Plasmodium ovale

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Plasmodium ovale trophozoits. Sciencedirect.com https://www.sciencedirect.com/topics/medicine-and-dentistry/plasmodium-ovale-malaria

Classification

Eukaryota (Domain); Apicomplexa (Phylum); Aconoidasida (Class); Haemosporida (Order); Plasmodiidae (family); Plasmodium (genus)

Species

Plasmodium ovale

Description and Significance

Plasmodium ovale is a parasite of malaria that is in red blood cells and can look normal or even a little bit enlarged, up to 1 and 1/4 times the normal size, and can be oval or round. It has hair-like or finger-like projections surrounding the structure as well, which differs from regular red blood cells. Plasmodium ovale is a blood parasite and it typically resides in human blood as the most common host. One of the dormant stages of P. ovale is when it persists in the liver of the human and can eventually relapse up to years later. This bacterium is most often found in the Sub-Saharan Africa region but there is potential for possible distribution to other areas of the world, even though it can be rare. Because the bacteria can remain dormant in the liver, it is important to understand the effects of this bacterium and the issues that can come from an infection or exposure. Be aware of mosquitoes when you are in an area that has the potential of carrying this disease, as that is the typical vector. Although rare in some areas, it is important to be familiar with the possibility of infections when traveling to these areas and get any prior vaccinations possible to prevent the spread.

Genome Structure

Plasmodium ovale is known to be circular like an oval and typically larger than a normal red blood cell about 1 1/4 times the size. Day five infections range from 28 micrometers to 60 micrometers with large nuclei, about 2 micrometers across. Nine-day infections range from 70 micrometers to 80 micrometers by 50 micrometers. It is seen to be as large, spherical, and made up of two portions, cytoplasm and nucleus. As the days continue, the parasites grow in length, width, and height, allowing them to infect more red blood cells and alter the human's internal system. These circular structures are also identifiable in the way that they have fimbriae that project outside of the normal, enlarged-looking blood cell. Although the last of the malaria species to be found, Plasmodium ovale is a dangerous infection that can differentiate into different parts of the body and remain dormant in a human's liver for up to 4 years.

Cell Structure, Metabolism and Life Cycle

The Plasmodium ovale (P. ovale) rings possess a sturdy cytoplasm and large chromatin dots. P. ovale trophozoites are compact, featuring large chromatin dots and dark-brown pigment. Mature P. ovale schizonts contain 6 to 14 merozoites with large nuclei, clustered around a mass of dark-brown pigment. P. ovale gametocytes are round to oval in shape and may nearly fill the red blood cell. The pigment in the gametocytes appears as scattered brown granules.

Plasmodium ovale relies on glycolysis to generate ATP allowing them to thrive in the red blood cells. The P. ovale takes up glucose from the host’s bloodstream and breaks it down into pyruvate, generating ATP in the process. They also break down hemoglobin from the red blood cells to obtain amino acids for protein synthesis. The toxic waste from this process can result in lactic acidosis and hypoglycemia in humans.

The Plasmodium ovale (P. ovale ) is introduced into the human host through a vector mosquito. The infected mosquito introduces a motile form of P. ovale called a sporozoite, which is carried by the blood to the liver. Once the sporozoites rapidly invade the liver, the parasites mature in approximately nine days. After this, they begin to replicate asexually into non-motile merozoites. Hundreds of merozoites are produced and released into the bloodstream where they invade reticulocytes and initiate the erythrocytic cycle. Inside erythrocytes, the P. ovale replication cycle takes 49 hours and after the erythrocyte ruptures. When the erythrocyte ruptures, 8-20 merozoites are released to infect other erythrocytes. Some of the merozoites will form gametocytes which instead remain in the blood and are taken in by the mosquito during feeding. When the gametocytes are ingested by the mosquito, they enter the mosquito's gut where fertilization occurs and mobile ookinetes are formed. The ookinete moves to the outer wall of the mosquito's gut where it develops for several weeks into an oocyst. After a period of several weeks, hundreds of sporozoites are produced in each mature oocyst. The oocyst ruptures, releasing these sporozoites, and the sporozoites are carried to the mosquito's salivary glands. When the mosquito feeds again, the sporozoite is injected into a new host through the salivary duct, starting the life cycle over again.

Ecology and Pathogenesis

Plasmodium ovale is a protozoan disease, under the malaria infectious disease category, that is transmitted from a mosquito Anopheles via a bite. Plasmodium ovale is most commonly found in tropical Western Africa. Less than 1% of cases reported were found outside of the endemic region of Western Africa. Those countries include Indonesia, the Philippines, and Papua New Guinea. Various malaria strains have been found in 107 countries and causes up to 3 million deaths per year. Plasmodium ovale is most commonly found in tropical Western Africa. Less than 1% of cases reported were found outside of the endemic region of Western Africa. Those countries include Indonesia, the Philippines, and Papua New Guinea. The ratio of Plasmodium ovale in comparison to other malaria infections is relatively low. It is recorded that 1:1000 cases of malaria are Plasmodium ovale. The severity of Plasmodium ovale is low due to the lack of cases. The disease is transmitted through the saliva of the Anopheles during a blood meal. The recorded symptoms of Plasmodium ovale include high fevers, headaches, fatigue, sweating, abdominal pain, nausea, vomiting, diarrhea, and orthostatic hypotension. The indicators of Plasmodium ovale as the specific strain of malaria are a patient presenting with a fever, rigors, and chill at reoccurring intervals. Anopheles and Plasmodium ovale have a mutualistic symbiotic relationship because both the disease and the mosquito benefit from the relationship. The Plasmodium ovale benefits from the Anopheles spreading the disease by relying on the Anopheles as its host. The Anopheles benefits because the Plasmodium ovale increases its lifespan via anti-aging transcriptomes and enhances chemoreceptor sensitivity.

References

Carr, A. L., Rinker, D. C., Dong, Y., Dimopoulos, G., & Zwiebel, L. J. (2021). Transcriptome profiles of anopheles gambiae harboring natural low-level plasmodium infection reveal adaptive advantages for the mosquito. Scientific Reports, 11(1). https://doi.org/10.1038/s41598-021-01842-x

Centers for Disease Control and Prevention. (2024, September 24). CDC - dpdx - malaria. Centers for Disease Control and Prevention. https://www.cdc.gov/dpdx/malaria/index.html

Collins, W. E., & Jeffery, G. M. (2005). Plasmodium ovale: Parasite and disease. Clinical Microbiology Reviews, 18(3), 570–581. https://doi.org/10.1128/cmr.18.3.570-581.2005

LPDx. (n.d.). Plasmodium ovale CDC. https://www.cdc.gov/dpdx/resources/pdf/benchAids/malaria/Povale_benchaidV2.pdf

Okafor, C. N., & Finnigan, N. (2023, August 14). Plasmodium ovale Malaria. National Library of Medicine, StatPearls Publishing(Internet) https://www.ncbi.nlm.nih.gov/books/NBK519021/

Schoch CL, et al. NCBI Taxonomy: a comprehensive update on curation, resources and tools. Database (Oxford). 2020: baaa062. PubMed: 32761142 PMC: PMC7408187

Author

Page authored by Mason Clark, Anna Darlington, Kara Cotton, & Hanna Elberson, students of Prof. Bradley Tolar at UNC Wilmington.