A sound trap for Aedes albopictus (Skuse) male surveillance:Response analysis to acoustic and visual stimuli.

Aedes albopictus (Skuse) is one of the most invasive mosquito species capable of transmitting various harmful pathogens to humans. Failure of vector control strategies against this species requires the development of new effective vector control methods. Among the alternative genetic control measures under development, the sterile insect technique (SIT) is today receiving a renewed interest as a possible effective tool to be integrated in an area-wide pest management approach. The monitoring of the abundance, distribution, movements and ratio of released sterile and wild fertile males is a fundamental requirement for the successful management of any pest control activities integrating an SIT component. Although several traps exist for adult female mosquito surveillance and population control, effective methods to monitor large quantities of non-biting males were less researched in the past and more difficult to obtain. In this study we analyzed the response of A. albopictus males to various sound stimuli produced with different volumes and frequencies in association with visual cues for the optimization of male catches. The production of modulated frequencies continuously varying within the typical female sound emission range (500-650Hz) showed the best results for a sound pressure level between 75 and 79dB measured at the speaker level. The black color of the trap, however, seems decisive to attract males in the vicinity of sound traps and the combined effect produced by these stimuli is additive. We also observed that males increase their response to acoustic stimulation up to 4days of age and then show a continuous and progressive decline of their sound responsiveness. A plastic sound trap prototype capable of producing the most effective sound stimuli tested at laboratory conditions showed a good A. albopictus males' attractiveness in the field despite a reduced use of color stimuli. The use of sound stimuli therefore appears to be a promising prospect to increase the capture rate of A. albopictus males in new or in already existing mosquito traps.

Guidelines to site selection for population surveillance and mosquito control trials: a case study from Mauritius.

Many novel approaches to controlling mosquito vectors through the release of sterile and mass reared males are being developed in the face of increasing insecticide resistance and other limitations of current methods. Before full scale release programmes can be undertaken there is a need for surveillance of the target population, and investigation of parameters such as dispersal and longevity of released, as compared to wild males through mark-release-recapture (MRR) and other experiments, before small scale pilot trials can be conducted. The nature of the sites used for this field work is crucial to ensure that a trial can feasibly collect sufficient and relevant information, given the available resources and practical limitations, and having secured the correct regulatory, community and ethical approvals and support. Mauritius is considering the inclusion of the sterile insect technique (SIT), for population reduction of Aedes albopictus, as a component of the Ministry of Health and Quality of Life's 'Operational Plan for Prevention and Control of Chikungunya and Dengue'. As part of an investigation into the feasibility of integrating the SIT into the Integrated Vector Management (IVM) scheme in Mauritius a pilot trial is planned. Two potential sites have been selected for this purpose, Pointe des Lascars and Panchvati, villages in the North East of the country, and population surveillance has commenced. This case study will here be used to explore the considerations which go into determining the most appropriate sites for mosquito field research. Although each situation is unique, and an ideal site may not be available, this discussion aims to help researchers to consider and balance the important factors and select field sites that will meet their needs.

Effects of static magnetic fields on growth of Paramecium caudatum.

Little is known about the influence of magnetic fields on growth of primitive eukaryotes such as the ciliate Paramecium. The latter are known to exhibit interesting characteristics such as electrotaxis, gravitaxis, and membrane excitability not commonly encountered in higher organisms. This preliminary study reports the effects of static magnetic fields on growth of Paramecium caudatum. The microorganisms were either permanently or 24 h on-and-off exposed to North and South polarity magnetic fields of average field gradient 4.3 T/m, for a period of 96 h. The growth rate and lag phase of all exposed populations were not significantly different from control ones exposed to normal geomagnetic field (P > .05). However, a significant negative shift in t(max) (time taken for maximum growth) of 10.5%-12.2% and a significant decrease (P < .05) in population size of 10.2%-15.1% during the 96 h of experimental conditions were recorded for exposed populations compared to control. Our results suggest that magnetic fields, irrespective of polarity and exposure period reduce Paramecium growth by triggering early senescence of the population. The mechanisms underlying the small changes in population growth are unknown at this level, but various hypotheses have been suggested, including disorganization of swimming patterns resulting from (i) changes in cell membrane electric potential due to high speed movement through a gradient magnetic field and (ii) thermodynamic effect of anisotropic magnetic energies on cell membrane components affecting functioning of calcium channels. Altered swimming movements could in turn affect highly orchestrated processes such as conjugation, essential for survival of the organisms during development of adverse environmental conditions as thought to occur in the closed culture system used in this study.