infectious causes of lameness Flashcards
describe this lession
location: interdigital (plantar aspect)
number and extent: Single focal lesion, ulcerated
Shape: 3cm circular
Colour: red
what species are affected by digital dermatitis?
What is the impact of DD?
- cattle, sheep, goats
- now endemic in the UK
- herd prevalence can exceed 30% (up to 50%)
Impact:
* welfare - painful active stages)
* decreases farmer morale as difficult to manage
* Economic
* small amount of milk loss
What is the aetiology of Digital dermatitis?
Three groups of anaerobic spirochetes bacteria repeatedly found in lesions:
* Group 1 – Treponema medium / vincentii-like
* Group 2 – Treponema phagedenis like
* Group 3 – Treponema pedis
also other opportunistic bacteria and Bovine foot microbiome
What is the survival time of digital dermatitis?
- Aerobic bovine faeces for 1 day (15 min-6 d)
- Viable on hoof knife blades for 2h
- Survive in pH 5.5–9.0 anaerobic culture
- Not viable after 15min in aerobic straw or sand (5%lime)
what is the epidemiology of Digital dermatits?
- Lesion on infected animal main reservoir (possibly only?)
- The slurry may be a reservoir of infection (footprint)
- Lesions can develop within 21 days (inoculation)
- Initial skin pathology to clinical lesion: 133 days (average)
what are the clinical signs of digital dermatitis?
Lesions on the feet
* Typical: appear on the plantar surface of the hindfoot (95 %) but can occur on front feet
* Occasional: heal bulb, interdigital space between claws, coronary band at the front of the foot, around accessory digits
- Mild lameness –> Moderate/Severe if not treated
How is digital dermatitis scored?
Mortellaro score (M-score):
M0 stage - normal healthy skin, no visible lesion, no sign of DD
**M1 stage **- Early stage, Focal active, Red-grey, Less than 2 cm ⌀
**M2 stage **- Acute, Bright red, Ulcerative, Painful lesion, More than 2 cm ⌀
M3 stage - Healing, Non-painful, Firm brown/black scab, Often seen after topical treatment (inactive)
M4 stage- Chronic stage, Non-painful, (inactive) Dys/Hyperkeratotic overgrowth, Brown-gray colour
M4.1 stage - Chronic M4, With reactivation M1
How is digital dermatis diagnosed?
- Observation in a trimming chute is considered the “Gold standard”
- scoring the feet in a milking parlor - feet must be clean,
- can use a mirror or boroscope for better view
- bulk tank milk - ELISA test (not widely used)
- Thermography (not used expensive)
What is treatment of the different stages of digital dermatitis?
- M1 (small active) - Non-antibiotic treatment (i.e.Chelate copper-zinc Gel /salicylic acid powder )
- M2 (severe lesion) - Spray licensed antibiotic (oxy/chlro- tetracycline, thiamphenicole)
- M3 (healing lesion) - No treatment
- M4 (chronic) - Non-antibiotic treatment (i.e.Chelate copper-zinc Gel /salicylic acid powder )
- M4.1 (reactivating) - Non-antibiotic treatment (i.e.Chelate copper-zinc Gel /salicylic acid powder )
in one study what percentage of cows with server lesions were lame? what is the implication of this?
Only 39% of cows with severe lesions are associated with lameness, with the risk of underestimating the BDD true herd prevalence
therefore need to look at the feet as score them regularly as can’t rely on lameness, look at the feet and score them in the parloer
What is the treatement of an individual cow with digital dermatitis?
- Clean, remove matted hair and “scab”
- Dry the lesion
- Apply topical
- Antibiotic/Non-antibiotic treatment
- -/+ bandage… remember to remove!
- Repeat applications (e.g. 3 days) to improve recover
- provide NSAIDs if painful
Parenteral antibiotics are effective but may not be cost-effective or justifiable (appropriate use) penicillin, amoxicillin, oxytetracycline
What is the prognosis of digital dermatitis?
- Good
- Except lesions on the front of foot –> Damages periople –> Impairs production of wall –> Under running
- Newer presentations may be more difficult to treat
What is the herd approach for the preventions/treatment for digital dermatitis ?
foot bath
* one litre of solution per cow passage,
* 12cm deep
* long enough for all 4 feet (3 metres)
Chemicals:
* Copper sulphate (4-5 %)
* Formaldehyde ( 2-4 %)
What are the risk factors for Digital dermatitis?
- enviromental hygeine
- stocking density
- cleanliness score and hock score (cleanliness)
- footbath
- flooring
- foot triming equipment
- biosecirity
- moisture (macerates skin)
- Parity and lactation (younger cow less prone, dry cow less prone (bedding cleaner)
What is the aetiology of interdigital necrobacillosis?
- “Foot Rot”, Foul”, “Claw Ill”, “Lewer”
- Fusobacterium necrophorum (Gram-negative); two subspecies:
- F. necrophorum ssp necrophorum (formerly biotype A)
- F necrophorum ssp funduliforme (formerly biotype B)
- Synergically acting with Porphyromonas levii and Prevotella intermedia
What are the clinical signs of interdigital necrobacillosis?
- Damage to the skin – rough underfoot condition e.g. stubble, course straw
- Sudden onset moderate to severe lameness
- Anorexia, drop in milk yield, weight loss and pyrexia
- Swelling of soft tissues above and around the coronary band and between the digits
- Hot, inflamed and painful
- “Split” in interdigital space, which discharges pus and necrotic tissue
- Characteristic foul smell
- Swelling may track higher up the leg as the infection invades
What are the risk factors for interdigital necrobacillosis?
- Poor surfaces (abrasive/cutting, such as stones, poor tracks)
- Poor hygiene
- Worm, moist environmental conditions
- Other causes of lameness increase the risk of the disease
- Beginning of lactation (metabolic status)
How is interdigital necrobacillosis diagnosed?
- Signs are pathognomonic once the foot is examined
- Swelling of the soft tissue
- Painful at palpation
- Severe lameness (AHDB score 2/3)
- Swabs/biopsy can be used (suitable transport medium) (but not normally done)
What is the treatment of interdigital necrobacillosis?
- Wash and flush with plenty of clean water
- Debridement of necrotic tissue if present
- Parenteral antibiotics for 3-5 days (NB responsible use!!!)
- Sulphamethoxypyridazine
- Oxytetracycline
- Penicillin/streptomycin combinations
- Tylosin (cat C)
What is the prognosis of interdigital necrobacillosis?
- Good if treated early…Otherwise very poor
- Deep digital sepsis can result in aggressive cases or if left untreated
- Progression of the swelling can cause separation of the digit
What is the main clinical difference between DD and interdigital necrobacillosis?
interdigital necrobacillosis has swelling of the foot
