Tropical Medicine and Health Vol. 39 No. 4 Supplement, 2011, pp. 17-27 doi:10.2149/tmh.2011-S04 Copyright 2011 by The Japanese Society of Tropical Medicine Review TMH 9 Dengue Vectors and their Spatial Distribution Yukiko Higa Published online 25 August, 2011 17 © 20A1b1stJraapcat:neTsheeSdoicsiteritbyuotifonTroofpdiceanlguMeevdeicctionres, Ae. aegypti and Ae. albopictus, is affected by climatic factors. In addition, since their life cycles are well adapted to the human environment, environmental changes resulting from human activity such as urbanization exert a great impact on vector distribution. The different responses of Ae. aegypti and Ae albopictus to various environments result in a difference in spatial distribution along north-south and urban-rural gradients, and between the indoors and outdoors. In the north-south gradient, climate associated with survival is an important factor in spatial distribution. In the urban-rural gradient, different distribution reflects a difference in adult niches and is modified by geographic and human factors. The direct response of the two species to the environment around houses is related to different spatial distribution indoors and outdoors. Dengue viruses circulate mainly between human and vector mosquitoes, and the vector presence is a limiting factor of transmission. Therefore, spatial distribution of dengue vectors is a significant concern in the epidemiology of the disease. Current technologies such as GIS, satellite imagery and statistical models allow researchers to predict the spatial distribution of vectors in the changing environment. Although it is difficult to confirm the actual effect of environ- mental and climate changes on vector abundance and vector-borne diseases, environmental changes caused by humans and human behavioral changes due to climate change can be expected to exert an impact on dengue vectors. Longitudinal monitoring of dengue vectors and viruses is therefore necessary. Key words: Aedes aegypti, Aedes albopictus, spatial, distribution, environment, dengue INTRODUCTION Humans have experienced dengue fever (DF) since ancient times. Dengue-like illness was already described in Chinese literature in 992 [1]. Since the early 20th century when experiments showed that dengue virus was trans- mitted by Aedes aegypti (L.), a great number of studies on the relationship between Ae. aegypti and DF have been conducted [2]. Although there are several potential dengue vectors, the field isolation of viruses and epidemiological evidence clearly show that Ae. aegypti and Ae. albopictus are responsible for the majority of dengue transmission [1]. Aedes albopictus (Skuse), better known as the “Asian tiger mosquito”, originates in Orient and serves as a second- ary vector of DF [2]. This species feeds on humans in gardens, parks and bushes around human dwellings in the daytime and is very common in Japan and other Asian countries. After Ae. albopictus was recognized to be a vector of DF in 1931 and dengue virus was isolated from Ae. albopictus caught in the wild, many scientists have taken an interest in this species as well as Ae. aegypti [2]. There is a wealth of studies on the distribution, mor- phology, genetics, biology and ecology of these two major dengue vectors due to their great medical importance. However, the dengue vector situation has completely changed since the 1980’s. World geographic distribution of Ae. albopictus has dramatically shifted as a result of intro- duction of the species from Orient to New World, Europe and Africa by frequent used tire transportations [3]. In addition, recent uncontrolled urbanization in developing countries and global warming, which influence vector mosquitoes and exert an impact on vector-borne diseases, have become topics of concern among scientists. Frequent movement of people by aircraft has resulted in a further introduction of vector mosquitoes to new places. Ae. aegypti and Ae. albopictus were collected from aircraft arriving at Changi International Airport in Singapore [4]. Such vector movement will increase the risk of newly emerging vector- borne diseases. Not only the expansion of dengue vector distribution but also behavioral changes of Ae. aegypti and Ae. albopictus are currently reported. Ae. aegypti, which usually breeds in artificial containers in houses, was found Department of Vector Ecology and Environment, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Sakamoto 1-12-4, Nagasaki city, Nagasaki 852-8523, Japan Tel: +81-95-819-7811 Fax: +81-95-819-7812 E-mail: yukko@nagasaki-u.ac.jp