Week 8 - Dermatology Flashcards
CS of skin dz in rabbits and rodents
Pruritus
Alopecia without pruritus
Scaling
Nodules
What can cause Pruritis in rabbits and rodents?
Parasites
Environment
◦Contact – bedding
Neoplasia
What Parasites cause pruritic in rabbits and rodents?
Rabbit: Psoroptes cuniculi (otitis externa!!)
Guinea Pig: Trixacarus caviae
Rats and Hamsters: Notoedres muris
Rabbits
◦ Sarcoptes scabiei
◦Leporacarus gibbus
Rats and mice
◦ Mites: Myobia musculi, Myocoptes musculinus, Radfordia ensifera, Liponyssus bacoti
◦Louse/Lice: Polyplax spinulosa, P serrata
Guinea Pigs
◦ Mites: Chirodiscoides caviae
◦Lice: Gliricola porcelli, Gyropus ovalis
What are the Louse/Lice parasites for rats and mice?
What what organisms are they vectors for/what do the lice carry?
Polyplax serrata (mice)
Polyplax spinulosa (rats)
Organisms:
◦ Mycoplasma (Haemobartonella) muris
◦ Encephalitozoon cuniculi
◦ Eperythrozoon coccoides
How do you TREAT mites or lice?
- Selamectin (Revolution®)
◦ 15 mg tube: rabbits < 2.3 kg
◦ 45 mg tube: rabbits > 2.3 kg
◦ 2 drops (60 mg/ml): mice
◦ Repeat in 2 weeks - Isoxazolines
◦ Fluralaner [Bravecto®] in rabbits 25mg/kg - Ivermectin (0.2 – 0.4 mg/kg) - q2 weeks, 2-3x, SQ or PO (Only SQ in guinea pigs: difficulty with GI absorption)
Do NOT use fipronil (Frontline®) on rabbits (or hedgehogs) !! – will cause illness
What can cause Alopecia w/out Pruritis?
Dermatophytes
Barbering / shedding
Demodicosis (most common in hamsters)
Endocrine dz
What are some examples of Dermatophytes?
Trichophyton mentagrophytes
Microsporum canis
Microsporum gypseum
How do you DIAGNOSE dermaotphytes?
fungal culture, trichogram, Wood’s
lamp, biopsy
How do you TREAT dermatophytes?
Lime sulfur 2% topical, 1:32 dilution (0.2 liters in 3.8 liters [1/2 cup in 1 gallon] of water), 2x/week for 1 month
0.2% enilconazole (Imaveral®: Janssen) weekly for 3 weeks
(may be toxic due to ingestion)
What should you avoid with chinchillas that have otitis?
Aminoglycosides (oto-neuro-toxicity)
What causes Demodicosis in Hamsters?
Demodex aurati
◦Long, follicular
Demodex criceti
◦Short, stratum corneum
How do you TREAT Demodicosis in hamsters?
Rx ivermectin (0.3 mg/kg) SQ q 7 to 10 days
or PO q24h x ?
Fluralaner 25mg/kg q 60 days x2
What common Endocrine issue happen in small mammals that affect dermatitis?
Hyperadrenocorticism (most common in
hamsters)
Cystic ovaries (most common in guinea pigs)
Diagnosis of both probably done most easily with ultrasound
What causes scaling and crusting in small mammals?
Cheyletiella sp mites
Venereal spirochetosis (rabbit syphilis): Treponema paraluiscuniculi
Guinea pig scaling of the pinnae:
hypovitaminosis C
What does Treponema paraluiscuniculi do clinically?
Crusts, erythema, edema, vesicles, ulcers,
proliferative lesions; face and perineum
Painful, not pruritic
Metritis, abortion and neonatal death
Rabbit syphilis is NOT zoonotic
How do you DIAGNOSE Treponema paraluiscuniculi in rabbits?
Microscopic visualization of T paraluiscuniculi
from scrapes on dark field, with special silver
stains on biopsy
Serology (OK to use human lab)
How do you TREAT Treponema paraluiscuniculi?
Penicillin G (40 - 80 000 IU/kg SC, q 1 week
x 3) resolution in 1-3 weeks.
Monitor for signs of antibiotic-associated
enterotoxaemia. Treat all exposed rabbits.
Chloramphenicol 55 mg/kg q 12 h per os
for 4 weeks
Azithromycin 30 mg/kg/day per os 1-2
times daily for 15 days
What causes scaling and crusting in small mammals?
Sebaceous adenitis
Cutaneous lymphoma (hamsters, rabbits,
guinea pigs and mice – usually with severe alopecia)
Thymoma
How do you TREAT scaling and crusting in small mammals?
◦Retinoids?
◦Antibiotics if secondary infections are
present
◦Cyclosporin A (5 mg/kg) and medium chain
triglycerides q24 h
Chelitis occurs in guinea pigs. What is chelitis? How do guinea pigs get chelitis?
dry and inflamed lips
Rough forage and/or acidic fruit
Hypovitaminosis C
Pox virus
What are the causes of Nodules in small mammals?
Infectious
◦ Pododermatitis
◦ Myxomatosis
◦ Abscesses
Neoplastic
◦ Trichofolliculoma
What is Pododermatitis?
Sore hocks
w/ Rabbits & guinea pigs (rats)
Infection, wire cage bottom, obesity, females
(rabbits), neutered (rabbits), hypovitaminosis
C (guinea pigs)
Treat underlying causes as well as infection
What is Myxomatosis?
caused by Myxoma (pox) virus
Arthropod transmission
Morbidity and mortality high in pet rabbits,
approaching 100%
Incubation 8 to 21 days.
CS of Myxomatosis
Edema of the head, ears, eyelids and genitalia, milky oculonasal discharge
Myxomas: firm, non-pruritic, erythematous
nodules
Lethargy, fever
What is Otitis Externa?
- Inflammation of the external ear canal epithelium +/- pinnal dermatitis
-pinnal derma can occur without otitis externa - Incidence up to 20 % in dogs
- Less common in cats at 6 -7%
What does the pinna do?
- Latin for fin or wing
- Plate of cartilage covered w/ epithelium
- Wide variability in conformation
- Mobile, channels vibrations
- Aids in directional hearing
- Vascular for heat exchange
What does the external ear canal do?
- Vertical and horizontal canal
- Modified squamous epithelium with numerous , large sebaceous glands & also ceruminous glands
What is the tympanic membrane?
- White oval shaped membrane
- Divides external ear from middle ear
- TM rupture → otitis media
What is the SIGNALMENT for Otitis Externa?
- Any age , sex or breed
- Certain breeds : increased risk→ think
of the underlying risk factors those
breeds may have - Dogs : 5 – 8 years of age
- Allergic dermatitis most common
- Cats : 1 – 2 years of age
- Ear mites most common
CS of Otitis Externa
- Head shaking
- Scratching
- Pain
What are the clinical findings of Otitis Externa?
- Erythema
- Excoriations
- Alopecia
- Odor
- Exudate: ceruminous or purulent
- Ulcerations of otic canal +/- pinnae
What are the CAUSES of Otitis Externa?
Most cases result from a multifactorial etiology !
-PREDISPOSING FACTORS
-PRIMARY FACTORS
-PERPETUATING FACTORS
What are PREDISPOSING FACTORS for Otitis Externa?
-Alter microenvironment of ear canal
-Predispose to secondary infection
- Breed conformation
-pendulous pinna (cocker spaniels)
–Not all pendulous pinnae breeds seem
predisposed to otitis externa
-Increased # of apocrine glands
-Hairs w/in ear canal (hirsutism) - poodles
-Narrow canal conformation (shar peis) - Humid environment
-humidity in ear
-Leads to maceration of tissue
-Increased humidity due to :
-Poor ventilation : anatomy (narrowed ear canals)
-Frequent swimming / bathing
-Obstruction of ear canal
-tumors or polyps
-inflammation →epithelial swelling - Inappropriate therapy
* Mechanical trauma
-plucking hair
-“cotton” swabs
* Irritant topical products
* Improper antibiotic usage →opportunistic or resistant infections
What are PRIMARY FACTORS for Otitis Externa?
- Initiate & directly produce inflammation of canal epithelium → turn on “incubator”
- If identified & correction/management is possible may result in resolution of ear disease
- Allergic dermatitis
- Parasites
- Foreign bodies
- Cornification disorders (endocrinopathies)
- Neoplasia
- Immune mediated (pinnal dz)
How does Allergic Dermatitis - a Primary factor – cause otitis externa? How about CAFR?
- Bilateral pruritic otitis externa occurs in 50 – 80% of AD (pollen and mold) dogs
-the ONLY clinical sign in 5 – 10 % of AD dogs - Bilateral pruritic otitis externa occurs in > 80 % of CAFR dogs
-Only clinical sign in 20 – 25 %
How do Parasites - a primary factor - cause otitis externa?
- Otodectes cynotis:
- 50 % of otitis externa in cats
- 5 to 10 % of otitis externa in
dogs
-Contagious, 3 – 4 wk life cycle
-Secondary infections & ectopic infestations can occur - Demodex canis
*Otobius megnini (spinous ear tick)
How do Foreign Bodies - a primary factor - cause otitis externa?
- Acute , unilateral & painful
- Plant material ( foxtails ) , dirt ,
dried medications , lodged hairs - Diagnose with otoscopic
examination : ALWAYS LOOK!! - Can perforate tympanum
How do Cornification Disturbance - a primary factor - cause otitis externa?
- Cerumen can be pro-inflammatory
- Changes in glandular secretions
- “Primary idiopathic seborrhea”
- Secondary to other diseases…
- Any that ↑ inflammation
- Endocrinopathies
( decreased T4 , hyperadrenocorticism) - Metabolic (ex Zn responsive)
- Immune-mediated
How do Neoplasia - a primary factor - cause otitis externa?
- Typically unilateral disease
- Often hemorrhagic discharge
- More common in dogs,
more malignant in cats - Ceruminous gland ademomas
& adenocarcinomas, squamous
cell carcinomas
How do immune mediated dz - a primary factor - cause otitis externa?
-pinnae more likely to be involved than external ear
-pemphigus foliaceous
-systemic lupus erythematosis
-erythema multiforme
-ischemic dermatopathy
-juvenile cellulitis
What are PERPETUATING FACTORS for Otitis Externa?
- Do not initiate disease but
perpetuates inflammation - Treatment is important for
resolution of otitis externa - Bacterial infection
- Yeast/fungal infection
- Otitis media
- Chronic path changes
–Glandular change
–Stenosis
–Mineralization
How do Bacterial Infections – a perpetuating factor – affect otitis externa?
- Often secondary to other factors
- Common pathogens :
COCCI
-Staph. pseudintermedius
-Strep sp.
RODS
-Pseudomonas sp.
-Corynebacteria sp
-Proteus sp.
-Klebsiella - Resistance occurs!
What is Pseudomonas aeruginosa? (Otitis Externa)
-it is a rod
-Not common inhabitant of normal ear canal or middle ear
-Ubiquitous in environment, particularly aquatic environments
- Causative agent in up to 35% of otitis externa
and / or otitis media cases - Canine otitis Pseudomonas isolates
often have moderate to high levels of
antimicrobial resistance - Typically biofilm producing organism
if you see ulcers in ear, most likely Pseudomonas Aeruginosa
How do biofilms impact therapy?
- Impede delivery of antimicrobials
- Provide protected reservoir for an organism
- Enhance resistance mutation
development to concentration
dependent antimicrobials
in terms of the bacteria
1. Promote bacterial physiology & metabolism
2. Provide essential nutrients
3. Create favorable environment for survival
4. Provide architectural integrity
5. Enable genetic transfer &
intracellular communication
More about biofilms
- Divalent cations, calcium & magnesium
-Maintain structural integrity of biofilm →hold polymers together & provide
binding strength for biofilm
-Tris-EDTA – chelates Ca – so imparts biofilms - Pseudomonas biofilm is 30μm, Klebsiella is 15 μm, if a mixed
growth even thicker biofilm! - Some Staph sp. are biofilm
producers - Protein matrix created by bacteria
-Primarily Staphylococcus species and
Pseudomonas - Prevents host from responding to
pathogen and prevents medications
from treating - Appears as a gelatinous exudate that is
brown, gray or yellow
What yeast/fungal organisms play a part as a PERPETUATING FACTOR for otitis externa?
- Malassezia: common secondary infection
but also normal ear flora - Candida sp., Aspergillus are rare
- Dermatophytes & systemic fungal mycoses
→ pinnal dermatitis
CS of Otitis Media
- Head tilt
- Pain on opening mouth or chewing
- Vestibular signs
What is Otitis Media - remember it is a PERPETUATING FACTOR for otitis externa
- Maybe cause of recurrence for Otitis Externa
- Not ruled out by intact Tympanic Membrane
- 80 % of chronic otitis externa had
otitis media (+ve culture) but 70% had intact TMb - Treat with systemic antibiotics +/- myringotomy & flush middle ear
- Surgery (TECABO or ventral bulla osteotomy )
How do you DIAGNOSE Otitis Media?
clinical signs & imaging
What is Primary Secretory Otitis Media?
- PSOM , similar to “glue ear” in children
- Middle ear effusion only, rarely external
ear canal disease, may see bulging TMb - Cause may be dysfunction of
Eustachian tube but no infectious etiology
cultures negative - Cavalier King Charles Spaniel predisposed
- Head shaking, sudden deafness, head tilt
What is Chronic Pathology in terms of being a PERPETUATING FACTOR for Otitis Externa?
- Epithelial hyperplasia & glandular hyperplasia
- Fibrosis of dermis & subcutis
- Calcification of auditory canal
When is culture and susceptibility indicated for Otitis issues?
- Indicated in otitis media, cytology w/ lots of rods, poorly responsive cases
- Swab of canal and/or bulla sample
Important to remember that..
* Sensitivities indicate serum not topical
drug levels
* Some antibiotics in otic preparations
not included
When is imaging indicated for Otitis issues?
- CT , MRI or radiographic bullae series
- Indicated in cases of suspected otitis media or neoplasia
- Normal appearance of bullae does not rule out otitis media
Goals of Otitis Therapy
- Eliminate organisms
- Clean ear
- Decrease inflammation
- Identify & manage risk factors
Topical Therapy for Otitis Issues - to ELIMINATE ORGANISMS
- Many topical otic preparations triple therapies : contain topical antibiotic, glucocorticoid & an anti-fungal
- Examples :
- Tresaderm®
- Mometomax®
- Gentizol ®
- Claro ®
- Things to consider when treating with topicals
- Active ingredients
- Viscosity of product
- Tympanic membrane intact?
-if not intact, then no aminoglycosides, or goopy meds - Owner compliance
What are the first and second line of topical therapies for otitis issues?
- First line antimicrobials: neomycin, polymyxin B & gentamycin
*common in triple therapies, chronic cases
may have resistance to these antibiotics - Second line topical antibiotics:
tobramycin, amikacin & fluoroquinolones: orbifloxacin (Posatex, Merial) & enrofloxacin ( Baytril Otic, Bayer)
What does SSD cream fight against? (topical therapy for otitis)
- Silver sulfadiazine (SSD) has antibacterial properties against both Staph species & Pseudomonas
Tris-EDTA is another topical therapy
- Tris-EDTA ear flush is alkaline & aqueous
- Pretreatment 20 to 30 minutes before applying
topical antibiotics potentiates antimicrobial
effects against Pseudomonas but not Staph - Tris-EDTA pretreatment soak → antibiotics
resistant based on MICs may still have efficacy - May affect biofilms : chelates calcium
- If neuro signs present avoid topicals
- No licensed therapy for middle ear
-Both drugs & vehicles could be ototoxic - If TMb is ruptured: avoid ointments
-Triz EDTA flush or saline
-Enro 2.5 %; 1:4 ratio w/ sterile water
-SSD suspension
What can cause ototoxicity? What is it?
- Damage to the hairs in vestibulocochlear
apparatus
-Cochleotoxicity vs vestibulotoxicity or combination - Most commonly seen with systemic
aminoglycosides, cisplatin and diuretics - Topically
-Chlorhexidine, alcohols, aminoglycosides, polymixins, cerumenolytics - Fluoroquinolones, cephalosporins, TrizEDTA,
dexamethasone are typically safe
When are systemic abx indicated for otitis?
- Otitis media present
- Marked swelling & hyperplasia of otic canal epithelium (tissue
infection) - Ulceration of the otic canal (indicates deeper epithelial infection)
- Adverse topical reactions occurred or suspected
- Owners are unable to treat topically
- Base selection on culture/ susceptibility
- Injectable antibiotics impractical or risky for weeks of treatment
- Fluroquinolones most common Rx for Pseudomonas
- Marbofloxacin over enrofloxacin
- Study: 28 % of dogs responded to txt w/ only oral marbofloxacin 5 mg/kg for 3 - 6 wks
- Marbo has longer half life
What are Ear Cleaners?
- Modified cleaning / drying solutions : antimicrobial properties & mild ceruminolytic agents
- Examples: Epi-Otic®, Oti-clens®, ChlorhexiDerm®, Malacetic Otic® Douxo micellar solution®
- Any potent ceruminolytic agents : always flush with saline after use
Acidic ear cleaners:
* Epi- Otic advanced (Virbac)
* Malacetic Otic (Dechra)
Tris EDTA containing ear flush
* T8 Keto (Bayer)
* TrizUltra with Keto (Dechra)
How is ear cleaning helpful?
- Cleaning otic canal removes bacterial & inflammatory debris→
improves efficacy of topical antimicrobials - Drugs can make contact w/ ear canal
- ↓ purulent debris that inactivates some antimicrobial agents
- Daily cleaning for chronic cases , q 48 to 72 hrs in acute cases
Why consider cleaning middle ear?
- In relapsing or refractory cases need
to consider if there is otitis media - Advanced imaging: CT or MRI
- Video otoscopy & myringotomy
- Sample middle ear
- Flush middle ear
How do you DECREASE INFLAMMATION of the ear?
- Glucocorticoids systemically, topically or both
- Most effective way to diminish ear canal
inflammation & hyperplasia - Antipruritic , anti-inflammatory ,
decrease sebaceous & apocrine gland secretion - decrease glandular hyperplasia
- Often in combination topical products
- Used as sole topical agent in allergic or ceruminous otitis externa
- Provide some increased comfort
- Systemic corticosteroids 0.5 to 2 mg/kg/day for 1 to 3 weeks,
depending on any concurrent health problems - Higher potency topical corticosteroids more effective
→mometasone, betamethasone, triamcinolone
What’s your Recheck & Reassess plan for otitis externa?
- Recheck 10 to 14 days into therapy
- Acute cases should respond within 1 to 3 weeks
- Evaluations w/ cytology should occur every 10 to 14 days
- Chronic Pseudomonas otitis may take 6 to 8 weeks but w/ ongoing clinical & cytologic improvement
- Otitis media treated 6 to 8 weeks
- Treatment continue 7 to 10 days past cytologic cure for chronic cases or Pseudomonas
- ALWAYS do concurrent evaluation for predisposing, primary &
perpetuating causes / risk factors - Especially critical if reinfection occurs
What are long term management goals?
- Prevent infection and inflammation
- Manage the underlying causes/ \risk factors!
- Maintenance topical plan with ear cleaner
- Consider judicious use of topical
corticosteroid
What to consider with End Stage Ears – may need to consider surgery
- Cannot be medically managed
- Chronic discomfort and pain
- Risk of infection → meningitis
- Chronicity or recurrence is due to
-Failure to identify all causes
-Inadequate management - Leads to permanent changes to
ear canal & need for palliative
surgical resection: TECABO
Surgery is needed for AURAL MASSES
