Evaluation of the efficacy of Bistar 80SC by residual application in dengue vectors control in the North of Vietnam

Background: Two species, Aedes aegypti and Aedes albopictus are the main intermediate vectors of transmission of the dengue viruses in Vietnam. Insecticide applications by different methods that may help interrupt the spread of dengue outbreaks. Many different groups of insecticides have been used for dengue vector control. Some recent studies revealed that Aedes vectors obscuring their resistance to insecticides at different levels. Therefore, a new insecticide formula is required for effective dengue vectors control. Objective: To evaluate the efficacy of Bistar 80SC by residual application in suppression of Aedes species in a northern province of Vietnam. Subject and methods: Bistar 80 SC with a component of Bifenthrin 80g/L was evaluated by residual application in suppression of 2 Aedes species in vitro and in an intervention commune of Hien Giang, Thuong Tin district and a control commune of Van Mo, Ha Dong town, Ha Tay province from March, 2004 to June, 2004. Results: WHO Bifenthrin paper test kit was effective at the concentration of 37.5mg/m2 and over with Aedes aegypti vectors ranged from 80% to 100% mortality in the North, In other words, Aedes vector remains susceptible to Bifenthrin in the region. The mortality on wood surface after 60 minutes of exposure to Bistar 80SC at concentrations of 25mg/m2 by using residual application was higher than those on brick walls. Up to 100% Aedes aegypti was killed after 60 minutes in exposure and remains in effect until the end of the third months and one month with Aedes albopictus. No side effects, to the sprayer and humans, livestock and environment caused by Bistar 80SC were reported in the intervention area. Conclusion: Bistar 80SC is suggested as a nominated alternative to effectively control the dengue outbreak by residual application.

Evaluation of the efficacy of cynoff 25 ULV to eradicate aedes species, dengue vectors in Vietnam, 2004

Background: Dengue fever remains a major public health problem in Vietnam. It was transmitted through two main Aedes species, namely Aedes aegypti and Aedes albopictus in which Aedes aegypti played the predominant role in transmitting the dengue viruses (accounted for 94% of the Aedes genus).Different groups of insecticides have been widely used in the community. As a consequence, it increased the resistance level of Aedes vectors to the insecticides. Therefore, a new synthesized insecticide was required for future control and prevention of dengue epidemics. \r\n', u'Objectives: To evaluate the efficacy of Cynoff 25 ULV in suppressing Aedes species in Vietnam. \r\n', u'Subjects and methods: The study was conducted in the entomology laboratory and in the fields of Ha Tay province. ULV spraying was implemented in Hiengiang commune, Thuongtin district, in comparison with a control area, Van Mo commune in Ha Dong town.\r\n', u'Results and conclusions: : Cynoff 25 ULV had a high efficacy that kills over 90% of 2 dengue vector species, namely Aedes aegypti and Aedes albopicctus after 24 hours exposure at the distance of 30 meters from the brass nozzle of a STIHL SR 400 sprayer. In the field trials, Cynoff 25 ULV also had high efficacy in killing Aedes species, e.g. 100% of Aedes species were killed after spraying and the effects lasted for 3 months for Aedes aegypti and one month for Aedes albopictus species. The insecticide had no side-effects or any other adverse effects to humans, livestock and the environment in the intervention areas. \r\n', u'

Prospect of using mesocyclops for dengue vector control in Viet Nam

8 species of Mesocyclops were reported in Viet Nam having wide distribution and existing naturally in certain drinking water containers of inhabitants. Mesocyclops can survive and develop well in normal condition and they are good preditors to the first instar of Aedes aegypti larvae, the major vector of dengue fever/dengue haemorrhagic fever. In the laboratory, a single Mesocyclops can kill first-instar of Aedes acgypti larvae up to 41 by M.rutneri, 37 by M.aspericorms and 31 by M.woutersi in average during 24 hours. In the fields releasing Mesocyclops (to all kind of water containers), population of Aedes aegypti reduced from 91.5% to 100% after 17 months treating and sustaining for months later

Field training active control the hemorrhagic fever vector in T©n Minh commune, Th­êng TÝn district, Hµ T©y province during 1995-1999

Subject 6928 persons in 1454 households, T©n Minh commune, Th­êng TÝn district, Hµ T©y province where the dengue hemorrhagic fever occurred during 1988 -1992. Methods: survey of focus of Aedes aegypti, training, and education for public perception, release of Mesocyclops in the field training and monitoring the vector. Results: the education for enhancement of the public perception, release of mesocyclops and removal of the wasted objects gave the long-term social and economic efficacy. These were easy to implement and can be enlarged to other areas to actively control the epidemic fever/ dengue hemorrhagic fever

Application of Mesocyclops in community for control dengue fever/hemorrhage vector in some locals of ViÖt Nam

Source of Aedes larvae was investigated in 200 households in provinces of Hµ T©y, Thõa thiªn HuÕ, §µ N½ng, Kh¸nh Hßa, Kiªn giang between 1998 - 2000. Mesocyclops were released to water containers and the waste water containers were eliminated. the results showed that in Northern area, mosquito and larvae population reduced by 100% after 13 months of project and maintained for several following months. In Central area, larvae population reduced by 90,7% and mosquito by 39.2% to 71.8%. In southern area, larvae population reduced by 97.7%, mosquito by 92.0% and there was not patient with dengue fever

Mesocyclops species and their potential in killing Aedes aegypti larvae in Vietnam

Mesocyclops were collected from 631 water areas and fresh water containers over 31 provinces and city between 1998 - 1999. It was found 10 species that involved in Mesocyclops gender. Messocyclops distribute widely and are available in fresh water containers in crowded regions. They can reproduce and develop easily under natural conditions. They have high potential in killing Aedes aegypti larvae. Mesocyclops can become an effective biological agent in preventing actively the Dengue fever/Dengue hemorrhage vector in Viet Nam