Diagnosis of malaria

Clinical presentation and symptom assessment

The first stage of the diagnostic search consists of identifying typical symptoms of intoxication (marked weakness, nausea, headache, loss of appetite) and characteristic febrile attacks.

An acute onset is typical for all forms of the disease, while during the first 5–7 days the fever may be continuous and irregular. Subsequently, a classical malarial paroxysm develops, which goes through three consecutive phases:

1. Rigors (intense chills).
2. Fever with a rapid rise in temperature to high levels.
3. Profuse sweating and temperature drop.

Between attacks, a period of apyrexia occurs, when the patient's well-being becomes quite satisfactory. The periodicity of paroxysms directly depends on the causative agent. Thus, in infection with Plasmodium vivax and Plasmodium ovale, attacks recur every other day, while with Plasmodium malariae they recur every two days (often from the first days). In infection with Plasmodium falciparum, the fever often remains irregular for a long time, and diarrhea may also occur.

Physical examination and risk groups

During the physical examination, the physician should pay attention to the color of the skin: with a prolonged course of the disease, a pale-yellow hue appears. A specific sign of all forms of malaria is the development of hypochromic hemolytic anemia and hepatosplenomegaly (enlargement of the liver and spleen).

The epidemiological history plays a crucial role. It is necessary to ascertain:

• the fact of staying in an unfavorable area (taking into account the season);
• a history of malaria in the past;
• cases of surgical treatment or blood transfusion over the past 3 months;
• possible injection drug use.

The patient's life history is also evaluated. Natural resistance to malaria decreases in nutritional deficiencies, chronic viral infections, helminthiases, as well as in blood disorders (e.g., G6PD deficiency or hemoglobinopathies). Pregnant women and young children constitute a special risk group—in them, the level of parasitemia is usually significantly higher, and the course of the disease is more severe.

Laboratory and instrumental diagnostics

The second stage of diagnostics aims at the final confirmation of the diagnosis. The basis of verification is microscopic blood examination:

• Blood smear is used to determine the specific species of the parasite (P. falciparum, P. vivax, P. ovale, P. malariae).
• Thick blood film is necessary for the quantitative count of parasites per 1 µL.

Additionally prescribed:

• Complete blood count: looking for signs of anemia (evaluation of hemoglobin, erythrocytes, color index), leukocytosis, thrombocytopenia, changes in ESR.
• Biochemical blood test: monitoring liver and kidney function (ALT, AST, bilirubin, creatinine, urea, glucose).
• Urinalysis (general and Nechiporenko test): detection of casts, erythrocytes, urobilin.
• Evaluation of acid-base balance to rule out metabolic acidosis.

According to indications, abdominal ultrasound, ECG, chest X-ray are performed, and related specialists (neurologist, nephrologist, endocrinologist) are consulted.

Formulation of the detailed diagnosis

The third stage is the synthesis of the obtained data. A complete clinical diagnosis must include three mandatory components:

1. Etiological evaluation: indication of the pathogen species based on the results of the thin smear (e.g., vivax malaria).
2. Quantitative evaluation: level of parasitemia from the thick film (number of parasites in 100 visual fields or per 100 leukocytes).
3. Clinical evaluation: severity grade, presence of relapses and complications (such as cerebral malaria, infectious-toxic shock, acute renal failure, or pulmonary edema, which are most characteristic of P. falciparum).

Based on this diagnosis, the infectious disease specialist determines the tactics of etiotropic and pathogenetic treatment.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Chemoprophylaxis drugs: mefloquine administration regimens and alternative options
• Specific methods of protection against mosquito bites in endemic zones
• Complications of falciparum malaria: cerebral form and acute renal failure
• Tactics of etiotropic and pathogenetic treatment of various forms of malaria
• Criteria for discharging a convalescent and follow-up medical examination (dispensary) rules

Other topics in the "Vector-borne infections" section

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