EFSA believes that as SBV appears to be transmitted by insects, its spread is highly dependent on temperature, meaning more animals could get infected starting in May. “If the disease is spread by insects, the temperature is a key factor as it determines the phases of insects’ activity. [Summer] is when the vectors are assumed to be active (April to November) and the experts looked at the earliest possible spread (which is May),” an EFSA spokesperson told GlobalMeatNews.
The Authority has released several potential scenarios on how the recently discovered disease could evolve in the next few months. It concluded that three types of epidemiological situations could be envisaged. In areas where a recent incursion might have occurred in animals not previously exposed to the virus, symptoms are being observed and might result in malformation in foetuses at a later date. In areas where incursion occurred in the past and part of the ruminant population has become immune, congenital malformations are not observed or unreported because very rare. In areas where no virus incursion occurred, but a susceptible population is present, it is important to record data and monitor potential symptoms.
“These scenarios are what our scientists reasonably believe could be observed in the coming months in Europe, based on the data available at the moment. What’s important to highlight here is that the outbreaks were observed only a few months ago and, on the basis of the limited information available, EFSA’s experts are already able to give some likely scenarios which are scientifically based,” the spokesperson added.
To come up with the scenarios, EFSA looked at currently available scientific data, but stressed that they were very limited. It compared SBV to Bluetongue disease, another virus affecting ruminants and transmitted by insects only.
“Assuming that SBV is a non-direct transmissible, vector-borne, infectious disease, that vector parameters for the spread of SBV are those for [Bluetongue], (...) the hypothetical scenarios show that, depending on the temperature and the number of vectors, SBV might spread further in susceptible populations. Whenever the number of vectors per host and the temperature are above a specific threshold there is a possibility of a wider disease epidemic affecting more Member States,” EFSA concluded.
SBV symptoms include fever, reduced milk yield, loss of appetite and diarrhoea, and usually last a week. When affecting pregnant animals at a particular stage of gestation, it can cause malformations in foetuses or even abortion.
EFSA pointed out that in regions currently affected, including Germany, Belgium, France, the UK and the Netherlands, animals were probably infected by insects last summer, even though the first symptoms were observed in late 2011.