Sheep (S-) strain of Johne’s disease (JD) in cattle

Page last updated: Monday, 15 April 2019 - 12:06pm

There are three strains of the bacteria, Mycobacterium avium subspecies paratuberculosis, that cause Johne’s disease (JD): sheep/ovine (S-), cattle (C-/bovine) and bison strains.

S-strain usually infects sheep but can potentially infect other JD-susceptible species, including cattle.

S-strain of JD and cattle

  • S-strain of JD is endemic in the Western Australian sheep flock and cannot be eradicated.
  • S-strain of JD in cattle has been detected in Australia.
  • In Australia, studies have indicated that there is a low-risk of transmission of S-strain from sheep to cattle, however, transmission can occur sporadically.
  • There is no proven transmission of S-strain between cattle.
  • As of 15 April 2019, WA has had three clinical cases of S-strain in cattle, with the first in a cow in 2013. 

What happens when S-strain is detected in cattle in WA?

All strains of JD, including S-strain, are reportable diseases. The Department of Primary Industries and Regional Development (DPIRD) must be notified.

No regulatory actions are implemented on a property if cattle are detected with S-strain. However, the detection is recorded against the property identification code (PIC) and this is taken into account when undertaking Property of Origin certification for JD-relevant markets.

What effect does S-strain detection have on my Johne’s Beef Assurance Score (J-BAS)?

If a laboratory test for a J-BAS 7 or 8 property confirms S-strain JD with no clinical signs, the property J-BAS will revert to a score of 6, provided the other requirements of J-BAS 6 are met. The property will be eligible to retest in two years, after the last high-risk animal(s) are removed, to progress to J-BAS 7. Producers should see the JD in Cattle Biosecurity Checklist for more information.

Risk factors for S-strain infection in cattle

The highest risk of introducing any strain of JD onto property is through introduction of infected animals. Other factors that increase the likelihood of S-strain spread from sheep to cattle include:

  • increased stocking densities
  • co-grazing cattle, especially cattle under one-year-old, with sheep shedding the bacteria
  • grazing cattle on pastures contaminated with S-strain
  • climatic conditions that facilitate survival of S-strain in the environment (such as higher rainfall areas).
  • indirect exposure of cattle to run-off from pasture contaminated with S-strain in sheep (whether from same or neighboring properties)
  • drought-feeding and hand-feeding sheep and cattle (grazing close to the ground and faecal contamination).

Managing the risk of S-strain infection in cattle

  • Avoid co-grazing cattle, particularly calves under one-year-old, with sheep. Consider vaccinating sheep by 16 weeks of age to minimise the JD risk from sheep.
  • Determine the JD status of sheep on the property through on-farm testing or abattoir monitoring.
  • If there is JD on the property, minimise the potential risk of exposure infection through the culling of infected livestock, grazing management and, if appropriate, vaccination of lambs for JD.
  • Prioritise high-risk sheep for culling including: clinical cases, suspect clinical cases, dam, test-positive animals and animals originating from high-risk sources.
  • Do not graze young animals in high-risk areas including next to neighbours with JD in sheep.
  • Do not graze cattle less than one-year-old on pastures that have been grazed by sheep, particularly not pastures grazed by sheep with JD.
  • Do not hand-feed cattle and sheep together.

Contact information

Jamie Finkelstein
+61 (0)8 9368 3805