The malariae Plasmodium is a parasite belonging to the group of protozoans. This parasite is the causal agent of a disease recognized since the Greek and Roman civilizations, more than 2000 years ago.
This disease is known as malaria and it affects humans. It is transmitted by the bite of a mosquito infected with these plasmodia.
Giemsa-stained micrograph of a mature Plasmodium malariae schizont. The parasite contains 6-12 merozoites with large nuclei, and has a thick dark brown pigment.
Plasmodia have several species, such as plasmodium falciparum and plasmodium vivax, which are responsible for most infections.
Plasmodium malariae can infect several species of mosquitoes. Unlike other species, malariae can remain in a human host for long periods, and thus remain infectious to mosquitoes.
The overall incidence of infection with this species is unknown, but it is believed to be significantly lower than that for falciparum.
The infection is often asymptomatic, and severe disease is thought to be rare. However, untreated infection has been observed to lead to later complications in patients.
Although the disease is widely distributed, it is a so-called benign malaria and is not as dangerous as that caused by falciparum or vivax.
However, it causes recurrent fevers at approximately three-day intervals (quartan fever), longer than the two-day (tertiary) intervals of the other malaria parasites.
Finally, some of the merozoites transform into female and male gametes (sex cells), called macrogametocytes and microgametocytes, respectively.
In mosquitoes
When the anopheles mosquito takes blood from an infected person, the gametocytes are ingested and a process known as ex-flagellation of the microgametocyte occurs, forming up to eight mobile microgametes.
These mobile microgametes fertilize the macrogametes and a mobile ookinet is formed that travels to the gut of the mosquito, where it transforms into an oocyst.
After a period of two to three weeks, a variable number of sporozoites are produced within each oocyst.
The number of sporozoites that are produced varies with temperature and can range from hundreds to thousands.
Eventually, the oocyst ruptures and the sporozoites are released into the circulatory system (hemocele) of the mosquito.
The sporozoites are transported by the circulation to the salivary glands, from where they will be injected into the next human host through the mouth of the mosquito, thus initiating the cycle.
References
- Bruce, MC, Macheso, A., Galinski, MR, & Barnwell, JW (2007). Characterization and application of multiple genetic markers for Plasmodium malariae. Parasitology, 134 (Pt 5), 637–650.
- Collins, WE, & Jeffery, GM (2007). Plasmodium malariae: Parasite and Disease. Clinical Microbiology Reviews, 20 (4), 579–592.
- Langford, S., Douglas, NM, Lampah, DA, Simpson, JA, Kenangalem, E., Sugiarto, P., & Anstey, NM (2015). Plasmodium malariae Infection Associated with a High Burden of Anemia: A Hospital-Based Surveillance Study. PLoS Neglected Tropical Diseases, 9 (12), 1–16.
- Mohapatra, PK, Prakash, A., Bhattacharyya, DR, Goswami, BK, Ahmed, A., Sarmah, B., & Mahanta, J. (2008). Detection & molecular confirmation of a focus of Plasmodium malariae in Arunachal Pradesh, India. Indian Journal of Medical Research, 128 (July), 52–56.
- Westling, J., Yowell, CA, Majer, P., Erickson, JW, Dame, JB, & Dunn, BM (1997). Plasmodium falciparum, P. vivax, and P. malariae: A Comparison of the Active Site Properties of Plasmepsins Cloned and Expressed from Three Different Species of the Malaria Parasite. Experimental Parasitology, 87, 185–193.