12. Seasonal variation in the prevalence of larvae of Aedes aegypti mosquito in district Hyderabad, Sindh, Pakistan

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Mukhtiar Ahmed Channa, Nasreen Memon


Entomological surveillance for the prevalence and seasonal variations of Aedes aegypti (Dengue and Chikungunya vector) mosquito larvae was conducted during July 2016 to June 2017 in district Hyderabad. In the role of being Aedes aegypti as potential vector of Dengue & Chikungunya, arboviral infections commonly prevalent in Lower Sindh. The outcome of study was designed on predictive modeling exercise so that rapid response in terms of larvicidal activity either biological method or mechanical or growth regulation could be implemented at positive localities besides identifying prospective geographical distribution in order to assess future interventions well in time prior to peak season. At onset of surveillance, larvae were collected from various types of indoor and outdoor water holding containers/breeding habitat. underground tanks, overhead tanks, plastic drums, earthen pots, discarded receptacles, plant nurseries, puncture tire shops and road side small hotels (Dhaba). A standard method was used for data collection and analysis (house index HI, container index CI and Breteau index BI). A total of 510 household surveyed with 1370 water holding containers in which 372 were positive with Aedes aegypti larvae at the rate of 27.1%; while 344 outdoor water containers examined, 46 were positive with Aedes aegypti larvae at the rate of 13.37%. Total of 1714 indoor and outdoor water holding containers examined, 418 were positive with Aedes aegypti larvae with overall positivity rate of 24.38 %. For entomological indices only indoor water containers data have been used. House Index (HI), Container Index (CI) and Breteau Index (BI) were estimated as 31%, 27.1 % and 73 % respectively. Drums were recorded with highest positivity rate of (40.17%), followed by underground water tanks (29.07%), overhead water tanks (22.8%), Earthen pot (22.6%), discarded containers (12.1%) and the least (10.7%) dripping water collection from air-condition and refrigerator. From outdoor breeding-sites, Plant nurseries were recorded highest 17.1% followed by Dhaba hotel (15.5%) and puncture tire shops (10.6%). The seasonal variations were noted as September and October were observed the peak seasons with positivity rate of 51.25% and 58.27% respectively and the reason is that the favorable climatic factors after monsoon; 131.8 mm rain fall in August 2016 and the favorable temperature and relative humidity as well for the breeding of Aedes aegypti. Positive water containers were distinguished with ratio as properly covered, partially covered and uncovered1.91%, 49.76% and 48.3%respectively.

Keywords: Aedes aegypti larvae; Breeding-sites; Dengue/Chikungunya Vector; Hyderabad; Larval indices; Prevalence; Seasonal variation


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