Malaria in India, while decreasing, remains a serious public health problem, and the contribution of submicroscopic and asymptomatic infections to its persistence is poorly understood. We conducted community surveys and clinic studies at three sites in India differing in their eco-epidemiologies: Chennai (Tamil Nadu), Nadiad (Gujarat), and Rourkela (Odisha), during 2012–2015. A total of 6,645 subject blood samples were collected for Plasmodium diagnosis by microscopy and PCR, and an extensive clinical questionnaire completed. Malaria prevalence ranged from 3–8% by PCR in community surveys (24 infections in Chennai, 56 in Nadiad, 101 in Rourkela), with Plasmodium vivax dominating in Chennai (70.8%) and Nadiad (67.9%), and Plasmodium falciparum in Rourkela (77.3%). A proportional high burden of asymptomatic and submicroscopic infections was detected in community surveys in Chennai (71% and 71%, respectively, 17 infections for both) and Rourkela (64% and 31%, 65 and 31 infections, respectively). In clinic studies, a proportional high burden of infections was identified as submicroscopic in Rourkela (45%, 42 infections) and Chennai (19%, 42 infections). In the community surveys, anemia and fever were significantly more common among microscopic than submicroscopic infections. Exploratory spatial analysis identified a number of potential malaria hotspots at all three sites. There is a considerable burden of submicroscopic and asymptomatic malaria in malarious regions in India, which may act as a reservoir with implications for malaria elimination strategies.

Understanding naturally acquired immune responses to Plasmodium in India is key to improving malaria surveillance and diagnostic tools. Here we describe serological profiling of immune responses at three sites in India by probing protein microarrays consisting of 515 Plasmodium vivax and 500 Plasmodium falciparum proteins with 353 plasma samples. A total of 236 malaria-positive (symptomatic and asymptomatic) plasma samples and 117 malaria-negative samples were collected at three field sites in Raurkela, Nadiad, and Chennai. Indian samples showed significant seroreactivity to 265 P. vivax and 373 P. falciparum antigens, but overall seroreactivity to P. vivax antigens was lower compared to P. falciparum antigens. We identified the most immunogenic antigens of both Plasmodium species that were recognized at all three sites in India, as well as P. falciparum antigens that were associated with asymptomatic malaria. This is the first genome-scale analysis of serological responses to the two major species of malaria parasite in India. The range of immune responses characterized in different endemic settings argues for targeted surveillance approaches tailored to the diverse epidemiology of malaria across the world.

BackgroundRepellents such as coils, vaporizers, mats and creams can be used to reduce the risk of malaria and other infectious diseases. Although evidence for their effectiveness is limited, they are advertised as providing an additional approach to mosquito control in combination with other strategies, e.g. insecticide-treated nets. We examined the use of repellents in India in an urban setting in Chennai (mainly Plasmodium vivax malaria), a peri-urban setting in Nadiad (both P. vivax and P. falciparum malaria), and a more rural setting in Raurkela (mainly P. falciparum malaria).MethodsThe use of repellents was examined at the household level during a census, and at the individual level in cross-sectional surveys and among patients visiting a clinic with fever or other symptoms. Factors associated with their use were examined in a multivariate analysis, and the association between malaria and the use of repellents was assessed among survey- and clinic participants.ResultsCharacteristics of participants differed by region, with more people of higher education present in Chennai. Use of repellents varied between 56–77 % at the household level and between 32–78 % at the individual level. Vaporizers were the main repellents used in Chennai, whereas coils were more common in Nadiad and Raurkela. In Chennai and Nadiad, vaporizers were more likely to be used in households with young male children. Vaporizer use was associated with higher socio-economic status (SES) in households in Chennai and Nadiad, whereas use of coils was greater in the lower SES strata. In Raurkela, there was a higher use of coils among the higher SES strata. Education was associated with the use of a repellent among survey participants in Chennai and clinic study participants in Chennai and Nadiad. Repellent use was associated with less malaria in the clinic study in Chennai and Raurkela, but not in the surveys, with the exception of the use of coils in Nadiad.ConclusionsRepellents are widely used in India. Their use is influenced by the level of education and SES. Information on effectiveness and guidance on choices may improve rational use.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1709-9) contains supplementary material, which is available to authorized users.

Background We conducted a diagnostic surveillance study to identify Plasmodium , dengue virus, chikungunya virus, and Orientia tsutsugamushi infections among febrile patients who underwent triage for malaria in the outpatient department at Ispat General Hospital, Rourkela, Odisha, India. Methods Febrile patients were enrolled from January 2016–January 2017. Blood smears and small volumes or vacutainers of blood were collected from study participants to carry out diagnostic assays. Malaria was diagnosed using rapid diagnostic tests (RDT), microscopy, and PCR. Dengue, chikungunya, and scrub typhus infections were identified using rapid diagnostic test kits and ELISA. Results Nine hundred and fifty-four patients were prospectively enrolled in our study. The majority of patients were male (58.4%) and more than 15 years of age (66.4%). All 954 enrollees underwent additional testing for malaria; a subset of enrollees (293/954) that had larger volumes of plasma available was also tested for dengue, chikungunya and scrub typhus by either RDT or ELISA or both tests. Fifty-four of 954 patients (5.7%) were positive for malaria by RDT, or microscopy, or PCR. Seventy-four of 293 patients (25.3%) tested positive for dengue by either RDT or ELISA, and 17 of 293 patients (5.8%) tested positive for chikungunya-specific IgM by either ELISA or RDT. Ten of 287 patients tested (3.5%) were positive for scrub typhus by ELISA specific for scrub typhus IgM. Seventeen patients among 290 (5.9%) with results for ≥3 infections tested positive for more than one infection. Patients with scrub typhus and chikungunya had high rates of co-infection: of the 10 patients positive for scrub typhus, six were positive for dengue ( p = 0.009), and five of 17 patients positive for chikungunya (by RDT or ELISA) were also diagnosed with malaria ( p < 0.001). Conclusions Dengue, chikungunya and scrub typhus are important etiologies of non-malarial febrile illness in Rourkela, Odisha, and comorbidity should be considered. Routine febrile illness surveillance is required to accurately establish the prevalence of these infections in this region, to offer timely treatment, and to implement appropriate methods of control. Electronic supplementary material The online version of this article (10.1186/s12879-019-4161-6) contains supplementary material, which is available to authorized users.

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