Lame - Foot pathology Flashcards
What are some diseases that can cause laminitis in horses?
Equine pituitary pars intermedia dysfunction
Equine metabolic syndrome
Endotoxaemia
Colic
Hormonal dysfunction
What are the predisposing conditions for laminitis usually associated with?
Systemic inflammation
Vascular compromise
Hormonal imbalance
What is the pathogenesis of laminitis?
Unknown
Thought to be to do with reduction in laminar capillary perfusion
Shunting blood increasing hydrostatic pressure and causing laminar oedema
Increase inflammatory cells embolising in laminar vessels
Dermal-epidermal junction breaks down
What does break down of the dermal-epidermal junction and inflammation of the laminae cause in laminitis?
Rotation of the third phalanx ventrally towards the sole
What is navicular syndrome?
A common degenerative disorder of the distal sesamoid - navicular bone
What limbs are most often affected by navicular syndrome?
Forelimbs - usually bilateral
What is thought to be contributing factors to navicular disease?
The shape of the navicular bone and the angle of the hoof
The pathogenesis is not completely understood however
What is found between the navicular bone and the deep digital flexor tendon?
Navicular bursa - synovial joint-like space lined with synoviocytes
What is thought to occur in navicular syndrome?
The deep digital flexor tendon compresses the navicular bone when pushing off the ground
This leads to abnormal wear and tear
Causes loss of cartilage and subchondral bone
Granulation tissue, fibrosis and osteophytes form
Damage to the deep digital flexor tendon
What is foul in the foot/foot rot?
Infectious bacterial disease of the interdigital skin of the bovine feet
Is foul in the foot contagious? What causes it?
No - more due to poor sanitation and recent calving
Previous injury to the skin allows infiltration of bacteria
What is the primary pathogen of foul in the foot/fot rot?
Fusobacterium necrophorum
What are two other bacteria that can accompany fusobacterium in foul in the foot/foot rot?
Porphyromonas and prevotella
Other bacteria can also infect too
What does each bacteria do to cause foot rot?
Fusobacterium cause tissue necrosis
Porphyromonas delays immune response
Prevotella forms biofilm to protect other bacteria
What are the steps of foot rot?
Skin abrasion allows fusobacterium in
Hyperaemia and swelling occur
Tissue necrosis
Fissures form
Secondary invasion and abcess formation
Infection spreads to deeper structures - sepsis
What are common complications of foot rot?
Septic arthriitis of distal interphalangeal joint
Navicular bursitis
Osteomyelitis
What disease is similar to foot rot?
Digital dermatitis
Is digital dermatitis contagious?
Yes
Where are digital dermatitis lesions usually found?
On the plantar surface of the hind foot in dairy cows
What causes digital dermatitis?
Constant exposure to manure and urine in unhygienic environments
What bacteria cause digital dermatitis?
Treponema
Then fusobacterium, dichelobacter
What happens in digital dermatitis?
Constant exposure to manure and urine
Structural breakdown and dermatitis at skin-horn junction
Treponema invade
Neutrophils are recruited which cause keratinocytes to proliferate and slough
Skin ulcerates and proliferates with mass like projections along coronary band which easily bleed
Where do sole ulcers most commonly affect?
The lateral claw of the rear hoof
What are the predisposing causes of sole ulcers?
Housing
Nurtrition
Foot trimming
Genetic conformational problems
What tends to cause sole ulcers to occur?
Mechanical injury to the corium secondary to weakened suspensory ligaments
Third phalanx sinking and compressing digital cushion
What causes weakened suspensory ligaments?
Pregnancy hormone related - cortisol, relaxin, oestrogen and prolactin
What causes heel sole ulcers?
Overgrowth of the outer claws in the hind limbs
What are the stages of heel sole ulcer formation?
Accelerated growth at the heel of the lateral claw
Cow puts weight on medial claw
Horn overgrowth at digital space
Concussion of corium
Ulcer forms
What predisposes to white line disease?
Diseases that disrupt blood flow to corium
So weakened defective horn is produced
Foreign material can separate white line mroe easily
What are the consequences of a foreign object in the white line?
Bacteria colonise the white line horn and destroy it
Infection reaches corium and abcess forms
Abcess might drain out, or may cause infection of deeper structures
