Introduction: An Overview of Malaria and Plasmodium

Malaria is a terrible infectious disease that affects people all over the world. Because it is so common in economically developing regions’ poorer countries, it poses serious clinical and economic challenges. Malaria is caused by parasitic organisms of the genus Plasmodium, which are single-celled protozoans. In addition to humans, these parasites infect a wide variety of other species. There are more than 200 formally characterized species of Plasmodium, each of which infects a distinct set of host organisms. There are only five Plasmodium species—P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi— that can infect people and cause malaria in major parts of the world. Only humans can contract the first four, but macaques naturally carry and spread P. knowlesi, the zoonotic malaria parasite that affects much of South and Southeast Asia. The mosquito is the most common insect vector for Plasmodium species that can infect vertebrate hosts. The vector is more than simply a vector; it also serves as the definitive host where Plasmodium species reproduce sexually. The next vertebrate host must acquire the parasite from the vector in order for transmission to occur. All five Plasmodium species that cause malaria in humans are transmitted only by anopheline mosquitoes, albeit the spectrum of insect species that can support the parasite’s crucial development varies by species. Due to their amazing genetic flexibility, Plasmodium species are able to rapidly adapt to changes in their environment, including the development of resistance to treatments like antimalarial drugs and a shift in host specificity. This chapter provides a selective assessment of issues related to the human malaria-causing Plasmodium species.