Mosquito density in rural Kerala: a study on the trend of Aedes larval indices over monsoon in a rural area of Thrissur district, India
Keywords:Container index, House index, Breteau index
Background: Dengue is one of the most rapidly spreading mosquito-borne viral diseases in the world. Aedes aegypti mosquito is the main vector of dengue and Chikungunya. Entomological surveillance on Aedes mosquito has been standardized on different indices like House index, Container index, Breteau index. Larval indices are important predictors of outbreaks and are valuable in taking preventive measures. The objectives of the present study was to study the trend of larval indices over four months in selected wards of Kaiparambu Panchayat, Thrissur, Kerala, India and to identify the major breeding sources.
Methods: A series of surveys were conducted from May to August of 2017 in Kaiparambu Panchayat under the field practice area of Amala Institute of Medical Sciences Thrissur. Houses were selected serially from 4, 5 and 6 wards with roughly 120 houses being covered each month.
Results: A total of 489 houses were surveyed over 4 months. Overall, positive containers (with larvae) were present in 375 of 4055 potential containers showing a calculated House index (HI) is 44.4%, Container index (CI) is 11.5% and the Breteau Index is 76.7%. All three indices increased from May to June, peaked in July and dropped by August. Plastic containers were the most common source of breeding.
Conclusions: The indices indicate risk even in the pre-monsoon season and there is a marked rise during monsoon. Hence, control measures need to be adopted during the pre-monsoon season so as to reduce the impact of the impending outbreak.
The world health report 2004-changing history. Geneva: World Health Organization; 2004. Available at: https://www.who.int/whr/2004/en/. Accessed on 9 April 2019.
A global brief, published on World Health Day 2014, on vector-borne diseases, World Health Organisation, Geneva. Available at: http://www .who.int/campaigns/world-health-day/2014/global-brief/en/. Accessed on 20 July 2019.
Dengue/DHF Situation in India: National Vector Borne Disease Control Programme (NVBDCP). Available at: https://nvbdcp.gov.in/index4.php? Lang=1&level=0&linkid=431&lid=3715. Accessed on 20 July 2019.
Hawley WA. The biology of Aedes albopictus. J Am Mosq Control Assoc. 1988;1:1-39.
World Health Organization, Regional Office for Western Pacific. Guidelines for dengue surveillance and mosquito control. Western Pacific Education in Action series. Manila: WHO-WPRO; 1995: 8.
Comprehensive guidelines for prevention and control of dengue and dengue haemorrhagic fever. Revised and expanded guidelines 2011. WHO SEARO Technical Publication Series No. 60.
Rainfall data for major cities of India. Available at: http://www.rainwaterharvesting.org/rainfall_htm/kochi.htm. Accessed on 20 July 2019.
Menon VTK, Rachel J, Saju CR, Rafi MM, Joshy VM. A study on mosquito density in rural Kerala before and after floods. Int J Comm Med Pub Health. 2019;6(2):659-63.
Jesha M, Sebastian N, Haveri SP, Shabeer MI, Manu AY. Mosquito density in urban Kerala: a study to calculate larval indices in municipal area of Perinthalmanna. Indian J Forensic Community Med. 2015;2(1):7-12.
Samuel PP, Thenmozhi V, Nagaraj J, Kumar TD, Tyagi BK. Dengue vectors prevalence and the related risk factors involved in the transmission of dengue in Thiruvananthapuram district, Kerala. South India J Vector Borne Dis. 2014;51:313-9.
Suganthi P, Govindaraju M, Thenmozhi V, Tyagi BK. Survey of mosquito vector abundance in and around tribal residential areas. J Entomol Zool Studies. 2014;2(6):233-9.
Vijayakumar K, Anish TS, Sreekala KN, Ramachandran R, Philip RR. Environmental factors of households in five districts of Kerala affected by the epidemic of Chikungunya fever in 2007. National Med J India. 2010;23(2):82-4.
Chan KL, Ho BC, Chan YC. Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. Larval habitats. Bull World Health Organ. 1971;44:629-33.
Tsuda Y, Suwonkerd W, Chawprom S, Prajakwong S, Takagi M. Different spatial distribution of Aedes aegypti and Aedes albopictus along an urban-rural gradient and the relating environmental factors examined in three villages in northern Thailand. J Am Mosq Control Assoc. 2006;22:222-8.
Dengue: Sero prevalence of dengue virus infection. WHO Singapore Wkly Epidemiol Rec. 1992;67:99-101.
Tun-Lin W, Kay BH, Barnes A, Forsyth S. Critical examination of Aedes aegypti indices: Correlations with abundance. Am J Trop Med Hyg. 1996;54:543-7.
Kuno G. Review of the factors modulating dengue transmission. Epidemiol Rev. 1995;17:321-35.
Sharma VP. Dengue haemorrhagic fever epidemic in Delhi. Some entomological aspects. Round Table Conference Series: No.1 December 1996, New Delhi, India: Ranbaxy Science Foundation; 1996: 10-3.