Exam 1 Dermatology Flashcards
Skin Scrapings function
This diagnostic test has 1 function: to evaluate for parasites. Diagnose ectoparasite discorders.
Keys to Diagnostic skin scrapings
- clip the hair or scrape a hairless area - squeeze the skin (gently) prior to scraping - scrape a sufficient area - scrape to the proper depth!
Why do you squeeze the skin while doing a skin scraping
this helps diagnose Demodex, or parasites that live in the hair follicles.
what direction do you scrape when you are doing a skin scraping
With a scalpal scrape in the direction of the hair. 1-2 cm area in diameter is generally sufficient and you do not need to scrape tot he capillary hemorrhage.
You identify this on Histology. What is it
Keratinocytic plug
If you do not see any of these on a slide, then you know you did not squeeze the skin hard enough
Evaluation for Yeast (Malassezia spp.)
- Demonstrate the organism
- impression smear
- cotton-tipped applicator swabs
- skin scraping
- Culture
- Histopathology
What technique do you need when making a slide for yeast
press the glass slide against the skin. To get the yeast to stick, you have to have a firm background
Should you use a fixative when staining a slide with tape on the slide
no, it will make the slide hazy
Trichogram - How to
Grasp the hairs firmly with forceps
Gentle, but firm, removal from follicle
Place on a slide in mineral oil
Add a cover slip
Examine microscopically
What is evidence of pruritus when performing a trichogram
The distal ends of the hair will appear to be damaged. This supports the claim of pruritus.
What type of hairs are in a “resting” state
Telogen hairs
when these are removed, they pull the whole root with it.
What are the growing hairs?
Antigen hairs- these tend to break off when they are removed.
Diagnosis of Dermatophytosis
Wood’s lamp examination
KOH preparation (trichogram)
Fungal culture
Histopathology of a skin biopsy
what are the folicular mites of the Genus Demodex
Demodex canis
Demodex injai
Demodex cati
What is an example of surface mites of the genus Demodex
Demodex gatoi (found in cats)
What is the pathogenesis of Demodicosis
- A mite-specific immunoincompetency allows for proliferation of mites
- Mites secrete some factor that suppresses T lymphocyte function resulting in general immunoinsufficiency
- Secondary infections are common
- Causing additional immunosuppression
Describe Localized Demodicosis
- Lesions restricted to one (or two) body areas
- Signs include alopecia, erythema, mild scaling
- 90% spontaneously resolve
- Treatment is not necessary, but if it is done, it will make lesions look worse initially
- Topical medications such as lotions or creams- hairs will shift from antigen and telogen, this causes the hairs to come out easier. Using a lotion will dislodge the hairs and make the area of alopecia large. The condition is not worsening but clients may believe so
If you have an area of alopecia around the patients eyes, and you suspect demodecosis, what diagnostic tool would you use?
You could do a skin scraping or a trichogram. The skin scraping is high risk because of it’s close association with the eyes.
A trichogram is lower risk and equally as effective.
Describe Generalized Demodicosis
- Multiple leasions: alopecia, scaling, crusts, pustules, erythema, draining tracts
- folliculitis and furunculosis
- Bacterial:generally Staph pseudintermedius
- Systemic signs: anorexia,lethargy depression
Furunculosis
Furunculosis is a deep infection of the hair follicle leading to abscess formation with accumulation of pus and necrotic tissue. Furuncles appear on the hair-bearing parts of the skin.
Treatment of Localized Demodicosis
- Topical medications
- Benzoyl peroxide gel
- Rotenone
- Amitraz
- consider products designed for flean control - Isoxazolines etc.
- Client education is important.
Treatment of Generalized Demodicosis
- Treat underlying pyoderma
- Systemic antibiotics for 3-4 weeks
- Topical antimicrobial/anti-seborrheic shampoos
- Hydrotherapy (bath)
- Cleansing
- Facilitates treatment of pyoderma
Why would you treat the secondary infection first?
Reduces pruritus - Pruritus is generally associated with the scondary infection. Reducing this will increase the comfort for the patient.
Removes the “yuk” factor for the clients
Can you treat Demodicosis with Avermectins or Milbemycins?
yes, but this is not the treatment of choice anymore
What is the significance of Amitraz?
- Approved for use in dogs
- This requires a total body clip in medium-long-coated dogs
- contact time is crutial for 10-15 minutes
- Do not rinse off
- Weekly treatment for 8-12 weeks.
Prior to this drug’s discovery, patients would die from Demodicosis infections
what is the downfall of using Ivermectin Therapy for demodicosis treatment
Treatment lasts for months.
What gene mutation do you have to worry about in Collies?
ABCB-1 gene mutation.
When using avermectins, what other drugs do you need to avoid using concurrently? Why is this?
Ketoconazole
Spinosad
Erythromycin
Cyclosporine
These drugs act as P-gp inhibitors and may lead to toxicosis
Explain Milbemycin Oxime. How long should you use this medication when treating Demodicosis? What animals do you need to avoid using it in
Product name: Interceptor
-A macrocytic lactone compound
Recommended to treat BID for 90-180 days
(Treat for 30 days past resolution)
Contraindicated in avermectin-sensitive dogs
Moxidectin
Macrocytic Lactone
combination product with imidocloprid (acts as an insect neurotoxin) Advantage multi
has similar effects as ivermectin in ivermectin-sensitive Collies
Weekly application is required to control demodecosis (extra-label use)
How do Isoxazoline parasiticides work
Give examples of these products
Block insect GABA and glutamine -gated chlorine channels
Bravecto, Nexgard, Simparica, Credello
Advantages of Isoxazoline parasiticides
appear to be highly efficacious
Label doses are effective
Minimal adverse effects
No contraindications in dogs with ABCB-1 Mutation
Disadvantages of isoxazoline parasiticides
Not labeled for treating demodicosis
What are some important points regarding Demodicosis
- client education is important
- Hereditary predisposition: neuter dogs with generalized demodicosis
- Good prognosis in most cases - fair to guarded prognosis in some animals
- Glucocorticoids are contraindicated
- Search for underlying disease in older patients.
Demodex injai clinical features
- Adult dogs
- seen most often over dorsal lumbar region
- pruritus, alopecia, greasy skin/hair coat.
Diagnosis of Demodex injai
Diagnosis: trichogram, skin scrapings
Mites are flound in low numbers
Recommend multiple samples; multiple techniques
Careful examination of slides
Treatment of choice for Demodex injai
- isoxazolines
- All appear to be effective
- no clinical trials reported
- Ivermectin
- Amitraz rinses weekly
- Advantage multi (weekly applications)
Demodex cati description
follicular
rare
often found in the ear
Demodex gatoi description
surface dwelling mite
common geographically
- patient presents with alopecia and pruritus (variable intensity)
- lesions may appear symmetrically
- Diagnose by skin scrapings, fecal flotation and histopathology
Why is it difficult to find Demodex gatoi under microscopic examination
Cats lick the lites off making them difficult to find. If you take a skin scraping try to collect samples from an area that has not been licked on
Fecal flotation is indicated if you suspect this.
Treatment of choice for Demodicosis in cats (D.gatoi)
- Fluralaner-Bravecto for cats
- treat every 8 weeks for 2-3 dosees
- He leans toward monthly treatments
- treat every 8 weeks for 2-3 dosees
- Lime sulfur (treatment-of-choice)
- treat weekly for 4-8 treatments
- At least 2 applications past negative skin scrapings
Sarcoptic Mange in dogs
- highly contagious
- reservoir is often wild canids
- Zoonotic potential
- Causes severe pruritus from irritiation and hypersensitivity reactions
- wakes them up, prefer to scratch over eating. So uncomfortable that they will stop whatever they are doing to itch.
what layer of the skin do you find female eggs for Sarcoptic scabiei var. canis?
Stratum corneum- the females burrow into this layer and hatch eggs. Males live their lives on the surface. If you use drugs that only get on the surface, and don’t penetrate the surface, you will only kill some mites.
how long is the lifecycle for Sarcoptic scabiei var canis
Life cycle is 3 weeks
- adult, egg, larva, nymph
- females burrow to lay eggs.
Clinical features of Sarcoptic mange
- Intense pruritus
- Generalized lymphadenomegaly- not cancer sized but prominent
- Crusts, scaling, erythema, alopecia, excoriations
- classical distribution of lesions (P-E-E-L)
- periocular area
- ear margins
- elbows
- lateral extremities
Diagnosis of Sarcoptic Mange
- Presumptive based on history and clinical features
- identify mite
- Skin scrapings: multiple scrapigns may be required to find mites
- fecal flotation
- Serologic testing
when trying to diagnose Sarcoptic Mange, where on the lesion would you wnat to collect skin scrapings
You want to be sure you collect the crusts from the lesion. Use your scalpal to chop up the crusts so the coverslip will fit. don’t worry about damaging the mites.
When performing a skin scraping of a crusty lesion, you identify this mite. what is your diagnosis/identification
Sarcoptes scabiei var canis
when performing a skin scraping of a crusty lesion you identify these structures on microscopic examination. What do you identify these as?
Sarcoptic scabiei var canis eggs with fecal mater (highlighted)
Treatment protocol for Sarcoptic mange in canine patients
- Treat all suspect animals
- Treat all animals in thehousehold
- Clean and disinfect the environment
- control pruritus with glucocorticoids (may offer some relief. These dogs are very uncomfortable)
- Suggests humans with lesions consult their physicians.
Topical Therapy for Sarcoptic Mange
total body clip is recommended in medium and long coated dogs
Keratolytic baths are helpful initially- remove crust and scale (sulfur shampoo is recommended)
Other shampoos used to control secondary infections
- Benzoyl peroxide
- Ketoconazole or miconazole
Is topical acaricides such as lime sulfur a reasonable topical option for a patient that has Sarcoptic Mange?
yes this is a good option. it must be applied weekly for 6-8 weeks following total body clip
what product is Selamectin
Revolution
How is selamectin used in the treatment of sarcoptic mange
One dose is 93% efffective
Using 2 doses repeated at 2-3 week intervals is 100% effective.
-This is labeled for sarcoptic mange in dogs with no adverse effects
How would you use moxidectin when treating for Sarcoptic Mange
Advantage Multi
Labeled to treat once monthly; however, clearance is slow 2-3 months
Recommend q14 days for 3 treatments (extra-label)
Ivermectin use against Sarcoptic mange in canine patients
ABCB1 mutation animals is still contraindicated.
This is highly effective via oral or SC administration.
Dosage q7d for 3-4 doses
Adverse effects:
- CNS signs: ataxia
- Vomiting
Fipronil for treatment against Sarcoptic Mange
Frontline Spray Treatment
total body spray once weekly for 2 weeks.
- 100% effective in 36 cases
Adverse effects: topical irritation
Milbemycin Oxime as a treatment for Sarcoptic Mange
Interceptor
Many protocols are described, but this is a Macrocytic lactone, so there are concerns against use in herding breed animals.
Amitraz use as a treatment against Sarcoptic Mange
Mitaban
Effective but not approved for this use in dogs in the USA
Isoxazoline parasiticide use against Sarcoptic Mange cases
studies support efficacy for all products
Mites cleared in 30-60 days
Lesions persist: consider other factors.
Overall treatment plan for a patient with sarcoptic mange
- consider use of glucocorticoids if not done previously
- Treat all affected dogs and cats with lime sulfur rinse for immediate relief
- Treat all household animals with selamectin, ivermectin, or moxidectin etc.
- clean and disinfect environment
- Recommend consultation with a physician if humans have lesions.
Why would you have treatment failure for a sarcoptic mange case
Incorrect diagnosis
Compound problems
Incorrect dosage of insectacide
Insufficient treatments
Incomplete application of insecticides
Re-infestation in farm dogs.
What products are good preventative options for a dog with potential Sarcoptic Mange exposure?
Advantage multi
Isoxazolines
Revolution
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