Behavioural response of the house mosquitoes Culex quinquefasciatus and Culex pipiens molestus to avian odours and its reliance on carbon dioxide.

How Culex (Diptera: Culicidae) mosquitoes select and discriminate between potential avian hosts is critical for understanding the epidemiology of West Nile virus. Therefore, the present authors studied the behavioural responses of Culex quinquefasciatus (Say) and Culex pipiens molestus (Forsskål) to headspace volatiles of three avian species [chicken and pigeon (sexes analysed separately), and magpie], presented either alone or in combination with 600 p.p.m. carbon dioxide (CO2 ). The attraction of Cx. quinquefasciatus to the headspace volatiles of both sexes of chicken, and of female pigeon, in combination with CO2 was significantly higher than that achieved by the CO2 and solvent control. Although Cx. p. molestus was attracted to headspace volatiles of chickens and magpies, it was repelled by those of female pigeons when combined with CO2 . An increased effect between the avian volatiles and CO2 was observed for Cx. quinquefasciatus, whereas the addition of CO2 had no effect on the attraction of Cx. p. molestus females. The results of this study demonstrate that Cx. quinquefasciatus and Cx. p. molestus are attracted to the odour of potential avian hosts. Future studies aimed at identifying the bioactive volatile compounds in the headspace of chickens may contribute to the potential development of effective surveillance and control tools against Culex species.

Courtship behaviour of Phlebotomus papatasi the sand fly vector of cutaneous leishmaniasis.

BACKGROUND: The sand fly Phlebotomus papatasi is an Old World vector of Leishmania major, the etiologic agent of zoonotic cutaneous leishmaniasis. This study describes the courtship behaviour of P. papatasi and compares it with that of Lutzomyia longipalpis, the New World vector of visceral leishmaniasis. Understanding the details of courtship behaviour in P. papatasi may help us to understand the role of sex pheromones in this important vector. RESULTS: P. papatasi courtship was found to start with the female touching the male, leading him to begin abdomen bending and wing flapping. Following a period of leg rubbing and facing, the male flaps his wings while approaching the female. The female then briefly flaps her wings in response, to indicate that she is willing to mate, thereby signaling the male to begin copulation. Male P. papatasi did not engage in parading behaviour, which is performed by male L. longipalpis to mark out individual territories during lekking (the establishment and maintenance of mating aggregations), or wing-flap during copulation, believed to function in the production of audio signals important to mate recognition. In P. papatasi the only predictor of mating success for males was previous copulation attempts and for females stationary wing-flapping. By contrast, male L. longipalpis mating success is predicted by male approach-flapping and semi-circling behaviour and for females stationary wing-flapping. CONCLUSIONS: The results show that there are important differences between the mating behaviours of P. papatasi and L. longipalpis. Abdomen bending, which does not occur in L. longipalpis, may act in the release of sex pheromone from an as yet unidentified site in the male abdomen. In male L. longipalpis wing-flapping is believed to be associated with distribution of male pheromone. These different behaviours are likely to signify significant differences in how pheromone is used, an observation that is consistent with field and laboratory observations.

Synthetic sex pheromone attracts the leishmaniasis vector Lutzomyia longipalpis (Diptera: Psychodidae) to traps in the field.

Improving vector control remains a key goal in reducing the world's burden of infectious diseases. More cost-effective approaches to vector control are urgently needed, particularly because vaccines are unavailable and treatment is prohibitively expensive. The causative agent of American visceral leishmaniasis (AVL), Leishmania chagasi, Cunha and Chagas (Kinetoplastida: Trypanosomatidae), is transmitted between animal and human hosts by blood-feeding female sand flies attracted to mating aggregations formed on or above host animals by male-produced sex pheromones. Our results show the potential of using synthetic pheromones to control populations of Lutzomyia longipalpis Lutz and Neiva (Diptera: Psychodidae), the sand fly vector of one of the world's most important neglected diseases, AVL. We showed that a synthetic pheromone, (+/-)-9-methylgermacrene-B, produced from a low-cost plant intermediate, attracted females in the laboratory. By formulating dispensers that released this pheromone at a rate similar to that released by aggregating males, we were able to attract flies of both sexes to traps in the field. These dispensers worked equally well when deployed with mechanical light traps and inexpensive sticky traps. If deployed effectively, pheromone-based traps could be used to decrease AVL transmission rates through specific targeting and reduction of L. longipalpis populations. This is the first study to show attraction of a human disease-transmitting insect to a synthetic pheromone in the field, showing the general applicability of this novel approach for developing new tools for use in vector control.

Courtship behaviour in the sandfly Lutzomyia longipalpis, the New World vector of visceral leishmaniasis.

Courtship behaviour in Lutzomyia longipalpis Lutz and Neiva (Diptera: Psychodidae) was examined to determine the sequence of behaviours that occur prior to copulation. Courtship consisted of a series of male and female touching and wing-flapping behaviours, with males performing a greater variety of wing-flapping behaviours than previously described. Occurrence of male approach-flapping, semi-circling and female stationary-flapping were all predictors of eventual copulation, and may coincide with the dispersal of pheromones or the production of auditory signals important to courtship. Touching occurred in the majority of observations, with contact most often made with the tips of the legs and antennae. This behaviour, not previously described in sandflies, was initiated by males and females, and may indicate the use of contact pheromones, a form of communication previously overlooked in L. longipalpis. Future studies are required to separate the auditory and chemical signals associated with wing-flapping, and to confirm whether L. longipalpis possesses cuticular hydrocarbons capable of inducing behavioural responses. The identification of signals that inhibit sexual behaviour during courtship may be particularly relevant to developing mating disruption techniques against L. longipalpis.

Host odor synergizes attraction of virgin female Lutzomyia longipalpis (Diptera: Psychodidae).

The sand fly Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae) is the principle vector of Leishmania chagasi/infantum Cunha and Chagas, the causative agent of visceral leishmaniasis. The disease is transmitted by blood-feeding females, which seek aggregations of males above potential hosts both to mate and blood-feed. Pheromones produced by male sand flies could potentially be used as lures in L. longipalpis control programs. We investigated whether attraction of male and female sand flies to pheromone could be increased by addition of host odor. Pheromone was attractive to females in the absence of host odor, although a 10-fold increase in concentration did not increase numbers attracted or reduce the proportion of flies not responding during trials. Odors from Syrian hamsters, Mesocricetus auratus, were more attractive to females than air when presented without sex pheromone, but this effect was masked by hexane, suggesting attraction to host odor alone may be relatively weak. Addition of hamster odor both increased the number of virgin female L. longipalpis attracted to sex pheromone (relative to a solvent control) and reduced the number of nonresponders, indicating that host odor may have both a synergistic and activating effect. Male sand flies were not attracted to pheromone with or without host odor, although addition of pheromone did counteract an apparent avoidance of host odor combined with a hexane control. These results indicate L. longipalpis pheromones function primarily to attract females and that their efficacy as lures may be increased through addition of host odor, or by deploying traps in the vicinity of host animals.

Haemoparasites of common shrews (Sorex araneus) in Northwest England.

The presence of haemoparasites belonging to the taxa Anaplasma, Bartonella and Trypanosoma was determined among 76 common shrews (Sorex araneus) from Northwest England. Anaplasma phagocytophilum DNA was recovered from the blood of 1 shrew (1.3%), with the amplified 16S rRNA sequence identical to one previously reported from a bank vole (Clethrionomys glareolus). Trypanosoma spp. DNA was detected in 9 shrews (11.8%), the amplified 18S rDNA fragments being indistinguishable from one another, and distinct from previously published data. This represents the first report of trypanosome infection in S. araneus and suggests they are susceptible to an uncharacterized Trypanosoma species. Blood from 11 shrews (14.5%) yielded Bartonella spp., with characterization of isolates using comparative sequence analysis of partial gltA and 16S-23S rRNA intergenic spacer regions revealing 2 different genotypes. Phylogenetic inference from alignment of partial gltA sequences found that both UK S. araneus types formed a well-supported cluster with Bartonella sp. isolated from S. araneus in Sweden. No significant effect of host age, sex, or year of collection was found on prevalence of Bartonella or trypanosome infections. The results of this survey demonstrate that common shrews in the UK are susceptible to haemoparasitic infections, at prevalences similar to those reported from sympatric rodents.