What is Malaria Disease?
Malaria is a life-threatening disease that is transmitted through the bite of an infected female Anopheles mosquito. Infected mosquitoes carry the Plasmodium parasite (the malarial parasite/ the causative agent of malaria). When this mosquito bites a human being, the parasite is released into its bloodstream.
Once the parasites are inside the human body, they travel to the liver, where they mature. After several days, the mature parasites enter the bloodstream and begin to infect red blood corpuscles or RBCs
How Malaria Enters the Body?
Within 48-72 hours, the parasites inside the red blood cells multiply, which causes the infected cells to burst open. The parasites continue to infect red blood cells, leading to symptoms that occur in cycles that last two to three days at a time.
Malaria is generally found in tropical and subtropical climates where the parasites can survive and thrive. The World Health Organization (WHO) Trusted Source reports state that in 2016, there were an estimated 216 million cases of malaria across 91 countries.
What Causes Malaria?
Malaria is caused by the female anopheles mosquito, which carries the plasmodium protozoa responsible for the disease.
There are four types of the malarial parasite that can infect humans:
Plasmodium Vivax
P. Ovale
P. Malaria
P. Falciparum.
P. falciparum causes a severe form of the disease and those who contract this form of malaria have a higher risk of death. An infected mother can also pass the disease to the fetus in the womb. This condition is known as congenital malaria.
What are the Symptoms of Malaria? / Malaria Symptoms
In the uncomplicated forms, which last 6-10 hours and recur every second day the general malaria disease symptoms are:
A sensation of cold with shivering
Fever, headaches and vomiting
Seizures can be observed in younger people with the disease
Sweats and then a return to normal temperature with fatigue
In the Severe form of Malaria, the Symptoms are:
Fever and chills
Deep breathing and respiratory distress
Abnormal bleeding and signs of anaemia
Impaired consciousness
Multiple convulsions
Clinical jaundice
Stages of Malaria Fever
Malaria fever has the following characteristics; chills, fever, rigor followed by sweating, called as the cold stage, the hot stage and sweating stage respectively.
The first cold stage lasts 15-60 minutes and is characterised by a feeling of cold and shivering.
The cold stage is followed by the hot stage, with fever from 39-41.5°C, lasting 2-6 hours, also associated with flushed and dry skin, headaches, nausea and vomiting.
At the end of the cold stage, the fever drops rapidly and the patient sweats profusely over a period of 2-4 hours.
Malaria Mode of Infection
The mode of infection in malaria occurs through the following cycle:
A female anopheles mosquito becomes infected by feeding on a person who has malaria.
The mosquito becomes the carrier of the parasite and it then transmits into a human body when the carrier mosquito bites a human
The parasite enters the body and travels to the liver, where it matures. (it can lie dormant up to a year)
When the parasites mature, they leave the liver and infect the RBCs of the bloodstream. (the symptoms start showing at this stage)
The cycle continues when an uninfected mosquito bites an infected person.
Other Modes of Transmission are:
From mother to the unborn child.
Through blood transfusion
Usage of shared syringes or needles
Malaria Life Cycle (Life Cycle of Malarial Parasite)
The complete development of the malarial parasite takes place in two different hosts; humans and mosquitoes.
The malarial parasite, plasmodium, exists in the form of a motile sporozoite. The female Anopheles mosquito, which is the vector of malaria, transmits the sporozoites into the hosts.
It is inside the mosquito’s body that the actual development and maturing of the plasmodium parasite takes place. The parasitic cells that are produced in the human body reach the intestine of the mosquito. Here, the male and female cells of the parasite fertilise each other to lead to the formation of a sporozoite.
After maturing, the sporozoite breaks out of the mosquito’s intestine and migrates to the salivary glands. When an infected mosquito bites a human, the sporozoites are transmitted into the bloodstream through the mosquito’s saliva.
Then they travel via the blood and accumulate in the liver. These parasites multiply within the liver and mature by damaging the liver and rupturing the blood cells in the body.
The parasites reproduce asexually in the RBCs, causing lysis of the cells and releasing more parasites to infect more cells. The rupture of red blood cells by the malaria parasite releases a toxin called haemozoin which causes the infected to experience a condition known as the chills and eventually one of the causes of malaria fever.
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Prevention of Malaria
Vector Control: Vector control is an effective way of preventing and reducing malaria transmission. There are two forms of vector control:
Insecticide Treated Mosquito Nets: Sleeping under/inside an insecticide-treated net can reduce contact with mosquitos. It acts as a physical barrier and the insecticide also keeps other harmful insects away.
Indoor Spraying With Residual Insecticides: This method can rapidly reduce malaria transmission. A particular insecticide is sprayed within a housing structure once or twice a year. This results in a significant increase in protection from the disease for the community.
Antimalarial Drugs: Antimalarial drugs can also be used to prevent malaria. For travellers, the disease can be prevented through chemoprophylaxis, which acts by suppressing the blood stage of malaria infections, thereby preventing malaria disease.
For women who are pregnant and are living in moderate-to-high transmission areas, WHO recommends intermittent preventive treatment with sulfadoxine-pyrimethamine at each scheduled antenatal visit after the first trimester.
For infants who live in high-transmission areas of Africa, 3 doses of intermittent preventive treatment with sulfadoxine-pyrimethamine are recommended, delivered alongside routine vaccinations.
FAQs on Common Diseases in Humans - Malaria
1. What is malaria and which parasite is responsible for causing it?
Malaria is a life-threatening disease caused by a protozoan parasite of the genus Plasmodium. It is transmitted to humans through the bites of infected female Anopheles mosquitoes. While several species of Plasmodium can infect humans, the most dangerous is Plasmodium falciparum due to its potential to cause severe and fatal complications.
2. What are the primary symptoms of a malaria infection?
The main symptoms of malaria typically appear 10-15 days after the infective mosquito bite. The classic symptoms include:
- A cyclical pattern of high fever, chills, and sweating.
- Severe headaches and muscle pain.
- Nausea, vomiting, and fatigue.
- In severe cases caused by P. falciparum, it can lead to anaemia, respiratory distress, and cerebral malaria.
3. Which mosquito transmits malaria, and why is only the female a vector?
Malaria is transmitted exclusively by the female Anopheles mosquito. This is because only the female mosquito requires a blood meal to obtain the necessary proteins for egg development. Male mosquitoes, in contrast, feed on plant nectars and do not bite humans or animals, thus playing no role in transmitting the disease.
4. Can you explain the life cycle of the malarial parasite, Plasmodium, in humans and mosquitoes?
The life cycle of Plasmodium involves two hosts. When an infected female Anopheles bites a human, it injects sporozoites into the bloodstream. The parasites first travel to the liver, where they multiply asexually. They then rupture the liver cells and invade Red Blood Cells (RBCs), continuing their asexual reproduction. This leads to the rupture of RBCs and the release of a toxin called hemozoin, causing fever and chills. Some parasites develop into gametocytes (sexual stages). When a mosquito bites an infected person, it ingests these gametocytes, which then fertilise and develop in the mosquito's gut, eventually migrating to its salivary glands as sporozoites, ready to infect another human.
5. What causes the characteristic cycle of chills and high fever in malaria patients?
The classic cyclical fever in malaria is caused by the synchronised rupture of infected Red Blood Cells (RBCs). As the Plasmodium parasite multiplies inside the RBCs, they eventually burst to release new parasites. This rupture also releases a toxic substance called hemozoin into the bloodstream. The human immune system reacts strongly to hemozoin, triggering the sudden chills and high fever that are hallmarks of the disease.
6. What are the most effective ways to prevent malaria?
Prevention of malaria, as per the CBSE/NCERT syllabus for the 2025-26 session, focuses on vector control and avoiding mosquito bites. Key methods include:
- Using insecticide-treated mosquito nets (ITNs) while sleeping.
- Spraying insecticides like DDT in residential areas to kill mosquitoes.
- Eliminating mosquito breeding grounds by draining stagnant water in and around homes.
- Introducing larvivorous fish like Gambusia into ponds to feed on mosquito larvae.
- Wearing protective clothing and using mosquito repellents on exposed skin.
7. How is malaria diagnosed and what are the standard treatments?
Malaria is diagnosed primarily through a parasite-based diagnostic test. This involves either microscopic examination of a blood smear to identify the parasite or using a Rapid Diagnostic Test (RDT) that detects parasite antigens. Early diagnosis is crucial. According to WHO guidelines, the most effective treatment for P. falciparum malaria is Artemisinin-based Combination Therapy (ACT). Other antimalarial drugs like chloroquine may be used for different species of Plasmodium.
8. Why does malaria cause recurring fevers in a predictable cycle?
The predictable cycle of fever (e.g., every 48 or 72 hours) is a direct reflection of the asexual reproductive cycle of the specific Plasmodium species. For example, Plasmodium vivax has a 48-hour cycle. The parasites inside the Red Blood Cells mature and rupture in a synchronised manner. This mass rupture releases hemozoin and new merozoites all at once, triggering an intense immune response and fever at regular intervals, which corresponds to the length of the parasite's developmental cycle in the blood.
9. What is the difference between the various species of Plasmodium that infect humans?
The four main species of Plasmodium that infect humans are P. falciparum, P. vivax, P. malariae, and P. ovale. The key differences lie in their severity, fever cycle, and geographical distribution. P. falciparum is the most deadly, causing severe anaemia and cerebral malaria, with an irregular fever pattern. P. vivax is less severe but can remain dormant in the liver, causing relapses. P. malariae causes a quartan fever (every 72 hours), while P. vivax and P. ovale typically cause a tertian fever (every 48 hours).
10. How does the Plasmodium parasite manage to evade the human body's immune response?
The Plasmodium parasite is highly effective at evading the human immune system through several mechanisms. Firstly, it spends its initial stage hiding and multiplying within liver cells, where it is shielded from immune attack. Once in the bloodstream, it resides inside Red Blood Cells, which lack the MHC-I molecules needed to signal an infection to immune cells. Furthermore, P. falciparum can change the proteins on the surface of infected RBCs, a process called antigenic variation, which helps it avoid recognition by the host's antibodies.
