Abstract
BackgroundMalaria is a major public health problem in India. Data from surveys totaling 3031 participants at three sites revealed a high proportion of asymptomatic infections, complicating diagnosis. The aim of this study was to identify differences in complaints and symptoms between sites, and factors associated with asymptomatic Plasmodium infections.MethodsPublished data from community-based cross-sectional studies conducted between 2012 and 2015 in Nadiad (Gujarat), Chennai (Tamil Nadu), and Rourkela (Odisha) as part of the Center for the Study of Complex Malaria in India were analysed. Complaints and symptoms were systematically recorded, and Plasmodium infections confirmed using microscopy, rapid diagnostic tests (RDTs), and polymerase chain reaction (PCR). Multivariate analyses were conducted to determine the association between general symptoms and age, season, or gender, and factors associated with asymptomatic Plasmodium infections were assessed.ResultsComplaints of any illness were lowest in Chennai (17.7%), 30.6% in Rourkela and 42.7% in Nadiad. Complaints were more often reported for children; gender differences were noted in Rourkela only. In Nadiad, 7.0% of 796 participants were positive for malaria by PCR (32% Plasmodium falciparum); 78.6% had a history of fever or documented fever, 14.3% had other symptoms, and 7.1% were “truly asymptomatic”. For Chennai this was 29.2%, 4.2% and 66.7% respectively, with a malaria prevalence of 2.6% by PCR of 928 participants (29% P. falciparum). In Rourkela, with 7.7% of 1307 participants positive for malaria by PCR (82% P. falciparum), the percentages were 35.6%, 24.8% and 39.6%, respectively. In Rourkela, asymptomatic infections were associated with young age and male gender (microscopy or RDT), and with rainy season (PCR). In the same site, participants with Plasmodium vivax were more likely to be asymptomatic (11/18 or 61.1%) than persons with P. falciparum mono-infections (27/78 or 34.6%); gametocytes for P. falciparum were evenly distributed between symptomatic and asymptomatic infections (2/53 vs. 2/49, respectively). The addition of the symptoms “headache”, “aches” and “chills” to fever improved the case-definition of symptomatic malaria.ConclusionThere were considerable differences in complaints at the three sites in India. Malaria and asymptomatic infections differ by region, indicating that malaria elimination will require localized approaches.
Highlights
Malaria is a major public health problem in India
Insecticidetreated nets (ITNs) were only used in Rourkela, while the use of personal mosquito repellents was common in Chennai
This study shows the importance of using an appropriate case-definition for asymptomatic infections: fever, chills, aches, and headaches identified all symptomatic malaria cases in Chennai, and most in Nadiad
Summary
Malaria is a major public health problem in India. Data from surveys totaling 3031 participants at three sites revealed a high proportion of asymptomatic infections, complicating diagnosis. In 2018, the National Vector Borne Disease Control Programme (NVBDCP) estimated that approximately 500,000 people suffered from malaria (63% Plasmodium falciparum), and less than 100 persons died [1]. These numbers are van Eijk et al Malar J (2020) 19:237 likely an underestimate; the World Malaria Report estimated that only 16% of cases may be detected by the Indian malaria surveillance system [2]. The major malaria vector is Anopheles culicifacies, estimated to be associated with 60–65% of the malaria disease burden in India [3]. The diverse malaria settings make the goal of malaria elimination challenging; one size does not fit all, and multiple localized strategies are needed, a stance supported by the National Framework for Malaria Elimination in India [5]
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