MALARIA

• A vector-borne infectious disease

• Caused by protozoan parasites of the genus Plasmodium

• Plasmodium falciparum and Plasmodium vivax

• P.ovale, P.malariae and P.knowlesi

• Transmitted by female Anopheles mosquitoes

• Parasites multiply within RBCs• Transmission reduced by

– preventing mosquito bites with mosquito nets– insect repellents– spraying insecticides inside houses– draining standing water where mosquitoes lay

their eggs.

SYMPTOMS• Symptoms: Anemia, fever, chills &

shivering, joint pain, nausea & vomiting, hemoglobinuria.

• If severe, coma & death.• Classical symptom

– Cyclical occurrence of sudden coldness followed by rigor, fever and sweating lasting 4-6 hours, occurring

• every 2 days in P. vivax and P. ovale infections• every 3 days for P. malariae• every 36-48 hours for P. falciparum or almost

continuously.

PATHOGENESISof malaria in humans

• 2 phases– Exoerythrocytic (hepatic)– Erythrocytic phase (RBC)

• An infected mosquito pierces a person's skin to take a blood meal

• Sporozoites in mosquito's saliva enter the bloodstream and migrate to the liver.

• Within 30 min, they infect hepatocytes• Asexual multiplication • No symptoms for 6 – 15 days• Differentiate to yield thousands of merozoites• Rupture or burst of the host cells• Merozoites escape into bloodstream• Infection of RBCs

• Sporozoites are cells that develop in the mosquito's salivary glands and enter the liver where they multiply.

• Merozoites are daughter cells of a protozoan parasite, that result from asexual reproduction.

• Some P. vivax and P. ovale• No immediate conversion of sporozoites into

merozoites• Produces hypnozoites that remain dormant for

6–12 months to as long as 3 years• After dormancy, they reactivate and produce

merozoites. • Hypnozoites are responsible for late relapses of

malaria.

VACCINE

• No vaccine currently available for malaria

• Chloroquine

• Quinine

• Amodiaquine

• Artemisinin

• Propranolol: – Blocks both Plasmodium's ability to enter red

blood cell and establish an infection, as well as parasite replication.