Effect of ultraviolet radiation on immature stages of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus mosquitoes.

Background & objectives: Understanding the influence of ultraviolet light on organisms is important for examining the hazards of exposure to ultraviolet (UV) light. However, little is known about the biological toxicity of ultraviolet light against mosquitoes, which are regularly exposed to UV light. This study was planned to determine the impact of UV radiation on different aquatic stages of Aedes aegypti, Anopheles stephensi and Culex quinquefaciatus mosquitoes. Methods: We exposed I/II instar larvae, III/IV instar larvae and pupae of Ae. aegypti, An. stephensi and Cx. quinquefaciatus mosquitoes to UV radiation of 253 nm wavelength in a closed chamber of 30×30 cm. The exposure was done for different time intervals viz. 1, 2, 3, 4 minutes and so on. Development of larvae/pupae to adult stage was monitored daily and mortality, if any, was recorded. Results: Development of I/II instar larvae of Ae. aegypti and Cx. quinquefasciatus to pupal stage was unsuccessful at an exposure time of one minute while only 1.7% pupation occurred in I/II instar larvae of Ae. aegypti upon similar exposure. When III/IV stage larvae were exposed to UV light, pupal development occurred only at 30seconds and one-minute exposure in An. stephensi and Cx. quinquefaciatus but in Ae. aegypti, no pupation occurred with one-minute exposure. With four-minute UV exposure of pupae, no adult emerged in Ae. aegypti; 33.3% adult emerged in An. stephensi and 66.7% adult emerged in Cx. quinquefaciatus. Interpretation & conclusion: Our results show that UV radiation results in developmental arrest of Ae. aegypti, An. stephensi and Cx. quinquefaciatus mosquitoes.

Insecticide susceptibility status of malaria vectors in Himachal Pradesh, India.

BACKGROUND & OBJECTIVES: The state of Himachal Pradesh is one of the hilly forested states of India. Warming of climate has been evidenced in the state due to the ongoing climate change which may cause the upsurge/introduction of mosquito-borne diseases. To curb disease transmission, an effective vector control strategy will be required. METHODS: Insecticide susceptibility status of available malaria vectors was determined using the standard WHO method in six districts Kangra, Una, Mandi, Bilaspur, Solan and Mandi of the state. An. culicifacies and An. fluviatilis were tested against DDT (4%), malathion (5%) and deltamethrin (0.05%) using WHO insecticide susceptibility kits. RESULTS: Overall, An. culicifacies was found resistant to DDT in all the six districts, susceptible to malathion in all districts except Bilaspur and Solan where it showed possible resistance. It was susceptible to deltamethrin in all the study districts. An. fluviatilis was resistant to DDT and susceptible to malathion and deltamethrin in Kangra and Una districts. INTERPRETATION & CONCLUSION: At present, indoor residual spraying (IRS) is not being undertaken in Himachal Pradesh. However, with the information generated through the present study, the state government can plan evidence-based IRS at least for focal spray in limited foci reporting malaria incidence.

Detection of Leishmania donovani in Wild-Caught Phlebotomine Sand Flies in Endemic Focus of Leishmaniasis in Himachal Pradesh, India.

An endemic focus of cutaneous leishmaniasis (CL) is located in the Sutlej River Valley in Himachal Pradesh (India) in the north-western Himalaya where CL co-exists with visceral leishmaniasis (VL). In areas of the Indian subcontinent such as Rajasthan, cutaneous leishmaniasis is transmitted by Phlebotomus papatasi (Scopoli) and Phlebotomus salehi. In Himachal Pradesh, Phlebotomus longiductus (Parrot) is suspected to be the vector for CL. In the current study, sand flies were collected and tested for Leishmania infection and to confirm the vector species causing CL. Sand flies were collected during April and September of 2017-2019 from CL endemic villages of Rampur (Shimla), Nirmand (Kullu) and Nichar (Kinnaur) districts of Himachal Pradesh. The sand flies were identified as Phlebotomus (adlerius) longiductus (Parrot) and Phlebotomus (larrousisus) major (Annandale). The density of P. longiductus was found highest. The elevation of villages ranged from 947 m to 2,130 m and were far from the presence of subsoil water. Field collected sand flies tested positive (7.69%) for Leishmania donovani by PCR-RFLP. The L. donovani sequences detected from P. longiductus were 97% similar to L. donovani sequences reported from the cases of CL in Himachal Pradesh.The Leishmania positive sand flies were morphologically identified as Phlebotomus adlerious longiductus providing one step further evidence towards the vector status of CL in Himachal Pradesh. The findings of the study are of epidemiological significance for strategic planning of vector control for leishmaniasis in India.

El Niño Southern Oscillation as an early warning tool for dengue outbreak in India.

BACKGROUND: Dengue is rapidly expanding climate-sensitive mosquito-borne disease worldwide. Outbreaks of dengue occur in various parts of India as well but there is no tool to provide early warning. The current study was, therefore, undertaken to find out the link between El Niño, precipitation, and dengue cases, which could help in early preparedness for control of dengue. METHODS: Data on Oceanic Niño Index (ONI) was extracted from CPC-IRI (USA) while the data on monthly rainfall was procured from India Meteorological Department. Data on annual dengue cases was taken from the website of National Vector Borne Disease Control Programme (NVBDCP). Correlation analysis was used to analyse the relationship between seasonal positive ONI, rainfall index and dengue case index based on past 20 years' state-level data. The dengue case index representing 'relative deviation from mean' was correlated to the 3 months average ONI. The computed r values of dengue case index and positive ONI were further interpreted using generated spatial correlation map. The short-term prediction of dengue probability map has been prepared based on phase-wise (El Niño, La Niña, and Neutral) 20 years averaged ONI. RESULTS: A high correlation between positive ONI and dengue incidence was found, particularly in the states of Arunachal Pradesh, Chhattisgarh, Haryana, Uttarakhand, Andaman and Nicobar Islands, Delhi, Daman and Diu. The states like Assam, Himachal Pradesh, Meghalaya, Manipur, Mizoram, Jammu & Kashmir, Uttar Pradesh, Orissa, and Andhra Pradesh shown negative correlation between summer El Niño and dengue incidence. Two - three month lag was found between monthly 'rainfall index' and dengue cases at local-scale analysis. CONCLUSION: The generated map signifies the spatial correlation between positive ONI and dengue case index, indicating positive correlation in the central part, while negative correlation in some coastal, northern, and north-eastern part of India. The findings offer a tool for early preparedness for undertaking intervention measures against dengue by the national programme at state level. For further improvement of results, study at micro-scale district level for finding month-wise association with Indian Ocean Dipole and local weather variables is desired for better explanation of dengue outbreaks in the states with 'no association'.

Entomological investigation of an outbreak of Japanese encephalitis in Solan district, Himachal Pradesh.

An outbreak of Japanese encephalitis (JE) was reported in Solan district of Himachal Pradesh, India in May 2018 wherein a total of eight JE cases were reported by the state health department, of which seven cases were confirmed by ELISA. An entomological survey was carried out to investigate the presence of vector mosquitoes in the affected area. Field visits were undertaken in eight villages of two blocks in Solan district. Larval collections were made from the major aquatic sites and emerging mosquito species were identified. Seepage water ditches were the main source of JE vector mosquitoes Culex tritaeniorhynchus and Cx. bitaeniorhynchus. During hand catch collections of adult mosquitoes, three vector species of JE,Culex tritaeniorhynchus (Man Hour Density 1-14), Cx. vishnui (MHD 2) and Cx. bitaeniorhynchus (MHD 1-2) were collected. A few specimens of Cx. tritaeniorhynchus (6 no.) were also collected in light trap collections. Since this was the first reported outbreak of JE from Himachal Pradesh, India, studies on sero-surveillance in addition to bionomics of JE vectors are required for better understanding of epidemiology of JE in Himachal Pradesh. Moreover, there is a need to study the role of climate change especially rising temperature in the context of JE in Himachal Pradesh.

Preparedness for malaria elimination in the wake of climate change in the State of Uttarakhand (India).

BACKGROUND & OBJECTIVES: Climate change is an emerging issue particularly in the context of vector-borne diseases. A study was undertaken in Nainital and Almora districts of Uttarakhand to provide evidences of changing climatic conditions, abundance of vectors, and knocking of malaria in hilly areas. MATERIAL AND METHODS: Longitudinal data on temperature and relative humidity were procured from Tussar Silk Centre, Bhimtal, India as well as generated using HOBO device. Monthly density of malaria vectors, their positivity for sporozoite proteins of malaria parasite and fever surveys were conducted as per the standard procedures from 2010 to 2013. Epidemiological data were procured from the State Programme Officer of Uttarakhand state. RESULTS: It was found that the temperature has increased since 1990 resulting in extension in windows of malaria transmission, temporal distribution as well as man hour density of Anopheles culicifacies and An. fluviatilis in hilly districts of Uttarakhand state. Both the vectors were found in high density up to a maximum man hour density of 110 (An. culicifacies) and 69 (An. fluviatilis) as compared to 32 and 33, respectively during 1998. The field collected vector species were also found positive for sporozoite proteins of malaria parasites in the month of October and November. Evidence of occurrence of malaria cases was also found in areas hitherto free from malaria. INTERPRETATION & CONCLUSION: The findings reveal that Himalayan region needs attention to strengthen surveillance for malaria to identify emerging new foci of malaria transmission in view of climate change. Health education to communities about preventive measures to contain breeding of vectors and seeking timely treatment should be imparted so as to achieve the goal of malaria elimination in category-1 in the first instance.

Control of Aedes aegypti and Ae. albopictus, the vectors of dengue and chikungunya, by using pheromone C21 with an insect growth regulator: Results of multicentric trials from 2007-12 in India.

BACKGROUND & OBJECTIVES: Aedes mosquito control has gained much importance nowadays in view of rise in number of reported cases of dengue and chikungunya in India and other countries. In the present study, C21 attracticide (containing a pheromone and an insect growth regulator­IGR, developed by Defence Research and Development Establishment (DRDE), Gwalior, India was tested for its feasibility for surveillance and control of Aedes mosquito in a multicentric mode from October 2007 to June 2012 in urban (Delhi, and Bengaluru district, Karnataka) and suburban (Alappuzha district, Kerala) settings of the country in three phases. METHODS: Across the randomly selected households in each study area, two to four containers treated with attracticide (experimental) and untreated (control) were placed and monitored by trained surveillance workers on weekly/ fortnightly basis for determining the presence of eggs, larvae and pupae. Container positivity, percent larvae, egg and pupae collected were determined during different phases and analyzed statistically using SPSS 18.0. RESULTS: Container positivity was found statistically significant at Bengaluru and Alappuzha, Kerala while in Delhi, it was found non-significant. Eggs collected from experimental containers were significantly higher in comparison to control at all the locations except Delhi. Also larvae collected from control containers were significantly higher at all the locations except Bengaluru. Pupae collected from control containers remained significantly higher at all the locations as no pupal formation was recorded from experimental containers. INTERPRETATION & CONCLUSION: The use of C21 attracticide hampered pupal formation, thus inhibiting adult population in the study areas. The study established that C21 attracticide was efficacious in the field conditions and has potential for use in surveillance and management of dengue and chikungunya mosquitoes.

A note on the insecticide susceptibility status of principal malaria vector Anopheles culicifacies in four states of India.

BACKGROUND & OBJECTIVES: The major malaria vector, Anopheles culicifacies Giles is reported to contribute ~ 65% of the malaria cases in India. This species developed resistance to DDT and later to HCH, malathion and also to pyrethroids in some states due to their use in the national malaria control programme. In the present study, insecticide susceptibility of this species was monitored in four states of India. METHODS: To determine insecticide susceptibility status of the major malaria vector An. culicifacies, adult mosquitoes were collected from different localities of 32 tribal districts in the states of Andhra Pradesh, Odisha, Jharkhand and West Bengal during October/November 2009-10. Mosquitoes were collected from stratified ecotypes comprising a group of districts in West Bengal and individual districts in three other states. Mosquitoes were exposed to papers treated with WHO diagnostic dose: 4% DDT, 5% malathion and 0.05% deltamethrin following the WHO tube method. RESULTS: RESULTS provided the susceptibility status of An. culicifacies to different insecticides used in the public health programme in 32 districts in four states. An. culicifacies was found resistant to DDT (mortality range 0-36%) in all the 32 districts; to malathion it was resistant in 14 districts, verification required in 10 districts and susceptible in eight districts (mortality range 32.2-100%). It was resistant to deltamethrin in four districts, verification required in 11 districts and susceptible in 17 districts (mortality range 43.3-100%). INTERPRETATION & CONCLUSION: Development of widespread resistance to insecticides used in public health sprays for vector control including to pyrethroids in An. culicifacies in the surveyed districts is of great concern for the malaria control programme as the major interventions for vector control are heavily reliant on chemical insecticides, mainly synthetic pyrethroids used both for indoor residual spraying and for long-lasting insecticidal nets. Thus, there is a need to periodically monitor and update the susceptibility status of malaria vector(s) to suggest alternative vector control strategies for effective disease management.

Retrospective study of chikungunya outbreak in urban areas of India.

BACKGROUND & OBJECTIVES: A retrospective study on chikungunya outbreak in India in five States viz. Delhi, Madhya Pradesh, Orissa, Maharashtra and Kerala was conducted in 2007-2008 to know the distribution and determinants of chikungunya fever outbreak in India. METHODS: On the basis of high and low incidence of chikungunya fever, two districts from each State and two wards from the selected district were taken for random selection of 1000 households from 10 districts and 5 States. Semi-structured questionnaires were administered to individuals, patients, qualified health professionals and to stakeholders for collecting information. RESULTS: The educational background and occupation of the respondents showed variations across the study States. Only in high incidence ward of Maharashtra, water storage period for 3-6 days and emptying, drying of water containers on weekly basis was noted. The study through knowledge, attitude, belief, practice (KABP) obtained individual's perception of chikungunya fever, its prevention and control. Patients' expenditure on treatment was mainly recorded less than Rs 500 across study States. Health facility survey obtained an overview of the capacity of local health facilities. Stakeholders' perception regarding chikungunya fever was also noted. INTERPRETATION & CONCLUSIONS: The study revealed differences in awareness of chikungunya, cause of the disease, vector responsible, mode of transmission, biting time and elimination of breeding of mosquitoes statistically significant among high and low incidence wards of all the States. Expenditure on treatment was independent of economically active status and loss of man-days across all the States. Education and occupation did not have any relation with emptying/drying of water containers in high incidence wards. Strengthening of surveillance, information, education and communication (IEC) activities along with case management facilities may be provided by the State health department for prevention of chikungunya outbreaks in future. Stakeholders should be more involved in outbreak management and future planning.

Anti-malarial activity of some xanthones isolated from the roots of Andrographis paniculata.

Four xanthones were isolated from the roots of Andrographis paniculata using a combination of column and thin-layer chromatographic methods. They were characterized as (i) 1,8-di-hydroxy-3,7-dimethoxy-xanthone, (ii) 4,8-dihydroxy-2,7-dimethoxy-xanthone, (iii) 1,2-dihydroxy-6,8-dimethoxy-xanthone and (iv) 3,7,8-trimethoxy-1-hydroxy xanthone by IR, MS and NMR spectroscopic methods. In vitro study revealed that compound 1,2-dihydroxy-6,8-dimethoxy-xanthone possessed substantial anti-plasmodial activity against Plasmodium falciparum with its IC(50) value of 4 microg ml(-1). Xanthones bearing hydroxyl group at 2 position demonstrated most potent activity while xanthones with hydroxyl group at 1,4 or 8 position possessed very low activity. In vivo anti-malarial sensitivity test of this compound on Swiss Albino mice with Plasmodium berghei infection using Peters' 4-day test gave substantial reduction (62%) in parasitaemia after treating the mice with 30 mg kg(-1) dose. In vitro cytotoxicity against mammalian cells revealed that 1,2-dihydroxy-6,8-dimethoxy-xanthone is non-cytotoxic with its IC(50) > 32 microg ml(-1).

Bionomics of vector anophelines in District Naini Tal, Uttar Pradesh.

Breeding behaviour and seasonal prevalence of vector anopheline in different habitats associated with rice land agroecosystem of terai and bhabar area of District Naini Tal was studied from July 1992 to June 1994. Adult prevalence in both the areas shows two distinct An. fluviatilis peaks in the months of March and October and the breeding places for the species were pokhars in bhabar and stream and irrigation drains in terai. Prevalence of adult An. culicifacies was observed during July to August in bhabar and April and August in terai. In bhabar high immature density of An. culicifacies was noted mainly in tanks, pokhars and paddy fields (early transplantation period). In terai high immature density of An. culicifacies was noted in stream, while low in paddy fields. Higher prevalence of immatures and adult anopheline vectors coincide with peak malaria incidence in both the areas. In bhabar in the months of August and September large number of malaria cases were contributed by An. culicifacies and in November by An. fluviatilis. In terai, malaria cases in April and from June to September were contributed by An. culicifacies, whereas An. fluviatilis might be responsible for transmission in October.

A modified probability model for out-migration.

"In this paper an attempt is made to describe the probability model of the total number of migrants [at the household level]. The suitability of the model is tested through observed data [for India]."