Bluetongue surviving winter by infecting livestock foetuses
Tuesday, 26 Aug 2008 12:13
Scientists have been looking at how the Bluetongue virus survives winter
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Scientists have come up with a number of hypotheses for explaining how the Bluetongue virus survives winter.
When it first reached livestock in northern Europe in 2006 it was thought that the virus would be killed off during the winter and thereby prevent it from spreading.
However, the virus did survive the winter and in fact escalated the following year.
Scientists from the Institute for Animal Health looked into how the virus survived in the open access journal PLoS Biology.
They claim that the survival may be due to a number of different reasons. In mild winters, such as that of 2006/07 for example, the infected midges may have survived in livestock barns before becoming active again in spring.
Another possibility is that Bluetongue is in fact spread by some susceptible species of long-lived ticks and by the simple mechanical transmission by Melopagus ovinus, a wingless parasite that lives in sheep.
Evidence from Australia also points to the fact that the Bluetongue virus can survive inside midges and cattle for three to four months, enough time to survive the majority of winter.
In northern Europe, it seems that the virus can survive by transplacental infections – spreading from an infected pregnant animal to its foetus. This is a significant phenomenon in cattle due to its nine month gestation period.
Dr Mellor, of the Institute for Animal Health, concludes: "Experiments have revealed a toolbox of possible mechanisms, with the potential to interact with and complement one another."