Plasmodium is a member involving the phylum Apicomplexa, a large group of parasitic eukaryotes. Within Apicomplexa, Plasmodium is in the order Haemosporida & family Plasmodiidae. Over two hundred species of this parasite have been described, many of which have been subdivided into 14 subgenera based on parasite morphology & host range.
Major relationships among different parasite species do not usually follow taxonomic boundaries; a few species that are morphologically similar or infect the same host become distantly related. It is a genus of unicellular eukaryotes that are obligate parasites of vertebrates & insects.
The life cycles of these parasite types involve development in the blood-feeding insect host which then injects parasites into a vertebrate host throughout a blood meal. Parasites grow within a vertebrate body tissue (often the liver) before entering the bloodstream to infect red blood cells(RBC). The ensuing destruction of the host (RBC) can result in a disease, called malaria. During this particular infection, some parasites will be found by a blood-feeding insect, continuing the life cycle.
Species of this parasite are distributed globally wherever suitable hosts are found. Insect hosts are the most frequently mosquitoes of the genera Culex & Anopheles. This parasite that causes malaria is neither a virus nor a bacterium. Vertebrate hosts are:
- Reptiles,
- Birds, &
- Mammals.
These parasites were initially identified in the later 19th century by Charles Laveran. Over the course of the 20th century, many other species were discovered in various hosts & classified.
Types Of malarial Parasite
There are some different types of this parasite, but only five types cause malaria & illness in humans.
- Falciparum ( P. falciparum)
- Malariae ( P. malariae)
- Vivax ( P. vivax)
- Ovale ( P. ovale)
- Knowlesi ( P. knowlesi)
Plasmodium falciparum
It is a unicellular protozoan parasite of humans & the deadliest species of this type that causes malaria in humans
Plasmodium malariae
It is a parasitic protozoan that causes malaria in humans. It is one of several species of these parasites that infect humans, including also Plasmodium falciparum & Plasmodium vivax, responsible for the 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 parasites.
Plasmodium vivax
It is a protozoal parasite & a human pathogen. This parasite is the most frequent & widely distributed cause of recurring malaria.
Although it is much less virulent than this type, the deadliest of the particular five human malaria parasites, P. vivax malaria attacks can lead to extreme disease & death, often due to splenomegaly.
P. vivax is carried by the female Anopheles mosquito; the males do not bite.
Plasmodium ovale
It is a species of parasitic protozoa that causes tertian malaria( longer than the two-day) in humans. It is one of several species of this type that infect humans including Plasmodium falciparum & Plasmodium vivax which are responsible for the most malarial infection. It is rare compared to these two parasites, & substantially less dangerous than P.falciparum.P. ovale
It has recently been shown by genetic methods to consist of two subspecies, P. ovale curtisi & P. ovale wallikeri.
Plasmodium knowlesi
It is a parasite that causes malaria in humans & other primates. It is found throughout Southeast Asia & is the most common cause of human malaria in Malaysia. Like other Plasmodium species, P. knowlesi has a life cycle that requires infection of a mosquito host & a warm-blooded host. The natural primate host of P. knowlesi is the long-tailed macaque; however, mosquitoes that feed on infected macaques can bite & infect humans. Infected humans can develop severe malaria, similar to that caused by Plasmodium falciparum. P. knowlesi malaria is an emerging disease first recognized in humans in 1965 but increasingly recognized as a human health burden in the 21st century.
P. knowlesi has also long been used in medical research. It was first used to cause fever as a treatment for neurosyphilis in the first half of the 20th century. Later, it became popular as a tool for studying parasite biology as well as vaccine & drug development. It readily infects the model primate the rhesus macaque, & can be grown in cell culture in human or macaque blood.
Malaria symptoms are:
- Typically fever,
- Tiredness,
- Nausea & vomiting,
- Headache.
- Muscle pain & fatigue
- Body aches
- shaking chills that can range from moderate to severe
- high fever
- diarrhea
- anemia
- Confusion
- Loss of appetite
Other signs & symptoms may include:
- Sweating
- Chest or abdominal pain
- Cough
- shivering & chills
- variation in body temperature e.g. one day high while next day normal… so on… plus minus
- Sleepless
In severe cases, it can cause
- Yellow skin,
- Bloody stools
- Kidney failure
- Seizures,
- Coma or death
Every year, approximately 219 million people are infected with malaria, & about 435,000 people die from malaria. Most of the people who die from malaria are young children in Africa,(the report in 2017 of WHO).
Scientists around the world are working to produce a vaccine to prevent malaria.
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