Author (P.C. Mishra, Rachna Hora)
Malaria is an infectious disease that dates as early as 2700 B.C., and is caused by a unicellular eukaryotic parasite ‘Plasmodium’. The word ‘malaria’ originates from the Italian phrase ‘mala aria’ meaning ‘bad air’. British physician Sir Ronald Ross identified genus Anopheles mosquitoes as vectors for transmission of this disease in 1897. There are more than 60 different species of Anopheles mosquitoes which are now known to be vectors of malaria parasite. Malaria is most widespread in the tropical countries with the African, South East Asian, Eastern Mediterranean and Western Pacific being defined as the endemic regions by World Health Organization (WHO). Spread of this disease in humans occurs through the bite of female anopheles mosquito infected with species Plasmodium falciparum (Pf), P. vivax(Pv), P. ovale(Po), P. malariae(Pm)or P. knowlesi(Pk). Of these, Pf causes the most lethal form of malaria which is responsible for most associated deaths especially in the Sub-Saharan African region. While Pf infections predominate the African continent, Pv and Pf-Pv mixed infections are more common in South-East Asia, including India. Globally, malaria accounts for nearly 0.4 million deaths annually with most victims being children less than 5 years of age. Common manifestations of the disease include high fever, shaking chills, anemia, respiratory distress etc. Though uncomplicated malaria is considered easily treatable with drugs, a large fraction of Pf infected patients develop severe complicated malaria. This may present itself as cerebral malaria causing seizures and coma. Neurological sequelaeresulting from cerebral malaria include cognitive defects, cortical blindness, deafness, epilepsy etc. leading to prolonged or permanent debilitation of the patients. Cerebral malaria is a form of malaria that results from cytoadherence of Plasmodium infected red blood cells on brain endothelium obstructing blood flow to the brain. Pregnant women residing in endemic areas are considered susceptible to placental malaria in which blood blow to the placental tissue is blocked by cytoadherence, leading to fetal mortality. While Pf is responsible for severe disease, Pv infection can cause recurrent malaria due to the formation of hypnozoites that lie dormant in the liver for long periods. These can be activated to show disease symptoms when favorable conditions occur.