**Abstract**

Malaria is a leading public health problem in tropical and subtropical countries of the world. In 2019, there were an estimated 229 million malaria cases and 409, 000 deaths due malaria in the world. The objective of this chapter is to discuss about the different Plasmodium parasites that cause human malaria. In addition, the chapter discusses about antimalarial drugs resistance. Human malaria is caused by five *Plasmodium* species, namely *P. falciparum*, *P. malariae*, *P. vivax*, *P. ovale* and *P. knowlesi*. In addition to these parasites, malaria in humans may also arise from zoonotic malaria parasites, which includes *P. inui* and *P. cynomolgi.* The plasmodium life cycle involves vertebrate host and a mosquito vector. The malaria parasites differ in their epidemiology, virulence and drug resistance pattern*. P. falciparum is* the deadliest malaria parasite that causes human malaria. *P. falciparum* accounted for nearly all malarial deaths in 2018. One of the major challenges to control malaria is the emergence and spread of antimalarial drug-resistant Plasmodium parasites. The *P. vivax* and *P. falciparum* have already developed resistance against convectional antimalarial drugs such as chloroquine, sulfadoxine-pyrimethamine, and atovaquone. Chloroquine-resistance is connected with mutations in pfcr. Resistance to Sulfadoxine and pyrimethamine is associated with multiple mutations in pfdhps and pfdhfr genes. In response to the evolution of drug resistance *Plasmodium* parasites, artemisinin-based combination therapies (ACTs) have been used for the treatment of uncomplicated falciparum malaria since the beginning of 21th century. However, artemisinin resistant *P. falciparum* strains have been recently observed in different parts of the world, which indicates the possibility of the spread of artemisinin resistance to all over the world. Therefore, novel antimalarial drugs have to be searched so as to replace the ACTs if Plasmodium parasites develop resistance to ACTs in the future.

**Keywords:** Malaria, Plasmodium species, antimalarial drug resistance

### **1. Introduction**

Malaria is a leading public health problem in tropical and subtropical countries of the world. The disease is caused by Plasmodium parasites that are transmitted by the bites of infected female Anopheles mosquitoes. In 2019, there were an estimated 229 million malaria cases and 409, 000 deaths due the disease in the world. Children aged under 5 years are the most vulnerable group, which accounted for 67% of all malaria deaths occurred in 2019. Nearly 94% of all malaria cases in 2019 occurred in Africa [1].

In addition to its health burden, malaria has also placed a heavy economic burden in Africa. Since 2000, the average annual cost of case management alone has been estimated nearly USD 300 million in Africa [2]. One of the main challenges of controlling malaria is the evolution of drug resistant strains of Plasmodium species against available antimalarial drugs [3–5]. In this chapter, antimalarial drugs resistance has been discussed. Furthermore, the life cycle, clinical features and chemotherapy of the different species of human malaria parasites have been discussed.
