Should I look for Neospora in my herd?
Neospora is a commonly diagnosed cause of abortion in cattle and while it is more commonly a problem in dairy herds, suckler herds should also be aware.
Cattle can become infected in two ways:
By eating Neospora oocysts (eggs) from the environment along with food or water
As an unborn calf when Neospora crosses the placenta from an infected cow
Dogs are a vital part of the Neospora story. They become infected by eating Neospora infected placentae, foetuses, calves or wildlife. The parasite multiplies in their intestine and oocysts are passed in faeces for two to three weeks. After this the dog is immune and no longer a risk.
As oocysts are only shed when the dog is infected for the first time this is most likely to occur in pups or young dogs. The oocysts are thought to survive in the environment for many months. After being eaten by a cow the oocysts multiply and then become dormant within tissue cysts. This has no ill effects on the cow which continues to appear healthy. The danger comes during pregnancy when the parasite re-activates and travels to the placenta and unborn calf. What happens next can include:
Abortion – abortion storms can occur when infection is introduced to a herd for the first time
The birth of a healthy, but infected, calf which may go on to abort during its first pregnancy
The birth of a calf showing signs of nervous disease, however, this is uncommon
Infected cows remain infected for life. The main way that Neospora infection is maintained in the herd is by infected cows giving birth to infected heifer replacements who in turn abort or produce further infected calves themselves. There is no evidence of direct cow to cow spread.
Vet, Helen Carty
If you don’t have Neospora in your herd, you can keep it out by ensuring your cattle don’t get access to dog faeces. In addition you should maintain a closed herd or consider only buying breeding females from herds with a low risk of Neospora.
Herds can work towards a low risk level certification by following the CHeCS programme.
Annual blood testing of all breeding females over one year of age is required. In addition to annual testing, there are mandatory control elements of the programme. These are to ensure that infected females are not retained in the herd for breeding. A health plan must be in place to ensure that farm dogs cannot acquire or pass on infection to cattle. Abortions must be investigated. Herds can choose how quickly they wish to progress through the risk levels. It is possible, for example, to retain high genetic merit test-positive cows to breed bulls. If doing this however, the herd cannot progress above level 3 until the test positive animals are removed.
Herds are now assigned a risk level, from 1 to 5 as below, with 1 being associated with the lowest risk of being a source of Neospora infected stock.
Helen Carty
Level 1: Three or more consecutive clear annual herd screens.
Level 2: One or two consecutive clear annual herd screens.
Level 3: The number of test positive animals does not exceed 5% of the herd eligible for testing in the Neospora programme.
Level 4: More than 5% of eligible animals identified as test positive animals at the most recent test.
Level 5: These herds may be carrying out a testing programme, but are not adhering to the mandatory requirements of the programme.
For further information contact the PCHS team at pchs1@btconnect.com or call 01835 822456.