COUNTRY LIFE IN BC • MARCH 2019


Bluetongue outbreaks expected to increase Warmer temperatures elevate risk of disease


In 2007, the United


Kingdom had its first outbreak of bluetongue, a viral disease that affects sheep and cattle and – on a wider scale – domestic and wild ruminants.


According to Agriculture


Research by MARGARET EVANS


It is spread by the bite of


infected midges of the Culicoides species. Symptoms include fever, lameness, reddening of the mouth lining, swollen lips, difficulty swallowing and breathing, and a swollen, purple- coloured tongue (hence the name).


Bluetongue can be fatal in sheep and, in fact, deaths in an infected flock can reach 3%. But while bluetongue is often mild in cattle, they are suspected of being the reservoir for the virus. Bluetongue originated in


Africa but it’s now found in the Middle East, India, China, the US and Mexico. In Canada, bluetongue has occurred in the Okanagan Valley over the past 30 years as a result, it is thought, of wind-borne infected midges blown north from the US where the virus is endemic. Then, in 2015, bluetongue was confirmed in three cattle on a single farm in Chatham-Kent, a municipality in southwestern Ontario, putting all sheep farmers on alert.


While that may appear to be another case of wind- borne insects, recent research at the University of Liverpool in the UK suggests that climate change could be a critical driver in the future expansion of bluetongue outbreaks. In a guest post in the online publication Carbon Brief, postdoctoral researcher Anne Jones, a scientist with UK- based IBM Research (the research division of computing giant IBM), wrote that over the past two decades the disease has spread to Europe as a result of infected midges being blown across the Mediterranean Sea. Climate change is allowing the disease to not only get established in southern Europe but spread further north to France, Switzerland and Germany where it has affected thousands of farms. The financial cost from livestock losses has been huge. The spread of the disease to England in 2007 occurred as midges were windblown across the English Channel following the 2006 heatwave.


and Agri-Food Canada, the virus is usually restricted to late summer and early fall when temperatures are above 13 degrees Celsius, warm enough for the virus to multiply. Midges are cold-blooded insects so higher temperatures and heat waves may accelerate their lifestyle, population, range and the spread of the virus. And that should put everyone on alert as we cope with climate change. At the University of


Liverpool, scientists have used mathematical modelling to identify why the 2007 outbreak was actually smaller than it could have been and predict the future impact of the disease as the climate warms.


Their study suggested


three factors that, luckily, limited the outbreak. The first was the fact that the location in southeast England has a relatively low farm density so the spread of the virus between farms was limited. The second was animal movement restrictions in place due to the 2007 foot and mouth disease outbreak in the UK. And third was the fact that, despite the 2006 heatwave which likely played a role in boosting bluetongue transmission in Europe, 2007 summer temperatures in the UK were below average. “The UK outbreak would


have been larger had the virus been introduced in a warmer year, something that is likely to occur more frequently in the future due to climate change,” said Joanne Turner of


the University of Liverpool’s Institute of Infection and Global Health. In the research study,


Turner and her team predict that by 2100 the disease risk will extend further north, outbreaks will be larger, and the transmission season will last up to three months longer. A 1-in-20-year outbreak in today’s temperatures will be the norm in 2070, 50 years from now, in a world with high greenhouse gas emissions. That profile for Europe and the UK would logically be duplicated in North America, with more outbreaks in Canada as a result of infected midges moving up from the US, especially considering the trend toward extremely hot summers. “Our results suggest that efficient detection and control measures to limit the spread of bluetongue and similar newly emerging vector-borne diseases will be increasingly vital in a future, warmer world,” said Jones. Given that midges expand their range by being wind- blown, it is difficult to put biosecurity measures in place. That means farmers will need to be especially vigilant with their own protocols for protecting their livestock against this spreading and deadly virus. An outbreak of bluetongue


considered endemic in the US (serotypes 2, 10, 11, 13 and 17) is immediately notifiable under the Health of Animals Regulations and laboratories must report confirmed diagnoses to the Canadian Food Inspection Agency. This


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FILE PHOTO


will ensure verification and support international reporting and certification requirements. Any other type of bluetongue exotic to the US is federally reportable under the Health of Animals Act.


The study, “Bluetongue risk under future climates,” was published in Nature Climate Change.


Margaret Evans is a freelance writer based in Chilliwack specializing in agricultural science.


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