Slaughter of the lambs

In 2012 the spread of Schmallenberg virus across Europe and its impact upon the farming community caused major concern.

Schmallenberg virus is a disease of farm animals that has so far infected many farms in Western Europe, including more than 1000 farms in England. The virus seems to have emerged from the small German town of Schmallenberg, 80kms east of Cologne some time in the latter part of 2011.

By the middle of 2012 it had spread to involve many farms throughout Germany, Belgium, Luxemberg, France, Italy and Britain.

The virus is transported and spread by small biting insects such as midges and possibly mosquitos. The particular species of midges so far identified are all native to England, but there would seem to be evidence that in the autumn of 2011 plumes of infected midges were blown across the sea from Western Europe into England.

To this point only farm animals have been affected, especially small ruminants such as sheep and goats, and while the symptoms in adult animals are not severe, in pregnant female sheep the virus can produce major foetal damage leading to a range of birth deformities. In parts of Germany 50% of newborn lambs have been born with severe malformations of the brain, spine and limbs and there is evidence that many of England’s newborn lambs seem destined to go the same way.

So far it appears that thousands of lambs have died throughout Western Europe and the disease is threatening the survival of many farms.

While this particular virus does not seem capable of spreading to humans it is a member of the orthobunyavirus family of which a number are known to infect humans. A vaccine has been recently developed but it will be some time yet before it is officially licensed and becomes widely available.

While there is no evidence of the virus spreading to farms in the Southern Hemisphere, our experience with SARS, Avian and Swine Flu shows just how easy it is for viruses to jump across time and geographic space, and how distance, isolation and national boundaries are of little significance in controlling the spread of infectious disease.

Bacteria and viruses recognise no international boundaries, and an outbreak anywhere in the world has significance for Australia. Such microbial agents move almost at will around our world, transported by insects, birds or in food and water and in a world where more than 1.6 Billion people cross international boundaries by air every year, in journeys that are considerably less than the incubation time for most infectious diseases, who knows what accompanies them.

There is little doubt that over the last decade our world seems to have become more vulnerable to a range of so- called ‘new’ infections such as SARS, Avian Flu, and Mad Cow Disease as well as the re-emergence of a number of older infections thought to be well under control. Witness for example the ‘resurgence’ of whooping cough in many developed countries and the rise of drug resistant TB and malaria throughout the world.

Among other things the emergence of infectious disease threats reveals that we live in an interconnected world and that any belief we held about inheriting a safe antiseptic infection-free world was totally misplaced.

More critically perhaps we continue to grossly under-estimate the power of our natural environment and the ability of the microbial world to adapt, mutate, and evolve. There is also little doubt that we have placed far too much reliance upon antibacterial and antiviral drugs to protect us. We also continue to overlook the fact that our health is intimately connected to that of the animal world.

Most of the infectious diseases to infect humans are zoonotic or animal diseases, long present in the environment, often circulating for hundreds even thousands of years among their primary animal hosts, and only rarely making the jump to infect humans. The influenza virus perhaps provides the best example of this.

The virus is nurtured among wild bird colonies in parts of Asia and has circulated among its primary host for hundreds of years every so often reaching out to infect human populations.

Schmallenberg virus demonstrates once again just how closely the natural environment and animal health influences our everyday lives and just how vulnerable our health and food security are to threats from the microbial world. While the full impact of Schmallenberg virus is still playing out in parts of Western Europe, will our geographic isolation, vigilance and surveillance offer a defence should the virus move from the Northern Hemisphere, or is it just a matter of time before we see it ‘downunder’? Are we facing a ticking time-bomb for a country with millions of sheep and export earnings in the billions of dollars?

Quite probably this virus may burn itself out among the farms of Western Europe over the next few months particularly as the new vaccine becomes widely available, although as temperatures warm, and midge populations multiply, the threat may actually intensify.

It also seems something of an irony that in health terms we always seem to have to react after the threat has been identified rather than anticipate it before it actually occurs, and by the time we have identified the threat and managed to construct a response, thousands, perhaps millions of people and animals have already suffered.

As for us in Australia, if  it’s not Schmallenberg virus, then we can rest assured that somewhere in the world a new viral threat already lurks, perhaps circulating among its natural animal hosts just waiting for the opportunity to jump to another species, mutate, and threaten our complacency.

It’s a brave but perilous world that confronts us.