Malaria Symptoms, Causes


Malaria is a life threatening disease and one of the world’s biggest killers. This is a mosquito born infectious disease. Malaria is a vector borne disease caused by a protozoan parasite. In additionally, malaria can infect up to 250 million people per year. Not only that but also it can kill nearly 800,000 people per year. Therefore it can found in hundreds of different countries in the world. So, many people around the world are at a high risk of getting the infection.

There is a different view that we have to consider about this disease. There are some countries in the world that are free of malaria. Also, there are some countries where there is a high risk of malaria transmission. So when international travelers visit those malaria endemic countries, they can get the disease. So there are nearly about 10,000 such cases in each year. There are currently over 100 countries where there is a high risk of malaria transmission.

Geographical distribution

Malaria can found throughout the tropics and subtropics of Africa, Asia, and South America. But in the past, epidemics of malaria had been reported in many countries all over the world. Therefore until the 19th century, malaria was prevalent in all countries of the world. Then the vector mosquito that transmits the disease was found by various investigations. As a result of that, the disease was almost eradicated from the developed countries.

There is a special geographical area called “Malaria belt” which shows the geographical distribution of the disease. Malaria belt covers the complete part of the world, which is below 1800 meters in the altitude. This includes the areas where malaria epidemics are very common.

Geographical distribution
Geographical distribution


The female of the anopheles mosquito is the vector of human malaria. The male anopheles, however never suck blood. It can lives only on vegetable and fruit meals. The female anopheles needs at least two blood meals before laying eggs.

This disease  caused by the parasites of the Plasmodium species. Anopheles mosquitoes are responsible for transmitting these species. There are four main human parasitic species. They are,

  • Plasmodium malariae
  • Plasmodium vivax
  • Plasmodium falciparum
  • Plasmodium ovale

There are several other species of Plasmodium that cause infection in birds and animals. They are,

  • Plasmodium cyanomolgi
  • Plasmodium inui
  • Plasmodium knowlesi
  • Plasmodium gallinaceum
  • Plasmodium elongatum

Anopheles mosquito
Anopheles mosquito

Clinical Manifestations

The incubation period varies indifferent species of Plasmodium. The incubation period varies from one species to another. Incubation period is the time from the entry of parasite in to the host until they become detectable in blood.

  • Plasmodium malariae 30 days
  • Plasmodium vivax 14 days
  • Plasmodium falciparum 12 days
  • Plasmodium ovale 14 days

The parasite can detect in blood before real clinical symptoms appear. These symptoms include,

  • Severe anaemia
  • Splenomegaly, splenic rupture
  • Hepatomegaly
  • Lung involvement: cough, pulmonary oedema
  • Involvement of kidney: acute tubular necrosis
  • Involvement of brain: confusion, coma
  • Vomiting
  • Dysentery
  • Haemorrhage
  • Maternal death, abortion

Clinical Manifestations
Clinical Manifestations

Laboratory Diagnosis 

Clinical diagnosis is possible for the residents of the endemic areas and for the visitors of such areas. But some people do not show many symptoms long after exposure to parasite. Therefore, laboratory diagnosis is important to prove the presence of malaria. Malaria can transmit through blood transfusion process. Therefore malaria is considered as a “Transfusion Transmissible Infection”. The best method to demonstrate the parasite is the microscopic examination of blood smear.

  1. Blood smear test (Microscopy)
    • Finger prick samples of blood are collected on two separate slides.
    • A thick smear is made in one and a thin smear is the other.
    • Both smears are microscopically tested for parasites.
    • The various stages of parasites are easily detectable on this film.
    • Some stages of Plasmodium falciparum are difficult to detect.
    • Therefore it is important to test repeated blood smears.
    • Microscopic examination can detect almost all the positive cases.
  1. Serological tests
    • There are several serological tests to detect malaria.
    • They use serological markers like Antibody and Antigen.
    • ELISA and IFAT are highly specific tests.
  1. Dip-stick test
    • Highly sensitive method
    • Easy to operate
    • Mostly use in research procedures
  1. Nucleic acid testing-PCR

Laboratory Diagnosis of Malaria
Laboratory Diagnosis of Malaria


  1. Destruction of mosquitoes
    • It is very difficult to avoid mosquito bites completely. But it is important to reduce the mosquito bites to avoid the disease.
  1. Use of anti-mosquito nets
    • The mosquito nets should be treated with insecticides.
  1. Use of mosquito repellents
    • Frequent use of repellent on skin and in sleeping environment can reduce the risk of getting the disease.
    • The most effective repellents contain diethyltoluamide.
    • These are available in sprays, roll-one, sticks and creams.

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Prevention of Malaria
Prevention of Malaria

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