Malaria
Etiology protozoan parasites
The etiology of malaria is from the protozoan parasites of the genus Plasmodium
with an asexual stage in humans and a sexual stage in mosquitoes. The four genus are P.
falciparum, P. vivax, P.ovale, and P. malariae.
Transmission and Distribution
The Anopheles mosquito is essential for the development, multiplication, and spread
of malarial disease. The bite from an infected female Anopheles mosquito can occur at
night, but is particularly noted during dusk and dawn periods and is seen at altitudes
less than 2200 meters. Malaria is found throughout the tropical and subtropical areas of
the world usually between 45 N and 40 S latitude with 200-300 million infections and 1.5
million deaths estimated per year. Most deaths are attributable to P. falciparum.
Clinical presentation symptoms
Signs may range from asymptomatic (usually semi-immune patient) to a rapidly fatal
disease. The nonimmune patient usually has acute onset of fever (102-106°) and rigors
(100 percent), headache (66-89 percent), nausea and emesis (41-64 percent), and myalgias
(40-57 percent). Physical findings include fever, diaphoresis, tachypnea, conjunctival
icterus, occasional pulmonary rales, palpable spleen (49-88 percent) and liver (31-44
percent), and alterations of mentation.
Laboratory Evaluation
Abnormal laboratory findings reflect the severity of hemolysis.
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CBC : anemia (25-50 percent), leukopenia (25-36 percent), thrombocytopenia (30-80
percent).
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Peripheral Blood Smear : look for malarial parasites (see diagnosis below).
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Urine : + protein, urobilinogen, conjugated bilirubin, and hemoglobin.
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Chemistry Panel (Lytes, Glucose, BUN, CRE) : Hypoglycemia is frequently seen in
children and pregnant females. Hyponatremia may occur.
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Liver Function Tests : The transaminases AST/ALT are often elevated.
Diagnosis
Diagnosis requires a high index of suspicion and demonstration of malarial
parasites in the peripheral blood. Smears should be obtained initially every 6-8 hours
while the diagnosis is in question for at least 3 days. Smears should be followed every
8-12 hours, if seriously ill, to monitor the effects of therapy and then daily until
parasitemia is resolved. Trophozoites should ideally decrease by 75 percent in first 48
hours and disappear within 7 days although gametes may persist. Thin smears are an
alternative if the lab is unable to prepare and interpret thick smears.
Differential diagnosis
This can include malaria, typhoid fever or other salmonelloses, dengue, influenza,
meningococcemia or other sepsis, amebiasis, relapsing fever, viral encephalitis,
rickettsial diseases, leptospirosis, and endocarditis.
Complicated Malaria
A patient with malaria and any one or more of the following should be
regarded as complicated: *
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Hyperparasitemia: >3 percent RBC's parasitized.
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Hypoglycemia: Serum glucose <60 mg/dl.
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Severe anemia: Hct <21 percent or a rapidly falling Hct.
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Renal failure: Urine output <400 ml/day, BUN >40 mg/dl or CRE >4 mg/dl.
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Hyponatremia: Serum Na < 125 mg/dl.
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Cerebral malaria: Any history or finding of delirium or decreased level of
consciousness.
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Prolonged hyperpyrexia >24 hours.
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High output diarrhea or protracted emesis.
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Any significant cardiac or pulmonary dysfunction.
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Pregnancy: Increased risk to mother and child.
*Cases of complicated malaria should be presumed to be secondary to P. falciparum
and should be treated as a medical emergency with parenteral therapy initially.
Malarial Resistance
P. falciparum
resistance to chloroquine is wide-spread throughout Asia,
Africa, and South America. Only sensitive organisms are reliably found in Central America
above Panama, Haiti, the Dominican Republic, and the Middle East. Resistance to sulfadoxine/pyrimethamine
(Fansidar) is present in Southeast Asia, Africa, and in the
Amazon basin of Brazil. Mefloquine resistance has been widely reported from Southeast Asia
and many parts of Africa. P. Vivax chloroquine
resistance has been recently
described from Papua, New Guinea, and Irian Jaya. P. vivax primaquine resistance
has been reported from Southeast Asia and South America.
Malaria Prevention
Essential concepts
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Assessment of risk and selection of appropriate chemoprophylaxis.
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Use of personal protective measures.
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Command enforcement of chemoprophylaxis and personal protective measures.
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Early identification and investigation of possible cases.
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Mosquito vector control measures, if appropriate.
Personal protective measures
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Avoid night-time exposures when possible.
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Wear long sleeve shirts and long pants with sleeves rolled down.
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Use insect repellent (long acting DEET preparations) and treat uniforms with permethrin.
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Use mosquito bed netting.
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Spray mosquito bed netting with permethrin spray.
Chemoprophylaxis
P. falciparum presence in Region
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Drug
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Toxicity
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Chloroquine-sensitive
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Chloroquine 300 mg/wk
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GI upset
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Chloroquine-resistant
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Mefloquine 250 mg/wk or Doxycycline 100mg/d
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CNS: vertigo
Cardiac: A-V bloc
Photosensitivity, GI upset
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Chloroquine
and Mefloquine
These medications should be taken at least 2 weeks before entering an
endemic area. Doxycycline can be started 1-2 days before exposure. All agents should be
continued for 4 weeks after leaving the risk area. Primaquine is generally indicated for
terminal prophylaxis for military exposures. The following points emphasize the importance
of chemoprophylaxis:
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No prophylaxis regimen is 100 percent effective.
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A single bite may result in infection.
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Any exposure to an endemic area may place an individual at risk.
Malaria Treatment
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Suspicion of malaria.
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Patient exposed to endemic area.
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Fever, rigor, sweats, HA, NNID, altered mental status.
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Peripheral smear - (+) malarial parasites.
Essentials of Malaria Treatment
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Recognize infection ASAP.
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Institute effective therapy immediately.
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Anticipate complications.
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Treat complications and prevent death.
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Prevent recrudescence and relapse.
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Recognize and treat recrudescence and relapse.
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Reduce transmission.
High suspicion of malaria
If the possibility of malarial infection is high in a severely ill patient, and one
is not able to demonstrate parasites, strongly consider empiric therapy for P.
falciparum malaria while continuing to work through the differential diagnosis.
Steroids are contraindicated in cases of cerebral malaria.
References
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Navy Medical Guide to Malaria Prevention and Control, NEHC- TM 6250.98-2, (8/98), Navy
Environmental Health Center, Norfolk, VA 23513-2617
Reviewed and revised by CAPT Beecham, MC, USN, Naval Environmental Preventive Medicine
Unit 6, Pearl Harbor, HI (1999).
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Preface
· Administrative Section
· Clinical Section
The
General Medical Officer Manual , NAVMEDPUB 5134, January 1, 2000
Bureau
of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C.,
20372-5300
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