Plasmodium Life Cycle: Diagram, Causes, Symptoms, Treatment
Plasmodium is a genus of parasitic protozoans that fall under the class Aconoidasida, the sporozoan subclass Coccidia, and the family Apicomplexa. Plasmodium infects red blood cells in mammals, e.g., humans, birds, and reptiles. A plasmodium species called P. knowlesi causes Malaria. Malaria develops when an infected female Anopheles mosquito bites a human or any other mammal. Other Plasmodium species known to spread malaria include P. vivax, P. ovale, and P. malariae. This protozoan disease is of great importance in the study of human health and disease due to its widespread impact.
This Story also Contains
- Understanding Plasmodium
- Hosts in Plasmodium Life Cycle
- Life Cycle of Plasmodium
- Plasmodium Life Cycle Diagram
- Plasmodium Life Cycle: Stages, Location, and Duration
- Symptoms of Malaria
- Diagnosis and Treatment:
- Prevention and Control of Malaria
- MCQs on Plasmodium Life Cycle
- Frequently Asked Questions (FAQs)
- Recommended Video on Plasmodium Life Cycle
Malaria is still prevalent in many parts of the world and continues to be a cause of death for millions of people each year. It is more common in tropical and subtropical areas of the world, especially Sub-Saharan Africa, Asia and Latin America. The protozoan disease primarily affects vulnerable populations like children and pregnant women. Understanding the life cycle is crucial for developing effective treatments and preventive measures.
Understanding Plasmodium
The Plasmodium species is not scarce and most of it affects reptiles, birds and mammals. The species infecting humans are mainly familiar with malaria. The stages of the parasite are sporozoites, merozoites, trophozoites and gametocytes. These stages also exhibit specific distinctive features, particularly the shape, size and ability to be stained.
Species Differences:
P. falciparum: It causes severe malaria, multiplies faster, and has complications most of the time.
P. vivax: P: falciparum malaria, responsible for relapses because of latency in the liver stages known as hypnozoites.
P. ovale: Unlike P. vivax, but less frequently.
P. malariae: Can cause chronic infections with the likelihood of later effects.
P. knowlesi: An emerging zoonotic species of macaque that becomes a severe human malaria agent in some cases.
Commonly Asked Questions
Plasmodium is a genus of parasitic protozoa that causes malaria in humans. It's important in human health because malaria is a life-threatening disease that affects millions of people worldwide, particularly in tropical and subtropical regions. Understanding Plasmodium's life cycle is crucial for developing effective prevention and treatment strategies.
The apicoplast is a unique organelle in Plasmodium that is similar to chloroplasts in plants. Although it doesn't perform photosynthesis, the apicoplast is essential for parasite survival. It's involved in the synthesis of fatty acids, isoprenoids, and heme, which are crucial for the parasite's metabolism. The apicoplast's unique nature and importance make it an attractive target for new antimalarial drugs.
Hosts in Plasmodium Life Cycle
Plasmodium requires two hosts to complete its life cycle. One is human, which acts as the intermediate host, and female anopheles mosquitoes, which act as the definitive host.
Human Host:
Asexual Reproduction: It occurs in the human liver and erythrocytes, or red blood cells (RBCs).
Mosquito Host:
Sexual Reproduction: It occurs in the gut of female anopheles whose eggs are laid in water. This step is important for the transmission of malaria from the man vector to other men or the next generation of man vectors.
Role of Anopheles Mosquito: female Anopheles mosquitoes are considered as the primary means of malaria pathogens, plasmodium parasites are transferred in the intimacy of a blood meal.
Life Cycle of Plasmodium
The life cycle of a plasmodium is divided into different stages to better understand the process at each step.The life cycle of Plasmodium is complex and involves two hosts, humans and female Anopheles mosquitoes. It includes multiple stages such as sporozoites, merozoites, and gametocytes. These stages occur in different organs and cells of the body.
Infection in Humans
Sporozoite Stage:
Transmission: Sporozoites are in fleas, and they get to people through the sting of the infected smears.
Liver Stage (Exo-erythrocytic Cycle):
Entry: Sporozoites penetrate hepatocytes (hepatitis cells). Asexual reproduction begins in hepatocytes. After getting into the hepatocytes, the sporozoites multiply asexually. Some of the hepatocytes are destroyed and replaced by new cells. Thus transforming into new forms through asexual reproduction. Kinetoplastids are protozoa that multiply after entering the hepatocytes.
Asexual Reproduction: Schizonts are formed in the cells of the liver, and the parasites also multiply here.
Release: Schizonts then rupture, and the released forms, known as merozoites, are released into the bloodstream.
Blood Stage (Erythrocytic Cycle):
Invasion: Merozoites invade RBCs.
Trophozoite Formation: They then form ring-shaped trophozoites inside the RBCs.
Schizont Formation: The blobs called trophozoites multiply and differentiate into schizonts, which in turn rupture RBCs to liberate more merozoites.
Symptoms: Cycle of rupture and destruction of RBCs results in clinical manifestations of malaria like fever, chills and anemia.
Transmission to Mosquitoes
Gametocyte Stage:
Formation: Both male and female gametocytes are produced in the blood of human beings.
Maturation: Gametocytes get enlarged and are in a position to be taken inside the digestive tube of the mosquito.
Mosquito Stage (Sexual Reproduction in Mosquitoes): Mosquito Stage (Fertilisation and Laying Their Eggs in Water):
Ingestion: From the studies, it has been noted that female Anopheles mosquitoes that are fed with blood are infected by gametocytes.
Fertilisation: Inside the body of a mosquito, the two male and female gametocytes fertilise to form a zygote called ookinete.
Oocyst Formation: It penetrates through the gut wall and forms an oocyst in it.
Sporozoite Production: Thousands of sporozoites are produced in several sections of the oocyst.
Migration: Sporozoites enter the mosquito's salivary glands and prepare it for transmission.
Plasmodium Life Cycle Diagram
A well-labelled diagram helps in visualising the stages of Plasmodium as it moves between the human body and mosquito. It includes key organs and cells like the liver, red blood cells, and mosquito gut. The following diagrams make it easier to understand the life cycle.
Commonly Asked Questions
In the mosquito vector, Plasmodium undergoes sexual reproduction and sporogenic cycles, while in the human host, it undergoes asexual reproduction. In mosquitoes, male and female gametocytes fuse to form a zygote, which develops into an oocyst producing sporozoites. In humans, the parasite multiplies asexually in liver cells and red blood cells. This alternation between sexual and asexual reproduction is key to the parasite's genetic diversity and adaptability.
Exo-erythrocytic schizogony refers to the multiplication of Plasmodium in liver cells before it infects red blood cells. This stage is significant because it allows the parasite to multiply extensively without causing symptoms, producing thousands of merozoites from a single sporozoite. It's a crucial amplification step that sets the stage for the blood infection. In some species like P. vivax, this stage can also produce dormant forms (hypnozoites) that can cause relapses.
Plasmodium Life Cycle: Stages, Location, and Duration
Each stage of the Plasmodium life cycle occurs in a specific location, in the liver, blood, or mosquito's gut. The duration of each stage varies and is essential for the parasite's survival and transmission. Here is a table summarising the stages, location, and duration.
Stage | Location | Duration (Approximate) |
Sporozoite | Human bloodstream | Minutes |
Liver Stage (Schizogony) | Human liver cells | 6-15 days |
Blood Stage (Erythrocytic) | Human red blood cells | 48-72 hours (depending on species) |
Gametocyte Formation | Human blood | Variable |
Fertilisation | Mosquito gut | Immediate upon ingestion |
Oocyst Formation | Mosquito gut wall | 8-15 days |
Sporozoite Migration | Mosquito salivary glands | Immediate after oocyst rupture |
Symptoms of Malaria
Common symptoms of malaria include high fever, and chills. In severe cases, it can lead to complications such as anemia or organ damage. Early diagnosis and treatment are necessary to avoid serious health risks. Malaria is accompanied by subsequent symptoms:
fever,
chill,
headache,
muscle ache,
fatigue,
nausea,
vomiting,
diarrhoea
occasionally anemia.
P. Falciparum causes severe malaria that develops into complications like
Cerebral Malaria,
Severe anaemia,
Multi-Organ Dysfunction.
Commonly Asked Questions
Malaria symptoms typically occur in cycles because they coincide with the synchronized bursting of infected red blood cells during the erythrocytic cycle. This releases parasites and cellular debris into the bloodstream, triggering an immune response that causes fever, chills, and other symptoms. The cycle length varies depending on the Plasmodium species.
Rosetting is a phenomenon where infected red blood cells bind to uninfected red blood cells, forming clumps. This is particularly significant in P. falciparum infections as it can contribute to severe malaria by obstructing blood flow in small blood vessels. Rosetting can also help the parasite evade the immune system and may play a role in the development of cerebral malaria, highlighting the complex interactions between the parasite and host.
Diagnosis and Treatment:
However, malaria is diagnosed through a simple blood test by background lab technicians that doesn’t take much time. Management of malaria consists of antimalarial agents such as chloroquine, artemisinin-based combination therapy (ACT), and others depending on the Plasmodium species as well as the resistance profile of the parasite.
Commonly Asked Questions
Different Plasmodium species show preferences for invading red blood cells of different ages. For example, P. falciparum can infect red blood cells of all ages, while P. vivax prefers young red blood cells (reticulocytes). This preference influences the severity and characteristics of the infection caused by each species. Understanding these preferences is important for diagnosing and treating different types of malaria.
Artemisinin-based combination therapies (ACTs) work by rapidly reducing the number of Plasmodium parasites in the blood. Artemisinin and its derivatives are fast-acting drugs that kill parasites quickly, while the partner drug eliminates remaining parasites and provides protection against resistance development. This combination approach is more effective than single-drug treatments.
P. falciparum is considered the most dangerous Plasmodium species because it can lead to severe complications like cerebral malaria. It multiplies rapidly in the blood, can infect red blood cells of all ages, and causes infected cells to adhere to blood vessel walls, potentially blocking blood flow to vital organs. These factors contribute to its higher mortality rate compared to other Plasmodium species.
Hemozoin is a crystalline substance formed by Plasmodium as a byproduct of hemoglobin digestion. When the parasite feeds on hemoglobin in red blood cells, it releases toxic heme. To protect itself, the parasite converts heme into non-toxic hemozoin crystals. The formation of hemozoin is crucial for the parasite's survival, and its disruption is a target for some antimalarial drugs.
Plasmodium undergoes antigenic variation by changing the surface proteins it expresses on infected red blood cells. This allows the parasite to evade the host's immune response, as antibodies produced against one variant become ineffective against new variants. This constant change makes it difficult for the immune system to mount an effective long-term response, contributing to the challenge of developing natural immunity to malaria.
Prevention and Control of Malaria
Mosquito Bite Prevention: Insecticide-treated bed nets, repellents, protective clothes, curtains and ceilings treated with insecticides were used.
Antimalarial Drugs: Travel and endemic malaria preventive uses of antimalarial drugs.
Vaccines: Vaccination that can prevent malaria.
Vector Control: They include indoor residual spraying (IRS), larval source management (LSM), sweeps, and modifications of environmental conditions to eliminate or minimise mosquito breeding.
Commonly Asked Questions
Antimalarial drugs like chloroquine primarily work by interfering with the parasite's ability to detoxify heme, a byproduct of hemoglobin digestion. Plasmodium feeds on hemoglobin in red blood cells, producing toxic heme. The drug prevents the parasite from converting heme into non-toxic hemozoin, effectively poisoning the parasite.
Mosquito control measures help prevent malaria by interrupting the Plasmodium life cycle at the transmission stage. By reducing mosquito populations or preventing mosquito bites, these measures decrease the chances of infected mosquitoes transmitting the parasite to humans. This breaks the cycle and reduces the overall prevalence of malaria in a population.
The spleen plays a crucial role in malaria infection by filtering infected red blood cells from the bloodstream. It can recognize and remove infected cells, helping to control parasite levels. However, some Plasmodium species, particularly P. falciparum, have evolved mechanisms to make infected cells stick to blood vessel walls, avoiding splenic clearance.
The Duffy antigen is a protein on the surface of red blood cells that P. vivax uses as a receptor to invade the cell. Some populations, particularly those of West African descent, lack this antigen and are naturally resistant to P. vivax infection. This demonstrates how human genetic variations can influence susceptibility to specific Plasmodium species.
MCQs on Plasmodium Life Cycle
Q1. Malignant malaria caused by
Plasmodium falciparum
Plasmodium vivax
Plasmodium malaria
Plasmodium ovale
Correct answer:1) Plasmodium falciparum
Explanation:
Malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal. Malignant malaria, caused by Plasmodium falciparum, is the most severe form of the disease and can be deadly if untreated. It often leads to complications such as cerebral malaria, organ failure, and severe anaemia. Prompt diagnosis and treatment are crucial to prevent life-threatening outcomes.
Hence, the correct answer is option 1) Plasmodium falciparum.
Q2. Where will you look for the sporozoites of the malarial parasite?
Saliva of infected female anopheles mosquito
Red blood corpuscles of humans suffering from malaria
Spleen of infected humans
Salivary glands of freshly moulted female Anopheles mosquito
Correct answer: 1) Saliva of infected female anopheles mosquito
Explanation:
The life cycle of Plasmodium begins when an infected female Anopheles mosquito bites a human, injecting sporozoites into the bloodstream. These sporozoites then travel to the liver where they attack the liver cells and undergo asexual reproduction resulting in the production of merozoites. These merozoites then leave the liver and enter the bloodstream where they infect red blood cells and continue the cycle, causing the symptoms of malaria.
Hence, the correct answer is option 1) Saliva of infected female anopheles mosquito.
Q3. Where will you look for sporozoites of malarial parasite?
Saliva of infected female Anopheles mosquito
Salivary glands of freshly moulted female Anopheles mosquito
RBCs of human suffering from malaria
Spleen of infected humans
Correct answer: 1) Saliva of infected female anopheles mosquito
Explanation:
When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and undergo further development. The parasites multiply within them to form sporozoites.
Sporozoites are stored in their salivary glands. When these mosquitoes bite a human, the sporozoites are introduced into his/ her body, thereby initiating the events mentioned.
Hence, the correct answer is Option 1) Saliva of infected female Anopheles mosquito.
Also Read:
Frequently Asked Questions (FAQs)
Q1. Is Plasmodium a virus or bacterium?
Plasmodium is a protozoan parasite, not a virus or bacterium.
Q2. Is Plasmodium a mosquito?
No, Plasmodium is not a mosquito. It is a parasite transmitted by the bite of an infected female Anopheles mosquito.
Q3. What are the 4 types of malaria?
The four types of malaria are caused by Plasmodium vivax, P. falciparum, P. malariae, and P. ovale.
Q4. Is there a vaccine for malaria?
Yes, a vaccine like RTS,S/AS01 is available in some regions to help prevent malaria.
Q5. How to avoid malaria?
Malaria can be avoided by using mosquito nets, repellents, keeping surroundings clean, and taking vaccination where available.
Recommended Video on Plasmodium Life Cycle
Frequently Asked Questions (FAQs)
Gametocytes are sexual stages of Plasmodium that mature in human blood-stream and are essential for malaria transmission. On biting an infected person, female Anopheles mosquitoes take along blood gametocytes. After that, zygotes develop into ookinetes and oocysts inside the mosquito’s gut during the sexual reproduction process and finally turn into sporozoites which can infect another human being through a subsequent mosquito’s blood meal.
The hepatic stage, also known as the exo-erythrocytic cycle, in Plasmodium species lasts approximately 6–15 days. It is then that sporozoites enter liver cells to become schizonts through asexual reproduction. Thereafter, merozoites are discharged into the bloodstream when the schizonts rupture. This signals the beginning of the erythrocytic stage.
Malaria symptoms include fever, chills, headache, muscle pain, tiredness, nausea, vomiting and diarrhoea. Severe malaria due to Plasmodium falciparum can cause cerebral malaria, among others, as well as severe anaemia, respiratory distress syndrome or multi-system organ failure. The cyclical pattern of intermittent fever and rigours during malarial infections corresponds with the erythrocytic stage in the parasite's life cycle.
The female Anopheles mosquito is the definitive host of Plasmodium. In this particular host, sexual reproduction takes place. The gametocytes are ingested by the mosquito from an infected human through a bite, and in the gut, they undergo sexual reproduction. This leads to sporozoites’ formation and the subsequent movement of these cells to the salivary glands of mosquitoes, which then infect other humans.
