CROSS-border co-operation can help limit the spread of deadly viruses and diseases to our shores, says Brian Hosie
Chinese Bird Flu passed between humans, camels linked to deaths in the Middle East, a mystery illness killing bats in the United States and UK livestock threatened by midge-borne infections.
We all face the threats of rapidly developing, new, infectious diseases or the emergence of more serious strains of known ones. In 2002 SARS (Severe Acute Respiratory Syndrome) emerged in China and ten years on Middle East Respiratory Coronavirus (MERS CoV) threatens those living on the Arabian Peninsula. Both cause severe respiratory disease and high death rates. In the last five years, cattle and sheep farmers in the UK have had to cope with the effects of Bluetongue and now Schmallenberg Virus. They blew in from Europe but probably came from Africa originally. Plants can be affected too: witness ash dieback.
There are three main reasons for the increasing threat of infectious disease. First, there are more of us than ever before. Not only has Scotland seen a population increase recently, the world population has doubled to seven billion in the past 50 years and continues to rise. In many parts of Africa and Asia, humans and their livestock are in direct competition with wildlife for the available resources. As a result viruses and other disease agents can more easily transfer from wild animals to domestic pets, livestock and humans. SARS is one example. The virus was isolated from palm civets and other wild cats sold in live markets throughout China. However, evidence now suggests SARS originated in Chinese bats and the virus jumped to directly to humans, or via the animal markets. This year MERS-Cov emerged among pilgrims to Mecca. The latest research suggests this virus, or one very similar, also occurs in camels. Again it appears there is a bat link.
Travel and the rapid expansion of global trade are also factors in the spread of infectious disease. Bluetongue is a viral disease, spread by biting midges and affecting cattle and sheep. Originating in tropical parts of Asia and Africa it causes the respiratory tract to swell making it hard for animals to breathe. They become ‘cyanotic’, with a bluish discolouration of the skin due to a lack of oxygen in the blood. Scotland’s Rural College (SRUC) operates a network of eight diagnostic Disease Surveillance Centres across the country, supporting practice vets by investigating and diagnosing diseases in farm animals and wildlife. Working closely with EU colleagues and the Animal Health Veterinary Laboratory Agency labs in England and Wales we followed the progress of a West African strain of the virus that appeared first in Germany and the Netherlands but spread throughout Europe causing heavy losses. The development of a vaccine prevented its establishment here.
Then in late 2011 a new virus appeared around the German town of Schmallenberg, spreading to the Low Countries. Again the virus is spread by midges. This time Scotland did not escape. While new vaccines offer the prospect of controlling this disease, the emergence of two midge-borne, tropical viruses in the same part of Western Europe within five years is alarming. It also suggests a common route of introduction, possibly though infected midges airfreighted with flowers and vegetables from Africa.
The recent relaxation of rabies quarantine rules have seen an explosion in the numbers of dogs and cats moving in and out of Britain. Already we are seeing parasites such as heartworm, leishmania and lungworm introduced with pets returning from Europe.
All of this is happening against the background of the third threat: climate change. High summer temperatures helped the rapid spread of midge-borne bluetongue across Europe and it is likely the exceptionally warm July will have favoured the spread of Schmallenberg Virus here. Recent wet summers and warm winters have favoured the spread of parasitic diseases of farm livestock such as liver fluke. Last summer’s sodden fields helped disease levels in cattle and sheep rise to five and ten times those of 20 years ago. Over-reliance on one drug treatment has made the situation worse, with some strains of the parasite not killed by the drug.
Information and intelligence about disease spread amongst humans, livestock or wildlife is now more vital than ever. Doctors, vets, including those at SRUC, and other health professionals must continue to co-operate across international boundaries and share information on these emerging diseases in order to tackle the threats we face.
• Brian Hosie is veterinary services manager at Scotland’s Rural College.