Control of the Aedes vectors of the dengue viruses and <I>Wuchereria bancrofti</I>: the French Polynesian experience

Abstract

In most of the 130 islands of French Polynesia, the stenotopic mosquitoes Aedes aegypti (the main local vector for the viruses causing dengue) and Aedes polynesiensis (the main local vector of Wuchereria bancrofti) share many breeding sites in water containers such as discarded cans, coconut shells, buckets and water-storage pots and drums. In addition to selective application of insecticides, non-polluting methods of controlling these mosquitoes have been evaluated during the last decade in two main ecological situations: (1) villages, where Aedes breeding sites are typically peridomestic; and (2) flooded burrows of land crabs, the major source of Ae. polynesiensis throughout the South Pacific region. Large-scale trials of biological control agents, such as mosquito fish (Gambusia affinis and Poecilia reticulata) and copepods (Mesocyclops aspericornis), and of integrated-control strategies have demonstrated the efficacy of certain techniques and control agents against the target Aedes populations in some village situations. Generally, mechanical methods (the use of layers of polystyrene beads against mosquito larvae and pupae, and screening against adult mosquitoes) were more efficient than use of the biological control agents. By integrating several methods of control, mosquito densities (as measured by human-bait collections and larval surveys) were reduced significantly compared with the results of concurrent sampling from untreated villages, and control remained effective for months after the interventions ceased. In land-crab burrows, the first attempts to control Aedes larvae used bacterial agents (Bacillus thuringiensis) and predatory copepods gave disappointing results. Mesocyclops aspericornis could be an effective control agent if the burrows were constantly flooded, but most burrows dry out and refill periodically, so copepod populations do not survive. As it proved difficult to reach all corners of the long sinuous burrows with any control agent, larvicidal (chlorpyrifos-methyl) baits were developed for foraging crabs to carry into their burrows. This novel technique proved to be effective and could become the method of choice for treating crab burrows. Further research is underway to find the optimum (biological or chemical) larvicidal ingredient for the crab bait. Despite the ecological and logistical challenges of controlling the Aedes vectors of the dengue viruses and W. bancrofti in so many scattered islands, the French Polynesian experience indicates that relatively simple methods can be integrated and applied effectively and economically. Operationally, however, success also depends on a strong political commitment and on at-risk communities that are sufficiently motivated to maintain a good level of Aedes control.

Mosquitocidal activity of Solanum xanthocarpum fruit extract and copepod Mesocyclops thermocyclopoides for the control of dengue vector Aedes aegypti

“…Mesocyclops has been studied as an antagonist of mosquito larvae, and its effectiveness has been demonstrated in different countries, including the USA (Marten 1990a, b), Honduras (Marten et al 1994a, b), Vietnam (Nam et al 1998), and French Polynesia (Lardeux et al 2002). This work demonstrates that the predatory efficacy of M. thermocyclopoides is substantial against the different larval instars of Ae.…”

“…Similar investigations have also been done using M. aspericornis in conjunction with other controlling methods and resulting in the eradication of Ae. aegypti (Lardeux et al 2002;Kay et al 1992;Russell et al 1996;Nam et al 1998;Locantoni et al 2006). Bacillus thuringiensis var.…”

“…There are several types of biological control including the direct introduction of parasites, pathogens, and predators to target mosquitoes. Biological control, using the natural enemies of Aedes, appears to be an alternative approach to the systematic failure of use of insecticides (Lardeux et al 2002). Secondly, the synthetic insecticides are toxic and adversely affect the environment by contaminating soil, water, and air.…”

The Copepods (Crustacean: Copepod) and Fish (Osteichthyes) That Inhabit in the Fluvial Ecosystems from Sancti Spíritus Province, Cuba

“…The number of identified individuals in the 90 ecosystems sampled in different years showed a total of 6348 specimens in the year 2000, equivalent to 41, 5% of the collected total (15,260). In 2005, the number increased to 7561, for 49, 5%, meanwhile in 2011, this number decreased rapidly, to only 1351 specimens, for 8, 8%.…”

Zika Outbreak in 2016: Understanding Brazilian Social Inequalities through Urban Spatial Analysis and their Consequences to Health

“…Improvements in public infrastructure and housing are pivotal. Public plans are needed to clarify what kinds of strategic objectives the national health organization would like to achieve and how this can be done in order to prevent the negligence in socio spatial terms and the outbreak prevalence [93][94][95][96][97][98][99].…”