Recent distribution of vector mosquitoes and epidemiology of the diseases they transmitted in Taiwan

Abstract

In Taiwan, the important mosquito-borne diseases include Japanese encephalitis (JE), dengue, and malaria, in which only JE is known as an endemic disease at present. This paper updates the current status of these disease vectors and pathogen activities to evaluate the disease risk. Since 2004, small to medium dengue outbreaks (202-2000 cases) have occurred annually, mostly in southern Taiwan where Aedes aegypti (L.) distributes. Occasionally, small outbreaks (smaller than 20) occurred in other areas without the presence of Ae. aegypti. Dengue virus infection in local vector population was detected sympatrically with the human cases in the same outbreak. JE cases have occurred sporadically after the introduction of vaccination program since 1968. The predominant species was Culex tritaeniorhynchus Giles (93.9%), followed by Cx. fuscocephala Theobald (3.4%), and Cx. vishnui Theobald (2.6%). Overall population densities were high, with the highest number of 37,440 per trap-night. JE virus was active in mosquito populations during May and June. The distribution of Anopheles minimus Theobald was limited to a few villages at the foothills of southern and eastern Taiwan. The highest numbers of An. minimus adults trapped per trap-night were between 23 and 206 in 6 villages. Chikungunya infection has been found in the travelers from endemic countries since 2007. In conclusion, the threat of these mosquito-borne diseases is increasing because of the frequent introductions of pathogens and the high densities of disease vectors in Taiwan.