Exploring Conditions for Handling Packing and Shipping Aedes aegypti Males to Support an SIT Field Project in Brazil.

The sterile insect technique (SIT) application, as an alternative tool for conventional mosquito control methods, has recently gained prominence. Nevertheless, some SIT components require further development, such as protocols under large-scale conditions, focusing on packing and shipping mosquitoes, and considering transporting time. Immobilization of Aedes aegypti males was tested at temperatures 4, 7, 10, and 14 °C, and each temperature was assessed for 60, 90, and 120 min. The recovery after 24 h was also studied. Chilled and control-reared males had comparable survival rates for all conditions, although 4 °C for 120 min impacted male survival. The male escape rate was affected after 60 min of exposure at 4 °C; this difference was not significant, with 24 h of recovery. First, we defined the successful immobilization at 4 °C for 60 min, thus enabling the evaluation of two transportation intervals: 6 and 24 h, with the assessment of different compaction densities of 100 and 150 mosquitoes/cm3 at 10 °C to optimize the shipment. Compaction during simulated mosquito shipments reduced survival rates significantly after 6 and 24 h. In the mating propensity and insemination experiments, the sterile males managed to inseminate 40 to 66% for all treatments in laboratory conditions. The male insemination propensity was affected only by the highest compaction condition concerning the control. The analysis of the densities (100 and 150 males/cm3) showed that a higher density combined with an extended shipment period (24 h) negatively impacted the percentage of inseminated females. The results are very helpful in developing and improving the SIT packing and shipment protocols. Further studies are required to evaluate all combined parameters' synergetic effects that can combine irradiation to assess sexual competitiveness when sterile males are released into the field.

Transgenic Aedes aegypti Mosquitoes Transfer Genes into a Natural Population.

In an attempt to control the mosquito-borne diseases yellow fever, dengue, chikungunya, and Zika fevers, a strain of transgenically modified Aedes aegypti mosquitoes containing a dominant lethal gene has been developed by a commercial company, Oxitec Ltd. If lethality is complete, releasing this strain should only reduce population size and not affect the genetics of the target populations. Approximately 450 thousand males of this strain were released each week for 27 months in Jacobina, Bahia, Brazil. We genotyped the release strain and the target Jacobina population before releases began for >21,000 single nucleotide polymorphisms (SNPs). Genetic sampling from the target population six, 12, and 27-30 months after releases commenced provides clear evidence that portions of the transgenic strain genome have been incorporated into the target population. Evidently, rare viable hybrid offspring between the release strain and the Jacobina population are sufficiently robust to be able to reproduce in nature. The release strain was developed using a strain originally from Cuba, then outcrossed to a Mexican population. Thus, Jacobina Ae. aegypti are now a mix of three populations. It is unclear how this may affect disease transmission or affect other efforts to control these dangerous vectors. These results highlight the importance of having in place a genetic monitoring program during such releases to detect un-anticipated outcomes.

Oviposition preference of Ceratitis capitata (Diptera: Tephritidae) at different times after pruning 'Italia' table grapes grown in Brazil.

Studies investigating oviposition preference of Ceratitis capitata (Wiedemann, 1824) in table grapes (Vitis vinifera L.) cultivated in the São Francisco River Valley can provide important information to guide control measures, therefore minimizing damage caused by this species in the region. The aim of this study was to evaluate the oviposition preference of C. capitata females for berries cv. 'Italia' collected at five different times (60, 70, 80, 90, and 100 d after production pruning [DAPP]), representing five grapevine growth stages. We also assessed the performance of immature stages of C. capitata regarding the physiological development of the berry. The total soluble solid content was significantly higher in berries at more advanced physiological developmental stages (90 and 100 DAPP). Conversely, these berries showed the lowest values of firmness and titratable acidity. With the onset of physiological development, the average number of punctures per berry increased and reached 5.2 per berry in 100 DAPP berries. The infestation level and pupal weight showed a positive correlation with the growth stage. The highest recovery of pupae was observed in 100 DAPP berries (1.54). Pupal viability values ranged from 50.9 to 64.7% independent of berry maturity stage. The physiological developmental stage of the berry did not affect offspring sex ratio. Results obtained suggest that regardless of the female preference for laying eggs on berries in a more advanced physiological developmental stage, females can initiate the attack to bunches of this cultivar at 60 DAPP, even if the berries have unfavorable physicochemical parameters for oviposition and development of larvae.

Mass production of genetically modified Aedes aegypti for field releases in Brazil.

New techniques and methods are being sought to try to win the battle against mosquitoes. Recent advances in molecular techniques have led to the development of new and innovative methods of mosquito control based around the Sterile Insect Technique (SIT)(1-3). A control method known as RIDL (Release of Insects carrying a Dominant Lethal)(4), is based around SIT, but uses genetic methods to remove the need for radiation-sterilization(5-8). A RIDL strain of Ae. aegypti was successfully tested in the field in Grand Cayman(9,10); further field use is planned or in progress in other countries around the world. Mass rearing of insects has been established in several insect species and to levels of billions a week. However, in mosquitoes, rearing has generally been performed on a much smaller scale, with most large scale rearing being performed in the 1970s and 80s. For a RIDL program it is desirable to release as few females as possible as they bite and transmit disease. In a mass rearing program there are several stages to produce the males to be released: egg production, rearing eggs until pupation, and then sorting males from females before release. These males are then used for a RIDL control program, released as either pupae or adults(11,12). To suppress a mosquito population using RIDL a large number of high quality male adults need to be reared(13,14). The following describes the methods for the mass rearing of OX513A, a RIDL strain of Ae. aegypti (8), for release and covers the techniques required for the production of eggs and mass rearing RIDL males for a control program.