Pyrethroid genetic resistance in the dengue vector (Aedes aegypti) in Posadas, Argentina.

Pyrethroids are extensively used to control adult populations of the arboviral vector Aedes aegypti, raising concerns regarding the increasing frequency and distribution of insecticide resistance mutations (kdr: knock-down resistance) in the voltage-gated sodium channel gene (Nav). The widespread use of pyrethroids imposes a threat to the success of mosquito control and the environment. In this study, we investigated the presence of two kdr mutations (V1016I and F1534C) in the Nav gene and their distribution across four neighborhoods in Posadas, Argentina, with different Ae. aegypti abundance and contrasting socioeconomic status (SES). Alleles at each locus were interrogated using TaqMan SNP genotyping assays in DNA extracted from adult females collected in a longitudinal study. We report the presence of both pyrethroid resistance alleles (kdr 1016I = 29.08%; kdr 1534C = 70.70%) among adult females. The frequency of combined kdr genotypes reveals that approximately 70% of local adult females have enhanced resistance to pyrethroids. Both, the proportion of resistant adult females (with at least one kdr allele in each locus) and Ae. aegypti abundance showed an uneven distribution between neighborhoods with different SES (p < 0.001). In high-SES neighborhoods, we found more mosquitoes and a higher frequency of pyrethroid resistance, possibly as a consequence of different public health interventions, social habits, and insecticide use. This is the first report of kdr mutations in Ae. Aegypti in the northeast region of Argentina. Our results focus on the need for within-population (city) distribution analyses of kdr mutations and highlight the relevance of incorporating insecticide resistance monitoring within the Integrated Vector Management initiative.

Field Worker Evaluation of Dengue Vector Surveillance Methods: Factors That Determine Perceived Ease, Difficulty, Value, and Time Effectiveness in Australia and Malaysia.

This qualitative study aimed to describe field worker perceptions, evaluations of worth, and time costs of routine dengue vector surveillance methods in Cairns (Australia), Kuala Lumpur and Petaling District (Malaysia). In Cairns, the BG-Sentinel trap is a favored method for field workers because of its user-friendliness, but is not as cost-efficient as the sticky ovitrap. In Kuala Lumpur, the Mosquito Larvae Trapping Device is perceived as a solution for the inaccessibility of premises to larval surveys. Nonetheless, the larval survey method is retained in Malaysia for prompt detection of dengue vectors. For dengue vector surveillance to be successful, there needs to be not only technical, quantitative evaluations of method performance but also an appreciation of how amenable field workers are to using particular methods. Here, we report novel field worker perceptions of dengue vector surveillance methods in addition to time analysis for each method.

Dengue vector surveillance and control in Hong Kong in 2008 and 2009.

Dengue vector surveillance programmes were implemented in the community and port areas in Hong Kong Special Administrative Region. Aedes albopictus was the only Aedes vector detected and its distribution was extensive in various areas during the summer months. Aedes aegypti was, however, not detected in any area under surveillance. For community surveillance, the monthly ovitrap indices (MOI) of 2008 and 2009 followed a similar trend as in previous years but were generally lower. The highest ovitrap index recorded in 2008 and 2009 was 37.5% and 48.3% respectively, which were much lower than the highest recorded of 70.9% in 2007. Only two surveyed areas in 2009 had ovitrap indices greater than 20.0% for more than two consecutive months, which was more often seen in 2007. Improvement in the dengue vector situation in the past two years could be attributed to the swift response of the agencies concerned upon getting information on surveillance results via the geographic information system. The public was also informed of the results regularly through the Internet and press releases to create awareness to prevent and control the dengue vector. Health education programmes targeted at different organizations/parties were arranged to promote knowledge about dengue vector prevention and control.

Dengue vector surveillance in Hong Kong – 2007.

A dengue vector surveillance programme was implemented in the city and port areas in Hong Kong. Asa result of the surveillance, only Aedes albopictus was detected to be present in various areas in summer.Aedes aegypti was, however, not detected in any area under surveillance. Although a rather high indexof 70.9% was recorded in July, the activity of Ae. albopictus was immediately brought down through concerted efforts of varies agencies and the public. The swift response of concerned agencies werefacilitated by the use of Geographic Information System (GIS) in the dissemination of surveillance results. Users were able to access the system at any time for the latest results of the surveillance for takingimmediate remedial measures. The public was also informed of the results regularly through theInternet and press releases to arouse awareness to prevent and control the local dengue vector.