Identifying how digital dermatitis is transmitted between dairy cows (PhD)

Summary/Key points:

When considering wintin host (animal) infection reservoirs other than within the foot leion:

• Digital dermaitis (DD) treponemes were identified in the bovine gastro-intestinal (GI) tract, primarily the gingiva and recto-anal junction (RAJ)
• DD treponemes do not appear to cause damage to the host in the GI tract.
• DD treponemes were able to be cultured/isolated from faeces demonstrating evidence for faecal shedding as one route of transmission.
• DD treponemes have the ability to survive in sterile faeces for a median of 1 day and a maximum of 6 days which would enable transmission of viable bacteria to another animal’s foot.
• Given involvement with the GI tract and faeces, increasing hygiene on farm should help to reduce DD on farm.

• Fomites:
  • The DD treponemes were detected in dairy cattle fomites (surfaces touched by affected feet/lesions)
    • including hoof trimming knives, trimming equipment, gloves and in footprints 
  • Fomites should be considered important infection reservoirs.
  • Improving biosecurity and foot trimming practices should help reduce disease spread. 
• Bedding:
  • DD bacteria were not viable in straw or sand containing 5%(w/w) lime in the laboratory
  • DD bacteria can remain viable in recycled manure solids (RMS) for 5 days, sawdust of 6 days and sand for at least 7 days
  • To reduce to the risk of DD transmission the preferable bedding is straw/sand containing 5% lime

Aims and Objectives:

• To identify and characterise specific associations between bovine digital dermatitis (BDD) treponeme transmission, the bovine host and the dairy environment.
• Specific objectives:
  • Development of enhanced DNA extraction techniques to aid detection of BDD treponemes
  • Survey of cow and dairy farm samples for BDD treponemes using PCR, treponeme isolation and immunohistochemistry
  • Understanding the ability of BDD treponemes to survive and grow in the dairy environment and under different host conditions
  • Investigate the association of BDD treponemes with healthy foot tissues