Malaria in South Asia: prevalence and control

Abstract

The "Malaria Evolution in South Asia" (MESA) program project is an International Center of Excellence for Malaria Research (ICEMR) sponsored by the US National Institutes of Health. This US-India collaborative program will study the origin of genetic diversity of malaria parasites and their selection on the Indian subcontinent. This knowledge should contribute to a better understanding of unexpected disease outbreaks and unpredictable disease presentations from Plasmodium falciparum and Plasmodium vivax infections. In this first of two reviews, we highlight malaria prevalence in India. In particular, we draw attention to variations in distribution of different human-parasites and different vectors, variation in drug resistance traits, and multiple forms of clinical presentations. Uneven malaria severity in India is often attributed to large discrepancies in health care accessibility as well as human migrations within the country and across neighboring borders. Poor access to health care goes hand in hand with poor reporting from some of the same areas, combining to possibly distort disease prevalence and death from malaria in some parts of India. Corrections are underway in the form of increased resources for disease control, greater engagement of village-level health workers for early diagnosis and treatment, and possibly new public-private partnerships activities accompanying traditional national malaria control programs in the most severely affected areas. A second accompanying review raises the possibility that, beyond uneven health care, evolutionary pressures may alter malaria parasites in ways that contribute to severe disease in India, particularly in the NE corridor of India bordering Myanmar Narayanasamy et al., 2012.

Fig. 1

An old map showing one view of South Asia countries, with pre-independence names: India (without Indian Kashmir), West Pakistan (now Pakistan), Afghanistan, East Pakistan (now Bangladesh), Ceylon (now Sri Lanka), Nepal, Bhutan, and Burma (now Myanmar). http://www.probertencyclopaedia.com/photolib/maps/.

Fig. 2

(A) Present state map of India (http://blog.lookindia.in). This is to help readers identify the different states mentioned in the text in the context of malaria epidemiology in India. (B) Districts of India vary widely in ABER compliance (2008 data). Some malaria prone N and NE districts (see Fig. 3) are among the poorest in malaria surveillance compliance (Map prepared by NIMR, Goa, using data from the National Vector Borne Disease Control Program, New Delhi).

Fig. 3

Annual Parasite Incidence (Slide positive malaria cases/1000 population) in India for the year 2008 (Map prepared by NIMR, Goa, using data from the National Vector Borne Disease Control Program, New Delhi).

Fig. 4

Changes in malaria prevalence in the South East Asia Region as reported by the member countries to WHO from 1971 to 2009. In this region, after resurgence of malaria in the mid seventies in the post eradication era, reported incidence of malaria has stabilized as seen in the trends of API and SPR. SPR represents Slide Positivity Rates (malaria incidences per 1000slides read). In contrast, P. falciparum proportion has consistently increased to reach 60% in recent years. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Data source: www.who.searo.int; WHO (2001a,b).

Fig. 5

Malaria endemic zones of South Asia. Highest transmission is shown in rust, and low transmission in yellow. These WHO estimates are likely to undergo continual reevaluation as more internal research activities take place in these countries, as well as cross checks from global NIH ICEMR activities. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Source: www.who.searo.int; WHO (2001a,b).

Fig. 6

India was estimated to be the largest contributor of malaria to South and South East in 2009.

Fig. 7

Distribution of confirmed chloroquine resistance sites (red triangles) in India based on data from the National Vector Borne Diseases Control Program, India; Shah et al. (2011a,b). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Source: http://nvbdcp.gov.in/DRUG.html.

Fig. 8

General distribution of primary vectors of malaria in India. An. cuclicifacies has wide distribution in rural plains, An. stephensi is an urban vector, An. fluviatilis is a vector in hills and foothills in the mainland, while An. minimus, An. nivipes and An. dirus are important vectors in the North Eastern India. An. sundaicus is restricted to the Andaman and Car Nicobar Islands. An. annularis (not shown in the figure) is suspected to play an important role in malaria transmission in the Eastern Indian states of Jharkhand and Orissa.