Alice Bathard (FCG WhiteAvon)

I recently attended an AHDB event in Wiltshire about Johne’s and how to manage the disease.  The talk was delivered by NMR Johne’s Expert Karen Bond who explained the science behind the disease and the struggles farmers face with managing it.  Tom from The George Vets then gave the Johne’s background of the host farm and how they implemented changes to help manage the disease within their herd.

The clinical signs of Johne’s include persistent scouring and weight loss.  However, due to many years of Johne’s management, clinical signs of Johne’s on farms are becoming increasingly rare.  MAP causes damage to the animal’s intestine, preventing it from properly absorbing water and nutrients.  The disease spreads primarily through faeces, making good hygiene and manure management critical for control.

One of the main challenges with Johne’s is that MAP can hide inside white blood cells.  This means that testing young animals is often ineffective, as the infection may be present but undetectable for long periods of time until the immune system responds.  During stressful periods—such as calving—the cow’s immune defences weaken, allowing MAP to emerge from hiding and spread within the body or to other animals.  Once the immune system responds and antibodies are produced, the bacteria can retreat again into the white blood cells for protection.  This cycle of dormancy and activity can lead to fluctuating test results, so one negative test does not necessarily mean an animal is free from Johne’s.

Managing Johne’s in your herd – tips from Karen and Tom

Cows with Johne’s often have other underlying issues such as reduced milk yield, high somatic cell counts, or lameness.  Many infected animals are culled for these reasons before showing clear clinical signs of the disease.  However, culling is not always the only option.  Any cow that has ever tested positive—even if later results are negative—should be managed carefully to reduce the risk of spread.  This includes avoiding the use of sexed semen for replacement heifers and ensuring segregation during calving.  MAP spreads through infected faeces, which makes it difficult to reduce the chances of infection for calves born from these cows.  However, breeding only beef calves, and having separate Johne’s calving pens is a simple change which can have the largest impact on herd health.

When disinfecting, it’s important to use suitable chemicals at the TB disinfection rate, as MAP’s thick cell wall makes it highly resistant.  Lime, for example, is shown to be ineffective against MAP when using to disinfect calf pens.

While farms can achieve low-risk or Level 1 Johne’s status, it is highly unlikely that any herd is completely free of the disease.  Ongoing vigilance, testing, and good biosecurity remain key to managing Johne’s effectively and protecting herd health.

Will Johne’s ever be eradicated?

Within the last 15 years or so, Johne’s has significantly changed in the way it affects farms and herd health.  Clinical signs are far rarer than they were back then, which is a positive direction, yet the disease does still exist within herds today.  Johne’s will probably always be in herds, but hopefully it can become a disease which is an inconvenience rather than a huge problem for farms.

To discuss any aspects of Johnes, contact Alice at alicebathard@fcgagric.com or your Vet.