Vector-borne diseases in central India, with reference to malaria, filaria, dengue and chikungunya.

Background: Vector-borne diseases (VBDs) caused by parasites and viruses are a major cause of morbidity and mortality in Madhya Pradesh (MP), central India. These diseases are malaria, lymphatic filariasis, dengue and chikungunya. Epidemiological information is lacking on different VBDs that are commonly prevalent in rural-tribal areas of MP, except on malaria.

Methods: The studies were carried out at the request of Government of Madhya Pradesh, in three locations where many VBDs are endemic. Data on malaria/filaria prevalence were collected by repeatedly undertaking cross-sectional parasitological surveys in the same areas for 3 years. For dengue and chikungunya, suspected cases were referred to the research centre.

Results: Monitoring of results revealed that all the diseases are commonly prevalent in the region, and show year-to-year variation. Malaria slide positivity (the number of malaria parasitaemic cases, divided by the total number of blood smears made) was 18.7% (190/1018), 16.4% (372/2266) and 20.4% (104/509) respectively in the years 2011, 2012 and 2013. There was a strong age pattern in both Plasmodium vivax and P. falciparum. The slide vivax rate was highest among infants, at 5% (odds ratio [OR] = 3.8; 95% confidence interval [CI] - 1.5 to 9.4; P<0.05) and the highest slide falciparum rate was 20% in children aged 1-4 years (OR = 2.0; 95%CI 1.5 to 2.7; p<0.0001). This age-related pattern was not seen in other VBDs. The microfilaria rate was 7.5%, 7.6% and 7.8% in the years 2010, 2012 and 2013, respectively. Overall, microfilaria rates were higher in males (8.7%) as compared to females 6.4% (OR = 1.5; 95% CI = 1.1 to 2.0; P < 0.01). The prevalence of dengue was 48% (dengue viruses 1 and 4 - DENV-1 and DENV-4), 59% (DENV-1) and 34% (DENV-3) respectively, in the years 2011, 2012 and 2013 among referred samples, while for chikungunya very few samples were found to be positive.

Conclusion: Despite recent advances in potential vaccines and new therapeutic schemes, the control of VBDs remains difficult. Therefore, interruption of transmission still relies on vector-control measures. A coordinated, consistent, integrated vector-management approach is needed to control malaria, filaria, dengue and chikungunya.