Environmental Risk Mapping for Dengue Fever Transmission in a Rural Area, Tamil Nadu

Dengue is a systemic viral infection transmitted between humans by Aedes mosquitoes. Dengue is a viral infection which originates from mosquitoes. Dengue is caused by a virus called the dengue virus (DENV). Most notably, there are four major DENV serotypes. Therefore it is possible to be diseased by either four or all four of them. As seen in most cases, DENV infections usu-ally cause a mild infection, but it can also lead to an acute (cid:977)lu-like illness. Occa-sionally this proliferates into a possibly deadly problem, called severe dengue. The Detection and mapping of Dengue risk areas is a multifaceted, tiring, com-plicated and extended task requiring evaluation of many criteria. It is not sure that always one single factor is liable for Dengue Fever transmission in all areas, but it differs with changing geographical location. The main objective of the present study is to prepare an environmental risk mapping for dengue transmission in a rural area, Tamil Nadu and access the level of risk the people of that area are in and how susceptible they are to dengue. A total of 40 houses were observed for risks of dengue using a questionnaire and by look-ing around the house for possible hotspots after screening for inclusion and exclusion criteria. There is hence a need for educational programs to facilitate awareness and promote sensible practices to avoid dengue. Every individual should also follow precautionary guidelines taking into consideration the risk dengue. This study serves to spotlight the possible current risk in contracting dengue due to poor household habits and lack of awareness in a rural area.


INTRODUCTION
One of the most common arboviral diseases passed to human beings from mosquito vectors is Dengue fever (DF) belonging to the genus Aedes (Gubler and Monath, 1988); the key factors affecting the spread of this virus include mixing virus serotypes, the vulnerability of human populations and mosquito density (Kuno, 1997).
The only manner to control this deadly virus is to impose vector control as there is no vaccine or precis treatment; this invariably places greater importance on prediction and identi ication of possible risk areas to assist in dengue prevention (Bohra and Andrianasolo, 2001).
There are many parameters and reasons to determine the reasons for the expansive rise of dengue. These include growth of human population, nature of vectors, the biology of population, the natural course of the history of the virus, human actions against nature and many more. In terms of environmental factors, rainfall, temperature, humidity are well-known determinants that can affect various developmental phases of dengue vector thereby limiting the occurrence of DF (Wet et al., 2001;Getis et al., 2003;Hales et al., 2002).
The goal of effective and ef icient risk assessment can be achieved by a broader-scale and prognostic point of view which asses risk that is not only about the already sampled areas but also expanded to new, unsampled areas analytically and logically (Arboleda et al., 2009). The study of risk mapping is one of the components used to evaluate the risk patterns of health care practitioners as well as recommends necessary changes in the living conditions to provide the best environment to the patient. Thereby risk mapping studies are an essential indicator to judge the quality and standard of living among individuals of a speci ic area. The current study is aimed to analyze the living conditions of people of a rural area and evaluate the risks of dengue in that region. This will help us gain knowledge on the prevalence of dengue in that locality and inally assessing the trend of dengue cases.

Aims and Objectives
To determine the household and environmental risk factors for dengue transmission in a rural area, Chennai.

Study Design
Cross-sectional Study.

Study Duration
The study was conducted for a period of 3 months, starting from Jan 2020 to March 2020.

Study Participants
Adult above 18yrs who will be available at the household

Study Area
The study was conducted in Mappedu, Tamilnadu

Sample size
All the 40 houses from the three different streets near the rural health Centre were included in the study.

Study Tool and Data Collection
A Pre-tested, validated, structured and self -administered questionnaire consisting of their sociodemographic details, assessment of environmental factors of household and assessment of potential breeding sources. Data were obtained from each house after rigorous scrutiny and careful examination, accessible areas were thoroughly covered. Epicollect 5 was used to collect relevant data.

Informed consent
It was obtained from all the study participants before eliciting the desired information.

Inclusion criteria
All houses in a particular location were included in the study.

Exclusion criteria
The study participants who didn't give proper responses to speci ic questions.

Ethical clearance
The study was carried out after getting approval from the Institutional Ethics Committee. Permission to carry out the study was also obtained from the Head of Community Medicine Department before starting the study.

Socio-demographic details of study participants
Totally 40 houses were included in this study after screening for inclusion and exclusion criteria. Majority of the study participants were female (82.5%) and between the age of 41-50 (22.5%) or 51-60 (27.5%). The educational quali ications of the personnel surveyed are as follows, 2 (5%) have no formal schooling, 9 (22.5%) have primary schooling, 22 (55%) people have a high school education, 5 (12.5%) have completed higher secondary, and 2 (5%) have completed graduate or higher.

Assessment of environmental factors of household
The type of loor in most houses is mostly divided into Hard loor and Earth loor. There are 18 (45%) living on a hard loor and 22 (55%) living on Earth loor. All families involved in the study are living on the ground loor. There are some houses with a second loor mainly used a roof to keep water tanks. The source of water is a tube well/bore pipe for   Table 2).

Assessment of potential breeding sources
Next, the results of the breeding sites and mosquito infestation was compiled. In-water storage tanks, there was neither mosquito nor larva breeding (0%) found. The same holds for the air cooler except for a small one family (2.5%) found a mosquito in the area, but there was still no larva breeding (0%). Drum had a wide range of results. 28 (70%) of drums were found not to have larva or mosquitos. 12 (30%) of drums were found to have mosquitos, of which 7 (58.3%) were found to have larva and 5 (41.7%) did not have larva. Used tires did not give any signi icant data as there was neither mosquito nor larva breeding 0 (0%) found. The same situation was found in potted plants as there was neither mosquito nor larva breeding 0 (0%) found. The same issue was found in animal food container as there was neither mosquito nor larva breeding 0 (0%) found. In discarded junk, the mosquito absent is found to be 25 (62.5%) and 15 (37.5%) found to have mosquito. Of the 15 (37.5%), 8 (53.3%) had larva present and 7 (46.7%) had larva absent. In discarded food and drink containers, 57.5% were found to be absent of mosquito. 42.5% were found have mosquito infestation, of which 76.5% were found to devoid of the larva and 23.5% were found to have larva. In disposable cups/glasses, 57.5% were absent of mosquito, and 42.5% were found to have mosquito and larva breeding (0%) found. In tree holes, 2 (5%) were found to have mosquitos, and 38 (95%) were absent of mosquitos and larva breeding 0 (0%) found. The same was found in fruit shells, 2 (5%) were found to have mosquitos, and 38 (95%) were absent of mosquitos and larva breeding 0 (0%) found. In rock holes, only 1 (2.5%) were found to have mosquitos, and 39 (97.5%) were absent of mosquitos, and larva breeding 0 (0%) found. In shoot of palm/ coconut leaves, there was neither mosquito nor larva breeding 0 (0%) found. (Table 3)

Distribution of breeding spots
The map depicts the number of households where breeding spots are present or absent. The red dots represent the households with breeding spots present, and the green spots represent the households without any breeding spots ( Figure 1). There are 11 (27.5%) of households without any breeding spots and 29 (72.5%) of households with breeding spots.

Distribution of breeding spots
The graph depicts the distribution of the various breeding spots. Air cooler, tree holes, fruit shells and rock holes are seen only in 1 (2.5%) household. The most commonly seen breeding spot is disposable cups which is seen in 23 (57.5%) households. The next most common is discarded food containers which are seen in 17 (42.5%) households, followed by discarded junk which is seen in 15 (37.5%) households (Graph 1).

DISCUSSION
As mentioned by Arboleda, S et al. (2009), arti icial containers are a signi icant breeding spot for dengue mosquitos. This is similar to the data obtained by us as there is a clear majority of households where arti icial containers such as discarded junk (37.5%), Discarded food containers (42.5%) and disposable cups (57.5%) account for most of the breeding spots. This can be attributed to the low socio-economic status and education background of the individuals in the vicinity. They lack the proper knowledge and practices to prevent the breeding of mosquito in their households. A proper campaigning and knowledge sharing session will bene it the people of the area by decreasing the possibility of mosquito infestation and in turn, decrease the cases of dengue in that area. (Getachew et al., 2015) further emphasize on the storage of water in containers such as the drum is due to the irregular supply and stockpiling of water for future use. When this water is left unattended for long periods leads to potential mosquito breeding as seen in our study where there is a good number of households (30%) where mosquito breeding was seen in the drums. As mentioned by (Bhat and Krishnamoorthy, 2014) who associated insuf icient rainfall and long-term storage of water in containers, it further proves evidence to the fact that stockpiling water over a long period can be attributed to an elevated risk of dengue infestation. (Snr et al., 2011) and (Bhat and Krishnamoorthy, 2014) stress the importance of removing waterilled containers kept over a while as a manner to eliminate mosquito breeding. (Philbert and Ijumba, 2013;Hiscox et al., 2013) suggest that the proper coving of water-holding containers is a very good practice to prevent stagnant water retention and mosquito breeding. (Snr et al., 2011;Bhat and Krishnamoorthy, 2014;Thete and Shinde, 2013) greatly emphasis on the need of both awareness and knowledge of the residents on dengue mosquito breeding. This can be implemented by conducting a public health education to increase awareness and highlight the seriousness of mosquito breeding and diseases associated with it. By slowly reducing various ecological and household factors associated with mosquito breeding, we can reduce the risk of dengue infection ultimately.

CONCLUSIONS
In the area of Mappedu, we can identify the potential mosquito breeding in various households. The lack of knowledge and awareness is a crucial factor that has contributed to the identi ication of potential breeding spots. Prolonged water storage without proper covers can also be attributed as a critical factor in the potential breeding spots. We have mapped out the potential risky households with a variety of factors indicating the danger that these households could face. These breeding spots are not only potential risky spots for dengue but also other mosquitoborne diseases such as malaria. A detailed and simple awareness and health program can help in the long run in the ight against dengue.