Plasmodium Definition, Life Cycle, Characteristics, Morphology, Diagram

Written by SouravBio · 11 minutes read >

Plasmodium parasite is considered the oldest known parasite in the world. In 1880, Charles Louis Alphonse Laveran first described the presence of Plasmodium parasites in the blood of malaria patients.

In the beginning, Charles Louis Alphonse Laveran called it Oscillaria malariae. Later two zoologists Ettore Marchiafava and Angelo Celli term this parasite as a member of a new genus, called Plasmodium, In 1885.

In 1886,  Camillo Golgi first noticed that there are different Plasmodium parasites which are responsible for different nakarua diseases.

Later two distinct human malaria species were identified by Giovanni Batista Grassi and Raimondo Filetti. They named it  Plasmodium vivax and Plasmodium malariae.

Plasmodium Classification

Domain: Eukaryota
(unranked): Diaphoretickes
Clade:TSAR
Clade: SAR
Infrakingdom:Alveolata
Phylum: Apicomplexa
Class: Aconoidasida
Order: Haemospororida
Genus: Plasmodium
Family: Plasmodiidae

Plasmodium Definition

Plasmodium is also known as the malaria parasite and is the genus of intracellular parasitic protozoa. They are digenetic parasites because Plasmodium are obligate parasites of insects (such as mosquitoes) and vertebrates.

The term “malaria” originated from two Italian words; “mal” which means bad, and “aria” means air.

The plasmodium parasite does not affect the infected mosquito (nor does it die from malaria). Because they don’t have red blood like others, where the parasites develop and thrive.

Plasmodium Morphology

Plasmodium Falciparum

Plasmodium Falciparum is considered as the most virulent species among the all human malaria parasites. P. Falciparum causes severe malaria (malignant malaria) with the development of irregular paroxysms and high fever and may cause death if not treated.

The diagnostic form or stage determines the morphological characteristics of Plasmodium Falciparum.

1. The Ring Form

  • Inside the erythrocytes the ring form of Plasmodium Falciparum is found.
  • It is called ring form because it looks like a ring. It contains nucleus, cytoplasm and a central vacuole.
  • The diameter of ring form is one fifth of erythrocytes and the ring form is very thin and thus delicate.
  • It contains 1 – 2 chromatins.

2. Trophozoites

  • The size of Trophozoites ranges between between 1.25 and 1.5um.
  • They contain a thin cytoplasm with a signet ring shape.
  • Trophozoites are vacuolated and have a single nucleus.

3. Schizonts

  • Schizonts are 4.5 to 5 um in diameter.
  • They capture 2-3 of a red cell.
  • They have 2 or 4 merozoites and a pigment which forms dark color during staining. A mature Schizonts contains about 30 merozoites.

4. Gametocytes 

  • Gametocytes are crescent shaped (banana-shape) and are considered as the sexual forms of the parasite.
  • The advantage of the sexual forms is the parasite contains both male and female forms which have a size about one and a half of a normal red cell.
  • They are infectious to mosquitoes.

5. Sporozoites

  • They are infectious to humans.
  • Sporozoites are 10 to 15 um in length
  • They contain a thick pellicle, a mitochondrion, a single nucleus.
  • They can move which is possible by the peripheral fibers.
  • The pellicle contains double-membrane and also has an additional layer made of subpellicular microtubules.

Plasmodium Vivax

1. Ring form

  • It has a signet ring shape.
  • Plasmodium Vivax contains a large cytoplasm with a large chromatin.
  • After maturation they form an amoeboid shape.
  • The size of Ring form is a third the diameter of red cells.

2. Trophozoites 

  • They appear as a  few dots of large chromatin with amoeboid cytoplasm as well as fine pigments (hematin) that are yellowish-brown in color.

3. Gametocytes 

  • These are round and oval in shape.
  • They contain high amounts of brown pigments which are scattered within the infected red cells.

4. Schizonts

  • They contain 12 to 24 merozoites and are large enough to fill the entire cell erythrocyte.
  • Schizonts also contain a yellowish-brown pigment.

Plasmodium Ovale

1. Ring form

  • They appear as one or two large chromatin dots as well as a sturdy/thick cytoplasm.
  • The Schuffner’s dots are formed when they are matured.

2. Trophozoites 

  • The trophozoite’s cytoplasm is sturdy with a few chromatin dots.
  • They are irregular in shape and some of them appear to be more compact.

3. Gametocytes 

  • These are round or oval in shape and large enough to fill the whole erythrocyte cell.
  • They also contain brown pigment.

4. Schizonts  

  • They contain about 6 to 14 merozoites.
  • Schizonts has a mass of dark-brown pigment which is covered by large nuclei.

Plasmodium Characteristics

  • They are unicellular eukaryotes.
  • Plasmodium are obligate parasites of vertebrates and insects.
  • They are responsible for human malaria disease.
  • They are considered the most researched genera of parasites.
  • The Plasmodium parasite is mainly found in tropic and subtropic areas.
  • Plasmodium falciparum, Plasmodium ovale, Plasmodium vivax, and Plasmodium malariae are responsible for human malaria.
  • They use Anopheline mosquito as a vector.
  • The symptoms of malaria disease are sometimes unnoticed or misdiagnosed; clinical signs include fever, chills, weakness, headache, vomiting, diarrhea, anemia, pulmonary and renal dysfunction, neurologic changes.

Plasmodium Genome

  • The complete genome sequencing of Plasmodium falciparum showed us that it contains 14 chromosomes and 5,300 genes. These genomes are responsible for dodging the host’s immunities
  • Plasmodium falciparum is considered the most common form of Plasmodium which is responsible for human malaria.
  • The average gene density is approximately 1 gene/4,338 base pairs.

Plasmodium Host

Plasmodium requires two host cells to complete their life cycle. They complete their asexual cycle within human body and the sexual cycle is within the female anopheline mosquito.

The female Anoph­eles mosquito is the definitive or primary host of Plasmodium whereas the human body is the inter­mediate or secondary host.

Except human plasmodium infects other hosts such as Monkeys (P. knowlesi and P. coatneyi),

Chickens (P. juxtanucleare), Pigeon (P. relictum), Snakes (P. wenyoni), Canaries (P. cathemerium).

Plasmodium Species

Plasmodium is the largest member of the order Haemosporidia. There are about  250 species within this genus. All of them are responsible for malaria disease in different vertebrates.

About 29 species cause infection in non-human primates; rodents outside the tropical parts of Africa are rarely affected.  Bats, porcupines, and squirrels; carnivores, insectivores, and marsupials are infected by few known species.

Here is the name of few Plasmodium Species;

Plasmodium accipiterisPlasmodium achiotensePlasmodium achromaticum
Plasmodium capraePlasmodium capistraniPlasmodium caloti
Plasmodium buteonisPlasmodium bubalisPlasmodium bucki
Plasmodium brygooiPlasmodium brumptiPlasmodium brasilianum
Plasmodium brodeniPlasmodium bouillizePlasmodium booliati
Plasmodium blacklockiPlasmodium biziuraePlasmodium bioccai
Plasmodium biguetiPlasmodium bertiiPlasmodium beltrani
Plasmodium beebeiPlasmodium beaucournuiPlasmodium basilisci
Plasmodium bambusicolaiPlasmodium billcollinsiPlasmodium azurophilum
Plasmodium balliPlasmodium billbrayiPlasmodium attenuatum

Plasmodium Cell Structure

In some ways, all the species of plasmodium differ from each other. They show the same life cycle. Anopheles mosquito injects the sporozoites with the saliva when they bite a human.

Plasmodium Diagram
Plasmodium Diagram | Image source: Wiki | Image Author: Jfbranch14
  • The size of this sporozoite is about 10 -15 µm in length and 1 µm in diameter. 
  • The sporozoites contain a thin outer membrane.
  • The subpellicular microtubules lie below the inner membrane.
  • The membrane contains 3 polar rings and the rhoptries are long, extending half the length of the body. 
  • The micronemes, convoluted elongate bodies, move forward to the anterior of the sporozoite entering a common duct with the rhoptries.
  • The posterior end contains the Mitochondria.
  • The sporozoites use the apical organelles to invade the liver cells when they enter the circulatory system.

Plasmodium life cycle

Five species of Plasmodium are responsible for human malaria such as: P. falciparum, P. malariae, P. vivax, P. knowlesi, and P. ovale.

The plasmodium parasite is transferred through the female Anopheles mosquito. When an infected female Anopheles mosquito bites a human it injects the parasite inside the bloodstream.

  • During male, the mosquito injects the small haploid sporozoites with saliva within the bloodstream.
  • Then the sporozoite immediately enters into the hepatic cells of the liver from the bloodstream.
  • There they produce merozoites by undergoing multiple asexual fission (schizogony).
  • Then the merozoites are attached and penetrate inside the erythrocytes, after being released from the hepatocytes.
  • After that, the plasmodial cell started to enlarge as a mononucleate cell known as a trophozoite.
  • The nucleus of trophozoite is divided and produces schizont, which contains 6 to 10 nuclei.
  • Then mononucleated merozoites are produced with the division of schizont.
  • These merozoites are released when the infected erythrocytes are lysed. After that these merozoites infect other erythrocytes.
  • This erythrocytic stage is cyclic and repeats approximately every 48 to 72 hours or longer, depending on the species of Plasmodium involved.
  • Then the symptoms of malaria disease such as chills, fever, and sweats are developed when the merozoites, toxins, and erythrocyte debris are released into the bloodstream.
  • Occasionally, macrogametocytes and microgametocytes are developed with the differentiation of merozoites. They do not rupture the erythrocyte.
  • When these are ingested by a mosquito during a blood meal, they develop into female and male gametes, respectively.
  • The erythrocytes are lysed and the gametes fuse to develop a diploid zygote known as the ookinete. The formation of ookinete is performed within the mosquito’s gut.
  • Then the ookinete gets attached and penetrates the mosquito’s gut wall to form an oocyst.
  • After that, the sporozoites are formed when the oocysts undergo meiosis. This process is known as sporogony. Then the sporozoites are Migrate to the salivary glands of the mosquito.
  • The cycle will repeat again when the mosquito bites another human host.
Plasmodium - malaria life cycle
Plasmodium – malaria life cycle

Plasmodium Disease/ Malaria Disease

Plasmodium parasite is responsible for the Malaria disease. There are different species of Plasmodium which are responsible for malaria in different hosts such as P. vivax, P. falciparum, P. ovale and P. malariae, P. knowlesi.

Symptoms of Malaria

Symptoms of malaria develop within 10 days to 4 weeks. The common symptoms include shaking chills that can range from moderate to severe, high fever, profuse sweating, headache, nausea, vomiting, abdominal pain, diarrhea, anemia, muscle pain, convulsions, coma, bloody stools.

Diagnosis of Malaria

  • The diagnosis of malaria can be done by observing the developing symptoms such as chills, sweats, fever, muscle pain, nausea, and vomiting which may appear within 7 to 30 days after infection.
  • The detection of malaria can be done by laboratory tests such as serology tests, PCR, and drug-resistance tests or observing the blood sample of malaria patients under a microscope.

Treatment of Malaria

The treatment procedure for malaria disease depends on several factors such as 

  • the types of parasite species.
  • the concentration of parasites within the bloodstream.
  • whether the parasite is drug resistant or not
  • the country where the parasite is located.

WHO recommended that the treatment will start within 24 hours after the development of symptoms.

For those patients, who’s malaria parasite is not identified they will be treated as they are infected with P. falciparum until the parasite is identified.

In those countries where chloroquine-resistant strains are not found, chloroquine can be used to treat P. falciparum, chloroquine.

In those countries where chloroquine resistance strain are founded, there three different types of treatment methods can be used such as;

  • a combination of atovaquone and proguanil.
  • oral quinine plus tetracycline, doxycycline, or clindamycin or
  •  3 –mefloquine

Primaquine is an effective drug P. vivax and P. ovale, it prevents the spread of the parasite into the bloodstream. Chloroquine with hydroxychloroquine can be used For P. vivax infections as a second-line alternative.

The new drug Artemisinins is the most effective agents against multi-resistant malaria strains. But they are not widely available and are very expensive.

For severe malaria, the infection can be treated with quinidine or an exchange transfusion. 

Transmission of Malaria Parasite

  • Malaria Parasite can be transmitted through the bites of female Anopheles mosquitoes.
  • It can be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. 
  • Malaria can transmit from a mother to her unborn infant.

Prevention of Malaria

  • Take prophylactic measures when travelers are going into malaria-endemic countries. Before travel and when traveling in malaria-endemic areas take Chemoprophylaxis.
  • Avoid mosquito bites by;
    • Apply insect repellent which contains 20-35% percent N,N-Diethyl-meta-toluamide (DEET) to your exposed skin.
    • When you are outside at night wear long-sleeved clothing and long pants.
    • Use a mosquito net over the bed.
    • Spray an insecticide or repellent on clothing.
    • Before going to bed Spray pyrethrin or a similar insecticide in your bedroom.

Plasmodium Examples

Plasmodium Falciparum

  • Plasmodium Falciparum are unicellular protozoan parasites that cause malaria in humans.
  • Plasmodium Falciparum considered as the deadliest species of Plasmodium and are  responsible for 50% of all malaria cases..
  • They cause falciparum malaria which is the most dangerous form of malaria disease.
  • They are classified as Group 2A carcinogen because they also help in development of blood cancer (Burkitt’s lymphoma).
  • The parasite Laverania which is found in gorillas, is the origin of Plasmodium Falciparum.

The life cycle, diagnosis, treatment, prevention, transmission of Plasmodium Falciparum is already discussed above.

Plasmodium Vivax

  • Plasmodium Vivax is responsible for recurring malaria.
  • Plasmodium Vivax is less virulent than Plasmodium falciparum.
  • They are mainly found in Asia, Latin America, and in some parts of Africa.
  • The P. vivax originated from wild chimpanzees and gorillas throughout central Africa.
  • 65% of malaria cases in Asia and South America are caused by the P. vivax.
  • The spread of Plasmodium Vivax can be done through vector control.

The life cycle, diagnosis, treatment, prevention, transmission of Plasmodium Vivax is already discussed above.

Plasmodium knowlesi

  • They are responsible for malaria disease in humans and other primates.
  • Plasmodium knowlesi is mainly found in Southeast Asia and responsible for human malaria in Malaysia.
  • They required both mosquitoes and a warm-blooded host to complete their life cycle like others.
  • In 1932, Plasmodium knowlesi was first discovered.

The life cycle, diagnosis, treatment, prevention, transmission of Plasmodium knowlesi is already discussed above.

FAQ On Plasmodium

1. Are plasmodium protists? 

Yes, Plasmodium is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects.

2. Are plasmodium heterotrophic or autotrophic?

As like Amoebae and paramecium,  plasmodium is a heterotrophic protist.

3. Are plasmodium bacteria?

No, plasmodium is a protista.

4. Can plasmodium falciparum interbreed?

No, plasmodium falciparum can’t interbreed.

5. Can plasmodium move?

Yes, plasmodium can move through a process known as the gliding motility.

6. Can plasmodium cross the placenta?

Yes, plasmodium  can be transmitted across the placenta and could result in congenital malaria

7. How does plasmodium reproduce?

They reproduced by asexual reproduction known as the exoerythrocytic cycle within the hepatocytes.

8. How plasmodium is transmitted by mosquitoes?

When an infected female Anopheles mosquito bites a human it injects the parasite inside the bloodstream.

9. How plasmodium causes malaria?

Follow the life cycle of plasmodium.

10. How plasmodium is transmitted?

Mosquito bites, blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria can transmit from a mother to her unborn infant.

11. What plasmodium causes malaria?

Five species of Plasmodium are responsible for human malaria such as: P. falciparum, P. malariae, P. vivax, P. knowlesi, and P. ovale.

12. When was plasmodium discovered?

Plasmodium parasite is considered the oldest known parasite in the world. In 1880, Charles Louis Alphonse Laveran first described the presence of Plasmodium parasites in the blood of malaria patients.

13. When was plasmodium falciparum discovered?

plasmodium falciparum originated around 10,000 years ago from the malarial parasite Laverania found in gorillas.

14. When does plasmodium reproduce asexually?

Within the hepatocytes the started their asexual reproduction known as the exoerythrocytic cycle.

15. Where plasmodium is found?

Plasmodium falciparum found in  tropical and sub-tropical areas. Plasmodium ovale is mostly found in the west coast region of Africa. Plasmodium malariae has a widespread distribution area but is fairly scattered within this area.

16. Where does plasmodium come from?

Plasmodium falciparu originated from the malarial parasite Laverania found in gorillas, Plasmodium vivax originated from the wild chimpanzees and gorillas throughout central Africa

17. Plasmodium eukaryotic or prokaryotic?

Plasmodium  are eukaryotic cells.

18. How is Plasmodium vivax transmitted?

Mosquito bites, blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria can transmit from a mother to her unborn infant.

19. What are the symptoms of Plasmodium vivax?

The symptoms are shaking chills that can range from moderate to severe, high fever, profuse sweating, headache, nausea, vomiting, abdominal pain, diarrhea, anemia, muscle pain, convulsions, coma, bloody stools.

Further Reading

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Writer and Founder of Microbiologynote.com. I am from India and my main purpose is to provide you a strong understanding of Microbiology. Microbiologynote.com shares notes related to different branches of microbiology.

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