Domestic and Environmental Factors of Chikungunya-affected Families in Thiruvananthapuram (Rural) District of Kerala, India

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Abstract

Background:

The world is experiencing a pandemic of chikungunya which has swept across Indian Ocean and the Indian subcontinent. Kerala the southernmost state of India was affected by the chikungunya epidemic twice, first in 2006 and then in 2007. Kerala has got geography and climate which are highly favorable for the breeding of Aedes albopictus, the suspected vector.

Aim:

The aim of the study was to highlight the various domestic and environmental factors of the families affected by chikungunya in 2007 in Thiruvananthapuram district (rural) of Kerala. Settings and design:This is a cross-sectional survey conducted in Thiruvananthapuram (rural) district during November 2007.

Settings and design:

This is a cross-sectional survey conducted in Thiruvananthapuram (rural) district during November 2007

distribution of the species (Ae. albopictus) showed strong ecological adaptability.[3]

Subsequently in 2006, an outbreak developed in India affecting at least 213 districts in 15 states of the country.[4] The viral strain responsible for this outbreak was of the same lineage (African genotype) as that in the Reunion island outbreak whereas previous outbreaks in India had involved an Asian genotype.[5] The primary vector in the 2006 outbreak is thought to be Ae. albopictus. The previous focal outbreaks were generally associated with high densities of Ae. aegypti.

Kerala was affected twice by the chikungunya epidemic, first in 2006 and then in 2007. Alappuzha and Thiruvananthapuram were the two districts extensively affected by the first epidemic in Kerala. The outbreak was confined to the coastal region. The second attack in 2007 was more extensive and the geographical location shifted to the plantation areas on the eastern side.[6] Kottayam, Pathanamthitta, Kollam, and Thiruvananthapuram (east) were the heavily hit districts.

Many studies from the pandemic affected areas all over the world including Kerala suggested the Ae. albopictus species as the major villain.[6] Kerala has got geography and climate which highly favor breeding of Ae. albopictus, which is thought to breed in natural water collections. Rubber plantations with its latex containers, cocoa plantations, and pineapple plantations in the high land add to the burden.[7] The geographical and ecological factors of the state is such that the eastern high ranges have high humidity and rainfall[8] which will in turn support the breeding of mosquitoes. At the same time, the urban type of dwellings, plastics, and water scarcity provide favorable indoor breeding sites for the endophilic, Ae. aegypti[9] in the coastal belt.

The aim of the study is to find out the domestic and environmental factors of chikungunya-affected households in Thiruvananthapuram (rural) district of Kerala during the 2007 epidemic.

The cluster sampling technique was used to collect the information. It was decided to include 6 clusters each having 23 houses. Field areas of health workers were selected as clusters. Six sub-centers from each primary health center were randomly selected (lot method). Twenty-three houses from each sub-center area were arbitrarily included in the study.

A structured questionnaire was used for data collection. The questionnaire was prepared under the guidance of the epidemiologists, entomologists, and sociologists in the Department Of Community Medicine, Medical College, Thiruvananthapuram. We had to resort to the syndromic approach for case detection because of resource constraints. The content validity of the questionnaire was assessed with the help of the faculty in the department. The major domains of the questionnaire were housing-related parameters (e.g.: location, walls, roof, etc), mosquito breeding-related information (e.g. presence and nature of containers, breeding, perceived mosquito menace, etc) and practice of mosquito control.

The case definition of chikungunya used was an attack of joint pain affecting more than one joint with the appearance of fever within a period 2 days prior to and 2 days after the onset of joint pain. The case definition was developed based on the investigation of chikungunya epidemic carried out by the faculty during the early phase. This case definition has a sensitivity of 88% and a specificity of 50.4% compared to IgM ELISA test for chikungunya.[11] The Junior Health Inspectors and Junior Public Health Nurses in selected sub-centers were briefed regarding the correct usage of the questionnaire. The health workers were asked to collect information from 138 houses under each health center (over all sample size of 414). They collected information from 528 houses altogether. The questionnaires were collected back after verifying all the entries. The data regarding all the 528 houses were entered and included in the study. As the study dealt with the domestic and environmental factors related to the outbreak, houses were considered as sampling units.