Does Aedes albopictus (Diptera: Culicidae) play any role in Usutu virus transmission in Northern Italy? Experimental oral infection and field evidences

This study evaluated the vector competence of Aedes albopictus in transmitting USUV after oral infection under laboratory conditions. Ae. albopictus showed a low vector competence for USUV, although the positive body sample found with a very high number of viral copies at one week post infection indicates that a replication in the mosquito body can occur, and that USUV can escape the midgut barrier. Field data from an extensive entomological arboviruses surveillance program showed a relevant incidence of Ae. albopictus USUV positive pools in the period 2009–2012 while all pools were negative from 2013 on. No conceivable explanation regarding this field evidence was addressed, suggesting that attention must be paid to the trend of development of this vector-pathogen association, being aware of the potential rapid arbovirus’ adaptation to new vectors, to prevent possible new disease’s emergence.