Lecture 5: Infectious Diseases

what is this?

digital dermatitis

what is this?

heel erosion

what is this?

foot rot

digital dermatitis

• “hairy heel wart”

• dairy cattle

• 70-95% of dairy farms affected in NA

• confinement housed → high prevalence

• pasture based → low prevalence

• early lactation cows and heifers at higher risk

• increased days open

• reduction in milk production

digital dermatitis etiology

• spirochetes → bacteriodes, campylobacter, fusobacterium, peptococcus

• spirochetes (treponema)

what feet are affected by digital dermatitis?

• rear feet (>90%)

• plantar interdigital cleft → shifts weight bearing to the toe

• corium → “hairy attack”

what are these showing?

digital dermatitis

what is this?

DD of corium (hairy attack)

what is this?

hair-like projections from digital dermatitis

digital dermatitis risk factors

• muddy or wet conditions

• replacement heifers or cows from other farms

• exhibition cattle

• host genetic factors

• not washing hoof trimming equipment between cows

• outside hoof trimmers

• presence of other infectious disorders

• chronically infected cows can act as a reservoir

digital dermatitis in beef cattle

• more common now

• one study showed 4% prevalence

digital dermatitis treatment for individual cases

• clean lesions (soap and water)

• check for other foot issues

• topical antibiotic → oxytetracycline with bandage

digital dermatitis treatment for herds

• clean with water under pressure

• foot bath → formaldehyde, copper sulfate, antibiotics

digital dermatitis prevention

• no vaccine available

• foot baths

• improve environmental hygiene

• automatic washing of hooves

• biosecurity → check for lesions

copper sulfate foot bath

• not fully effective if organic material is present (manure) (10-20%)

• negative impact on environment

• can contribute to high copper intake

formaldehyde foot bath

• 3-5%

• effective in 20% manure

• greater than 5% concentration can cause skin chemical burn

• poor activity at low temps (<50F)

• worker safety due to fumes

• turns to water so no risk for disposal

foot bath design and maintenance

• in parlor system

• change every 150-300 cows

• ideally 10ft long x 3ft wide x 6 inches deep

advantages to digital dermatitis foot baths

• good access to lesions in interdigital space

• convenient

disadvantages to digital dermatitis foot baths

• hard to keep clean and correct concentration

• cost

• inefficient if low % affected

advantages of digital dermatitis sprays

• less copper content waste

• cost

disadvantages to digital dermatitis sprays

• labor

• poor access to interdigital space

• risk of milk contamination

what kind of sprays are used for digital dermatitis treatment?

oxytetracycline and lincomycin

digital dermatitis prognosis

• most cattle respond to treatment

• positively correlated with cleanliness of farm and early treatment

• negatively correlated if more than one limb affected

interdigital dermatitis

• superficial dermatitis of the interdigital skin

• often found with DD and heel horn erosion

• may be painful to touch

• may not cause lameness

• more common in rear feet

• prevention → foot bath, hygiene

what is this?

interdigital dermatitis

interdigital hyperplasia

• proliferative growth that may occupy part or all of the interdigital space

• rarely causes lameness

• usually result of chronic skin irritation

risk factors for interdigital hyperplasia

• dermal inflammation

• late treatment of foot rot

• slurry/poor hygiene

• rocky pasture

• poor conformation

• hereditary predisposition

• more common in heavy cows

• improper trimming

what is this?

interdigital hyperplasia aka corn, interdigital fibroma

what are these?

corns

corn removal

• foot anesthesia

• pull claws apart

• grab corn with towel clamps

• excise corn

• apply bandage with topical oxytetracycline

interdigital necrobacillosis (foot rot)

• aka interdigital phlegmon, foul in the foot

• mixed bacterial infection of soft tissues (anaerobes)

• can lead to ascending infection of tendons and joints

what is this?

interdigital necrobacillosis

foot rot is primarily caused by

fusobacterium necrophorum

foot rot bacteria

• present in GI flora of cattle and environment

• enters through defect in the interdigital skin

• virulence factors

• macerated skin + injury/trauma = infection

what is this?

foot rot

fusobacterium necrophorum causes

suppurative necrotic cellulitis

clinical signs of foot rot

• swellings → claws spread, coronary band, joint distension

• lameness

• foul odor

• sloughing, fissuring and necrosis of interdigital space

• minimal pus

• risk of invasion of soft tissues and coffin joint → septic arthritis

contributing factors for foot rot

• usually only affects one foot

• wet conditions → pasture cattle in mud and ponds, confined cattle in mud

• trauma → stones, stubbles, manure, pieces of wood

• organism may survive in environment for 1-10 months

foot rot treatment

• early detection is key

• clean and debride interdigital space

• parenteral antibiotics

• response rate is usually 70%

• foot baths

foot rot prevention

• minimize muddy, wet conditions

• minimize access to ponds

• good free stall, pen hygiene

• reduce fecal contamination

• vaccines → 2 available

prevention of infectious foot diseases

• difficult

• reduce conditions needed by microorganisms to reproduce

• correct underlying factors affecting the immune system

tenosynovitis

• usually from ascending infection or penetrating wound

• causes severe lameness

• can compare distance between dewclaws

• treatment is long, claw block, lavage

what is this?

tenosynovitis

pedal osteitis

• inflammation and demineralization of P3

• secondary to other hoof problems

• severe lameness, chronic

• hoof trimming, deep toe/sole ulcer

• irregular margins of P3

• loss of bone density, sequestrum

treatment of pedal osteitis

• bone curettage, sequestrum removal

• claw amputation, facilitated ankylosis, cull

what is this?

pedal osteitis

foot rot and osteomyelitis

• extension into the coffin joint

• radiographs recommended

• chronic or septic arthritis

what are these showing?

foot rot and osteomyelitis

treatment for infectious foot diseases

• topical antimicrobials → foot bath, topical spray, topical with bandage

• parenteral antimicrobials

• pain management

treatment for non-infectious foot diseases

• corrective trimming

• block placement

• pain management

• bandaging

septic arthritis

• more common in neonates → bacteremia, septicemia, or umbilical issue

• warm, swollen, painful joint

• synovial fluid analysis → increased leukocyte and protein count

• most commonly affects hock, stifle, and carpus

• more than one joint may be affected

treatment of septic arthritis

• joint lavage

• regional limb perfusion

• sometime nonresponsive

what is this?

septic arthritis

clostridial myonecrosis (blackleg)

• Cl. chauvoei, Cl. septicum

• any muscle at risk but limbs most common

• ubiquitous in soil, GIT, feces

what is the most potent of all clostridial species?

Cl. sordellii

what is this?

clostridial myonecrosis

black leg

• C. chauvoei

• any site, but most commonly thigh, rump, loin or brisket

• if alive, see lameness, depression, anorexia, rumen stasis, fever, reluctant to move

• SC emphysema, swollen, initial heat and pain, late cold and painless

• rapid prostration, shock, coma, and death

malignant edema

• C. septicum

• deep wound or traumatized sites such as repro tract or udder

• signs like blackleg but more edema

• rapidly spreading edema following fascial planes

• death in 24-48 hours

what is this?

malignant edema

black neck

• C. sordellii

• most in feedlot animals

• found dead

• massive black hemorrhage and muscle necrosis at base of neck and brisket

what is this?

black neck

clostridial myonecrosis

• cattle

• 4-24 months, occasional adult

• warm seasons, often at pasture

• wounds, trauma, bruising, dystocia

clostridial myonecrosis post-mortem

• rapid autolysis

• odor (rancid butter)

• bloody discharge from body orifice

• swelling and crepitus

• necrotic muscle tissue and edema

• signs of systemic toxemia

treatment of clostridial myonecrosis

• horses have best prognosis (guarded) with all others grave

• antibiotics → penicillin, tetracyclines

• anti-inflammatory drugs

• IV fluids

• aggressive debridement and fasciotomy

prevention of clostridial myonecrosis

• sanitation → proper disposal of carcasses, burning, burying

• vaccination → at least 2 initial doses, annual booster at minimum

clostridium tetani

• wounds, parturition, tail docking, ear tags, dehorning, elastrator bands

• exotoxins → clinical disease

clinical signs of early clostridium tetani

prolapse of 3rd eyelid, rigid muscles around head and neck

clinical signs of late clostridium tetani

sawhorse stance, pump handle tail, stiff gait, extended head, bloat

clinical signs of the latest form of clostridium tetani

tonic muscle spasms, death

what are these showing?

clostridium tetani

treatment for clostridium tetani

• muscle relaxation → sedatives, not stimulus, muscle relaxers, Mg

• supportive care → bedding, food, water

• infection → penicillin

• neutralize → antitoxin

• prognosis is 50%

prevention of clostridium tetani

vaccination with toxoid