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Birds and foot-and-mouth

Malcolm Ogilvie

Perhaps not surprisingly, the possibility that birds might be carriers of foot-and-mouth disease has been raised during the present epidemic, especially recently when new cases have occurred many miles from existing ones without, initially at least, any obvious animal, human or vehicle connection. For example, a letter to the 'Scottish Farmer', a weekly magazine widely-read among the farming community, warned of the danger to cattle and sheep on Barnacle Goosethe islands of Bute and Islay when the Barnacle Geese wintering on the Solway left for their arctic breeding grounds. However, the truth of the matter is that this population of geese migrates north-east to Svalbard (Spitsbergen), and so doesn't come anywhere near these islands, which lie many miles to the north-west. And then 'The Times' newspaper, reporting on the 30-mile leap of the disease from Dumfriesshire to Jedburgh in the Borders, quoted an agricultural official as agreeing that some of these same Solway geese could have fed on infected grasslands on the Solway and then passed on the infection, presumably through their droppings, as they flew over Jedburgh on their way to their "Canadian" breeding grounds.

A third report was even more improbable. A letter-writer to 'The Scotsman' newspaper blamed birds of prey, saying that "the outbreaks appear most prevalent where their numbers are excessive", which suggests more than just a concern about foot-and-mouth, and suggested that these birds, instead of being allowed to feed on diseased carcasses and then roam freely, should be destroyed,. Fortunately a reply was published pointing out that, of our British birds of prey, only Golden Eagle, Sea Eagle and Red Kite were carrion feeders and that the first-named was a very scarce breeder in south-west Scotland (just two pairs in Dumfries and Galloway, plus one in Cumbria) and that the other two were, at most, rare visitors. The writer added, for good measure, that nowhere in Scotland were numbers of raptors excessive and that, indeed, populations of some species were being held down by illegal persecution.

So what is the true state of affairs? Can birds transmit foot-and-mouth disease and, more importantly, do they? In March, the RSPB commissioned Professor Chris Feare, an independent agricultural scientist, to investigate the matter. His report (which is available on the RSPB's website, concluded that while there is a minimal, and theoretical, risk that birds could spread the disease, there is no evidence from the scientific literature or from a detailed analysis of earlier outbreaks in the 1950s and 1960s to suggest that they actually do. David Snow, who anaalysed the 1967-68 outbreak, concluded that the spread of the disease correlated best with the prevailing winds. Furthermore, a large Starling roost near Oswestry in the area of the outbreak had no detectable influence on the spread of the disease, which actually by-passed the roost in its spread to the north-east and never affected the farms in its immediate area.

One difference from the 1967-68 outbreak is the presence, often for several days, of dead animals left out in the open. Whether crows and large gulls, which are undoubtedly feeding on these carcasses, could spread the disease via their droppings is unknown, but is probably, again, theoretically possible, but unlikely.

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Dr Ogilvie is a natural history writer and editor, formerly a research scientist with the Wildfowl and Wetlands Trust, and resident on the island of Islay since 1986. Until 1997, a member of the 'British Birds' editorial board and also one of the editorial team which produced 'Birds of the Western Palearctic'.