Abstract
Culicoides-borne arboviruses of livestock impair animal health, livestock production and livelihoods worldwide. As these arboviruses are multi-host, multi-vector systems, predictions to improve targeting of disease control measures require frameworks that quantify the relative impacts of multiple abiotic and biotic factors on disease patterns. We develop such a framework to predict long term (1992–2009) average patterns in bluetongue (BT), caused by bluetongue virus (BTV), in sheep in southern India, where annual BT outbreaks constrain the livelihoods and production of small-holder farmers. In Bayesian spatial general linear mixed models, host factors outperformed landscape and climate factors as predictors of disease patterns, with more BT outbreaks occurring on average in districts with higher densities of susceptible sheep breeds and buffalo. Since buffalo are resistant to clinical signs of BT, this finding suggests they are a source of infection for sympatric susceptible sheep populations. Sero-monitoring is required to understand the role of buffalo in maintaining BTV transmission and whether they must be included in vaccination programs to protect sheep adequately. Landscape factors, namely the coverage of post-flooding, irrigated and rain-fed croplands, had weak positive effects on outbreaks. The intimate links between livestock host, vector composition and agricultural practices in India require further investigation at the landscape scale.
Highlights
Culicoides (Diptera: Ceratopogonidae) are tiny biting flies that transmit arboviruses of livestock, wildlife and humans
Utilising a substantial dataset of clinical BT outbreaks collected since 1992 by the Indian Council of Agricultural Research’s National Institute for Veterinary Epidemiology and Disease Informatics (NVIEDI), this paper investigates the relative roles of climate, land-use and availability of livestock hosts in driving long-term spatial variation in the severity of BT outbreaks in sheep across districts in South India
We analyse the potential impact of temporal mismatches in our predictor data versus the bluetongue outbreak data on our results
Summary
Culicoides (Diptera: Ceratopogonidae) are tiny biting flies that transmit arboviruses of livestock, wildlife and humans These viruses cause diseases that have a significant impact on animal health and welfare, livestock production, trade and livelihoods[1,2,3]. The emergence of bluetongue virus (BTV: Reoviridae; Orbivirus) and Schmallenberg virus (Bunyaviridae: Orthobunyavirus) in Europe has focussed research effort upon understanding and predicting spatial variability in Culicoides-borne arboviruses in relation to environmental drivers[4,10,11,12,13]. Prior studies of Culicoides-borne disease patterns in tropical endemic areas focussed largely on climatic factors, primarily temperature and rainfall[14]. In addition to mortality (with local case fatality rates of up to 30%19), clinical impacts include weight loss, reductions in wool quality, infertility and lameness Economic costs include those for veterinary treatment, vaccination, surveillance and trade restrictions[20]. Research in Europe has linked vector seasonality and abundance and spread of bluetongue to landscape and host factors alongside climate[29,30,31]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
