A recent review estimates that the global burden of the malarial parasite Plasmodium vivax, is much higher than currently reported.
According to the World Health Organization (WHO), in 2019, malaria caused more than 400,000 deaths. The majority of these deaths occurred in children under the age of 5 years. The mosquito-borne disease is widespread in tropical and subtropical regions. However, more than 90% of cases and deaths occur in Sub-Saharan Africa. The malarial parasite, Plasmodium falciparum currently causes the greatest number of deaths. However, there are three other species that can cause malaria: P. vivax, P. ovale, and P. malariae. Plasmodium vivax is the second most common cause and causes about 14.3 million cases annually. However, researchers suggest that the actual global burden of the disease is much higher than that currently reported.
Researchers Kevin Baird and Katherine Battle conducted a review of the estimated global burden of P. vivax. They published their findings in the open-access journal PLOS Medicine.
Factors Affecting Global Estimates
Unlike other malarial parasites, P. vivax can exist in the body at low levels and for longer. Its presence in the body, although causes no symptoms, makes diagnosis difficult and can spread the disease to others. Moreover, chronic infections in people repeatedly exposed to P. vivax causes brain, kidney, and circulatory system damage.
The Duffy antigen, present on the surface of red blood cells, helps P. vivax invades cells. People in Sub-Saharan Africa lack the antigen and are considered immune to infections from the parasite. However, recent studies have shown that P. vivax is still widespread in the region. Researchers believe that all these factors further complicate the global estimates. They, therefore, suggest that global burden estimates should account not only for active cases but all other factors. Moreover, as chronic infections are often missed in global estimates and cause more deaths, researchers point to the need for better diagnostic methods, treatments, and vector control strategies.
Battle KE, Baird JK (2021) The global burden of Plasmodium vivax malaria is obscure and insidious. PLoS Med 18(10): e1003799. doi.org/10.1371/journal.pmed.1003799