The different types of malaria

Malaria, caused by a parasitic protozoon, Plasmodium, comes in four forms based on which type of plasmodium has caused the disease in an individual

By Dr Vasundhra Atre



The malaria plasmodium

Malaria, a disease transmitted through the bite of the female Anopheles mosquito, is rampant in more than 100 countries. Malaria is caused by a parasitic protozoon, Plasmodium, which infects red blood cells. A single bite of the mosquito injects Plasmodium parasites into blood stream of the host. There are four main strains of malaria, Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae.

The life cycles of the four types of malaria parasites are broadly similar. A female Anopheles mosquito carrying malaria-causing parasites releases the malarial parasites (called sporozoites) into the bloodstream following a mosquito bite. They migrate to the liver where they mature and release another form, the malarial merozoites into the blood stream. These merozoites can develop into male and female gametocytes that circulate in the bloodstream. When a mosquito bites an infected human the gametocytes are ingested and develop further in the gut of the mosquito, till they develop into sporozoites and invade the mosquito salivary glands; waiting for the next bite to release them into human bloodstream.

Plasmodium Falciparum (P.falciparum)

Plasmodium falciparum is the most common strain of malaria and also the deadliest. Found in Asia, Africa, the Middle East, the Pacific and South America, it is responsible for 60% of malarial infections and 90% of malarial deaths, worldwide.

  • The incubation of P. falciparum is 6 – 21 days. The fever cycle is usually 48 hours although it maybe sometimes difficult to pick these spikes. Although limited immunity develops with repeated infection of the same P. falciparum strain; it rarely develops in adults.
  • Unlike the other strains of malaria if adequately treated it should not recur.
  • If prompt treatment is not given, the progression of the disease to a more severe form can be as rapid as a few hours. It is one of the few diseases where an individual can be relatively well in the morning, have a high fever by afternoon and be dead by evening.
  • As the parasite multiplies the smaller blood vessels tend to get blocked, significantly reducing the blood flow to the major organs. This can happen in the vessels supplying the brain (cerebral malaria), the liver (malarial hepatitis) or the kidney causing renal failure.
  • Over time P. falciparum have developed wide resistance to anti-malarial medication. Newer drugs or drug combinations maybe suggested in these cases.

Plasmodium Vivax (P. vivax)

Found in Asia and Central America, with small outbreaks in West and Eastern Africa, categorized as a benign form of the disease, P. vivax is in fact the second most deadly strain of malaria. P. vivax parasites have a preference for younger red blood cells.

  • For patients who suffer traumatic rupture of the spleen, it can be fatal, as also in cases of severe anaemia, especially among malnourished and debilitated patients.
  • The incubation period is 12 – 17 days; with fever cycles of 48 hours. Recurrence of infection is common with P. vivax.
  • In some cases of the disease, immunity to some strains have been noted; probably because the mosquitoes live close to their larvae development site, recurrent victims of the disease continually receive infections of the same strain of P. vivax allowing the body to build up some immunity to that one strain. This is a limited immunity; if another strain of P. vivax infects the individual, the immunity is ineffective.
  • In some areas, resistance to anti-malarial medication has been described.

Plasmodium Malariae (P. malariae)

Found in East and West Africa, Guyana, India and South East Asia, P. malariae categorized as a benign form of the disease, have a preference for mature red blood cells.

  • The incubation period ranges from 18 – 40 days or longer depending on the strain.
  • The fever cycle occurs every 72 hours and may last for 8 -10 hours at a time.
  • While the first attack is usually very mild, a recurrence of the disease has been known to occur even after five decades.

Plasmodium Ovale (P. ovale)

More commonly encountered in Sub-Saharan Africa, it has been categorized as a benign form of the disease and has a preference for younger red blood cells.

  • The incubation period varies from 16 – 18 days or longer depending on the strain.
  • While the symptoms resemble other benign forms of the disease, it is characterized by fever spikes every 48 – 50 hours.
  • If no treatment is taken or taken inadequately the infection may last for 18 months to three years; the periods of recurrence may be lengthy between attacks.

Even the strains of malaria that are considered benign can prove deadly in a patient who is malnourished or weak. Malaria is a disease that is beatable and treatable and is better prevented rather than treated.

Picture credit: Wikipedia.org

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