New entomological sampling method for the surveillance of vector-borne pathogens

Background. Vector-borne diseases account for more than 17% of all infectious diseases, causing more than 1 million deaths annually. Global travel, trade and environmental challenges can affect their transmission, causing the introduction or re-introduction of pathogens in countries where they were unknown or eradicated. Early detection of pathogens in arthropod vectors is highly important in prevention of vector-borne diseases and has the potential of providing the timely indicator of pathogens circulation before reaching humans. Objectives. The aim of this study is to develop a new entomological surveillance approach that can be used in different contexts both of endemic and emerging vector borne diseases areas. For this purpose, we propose a trapping system able to i) detect directly the pathogen circulating in a specific area and preserve pathogen RNA/DNA in samples collected without the need of cooling chain ii) work in autonomy without frequent servicing thus reduce the economic and working effort, an essential feature in remote areas useful also in other contexts. Preliminary results. We have modified a trapping device for mosquito monitoring (BG Sentinel) in which pathogen nucleic acids carried by infected specimens can be preserved for several days at environmental temperature and subsequently molecularly detected. The trap is provided with an artificial feeding system, based on the assumption that it is possible detect pathogens in mosquito saliva released during a sugar meal directly on FTA card soaked with a honey-based solution. We have tested the feeding system in laboratory and successively in the field in an Italian endemic area for West Nile Virus (WNV) in order to evaluate i) the best sugar solution and the feeding rate in mosquitoes ii) the modified BG trap’s efficiency compared with CDC-CO2 trap, commonly used as gold standard in WNV surveillance iii) the mosquito ability to release WNV on the feeder’s card in field conditions iv) the possibility to molecularly detect the virus from the FTA card. Preliminary results confirm the ability of mosquitoes to take a meal on FTA cards, baited with a mixture of honey, hydroxyl-ethylcellulose hydrogel and methylene blue, both in laboratory and field conditions. Also, WNV is detectable in the cards from traps with infected mosquitoes, confirming a sufficient sensitivity of the system for surveillance purposes. Future perspectives. The next step is to validate the system in tropical areas with circulation of different vectors and pathogens, such as Burkina Faso, a sub-Saharan country endemic for malaria.