There are quite a few infections that cattle, sheep and horses could pass to dogs (and vice versa) if they eat each other’s faeces. As well as salmonella, E coli and campylobacter, and a variety of other bacteria present in many faeces, there is a specific risk of leptospirosis to the dogs if the faeces are contaminated with cattle urine as well.
Faeces undergo a decomposition process that will include the production of various toxins (often by fungi) so dogs may also be poisoned by eating older manure. It is unlikely that cattle and sheep would be so poisoned – partly due to the disparity in size and relative dose, but also due to the ability of cattle and sheep to break down poisons in the large stomach (rumen).
Cattle and horses may also have certain drugs in their faeces as a result of veterinary treatment. However the quantity of any drug like ivermectin in the cattle faeces is so low that even an ivermectin-sensitive breed (such as many collies) would be most unlikely to eat enough manure to be affected. A normal dog would have to eat 10% of its own body weight in really fresh faeces from a recently treated cow to get enough ivermectin to achieve a normal (safe) therapeutic dose. In an ivermectin-sensitive collie the figure would be 2 per cent – which is still 300g of faeces being eaten by a 15kg collie.
Older faeces from less recently treated animals will have a lot less ivermectin. There are dog drugs that are present in their faeces in sufficient quantity to poison cattle or sheep. Is there anything harmful to cattle and sheep in dog faeces? The answer is yes – there are some tapeworms (Taenia hydatigena, T multiceps, T ovis, Echinococcus multilocularis, E granulosus) that dogs carry that can infect cattle and sheep. Usually these do not cause the sheep and cattle a problem, but they can pass to humans when we eat the cattle or sheep. It is important that you regularly worm your dog and you should consult your vet about the most effective product for your animal. Fortunately, these tapeworms are now rare, as we have had effective wormers for many years, but we still need to keep worming dogs to stop these things coming back, as they are still in the fox population.
It is essential that pet owners keep their dogs on a lead near any farm animal or pasture. Dogs who eat livestock or horse manure can be exposed to harmful parasites and bacteria that can cause diarrhoea and vomiting. Moreover, cattle or horses who have been treated with worming medication such as ivermectin can pass it in their manure for many days after treatment. Certain breeds of dogs, most commonly collies, carry a gene mutation that puts them at high risk of poisoning from these drugs. If a dog eats manure containing traces of worming medication, it can show severe neurological signs, such as tremors, seizures or disorientation. If your dog shows these symptoms, he should be taken to a vet immediately.
It is also important that pet owners pick up their dog’s droppings from pastures where cattle, sheep or horses are grazed.This is because dogs can carry a parasite called Neospora caninum without showing any outward symptoms, which can spread from their faeces to cattle. Neosporosis can cause abortion, premature or still births in cattle months or even years after they are infected and is very difficult to control.
Many dogs have a tendency to eat things they shouldn’t when out and about, including horse and livestock manure. Although it’s one of the least desirable habits among our four-legged friends, most breeds of dog that eat a small amount of manure will not become ill. But there is a risk of toxicity due to chemicals in worming medications, which will be passed in the faeces, and so dog owners – particularly those with certain ‘at risk’ breeds – should avoid letting their pets consume it. Horse worming treatments often contain a chemical called ivermectin, which is effective against many different parasites across a range of species. It is also used as a wormer in cattle and sheep. Some worming medications for dogs include the chemical – but in very low doses, managed by a vet, that cause no harm.
There is a far higher concentration of ivermectin in horse and livestock worming treatments and this can be passed in manure for days after the animal has taken the medication. This can be toxic to dogs who eat it, but the risk depends on the breed of dog, when the animals were treated and the amount consumed. Any dog that consumes a large amount of horse poop containing the chemical could become very ill, but a percentage of dogs of certain breeds have a gene mutation that predisposes them to toxicity from ivermectin at low levels. These include collies, Shetland Sheepdogs, Australian Shepherds, Old English Sheepdogs, long-haired Whippets, merle Pomeranians and possibly other herding breeds, as well as those with white feet. There is a test for the gene mutation that puts dogs at high risk, so you can check your own pet.Toxicity in breeds that don’t have the genetic predisposition to being affected by ivermectin in low doses is very rare.
Certain breeds of dog can become very ill after eating horse, sheep or even dog faeces. Border Collies and Shetland Sheepdogs, for example, are highly sensitive to the ingredients in certain wormers, so can become extremely unwell after eating faeces from animals treated with ivermectin-based products. Parasites in faeces can also pose a risk to both dogs and livestock. Dogs are hosts for a harmful parasite (known as Neospora caninum), though many are unaffected and generally show no symptoms, if infected. This parasite can be transferred to cows or other dogs when fields, bedding or grazing areas become contaminated with faeces.
Pregnant dogs can transfer the neosporosis infection down to their puppies, causing paralysis, difficulty swallowing,weakness and even death. Older dogs are also vulnerable and in rare circumstances the worms can cause severe intestinal blockages. Picking up your dog’s mess is incredibly important and will help avoid the parasite from spreading, for dogs and livestock alike.
Teaching your dog various ‘leave’ commands can be useful to discourage them from eating anything they shouldn’t. It’s also important to regularly treat your dog for parasites and always ensure good standards of hygiene when handling dog poor yourself, especially if pregnant. If you are concerned that your dog has eaten faeces or something he shouldn’t, you should make an appointment with your vet.