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Malaria

Parasitic infection due to protozoa of genus Plasmodium transmitted by the female Anopheles mosquito. There are four plasmodia species: P. falciparum, P. vivax, P. malariae, P. ovale.

Salient features

• Malaria is an acute and chronic protozoan illness characterized by paroxysms of fever, chills, sweats, fatigue, anaemia and splenomegaly.

• Falciparum malaria (severe and complicated malaria) is associated in varying degrees with the following clinical signs:

Cerebral: mental clouding, coma, convulsions, delirium and occasionally localizing signs Hyperpyrexia (>40.5ºC) Haemolysis, oliguria, anuria, pulmonary oedema and macroscopic haemoglobinuria

• Diagnosis is made by presence of protozoa in the blood in thick and thin smear slides. Thick smear for easy detection of parasite and thin smear for identification of species. Note that blood films may be negative even in a severe attack because of sequestration of parasites in the deep capillaries

Principles of therapy

1. All fever cases without any other obvious causes should be presumed as malaria cases and antimalarial drug be given preferably after taking blood smear.

2. Chloroquine is the main antimalarial drug and it is to be used as first line of treatment for the treatment of uncomplicated malaria.

3. In high-risk areas presumptive treatment 25 mg/kg of Chloroquine base is to be given on 3 consecutive days with a single dose of Primaquine 0.75 mg/kg on the first day. High risk area is defined as follows:

i.Recorded deaths due to malaria (on clinical diagnosis or microscopic confirmation) with P. falciparum infection during the transmission period in an endemic area during any of the last 3 years.

ii. Doubling of slide positivity rate (SPR) during the last 3 years provided the SPR in second or third year reaches 4% or more or the average SPR of the last year is 5% or more.

iii.P. falciparum is 30% or more provided SPR is 3% or more during any of the last 3 years.

iv.An area having a focus of chloroquine resistant P. falciparum.

4. In the low risk areas, presumptive treatment 10 mg/kg Chloroquine single dose.

5. Resistance should be suspected if inspite of full treatment and no history of vomiting and diarrhoea, patient does not respond within 72 hours parasitologically. Such patients should be given alternative drug i.e. Sulfa-pyrimethamine (S-P) combination.

6. S-P combination is the antimalarial drug of choice in P. falciparum resistant to chloroquine. The dose is 25 mg/kg of sulfa + 1.25 mg/kg of pyrimethamine which is 3 tablets for the adult (single dose).

7. The dose of Primaquine for P. vivax cases is 0.25 mg/kg daily for 5 days to prevent relapse and for P. falciparum 0.75 mg/kg single dose for gametocidal action.

8. Mefloquine can be given to chloroquine/other antimalarial resistant uncomplicated P. falciparum cases only.

9. Resistance to Chloroquine

• There must be an evidence of falciparum positive blood slide on the first and third days of treatment. WHO classifies resistance to chloroquine into 3 types.

• R1: total disappearance followed by reappearance of the parasite.

• R2: noticeable fall without disappearance of the parasite.

• R3: parasite level almost unchanged, indeed, increased.

Before labeling resistance verify

• that treatment has in fact been taken.

• that the correct dose for weight has been prescribed.

• the patient has not vomited within 30 min of taking medication.

• that there has not been under-dosage due to confusion between the expression of the dosage as a chloroquine base and as a chloroquine salt. Equivalence between salt and base:

130 mg sulphate=150 mg phosphate or diphosphate = 100 mg base.

200 mg sulphate=250 mg phosphate or disphosphate= 150 mg base.

10. In Pregnant woman and infants, primaquine is contraindicated. As no data is available to suggest the safety of artemisinin derivatives in this group, the same is not recommended.

Treatment

Patients of uncomplicated malaria can be managed at primary level but patients with severe malaria with complications should be admitted and managed in a hospital where facilities for detailed investigations and blood transfusion exists.

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