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Malaria

Title               

Ñ    Malaria

Definition

Disease caused by:

Ñ    Protozoan parasites

Of the:

Ñ    Genus plasmodium

Aetiology

Causative organisms

Ñ    Plasmodium vivax

Ñ    Plasmodium falciparum

Ñ    Plasmodium ovale

Ñ    Plasmodium malariae

Pathogenesis

Vector

Ñ    Anopheles mosquito

Stages

Ñ    Mosquito:

Developmental cycle 7-20 days (depending on temperature) culminates in infective sporozoites migrating to the salivary glands of the mosquito

Ñ    Sporozoites inoculated into host

Ñ    Those not destroyed by the host’s immune response are taken up by the liver

Ñ    Liver stage:

Multiply to form merozoites, which are released, into the blood stream

P. vivax and P. ovale delayed forms may occur :

Hypnozoites

Ñ    Red cell stage:

Merozoites mature into trophozoites, which form schizonts, which again form merozoites

The merozoites may infect fresh red cells following cell rupture or develop into gametocytes, which are taken up by mosquitoes and complete the cycle

P. falciparum

Ñ    Red cells containing parasites adhere to capillary walls causing obstruction and ischaemia

Ñ    Rupture of schizonts releases toxins and stimulates cytokine release

Clinical Features:

History

Incubation period

Ñ    10-21 days

E&M

Ñ    Fever, chills and rigors

GIT

Ñ    Vomiting

Ñ    Diarrhoea

CNS

Ñ    Headache

Examination

HS

Ñ    Hepatosplenomegaly

Complications

Plasmodium vivax

Plasmodium ovale

HS

Ñ    Anaemia

Ñ    Hyperreactive splenomegaly:

Tropical splenomegaly syndrome

Plasmodium malariae

KUS

Ñ    Glomerulonephritis

Ñ    Nephrotic syndrome

Plasmodium falciparum

E&M

Ñ    Hyperpyrexia

Ñ    Metabolic acidosis

Ñ    Adrenal insufficiency

Ñ    Hypoglycaemia:

Decreased liver glycogen stores

CVS

Ñ    Shock (algid malaria)

This may be due to:

·          Dehydration

·          Haemorrhage:

Splenic rupture

Gastrointestinal haemorrhage

RS

Ñ    ARDS

GIT

Ñ    Diarrhoea

Ñ    Jaundice

KUS

Ñ    Haemoglobinuria:

Blackwater fever

Ñ    Acute tubular necrosis

HS

Ñ    Anaemia

Ñ    DIC

Ñ    Splenic rupture

CNS

Ñ    Cerebral malaria

Ñ    Cerebellar syndrome:

Post-malaria

Investigations

Fluids

Blood

Haematology

Thick films and thin films:

Ñ    Detect and type parasite

Immunology

Ñ    Immunochromatographic test (ICT) detects specific malaria surface proteins:

Distinguishes Plasmodium falciparum from others

Simple card test

Management

Cure

Drugs

Acute attack

Ñ    Chloroquine if strain is sensitive

Ñ    Other drugs:

Quinine, pyrimethamine / sulfadoxine, mefloquine, artemesinin derivatives, atovaquine/proguanil

Pyrimethamine / sulfadoxine rarely used now as resistance occurs

Severe Malaria

Either complications or parasite count > 1%

Ñ    Quinine

Ñ    Artesunate iv shown to be superior in trials in severe malaria

Ñ    Often add second drug

Doxycycline, clindamycin

Eradicate liver forms

Ñ    Primaquine:

May precipitate haemolysis in G6PD deficiency

Support

HS

Biological agents

Ñ    Blood transfusion:

If anaemic

Ñ    Exchange transfusion:

Parasitaemia >10%

KUS

Ñ    Maintain fluid balance

Nutritional support

Ñ    Treat hypoglycaemia:

Quinine may cause hypoglycaemia

Prevention

Drugs

Ñ    Prophylactic drugs for travellers

Biological agents

Mosquito eradication

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