Incidence of malaria in India continues to be the cause of concern as it imposes heavy economic burden on the country as well as on the families of the people affected by the disease.
According to World Health Organization report, “there were 4,45,000 malaria related deaths globally in 2016. India accounts for 6% of global malaria cases and 7% of deaths.
While countries like the Maldives, Sri Lanka and Kyrgyzstan have achieved malaria-free status, it is most unlikely that India would reduce its case burden beyond 40% by 2020. About 80% of death occurred in 15 countries, including India and Sub-Saharan African countries,” the report stated.
Union Health and Family Welfare Minister Mr J.P.Nadda says, “India has reduced its new malaria cases by one-third, and even crossed the malaria mortality target of 2020. The majority of malaria cases occur in the bordering districts, forests and tribal areas.”
Malaria is caused by Plasmodium parasites, five of its kind namely P.falciparum, P.vivax, P.ovale, P.malariae and P.knowlesi, following the bites of infected Anopheles mosquitoes. The incidence of P.falciparum variety that was once virulent in Indian scenario has now come down drastically, but P.vivax has become dominant to the level of 50% of the total malaria cases reported.
Origin of disease
According to Dr K.Thilagarani, Pathologist of KG Hospital, man and malaria seem to have evolved together and probably malaria parasites jumped onto human from apes through the bites of vector mosquitoes.
It was probably Hippocrates, the first malariologist. who described various forms of malaria. In a power-point presentation on the topic “Malaria lifecycle and pathogenesis,” delivered recently in KG Hospital Auditorium for the benefit of post-graduate medical students, Dr Thilagarani traced the sequence of how mosquito bites inject the parasites into the human system, the manifestation of disease, and how it affects the vital organs.
When a mosquito bites, hundreds of sporozoites are introduced into the skin. While some of the sporozoites are destroyed by the local macrophages, some enter the lymphatics and some others find a blood vessel.
Some of the sporozoites in the lymph node partially develop into exoerythrocytic stages. Then each sporozoite develops into a schizont, containing 10,000—30,000 merozoites. Dr Thilagarani says that the pre-erythrocytic phase remains “silent,”ie., it stays without symptoms. This phase lasts 5-9 days.
The erythrocytic cycles occur for various durations depending upon the type of parasites: 24 hours in case of P.knowlesi, 48 hours in case of P.falciparium, P.vivax and P.ovale, and 74 hours in case of P.malariae.
Newborns at risk
Dr Thilagarani says that there is a possibility of newborns contracting malaria when the parasitized red cells from infected mother are transmitted to the child either transplacentally or during labour. Congenital malaria occurs more often during the first pregnancy.
She says that malaria can be transmitted by transfusion of blood from infected donors and the infection might remain ineffective or dormant for weeks to months or even years. She cautions that those who have suffered from malaria should not donate blood for at least 3 years after becoming asymptomatic, and proven carriers of P.malariae should never donate blood.
Dr Thilagarani points out that the risk of transmission is higher in transfusion of fresh, whole blood, particularly when the blood has been stored for less than 5 days, and the risk is considerably lesser after 2 weeks. The risk is extremely low in cases of transfusions of plasma, plasma components or derivatives devoid of intact red cells.
Most vulnerable organs
Malaria can affect the vital organs such as the spleen, the liver, the lungs, the central nervous system and the kidneys. She further says that the microscopic tests such as the peripheral smear study and the Quantitative Buffy Coat test are commonly used for diagnosis.
Mosquito bites could be prevented by using insect repellents, mosquito net for the bed, wearing long sleeves while going out, covering doors and windows with nets and switching on the air-conditioner.