It is the most destructive disease for man caused by protozoa. Malaria is widespread in the tropics and subtropics and also in certain areas of the temperate zones.
Malaria was earlier thought to be caused by foul gases emanating from marshes, hence the disease was named malaria (Italian, mala = bad, aria = air).
The term malaria was given by Maculoch (1837).
A French army doctor Charles Laveran (1880) discovered the malaria parasite (Plasmodium vivax and P. malariae) in the RBC of a malaria patient.
Stephens discovered P. ovale and Welch discovered P. falciparum. Lancisi suspected that malaria occurs where mosquitoes are found.
Richard Pfeiffer (1892) explained that some blood-sucking insects are involved in the transmission of malaria.
Scottish doctor Patrick Manson (1894) suggested that mosquito has some role in the transmission of malaria.
A doctor in the Indian Army Sir Ronald Ross (1897) established a relationship between mosquitoes and malaria.
On 29th August 1897 Ronald Ross discovered the oocysts of Plasmodium on the stomach of a female Anopheles mosquito.
Hence 29th August is observed as Mosquito Day.
For his valuable discovery, Ronald Ross was awarded the Noble Prize of Medicine in 1902.
The life history of the malaria parasite in female Anopheles mosquitoes was studied by B. Grassi (1917), A. Bignami and G. Bastianelli.
Erythrocytic schizogony in the RBC of man was studied by Golgi (1885).
E. Shortt (1948) reported the development of the malaria parasite in the liver of man.
The detailed monograph of malarial parasites was written in 1996 by P.C.C. Garnham and their fine structure has been reviewed by M. Rudzinska (1969).
Causes of malaria
Malaria is a common tropical disease caused by protozoa Plasmodium through the bite of a female Anopheles mosquito.
There are mainly four types of Plasmodium infection causing malaria as follows:
- Plasmodium falciparum (Malignant tertian malaria)
- Plasmodium vivax (Benign tertian malaria)
- Plasmodium malariae (Quartan malaria)
- Plasmodium ovale (Mild tertian malaria)
The life cycle of Plasmodium
When an infected mosquito bites an individual, its saliva, rich in parasites (sporozoites) is injected. sporozoites are infectious phage is plasmodium.
The sporozoites enter the circulation and then the liver known as the pre-erythrocytic phase. It multiplies in the liver cells forming merozoites.
After 5-9 days, the merozoites enter the red blood cells known as the erythrocytic phase forming trophozoites which subsequently mature to become schizonts.
The erythrocytic merozoites are discharged into the bloodstream when the red cells degenerate. When RBCs degenerate Hemoglobins dissociate into Hemozoin. The formation of Hemozoin causes a shivering fever. This results in an attack of malarial fever.
The red cells are destroyed by the spleen which enlarges and some of the merozoites continue to develop in the liver (exo-erythrocytic phase) causing a relapse.
This phase is absent in the life cycle of P. falciparum.
Some of the merozoites for unknown reasons do not form schizonts but develop into male and female gametocytes.
During the mosquito bite, these gametocytes are ingested.
They fertilize in the mosquito’s stomach and develop into sporozoites which localize in the salivary glands of the mosquito.
These sporozoites enter the human bloodstream on a subsequent mosquito bite and thus complete the cycle.
Abdominal pain, nausea, dry cough and malaise. Rarely it may be acute and with fever and chills.
In the early stage, fever may be persistent for several days but soon it develops into a synchronous periodicity.
A classical attack of fever has a chill, rise in temperature to 40-41QC headache and myalgia. This is followed by several hours of profuse sweating and fall in temperature.
In vivax and ovale malaria these paroxysms occur every 48 hours (benign tertian) whereas, in malariae, it occurs every 72 hours (quartan).
In falciparum malaria, the temperature is usually persistently elevated or may progress to a 48-hour cycle (malignant tertian malaria).
These cycles may be repeated in the case of benign tertian malaria due to the exo-erythrocytic phase.
The liver is moderately enlarged and tender. The spleen is often palpable in acute attacks. It is soft to firm and occasionally tender. Rarely jaundice may occur.
Diagnosis and treatment
Malarial parasites may be visible on the peripheral smear examination.
Malarial parasites can also be demonstrated on bone marrow examination and by splenic puncture.
Treatment of Malaria includes drugs like Daraprim, Chloroquine & Quinine (derived from the bark of Cinchona tree).