Neosporosis in cattle
If your cow aborts or is showing signs of infertility, one of the first conditions to consider is neosporosis. It is the most common diagnosed cause of abortion in cattle in New Zealand and is responsible for almost half of all abortion cases confirmed in veterinary laboratories.
The abortion rate on infected farms is typically around 7 percent, but in severe outbreaks, rates as high as 30 percent have been recorded. These losses can have a serious financial impact on both commercial and small-scale cattle operations.
What Causes Neosporosis?
Neosporosis is caused by Neospora caninum, a microscopic parasite. A cow infected with Neospora may appear completely healthy until she becomes pregnant. At that point, the developing foetus is likely to die.
If the foetus dies early in gestation, it may be reabsorbed.
If the death occurs later, the foetus may be aborted or mummified.
Occasionally, the calf is born appearing normal, but is actually infected.
If this infected calf is raised as a replacement heifer, she may go on to infect her own calves. These calves may also be aborted or be born infected, continuing the cycle.
Signs of Neosporosis in Cows
Affected cows may not show outward signs of illness, but the following are common indicators:
Abortions, stillbirths or mummified foetuses
Infertility due to early embryonic loss
Reduced milk production in some infected cows
Slower growth rates in infected young stock
Most abortions occur in cows under four years of age, and typically around the fifth month of pregnancy.
What to Do if Your Cow Aborts
Consult your veterinarian immediately. They may recommend testing for Neospora using blood samples.
If neosporosis is confirmed, your vet may suggest one or more of the following approaches:
Culling infected animals
Treating affected stock, if treatment options are appropriate
Vaccinating young stock or any new animals brought onto the property
Taking no action, depending on your overall farm management goals
Your vet will help determine the best course of action based on economics and long-term breeding plans.
How is Neosporosis Spread?
Although dogs are often implicated in the disease’s name, the most common route of transmission is vertical – from infected cows to their calves in utero. This accounts for over 90 percent of cases.
However, horizontal transmission through dog faeces is possible. Dogs and possibly other wild mammals can spread the parasite if they consume infected tissue and then defecate on pasture grazed by female cattle.
Preventing Neosporosis on Your Block
You can reduce the risk of neosporosis by taking the following precautions:
Do not allow dogs to defecate on paddocks grazed by breeding stock. If they do, remove the faeces promptly.
Prevent dogs from consuming aborted calves, afterbirth, or raw meat from cattle. The parasite can live in muscle and internal organs.
Avoid buying cows with a history of abortion unless their health and reproductive history is known and clear of neosporosis risk.
