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Diagnosis of Malaria

Malaria can be suspected based on a patient's symptoms and physical findings at examination. However, for a definitive diagnosis to be made, laboratory tests must reveal the malaria parasites or their components.

Incubation Period

Following the infective bite by the Anopheles mosquito, a period of time called the incubation period goes by before the first symptoms appear. The incubation period for P. Falciparum, the parasite common in Zambia, is about 7 days.

Clinical Diagnosis

Clinical diagnosis is based on the patient's symptoms and on physical findings at examination.  The first symptoms of malaria; fever, chills, sweats, headaches, muscle pains, nausea and vomiting, are often not specific and are also found in other diseases (such as the "flu" and common viral infections). Likewise, the physical findings are often not specific such as elevated temperature, perspiration, tiredness.

In severe malaria (caused by Plasmodium falciparum), clinical findings (confusion, coma, neurological focal signs, severe anemia, respiratory difficulties) are more striking.

Health centers in Zambia that do not have laboratory capabilities or access to Rapid Diagnostic Tests (RDTs) rely solely on the clinical diagnosis of malaria.

Microscopic Diagnosis

Malaria parasites can be identified by examining a drop of the patient's blood, spread out as a "blood smear" on a microscope slide. Prior to examination, the specimen is stained to give to the parasites a distinctive appearance. This technique remains the gold standard for laboratory confirmation of malaria.

Antigen Detection

Various test kits are available to detect antigens derived from malaria parasites. Such tests provide results in 2-10 minutes. These "Rapid Diagnostic Tests" (RDTs) offer a useful alternative to microscopy in situations where reliable microscopic diagnosis is not available. Malaria RDTs are currently used in some clinical settings and programs. However, before malaria RDTs can be widely adopted, several issues remain to be addressed, including lowering their cost and ensuring their adequate performance under adverse field conditions.

Molecular Diagnosis

Parasite nucleic acids are detected using polymerase chain reaction (PCR). This technique is more accurate than microscopy. However, it is expensive, and requires a specialized laboratory. In Zambia, research institutions such as the Tropical Diseases Research Centre, use molecular diagnosis to confirm microscopic diagnosis.

For a more detailed description of laboratory diagnostic technique including blood smears and reading results check out Virtual Naval Hospital Appendix 3.

 Two Types of Malaria

Since infection with malaria parasites may result in a wide variety of symptoms, ranging from absent or very mild symptoms to severe disease and even death malaria disease can either be categorized as uncomplicated or severe (complicated) . In general, malaria is a curable disease if diagnosed and treated promptly and correctly.

Uncomplicated Malaria

The classical (but rarely observed) malaria attack lasts 6-10 hours. It consists of:

·a cold stage (sensation of cold, shivering)

·a hot stage (fever, headaches, vomiting; seizures in young children)

·and finally a sweating stage (sweats, return to normal temperature, tiredness)

More commonly, the patient presents with a combination of the following symptoms:

·Fever

·Chills

·Sweats

·Headaches

·Nausea and vomiting

·Body aches

·General tiredness

In P. falciparum malaria, additional findings may include:

·Mild jaundice

·Enlargement of the liver

·Increased respiratory rate

Severe Malaria

Severe malaria occurs when P. falciparum infections are complicated by serious organ failures or abnormalities in the patient's blood or metabolism. The manifestations of severe malaria include:

·Cerebral malaria, with abnormal behavior, impairment of consciousness, seizures, coma, or other neurological abnormalities

·Severe anemia due to hemolysis (destruction of the red blood cells)

·Hemoglobin in the urine due

·Fluid buildup in the lungs or acute respiratory distress syndrome (ARDS)

·Abnormalities in blood coagulation and decrease in blood platelets

·Cardiovascular collapse and shock

Other manifestations that should raise concern are:

·Acute kidney failure

·Hyperparasitemia, where more than 5% of the red blood cells are infected by malaria parasites

·Excessive acidity in the blood and tissue fluids

·Low blood glucose levels

Severe malaria occurs most often in persons who have no immunity to malaria or whose immunity has decreased. These include all residents of areas with low or no malaria transmission, and young children and pregnant women in areas with high transmission.  In all areas, severe malaria is a medical emergency and should be treated urgently and aggressively.

Treatment of Malaria

What is the treatment for malaria?
After diagnosis is confirmed, patients (except pregnant women and children who weigh less than 10kg) receive a treatment with Coartem. Coartem is the new first line treatment in Zambia and has now been launched in all districts. Sulfadoxine/pyrimethamine (SP or Fansidar) should be used if Coartem is not available.  Since the malaria strain in Zambia has been shown to be overwhelmingly resistant to chloroquine, this drug is no longer used.  No one who contracts malaria in Zambia should take chloroquine tablets or receive chloroquine injections.  If a child or pregnant women shows a lack of response after being treated with SP, they should then take quinine tablets (not chloroquine).

What is "Presumptive Treatment?"

In endemic areas (such as Zambia), the great prevalence of malaria like symptoms and lack of resources such as microscopes and trained microscopists have led health facilities to use "presumptive treatment". Patients who suffer from a fever that does not have any obvious cause are presumed to have malaria and are treated for that disease, based only on clinical suspicion, and without the benefit of laboratory confirmation.

This practice is practical in that it allows for the treatment of a potentially fatal disease, however, it also leads to incorrect diagnoses and unnecessary use of anti-malarial drugs. This results in additional expenses and increases the risk of selecting for drug-resistant parasites.

What if a woman infected with malaria is pregnant?
Pregnant women who are infected with malaria during their second or third trimester should take SP, not Coartem. Pregnant women infected with malaria during their first trimester should take quinine (NOT chloroquine) tablets.

Pregnant women in Zambia should receive intermittent presumptive treatment (IPT) for malaria as part of routine antenatal care, even if they do not have symptoms. (See Malaria In Pregnancy on this website.)
 

The source of much of the information on diagnosis was taken from the CDC website on malaria.