Dipterous haematophagous insects occurring in Dehradun district and its adjoining areas in Uttarakhand, India

Haematophagous dipterans belonging to 10 genera - Aedes (12), Anopheles (14), Armigeres (01), Culex (09), Toxorhynchites (01), Uranotaenia (01), Sergentomyia (02), Phlebotomus (01), Atylotus (01) and Tabanus (03) were encountered from 12 localities under 6 blocks of Dehradun district (Uttarakhand) during January 2011 to December 2012. The Culicines (50.69%) were more dominant than the Anophelines (38.9%), Toxorhynchites (1.72%), horse flies (6.63%) and sandflies (2.01%). The following species viz., Toxorhynchites splendens and Phlebotomus argentipes have been recorded for the first time while Aedes pseudotaeniatus as reappeared species from the study area. Species diversity is represented through Species richness (S), Shannon index (H) and Shannon Eveness (E) among Aedes, Anopheles, Culex, Sandfly and Horsefly. The species richness (S) and evenness (E) were found as 12, 0.65; 14, 0.84; 09, 0.74; 3, 0.61 and 4, 0.78 respectively by Aedes, Anopheles, Culex, Sandfly and Horsefly. Highest Shannon index was shared by Anopheles (2.214) followed by Culex (1.639), Aedes (1.631), Horsefly (1.085) and Sandfly (0.672) in succeeding order.

Reappraisal on anopheline mosquitoes of Garhwal region, Uttarakhand, India.

BACKGROUND & OBJECTIVES: The study examines occurrence of anopheline mosquitoes in seven districts--Dehradun, Pauri, New Tehri, Hardwar, Rudraprayag, Chamoli and Uttarkashi of Garhwal region in Uttarakhand state, India. METHODS: The methodological approach comprised sampling and processing of adult/immature mosquitoes, data compilation, meteorological information and parasitological survey. RESULTS: A total of 87 localities covering 24 tehsils/blocks were surveyed during January 2000 to December 2005 for mosquito sampling. The study encountered 18 species of anophelines including three malaria vectors namely Anopheles culicifacies, An. fluviatilis and An. stephensi collected from Kalsi, Dehradun City, Sahaspur, Hardwar town, Roorkee, New Tehri town and Kotdwar localities. An. pallidus has been recorded for the first time from the Garhwal region. All the collected species have been presented with particular reference to their both adult and immature distribution, brief account of bionomics and some ecological notes. INTERPRETATION & CONCLUSION: Out of 18 collected anopheline species, 15 were non-vectors and they were found to create nuisance to the inhabitants. As far as the species distribution was concerned the diversity was more at elevation between 150 and 1000 m above the mean sea level, while the immature of some species were not recovered from those localities where their adults were collected. Certain species of Anopheles were climate determined and their distribution was localized while some others were cosmopolitan.

Climatic variables and malaria incidence in Dehradun, Uttaranchal, India.

BACKGROUND & OBJECTIVES: Mosquito-borne diseases particularly malaria and Japanese encephalitis (JE) are becoming most dreaded health problems in Dehradun district. Keeping in view that the climatic factors particularly temperature and rainfall may alter the distribution of vector species--increasing or decreasing the ranges, depending on weather conditions that are favourable or unfavourable for mosquito breeding, it is aimed to find out the effect of climatic factors on malaria incidence with particular emphasis to capture the essential events as a result of climatic variability. METHODS: Mosquito sampling and identification was done using WHO entomological methods and follow-up of recognised keys and catalogues. Data on malaria incidence and meteorological information were gathered in a collaborative study with the District Malaria Office, and the Forest Research Institute, Dehradun respectively. Pearson's correlation analysis was applied for establishing relationship between climate variables and malaria transmission. RESULTS: Higher positive correlation of association was found between monthly parasite incidence and climatic variables (temperature, rainfall and humidity). However, highest significant correlation was found between rainfall and malaria incidence (r = 0.718, p < 0.0001) when the data were staggered to allow a lag of one-month. INTERPRETATION & CONCLUSION: Climatic variables that predict the presence or absence of malaria are likely to be the best suited for forecasting the distribution of this disease at the edges of its range.

Relationship between Anopheles fluviatilis & A. stephensi (Diptera: Culicidae) catches & the prevalence of malaria cases at Kalsi area in Dehradun district (Uttaranchal).

BACKGROUND & OBJECTIVE: Though the relationship between mosquito density and transmission of malaria in different regions of the country is known, no studies are available on the relationship between mosquito catches and malaria cases in Kalsi area of Dehradun district in Uttaranchal. Hence, the present study was done to evaluate the role of anopheline mosquitoes catches and prevalence of malaria cases in this area. METHODS: During three consecutive years (2000-2003) mosquitoes were collected from 10 villages in Kalsi area twice a month, during the morning and evening hours. Identification of anopheline mosquitoes was done. Indoor collected female mosquitoes were dissected to see infection. Sporozoites were fixed and stained. Data on temperature and rainfall were also collected. RESULTS: As many as 10 species of anophelines were collected during three consecutive years - January 2000 to December 2002 at Kalsi block in district Dehradun (Uttaranchal). Proportion of the total anopheline species as well as the abundance of Anopheles stephensi was found more in the year 2002 than in 2000 and 2001. Incrimination studies revealed malarial infection (sporozoite positive) in A. fluviatilis and A. stephensi. Of the 5450 blood smears examined, only 50 (0.91%) were found positive for malarial parasite i.e., Plasmodium vivax. There was no case of P. falciparum during the study period. Highest slide positive rate (SPR) of 1.107 per cent was recorded in 2002 while in 2001, highest month-wise malaria positive cases were recorded in the month of August. September shared highest positive cases during 2000 and 2002. While correlating a relationship between mosquito catch especially infected ones and monthly parasite incidence, the density of A. stephensi showed significantly high correlation (r = 0.819; P<0.001). A slight variation in this type of relationship was seen in A. fluviatilis. Both temperature and rainfall were found to be positively correlated with malaria incidence. INTERPRETATION & CONCLUSION: Our findings showed that A. fluviatilis and A. stephensi played a significant role in transmission of malaria in Kalsi area of Dehradun.

Habitat biodiversity of mosquito richness in certain parts of Garhwal (Uttaranchal), India.

The present study gives an overview of data on the habitat biodiversity of mosquitoes occurring in certain parts (viz, Pauri, Tehri and Uttarkashi) of Garhwal (Uttaranchal), India. The study was based on the mosquito sampling in 450 sites/spots in all the 3 districts, each spot having an area of 25 km2 and geographically located at varying altitudes between 300 to 3,000 m. While compiling the data, published sources in the recent past were also considered. The species richness was categorized as most species and least species by estimating the top and least 5 percentile of species density in each grid cells/spots, respectively. Our database showed that the area harbors 45 species from 3 genera. As many as 17 species of Anopheles and 15 species of the genus Aedes were recorded during November 2000 to October 2002. Further, there were 13 species of Culex, besides few specimens that could not be identified correctly because of damage body parts. Collected species of Anophelines were grouped as common, uncommon, and rare species depending to their percentage of occupying in grid cells/spots. There were 9 common species, while the number of rare species and uncommon species were 3 and 5, respectively. The sites/ spots nearer to riverine areas or thick-forested areas showed more diversity of mosquitoes than those nearer to non-forested or thin-forested areas. However, the biodiversity rich spots were up to 1,200 m altitudes.

Altitudinal distribution of mosquitoes in mountainous area of Garhwal region: Part-I.

BACKGROUND & OBJECTIVES: Mosquito fauna diversity in mountainous areas of Garhwal region was studied during November 2000 to October 2002 to correlate the altitudinal vegetation and distribution of mosquitoes. METHODS: Adult mosquitoes and mosquito immatures were collected using WHO methods and identified using standard keys and catalogues. Altitude of mosquito habitat was measured using portable altimeter and also by GPS. RESULTS: Altogether 34 species in five genera--Aedes, Anopheles, Armigeres, Culex and Uranotaenia were encountered in the present study in the altitude range of 300 to 2000 m. Majority of the mosquitoes were found in between 300 to 900 m altitude except Culex vagus and Anopheles maculatus, which were found throughout the range. INTERPRETATION & CONCLUSION: The mosquitoes were categorised into six groups based on their altitudinal distribution. The areas at lowest elevation were having the greatest number of species but not the corresponding greater number of specimens in the present study.