Recovery rates of bluetongue virus serotypes 1, 2, 4 and 8 Spanish strains from orally infected Culicoides imicola in South Africa

In June 2006, bluetongue virus, an arboviral pathogen of ruminants, appeared in northern Europe for the first time, successfully overwintered and subsequently caused substantial losses to the farming sector in 2007 and 2008. This emergence served as a test of how the probability of arboviral incursion into new regions is assessed and has highlighted the reliance of decision making on paradigms that are not always underpinned by basic biological data. In this review, we highlight those areas of the epidemiology of bluetongue that are poorly understood, reflect upon why certain vital areas of research have received little attention and, finally, examine strategies that could aid future risk assessment and intervention.

Culicoides biting midges are among the most abundant of haematophagous insects, and occur throughout most of the inhabited world. Across this broad range they transmit a great number of assorted pathogens of human, and domestic and wild animals, but it is as vectors of arboviruses, and particularly arboviruses of domestic livestock, that they achieve their prime importance. To date, more than 50 such viruses have been isolated from Culicoides spp. and some of these cause diseases of such international significance that they have been allocated Office International des Epizooties (OIE) List A status. Culicoides are world players in the epidemiology of many important arboviral diseases. In this context this paper deals with those aspects of midge biology facilitating disease transmission, describes the factors controlling insect-virus interactions at the individual insect and population level, and illustrates the far-reaching effects that certain components of climate have upon the midges and, hence, transmission potential.