DS0409 - Émergence et transmission des agents pathogènes, résistances

How ANOpheles Females sEEk maLe? – Anofeel

How ANOpheles Females sEEk maLes?

Basic knowledge of insect mating behavior and a clear understanding of the mechanisms of mate preference was incidental to the development of efficient agricultural pest control. Such knowledge is currently lacking for most arthropod vector species. Here, we propose to fill some of these gaps by addressing for the first time processes involved in female mating behavior in the African malaria mosquito, Anopheles gambiae.

what stimuli are attractive?

Currently, almost nothing is known on Anopheles female pre-copulatory behavior. The objective of this proposal is to identifying stimuli used by virgin females of the An. gambiae complex to detect, recognize and locate species-specific male swarms at long range. Since swarming behavior is expressed during a narrow time window each day and because females mate only once, the ability of females to accurately identify and locate male swarms should be strongly selected for. Thus, females need to use relevant cues allowing them to accurately detect, recognize and locate conspecific swarms. We are investigating the three senses potentially involved in this behavior (i.e. olfaction, vision and audition) and we will screen all potential stimuli usable at long range.

We have adopt a comparative approach using the three main vectors in West Africa (An. coluzzii, An. gambiae and An. arabiensis). Tools from chemical ecology, acoustic and video-tracking are used. We are proceeding with a behavioral ecology approach, using appropriate methodologies to identify attractive stimuli (i.e. isolate stimuli that are detected physiologically by sensory systems and/or that alter behavior). Experiments are performed in the laboratory and extended to semi-field conditions to test the stimuli shown to be the most effective in controlling mating behavior and potentially the most useful for control purposes.

To date, we are able to generate swarms with the three species and to control for their high, location and duration.

Once stimuli will be identified, we can imagine to design bio-inspired traps to control for both females and males mosquitoes (swarms = aggregation behavior)

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Malaria is an infectious disease caused by parasites that are transmitted between people by female mosquitoes, killing 600,000 to 1.2 million people each year. In addition to its lethal aspect, malaria is an impediment to the social and economic development of endemic countries. In Africa, Plasmodium falciparum, the most deadly species of malaria parasites, is responsible for 90% of infections and is transmitted by mosquitoes mainly belonging to the Anopheles gambiae complex. Among them, Anopheles gambiae s.s., An. coluzzii and An. arabiensis are the most widespread vectors throughout sub-Saharan Africa. Current malaria prevention is mainly based on the use of long lasting insecticidal nets (LLIN) and indoor residual sprayings of insecticide (IRS) which target female mosquitoes that enter habitations at night to take a blood meal on its human host. During the past decade, these methods have significantly reduced mortality and prevalence of malaria over large areas of sub-Saharan Africa. Unfortunately, recent data indicate an increase in transmission rates in several countries, highlighting the limitation of both LLIN and IRS efficiency. A main hypothesis regarding this resurgence in malaria is that long-term use of residual insecticides is driving an increase in the prevalence of insecticide resistance mechanisms and changes in mosquito behavior that cause them to avoid contacting insecticide either by blood-feeding predominantly outdoors or in the early evening before people are protected by their treated bed nets. Moreover among the Anopheles species able to transmit malaria parasites, some are exophilic, preferring to bite humans outdoors, thereby evading control measures based on indoor residual insecticides. Thus, vector biodiversity and the high adaptive potential of Anopheles species, make more complex the epidemiological landscape and make the long-term control of these vectors difficult. Current efforts to prevent and control life-threatening mosquito-borne diseases require new and innovative vector control tools.
Because their blood feeding habit is a key behavior in the malaria transmission process, and because it was thought that mosquitoes could be controlled with insecticides, other basic life history traits, behavior and ecology remain deeply unexplored despite their importance to mosquito biology and parasite transmission. Although mating has been one of the most overlooked behaviors, the development of male release strategies to control mosquito populations, such as the sterile insect technique and genetically modified male mosquitoes, highlights the necessity of producing competitive males and has increased the level of interest in male mating behavior in recent years. However, female mating behavior has been greatly neglected, potentially limiting the effectiveness of male release methods, and the range of tools available for new control and monitoring strategies. Basic knowledge of insect mating behavior and a clear understanding of the mechanisms of mate preference was incidental to the development of efficient agricultural pest control. Such knowledge is currently lacking for most arthropod vector species. Here, we propose to fill some of these gaps by addressing for the first time processes involved in female mating behavior in the African malaria mosquito, Anopheles gambiae.
It is known that males form swarms in which females come to find a mate but the way females are attracted to swarms is unknown. Through a multidisciplinary approach, stimuli used by females to locate and recognize male swarms at long range will be identified. Chemical, visual and acoustic signaling will be investigated. Results will help improve vector population suppression/replacement strategies and may prompt the development of new bio-inspired traps for vector surveillance and control.

Project coordinator

Monsieur Olivier Roux (Institut de Recherche pour le Developpement)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IRD - UMR 224 Institut de Recherche pour le Developpement

Help of the ANR 370,000 euros
Beginning and duration of the scientific project: March 2016 - 48 Months

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