Malaria is one of the commonest and deadliest infectious diseases across the globe. It is also the commonest vector borne disease to be transmitted by the mosquitoes.
Malaria is a protozoal infectious diseases transmitted by vector. The causative organism is a parasite of genus Plasmodium while the vector responsible for its widespread transmission is Anopheline mosquito. The mosquito bites human beings and releases the parasite in the blood cells.
H. Walpole first used the term “mal aria” meaning, “foul air” in1740. Although in 1880 C. Laveran for the first time identified the parasites in the blood of human beings, Sir Ronald Ross was the premier scientist to discover mosquito borne malaria.
Epidemiological Factors - Malaria
They include agent, host and environmental factors.
1. Agent Factors:
Four distinct species of Plasmodium parasite are responsible for its occurrence and causation. They are:
Ø Plasmodium falciparum
Ø Plasmodium malariae
Ø Plasmodium ovale
Ø Plasmodium vivax
Parasite Life Cycle: The malarial parasite has two phases of development and growth. The asexual cycle is found in human beings and the sexual cycle, occurring in mosquito.
Communicability of Parasite: The notorious infection holds chances of communicability as long as the Plasmodium gametocytes remain mature in the blood of humans.
Incubation Period: It is the time interval between the mosquito bite and the appearance of first signs and symptoms. In malaria it is around 10 days.
2. Host Factors:
Some important host factors are listed as under are:
Ø Newborns: They are known to be resistant to malaria as they have high concentration of hemoglobin, which restrains the development of parasite, especially .P falciparum.
Ø Ethnicity: Individuals whose RBCs have “Duffy negative”( a hereditary trait) are almost resistant to the attacks of P. vivax.
Ø Pregnancy: The susceptibility to malarial infection increases during pregnancy. The infection may prove detrimental to the fetus resulting in IUD, abortion or preterm onset of labor.
Ø Occupation: more prevalent in rural areas due to agricultural practices.
3. Environmental factors
Some of the significant environmental factors accountable for the growth and development of malarial parasite are:
o Seasons: Malaria is quite common in rainy season( July to Nov)
o Temperature: Optimum temperature for proper growth of the malarial parasite is somewhere between 20-30 degree Celsius. High temperature is fatal for the parasite.
o Humidity: It is important for the viability of mosquitoes. Mosquito need relative humidity of about 60%, for their growth and viability.
o Effect of Altitude: Mosquitoes do not survive at high altitudes.
Signs & Symptoms - Malaria
Malaria is seen to mimic the clinical manifestations of various infectious diseases but some of the important signs and symptoms are:
Typically a malarial cycle comprises of following stages:
Ø Cold Stage- manifested by chills and rigors.
Ø Hot Stage- characterized by onset of high grade fever.
Ø Sweating Stage- involves profuse sweating.
Cold Stage: common symptoms are lassitude,, headache, nausea, chills associated with rigors. The stage usually lasts for 15-60 minutes.
Hot Stage: the individual feels burning and wants to shed off all clothes. The skin usually is dry and quite hot to feel and touch. This stage is for 2-6 hours and characterized by severe excruciating headache.
Sweating Stage: copious sweating is seen and fever subsides. Temperature drops to normal and skin becomes cool. The person feels relieved and often sleeps. Usually this stage last for 2-4 hours.
These three classical stages are not mandatory for the occurrence of malarial infection.
Other common symptoms include:
o Cough, running nose, and other signs of respiratory infection
o Diarrhea or dysentery
o Burning micturition and lower abdominal pain
o Skin rash or skin infections
o Painful swelling of joints
o Ear discharge