From Surveillance To Control: Evaluation of A Larvicide Intervention Against Aedes aegypti In Brownsville, Texas

Abstract

South Texas is recognized as a potential area for the emergence and re-emergence of mosquitoborne diseases due to recent circulation of Zika, chikungunya, and dengue viruses. During 2017, high Aedes aegypti abundance found in the city of Brownsville, TX, in combination with the previous year's local transmission of Zika virus, triggered the activation of the Texas Department of State Health Services Emergency Mosquito Control Contingency Contract. A contract with the Clarke Environmental and Mosquito Control was a response to control Ae. aegypti, using a ground-based wide-area larvicide spray (WALSe) containing Bacillus thuringiensis israelensis. The WALS application was evaluated through a field-based bioassay and by comparing surveillance data pre-and post-WALS application. The WALS application bioassay demonstrated that the larvicide was effective up to 60 m into the target properties. Additionally, the number of Ae. aegypti captured in traps decreased in the WALS intervention areas compared with the untreated control areas, with an estimated 29% control.

An evaluation of Bacillus thuringiensis israelensis (AM65‐52) treatment for the control of Aedes aegypti using vehicle‐mounted WALS® application in a densely populated urban area of Puerto Rico

“…11 In comparison with another study using vehicle-mounted equipment where the net level of control reported was a 29% reduction of Ae. aegypti in treatment sites, 14 the study in Bayamón showed some improvement of the technique, with 28% and 62% reductions in numbers of Ae. aegypti in treatment sites compared with the control.…”

“…WALS® application of Bti AM65‐52 WDG has been successful for dengue vector and disease suppression in Malaysia 10, 11 and in Key West, Florida 12 . WALS® was also used successfully in Miami, Florida 13 and Brownsville, Texas 14 during the Zika crisis of 2016. Therefore, in an effort to find a solution that can be applied to entire communities at speed and at scale, a trial was launched in Puerto Rico to test the effectiveness of applying Bacillus thuringiensis israelensis ( Bti ) AM65‐52 WDG (VectoBac® WDG, Valent Biosciences LLC) using vehicle‐mounted WALS® across multiple areas in the island's urban environments to control Ae.…”

“…The inspiration for this study came as a result of the success of wide-area larvicide spraying in other locations. [10][11][12][13][14] Because Puerto Rico has a very different type of architecture from other parts of the USA reflecting more the Latin American style of small yards, properties located closely together, having flat roofs and high security often meaning access to back yards is limited, it was necessary to determine whether this type of larvicidal application was appropriate for control of Ae. aegypti in neighborhoods on the island.…”

Variable coverage in an Autocidal Gravid Ovitrap intervention impacts efficacy of Aedes aegypti control

“…The AGO has been shown as an efficient surveillance and control tool in Puerto Rico and has reduced chikungunya virus incidence in humans (Sharp et al, 2019). Before wide implementation of this tool by vector control programmes in other regions, its evaluation based on community acceptance, field operational performance and overall efficiency for both surveillance and control, needs to be assessed under different local settings (Garcia-Luna et al, 2019;Gunning et al, 2018;Lenhart et al, 2020). The AGO has been shown to be a cost-effective tool for the surveillance of adult A. aegypti in both San Antonio (Obregón et al, 2019) and the Lower Rio Grande Valley (LRGV) region (Martin et al, 2019) in South Texas.…”

Susceptibility of South Texas Aedes aegypti to Pyriproxyfen

“…In the Lower Rio Grande Valley (LRGV) of South Texas, we completed several studies on Ae. aegypti to better understand ecological and social aspects of this mosquito vector [ 4 , 5 ] and to evaluate control tools under local settings [ 6 ]. Our research team will conduct an intervention study of Ae.…”