Altering mating rituals to curb disease transmission
If left untreated, visceral leishmaniasis (VL) is fatal, while cutaneous leishmaniasis (CL) is likely to cause facial disfigurement. There are no vaccines currently available. The 'Vector control for visceral and cutaneous leishmaniasis' (VCVCL) project aimed to address EU and World Health Organization (WHO) concerns regarding the implications of these diseases. The overall goal was to commence work on developing a vector control strategy targeting sand flies and thereby disease transmission. In laboratory experiments, researchers set out to determine how males and females of either of the two sand fly species are attracted to each other. Another avenue of research involved ascertaining the age of adult males or females producing sex pheromones and then the age of those shown to be the most responsive to the pheromones. This approach was used to elucidate the role of sex pheromones and enable strategies for using it to curtail disease development. Project partners also aimed to determine where pheromones are produced in the insect and from what distance they are effective in attracting mates. Phlebotomus perniciosus and Phlebotomus papatasi are the sand fly species known to transmit VL and CL. On completion of the project, studies for P. perniciosus revealed that the species does not produce a sex pheromone. VCVCL members therefore completed all work related to their objectives for P. papatasi and clearly showed that these males produce a sex pheromone. A sex pheromone attractive to one-to-three-day-old P. papatasi females is produced by one-to-three-day-old P. papatasi males. In a Tunisia field experiment, researchers were successful in attracting female P. papatasi to traps with small numbers of males and females. Interestingly, females were not attracted to traps with larger numbers of males and females. Results suggest that the sex pheromone is effective up to a distance of at least three metres. Studies were inconclusive in clearly identifying sites of pheromone production in the insect. This prompted the project members to focus on male-female mating interactions in the hope of determining what takes place along the continuum from courtship to mating. The VCVCL project findings are positive for further research into characterising chemical elements of the pheromone that manipulates the behaviour of wild populations of P. papatasi. This information can ultimately be used for developing and exploiting vector control strategies that will reduce disease transmission.
