Neospora caninum is one of the most common causes of abortion in cattle in Ireland, according to the Department of Agriculture’s James O’Shaughnessy.

Speaking at a recent Teagasc / Animal Health Ireland (AHI) beef event, the veterinary surgeon and research officer explained how the disease can affect cattle.

“It is very common in some herds and farmers don’t know it’s in their herd in the first place,” O’Shaughnessy said.

Neosporosis may be suspected if an animal aborts during the fifth or sixth month of gestation.

He added that aborting animals don’t usually show any signs of infection, and in very rare cases, infected calves may be born with visible symptoms.

On some farms you’ll have maybe one or two abortions a year, sometimes you won’t even know until a cow shows up empty at the end of the year.

“Other times you might have a number of heifers all aborting at the one time,” he added.

Neospora may be suspected, but samples must be sent to the laboratory for testing to confirm infection.

“If you get a couple of animals that abort, try get your hands on the aborted calf or the cleanings for laboratory examination. Also take a blood sample from the animal itself,” O’Shaughnessy advised.

Antibodies to neospora fluctuate at various stages of the reproductive cycle. Antibodies are at their highest 10 to four weeks before calving. Animals found negative when non-pregnant or in early pregnancy should be retested at this time to confirm negative status.

O’Shaughnessy emphasised the importance of blood testing animals twice in order to confirm freedom from infection.

AHI has listed a number of economic losses due to neosporosis:
  • Potential value of aborted calves;
  • Retention of barren suckler cows;
  • Premature culling of breeding animals and consequent increased replacement rates;
  • Reduced value of high-genetic merit animals;
  • Loss of milk associated with abortion.

The issues of neospora infection

Once infected, animals remain infected for life. Any live, full-term calves they produce may be born infected, allowing neospora to be passed from generation to generation.

O’Shaughnessy confirmed neosporosis is not spread from cow to cow.

With vertical transmission – the spread of disease from dam to calf – offspring of neospora-infected cows kept as replacement heifers will cause problems down the line. Culling positive animals is recommended to try and deal with this issue, he added.

If a cow has tested positive for neosporosis, she’s far more likely to abort subsequent pregnancies than an animal that’s negative.

Cattle can also become infected with neospora by eating feed contaminated by neospora oocysts (eggs) in the faeces of an infected dog.

According to Animal Health Ireland, approximately 90% of infected cattle contract the infection from their dams, while only 10% are infected through contaminated dog faeces.

Dogs become infected by eating cleanings or aborted foetuses infected with neospora; and once infected, it will remain so for life.

However, dogs will only pass neospora oocysts for three weeks after acquiring the initial infection.

There is no practical treatment for neospora infection in cattle at present. And with no vaccine against neosporosis licensed in the EU currently, prevention and control is the only way to try and minimise the disease.

How to prevent and control neospora infection:
  • Minimise the risk of cattle ingesting dog faeces;
  • Foetuses and cleanings should be collected and disposed of so that dogs cannot access them;
  • Keep a completely closed herd, if possible;
  • Blood test any purchased breeding stock for neospora – two blood tests are required to confirm that an animal is truly negative;
  • Identify carriers of the disease and do not breed from these animals;
  • If positive animals are retained; their progeny should be fattened and slaughtered.