By Jane M. Carlton and Sandra Albert
April 25 marks World Malaria Day 2022, a time when researchers, clinicians, and health workers around the world come together to highlight the burden of this ancient disease, and mark the ways in which communities unite around the common goal of malaria elimination. Malaria is a disease that affects men, women and children of all ages in India, and has caused untold deaths and suffering. Caused by species of the Plasmodium parasite that are transmitted by the bite of a female Anopheles mosquito, the disease can cause debilitating fever and paroxysms, anemia and multi-organ failure that can result in cerebral malaria and eventually death.
According to the World Malaria Report 2021: Globally, there were an estimated 241 million malaria cases in 2020 in 85 malaria endemic countries, increasing from 227 million in 2019. The highest burden continues to be in countries in the WHO African Region. The WHO South-East Asia Region accounted for about 2% of the burden of malaria cases globally. Malaria cases reduced by 78%, from 23 million in 2000 to about 5 million in 2020. Malaria case incidence in this region reduced by 83%, from about 18 cases per 1000 population at risk in 2000 to about three cases in 2020. India accounted for 83% of cases in the South-East Asian region. But overall, India continues to show remarkable progress in the control of malaria, and there was no rebound or increase during the pandemic. India launched a National Framework of Malaria Elimination in 2016 with the goal of achieving zero indigenous cases in the country by 2030.
Unlike countries in Africa where one or two species of malaria parasite cause infections and are transmitted by only one or two major mosquito species, malaria in India is “complex” caused by at least four different parasite species and transmitted by at least half a dozen mosquito species. Thus, contributing to complexity in manifestation and management.
Over the past decade, the prevalence of malaria has been decreasing in many countries worldwide, although the precise reasons why are not clear. Some say that the widespread distribution of long-lasting insecticide treated bed nets (LLIN) combined with new antimalarial drugs such as artemisinin combination therapies (ACT) has tipped the balance against the deadly parasite/mosquito duo. But in several countries the reduction in malaria occurred prior to the introduction of such new methods of control. In 2020 the first W.H.O. approved malaria vaccine R,TSS was approved for use in children in mid-high endemic areas in sub-Saharan Africa. Malaria vaccines although long in the making have a disappointingly low effectiveness in the range of 35-65%.
In Meghalaya, the National Vector Borne Disease Control Programme (NVBDCP) has made remarkable progress in its effort to control malaria. The state reported a notable decline in malaria cases and deaths since 2016 to now historically low levels, with only 483 cases reported in the whole of the state in 2021. Our epidemiology studies too as part of an international collaboration called the “Center for the Study of Complex Malaria in India” have also shown a significant reduction in malaria in several districts of Meghalaya and confirm that the malaria parasite has gone “underground” and infections are mostly asymptomatic with low parasite levels.
In 2019-2020 a second round of LLIN distribution took place in Meghalaya. An independent evaluation of the control programme in Meghalaya by our research team demonstrated high bednet distribution (99.5%) was achieved as per plan of the NVBDCP. It was observed that bed nets have been widely accepted by our rural communities, but the second control measure of indoor residual spraying with DDT is less popular. Only about 18 % of the households observed accepted spraying.
From 2010–2020, international sources led by the USA provided 69% of the total funding for malaria control and elimination. Within the public sector and among all malaria R&D funders, the US National Institutes of Health (NIH) was the largest contributor in 2020, contributing over half of its US$ 1.9 billion investment into basic research. The need for R&D continues as one cannot stop evolution and adaptation of parasites against human endeavors to eliminate them. The Rapid diagnostic tests (RDT) deployed by front line workers have been a key strategy that has aided early detection and treatment of malaria. Deletions in the parasite’s pfhrp2/3 genes render parasites undetectable by RDTs that are based on histidine-rich protein 2 (HRP2). Slow but increasing drug resistance to ATS compounds is a cause for concern and globally resistance to pyrethroids, the primary insecticides currently used in LLIN, is also rising.
This year’s World Malaria Day theme is “Harness innovation to reduce the malaria disease burden and save lives”. The research in our Center has taken this catchphrase to heart since operations started in 2017. For example, we have been using new technologies such as high-throughput immunology assays to identify antibodies in individuals that indicate a recent infection, even in the absence of malaria parasites. We are using next generation genomics to look at the genes of the ‘disappearing’ malaria parasites. And we are using molecular identification of Anopheles species to enhance accuracy compared to the morphological identification tools that are usually used. This has helped identify new anopheles vector species in Meghalaya e.g. An xui that was not previously reported in India.
In 2021, the WHO certified China and El Salvador as malaria-free, and a further 25 countries including India are reported to be on track to end malaria transmission within the decade. Malaria elimination, the dream of public health practitioners, clinicians, and scientists, may now finally be within sight in Meghalaya.
Jane M. Carlton, Silver Professor of Biology and Genomics Director, Center for the Study of Complex Malaria in India New York University, USA. Sandra Albert, Director, Indian Institute of Public Health Shillong