Malaria is an infectious disease caused by a protozoan parasite, Plasmodium. It is most often transmitted by the bite of female Anopheles mosquitoes. Fortunately, the disease is largely preventable and curable. While there are five types of malaria parasites, only two are dangerous to humans. In the year 2020, nearly half of the world’s population was at risk. While most cases of malaria are found in sub-Saharan Africa, other WHO regions report significant numbers of cases.
Two main types of malaria are caused by P. vivax and P. ovale. The latter is more likely to cause a relapse of malaria. The sporozoites produced by the latter may lie dormant in the liver for months or years before they cause symptoms. Those with an immune-compromised state are particularly susceptible to relapses. This makes it essential to find a doctor as soon as symptoms appear.
Plasmodium parasites are transmitted to humans by female Anopheles mosquitoes. The female Anopheles mosquito feeds on human blood and transmits the parasites to her next victim. Once in the host’s bloodstream, the parasites multiply inside red blood cells and then invade the liver. The invading red blood cells then rupture, allowing the parasite to multiply. The cycle of invading red blood cells repeats itself, causing the disease symptoms.
The PfRh4 gene is located in the surface of the parasite. This gene can be switched on and off to protect the host from its immune response. The switchover of the gene is called epigenetic regulation. This discovery has a profound impact on our understanding of malaria. In some cases, a person’s immune system may be unable to recognize the presence of the parasites in their blood, causing malaria.