How to keep disease out of your dairy herd

Wherever there are cattle, there is always a risk of disease threatening the herd. An endemic disease is one which is constantly present, and these diseases cost the UK dairy industry millions per year¹.

Colin Mason, Veterinary Centre Manager at SRUC, explains which endemic diseases pose the biggest threat to UK dairy herds and how farmers can manage them.

What is an endemic disease?

An endemic disease is one which is always present in a population of animals or a geographical area.

Key examples in UK dairy herds include:

• BVD
• IBR
• Leptospirosis
• Salmonella Dublin infections

These endemic diseases can theoretically be eradicated and kept out. Others are more difficult to fully eradicate due to the nature of pathogens being present in the environment - such as cryptosporidia in calves. To control endemic diseases, farmers need to focus on an immunity-led, preventative approach.

How do endemic diseases impact dairy herds?

Endemic diseases all impact performance, welfare and profitability, meaning it’s worthwhile for every farmer to take steps to manage them.

Clinical diseases can present themselves in various forms; from very severe to subclinical, meaning it doesn’t show any visible signs but may still contribute to performance issues and potentially be passed on to healthy animals.

For example:

• Salmonella Dublin can have severe disease symptoms, such as scour, death, and abortion, but can also be quite subtle, causing reduced performance in calves or cows.
• Leptospirosis remains common, particularly in naïve cattle who have not received a full vaccination programme. With reports of infection in 70% of dairy farms¹, it can cause abortion and milk drop.
• IBR can cause respiratory disease, milk drop and abortion. Cattle often carry the causal virus, bovine herpes type 1, which can be activated when they are under intense periods of stress or in negative energy balance. This is where you could see subclinical or clinical symptoms appear, resulting in production losses. 

How can farmers control endemic diseases?

Key aspects of herd health planning to control endemic diseases include knowing and managing what you’ve already got in the herd and knowing what diseases are not present, the risks that might pose and how to keep it out.

To start more active herd health planning, break it down into bite-sized chunks and begin with the disease having the biggest impact. It’s essential to know what diseases are present - screening and diagnostics are essential parts of a herd health plan.

How can you test for endemic disease?

Accurate diagnosis is key. Discuss sampling strategies with your vet. It can be as simple as a swab from an affected cow’s nose to get a good sample for disease testing. Negative results for infectious disease are very useful to help rule things out.

Abortion screening is also a useful tool for diagnosing infectious disease because Salmonella Dublin, IBR, Leptospirosis and BVD can all cause abortions in cattle. A level of 2-3% abortions is normal but, generally, if it’s above that it should be investigated.

What are the risks of endemic disease?

You need to balance the level of potential harm a disease can do to the herd with the risk of it actually happening.

Risk levels vary between closed, flying or expanding herds, those that are housed all-year-round and those with rented grazing away from the farm, or a family workforce compared with teams drawing in labour from different locations.

None of these are necessarily bad or good, they are particular to each farm - you need to make a judgement about risk based on your own situation.

How can farmers reduce the threat of endemic disease?

To manage the risk of an endemic disease like IBR entering or re-entering a herd you will need to focus on biosecurity, which will help reduce spread between herds – such as:

• A quarantine policy if stock are bought in
• Good boundary fencing
• Minimal risk of people coming in contact with the herd

How can vaccination protect herds against endemic disease?

Vaccination is the foundation of any preventative herd health strategy and provides a useful insurance policy alongside biosecurity protocols and husbandry management.

When considering whether to vaccinate, current health status and risk of the disease entering the herd if it is disease-free should be discussed with your vet.

Is it possible to eradicate endemic disease?

Eradication can be worked towards for some diseases. Aiming to remove targeted diseases and then keep them out through vaccination and a good biosecurity programme should be a long-term aim.

With BVD, we now have strategies based on identification and removal of persistently infected cattle (PIs) and vaccination to maintain immunity.

For IBR, if you know you only have a small number of carriers in a fully closed herd, the best strategy is probably to remove them, then work with your vet to decide whether to vaccinate or not.

However, a lot of herds will have a large proportion of animals carrying IBR and/or high risk of bringing it back onto the farm in which case they could set a goal to gradually keep removing carriers over a number of years along with vaccination.