Species of Plasmodium parasites
Species of Plasmodium parasites infecting humans with malaria
Malaria is caused by a parasite that spreads to humans through the bites of infected female Anopheles mosquitoes. The Plasmodium parasites that infect people with malaria cannot survive outside of their hosts: humans and Anopheles mosquitoes.
There are more than 150 blood parasites of the genus Plasmodium. However, only five species of malaria parasites cause significant disease in humans:
- Plasmodium falciparum – the most prevalent, causes the majority of severe malaria cases and deaths.
- Plasmodium vivax – the main cause of relapsing malaria, with a blood and a liver infection causing acute and ongoing symptoms.
- Less prevalent: Plasmodium ovale, Plasmodium malariae and Plasmodium knowlesi.
What are the species of Plasmodium parasites causing malaria in humans?
- P. falciparum can lead to uncomplicated malaria, but the parasite is also responsible for the majority of severe (complicated) malaria cases and deaths globally and is the most prevalent species in sub-Saharan Africa. The other malaria parasite species are not typically as life threatening as P. falciparum.
Severe malaria is usually caused by a P. falciparum infection, and typically occurs when treatment of uncomplicated malaria is inefficacious, delayed or absent. Pregnant women in their second and third trimesters are among the most at-risk of severe malaria, as are children aged five and under, who account for around 75% of malaria-related deaths annually. Though P. vivax and P. knowlesi infections can also result in severe malaria, this occurrence is less frequent.
Visit the severe malaria hub for more about its symptoms and treatment options
- P. vivax is the second most significant parasite causing malaria (approximately 2% of all cases) and is prevalent in Southeast Asia and Latin America. P. vivax and P. ovale trigger a blood stage infection causing an acute malaria episode but have the added complication of a liver stage infection, where the parasites (hypnozoites) can lie dormant and reactivate if left untreated. This can cause relapses that may occur weeks or months after the initial infection. This makes P. vivax a particular challenge for elimination efforts, with transmission driven largely by relapse from dormant liver stages.1
For many years, P. vivax malaria was considered relatively benign. However, evidence has emerged that it can also lead to severe disease and death,2 with young children and pregnant women at highest clinical risk.3
Achieving what is referred to as ‘radical cure’ for P. vivax, that is clearing all the parasites present in the patient, involves treating both the blood and liver stages of infection.
Visit the P. vivax malaria hub to learn more about its symptoms and treatment options
- Together with P. malariae, P. vivax represents only a small percentage of global infections. P. malariae causes milder symptoms than either of the two parasites above.
- A fifth species, P. knowlesi, primarily infects primates, but has also led to human malaria, though the exact mode of transmission remains unclear.
Learn more about relapsing malaria
1. Chu CS, White NJ. “Management of relapsing Plasmodium vivax malaria” Expert Rev Anti Infect Ther. 14(10):885-900 (2016), doi: 10.1080/14787210.2016. 1220304
2. Price RN et al. “Vivax malaria: neglected and not benign” Am J Trop Med Hyg. 77(6 Suppl):79–87 (2007), PMCID: PMC2653940
3. Phyo AP et al. “Clinical impact of vivax malaria: A collection review” PLoS Med. 19(1): e1003890 (2022), doi: 10.1371/journal. pmed.1003890 Fernando D et al. “Cognitive performance at school entry of children living in malariaendemic areas of Sri Lanka” Trans R Soc Trop Med Hyg. 97(2):161-5 (2003), doi: 10.1016/s0035- 9203(03)90107-6
