1. Vector independent transmission of the vector-borne bluetongue virus.
- Author
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van der Sluijs MT, de Smit AJ, and Moormann RJ
- Subjects
- Animals, Bluetongue epidemiology, Bluetongue prevention & control, Bluetongue virus classification, Bluetongue virus isolation & purification, Cattle, Europe, Infectious Disease Transmission, Vertical, Sheep, Vaccination, Vaccines, Attenuated, Viral Vaccines immunology, Bluetongue transmission, Bluetongue virology, Bluetongue virus physiology, Disease Vectors
- Abstract
Bluetongue is an economically important disease of ruminants. The causative agent, Bluetongue virus (BTV), is mainly transmitted by insect vectors. This review focuses on vector-free BTV transmission, and its epizootic and economic consequences. Vector-free transmission can either be vertical, from dam to fetus, or horizontal via direct contract. For several BTV-serotypes, vertical (transplacental) transmission has been described, resulting in severe congenital malformations. Transplacental transmission had been mainly associated with live vaccine strains. Yet, the European BTV-8 strain demonstrated a high incidence of transplacental transmission in natural circumstances. The relevance of transplacental transmission for the epizootiology is considered limited, especially in enzootic areas. However, transplacental transmission can have a substantial economic impact due to the loss of progeny. Inactivated vaccines have demonstrated to prevent transplacental transmission. Vector-free horizontal transmission has also been demonstrated. Since direct horizontal transmission requires close contact of animals, it is considered only relevant for within-farm spreading of BTV. The genetic determinants which enable vector-free transmission are present in virus strains circulating in the field. More research into the genetic changes which enable vector-free transmission is essential to better evaluate the risks associated with outbreaks of new BTV serotypes and to design more appropriate control measures.
- Published
- 2016
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