From mathematical models, vector survival and length of the period between successive blood meals are known to be major determinants of the probability of arbovirus transmission ( Gubbins et al., 2008 and Macdonald, 1957)

and, in Culicoides, both parameters are impacted (in opposite directions) by temperature. A lack of reliable and straightforward age grading techniques for the Culicoides genus as a whole has meant that the proportion of autogenous females surviving to produce a click here third egg batch is not reliably known for C. impunctatus. Preliminary studies conducted on other autogenous Culicoides worldwide ( Kettle, 1977 and Mirzaeva, 1974), however, suggest this proportion is small (4–5% for the first anautogenous cycle) and may preclude high rates of arbovirus transmission. A second major argument against C. impunctatus sustaining person-to-person transmission of arboviruses lies in uncertainty regarding the degree of ecological separation from urban or semi-urban human populations. ABT-263 nmr The populations of C. paraensis responsible for OROV transmission appear to be unique within the genus worldwide in exploiting

semi-urban habitats in close proximity to areas of high human density with few alternative feeding opportunities. Coincidence of C. impunctatus larval habitats and human population density in Scotland remains poorly characterized, but it appears that this species is less closely associated with these areas than C. paraensis in epidemic areas of Brazil, although sustained biting in garden habitats within Scotland does occur. While wide-scale surveys have been conducted for this species across Scotland ( Purse et al., 2012), these were largely aimed at defining presence on farms in the role of transmitting BTV and no standardized attempt has been made to understand human contact rates in semi-urban or urban areas. A third potentially limiting

factor in epidemics driven over by C. impunctatus is their relatively short seasonal appearance as adults in comparison to C. paraensis, which in Brazil can be active throughout the year ( Hoch et al., 1990). Peak C. impunctatus activity occurs during May and June when measured by landing rates on humans ( Service, 1969), by collections from black cloth hung at dusk ( Hill, 1947) and from suction or light-suction trap surveys ( Blackwell et al., 1992, Holmes and Boorman, 1987, Service, 1968 and Takken et al., 2008). While a second peak of C. impunctatus activity during September has been recorded in Scotland, suggesting the production of two broods per year ( Blackwell et al., 1992), there is evidence that the adult population is also curtailed earlier than that of C. obsoletus ( Holmes and Boorman, 1987).