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

Abstract

The pathogen transmitting Aedes albopictus mosquito is spreading rapidly in Europe, putting millions of humans and animals at risk. This species is well-established in Albania since its first detection in 1979. The sterile insect technique (SIT) is increasingly gaining momentum worldwide as a component of area-wide-integrated pest management. However, estimating how the sterile males will perform in the field and the size of target populations is crucial for better decision-making, designing and elaborating appropriate SIT pilot trials, and subsequent large-scale release strategies. A mark-release-recapture (MRR) experiment was carried out in Albania within a highly urbanized area in the city of Tirana. The radio-sterilized adults of Ae. albopictus Albania strain males were transported by plane from Centro Agricoltura Ambiente (CAA) mass-production facility (Bologna, Italy), where they were reared. In Albania, sterile males were sugar-fed, marked with fluorescent powder, and released. The aim of this study was to estimate, under field conditions, their dispersal capacity, probability of daily survival and competitiveness, and the size of the target population. In addition, two adult mosquito collection methods were also evaluated: BG-Sentinel traps baited with BG-Lure and CO2, (BGS) versus human landing catch (HLC). The overall recapture rates did not differ significantly between the two methods (2.36% and 1.57% of the total male released were recaptured respectively by BGS and HLC), suggesting a similar trapping efficiency under these conditions. Sterile males traveled a mean distance of 93.85 ± 42.58 m and dispersed up to 258 m. Moreover, they were observed living in the field up to 15 days after release with an average life expectancy of 4.26 ± 0.80 days. Whether mosquitoes were marked with green, blue, yellow, or pink, released at 3.00 p.m. or 6.00 p.m., there was no significant difference in the recapture, dispersal, and survival rates in the field. The Fried competitiveness index was estimated at 0.28. This mark-release-recapture study provided important data for better decision-making and planning before moving to pilot SIT trials in Albania. Moreover, it also showed that both BG-traps and HLC were successful in monitoring adult mosquitoes and provided similar estimations of the main entomological parameters needed.

A bacterium against the tiger: further evidence of the potential of noninundative releases of males with manipulated Wolbachia infection in reducing fertility of Aedes albopictus field populations in Italy

“…albopictus males. 32,38,39 Both 2018 and 2019 C-values are above the 0.2 threshold, which is considered as the lower limit for an effective suppressive impact on the target population in the field. 32 In addition to the above standard approach to assess of viability in eggs laid in ovitraps, we collected single females inside the release area in order to assess the effect of cytoplasmic incompatibility at the individual level rather than in the whole population.…”

“…This value is higher than the C ‐value estimated for 2018 experiments (0.21) and lies in the upper side of the range of C ‐values observed in similar field studies conducted with irradiated Ae. albopictus males 32,38,39 . Both 2018 and 2019 C ‐values are above the 0.2 threshold, which is considered as the lower limit for an effective suppressive impact on the target population in the field 32 …”

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.…”

“…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. For instance, pilot release studies in Germany [ 14 ], Montenegro and Greece [ 44 ] and Albania [ 24 ] relied on outsourced sterile male mosquitoes that were sent from Italy. A method of transport for nonchilled adults was used, but chilled adults were also transported for a period not exceeding 24 h. However, most of the transboundary shipments by air for longer distances will take more than 24 h considering the time it takes for the shipment to be picked up and delivered.…”

“…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.…”