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- The rule of thumb is to limit abortions to no more than 2% in adult pregnant animals.
- Producers want quick answers once an abortion storm hits.
- However, a circumspect approach is required and firstly demands that the aborted foetus and afterbirth be sent to a laboratory for testing to determine possible causes.
- The second step is to determine the most common contagious causes of abortions by studying the herd’s disease status.
- It is important to cull the carriers of diseases that can cause abortions.
The number of abortions occurring in pregnant animals is one of the most important observations to make during the pre-calving and -lambing period. The rule of thumb is to limit abortions to no more than 2% in adult pregnant animals, and no more than 3% in young first-calvers or first-lambers.
Because of certain metabolic and physiological reasons not all abortions will involve disease-causing organisms, for example gestation that cannot be maintained at a hormonal level, or an anatomical abnormality in the foetus. When abortions are in fact the result of disease-causing organisms, toxins or other factors, the abortion percentage can easily exceed the 2 and 3% marks. In these cases, the herd veterinarian must be consulted directly to examine the cause and make a specific diagnosis.
The big challenge
Producers want quick answers once an abortion storm hits. However, a circumspect approach is required and firstly demands that the aborted foetus and afterbirth be sent to a laboratory for testing to determine possible causes. Unfortunately, these tests have a less than 50% success rate in confirming the cause. Discuss the sample-taking process with your veterinarian and include a detailed description in your health protocol.
Sometimes it isn’t possible to send the aborted foetus and afterbirth to a laboratory. Therefore, it is important to take clear and detailed photographs or a video of both the foetus and afterbirth, as this will give a good indication of the age of the foetus along with any foetal or afterbirth abnormalities. The veterinarian can use this material as part of a complete examination.
Remember to always wear gloves when handling an abortus or afterbirth, as many of the organisms involved can also affect humans.
Herd status
The second step is to determine the most common contagious causes of abortions by studying the herd’s disease status, and collecting complete background information regarding vaccinations and other animal health management actions. On a well-managed farm, these general causes will already be well managed or eliminated.
The most important general disease conditions to include or exclude are:
- Cattle: Brucella abortus, trichomoniasis and vibriosis.
- Sheep and goats: Enzootic abortion and Brucella ovis.
Once the general causes of abortion have been eliminated because the herd has tested free of it or preventive vaccinations have been administered correctly, the next order of business is to investigate the following possible causes:
- Major management, feed, or environment changes during late gestation.
- The presence of plant or mould toxins, especially where bales (which have become wet) serve as supplementary feed prior to the calving or lambing season.
- Any fever-causing diseases such as tickborne (heartwater, redwater, and gallsickness in cattle) and insectborne (three-day stiffsickness, lumpy skin disease, bluetongue, or Rift Valley fever) diseases.
- Specific virus diseases that affect not only the respiratory system but can also lead to abortions in cattle, such as bovine viral diarrhoea (BVD) and infectious bovine rhinotracheitis (IBR).
- Chlamydia which causes enzootic abortion in sheep and goats, and have also become a significant cause of abortions in cattle.
- Other possible causes in sheep, such as toxoplasmosis, Campylobacter sp. (vibriosis in cattle) and Coxiella burnetii.
- Other bacterial causes such as leptospirosis and salmonellosis of which the incidence has not yet been well studied in South Africa.
Field observations
Abortions often occur over a short period of time right before the calving or lambing season. Producers will take note of the warning signs but as soon as an investigation into the causes start, the abortions come to a halt. It is difficult to explain the reasons for this phenomenon, but it is always better to take heed and at least commence with a basic examination and ensure that general preventive management is in place.
A number of causes can be eliminated or managed preventively in conjunction with the herd veterinarian:
- Test and cull animals infected long term with disease-causing organisms that can cause poor gestation or abortions, such as Brucella and sexually transmitted diseases.
- Compile a detailed vaccination programme, especially for replacement animals, ensuring that they are fully vaccinated before their first breeding season. Preventable abortions usually occur in this group during their first pregnancy.
- Use a pre-drafted plan to manage stress, nutritional shortages/supplementation, and environmental conditions during the pre-calving and -lambing season.
It is important to cull the carriers of diseases that can cause abortions. The cornerstone of prevention lies in vaccinating replacement animals and administering booster vaccinations. – Dr Danie Odendaal, consulting veterinarian.
For more information, contact Dr Danie Odendaal on 082 454 0532.
