Climate change opens doors for new diseases

A disease usually found in Mediterranean regions has to spread to northern Europe as a result of climate change, according to scientists.

The disease, which affects sheep and cattle, is known as Schmallenberg, and is suspected to be passed virally through midges. Such diseases used to only be found in Spain, Portugal and Turkey. However, in the last six years, two types of midge-borne viral diseases have been found in northern Europe. Since January alone, Schmallenberg has managed to infect 83 farms in the UK, and was also found in German livestock last year.

These instances collaborate with the findings of scientists at Liverpool University, who have been studying climate models and information on the biology of viruses and midges.

“Temperature changes in Europe which to most of us have felt relatively small have in our model led to a large increase in the risk of viral midge-borne diseases,” revealed Professor Matthew Baylis from the Institute of Infection and Global Health at Liverpool University.

The rise in temperature experienced in recent decades has seen a surge in the number of midges and has also increased the frequency of midges’ feeding. Warmer climates also allow viral diseases to develop faster.

In the case of Schmallenberg, this has introduced to northern Europe cases of lambs and calves being born with deformities or being stillborn, as a result of infection during a critical stage of pregnancy. In adult animals it causes fever and diarrhoea, but animals do recover and, according to the Netherlands government health agency, the disease poses no threat to humans.

“There is the possibility (Schmallenberg) will simply die out, but I think that would be too good to be true,” said Professor Baylis.

“There’s a lot of virus about, and I think it’s quite likely that it won’t simply go away in one year. Is Culicoides (the midge) the only means of spread, or is there something else on a local level- fecal-oral, or aerosol (airborne) spread? We don’t know.”

Although not fatal to adult animals, the lambs and calves that are born infected with the disease this spring could potentially pass the disease onto new midges. These midges will in turn infect cows and sheep, and these will then give birth to more infected, potentially deformed animals next year. A vaccine for Schmallenberg is currently being developed, however it is not expected to be available to famers and cattle owners for at least 18 months. In the meantime, farmers have begun to take precautionary measure such as providing shelter for their animals.

The Schmallenberg situation raises questions about what other diseases could gain new ground as milder climates spread north. The models used by Liverpool University suggest other similar diseases should be expected in the future, according to Professor Peter Mertens, from the Institute for Animal Health in Surrey, who warned: “The doors are open.”

 

Image: Joost J Bakker IJmuiden | flickr