Journalist and part-time shepard Tim Metcalfe writes on a canine menace

Last week I mentioned the risk dogs pose to sheep during the lambing season. At the risk of being seen to be bashing our canine companions, I’d like to highlight the risk of disease being spread by dogs – especially those who get out and about with their owners in rural areas where they mix with livestock.

There is growing evidence of the links between two specific diseases in livestock and the presence on grazing land of faeces from infected dogs. You may have seen farmer Adam Henson talking about the issue on Countryfile recently.

The diseases are Neosporosis – which has been shown to cause abortions in cattle – and Sarcocystosis – which can cause neurological disease and death in sheep.

Neosporosis is caused by the parasite Neospora caninum and the disease is now thought to be the most common cause of all cattle abortions reported in the UK. Neospora eggs are produced by infected dogs and excreted in their faeces. Cattle come along and eat the infected grass. There are no drugs available to control this disease in cattle or to cure infected animals, so it has a serious economic impact for livestock farmers.

Research in Scotland has shown that dogs are the definitive host of the parasite and that they have not found a link between transmission of Neospora eggs and other carnivores such as wild foxes.

So how do dogs pick up this nasty parasite? Neospora can be picked up by dogs being fed contaminated raw meat or eating the remains of dead animals while out walking. Sadly there is no definitive information on other transmission routes, but what is known is that faeces from infected dogs can contaminate pastures. Researchers say that the prevalence of the disease in herds, and its potential impact on farm economics – due to infected cows being more likely to abort, premature culling and reduced milk yields – make this an important disease to control.

Sarcocystosis in sheep is also caused by a parasite called Sarcocystis spp which also use a number of intermediate hosts. Sarcocystis eggs are produced by infected carnivores and excreted in their faeces. Sheep will become infected if they ingest contaminated food or drink.

In many cases, infected sheep show no symptoms, but the disease is apparently more likely to occur in fields used heavily for dog walking. The disease can also be passed on from ewe to lamb during pregnancy.

Like Adam Henson, farmers are now making sure their own dogs do not defecate where livestock graze, or where animal feed or bedding is stored – or where stock is housed undercover.

Dog walkers and owners are being asked to follow their example by always removing dog waste from grazing land, such as Oxford’s Port Meadow for example a popular dog walking area. By safely disposing of waste, dog owners can help minimise the risk of passing on this microscopic menace to livestock.