Sheep Abortion The Facts

As we head into the peak of lambing season, one disease no sheep farmer wants to see is abortion. This can occur in flocks in the last trimester of pregnancy, with some abortion storms leading to 25% losses.

The target for abortions is to have them under 2% in your flock. 

We regularly talk to farmers in the vet practice who have experienced this devastating disease.

Like every disease it can have massive health and financial impacts on flock performance. During an outbreak of abortion we must act fast to get issues under control.

We can make short term decisions that can help but also accurate early diagnosis will help to make better future decisions around control.

There are several agents that can cause abortion. Chlamydial abortion, toxoplasmosis, salmonella, listeria amongst other things.

By far the two most common agents isolated are Enzootic (chlamydia abortus) and toxoplasmosis. 

Sheep abortion some facts 

  • Chlamydia abortion is a bacterial infection that can cause abortions in our flocks. It can spread easily from the womb of infected sheep, aborted lambs or afterbirth. Even young lambs or other infected sheep can pick up the infection from these materials. It will lie dormant in these sheep until they are 90 days pregnant greatly increasing the risk of abortion. 
  • In simple terms exposed sheep may become infected. They will appear normal but can abort after 90 days of pregnancy. 
  • This is one of the abortion agents we can bring into our flock with sheep carrying the bacteria. This is why operating a closed flock pays or else buying stock from a farm of known disease status. 
  • Where outbreaks occur all aborted sheep and aborted materials must be kept away from other sheep. Once this problem or chlamydia abortion has been diagnosed vets can recommend flock treatments with antibiotics.
  • With increased concerns around AMR and antibiotic resistance we must be very careful about flock treatments without the correct diagnosis. 
  • Toxoplsmosis is an abortion agent caused by a protozoan oocyst. The cat plays as important intermediate host in this cycle. They can spread toxoplasma oocysts in their faeces which can infect immunoniave sheep. 
  • With toxoplasma you can get a number of presentations. Some ewes will abort early and will scan empty. Other ewes will carry close to full term aborting anywhere in the last 6 weeks before lambing. 
  • While enzootic abortion you can have some lambs born weak or alive, with toxoplasma more often than not you will have dead lambs (or mummified foetuses.
  • During a toxoplasma outbreak there is little point treating the flock. Once a diagnosis is made, then long term control strategies like vaccination become very important.
  • With cats playing an important role in the potential spread of toxoplasmosis. All feed stores should be secured and cats really shouldn’t be allowed in sheep sheds with pregnant ewes. Following infection, sheep develop immunity which will protect them against the disease in subsequent pregnancies

Steps to take during an outbreak

We need to remember that these abortion agents are zoonotic agents. This means they can affect humans, with pregnant women being at particular risk. Take care while handling aborted material and when returning back into the house. 

All aborted material should be removed quickly from lambing pens. This includes dead lambs, placenta, lambing gloves and straw or bedding. 

Aborted lambs and placenta can be used to take diagnostic swabs by your veterinary surgeon. Farmlabs has a very unique test to diagnose the cause of abortions. 

All ewes that have aborted must be isolated from the flock. They can be the source of infection with other sheep in the flock including lambs.

Diagnostic options

Having a diagnosis of which agent has caused your abortion can really make a big difference. 

For more information around our cutting edge science in abortion detection using swabbing, talk to your own veterinary practitioner.

Sheep Abortions

Laboratory tests for the causes of sheep abortion are an essential diagnostic tool which can save the farmer huge expenditure in money, time, and labour.  However, it is vital that the swabs for the tests are performed accurately.  This Farmlab video shows the procedure clearly and also explains it in clear and straightforward language.

BVD The Facts For Farmers


Our BVD eradication scheme is coming very close to our target of national eradication and we are seeing the real animal health benefits on farms.

While we have not achieved national eradication, significant progress has been made. We can also learn valuable lessons for future programs and their implementation. For now BVD tissue tag testing is a key component of this program as we get closer to eradication.

Talking to vets up and down the country one thing they have really begun to reflect on, is how much more healthy cattle are. One area where significant improvements have been made, are in improving calf health. This improvement in calf health is one of the real success stories of the program.

BVD virus works by suppressing the immune system amongst other things. When we tackle disease we are always trying to raise immunity and reduce infection. Removing this virus from circulation is critical to healthy cattle farming.

Lets remind ourselves on BVD the facts

  • BVD or bovine viral diarrhoea virus has an affinity for the reproductive tract of animals causing a range of diseases. It can cause severe immunosuppression in young animals. An animal’s immune system is so important in the fight against infectious bugs and pathogens.
  • There are two strains of the virus but we commonly see BVDv type 1 in Ireland
  • Animals who haven’t been exposed to the virus are extremely susceptible. This means while most Irish farms current risks are low it is extremely important to keep the disease out. Good biosecurity is important when we consider all infectious disease.
  • The virus can spread orally or by inhalation, it will usually migrate to the ovaries and womb of female cattle. This is important because it can pass through the placenta into the young calf.
  • The critical thing to remember is when this happens in the first 120 days of pregnancy the calf can become persistently infected. At this early stage the calf has no immune system developed so will it be persistently infected with the virus.
  • These calves may not survive and abort or can be born persistently infected. The tissue tagging we currently do is to identify these calves early and remove them.
  • Very occasionally the virus can cause deformities in the calf.
  • The virus also can have devastating effects at breeding time itself, with dramatic increases in fertility issues. This can be seen with poor conception, early embryo loss and usually farmers will see very irregular repeats or cattle returning on heat.
  • While persistently infected animals are a huge source of the disease, we can also get animals with transient infections. This is where healthy animals are exposed to the virus, they will show the effects like infertility or often in older cattle issues like respiratory disease.
  • While the BVD virus can cause problems on its own, its effect on depressing the immune system opens the door for other viruses and bacteria. We can often see this where we have really bad outbreaks of pneumonia even in older cattle.
  • Where a persistently infected calf is born they can really shed billions of viruses into the environment. These will then infect other calves in the herd (transient infections 3-4 weeks). This can be absolutely devastating where you get calf scours.
  • BVD virus can also infect bulls , they will often get a temperature spike and can become infertile
  • Remember good biosecurity pays long term, don’t buy in disease and always secure boundaries.

We are very close to eradication

Removing PI (persistently infected) animals has been a key part of the program through tissue testing. These animals are like virus factories and early testing and prompt removal is critical. While most of these PI animals will not make it to 2 years. Some will and can appear normal but will continually shed the virus.

Should I continue to vaccinate?

This is a question we commonly get asked about BVD. Vaccination has traditionally played an important role in the control of BVD. Vaccines are often administered in advance of breeding to protect the female animal and her future calf.

Every vaccine will have a specific protocol and must be followed. While the risk of BVD is extremely low now for most herds, our advice has been to talk to your own veterinary practitioners about your herds risk.

The challenge is now, as the vast majority of herds have no immunity or exposure and outbreak could be devastating. While we have BVD in our national herd even at very small levels, this makes anyone advising to drop a vaccine in a very difficult position.

Farmlab Diagnostics continues to develop its services to help vets and farmers have healthier livestock.

Farmlab Diagnostics is a leading  provider of animal health diagnostic services to the Irish agri-food industry. BVD testing is just one of the many diagnostic services we perform in our lab. To check out the full array of diagnostic services go to or contact us on (071) 9630792.

We also do special offers on larger volumes of testing, just pick up the phone to find out more.

BVD Virus

The number of BVD virus animals born has been reduced to 925 or 0.05% of calves born in 2019.

Bovine viral diarrhoea (BVD) virus in Ireland has been controlled as part of the National BVD Eradication Programme since 2012. In 2013 it became mandatory that all newborn calves were tissue tag tested for BVD Virus. Since that time the numbers of BVD positive animals have greatly reduced.  The number of BVD positive animals born in 2013 was 16,194 or 0.77% of the national herd. With three weeks left to go in 2019, the number of BVD animals born this year has been reduced to 925 or 0.05% of calves born. This is an incredible achievement, and of huge benefit to Irish national cattle herd.

Improved health and fertility on Irish cattle farms

The benefit of this reduction in BVD levels has been seen in improved health and fertility on Irish cattle farms. The reason for this is that BVD has a number of detrimental effects on bovine health and well-being. Two of the main effects are a reduction in immunity to other diseases and a negative impact on fertility. The negative impact on fertility may be seen as a failure to conceive, abortion, stillbirths, congenital deformities, or calves being born as persistently infected (PI) animals.

Identification of positive animals in positive BVD Virus herds

One of the main contributors to this dramatic reduction in calves born persistently infected with BVD is the identification of positive animals in positive BVD herds. This has been brought about by sampling every calf when it is born to see if it is infected with BVD virus (BVDV) or not. If the calf is infected then a decision is made on whether it is persistently infected or not. If it is persistently infected then it is removed from the herd, and so prevents the spread of the disease to other animals on the farm. This is particularly important in preventing spread to pregnant cows and heifers on the farm, and so eliminating the possibility of creating another generation of persistently infected animals on the farm.

Elisa testing and PCR testing

When the tissue tag is taken from the newborn calf it is sent to a designated laboratory for testing. All BVD designated laboratories are accredited to ISO17025 standard to carry out BVD tests on ear notch samples. Once received in the laboratory the sample is tested using one of two methods, ie either Elisa testing or PCR testing. Elisa testing works by identifying the erns protein which is present in the BVD virus. Persistently infected calves have the virus in all of their tissues as well as in their bloodstream, and so if the animal is positive for BVD it should be detected using the ELISA test. The other test which is used to detect virus positive calves is a technique called PCR testing. The full name for this is quantitative real-time polymerase chain reaction (qPCR) testing. This method works by detecting sequences of the virus’ RNA which are unique to that virus. This means that qPCR is a highly accurate means of detecting BVDV.

Sample Process

Once calves are tissue tag sampled, the tags should be dispatched to the laboratory as soon as possible, allowing the tissue sample to reach the laboratory within 7 days of being taken from the calf. Farmers sending tag samples to the laboratory should familiarize themselves with the postage requirements for these samples. From 2019 the minimum postage requirement on tissue tags sent in the post is €2.00. This usually allows up to 10 tags to be posted, but farmers should check this with An Post before sending. Once samples have been tested in the laboratory results are transmitted to the ICBF database, The ICBF database then sends a text message to the farmer notifying them of the test result

Bacteriological testing uncovers some “unusual suspects”

Wet weather and a bit of increased stress on cows has led to an increase in the number of cases of mastitis recently. This has led to an increase in the number of milk samples we have been looking at over the same period. Usually, the bacteriological cause of mastitis at this time of year is one of the “usual suspects” ie. Staphylococci or Streptococci. In most cases the cow has picked up one of these “bugs” at milking time, ie. these types of mastitis are generally contagious, meaning they spread from cow to cow, usually on the milking operators’ hands at milking or through the milking machine. Recently however when milk samples have been cultured and analysed in the lab, we have seen some cases of bacteria which are not the “usual suspects”

One such case was a mastitis sample which contained a pure growth of a particularly nasty bug called Pseudomonas aeruginosa . Usually this organism is present in the environment and is not the main cause of mastitis on farms, however in some cases it can cause mastitis in its own right. In these cases, the bacteria can gain entry to the udder from the housing, but also through the use of contaminated water in the milking routine. I call this a particularly nasty bug because when it was tested to see which antibiotic tubes were effective against it, we found that it was resistant to all except one of the routinely used antibiotics.

Another interesting cause of bacteria recently was a yeast called Candida albicans. Again, yeasts are not a major cause of mastitis, but sometimes occur after a cow has been treated on several occasions with intramammary antibiotics. The reason being that yeasts are not killed by antibiotics (as was the case with this one when we tested it in the lab). Recently we have become more aware that there is a natural biome of “good” bacteria in the teat canal which helps defend the udder from infection. Over-use of antibiotics may interfere with these defence mechanisms, and allow the overgrowth of yeasts.

Bacteriological culture of mastitis samples is the only way to identify these “unusual suspects”, and treating these sorts of cases without knowing what’s going on can make matters worse. The lead up to drying off is a good time to discuss with your vet about some monitoring of high cell count cows, or problem cows to build up a profile of the bugs present on the farm.

The vet can then use this information to help inform the decision on which are the correct dry cow treatments to use on the farm. There is a growing move towards selective dry cow therapy, where some of the cows on the farm are infused with antibiotics at drying off if needed, while others are left untreated. Carrying out selective dry cow therapy on a farm without knowing the causes of clinical or subclinical mastitis can be very dangerous, as you can get a big flare up in the incidence of mastitis on the farm in the following season, particularly if there are highly infectious organisms such as Staphyloccus aureus present on the farm.

Early Lambing – Investigating abortions in sheep

Early lambing is less popular than it was in our part of the world, but we have had some cases of sheep aborting in recent weeks. This mainly has been in pedigree lambing flocks where early lambing is still popular. One recent case involved a hogget delivering two malformed lambs which were premature and partially decomposed. Continue reading “Early Lambing – Investigating abortions in sheep”

Investigate the Reason for Chlamydia Abortus / Sheep Abortion

Please download a story in the Irish Farmers Journal where a Sligo vet discusses the causes of infectious abortion in sheep. The most common causes include Toxoplasmosis and Chlamydia. Both can be detected by a test provided by Farmlab and you can order the sampling kit here.

Continue reading “Investigate the Reason for Chlamydia Abortus / Sheep Abortion”

Testing for Infectious Bovine Rhinotracheitis (IBR)

Infectious Bovine Rhinotracheitis (IBR) is caused by bovine herpesvirus 1 (BoHV-1). This virus causes an acute upper respiratory tract disease which can lead to fatal pneumonia. Infection can also cause a severe and prolonged drop in milk yield, reduced fertility and abortion. Continue reading “Testing for Infectious Bovine Rhinotracheitis (IBR)”

What is Bovine Viral Diarrhoea (BVD) in Cattle?

Bovine Viral Diarrhoea (BVD) in Cattle

BVD is a viral disease of cattle, caused by a pestivirus, called Bovine Viral Diarrhoea Virus (BVDV). BVDV can infect cattle at any stage of their lives, resulting in impaired immunity thereby weakening the immune system and leaving the animal susceptible to other infections at the same time. This can be particularly pronounced in the case of cattle which become concomitantly infected with other respiratory viruses, such as IBR. Combined infection with IBR and BVD can cause a severe fulminating pneumonia and potentially death. Continue reading “What is Bovine Viral Diarrhoea (BVD) in Cattle?”

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