Malaria Disease

BASICS

DESCRIPTION

Malaria is an acute and chronic protozoan infection transmitted by Anopheles mosquitoes to humans. There are four species or Plasmodium that cause human infection.

System(s) affected: Hemic/Lymphatic/Immunologic
Genetics: No known genetic pattern. Glucose-6-phosphate deficiency, sickle cell disease or trait, and hereditary ovalocytosis probably help protect against severe P. falciparum infection.
Incidence/Prevalence in USA: Rare primary outbreaks in US. Most cases are imported. In the US, in 1994, P. falciparum caused 44% of all reported cases, P. vivax 44%, P. malaria 4%, and P. ovale 3%.
Predominant age: All ages
Predominant sex: Male = Female

SIGNS AND SYMPTOMS

Fever
Malaise
Chills
Headache
Nausea
Splenomegaly (especially with chronic infection)
Systolic hypotension
P. falciparum (also known as malignant tertian malaria): Incubation period usually 12-14 days with subsequent high fevers every 48 hours within 2 months of infection. If large parasitemia, can lead to anemia, thrombocytopenia, and vascular collapse. Other complications include gastroenteritis, central nervous system impairment, renal failure, and pulmonary edema. Associated with fatal outcome if severe infection
P. vivax (benign tertian malaria) and P. ovale: Incubation period up to 12 months with high fever every 48 hours. Dormant parasites may remain in the liver causing relapse months after the initial infection
P. malariae (benign quartan malaria): Incubation period approximately 35 days with high fevers every 72 hours. May become chronic and lead to nephrotic syndrome

CAUSES

Plasmodium falciparum, P. malariae, P. vivax, P. ovale

RISK FACTORS

Traveling and/or living in endemic area
Bites from infected Anopheles mosquitoes, or transfusion of infected blood

DIAGNOSIS

LABORATORY

In uncomplicated infection:

Elevated liver function tests and lactate dehydrogenase (>50% of cases)
Thrombocytopenia (40%)
Anemia (25%)
Leukopenia (25%) vs leukocytosis (1-5%)

Drugs that may alter lab results: Antimalarial agents may reduce parasitemia
Disorders that may alter lab results: N/A

PATHOLOGICAL FINDINGS

Malaria causes hemolysis
If infection is severe, hemolysis of parasitized red blood cells activates pro-inflammatory cytokines causing sludging within the microcirculation and localized necrosis
Edema, localized hemorrhage, and the presence of malarial pigments are frequent findings

SPECIAL TESTS

Malarial smear thick preparation obtained every 6-12 hours for 3 samplings. Best to obtain blood during or right after fever spike
Other very promising tests that are yet unapproved by the FDA include monoclonal antibody tests and a dipstick assay

IMAGING

N/A

DIAGNOSTIC PROCEDURES

Malarial peripheral blood smear showing intracellular parasite forms

TREATMENT

APPROPRIATE HEALTH CARE

Inpatient for most cases of falciparum malaria in nonimmune patients. Outpatient for others, except during acute phase if blood products or close observation is required.

GENERAL MEASURES

In severe cases watch for complications, such as severe anemia, and renal failure, otherwise supportive care

SURGICAL MEASURES

N/A

ACTIVITY

May resume activity as soon as the fever is under control. Avoid strenuous exercise if splenomegaly.

DIET

No restrictions; as tolerated

PATIENT EDUCATION

Prevention of future exposures. These measures include prevention of mosquito bites and malarial chemoprophylaxis.

FOLLOW UP

PREVENTION/AVOIDANCE

Use malarial chemoprophylaxis when in an endemic area
Oral therapy for areas with chloroquine-resistant Plasmodium species (most areas)
- Mefloquine (begin 1 week before arrival and continue for 4 weeks after leaving area):
  - Adults: 250 mg (1 tablet) weekly
  - Children: 5-9 kg 1/8 tablet; 10-19 kg 1/4 tablet; 20-30 kg 1/2 tablet; 31-45 kg 3/4 tablet; > 45 kg 1 tablet
Oral therapy for areas with chloroquine-sensitive Plasmodium species
- Chloroquine phosphate (begin 2 weeks before arrival and continue until 4-6 weeks after leaving area):
  - Adults: 300 mg base (500 mg) weekly
  - Children: 5 mg base/kg weekly (max 300 mg base)
Oral therapy for areas with chloroquine and mefloquine resistance
- Doxycycline 100 mg daily. Not for pregnant women or children < 8 years. Begin 1-2 days before arrival and continue for 4 weeks after leaving area

POSSIBLE COMPLICATIONS

P. falciparum: if not treated early, may cause cerebral malaria, acute renal failure, acute gastroenteritis, pulmonary edema, massive hemolysis, and splenic rupture. Death from malaria is virtually limited to P. falciparum infection
P. malariae: nephrotic syndrome may develop in patients with chronic infection
Other complications: seizures, anuria, delirium, coma, dysentery, algid malaria, blackwater fever, hyperpyrexia

EXPECTED COURSE AND PROGNOSIS

Only falciparum infection carries a poor prognosis with high mortality if untreated. However, if diagnosed early and treated appropriately the prognosis is excellent.

MISCELLANEOUS

ASSOCIATED CONDITIONS

N/A

AGE-RELATED FACTORS

Pediatric: N/A
Geriatric: More serious outcome in this age group
Others: N/A

PREGNANCY

Chloroquine is safe. Mefloquine is not recommended unless there are no effective alternatives. Doxycycline, quinine and quinidine should not be used in pregnancy.

OTHER NOTES

Most areas of the world now have chloroquine-resistant P. falciparum (the form of malaria most prevalent worldwide). Some multi-drug resistant strains of P. falciparum and P. vivax are present in Southeast Asia
Current information regarding malaria treatment and prophylaxis is always available from Centers for Disease Control (CDC) in Atlanta, GA

ABBREVIATIONS

N/A

Clinical Investigations

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