A comparative study on vector competence of Anopheles stephensi from geographically distinct malarious and a non-malarious urban area to Plasmodium vivax.

BACKGROUND OBJECTIVES: Anopheles stephensi is responsible for the transmission of malaria in urban areas. Vector competence of An. stephensi from a non-malarious (Coimbatore) and highly malarious (Chennai) urban areas in Tamil Nadu state of India, was investigated to find the reason for non-transmission of malaria in Coimbatore. METHODS: Vector competence (susceptibility/refractoriness) of An. stephensi mosquitoes from Chennai (malarious) and Coimbatore (non-malarious) to Plasmodium vivax (Chennai) was investigated. Bioassays were carried out concurrently in both these strains by artificial membrane feeding technique using the same malaria-infected blood. An. stephensi were dissected to observe infection in midgut and salivary gland. The parasite infection, oocyst and sporozoite positivity rate, the oocyst load, correlation between male-female gametocyte ratio and infection, and Survival Analysis of parasitic stages during sporogony were analyzed and compared. RESULTS: The overall infection rate was 45.8 and 41.2 percent in Chennai and Coimbatore, respectively. Oocyst count ranged from 1-80 and 1-208 respectively and not statistically significant. Oocyst positivity was high from Day 8-21 in both strains. The Mean Survival Day (MSD) for oocyst was Day 14 in both strains. Sporozoite was observed in four experiments in each of the strains and the MSD for sporozoites was Day 20 in Chennai and Day 17 in Coimbatore. INTERPRETATION CONCLUSION: An. stephensi of Chennai and Coimbatore are equally susceptible to P. vivax infection and non-transmission of malaria in Coimbatore can be attributed to external factors such as the presence of preferential breeding habitat, vector density, vector survival, and weather. The only difference observed was the comparatively shortened oocyst maturation time in the Coimbatore strain which requires further investigation.

Impact of climate change on temperature variations and extrinsic incubation period of malaria parasites in Chennai, India: implications for its disease transmission potential.

BACKGROUND: The global temperature has significantly risen in the past century. Studies have indicated that higher temperature intensifies malaria transmission in tropical and temperate countries. Temperature fluctuations will have a potential impact on parasite development in the vector Anopheles mosquito. METHODS: Year-long microclimate temperatures were recorded from a malaria-endemic area, Chennai, India, from September 2021 to August 2022. HOBO data loggers were placed in different vector resting sites including indoor and outdoor roof types. Downloaded temperatures were categorised by season, and the mean temperature was compared with data from the same study area recorded from November 2012 to October 2013. The extrinsic incubation period for Plasmodium falciparum and P. vivax was calculated from longitudinal temperatures recorded during both periods. Vector surveillance was also carried out in the area during the summer season. RESULTS: In general, temperature and daily temperature range (DTR) have increased significantly compared to the 2012-2013 data, especially the DTR of indoor asbestos structures, from 4.30 â„ƒ to 12.62 â„ƒ in 2021-2022, unlike the marginal increase observed in thatched and concrete structures. Likewise, the average DTR of outdoor asbestos structures increased from 5.02 â„ƒ (2012-2013) to 8.76 â„ƒ (2021-2022) although the increase was marginal in thatched structures and, surprisingly, showed no such changes in concrete structures. The key finding of the extrinsic incubation period (EIP) is that a decreasing trend was observed in 2021-2022 compared to 2012-2013, mainly in indoor asbestos structures from 7.01 to 6.35 days, which negatively correlated with the current observation of an increase in temperature. Vector surveillance undertaken in the summer season revealed the presence of Anopheles breeding in various habitats. Anopheles stephensi could be collected using CDC light traps along with other mosquito species. CONCLUSION: The microclimate temperature has increased significantly over the years, and mosquitoes are gradually adapting to this rising temperature. Temperature negatively correlates with the extrinsic incubation period of the parasite. As the temperature increases, the development of the parasite in An. stephensi will be faster because of a decrease in EIP, thus requiring relatively fewer days, posing a risk for disease transmission and a hindrance to malaria elimination efforts.

Community perspective and healthcare assessment in malaria endemic states of India: a cross-sectional study protocol.

INTRODUCTION: India's contribution to the malaria burden was highest in South-East Asia Region in 2021, accounting for 79% of the estimated malaria cases and 83% of malaria-related deaths. Intensified Malaria Control Programme supported by Global Funds to Fight against AIDS, Tuberculosis and Malaria has deployed crucial interventions to reduce the overall burden of malaria in India. Evaluation of utilisation of malaria elimination interventions by the community and assessment of the healthcare system is underway in eleven high malaria endemic states in India. Health system preparedness for malaria elimination, logistics, and supply chain management of diagnostic kits and anti-malarial drugs in addition to the knowledge, attitude and practice of the healthcare workers is also being assessed. METHODS AND ANALYSIS: The study is being undertaken in 11 malaria endemic states with a variable annual parasite incidence of malaria. In total, 47 districts (administrative unit of malaria control operations) covering 37 976 households are to be interviewed and assessed. We present here the protocol following which the study is being undertaken at the behest and approval of Ministry of Health and Family Welfare in India. ETHICS AND DISSEMINATION: No patients were involved in the study. Study findings will be shared with Institutional ethics board of National Institute for Malaria Research New Delhi (NIMR) in a timely, comprehensive, accurate, unbiased, unambiguous and transparent manner and to the National Vector-borne Disease (Malaria) Control Programme officers and the Community public who participated. Important findings will be communicated through community outreach meetings which are existing in the Health system. Results will be informed to study participants via local fieldwork supervised by District Malaria Officers. Also findings will be published in reputed journals based on Indian Council of Medical Research (ICMR) publication policy.The ICMR-NIMR ethics committee approved the study via letter No. NIMR/ECM/2023/Feb/14 dated 24 April 2023 for version 5. All standard ethical practices will be followed.