Parasitic protozoa of human

importance :

Disease : Malaria Agent : Plasmodium 4 species

Differential pathogenicity

Vector-borne Apicomplexan inhabiting liver & blood

Malaria

• Plasmodium vivax : Most predominant and only species which extends to temperate regions. Benign tertian. Relapses.

• Plasmodium ovale : Tropical Africa, occasionally S. America and Asia. Ovale tertian. Relapses

• Plasmodium malariae : Primarily subtropical. Less frequent. Quartan.

Malaria

Plasmodium falciparum : Most pathogenic species. Entirely confined to tropics and subtropics. Clinically sharply differentiated from the other three species. Malignant tertian.

Malaria : diagnosis

• Microscopy : Blood smears : thin versus thick smears

• Differentiation from P. falciparum (medical emergency in non-immune)

• Rapid diagnostic antigen test

• Serology

• Gene amplification methods

Plasmodium vivax

Plasmodium ovale

Plasmodium malariae

Complications• Cerebral malaria

• Anemia

• Renal disease

• Blackwater fever

• Dysenteric malaria

• Algid malaria

• Hyper-reactive malarial splenomegaly (HMS)

Malaria and pregnancy

Pathogenesis• Sequestration +

cytoadherence : stage & strain-specific parasite-derived ligands

• Host secreted proteins : cytokines : TNF and interleukins

• Differential ability to infect RBCs

• RBC recognition and invasion

• Paroxysm

Epidemiology

• Transmission : characteristics of the vector

• Other forms of transmission (blood transfusion, shared needles, congenital)

• Innate resistance : red blood cell defects

• Immunity

• Control : eradication versus containment

Treatment : malaria

• Management of severe falciparum malaria

• Chloroquine-resistant P. falciparum• Chloroquine-sensitive P. falciparum or P.

vivax, P. ovale and P. malariae• Severe falciparum chemotherapy• Chemotherapy for P. vivax and P. ovale• Chemotherapy for P. malariae

Prevention and Control

• Malaria control strategy• Early diagnosis &

treatment

• Selective & sustainable prevention against parasite & vector

• To detect & contain epidemics

• To reassess regularly a country’s malaria situation

• Roll back malaria campaign/WHO strategy –Note : impregnated bednets

A vaccine against malaria: a substantial step forward

V. Moorthy et al.Lancet vol. 373 April 25, 2009

Comment

Current leading recombinant pre-erythrocytic malaria vaccine candidate: RTS,S/AS02D (sporozoite antigen, CSP)