Trophozoite

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A trophozoite (G. trope, nourishment + zoon, animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing Plasmodium falciparum and those of the Giardia group. [1] The complementary form of the trophozoite state is the thick-walled cyst form. They are often different from the cyst stage, which is a protective, dormant form of the protozoa. Trophozoites are often found in the host's body fluids and tissues and in many cases, they are the form of the protozoan that causes disease in the host. [2] In the protozoan, Entamoeba histolytica it invades the intestinal mucosa of its host, causing dysentery, which aid in the trophozoites traveling to the liver and leading to the production of hepatic abscesses. [3]

Contents

Life cycle stages

Malaria Lifecycle Malaria lifecycle.gif
Malaria Lifecycle

Plasmodium falciparium

The causative organism of malaria is a protozoan, Plasmodium falciparium, that is carried by the female Anopheles mosquit. [4] Malaria is recorded as the most common disease in Sub-Saharan Africa and some Asian countries with the highest number of death. [5] Studies have shown the increased prevalence of this disease since 2015. [6] This protozoan has several other subspecies, with some causing diseases in humans with over 91,000 death in 2021 from malaria (Plasmodium falciparium) alone, which is a 77% increase from 2020 as reported by the World Health Organization (WHO). [7]

Life cycle of Balantidium coli Balantidium LifeCycle.png
Life cycle of Balantidium coli

The Malaria lifecycle is divided into two phases:

  1. Human: The infected female mosquito (usually Anopheles species) bites a human and injects sporozoites into the bloodstream during a bloodmeal. [8] The sporozoites travel to the liver where they invade liver cells (hepatocytes) in the Exo-erythrocytic Cycle. [9] The sporozoites in the infected liver cells ruptures into schizonts which enter into the blood of the individual (Erythrocytic Cycle). The schizonts mature and divide asexually to form thousands of merozoites [10] in the early trophozoite phase, which cause the malaria symptoms in humans. These mature and go through sexual reproduction, known as gametogenesis to produce the gametocytes (occurring in male and female forms) [11] in the late trophozoite phase in the bloodstream that are picked up by other mosquitoes during blood meals.d [12] [13]
  2. Mosquito: The gametocytes, flagellated microgametocytes (males) and the unflagellated megagametocytes (females) are ingested during bloodmeal by mosquitoes, which then enter into the cyst phase, sporozoites and undergo a series of asexual reproduction. After a span of 10-18 days, the sporozoite moves to the mosquito's salivary gland subsequent blood meal on another human, anticoagulant saliva is injected along with the sporozoites, which then migrate to the liver, initiating a new cycle. [14]

Balantidium coli

Balantidium coli is the causative agent of balantidiasis. In the apicomplexan life cycle the trophozoite undergoes schizogony (asexual reproduction) and develops into a schizont which contains merozoites.

Giardia

The trophozoite life stage of Giardia colonizes and proliferates in the small intestine. Trophozoites develop during the course of the infection into cysts which is the infectious life stage. [15]

Related Research Articles

<span class="mw-page-title-main">Apicomplexa</span> Phylum of parasitic alveolates

The Apicomplexa are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of (non-photosynthetic) plastid called an apicoplast—with an apical complex membrane. The organelle's apical shape is an adaptation that the apicomplexan applies in penetrating a host cell.

<i>Plasmodium</i> Genus of parasitic protists that can cause malaria

Plasmodium is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of Plasmodium species involve development in a blood-feeding insect host which then injects parasites into a vertebrate host during a blood meal. Parasites grow within a vertebrate body tissue before entering the bloodstream to infect red blood cells. The ensuing destruction of host red blood cells can result in malaria. During this infection, some parasites are picked up by a blood-feeding insect, continuing the life cycle.

<i>Entamoeba histolytica</i> Anaerobic parasitic protist

Entamoeba histolytica is an anaerobic parasitic amoebozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates causing amoebiasis, E. histolytica is estimated to infect about 35-50 million people worldwide. E. histolytica infection is estimated to kill more than 55,000 people each year. Previously, it was thought that 10% of the world population was infected, but these figures predate the recognition that at least 90% of these infections were due to a second species, E. dispar. Mammals such as dogs and cats can become infected transiently, but are not thought to contribute significantly to transmission.

<span class="mw-page-title-main">Parasitology</span> Study of parasites, their hosts, and the relationship between them

Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question but by their way of life. This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell biology, bioinformatics, biochemistry, molecular biology, immunology, genetics, evolution and ecology.

<span class="mw-page-title-main">Isosporiasis</span> Human intestinal disease

Isosporiasis, also known as cystoisosporiasis, is a human intestinal disease caused by the parasite Cystoisospora belli. It is found worldwide, especially in tropical and subtropical areas. Infection often occurs in immuno-compromised individuals, notably AIDS patients, and outbreaks have been reported in institutionalized groups in the United States. The first documented case was in 1915. It is usually spread indirectly, normally through contaminated food or water (CDC.gov).

<i>Plasmodium falciparum</i> Protozoan species of malaria parasite

Plasmodium falciparum is a unicellular protozoan parasite of humans, and the deadliest species of Plasmodium that causes malaria in humans. The parasite is transmitted through the bite of a female Anopheles mosquito and causes the disease's most dangerous form, falciparum malaria. It is responsible for around 50% of all malaria cases. P. falciparum is therefore regarded as the deadliest parasite in humans. It is also associated with the development of blood cancer and is classified as a Group 2A (probable) carcinogen.

<span class="mw-page-title-main">Gametocyte</span> Eukaryotic germ stem cell

A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called spermatocytes, and female gametocytes are called oocytes.

<i>Plasmodium vivax</i> Species of single-celled organism

Plasmodium vivax is a protozoal parasite and a human pathogen. This parasite is the most frequent and widely distributed cause of recurring malaria. Although it is less virulent than Plasmodium falciparum, the deadliest of the five human malaria parasites, P. vivax malaria infections can lead to severe disease and death, often due to splenomegaly. P. vivax is carried by the female Anopheles mosquito; the males do not bite.

<i>Plasmodium ovale</i> Species of single-celled organism

Plasmodium ovale is a species of parasitic protozoon that causes tertian malaria in humans. It is one of several species of Plasmodium parasites that infect humans, including Plasmodium falciparum and Plasmodium vivax which are responsible for most cases of malaria in the world. P. ovale is rare compared to these two parasites, and substantially less dangerous than P. falciparum.

<i>Plasmodium malariae</i> Species of single-celled organism

Plasmodium malariae is a parasitic protozoan that causes malaria in humans. It is one of several species of Plasmodium parasites that infect other organisms as pathogens, also including Plasmodium falciparum and Plasmodium vivax, responsible for most malarial infection. Found worldwide, it causes a so-called "benign malaria", not nearly as dangerous as that produced by P. falciparum or P. vivax. The signs include fevers that recur at approximately three-day intervals – a quartan fever or quartan malaria – longer than the two-day (tertian) intervals of the other malarial parasite.

<i>Plasmodium knowlesi</i> Species of single-celled organism

Plasmodium knowlesi is a parasite that causes malaria in humans and other primates. It is found throughout Southeast Asia, and is the most common cause of human malaria in Malaysia. Like other Plasmodium species, P. knowlesi has a life cycle that requires infection of both a mosquito and a warm-blooded host. While the natural warm-blooded hosts of P. knowlesi are likely various Old World monkeys, humans can be infected by P. knowlesi if they are fed upon by infected mosquitoes. P. knowlesi is a eukaryote in the phylum Apicomplexa, genus Plasmodium, and subgenus Plasmodium. It is most closely related to the human parasite Plasmodium vivax as well as other Plasmodium species that infect non-human primates.

Megaloschizonts are large schizonts that produce extremely high numbers of merozoites. They are found in various species of the Phylum Apicomplexa. The Apicomplexa phylum contains several parasitic protozoans. They have a very complex life cycle that includes several stages. Megaloschizonts and the smaller schizonts are the part of the life cycle that takes place inside the infected host organism and operates as an asexually reproductive cell. Megaloschizonts appear as grey-white nodules found in the smooth muscle of major organs, such as the heart, liver, lung or spleen.

<span class="mw-page-title-main">Amoebiasis</span> Human disease caused by amoeba protists

Amoebiasis, or amoebic dysentery, is an infection of the intestines caused by a parasitic amoeba Entamoeba histolytica. Amoebiasis can be present with no, mild, or severe symptoms. Symptoms may include lethargy, loss of weight, colonic ulcerations, abdominal pain, diarrhea, or bloody diarrhea. Complications can include inflammation and ulceration of the colon with tissue death or perforation, which may result in peritonitis. Anemia may develop due to prolonged gastric bleeding.

Plasmodium fieldi is a parasite of the genus Plasmodium sub genus Plasmodium found in Malaysia. This species is related to Plasmodium ovale and Plasmodium simiovale. As in all Plasmodium species, P. fieldi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are primates.

Plasmodium vaughani is a parasite of the genus Plasmodium, and the type species of the subgenus Novyella. As in all Plasmodium species, P. vaughani has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

<span class="mw-page-title-main">Apicomplexan life cycle</span> Apicomplexa life cycle

Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is typified by a cellular variety with a distinct morphology and biochemistry.

Nycteria is a genus of protozoan parasites that belong to the phylum Apicomplexa. It is composed of vector-borne haemosporidian parasites that infect a wide range of mammals such as primates, rodents and bats. Its vertebrate hosts are bats. First described by Garnham and Heisch in 1953, Nycteria is mostly found in bat species where it feeds off the blood of their hosts and causes disease. Within the host, Nycteria develops into peculiar lobulated schizonts in parenchyma cells of the liver, similarly to the stages of Plasmodium falciparum in the liver. The vector of Nycteria has been hard to acquire and identify. Because of this, the life cycle of Nycteria still remains unknown and understudied. It has been suggested that this vector could be an arthropod other than a mosquito or the vector of most haemosporidian parasites.

Plasmodium coatneyi is a parasitic species that is an agent of malaria in nonhuman primates. P. coatneyi occurs in Southeast Asia. The natural host of this species is the rhesus macaque and crab-eating macaque, but there has been no evidence that zoonosis of P. coatneyi can occur through its vector, the female Anopheles mosquito.

<i>Plasmodium cynomolgi</i> Species of single-celled organism

Plasmodium cynomolgi is an apicomplexan parasite that infects mosquitoes and Asian Old World monkeys. In recent years, a number of natural infections of humans have also been documented. This species has been used as a model for human Plasmodium vivax because Plasmodium cynomolgi shares the same life cycle and some important biological features with P. vivax.

<span class="mw-page-title-main">Quartan fever</span> Medical condition

Quartan fever is one of the four types of malaria which can be contracted by humans.

References

  1. ↑ Yaeger RG (1996). Baron S (ed.). Protozoa: Structure, Classification, Growth, and Development. University of Texas Medical Branch at Galveston. ISBN   9780963117212.
  2. ↑ Aguirre García M, Gutiérrez-Kobeh L, López Vancell R (February 2015). "Entamoeba histolytica: adhesins and lectins in the trophozoite surface". Molecules. 20 (2): 2802–2815. doi: 10.3390/molecules20022802 . PMC   6272351 . PMID   25671365.
  3. ↑ López-Soto F, León-Sicairos N, Reyes-López M, Serrano-Luna J, Ordaz-Pichardo C, Piña-Vázquez C, et al. (December 2009). "Use and endocytosis of iron-containing proteins by Entamoeba histolytica trophozoites". Infection, Genetics and Evolution. 9 (6): 1038–1050. doi:10.1016/j.meegid.2009.05.018. PMID   19539057.
  4. ↑ White NJ, Pukrittayakamee S, Hien TT, Faiz MA, Mokuolu OA, Dondorp AM (February 2014). "Malaria". Lancet. 383 (9918): 723–735. doi:10.1016/s0140-6736(13)60024-0. PMID   23953767.
  5. ↑ "Pan American Health Organization (PAHO) Regional Office of the World Health Organization (WHO)". The Grants Register 2018. London: Palgrave Macmillan UK. 2018. p. 584. doi:10.1007/978-1-349-94186-5_904. ISBN   978-1-137-59209-5.
  6. ↑ Dhiman S (February 2019). "Are malaria elimination efforts on right track? An analysis of gains achieved and challenges ahead". Infectious Diseases of Poverty. 8 (1): 14. doi: 10.1186/s40249-019-0524-x . PMC   6375178 . PMID   30760324.
  7. ↑ Walker NF, Nadjm B, Whitty CJ (February 2014). "Malaria". Medicine. 42 (2): 100–106. doi:10.1016/j.mpmed.2013.11.011.
  8. ↑ Kooij TW, Matuschewski K (December 2007). "Triggers and tricks of Plasmodium sexual development". Current Opinion in Microbiology. 10 (6): 547–553. doi:10.1016/j.mib.2007.09.015. PMID   18006365.
  9. ↑ Mitchell CM, McLemore L, Westerberg K, Astronomo R, Smythe K, Gardella C, et al. (August 2014). "Long-term effect of depot medroxyprogesterone acetate on vaginal microbiota, epithelial thickness and HIV target cells". The Journal of Infectious Diseases. 210 (4): 651–655. doi:10.1093/infdis/jiu176. PMC   4172039 . PMID   24652495.
  10. ↑ Billker O, Lindo V, Panico M, Etienne AE, Paxton T, Dell A, et al. (March 1998). "Identification of xanthurenic acid as the putative inducer of malaria development in the mosquito". Nature. 392 (6673): 289–292. Bibcode:1998Natur.392..289B. doi:10.1038/32667. PMID   9521324. S2CID   2584314.
  11. ↑ Wipasa J, Elliott S, Xu H, Good MF (October 2002). "Immunity to asexual blood stage malaria and vaccine approaches". Immunology and Cell Biology. 80 (5): 401–414. doi: 10.1046/j.1440-1711.2002.01107.x . PMID   12225376. S2CID   24675596.
  12. ↑ Rajagopalan PK (2019-04-02). "Malaria Remains Unshaken and the Mighty Mosquito Remains Unbeaten". Journal of Communicable Diseases. 51 (1): 43–49. doi:10.24321/0019.5138.201906 (inactive 31 January 2024). ISSN   0019-5138. S2CID   134359453.{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
  13. ↑ Gazzinelli RT, Kalantari P, Fitzgerald KA, Golenbock DT (November 2014). "Innate sensing of malaria parasites". Nature Reviews. Immunology. 14 (11): 744–757. doi:10.1038/nri3742. PMID   25324127. S2CID   23050925.
  14. ↑ "Malaria: Control, Elimination, and Eradication". Human Parasitic Diseases. 8: 11–15. 2016. doi:10.4137/hpd.s16590. ISSN   1179-5700.
  15. ↑ Einarsson E, Ma'ayeh S, Svärd SG (December 2016). "An up-date on Giardia and giardiasis". Current Opinion in Microbiology. 34: 47–52. doi:10.1016/j.mib.2016.07.019. PMID   27501461.
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