presence of malaria can be a serious threat to both the mother and fetus. When one must travel to an endemic area, prevention should be practiced and chloroquine should be given. After a person leaves an endemic area, resistance lasts only a few months and protects against only those parasite strains to which the person was exposed.

The direct way to diagnose malaria is to prepare and examine blood smears using oil immersion magnification.

Fluorescent staining is one of two new techniques for detecting malaria parasites in peripheral blood specimens. DNA probes have been developed to detect parasites. Commercial testing kits are now available for testing antigens as an alternative to looking in a microscope.

In the treatment of an acute attack, the drug of choice against P. malariae, P. ovale, P. falciparum and P. vivax is chloroquine. The patient usually becomes afebrile in 48 to 72 hours. In P. falciparum, slow intravenous (IV) administration of chloroquine is indicated if the oral drug cannot be tolerated. In patients with rapidly increasing numbers of parasites in the blood, the use of exchange transfusions in combination with parenteral antimalarials will rapidly remove infected RBCs and may be lifesaving. In cerebral malaria, the use of corticosteroids is contraindicated.

In patients with chloroquine-resistant P. falciparum, the treatment is with oral quinine sulfate or, in severe cases, with intravenous quinidine or quinine dihydrochloride. Parenteral therapy needs to be continued until parasites are less than 1%, or oral medication is tolerated. Because of a possible relapse, it is usual for this drug regimen to be supplemented with other medications.

Liver infections may persist for 2 to 3 years in P. viva and P. ovale, but not with P. falciparum or P. malariae. These dormant parasites become the basis for relapses, and complicate chemotherapy because the drugs used to treat clinical disease do not kill them. When infection is transmitted by blood transfusions, through sharing of contaminated needles, or congenitally, the pre-erythrocytic malarial life cycle is by-passed.

Anemia and jaundice are caused by destruction of the membrane of infected red blood cells, phagocytosis of infected and uninfected RBCs in the spleen, and ineffective production and development of blood cells in the bone marrow with accompanying malnutrition.

1. May be entitled to special monthly compensation where the Veteran has a single service-connected disability rated as 100% and/or other requirements/qualifications under 38 CFR 3.350 [Special monthly compensation ratings]. Also reference 38 CFR 3.155(d)(2).  

2. This disease shall be granted service connection as a result of tropical service, although not otherwise established as incurred in service if manifested to a compensable degree within the applicable time limits under §3.307 or §3.308 following service in a period of war or following peacetime service provided the rebuttable presumption provisions of §3.307are also satisfied [38 CFR connection].

3. This disease shall be granted service connection as a result of service in the Southwest Asia theater of operations during the Gulf War as defined in 38 CFR 3.317(e) or Afghanistan on or after September 19, 2001 and the disease becomes manifest to a compensable degree within one ear of the date of separation from a qualified period of service as defined in 38 CFR 3.317 (c)(3)(ii). 

4. Consider service connection on a presumptive basis as a tropical disease (38 CFR §3.307; §3.308; §3.309 (b)).

• The diagnosis of malaria, both initially and during relapse, depends on the identification of the malarial parasites in blood smears or other specific diagnostic laboratory tests such as antigen detection, immunologic (immunochromatographic) tests, and molecular testing such as polymerase chain reaction tests.

• Rate under the appropriate body system any residual disability of infection, which includes, but is not limited to, liver or splenic damage, and central nervous system conditions.

• (38 CFR 4.88 (b) [Schedule of ratings-infectious diseases, immune disorders and nutritional deficiencies]).