Spatial and temporal village-level prevalence of Plasmodium infection and associated risk factors in two districts of Meghalaya, India

Abstract

Background Despite declining incidence over the past decade, malaria remains an important health burden in India. This study aimed to assess the village-level temporal patterns of Plasmodium infection in two districts of the north-eastern state of Meghalaya and evaluate risk factors that might explain these patterns. Methods Primary Health Centre passive malaria case data from 2014 to 2018 were analysed to characterize village-specific annual incidence and temporal trends. Active malaria case detection was undertaken in 2018 and 2019 to detect Plasmodium infections using PCR. A questionnaire collected socio-demographic, environmental, and behavioural data, and households were spatially mapped via GPS. Adult mosquitoes were sampled at a subset of subjects' houses, and Anopheles were identified by PCR and sequencing. Risk factors for Plasmodium infection were evaluated using bivariate and multivariate logistic regression analysis, and spatial cluster analysis was undertaken. Results The annual malaria incidence from PHC-based passive surveillance datasets in 2014–2018 was heterogenous but declining across villages in both districts. Active surveillance in 2018 enrolled 1468 individuals from 468 households (West Jaintia Hills) and 1274 individuals from 359 households (West Khasi Hills). Plasmodium falciparum prevalence per 100 people varied from 0 to 4.1% in the nine villages of West Jaintia Hills, and from 0 to 10.6% in the 12 villages of West Khasi Hills. Significant clustering of P. falciparum infections [observed = 11, expected = 2.15, Relative Risk (RR) = 12.65; p < 0.001] was observed in West Khasi Hills. A total of 13 Anopheles species were found at 53 houses in five villages, with Anopheles jeyporiensis being the most abundant. Risk of infection increased with presence of mosquitoes and electricity in the households [Odds Ratio (OR) = 1.19 and 1.11], respectively. Households with reported animals had reduced infection risk (OR = 0.91). Conclusion Malaria incidence during 2014–2018 declined in all study villages covered by the passive surveillance data, a period that includes the first widespread insecticide-treated net campaign. The survey data from 2018 revealed a significant association between Plasmodium infection and certain household characteristics. Since species of Plasmodium-competent mosquito vectors continue to be abundant, malaria resurgence remains a threat, and control efforts should continue.

Household and individual level risk factors associated with declining malaria incidence in Meghalaya, India: implications for malaria elimination in low-endemic settings

“…With 23–28 °C temperatures and high relative humidity (> 70%) the conditions are conducive for mosquito breeding and perennial transmission. Between 2012 and 2015, the number of malaria cases and deaths in Meghalaya increased steadily, but seems to have generally declined from 2016 [ 10 ], although the rate of decline varied between and within districts [ 11 ].

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“…This lag in declining incidence is partly due to the unique ecological and socio-cultural conditions of the NER, inhospitable terrain, poor road conditions and inadequate healthcare infrastructure, all of which may have contributed to the relatively high malaria incidence, until recently [ 3 ]. This is particularly true in the state of Meghalaya where incidence increased from 2012 to 2015, and only began to decline after 2016 [ 10 , 11 ]. The reasons for the observed delayed decline in malaria incidence in Meghalaya are unclear but could be related to the first wide-spread distribution of long-lasting insecticidal nets (LLINs) in the endemic communities not occurring until 2016 [ 11 ].…”

“…This is particularly true in the state of Meghalaya where incidence increased from 2012 to 2015, and only began to decline after 2016 [ 10 , 11 ]. The reasons for the observed delayed decline in malaria incidence in Meghalaya are unclear but could be related to the first wide-spread distribution of long-lasting insecticidal nets (LLINs) in the endemic communities not occurring until 2016 [ 11 ].…”

“…Information on malaria patterns in Meghalaya is limited to unpublished government reports and a recent cross-sectional survey in two districts [ 11 ]. The later characterised village-level prevalence of Plasmodium infection during 2018–2019 in 21 villages, summarised village-level risk factors for infection, and identified 13 Anopheles mosquito species as potential vectors in a subset of villages [ 11 ].…”

“…Information on malaria patterns in Meghalaya is limited to unpublished government reports and a recent cross-sectional survey in two districts [ 11 ]. The later characterised village-level prevalence of Plasmodium infection during 2018–2019 in 21 villages, summarised village-level risk factors for infection, and identified 13 Anopheles mosquito species as potential vectors in a subset of villages [ 11 ]. To further understand the epidemiology of malaria in Meghalaya, the study presented here undertook detailed analysis of household and individual level Plasmodium infection patterns in the same two low-endemic communities in 2018–2019, evaluated social and behavioural risk factors for infection, and explored patterns of Plasmodium antigen-specific antibodies in the population.…”