Plasmodium Life Cycle

Plasmodium is a genus of parasitic protozoans. It belongs to the family Apicomplexa, class Aconoidasida, and subclass Coccidia. These parasites are known to infect red blood cells in mammals, including humans, as well as in birds and reptiles.

P. Knowles is one of the Plasmodium species that causes malaria, a disease transmitted when an infected female Anopheles mosquito bites a mammal. Other Plasmodium species causing malaria include Plasmodium Vivax, P. ovale, P. malariae, and P. knowlesi.

The Plasmodium parasite undergoes a complex life cycle involving an insect vector, the mosquito, to transmit the disease.

Plasmodium Life Cycle – Different Stages of Life

The life cycle of Plasmodium Vivax comprises three main stages: Gametocytes, Sporozoites, and Merozoites.

1. Gametocytes (Stage 1) – Male gametocytes are known as microgametocytes, and female gametocytes are called macrogametocytes. These are transmitted to humans during a mosquito bite. Inside the mosquito, these gametocytes develop into sporozoites. The male and female gametocytes mate in the mosquito’s gut, forming sporozoites after 15 to 18 days.
2. Sporozoite Stage in the Life Cycle of Plasmodium (Stage 2) – When the infected mosquito feeds on humans, it transmits sporozoites through its saliva into the human bloodstream. In the life cycle of plasmodium, this sporozoite enters liver cells, where they mature into schizonts. The schizonts eventually rupture, releasing merozoites.
3. Merozoite Stage in the Life Cycle of Plasmodium Vivax (Stage 3) – The schizonts in the liver multiply, forming merozoites, which enter the bloodstream and attack red blood cells. As they grow and multiply, they destroy the blood cells. Some merozoites develop into gametocytes, which a mosquito ingests during a blood meal, continuing the cycle. The destruction of red blood cells by merozoites releases toxins, leading to malaria symptoms like severe chills and fever in humans.

Life Cycle of Plasmodium Falciparum – Most Dangerous Human Parasite

Plasmodium falciparum, a unicellular protozoan parasite, is notorious for causing malaria, making it the deadliest among the Plasmodium species. This parasite spreads through the bite of the female Anopheles mosquito, leading to the most lethal form, falciparum malaria.

This species is estimated to cause nearly half of all malaria cases globally, marking Plasmodium falciparum as the most dangerous human parasite. It’s also associated with the development of blood malignancies.

Plasmodium falciparum evolved from the gorilla malarial parasite Laverania about 10,000 years ago. Alphonse Laveran first identified this parasite in 1880, naming it Oscillaria malariae. The discovery of its transmission through mosquitoes is credited to Ronald Ross in 1897, and Giovanni Battista Grassi in 1898 established that Anopheles mosquitoes could transmit the disease to humans.

The life cycle begins with an infected Anopheles mosquito bite, notably Anopheles gambiae, which is prevalent in Africa. Sporozoites, the infectious stage, are transferred from the mosquito’s salivary glands into the human bloodstream during feeding. Mosquito saliva contains enzymes that prevent blood clotting and minimize pain.

Typically, each infected bite carries 20–200 sporozoites. The immune system quickly clears these from circulation, but some manage to invade liver cells, propelled by actin and myosin proteins.

The World Health Organization’s World Malaria Report 2021 states there were 241 million malaria cases in 2020, with an estimated 627,000 deaths. Plasmodium falciparum is accountable for the majority of these deaths, especially in Africa, where it constitutes 95% of cases.

Children under five are especially susceptible, comprising 80% of all malaria fatalities. While Plasmodium falciparum is predominant in Sub-Saharan Africa, other less virulent species like Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae are more common in other malaria-endemic regions.

Life Cycle of Plasmodium Vivax

Similar to Plasmodium falciparum, Plasmodium vivax undergoes a complex life cycle involving human and mosquito hosts, but it is less virulent and typically causes less severe forms of malaria.

How Does the Malaria Transmission Occur?

1. Gametocyte Carrier: A person carrying gametocytes, the source of the malaria parasite.
2. Anopheles Mosquito: A suitable vector for the disease.
3. Susceptible Individual: Someone vulnerable to infection.

Incubation Period in the Life Cycle of Plasmodium

After entering the human body, sporozoites undergo development first in the liver and then in red blood cells (RBCs). The erythrocytic schizogony stage in the life cycle of plasmodium involves rapid multiplication of the parasite, eventually reaching a concentration that triggers fever.

This development phase is known as the incubation period. For P. vivax, P. ovale, and P. falciparum, it spans 10-14 days, while for P. malariae, it ranges from 18 days to 6 weeks.

What are the Signs and Symptoms of Malaria?

The main symptoms include intermittent fever, anemia, and splenic enlargement. The malarial fever typically begins in the early afternoon and consists of three stages:

• Cold Stage: Lasts 20 minutes to an hour.
• Hot Stage: Lasts 1 to 4 hours.
• Sweating Stage: Last 2 to 3 hours.

Fever patterns synchronize with the erythrocytic schizogony of the malaria parasite and vary by species:

1. a) Tertian Fever: 48-hour cycle, fever every third day.
2. b) Quartan Fever: 72-hour cycle, fever every fourth day.

What are the Treatment Options for Malaria?

1. Therapeutic (Clinical Cure): 4-aminoquinolines like chloroquine amodiaquine, and mepacrine target the early erythrocytic phases of the parasite.
2. Protective or Prophylactic: Drugs like proguanil, pyrimethamine, and trimethoprim suppress clinical symptoms by destroying the pre-erythrocytic phase in the liver and inactivating gametocytes, preventing further development in mosquitoes.
3. Synergists: Enhance the effectiveness of schizonticidal drugs. Sulphonamides and sulphones (e.g., dapsone) are often used alongside prophylactic drugs.

Fascinating facts about the Life Cycle of Plasmodium Class 12

• Plasmodium has a unique life cycle that requires two hosts to complete – a mosquito (specifically, the female Anopheles species) and a human.
• Once inside the human body, the Plasmodium parasite initially infects the liver. Here, it undergoes asexual reproduction, dramatically increasing in number. This liver phase can be asymptomatic, meaning it has no symptoms.
• The next phase involves the parasite entering red blood cells, where it continues to multiply. This phase is responsible for the symptoms of malaria, such as fever, chills, and anemia, due to the destruction of red blood cells.
• Some parasites develop into male and female forms (gametocytes), which are taken up by a mosquito during a blood meal. Inside the mosquito, these gametes mate, continuing the cycle.
• The sexual reproduction phase within the mosquito allows for genetic recombination, contributing to the genetic diversity of Plasmodium. This diversity can lead to drug resistance, making malaria challenging to treat.
• Plasmodium can change infected red blood cells’ surface proteins, helping it evade the human immune system.
• The sporozoites, the form of the parasite that infects humans through mosquito bites, are highly motile. They use a unique form of movement, known as gliding motility, to navigate through the human body to the liver.

Understanding the Life Cycle of Plasmodium Class 12 is crucial, as malaria remains a major global health challenge, particularly in tropical and subtropical regions. This knowledge is key to developing effective prevention and treatment strategies.

FAQs on Plasmodium Life Cycle

What are the stages in the life cycle of Plasmodium falciparum?

The life cycle of Plasmodium falciparum, the parasite causing malaria, involves two hosts. In humans, it starts as sporozoites entering the bloodstream, developing into the liver, and then blood-stage forms (schizonts, merozoites).

What is the life cycle of Plasmodium trophozoite?

The trophozoite stage is part of the Plasmodium life cycle, occurring in human red blood cells. After a merozoite infects a red blood cell, it matures into a trophozoite, feeding and growing. It then divides into new merozoites, which rupture the cell and infect more red blood cells.

What is the timeline of the Life Cycle of Plasmodium Class 12?

The timeline of Plasmodium in humans begins with the bite of an infected mosquito, introducing sporozoites. Within 30 minutes, they reach the liver, maturing over 5-16 days. Blood-stage parasites emerge, multiplying every 48-72 hours. Symptoms usually appear 10-15 days after the initial mosquito bite.

What is the full name of Plasmodium spp?

The full name 'Plasmodium spp.' refers to the genus Plasmodium, encompassing several species of parasites causing malaria. 'spp.' is an abbreviation for 'species pluralis,' indicating the mention of multiple species within the genus. Examples include Plasmodium falciparum and Plasmodium vivax