Abstract
The Asian Tiger mosquito, Aedes albopictus, first appeared in Europe in the 1970s,almost certainly a result ofintercontinental transport of its dessication-resistant eggs. In the laboratory,the species is capable of transmitting 27 viruses including Yellow Fever, dengue, chikungunya and zika, although in the field it is not considered an efficient vector because it is not host-specific.The first objective of our studies was to monitor aspects of the biology of the species in Nice (southeastern France), where it has been established for more than 10 years. Infusion-baited ovitraps, B-G® adult traps and human landing captures were used to reveal seasonal population fluctuations, parous rates and other parameters. In two complete years of study, adult mosquitoes began to appear in April, reached a plateau in July-August and declined thereafter until activity ceased in November. Parous rates were stable from June to October (0,52 to 0,71%) indicating a balance between recruitment (eclosion) and mortality. During this period, daily survival probability was high although this may be an underestimate if the duration of the gonotrophic cycle is extended by skip oviposition. Up to 44% of females captured by landing capture were gravid, confirmation of multiple blood-meals per gonotrophic cycle.The main focus of the work was an assessment of the efficacy of Ultra-low Volume (ULV) space sprays, the principal method used in the event of urban outbreaks. The local population proved highly susceptible to deltamethrin (the only insecticide approved for adult mosquito control in France) although femaleswere significantly less susceptible than males. A comparison of results by topical application and by the WHO tube test confirmed this difference is a function of size. In six separate field trials,there was no evidence of any impact of ULVdeltamethrin on females although there was a significant reduction of males. By contrast, outdoor treatment of a small cluster of homes with a portable thermal fogger gave virtual elimination (ca. 95%) of both sexes.These results are clearly of public health significance.Lastly, the efficacy of several slow-release formulations of microencapsulated insecticide in paint was tested in laboratory and semi-field conditions. Results were encouraging and tests demonstrated that the paints remained effective for 24 months on plastic surface. The ultimate goal was to use paint-treated ovitraps as a control method: in theory, skip ovipositon should ensure a high probability that ovipositing females will make contact with a treated trap on their rounds of suitable oviposition sites. In a small field trial, however, no impact on the wild population was observed. This may have been because too few treated traps were deployed; further studies along these lines could prove worthwhile.