What's going on Blog Silent killers: Neosporosis Neosporosis is a disease that is said to be one of the most common infectious causes of abortion in cattle, but it is not only cattle keepers who need to understand its implications. Anyone who walks a dog on land where livestock can graze also has a responsibility to be aware of this killer disease. Caused by Neospora caninum, or N. caninum for short, this disease was first identified in the 1980s and is one of the most common infectious diseases in cattle worldwide. Studies have indicated that it causes over 10% of all abortions in UK cattle. Neospora is a protozoan parasite, that is a microscopic, unicellular parasite organism, that can invade, live and multiply inside animal cells. Cattle can become infected either by ingesting parasite eggs (oocysts) or by acquiring the parasite in the uterus from their mothers. It can cause repeat abortions in successive pregnancies and the parasite is very effectively transmitted from an infected dam to its foetus – in fact, this transmission may occur in up to 95% of pregnancies in infected animals and they may also pass the infection to their offspring over several generations. One of the most likely ways that the disease is introduced into a herd is by buying in infected animals, but the disease can be transmitted via dog faeces. The dog, and other canids such as foxes, are the definitive host of N. Caninum, which means that they are the animals in which the parasite becomes sexually mature and reproduces. A dog walking on farmland can acquire the disease after eating tissue, such as afterbirth, from an infected cow. With the eggs being infectious for up to six months, this is potentially the start of a vicious circle if dog faeces are then left in fields where cattle can ingest the eggs while grazing. For dog walkers, the message is simple: wherever you are, clear up after your dog. Whilst in urban and public access areas such as parks most dog owners are aware of their social responsibility to protect children and other members of the public, many don’t see the need in open countryside – after all, no one clears up after cattle, sheep or horses, do they? However, as neosporosis is also dangerous to dogs, causing illness in adult dogs and death in young puppies, it is also in the interest of dog owners themselves to take responsibility in the countryside. This means not only clearing up after your dog, but making sure that it doesn’t eat fallen livestock, after-birth or birth fluids from livestock – another good reason for keeping dogs on leads in any area where livestock is grazed. Infection from dog – including farm dog – or fox faeces is one factor, but vertical transmission from mother to calf is far more significant and can maintain infection in a herd. There are currently no effective vaccines to prevent Neospora infection nor are there any licensed drugs for bovine neosporosis. While cows infected with Neospora are five to seven times more likely to abort than uninfected cows, there are no other clinical signs. Diagnosis can only be reached by submitting aborted foetuses for post-mortem investigation or by detecting parasite-specific antibodies in the blood or milk of infected live animals. All cattle with antibodies to Neospora are sources of infection to their calves, so identified cattle should be culled from the herd. Only seronegative cattle should be used for breeding, although heifers with antibodies can be sold for meat. Farm biosecurity measures are also key to preventing the spread of disease. Fallen, aborted foetuses or cattle tissue leftover from calving should be disposed of promptly and hygienically and any livestock feed should be covered and locked away to prevent access by dogs and wildlife. Dogs should be prevented access to calving areas or parts of the farm where pregnant cattle are kept and if public footpaths cross the farm, it is advisable to put up notices reminding dog walkers that they should pick up their dog’s faeces to prevent passing on any infection to livestock. Any cattle keeper that suspects there may be Neospora problems in their herd should consult their veterinary practice to assess the risk and impact on the herd. Bovine neosporosis is now included in the Cattle Health Certification Standards (CHeCS) and CHeCS licensed health schemes include control programmes specific to bovine neosporosis.