An eco-epidemiological analysis of dengue outbreak in Port Blair, South Andaman Island, India.

BACKGROUND OBJECTIVES: In Port Blair, the capital of Andaman & Nicobar Islands, in the Bay of Bengal, India, there was a sudden increase in fever cases resembling the symptoms of dengue in the monsoon period of 2022. Hence, an investigation was carried out to find out epidemiological and entomological reasons behind the outbreak. METHODS: An entomological survey was carried out in 24 wards of Port Blair Municipal Council (PBMC) area, epidemiological data of last six years (January-December 2017-2021 and January-October 2022) and patient details of the year 2022 were collected. Both the epidemiological and entomological data were analyzed concerning time and place. RESULTS: During this outbreak period tyres (22.4%) came out as a major breeding habitat followed by small discarded materials (17.5%), metal drums (15.3%), and plastic drums (11.7%). In rainy season, peri-domestic breeding (55%) was more than the domestic breeding (45%) habitat. Ae. aegypti had a high preference for indoor large containers (100-1000 L) like plastic tank, metal drum and cement tank whereasAe. albopictus prefers to breed in medium sized plastic container (20-100 L) and outdoor water receptacles like tyres, flower pots, and domestic discarded materials. INTERPRETATION CONCLUSION: By source reduction, indoor space spray and outdoor fogging, vector density was controlled which curtailed the transmission and within eight weeks a decreasing trend of dengue cases was noticed. A regular entomological survey is crucial to know the seasonality and key breeding habitats of the vector for proper planning of vector control.

An eco-epidemiological analysis of Dengue outbreak in Port Blair, South Andaman Island, India, during 2022.

BACKGROUND OBJECTIVES: In Port Blair, the capital of Andaman & Nicobar Islands, in the Bay of Bengal, there was a sudden increase in fever cases resembling the symptoms of dengue in the monsoon period of 2022. Hence, an investigation was carried out to find out both epidemiological and entomological reasons behind the outbreak. METHODS: An Entomological survey was carried out in 24 wards of Port Blair Municipal Council (PBMC) area, epidemiological data of last six years (January to December of 2017-2021 & January to October of 2022) and patient details of the year 2022 were collected. Both the epidemiological and entomological data were analyzed concerning time and place. RESULTS: During this outbreak period tyres (22.4%) came out as a major breeding habitat followed by small discarded materials (17.5%), metal drums (15.3%), and plastic drums (11.7%). In rainy season peri-domestic breeding (55%) was more than the domestic breeding (45%) habitat. Ae. aegypti had a high preference for indoor large containers (100-1000 L) like plastic tank, metal drum and cement tank whereas Ae. albopictus prefers to breed in medium sized plastic container (20-100 L) and outdoor water receptacles like tyres, flower pots, domestic discarded materials etc. INTERPRETATION CONCLUSION: By source reduction, indoor space spray and outdoor fogging vector density was controlled which curtailed the transmission and within 8 weeks decreasing trend of dengue cases were noticed. A regular entomological survey is very important to know the seasonality and key breeding habitats of the vector for proper planning of vector control.

First Report of Anopheles annularis s.l., An. maculatus s.s., and An. culicifacies s.l. as Malaria Vectors and a New Occurrence Record for An. pseudowillmori and An. sawadwongporni in Alipurduar District Villages, West Bengal, India.

A comprehensive entomological survey was undertaken in Alipurduar District, West Bengal, from 2018 to 2020 and in 2022. This study was prompted by reported malaria cases and conducted across nine villages, seven Sub-Centres, and three Primary Health Centres (PHCs). Mosquitoes were hand-collected with aspirators and flashlights from human dwellings and cattle sheds during the daytime. Both morphological and molecular techniques were used for species identification. Additionally, mosquitoes were tested for Plasmodium parasites and human blood presence. Mosquito species such as An. barbirostris s.l., An. hyrcanus s.l., An. splendidus, and An. vagus were morphologically identified. For species like An. annularis s.l., An. minimus s.s., An. culicifacies s.l., and An. maculatus s.s., a combination of morphological and molecular techniques was essential. The mitochondrial cytochrome c oxidase gene subunit 1 (CO1) was sequenced for An. annularis s.l., An. maculatus s.s., An. culicifacies s.l., An. vagus, and some damaged samples, revealing the presence of An. pseudowillmori and An. fluviatilis. The major Anopheles species were An. annularis s.l., An. culicifacies s.l., and An. maculatus s.s., especially in Kumargram and Turturi PHCs. Plasmodium positivity was notably high in An. annularis s.l. and An. maculatus s.s. with significant human blood meal positivity across most species. Morphological, molecular, and phylogenetic analyses are crucial, especially for archived samples, to accurately identify the mosquito fauna of a region. Notably, this study confirms the first occurrence of An. pseudowillmori and An. sawadwongporni in West Bengal and implicates An. maculatus s.s., An. culicifacies s.l., and An. annularis s.l. as significant vectors in the Alipurduar region.

Insecticide resistance status of malaria vectors in the malaria endemic states of India: implications and way forward for malaria elimination.

Background: In 2012, the World Health Organization (WHO) released the Global Plan for Insecticide Resistance Management in malaria vectors to stress the need to address insecticide resistance. In a prospective multi-centric study commissioned by the Indian Council of Medical Research (ICMR), we assessed the insecticide susceptibility status of the primary malaria vectors in India from 2017 through 2019. Methods: The insecticide susceptibility status of the prevalent primary malaria vectors - An. culicifacies, An. fluviatilis, An. stephensi, An. minimus and An. baimaii and secondary malaria vectors - An. aconitus, An. annularis and An. philippinensis/nivepes from 328 villages in 79 districts of 15 states of India were assessed following the WHO method mainly to insecticides used in vector control, organochlorine (DDT), organophosphate (malathion), and other pyrethroids (alpha-cypermethrin, cyfluthrin, lambda-cyhalothrin and permethrin). The study sites were selected as suggested by the National Vector Borne Disease Control Programme. Results: The primary malaria vector An. culicifacies showed resistance to DDT (50/50 districts including two districts of Northeastern India), malathion (27/44 districts), and deltamethrin (17/44 districts). This species was resistant to DDT alone in 19 districts, double resistant to DDT-malathion in 16 districts, double resistant to DDT-deltamethrin in 6 districts, and triple resistant to DDT-malathion-deltamethrin in 9 districts. An. minimus and An. baimaii were susceptible in Northeastern India while An. fluviatilis and the secondary malaria vector An. annularis was resistant to DDT in Jharkhand. Conclusion: In this study we report that among the primary vectors An. culicifacies is predominantly resistant to multiple insecticides. Our data suggest that periodic monitoring of insecticide susceptibility is vital. The national malaria program can take proactive steps for insecticide resistance management to continue its push toward malaria elimination in India.

Leucocytosis and early organ involvement as risk factors of mortality in adults with dengue fever.

The clinical profile and risk factors for mortality in dengue fever have evolved over the years. The all-cause mortality in admitted dengue patients is around 6%. We aimed to evaluate the recent change in trends of the clinical characteristics and risk factors for in-hospital mortality in adults with dengue fever. This is a retrospective study on adults with confirmed dengue fever admitted in a medical unit of a tertiary care center in North India. Medical records of confirmed dengue fever patients admitted between January 2011, and December 2016 were reviewed. Chi-squared tests with Bonferroni correction for multiple testing were used to identify risk factors for mortality. 232 records were included, of which 66.8% were males. The mean age was 31.6 ± 14 years. There were 17 deaths with an all-cause mortality rate of 7.3% with 76.5% being classified as severe dengue at admission. Among the 17 mortality cases, dyspnea (47%), tachypnea (86.7%), leucocytosis (58.8%), raised urea (80%), and elevated serum creatinine (52.9%) at presentation were significantly associated with mortality (p < 0.001). Shock at any time during the hospital stay (58.8%) was also found to be significantly associated with mortality (p < 0.001). We found that dyspnea, tachypnea, acute kidney injury, and leucocytosis at presentation was significantly associated with in-hospital mortality. Based on our results, we recommend aggressive management of patients with severe dengue and those with mild/moderate disease with the above risk factors.

A study on dengue outbreak during 2009 in Bhopal and Indore districts of Madhya Pradesh, India.

An outbreak of mysterious virus disease reported from Bhopal, Indore and adjoining districts of Madhya Pradesh (MP) state during 2009. The outbreak started in Bhopal in early September and then from Indore in last week of September. Subsequently cases were also reported from adjoining districts. On basis of Epidemiological, Clinical, Entomological and Laboratory findings dengue outbreak was declared in the area. A total of 620 IgM Elisa positive cases were reported from Bhopal and Indore district and adjoining areas. The outbreak involved 8 districts in the state. The control measures were undertaken in the area and the outbreak of dengue subsided in December 2009.

Laboratory bio-assay of temephos and fenthion against some vector species of public health importance.

Laboratory studies carried out using Temephos and Fenthion, two commonly used larvicides under Urban Malaria Scheme (NMEP) and NFCP for the control of mosquito larvae. The results revealed that the LC50 and LC90 values for temephos against Aedes aegypti 0.0177 and 0.0559, Anopheles stephensi 0.0148 and 0.0472, Culex quinquefasciatus 0.0157 & 0.0480 and for Culex vishnui group of mosquitoes 0.043 & 0.0118 ppm respectively. The results obtained revealed that there is a 62.8 & 94.12 times increase in the LC50 & LC90 of Cx. Quinquefasciatus which indicates that the species has developed resistance to temephos. There were 6.32 & 8.34 fold increase in Ae. aegypti and 2.27 & 2.34 fold increase in LC50 & LC90 values of An. stephensi are indicative of development of tolerance against temephos. Similarly LC50 and LC90 values estimated for fenthion against Ae. aegypti 0.0173 & 0.0392, An. stephensi 0.0274 & 0.0992 and Cx. quinquefasciatus 0.03 & 0.0469 respectively. The slope values were found to be higher in fenthion as compared to temephos. It was recorded to be 2.72 times higher in Cx. quinquefasciatus and 1.54 times against An. stephensi. However, much difference was not observed in the slope values of temephos and fenthion in Ae. aegypti.