Wats, Meenu and Maansi
Dengue and Chikungunya are the vector borne disease (VBDs) whose viruses are transmitted by infested female Aedes mosquito to human beings. The major vector species are Ae. aegypti, Ae. albopictus and Ae. vitattus whose occurrence and abundance shows a direct correlation with the prevalence of the diseases, especially in urban areas which are found as preferable abodes by these vectors. The present study aims to investigate the correlation between changing climatic conditions (temperature and humidity), the population dynamics of three vector species of Aedes mosquito along with the incidences of Dengue and Chikungunya in Chandigarh (U.T.) and its two satellite towns. During the period of investigation (monsoon and post monsoon seasons 2015- 2016) increasing trends in the annual average temperature and humidity was observed, which favored the breeding of all the three species of Aedes. The House Index value was found increased from 23.22% to 50% and Container Index from 17.5% and 44% during the period of investigation. The differential population of three species was studied and was correlated with the incidences of Dengue and Chikungunya in the area under study.
Keywords: Aedes, Dengue | Chikungunya | Vector borne diseases | Climatic factors
Introduction
The mosquito borne diseases mainly hit the human population of tropical and sub-tropical countries because of the naturally available favorable climate for the vectors to flourish. About 2.5 Billion people, throughout the world are at the risk of Dengue (Thangamathi et al., 2014): Out of which, Asia contributes 70% of this global burden of which one third (34%) is shared by India (Kristie L. Ebi, 2016): Mosquitoes act as vector for number of diseases to mankind and animals such as Malaria, Japanese Encephalitis (JE), Lymphatic Filariasis (LF), Eastern Equine Encephalitis (EEE), St. Louis Encephalitis (SLE), West Nile Virus (WNV), Yellow Fever (YF), Brain Fever, Dengue, Chikungunya, etc. (Jaswanth et al., 2002) of which India is facing medical and economical threat from five main diseases viz. Malaria, Japanese Encephalitis, Lymphatic Filariasis, Dengue and Chikungunya.
In India the reports of Dengue and Chikungunya are available since 1950 and 1960 respectively but the severity of Dengue has increased manifold in the last two decades and that of Chikungunya since 2006. The National Vector Borne Disease Control Programme (NVBDCP, 2013) had reported that dengue has been endemic in 16 states and UTs since the beginning. The Chikungunya virus seems to be re-emerged in 2006 after a gap of 32 years in India and has reported 18639 of Chikungunya along with 74454 cases of Dengue till 2013 (Cecilia, 2014):
Dengue (DENV) and Chikungunya virus (CHIKV) has been reported to be transmitted worldwide by Ae. aegypti, acting as the primary vector (Vincent et al., 1998 and William et al., 2002) and Ae. albopictus as secondary vector of Dengue and Chikungunya in Asia, Africa and Europe (Gratz, 2004 and Carrieri, 2011): Ae. vittatus has also been reported as a potential vector of Chikungunya and Yellow Fever (Mawlouth Diallo, 1999; Kumar et al., 2013 and Ali et a.l, 2014): In nature DENV maintain itself by human-mosquito-human cycle where Ae. aegypti remains preferable host but the mutant forms of Ae. albopictus under experimental conditions show equal efficacy to act as the vector of the same virus.
It has been observed that mosquitoes in general breed in wide variety of habitats but the breeding of Aedes has been primarily confined to natural as well as manmade containers filled with freshwater (Service 1995 and Banerjee et al., 2013): The different species of Aedes do show slight demarcation in the selection of their breeding sites. Ae. aegypti prefers artificial water containers while Ae. Albopictus breed both in manmade as well as natural containers viz. hollow bamboo stalks, tree holes, leaf axils, tanks, pools, streams and discarded and unattended containers (Pemola et al., 2005): Ae. vittatus favors pot holes, discarded tires, empty coconut shell, latex collecting containers, abandon earthen pots, rain or irrigated water filled plant pot, plastic container and tank, tree hole etc. for their breeding (Jomon, 2009):
Globalization, urbanization, demographic change, inadequate domestic water supplies, along with increasing temperatures and humidity are associated with the spread of the main vectors like Ae. aegypti, Ae. albopictus and Ae. vittatus (Murray et al., 2013 and Thangamathi et al., 2014):
This study was undertaken to investigate the various breeding sources and distribution of three species of Aedes, role of temperature and humidity in their population dynamics and their correlation with the prevailing cases of Dengue and Chikungunya in Tricity in 2015-2016 time span.