Preventing Clostridial Disease

Clostridial disease poses a serious threat to unvaccinated sheep. With vaccines costing as little as 50p a head, it is not a risk worth taking ahead of the lambing season. 

Last year, saw a number of vaccine supply issues. We have not heard that this will be the case again this year, however, may be wise to think ahead with numbers.

The National Office for Animal Health (NOAH) categorises vaccination for clostridial disease as the highest priority for sheep. This means flocks should be vaccinated as a default unless your vet deems otherwise. 


What is clostridial disease and what triggers an infection?

Clostridial diseases are caused by organisms called clostridia that live in the environment, most commonly soil, for a long period of time. 

Most of the organisms occur naturally in the gut of a healthy animal and pasture becomes contaminated via faeces. 

Vaccination advice

Most vaccines require ewes to be given an initial course, then a booster four to six weeks before lambing to ensure their offspring obtain sufficient passive immunity – whereby antibodies are transferred from the ewe to her lambs. 

The duration of protection differs depending on which vaccine is used and the type of clostridial disease. 

Typically, passive immunity against blackleg – one of the most common clostridial disease – only lasts about two weeks, so farmers shouldn’t delay in vaccinating lambs with their primary course. 

Get in as early as you can with the vaccine to make sure lambs have protection. Most vaccines can be used from three weeks of age. 

Vaccine timing can be difficult to coordinate when catering to a wide age range of lambs, but it can be achieved after discussion with your vet. If you can do them in groups, then do them, or, if you can’t, you must consider when your biggest risk period is and treat lambs before this. 

It’s about speaking to your vet and deciding the best timing for your flock. The biggest danger is thinking you don’t have clostridial disease and doing nothing. 

It’s not uncommon to see blackleg on farms that have never had previous issues, including farms which can go years and years without an issue, and they might start using a new field and they will get an outbreak. 

Other key points to remember when vaccinating: 

  • Avoid needle contamination 
  • Reduce stress where possible 
  • Dry fleeces make vaccination more effective 
  • If you have a long lambing block, consider splitting ewes into two groups to maximise protection for later lambing ewes 

Colostrum management

Good colostrum management is also key to ensuring lambs receive adequate protection within the first few weeks of life. If you vaccinate your ewes, but lambs don’t get enough colostrum, they won’t get protection.  

Lambs must have 50ml per kilo of liveweight within the first two hours of birth – for example, lambs weighing 4kg must drink at least 200ml - this is not easy to quantify, but a simple test is checking the lamb has a full belly.  

Colostrum must also be good quality, and to test this, you can use a refractometer to ensure colostrum offered measures more than 22%. It is not necessary to test every ewe – a percentage of the flock is adequate – depending on your flock size, as well as how many groups are run and how many rations are fed. 

By the time you have colostrum, there’s not a lot you can do about it; you’ve got what you’ve got. But if colostrum is poor quality, and you have more to lamb you can adjust their diets, or it might be a good reason to vaccinate lambs early. 

There’s no substitute for ewe colostrum and seeing that lamb up and suckling in the first few hours. 


Sudden deaths should always be investigated with a post-mortem. Often, the first time the post-mortem comes back inconclusive which is frustrating, so farmers often give up. But if you don’t do the first one you can’t do the second, so we’d encourage people not to give up. Remember, finding out what hasn’t caused the death can be just as important as finding out what has. 

Get carcasses sent off as quickly as possible to get the best results and keep them cool to prevent decomposition.  

1st December 2023

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