L4- Bacterial diseases Flashcards
superficial pyoderma
One of most common diseases in dogs
• Bacterial skin disease is more common in dogs than other species
• Involves the epidermis and superficial
portion of hair follicle
• Staphylococcus sp. usual culprit
• Short duration, heal without scarring or
systemic issues
• Papules, pustules, crusts, epidermal
collarettes
• Diagnostics: culture, cytology
bacterial: Deep pyoderma
Involve the hair follicle, dermis, and/or
subcutis
• Heals with scarring
• Usually associated with lymphadenopathy or other
systemic signs
• Tissue swelling, raised nodules, draining tracts,
exudate with crusting, ulceration
• Often painful
• Staphylococcus sp. are most common cause
• S. pseudointermedius is common cause in dogs
• May be cause of pastern dermatitis in horses • Diagnostics: culture
greasy pig disease
Caused by Staphylococcus hyicus
• Gram positive cocci, normal skin flora
• Fatal, generalized exudative epidermitis in neonatal
pigs
• Thought to be induced by trauma to skin – exact
pathogenesis unknown
• Virulence factors – exfoliative toxins and
metalloproteases
• Intraepidermal cleavage
• Macules around eyes, nose, lips, ears
• Exude greasy sebum, can become crusty
• Greasy exudate over body
• May see lesions at coronary band
dermatophilosis (rain rot)
Dermatophilous congolensis
• Gram positive facultative anaerobe
• Most common in hot humid areas with heavy rain • Cattle, sheep, goats, horses
• Two factors: trauma to skin and prolonged
wetting
• Bacteria invade in epidermis and hair follicles
painful
• Thick laminar crusts, hyperkeratosis
• Papules and pustules à crusting and scabbing –
• Face, axilla, inguinal regions, distal limbs, dorsum
• Diagnostics: biopsy
abscesses
Well-delineated/contained accumulations of pus
• Body’s attempt to contain a pathogen
• Surrounded by wall of granulation tissue
• Center of liquefactive necrosis + chunks of fibrin
• Can occur in literally any species in any tissue
• If chronic, can become granulomas and be
completely walled off
• Common agents:
• Staphylococcus sp., Clostridium sp., Pasturella
multocida, Corynebacterium pseudotuberculosis,
Trueperella pyogenes
• Cytology – degenerate neutrophils, proteiaceous
background, +/- agent
actinomycosis
Actinomyces sp.
• Gram positive, filamentous rod (often beaded
look); opportunist
• A. bovis – osteomyelitis (Lumpy jaw)
• SubQ firm, lumpy mass with draining tract; yellow
sulfur granules on cut section
• Infection usually secondary to wounds
• Cattle: A. bovis is common agent
• Horses: rare, but associated with fistulous
withers and poll evil
• Painful lymphadenopathy with abscesses or
granulomas
mycobacterium
Aerobic, slow-growing, acid-fast bacillus
• Intracellular pathogen within macrophages
• Many groups
• Tuberculosis group: M. bovis, M. tuberculosis
• Leprosy group: M. lepraemurium
• Opportunistic group: M. fortuitum, MAC
• Tissue damage due to persistent antigen and
cell-mediated response
• GRANULOMATOUS DERMATITIS
• Cats especially, less common dogs and cattle
• Diagnostics: ACID-FAST STAIN, PCR, biopsy
mycobacterium disease manifestations
Cutaneous tuberculosis:
• Multiple ulcers, plaques, nodules,
abscesses discharging thick exudate; pyogranulomatous inflammation with caseous necrosis
• Will see few organisms on slides
• Usually M. bovis, M. tuberculosis, rarely
M. avium or M. microti
mycobacterium disease manifestations
Atypical mycobacteriosis
OPPORTUNISTIC mycobacterial granulomas):
• Chronic/recurrent fistulous tracts, ulcers,
fasciitis, ulcerative nodules on ventral
abdomen
• Most common in cats
• Organisms also rare to find on slides
• Usually rapidly-growing species, easier to
culture!
feline leprosy syndrome
Tuberculoid leprosy ( M. lepraemurium)
• Yo u n g adult cats (<5yo)
• Rapidly progressive lesions that spread/ulcerate,
recur after surgery
• Non-painful, head neck, distal limbs
• Rare bacilli in lesions
• Lepromatous leprosy
• Older adult cats (>9yo), slowly progressive
(can be localized and spread, or generalized)
• Generally due to poor host immune response
• Nodular skin lesions
• Sheets of macrophages with numerous bacilli
• Rarely systemically ill within FLS
necrobacillosis
Caused by Fusobacterium
necrophorum
• Gram negative rods/filaments; obligate
anaerobe
• Virulence factors: LPS, leukotoxin
• Trauma to skin leads to colonization
• Cattle: (B.I.N) BOVINE INTERDIGITAL N
• Interdigital dermatitis and cellulitis with
necrosis- SEVERE
• Can extend to deeper structures
• Sheep: ovine interdigital dermatitis-NOT AS SEVERE
• Heel and toe abscesses
• Te n d t o be more mild than disease in cattle
• Diagnostics: culture
contagious foot rot
Caused by Dichelobacter nodosus
• Obligate anaerobe, contagious
• Virulence factors: exotoxin, LPS
• F. necrophorum often plays synergistic role • Wet conditions with minor wounds/abrasions
• F. necrophorum colonizes, causes damage to tissue
• Allows for D. nodosus to colonize and cause infection
• Sheep: tend to have severe lesions-SEVERE
• Necrotic damage to hoof, separation of hoof horn
• Very painful
• Cattle and goats: tend to be LESS SEVERE
• Lesions confined to interdigital skin
• Diagnostics: culture
hairy heel warts
AKA Bovine papillomatous digital dermatitis
• Thought to be caused by Treponema sp.
(spirochete organism)
• Cause of lameness in beef and dairy cattle
worldwide
• Generally solitary, circumscribed, exudative,
painful lesions on heel bulb
• Chronic lesions may look verrucose, simulating
fibropapilloma
• Confined to dermis
• Similar disease in sheep (contagious ovine
digital dermatitis (CODD) - associated with
Treponema sp.
swine erylipelas
• Erysipelothrix rhusiopathiae
Diamond skin disease
• Gram positive bacillus
• Swine are important reservoir and
• Diagnostics: culture
source of infection for other pigs
• Bacterial embolization to skin à
vasculitis, thrombosis, infarction
ZOONOTIC ALERT
• Multifocal, red/purple diamond skin lesions
• Necrosis of ears/tails with chronic lesions
• Also get vegetative valvular endocarditis
in heart
protozoal diseases- besnoitiosis
Horses/donkeys – B. bennetti
Cattle – B. besnoiti
Apicomplexan parasite
• Two-host life cycle: Definitive carnivore host
(usually CATS) and an intermediate herbivore host
• Pathogenesis is poorly understood, full life cycles not
completely worked out
• Alopecia, markedly thickened skin
• Neck, shoulders, rump
• Tissue cysts around MM, sclera – small white nodules
• Multiple, white, pinpoint masses in skin with alopecia
• Nares, conjunctiva, sclera, limbs, perineum
• Tissue cysts contain bradyzoites
• Diagnostics: biopsy
protozoal diseases- leishmaniasis
Leishmania sp.
zoonotic
• Intracellular protozoan, L. mexicana confirmed in Texas • 3 forms of disease
• Cutaneous, mucocutaneous, visceral
• Occurs in many species
• Dogs are natural host, primary domestic reservoir for human infection
• Southeastern and Midwest US
• Route of infection: female sandfly (Lutzomyia)
• Most common laboratory finding is hyperproteinemia
with hypergammaglobulinemia and hypoalbuminemia
• Alopecia, nodules, exfoliative dermatitis
• Muzzle, periorbital and aural regions
• Diagnostics: biopsy or cytology
• Pyo/granulomatous inflammation
• Organisms with macrophages
• Round to oval, rod-shaped kinetoplast perpendicular to nucleus
protozoal diseases- white spot disease
Ichthyophthirius multifilis, freshwater parasite of
fish
• Cryptocaryon irritans is saltwater equivalent (Marine
ich)
• Duration of life cycle and number of fomites
produced is temperature dependent
• Warmer water (59 – 77 ° F) improves proliferation
• 1 mm diameter white, slightly protruding nodules
(salt-like dusting)
• Surface of body, fins, gills
• Diagnostics: Fin clip, gill clip, skin scrape/cytology
• Oval, ciliated parasite
• Horseshoe-shaped macronucleus
arthropod diseases- cuterebra sp.
Obligate parasites of rodents and
rabbits
• Aberrant host: cats
• Route of infection: ingestion or direct
penetration of larvae
• Produce firm to flocculant cyst-like
subQ abscess
• Pore at top/draining tract for larvae to
breathe
• Often seen in necks of cats
athropod diseases- screwworm- Reportable
Asian and African screw worm)
Caused by Cochliomyia hominivorax and C.
macellaria in the Americas, Chrysoma bezziana
(
• Obligate parasite – needs living host for larvae to
feed • Currently eradicated in the US***
• Female lays eggs in fresh wounds à larva feed, use
proteolytic enzymes to liquefy tissue host à larvae
leave host in 5-7 days, enter soil to pupate
• If wound disturbed during feeding, larvae will burrow
or “screw” deeper into flesh – painful lesion
• Nose, eye, mouth, anus, genitalia, umbilicus
• Oozing wound with larvae tightly packed, deep in the wound (not near surface)
• Dark pigmentation of tracheal trunk through last 3-4 segments
arthropod diseases- sarcoptic mange
Sarcoptes scabiei
zoonotic
• Highly contagious mite
• Common in dogs, pigs, goats
• Completes entire life cycle on host just under
stratum corneum (within epidermis)
• Causes massive irritation and intense pruritis
• Erythematous, crusted papules with alopecia
• Self-trauma due to scratching, excoriation
arthropod diseases- sarcoptic mange
zoonotic
Pigs: S. scabiei var. suis
• Hypersensitivity form
• Most common, young pigs
• Intense pruritis in and on ears, the over rump and flanks
• Hyperkeratotic form
• Multiparous sows, thick crusts on head, pinnae, legs
• Dogs: S. scabiei var. canis
• Pinnae, elbows, hocks, ventral thorax and abdomen • Cattle: S. scabiei var. bovis
• Face, pinnae, neck • Goats: S. scabiei var. caprae
• Face, pinnae, neck, legs • Alpacas: S. scabiei var. auchinae
• Weight loss, decreased fiber production
• Ventral abdomen and chest
• Diagnostics: therapy, pinnal-pedal reflex
arthropod diseases- notoedric mange
Notoedres cati
feline scabies
• Uncommon
• Highly contagious
• Similar life cycle to Sarcoptes
• Pruritis is main clinical sign
• Head and ears (margin of pinna)
• Alopecia, thickening of skin with yellow crusts
• Diagnostics: skin scrape
• Mites easier to find than Sarcoptes
arthropod diseases- psoroptic mange
Psoroptes sp.
-reportable
• Several species, affects many animals
• Serious disease in cattle and sheep
• Complete life cycle on surface of skin
• Causes intense pruritis – likely hypersensitivity
response
• Excoriation, damaged hair, pustules that ooze, crusts
• P. ovis – sheep, cattle, goats, horses
• Ears, inguinal and perineal folds
• Can progress to rest of body
• P. cuniculi – rabbit horse, donkey, mule, sheep
• Ears • P. cervinus – ear mite, bighorn sheep
• P. communis var. auchinae - alpacas
arthropod diseases- demodectic mange
Demodex sp.
• Obligate parasites
• Live in hair follicles, part of normal flora
• Often get increased numbers with immunosuppression
• Dogs: D. canis and D. injai
• Localized – scaly and alopecia around face
• Generalized – entire body region, crusting lesions with deep folliculitis
• More common in juveniles (3-18 mos)
• Cats: D. gatoi, D. cati
• D. gatoi lives in stratum corneum, not follicles
• Alopecia, scaling, crusting on ventral abdomen, thorax, limbs
• Diagnostics: deep skin scrape
arthropod diseases- knemidokoptic mange
Knemidokoptes (or Cnemidocoptes) mutans
• Common in chickens, turkeys and
pheasants
• Entire life cycle completed on host skin
• Scaly, hyperkeratotic, crusting on
featherless areas
• Face and legs – affects large areas of skin
• Can spread to beak, claws
helminth diseases- stephanofilariasis
Stephanofilaria stilesi
• Disease of cattle
• Skin near midline
• Route of infection: hornfly
• Start out as circular patches à enlarge
with scabbing
• Chronic phase: alopecia and lichenification
• Microfilaria in skin
helminth disease- cutaneous onchocerciasis
Onchocerca cervicalis
• Causes disease in horses, cattle
• Route of infection: black fly, biting midges • Adults live in lamellar part of nuchal ligament
• Cutaneous lesions are a type I and III
hypersensitivity to the microfilaria
• Face and neck (esp. mane), ventral chest and abdomen
• Focal annular alopecia and crusting to ulceration
and lichenification
stifle
• Annular lesion in center of forehead is very classic
• Diagnostics: biopsy if needed
• Cattle: O. gutturosa
• Nuchal ligament and tendons/ligaments of shoulder, hip,
helminth disease- cutaneous habronemiasis
H. muscae; H. majus; Draschia megastoma
• Spirurid nematodes
• Disease in horses, esp. summer and early fall
• Adults found in stomach of horses
• Route of infection: L3 larvae deposited on skin
• Most common sites are the medial canthus of the
eye, the glans penis and prepuce, and any cutaneous wound
• Eyes
• Persistent conjunctivitis with ulcerated, proliferative
nodules
• Ulcerated masses of red-brown granulation tissue
• Diagnostics: biopsy if needed
