Plasmodium Vivax Life Cycle Structure Transmission and Clinical Features
Plasmodium vivax is a protozoa parasite and human pathogen. Plasmodium vivax is one of the six species of malaria parasite causing recurring (Benign tertian) malaria. Plasmodium falciparum is the deadliest of the six; Plasmodium vivax is less virulent but can cause severe ailment and death due to splenomegaly (pathologically enlarged spleen). Plasmodium vivax is borne by the female Anopheles mosquito since it is the only female of the species that bite humans. In spite of the recent advancement, the protein structure of Plasmodium vivax remains unknown, though Plasmodium falciparum and Plasmodium vivax share an analogous metabolic potential, with a range of putative membrane transporters necessary for parasites.
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Morphology
There are four distinct species of plasmodium that infect humans; P. falciparum, P.vivax, P.ovale, and P.malariae. Molecular investigation revealed there could be other morphological variants. CSP gene analysis of a blood sample of a P.vivax infected person revealed the individual was infected by a species closely related to P.simiovale, a simian malaria parasite. Plasmodium vivax morphology is distinctive by infected enlarged erythrocytes, which appear like granules over the erythrocytes. These granules are caused by caveola complexities over the erythrocytes. Plasmodium vivax morphology is identical to P.ovale also. This parasite also exhibits granules on the erythrocytes, making it difficult to distinguish between the two. Plasmodium vivax morphology often has the ameboid appearance and the schizonts with more than 20 merozoites.
Pathogenicity of Plasmodium Vivax
Plasmodium vivax is now recognized as one of the prime causes of severe and fatal malaria despite its low virulent. The vivax infected blood cells of the person get deformed with apparent rareness of parasite sequestration. Severe amenity is witnessed along with recurrent hemolysis of predominant healthy erythrocytes with enhanced vulnerability. Lung injury caused by inflammation in alveolar-capillary membrane permeability. However, rare vivax related coma may occur.
A plasmodium characteristic inside the red blood cell is a double membrane, and the plasmalemma is closely applied to the cytoplasm. The structure of Plasmodium vivax contains cytoplasm made of ribonucleoproteins containing small dense particles. The double membrane of the malaria plasmodium vivax containing mitochondria has peripheral cristae and a stricter, less central region.
Plasmodium vivax life cycle diagram explains the life cycle, which s divided into two; asexual life or schizogony in men and sexual life cycle in female Anopheles mosquito. Schizogony is a process where Plasmodium vivax in man and plasmodium asexually reproduce in liver and RBC cells. A man gets infected when an infected female Anopheles mosquito with sporozoites in its salivary gland. While puncturing the skin of the man, the mosquito inserts the infected saliva into the bloodstream. The sporozoites inoculate into thousands in the host`s blood. Sporozoites are inflected forms of the parasite.
Plasmodium Vivax in Mosquitoes has Below Stages
Ingestion: When the female Anopheles mosquito sucks the blood of the infected person, the gametocytes along with RBC enter its body.
Gametogenesis: In this process, gametes are formed from gametocytes; like gametocytes, gametes are micro and macro.
Fertilization: This process is also known as syngamy, where the nucleus of the female gamete comes to lie near its receptive ones.
Ookinete: During this period zygote becomes elongated and shapes like a worm with pointed ends and motile. In the first twenty-four hours, the zygote remains motionless then starts metamorphosis.
Encystment: In this phase, Ookinete changes into a spherical shape and starts taking nutrition from the stomach wall forming a thin, supple, and permeable cyst.
Sporogony: Each oocyst enters into a stage of asexual multiplication.
Microscopic View
Plasmodium vivax under a microscope under optimal condition shows granules over the erythrocytes known as Schuffner's dot. P.vivax rings have large chromatin dots, and cytoplasm can become ameboid as they develop. The trophozoite stage of Plasmodium vivax exhibits large chromatin dots with fine yellowish pigment. The in-ring stage of plasmodium vivax is often thin and delicate. The ring may have one or more chromatin dots found in the periphery of the RBC cells.
P.vivax is borne by at least seventy-one mosquito species. Many vivax vectors thrive in temperate climates extending up to the north as Finland. Some species prefer to bite in the daytime and outdoor, negating the effectiveness of mosquito repellent and bed nets. As some key vector species are yet to be grown and studied at the laboratory, the effectiveness of insecticide on these vectors is unqualified. Unlike P. falciparum, P.vivax can infect the bloodstream at sexual stage parasites.
Hence, the article has covered all the vital details regarding Plasmodium Vivax.
FAQs on Plasmodium Vivax and Its Role in Malaria Infection
1. What is Plasmodium vivax?
Plasmodium vivax is a protozoan parasite that causes vivax malaria, a widespread form of human malaria. It belongs to the genus Plasmodium and is transmitted by the bite of infected Anopheles mosquitoes.
- It primarily infects red blood cells (RBCs).
- It is common in Asia, Latin America, and parts of Africa.
- It is known for causing recurrent malaria due to dormant liver stages.
2. How is Plasmodium vivax transmitted to humans?
Plasmodium vivax is transmitted to humans through the bite of an infected female Anopheles mosquito. During a blood meal, the mosquito injects sporozoites into the bloodstream.
- Sporozoites travel to the liver and infect hepatocytes.
- They multiply and later infect red blood cells.
- Transmission can also rarely occur via blood transfusion.
3. What is the life cycle of Plasmodium vivax?
The life cycle of Plasmodium vivax involves two hosts: humans (asexual stage) and the Anopheles mosquito (sexual stage). It alternates between liver and blood stages in humans.
- Sporozoite stage: Enters human blood and infects the liver.
- Schizont stage: Multiplies in liver cells and releases merozoites.
- Erythrocytic cycle: Merozoites infect RBCs and multiply.
- Gametocyte stage: Taken up by mosquito during blood meal.
- Sporogony: Sexual reproduction occurs in mosquito gut.
4. What are hypnozoites in Plasmodium vivax?
Hypnozoites are dormant liver-stage forms of Plasmodium vivax that can reactivate weeks or months after initial infection. They are responsible for malaria relapse.
- They remain inactive inside hepatocytes.
- They do not cause symptoms while dormant.
- Reactivation leads to new blood-stage infection.
5. What are the symptoms of Plasmodium vivax malaria?
The symptoms of Plasmodium vivax malaria include cyclical fever, chills, and sweating due to rupture of infected red blood cells. The fever typically follows a 48-hour cycle.
- High fever with shaking chills
- Headache and muscle pain
- Anemia due to RBC destruction
- Enlarged spleen (splenomegaly)
6. How does Plasmodium vivax infect red blood cells?
Plasmodium vivax infects red blood cells by invading young RBCs called reticulocytes using specific surface proteins. After invasion, it multiplies inside the cell.
- The parasite enters the RBC and forms a trophozoite.
- It develops into a schizont and produces merozoites.
- RBC rupture releases merozoites, causing fever.
7. What is the difference between Plasmodium vivax and Plasmodium falciparum?
The main difference between Plasmodium vivax and Plasmodium falciparum is that P. vivax causes relapsing malaria due to hypnozoites, while P. falciparum causes more severe and potentially fatal malaria.
- P. vivax: Infects reticulocytes and forms hypnozoites.
- P. falciparum: Infects RBCs of all ages and causes severe complications.
- P. falciparum is more associated with cerebral malaria.
8. Where is Plasmodium vivax commonly found?
Plasmodium vivax is commonly found in tropical and subtropical regions, especially in Asia, Latin America, and parts of the Middle East. It is less common in most of sub-Saharan Africa.
- High prevalence in South and Southeast Asia
- Common in Central and South America
- Limited in Africa due to Duffy-negative blood groups
9. Why does Plasmodium vivax cause recurring malaria?
Plasmodium vivax causes recurring malaria because of dormant liver stages called hypnozoites that reactivate after the initial infection. This leads to relapse without a new mosquito bite.
- Hypnozoites remain inactive in the liver.
- They reactivate weeks or months later.
- New merozoites enter the bloodstream and infect RBCs again.
10. How is Plasmodium vivax diagnosed in the laboratory?
Plasmodium vivax is diagnosed primarily by microscopic examination of Giemsa-stained blood smears. The parasite stages can be seen inside red blood cells.
- Thick smear detects presence of parasites.
- Thin smear helps identify species.
- Rapid diagnostic tests (RDTs) detect malaria antigens.
