---start---- derm 11/13 fungal diseases of the skin: kevin byrne any test questions are based on the objectives on first page of handouts (two handouts) Dermatophytosis (ringworm): -relatively low incidence, but common problem (eh?) -11-22% positive cultures (exception - some catteries) -microsporum and trichophyton are most common genera in animals -require actively growing hair -almost always centered on hair follicles - unlike tinea infections in humans -endothrix infection: arthrospores within hair shaft: less common in animals -ectothrix infection: arthrospores on outside of hair shaft: way more common classes of dermatophytes: geophilic: normally inhabit soil, eg Microsporum gypseum zoophilic: adapted to animals: M. canis, most often associated with felines anthropophilic: adapted to humans: M. audouinii most common in dog/cat: -M.canis -M.gypseum -Trichophyton mentagrophytes transmission: we think it involves trauma upsetting stratum corneum. fungal spores come from infected animal or environmental source - infected hair shafts, or whatever. fomites: combs, clippers, bedding, cages, fleas, mites M.canis - comes from infected cat - spores viable up to 18 mos Trichophyton mentagrophytes - rodent burrows - free roaming dogs M. gypseum - from contaminated soil, any outdoor exposure pathogenesis: disruption of stratum corneum hyphal invasion of follicular ostia there are some virulence factors which cause some inflammation at the site - keratinases, etc host response - seems to be most important for determining severity or type of lesion we see. most dogs, if they get this, have fairly significant inflammation, erythema, swelling, etc - but some cats tolerate it much better cell mediated immunity is protective; circulating Ab is not. clinical findings - spp not that important. most common sites are head, paws, tail. if dog/cat has alopecia only on rear leg, you wouldn't put this at the top of your ddx list. should see some lesions on head, paws, tail. alopecia is the most consistent finding - without that you probably can rule out dermatophytosis. scaling is variable but common. pruritus is usually minimal. Kerion - nodular furunculosis. this is a fairly deep inflammation seen in dogs more than cats. in dogs: alopecia is seen folliculitis is most common sign - papules, pustules classic lesions uncommon two main ddx: staph folliculitis, demodecosis slide: dog lesion - skin surface shiny, thickened, alopecic. clear demarcation of edge of lesion. some little dark pink spots in paler pink background. dogs also can get it just on the dorso-rostral aspect of the muzzle - fairly common presentation - alopecia, fair amount of inflammation, crusting. slide: generalized T. mentagrophytes in dog - all over the body. not common to be this bad. slide: closeup - severely inflammed, crusted, papular type of lesion. looks like it could be autoimmune - ulcerations and stuff present. one thing that we see sometimes is that the T. mentagrophytes form can cause severe lesions like this in dogs. lesions can be symmetric and facial; may see focal folliculitis/furunculosis, or onchomycosis (not that common - people get those nail bed fungal infections, but animals do not commonly get it). if dogs do get onchomycosis, it usually takes longer to heal than a regular dermatophytosis would. slide: puppy who looks very worried - has a kerion, a fungal kerion on his right carpal region. it's a big pink plaquelike thing. dogs get a lot of inflammation - thickened skin here - looks like deep pyoderma or lick granuloma. but this is a dermatophytic kerion. clinical findings: cat: the poster cat is a persian or himalayan - for whatever reason, these cats get it a lot more. there is probably a genetic susceptibility or immunodeficiency making them more prone to it. -alopecia -damaged hair -inflammatory changes -seborrhea-like eruptions slide: small alopecic patch on dorsal aspect of paw. this is typically what a case of this can look like, esp on front foot of young cat. you have to consider ringworm as etiology of this lesi on and do diagnostics. other feline lesions: pseudomycetoma in some himalayans - a deep dermatophytic lesion in deep dermis or subq on the dorsum, makes draining lesions, looks really bad; feline acne; onychomycosis. when you see hair at toes that looks chewed, broken, or damaged, seriously consider dermatophytosis. diagnosis: woods lamp: UV light source (specific wavelength) - turn on and let warm up 5-10 minutes, expose area for 5 minutes or so. half the time, some strains of dermatophyte will fluoresce. hairs should be exposed for 5 minutes, though. negative test = nondiagnostic. positive allows you to select which hairs to pluck for fungal culture and speciation. microscopic exam: requires practice. look at hyphae and arthrospores found outside the hair shaft - little grapelike clusters of arthrospores are what you should expect to see on some hairs. you have to select the right hairs to pluck b/c not all hairs are affected. pluck affected hairs in the direction of growth. and put them on slide with mineral oil under 40x. fungal culture: most reliable method. part of the database for cats. "Derm Duet" plate has dermatophyte test media and rapid sporulation media - if you have alopecia in a cat you should do this type of test or a similar test - only way to find out what spp is present. findings must correlate with lesions, though. it is possible a dog/cat has a fungal organism hanging out on there but not causing a problem. to get source for culture, select hairs and pluck them or take a new toothbrush and brush it over the cat for two minutes then tap it over the media. that way if a cat is a carrier but has no clearly defined alopecic lesions you can tell - to find carrier who is infecting others in household. T. mentagrophytes - again, nasty lesions in dogs slide: M. gypsium hyphae DTM fungal culture - media turns red when dermatophyte is present due to change in pH when dermatophyte consumes part of media. other contaminants do not usually cause that color change to occur until much much later. the change in color occurs early while colony grows with dermatophytes, though. some other things like sporothrix and a couple of other pathogens can cause the color change though - so you have to take part of the colony, put it on a slide with some stain, and look at it - the three main dermatophytes have fairly identifiable characteristics m .canis has 6 or more macroconidia with thick wall and big knobby end. m. gypseum has thinner wall, broader shape, fewer macroconidia biopsy: not as reliable as culture. finding organism = definitive proof. most useful for nodular forms. therapy: make client aware this takes a while to treat. for pseudomycetoma (uncommon deep lesions) - surgical excision and lengthy treatment for any contact animals in house, and the environment: topical therapy and disinfectants. some dermatophytes are resistant, though. hard to kill. typically b/c of nature of organism we treat after apparent clinical cure - in cats, need 2 negative toothbrush cultures after it resolves, then d/c meds. in dogs, go 4 weeks of therapy regardless of what lesion is doing, then negative toothbrush culture. sylvatic ringworm - trichophytan types - tend to be severe and aggressive - almost always require systemic therapy. cats also almost always get systemic therapy too b/c it is the only thing that really works. topical therapy: d/c environmental contagion if possible dispose of old bedding gently clip affected lesions clipping the entire cat of affected cats can make some cats worse. the only good reason for that is if it has severe generalized dz. three main topical therapies which might work: lime sulfur miconazole chlorhexidine efficacies of these may depend on strain of dermatophyte systemic therapy for nonresponding dogs and all cats, trichophyton infections, or severe cases - combine with topical therapy to reduce shedding into environment and exposure of other pets and people. griseofulvin - binds microtubles, also affects chitin synthesis. give with fatty meals. side effects - some cats have idiosyncratic bone marrow problems from it like neutropenia, anemia, etc. always make sure cat FIV negative first b/c positive cats more suscptible. certain purebreds more susceptible to side effects too. monitor CBC, liver enzymes. it's teratogenic too. itraconazole: (sporanox) works, fairly well tolerated. not approved for use in dogs and cats. inhibits production of ergosterol. well tolerated in cats, better than ketoconazole or nizoral, but only comes in 100 mg capsules so you have to find someone to break them open and reformulate it- cat will usually take readily in tuna flavored suspension. 10 mg/kg once daily is the dose. not for use in pregnant animals. ketoconazole (nizoral) not tolerated as well, some resistance to it exists too. other drugs: terbinafine - new, expensive, used in asia, fewer side effects in humans, unproven in dogs and cats. extremely expensive, doses aren't worked out well. fairly well tolerated we think, though. not economically feasible at this time.a tube is like 90 bucks. reasons for therapeutic failure: if there is one thing it is hard to do it is clear a dermatophytosis without relapse. especially in multicat houses -inappropriate therapy (drug/dose/frequency/duration) -failure to use topicals (environmental contamination and constant reinfection) -underlying disease -immunosuppressive drugs Malasseziasis - yeast infections M. pachydermatitis - a yeast that is a lipophilic, amycelial saprophyte and a real cause of pruritis and stuff in dogs and rarely cats. normal and abnormal canine skin contains malassezia. highest numbers in areas of increased sebum. T cell mediated immunity is protective. clinical findings: lesions: erythema, lichenification, waxy yellow exudate, alopecia. no pathognomonic lesions. sites: interdigital, ventral neck, axillae, perianal, lips, ears, skin folds. also around nail beds. typical presentation - cocker spaniels get this alot - cocker with lichenified alopecic area on ventral neck, with some yellow seborrheic appearance to it, yeasty odor. this dog was so severe he had a lesion on the dorsum which is rare. dx: find underlying cause ddx: pyoderma, parasitic, seborrheic dermatitis, other diagnostic trial with ketaconazole: determine yeast contribution to dermatitis dog usually will markedly improve within a few days/weeks remember dog could have more than one problem at one time! any breed but terriers, bassetts, poodles overrepresented underlying causes in 50% pruritus common nd often severe offensive odor present dx: skin cytology: scraping, taping, or swabbing in normal skin should see 3 or fewer organisms per cu.cm. management: systemic therapy usually required if lesions are multifocal ketoconazole at 5-10 mg/kg sid/bid. can try topicals. usually have to go to oral systemic. dog side effects: anorexia, hepatotoxicity, dose related histopath isn't that useful for dx yeasts...yeasts usually wash away during specimen preparation. ---break--- nodular fungal diseases: -avoid glucocorticoids -nodules may be single or multiple -may ulcerate and drain or remain intact -hematogenous spread in systemic mycoses slide: hock of dog with nodular sporothrichosis (?) dx: excision of nodule with fungal culture and histologic exam for draining lesions, cytology may be diagnostic. cryptococcus - a nodular form is possible. c. neoformans: slide of cat with cryptococcosus, swelling of nasal planum, oozing, purulent material present. the nice thing is this is easy to dx via cytology. impression smears are diagnostic. pyogranulomatous exudate with fungal orgnaisms dispersed throughout. crypto is uncommon in cats and rare in dogs. it's the most common deep mycosis in cats. if FIV/FeLV positive, hard to resolve. most feline cases have nasal mass. Therapeutics in dermatology: slide: waterfall when dealing with skin, shampoos and liquids are fairly helpful. First line antibiotics: for first or 2nd time, non-chronic infections pertaining specifically to the skin -Lincomycin - 22 mg/kg BID: expensive, resistance problems -Erythromycin - 10-15 mg/kg tid: vomiting, resistance -Clindamycin: 11-12 mg/kg TID: expensive, deep lesions, resistance second line abx TMP/sulfa - side effects, don't use in dobies clavamox oxacillin ormetoprim/sulfa these are less likely to have resistance problems, esp clavamox or oxacillin (although oxacillin resistance has been seen.) methicillin resistant staph aureus in humans is a problem but we don't have such a huge problem in vet med yet w/ staph intermedius big guns: cephalexin - 22 mg/kg bid-tid - good drug for large dogs, fairly economical enrofloxacin - 5-10 mg/kg sid - sometimes fails when organism is sensitive perhaps due to inadequate tissue levels, can't use in growing animals, avoid in epileptics other fluoroquinolones have come out recently - their spectrum is similar to that of Baytril. systemic glucocorticoid therapy: used most often for pruritus - the bad thing is to use them during infectious processes. allergy - steroids often don't really help and cause more side effects than benefit and can cause secondary pyodermas we like to use steroids for immune mediated disorders, and other noninfectious inflammatory diseases like granulomatous disease. severe pruritis. also used for cancer chemotherapy. glucocorticoid doses: pred: .04-.22 mg/kg/day maintenance 1.1 mg/kg/day antiinflammatory 2.2- 4.4 mg/kg/day for immunosuppression dexamethasone rarely used except for some dogs are less pu/pd on it than pred. with steroids: attain desired effect, decrease to lowest dose which works, then taper off if possible. sometimes the side effects of the steroids are the main complaint - you may fix the pemphigus but create a dog who isn't housebroken and owner is still upset. if side effects are as bad as original disease, you really want to try nonsteroidal therapies. side effects: iatrogenic cushings, immunosuppression, gi ulceration, steroid hepatopathy, immunosuppression, secondary infection, demodex. systemic antihistamines: metabolized by liver anticholinergic side effects unknown teratogenicity other effects - antipruritic. don't work as well in dogs/cats as people, especially the nonsedating ones really don't work well in dogs/cats block mast cell degranulation (hydroxyzine) efficacy unpredictable in dogs/cats; weekly therapeutic trials - usually we try one for a week, see if it works, if not, try another one. lather, rinse, repeat until you find one that works. cats more likely to get side effects, in terms of behavior changes, hyperexcitablitiy (dogs get more sedate), so warn owners. none of these are approved for veterinary uses. used with other therapies first generation antihistamines: chlorpheniramine maleate (Chlortrimeton) diphenhydramine (Benadryl) hydroxyzine doxepin (really a tricyclic antidepressant w/antihistamine activity) clemastine (Tavist) Synthetic Retinoids - vitamin A analogues very expensive probably 100 bucks/mo to tx 30 kg dog fewer side effects in dogs than people potent teratogens: Keep Out Of Reach of Women effects are numerous on epithelia monitoring required side effects we do see are elevated liver enzymes, dry eye examples: Isotretinoin (Accutane): more effective for adnexal dzs - schnauzer comedones, sebaceous adenitis, feline acne, keratoacanthoma, ichthyosis. dose 1-3 mg/kg/day side effects: conjunctivitis, vomiting/diarrhea, erythema, others. (in people - depression/suicide) lab abnormalities - hypertriglyceridemia, increased liver enzymes (d/c drug temporarily), hypercholesterolemia longterm use: hyperostosis, periosteal calcification, longbone demineralizatoin.s Etretinate (tegison) - to be replaced by acitretin b/c lasts 2 yrs in body fat! more effective for epithelial dzs - idiopathic seborrehea, SCC, solar dermatitis dose 1 mg/kg/day, side effects as with accutane rule of thumb for topical therapy: if it is wet, dry it, if it is dry, wet it. considerations in choosing a topical therapy: see handout for details purpose: desired result sole therapy (rarely), or adjunct (usually) type of delivery system (shampoo, cream, lotion, spray) active ingredients needed patient/client considerations one of the biggest compliance problems we have is clients not wanting to use shampoos and other topical therapies. so always consider ease of use. when you talk to the client, weigh their response - if you ask them if they will shampoo the dog and they say "well, sort of, I guess." that means shampoo is probably a poor choice. formulations: selection considerations: size of the area that needs tx residual activity - low with most shampoos presence of hair - interferes with creams nature of lesion - if wet, dry it; if dry, wet it! new thing - spray on shampoos - HyLyt product antipruritic topicals: to decrease pruritic load - colloidal oatmeal (Epi-Soothe), Burow's solution to substitute another sensation - menthol, camphor, thymol (cooling sensation) to anesthetize peripheral nerves - pramoxime (in Relief products), benzocaine. one cool product: pramoxine and oatmeal leave on conditioner - better than shampoo b/c you do not wash it off. this is called "ResiPROX" and is part of the "Resi" line by Allerderm which has increased residual activity biochemical antipruritic agents: hydrocortisone fluocinolone diphenhydramine - not useful in pruritic dog/cats CortiCalm - hydrocortisone lotion - very expensive. DVM Pharmaceuticals. Antimicrobials - the other important group of topicals. these are going to be a big help to you. Chlorhexidine - perhaps the best if you had to pick one. good against s. intermedius, not pseudomonas. good against yeast. usually nonirritating, rarely sensitizing. not inactivated by organic material. 1% needed for yeasts. benzoyl peroxide - good antibacterial, good keratolytic, good degreaser. very drying, not for use on dry skin or will increase pruritus.very irritating. good follicle flusher. also remember - these are bleaching agents. if you put cream on pet and pet jumps on leather couch owner will be pissed at you if the couch gets bleached out. silver sulfadiazine - 1% effective for pseudomonas; no interference with reepithelialization ethyl lactate: hydrolized by bacterial lipases into lactic acid and ethanol. expensive, and no benefit over chlorhexidine. topical antibiotics: neomycin - OTC at human pharmacy. variable efficacy for gram negs. good contact sensitizer, though - allergy may develop; interferes with reepithelialization polymixin B and bacitracin - Mupirocin: most used in dogs for focal lesions when we need anti-staph activity. relatively effective for s.intermedius, some resistance. penetrates skin well, not systemically absorbed, 10 minutes contact time. polyethylene glycol base - in cats can be toxic if you cover enough surface area with this stuff. antimycotics: miconazole good for malasseziasis, some effect against dermatophytes clotrimazole: good for yeast, +/- may be effective against dermatophytes ketoconazole - same as miconazole and expensive nystatin - in panalog - kills yeast thiabendazole - some efficacy against malassezia misc. topicals: tretinoin: Retin-A: tx of acne, local keratinization disorders; irritating, potent teratogen so wear gloves. DMSO: very hygroscopic, quickly penetrates skin, variety of properties, use medical forms only, avoid contaminants. currently being used in situations in dogs where there is calcinosis cutis (secondary to cushings or whatever) - it works well in the gel form for this. if you tx dog too fast, dog can get hypercalcemia and renal failure! so be judicious.no published literature on this yet, give it 6 mos to 1 yr and there will be. Lime sulfur: more effective for dermatophytosis. good to have on desert island with you :). fairly good antiparasitic for sarcops, cheyletiella, etc. smells awful and stains jewelry. Trantal (pentoxifylline) - a drug looking for a disease - inhibits phosphodiesterase and TNF-a. used in vascular dz, irritant/allergic contact rxn. can tx cold agglutinin dzs, lymphocytic infiltration dzs. dose isn't really worked out well yet, see handout Tetracycline and niacinamide: first used in humans to tx bullous skin dzs anti-inflammatory, most useful for discoid lupus, mostly GI side effects. dogs 250-500 mg of each drug TID worth trying this as cheap steroid sparing drug for inflammatory dz. ---end---