CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 Malaria
Malaria is an ancient disease that continues to take a toll on human existence. It remains one of the world's greatest public health problems (Cox- Singh et al., 2008). Today, an estimated 40% of the world's population remains at risk of malaria, with 500 million cases annually, resulting in 1–2 million deaths, mostly of young children, each year with a death from malaria occurring every 30 seconds (Singh et al., 2004). Ninety percent of the deaths occur in sub-Saharan Africa, but all tropical poor countries are affected. Four species of Plasmodium have been known to infect man namely: Plasmodium falciparum, P. vivax, P. ovale, P. malariae (Prudencio et al., 2006). In addition to these, there are over a 100 Plasmodium species that infect a variety of other hosts, including reptiles, rodents, birds, primates and other mammals (Cox-Singh and Singh, 2008). The dogma of only four species of Plasmodia infecting humans has recently been challenged by the discovery of a large focus of simian malaria parasite P.knowlesi in the Malaysian population (Singh et al., 2004).
Therefore, a fifth species P.knowlesi (monkey parasite) is now known to infect humans (Cox-Singh and Singh, 2008, Cox- Singh et al., 2008, Nishimoto et al., 2008). Plasmodium falciparum is so far the deadliest of the five species, and is responsible for most of the morbidity and mortality associated with malaria (Prudencio et al., 2006). P. knowlesi could become potentially dangerous if control measures are not taken (Nishimoto et al., 2008).
2.1.1 Malaria and it’s epidemiology
In 2006, World Health Organization (WHO) estimated that 3.3 billion persons were at risk of acquiring malaria. Of these, 247 million were infected (86% in Africa) and nearly 1 million (mostly African children) die of the acute or chronic infection. In 2008, malaria was still endemic in 109 countries worldwide, 45 of them in Africa ( WHO, 2006). WHO estimated that approximately 1.1 million persons were still dying of malaria (WHO, 2008). Malaria killed 437,000 children before their fifth birthday in 2013, the majority in sub-Saharan Africa (WHO, 2015). It is a mosquito-borne acute or chronic infection that killed an estimated 1.1 million people in 1998 and with an estimated 300 to 1,600000 new cases, but in 2013 the disease caused an estimated 453,000 under – five deaths (WHO, 2013). According to the latest estimates, malaria mortality rates were reduced by about 47% globally and by 54% in the WHO African Region between 2000 and 2013. The incidence rates declined by 30% around the world and by 34% in the African region (WHO, 2013). These substantial reductions occurred as a result of a major scale-up of vector control interventions, diagnostic testing and treatment with artemisinin – based combination therapies (Mbugi et al., 2010). It is important to note that children under the age of five and pregnant women are particularly vulnerable, while adults are also vulnerable either with an acute infection or chronic malaria infection (Mbugi et al., 2010).
2.1.2 The parasite
Human malaria results from acute or chronic infection with Plasmodium falciparum, P. vivax, P. ovale, or P. malariae. Plasmodium falciparum causes a large majority of the clinical cases and mortalities (Bozdech et al., 2003). Plasmodium is a protozoan parasite of the Phylum Apicompleza, Class Sporozoea. Reproduction generally is both sexual and asexual. Locomotion of mature organisms is by body flexon, gliding, or undulation of the longitudines ridges (Breman, 2001). Flagella is present only in microgametes, pseudopods ordinarily absent (Breman, 2001).
