Malaria - Big Menace to Human Health in Tropical and Sub-tropical Regions of the World


Malaria is one of the major causes of mortality and morbidity worldwide, affecting nearly 40% of the world’s population and accounting for...

Malaria is one of the major causes of mortality and morbidity worldwide, affecting nearly 40% of the world’s population and accounting for about 3-5 million deaths and more than 500 million new cases annually. Wide spread resistance of the parasite to common and easily accessible drugs like chloroquine and insecticide resistance in the mosquito vector has made the malaria situation very alarming.


-Dr. Arvind Singh

Malaria is an infectious disease transmitted by the biting of female Anopheles mosquito. It is one of the oldest known diseases caused by a protozoan known as Plasmodium. Since Romans were of the opinion that malaria is caused by the bad air of the swamps and marshes hence they called it malaria (in Italian malaria means bad or foul air). The disease was discovered by French army surgeon named Alphonse Laveran who found that the condition is caused due to certain members of a family of protozoans parasites which enter the red blood cells. Another British doctor Patric Manson made similar observations while working in China and he also found evidence that his parasite was carried by mosquitoes and people get infected.


Symptoms of MalariaMosquitoes in large parts of India have become resistant to DDT, BHC, malathion and fenitrothion consequently the number of malaria cases is increasing and the government is forced to spend large sums of money to control mosquitoes.

Africa, Asia, South America, Central America and Asia-Pacific are the regions of the world where malaria persists as the major health problem. The condition is worst in the continent of Africa. Thus malaria is a serious menace to human health especially in tropical and sub-tropical regions of the world.

Causes of spread of Malaria:

The tropical and sub-tropical world faces greatest challenges from emerging, re-emerging and spread of malaria as a result of demographic changes, rapid urbanization, global travel and other environmental changes.

Urbanization, industrialization, migration, building of dams, construction of canals to boost the agricultural production, coal mining projects, increased use of pesticides, increased area under paddy cultivation, floods, ecological alterations, global warming etc. are the chief causes of spread and outbreak of malaria.

Urbanization and industrialization pulls the rural population for the job opportunities in the urban areas. These migrant people transmit malaria to the urban areas. Furthermore the migrant population lives in slums in urban areas as a result of which insanitary conditions are created which favour the development and spread of malaria. Studies on malaria in Kolkata city reveals a rising trend in incidence of malaria since 1970s which is basically due to urbanization, industrialization and migration.

The development of Indira Gandhi canal in Rajasthan has led to the spread of malaria in the state. Increased area under paddy cultivation in India has substantially contributed to the transmission and spread of the disease as the water logged paddy fields provide ideal breeding ground for mosquitoes.

The natural calamity, flood has also been a cause of spread and outbreak of malaria in India.

The Sardar Sarovar Water Resources Development Project in Gujarat, Bagri Dam Project in Madhya Pradesh and Konkan Railway Project in Konkan region had led to increased incidence of malaria in these projects affected areas.

Rise in Earth’s temperature due to global warming has favoured the growth and development of mosquito population thus resulting into an increase in incidence of malaria.

Ecological alteration like deforestation in Wet tropical Africa has caused several fold spread and outbreak in the incidence of malaria.

What is Plasmodium?

Plasmodium is single celled protozoan which causes malaria in human beings. The parasite was discovered by Sir Ronald Ross in 1898. There are five different species of Plasmodium causing malaria in human beings. These include Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale, Plasmodium malariae and Plasmodium knowlesi. As far as India is concerned Plasmodium vivax and Plasmodium falciparum are the species causing malaria whereas Plasmodium malariae in rare. However, Plasmodium ovale and Plasmodium knowlesi has not been reported from India so far.

The malaria caused by Plasmodium vivax, Plasmodium falciparum and Plasmodium malariae are known as Tertian malaria,Cerebral malaria and Quartarian malaria, respectively. Cerebral malaria is the most fatal form of malaria which affects the brain.

Symptoms of Malaria: 

Malarial symptoms appear about 9-14 days after the mosquito bite, although this varies with different Plasmodium species. The usual symptoms are intermittent fever with enlargement of spleen. The intermittent fever is characterized by chill and shivering accompanied by headache, nausea and body ache. The fever subsides with profuse sweating.

Extreme weakness and haemolytic anaemia are the other symptoms of the disease.

Malaria can kill by infecting and destroying red blood cells (anaemia) and by clogging the capillaries that carry blood to brain and other vital organs.

Life cycle of Plasmodium:

Malaria Transmission Cycle
The malarial parasite Plasmodium undergoes development both in human beings and in female Anopheles mosquito. The mosquito ingests human blood through a bite. This blood contains the gametocytes a stage in the life cycle of the malarial parasite. In the stomach of the mosquito, male gametocytes fertilize with female resulting into formation of a zygote. The zygote increase in size and becomes mobile; which pierces the stomach wall of the mosquito and a cyst is formed. Infective forms known as sporozoites appear in this cyst. In 7-20 days they reach the salivary glands and proboscis of the mosquito. When this infected mosquito bites human beings these sporozoites are introduced into human tissues. Sporozoites then enter the blood stream and reach the liver. In liver, the merozoites are released out of them, it is when merozoites, enter the blood, does the fever. This cycle is completed in 48 hours in case of Plasmodium vivax and Plasmodium falciparum and the same takes 72 hours in Plasmodium malariae.

Medicines prescribed for Malaria: 

Chloroquine, quinine and mepacrine are usually prescribed for the treatment of malaria. Since malarial parasites have developed resistance against chloroquine hence in such cases Sulphadoxine with Pyrimethamine is prescribed. Combinations of mefloquine, quinine with antibiotics tetracycline, doxycycline, chloroquanide are also used.

While visiting a place where malaria is endemic as a precautionary measure drug prophylaxis must be started two weeks before and continued for at least 4-6 weeks after leaving the malaria endemic area. Different doses of chloroquine, amodiaquine, sulphadoxine-pyrimethamide are prescribed.

Control of Malaria:

Since the malarial parasite is only transmitted by mosquitoes the control of malaria depends in preventing mosquitoes from biting humans and where possible the eradication of mosquitoes.

Female mosquitoes lay their eggs in stagnant water in ponds, lakes or ditches, or even in small amounts of rain-water lying in puddles, drinking trough or cans. The eggs soon hatch into larvae, which feed on the microscopic plants in the water. The larvae live at the surface of the water breathing air through a tracheal tube. Ultimately it pupates; the pupa, although it does not feed, still breathes air. Finally the pupal skin splits open and the imago emerges and flies away.

Methods of mosquito eradication are directed at each of the stages of its development. The adult insect should be attacked with pesticide sprays that are not harmful to other life forms. The breeding grounds of the mosquito should be destroyed by draining ponds, stagnant swamps, turning sluggish rivers into swiftly flowing steam, and by preventing the accumulation of water in puddles or tanks accessible to the mosquito. Marshy places should be covered with sand. Vegetation, the usual shelter for the mosquitoes around the streams should be destroyed.

Treating static water with oil-based sprays produces a film of oil on the water which suffocates the larvae and pupae by blocking their breathing tubes; the addition of pesticides to the sprays increases their effectiveness. Such spraying must include not only lakes and ponds but any accumulation of water which mosquitoes can reach, such as drains and gutters and even the small amounts collected in the old tin cans and other rubbish.

What is Sickle cell anaemia? 

In several regions of African continent where malaria is endemic, sickle cell anaemia in heterozygous state is a cultural adaptation to cope up with problem of malaria. Sickle cell anaemia is a genetic disorder in which abnormal haemoglobin is produced as a result of which red blood cells become sickle shaped and ultimately collapses. Consequently the malarial parasite parasitizing the red blood cells also die. The disease is caused by a recessive gene. Hamozygous individuals normally die early in life due to severe anaemia caused by destruction of the sickled red cells. However, heterozygous individuals who have both normal and abnormal haemoglobin and who also have mild anaemia, are naturally protected against contracting malaria as the parasite cannot survive in these distorted cells.

What is source of Artemisinin? 

Artemisia annua (an herbaceous plant belonging to Asteraceae family of flowering plants) is source of drug artemisinin which is used in treatment of cerebral malaria. The plant is native of China.

How Malaria is diagnosed? 

Malaria is diagnosed by blood test. The MP / MF tests are conducted to detect the malarial parasite in blood, MP test stands of malaria plain while the MF stands for malaria Falciparum.

What is source of Quinine? 

Cinchona calysia (a tree belonging to Rubiaceae family of flowering plant) is source of drug quinine which has been used in treatment of malaria since last 400 years. The drug is obtained from the bark of tree. Cinchona calysia is native of South America where its bark has traditionally been used as anti-pyretics.

What are the side effects of anti-malarial drugs? 

Chloroquine can cause nausea, vomiting and itching while Amodiaquine can cause serious blood disorders but rarely. Quinine can cause tinnitus, deafness or dizziness whereas Primaquine can cause abdominal pain.
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  1. Balendy Sharma10/20/2014

    Very informative and useful.

  2. Anonymous10/20/2014

    Atyant upyogi lekh, badhai.

    Vimal Kumar Sahu, Dhanbad

  3. Good article.



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TechGape: Malaria - Big Menace to Human Health in Tropical and Sub-tropical Regions of the World