Field Performance Assessment of Irradiated Aedes albopictus Males Through Mark–Release–Recapture Trials With Multiple Release Points

Abstract

Mark–release–recapture (MRR) trials have been conducted in Northern Italy to evaluate the capacity of radio-substerilized Aedes albopictus males to survive, disperse, and engage in mating in the field. Two MRR sessions with the human landing collection method (HLC) were conducted with the simultaneous release of irradiated males marked with four different pigment colors. The survival and dispersal rates seem to be influenced more by environmental factors such as barriers, shading, and vegetation rather than weather parameters. In this study, we confirmed a positive linear relationship between the sterile adult male’s daily survival rate and the relative humidity previously reported in similar experimental conditions and a different dispersal capacity of the released A. albopictus males in low- (NDVI index <0.4) and high (NDVI index >0.4)-vegetated areas. Consistent with previous studies, A. albopictus males have their maximal dispersion in the first days after release, while in the following days the males become more stationary. The similar field performances obtained with marked and unmarked radio-sterilized and untreated A. albopictus males on similar environments confirm the negligible effects of irradiation and marking procedures on the quality of the males released. The similar sterile to wild (S/W) male ratio measured in high- and low-vegetation areas in the release sites indicates a similar distribution pattern for the wild and the released sterile males. According to the MRR data collected, the Lincoln index estimated different A. albopictus mean population densities in the study areas equal to 7,000 and 3,000 male/ha, respectively.

From the Lab to the Field: Long-Distance Transport of Sterile Aedes Mosquitoes

“…The success of the technique relies on a high survival rate and quality of released sterile males, which also help in reducing the production cost. The cost reduction may also rely on the use of optimal tools and protocols for mass production [ 29 , 41 , 42 ], optimal irradiators and irradiation doses [ 31 ], quality control [ 30 , 33 , 43 ] and also the release strategy in the field [ 24 , 25 , 26 ]. Most published studies relating to field work rely on irradiated mosquitoes that were produced and delivered at field sites either as pupae that need time to emerge and are kept for a small number of days prior to release or as adults ready to be released.…”

“…Marking using fluorescent powders is a common technique for externally marking adult mosquitoes [ 18 , 19 , 20 , 21 ]. This is to help assess multiple biological parameters, including population size, dispersal, mating and survival [ 22 , 23 , 24 , 25 , 26 ]. However, the interactions between the shipping/transportation, chilling and marking of sterile male mosquitoes has not yet been documented.…”

A Mark-Release-Recapture Study to Estimate Field Performance of Imported Radio-Sterilized Male Aedes albopictus in Albania

“…This MRR study was conducted in September only (the end of mosquito season), and the total trapped area was only 250 m of ray which constitutes the main limitations of the study. However, based on the cost-effectiveness of the SIT program and the available data on such MRR studies ( Caputo et al, 2021 ; Lacroix et al, 2009 ; Balestrino et al, 2022 ), we believe that the design limit of 250 m seems reasonable to measure the main parameters needed for testing the SIT. Although it provides important insights on the overall performance of the released sterile males, their dispersal and survival in the field as well as the size of the wild population can vary over time during the mosquito season due to variation in environmental conditions.…”

“…Although of importance, it was, however, not feasible in the present mark-release-recapture study since only the local strain can be released in the study area and there is no biological marker to differentiate non-marked released mosquitoes from the wild ones in order to compare their dispersal and longevity. A recent study conducted in northern Italy ( Balestrino et al, 2022 ) on Ae. albopictus under the same rearing and climate conditions but released in the summer (July–August) without long-distance transportation has shown a lower recapture rate (0.27%–1.7%) and PDS 65.4% ± 11.5% to 80.0% ± 6.4%).…”

A sterile insect technique pilot trial on Captiva Island: defining mosquito population parameters for sterile male releases using mark–release–recapture

“…Once the containers had been removed from the refrigerator, adults hanging from the sides were gently dislodged by tapping. Sterile males were dusted with fluorescent powder (~ 1.6 g/15 containers) using a nasal aspirator which blew the powder inside the container to create a cloud that evenly settled on the immobilized mosquitoes, similarly to Balestrino et al [ 34 ]. To ensure that large clusters of dye did not adhere to the males, the aspirator bulb was inserted into a fine mesh bag so that the powder was aerosolized.…”