Risk of the spread of disease in livestock from dog faeces
The purpose of this note is to provide information and advice about the risk of the transmission of diseases in livestock from contaminated dog faeces.
Disease in 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. The two diseases are:
- Neosporosis – which can cause abortions in cattle
- 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 responsible for the highest percentage of all cattle abortions reported in the UK. Once neosporosis infection has occurred in a cattle herd it can persist within the herd due to the vertical transmission of the parasite between cows and calves. The Moredun Research Institute (for Animal Health) near Edinburgh is carrying out research into the disease at present. Although this work is ongoing, the Moredun has published information on the disease and the main points to note are:
- Neospora eggs are produced by infected dogs* and excreted in their faeces.
- Cattle will become infected if they eat food or drink water contaminated with Neospora eggs.
- Infection in cattle is common and frequently there are no obvious ill effects for cow or calf.
- The disease manifests when Neospora multiplies in the cells of the developing calf and its placenta and causes sufficient damage to trigger abortion or stillbirth.
- Control of Neospora abortion is difficult but certain management practices can be applied to reduce the risks.
- There are no drugs currently available to control this disease in cattle or to cure infected animals.
- No vaccine is currently licensed in the UK to prevent neosporosis in cattle.
- Current knowledge suggests that Neospora does not cause disease in human beings.
* Moredun advise that dogs are the definitive host of the parasite and that they have not founda link between transmission of Neospora eggs and other carnivores such as wild foxes.
The vertical transmission of neosporosis is a major cause of persistent infection within a herd, however spread of the disease between unrelated females only occurs where a dog acts as host to the parasite – such point sources of transmission can cause ‘abortion storms’ within a herd. The parasite can be picked up by dogs through the ingestion of contaminated livestock material, such as placentas from newly calved cows, or by being fed contaminated raw meat. This does not rule out other possible transmission routes, but there is no definitive information on other transmission routes at the current time. Faeces from infected dogs can contaminate pasture and potentially cattle feed, water or bedding.
Evidence suggests that only a small number of infected dogs develop symptoms of the disease, which include progressive lameness and paralysis in pups less than 6 months of age. Infected bitches can pass the parasite to their puppies during pregnancy by trans-placental infection. If dogs do develop symptoms, most of these cases are fatal or require euthanasia.
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 try to control. As there is no way to effectively prevent (through vaccination) or to treat neosporosis, a farmer’s main line of defence against the disease is to take reasonable and proportionate actions to manage the likelihood of Neospora contamination.
Sarcocystosis is also caused by parasites, Sarcocystis spp, which use a number of intermediate hosts, including dogs. The main points to note are:
- Sarcocystis eggs are produced by infected carnivores and excreted in their faeces.
- Sheep will become infected if they eat food or drink water contaminated with Sarcocystis eggs.
In many cases, infected livestock show no symptoms, but the disease is more likely to manifest if there is a high level of infection in the environment which could occur in a field used heavily for dog walking. Even when symptoms have not been present, the presence of sarcocysts on a carcass following slaughter can result in the carcass being condemned. The disease can be passed on from ewe to lamb during pregnancy, but vertical transmission is not believed to be an important method of spread for sarcocystosis.
Dogs can pick up the parasite through the ingestion of contaminated material from carcasses, or by being fed contaminated raw sheep meat. Faeces from infected dogs can contaminate pasture and animal feed, water or bedding. In contrast to neosporosis, there is no transmission of the Sarcocystis parasite between bitch and puppy.
The scientific evidence demonstrating the link between infected dogs and sarcocystosis in sheep is compelling, but the disease is generally regarded as less of a problem than neosporosis.
There is no vaccine against sarcocystosis in sheep and although theoretically there are some possible treatments available, the high cost and practicality of administration of these prevents their application. As with neosporosis, the most feasible option for the farmer is to introduce reasonable and proportionate management practices to reduce infection risks.
Control of transmission by dogs.
Transmission of the diseases by dogs involves two stages – dogs eating material which contains the parasites and subsequent ingestion of the dog’s faeces by livestock. The following issues are relevant in trying to minimise the risk of contaminated dog faeces transmitting these diseases to livestock. For Access Officers, the issue of most relevance, in terms of the potential to play a helpful role, relates to dog fouling – see the 3rd point:
- Carcass management – both diseases can be picked up by dogs which eat infected placenta/ foetal material, or raw meat from infected stock. To minimise the risk of picking up the parasites, dogs, including farm dogs, should not be allowed to eat material from fallen stock, or other material such as placentas or foetal material. Prompt disposal of carcasses and any other potentially contaminated material will help to limit the spread of disease.
- Working dogs – there is a need to raise awareness of the potential risk of infection of working dogs from eating uncooked meat. Animal Health is responsible for issuing approvals to allow raw meat not certified for human consumption to be fed to animals (approvals are required for working dogs, not pet dogs) and can include hunt kennels, racing greyhounds etc. as well as farm dogs. Farm dogs should, as far as possible, not be allowed to defecate in grazing fields, or in buildings which are used to store animal feed or bedding, or to house animals.
- Domestic / pet dogs – the Dog Fouling (Scotland) Act 2003 makes it an offence to not pick up your dog’s faeces, and applies to all public places (but specifically exempts agricultural land, including grazing land *). Public places include public parks, mainly with the intention of reducing the risk of transmission of the disease toxocariasis to children. This offence applies to everyone in charge of a dog, including commercial dog walkers. Awareness should be raised of the potential risk of passing on infection to livestock, and all dog walkers should be encouraged to pick up their dogs’ waste, even if they are on agricultural land.
- Raw meat – if raw meat is the preferred choice for feeding dogs, dog owners should be encouraged to seek advice on how to kill parasites before meat is eaten, for example freezing the meat for a period of days before feeding it.
Vets and other organisations which provide advice to dog owners can help advise on precautions to take if feeding dogs raw meat, and the NFUS and SRPBA have roles in disseminating advice relating to carcass management and working dogs. In terms of encouraging farmers and land managers to play their part in controlling the risk of transmission by dogs, the key messages are set out below.
Key messages for farmers / land managers:
- You should remove any raw livestock matter on farms promptly – such as an aborted foetus, the placenta of a newly born calf / lamb, or fallen stock – to make sure that dogs can’t get access to it or eat it.
- You should make sure your own dogs do not defecate where livestock graze, where animal feed or bedding is stored, or where stock is housed undercover.
- Feedstuffs, hay, bedding and water should be kept free of faecal contamination by dogs and other carnivores, as well as vermin.
It is worth noting that, whilst the two issues highlighted in this briefing are of particular concern due to the lack of effective forms of treatment and the economic impact they can have on farming, other problems affecting livestock, including horses and pigs, can occur from grazing land contaminated by infected dog faeces. For animal health reasons, and for the benefit of other people enjoying the outdoors, it is helpful to encourage good practice by the public to always pick up after their dog.
Key messages for dog walkers using local ‘hot spots’
Parasites can be transmitted to livestock through infected dog waste being left on grazing land. Some of these parasites cause diseases in livestock which can result in death of sheep, and abortion in cattle.
Dog walkers and owners can take some simple steps to help minimise the risk of spreading these diseases:
- Always remove dog waste from all locations, including grazing land. If your dog is carrying the parasites, it will pass the eggs in its poo. By safely disposing of dog waste, you will help minimise the risk of passing on disease to livestock.
- Don’t let your dog eat remains of dead animals or leftover birth materials such as placentas whilst out walking. Your dog may be infected by parasites if you allow it to eat animal material it may find whilst out on a walk. Often the parasites cause no symptoms in dogs, but sometimes the disease of neosporosis can seriously affect your dog’s health and possibly result in death.
- If you choose to feed your dog raw meat, make sure that it is parasite-free. Your dog can pick up parasites from eating uncooked meat. You won’t be able to tell if raw meat contains parasites just by looking at it, but your local vet will be able to give you advice on how to make sure raw meat is safe for your dog.