Diseases Caused by Protozoa > Malaria

Malaria is a vector-borne infectious disease caused by Plasmodium.

• The main species mentioned are P. vivax, P. ovale, P. malariae, and P. falciparum.
• P. falciparum causes the most serious form and can be fatal.

Transmission:

• The disease is transmitted by the bite of an infected female Anopheles mosquito.
• During the bite, sporozoites enter human blood circulation.
• The parasite requires two hosts, human and mosquito, to complete its life cycle.

• After entering the human body, sporozoites first multiply in the liver cells.
• They then infect red blood cells, where they multiply further and cause rupture of RBCs.
• Some stages develop into gametocytes in the blood.
• When these are taken up by a female mosquito, fertilisation occurs in its gut, forming a zygote and then an oocyst.
• The oocyst produces many sporozoites, which reach the salivary glands and infect another person during the next bite.

Plasmodium: life-cycle

Symptoms:

• Symptoms usually appear about 7 to 15 days after the bite of an infective mosquito.
• Common symptoms include fever, headache, chills, nausea, muscle pain, and shivering attacks.
• The classical feature is cyclic high fever followed by sweating and sudden shivering.
• Other signs mentioned include vomiting, convulsions, anaemia, hemoglobinuria, hepatomegaly, retinal damage, and cerebral malaria.

Fever pattern:

Cause of fever

• Rupture of infected red blood cells releases haemozoin, a toxic pigment.
• Haemozoin is responsible for chills, shivering, and recurring high fever every three to four days.

Diagnosis

• Malaria can be diagnosed by microscopic study of blood smear.
• Rapid diagnostic tests based on nucleic acid amplification techniques are also used.

Treatment

• Treatment includes artemisinin-based combination therapies (ACTs).
• Different combinations of artesunate, sulfadoxine, pyrimethamine, and other drugs are mentioned.
• Quinine, chloroquine, metakelfin, and primaquine are also listed.

Prevention and control:

• Use mosquito nets and insect repellents to prevent mosquito bites.
• Control mosquito breeding by spraying insecticides and draining stagnant water.
• Gambusia and other larvivorous fishes can be used for mosquito larval control.
• Kerosene oil may be sprinkled on large water bodies to kill larvae.
• RTS, S/AS01 is mentioned as the first vaccination developed.