Demodicosis Flashcards
What is demodicosis?
- Inflammatory skin disease caused by the follicular mite Demodex canis
- Disease state where the mites are prsent in much larger numbers
Where is Demodex canis usually found?
- Normal habitant of skin/hair follicles generally found in small numbers in healthy animals
Is Demodex canis contagious?
- No
is Demodex canis pruritic?
- Not considered pruritic, but it can cause pruritus
Where does Demodex spend its entire life?
- On the skin of the host
Where is Demodex typically found on the skin of the host?
- Hair follicles and occasionally in the sebaceous glands
What are the life stages of Demodex (and # of legs for each)?
- Fusiform eggs
- Six-legged larvae
- Eight-legged nymphs
- Eight-legged adults
How long is the life cycle for Demodex?
- 20-35 days
How are Demodex mites transmitted?
- Spread from bitch to puppies in the first 3 days after birth
- Nursing provides direct contact for transmission
- Not transmitted or considered very difficult to transfer to dogs older than a few days old
- Mites are not found in puppies born via C-section and raised away from the mother (i.e. in utero transmission does not occur)
Why do demodex mites proliferate in some dogs (juvenile onset generalized disease)?
- Gene defect that is considered hereditary
- Thought to be autosomal recessive
What is thought to be underlying cause of generalized demodicosis in adults (and could be juveniles too)?
- Probably T-cell defect
- Somehow a depressed immune system
- Think disease or drugs!
Predisposing factors for demodicosis
- Age
- Breed
- Poor nutrition
- Estrus
- Parturition
- Ectoparasites
- Stress
Clinical lesions of demodicosis?
- Alopecia (patchy/moth-eaten to complete)
- Erythema
- Comedomes
- Papules
- Pustules
- Crusts
- Draining tracts
- Epidermal collarettes
- Nodules
What are the two variants of demodex?
- D. cornei (D. canis)
- D. injai
Is demodicosis easy to cure?
- No
- OWNER FRUSTRATION IS BIG
What do demodex mites feed off of?
- Follicular cells
- Sebum
- Epidermal debris
What can cause the pruritus with demodex?
- Secondary pyoderma
- Possible hypersensitivity
Does D. canis survive off the host?
- No
Differentials for folliculitis?
- Demodex
- Bacterial pyoderma
- Dermatophytosis
What happens when demodex causes hair follicles to rupture or get irritated?
- Folliculitis and furunculosis –> deep pyoderma
- Secondary pyoderma develops
How do you categorize demodex?
- Localized vs generalized
- If generalized, juvenile onset vs adult onset
Localized demodicosis clinical signs
- 1 to several areas
- Patchy alopecia
- Erythema
- Scales
- No to minimal pruritus
- Face, forelegs
- Usually 6 or fewer indicates localized; greater than 12 is indicative of generalized disease
Demodectic pododermatitis
- Can be present on the feet of dogs without generalized lesions
When is the juvenile onset for localized democisosis?
- Typically 3-6 months of age (<1 year usually)
Cause of juvenile onset for localized democisosis?
- Immature immune system possibly
Progression of juvenile onset for localized democisosis?
- Rarely progresses to generalized form
- Up to 90% spontaneously heal without treatment
Treatment of juvenile onset for localized democisosis?
- Again, up to 90% spontaneously heal without treatment
Is juvenile onset for localized democisosis a genetic defect?
- Not generally, if it resolves
How quickly can hair re-grow for juvenile onset for localized democisosis?
Usually within 30 days
Clinical sites that can be affected for democisosis
- Face
- Periocular area
- Commissures of the mouth
- Forelegs
- Trunk
- Rear legs
- Paws (demodectic pododermatitis)
- Bilateral ceruminous otitis
Do we treat localized form of demodicosis with miticidal drugs, and why or why not?
- NO because you need to see if it will progress if you are planning on breeding the dog
- If it does progress, that would be an indication that you shouldn’t breed this dog
- Unless they are spayed or neutered and don’t have to see if it’s going to resolve or not
Monitoring and treatment for localized demodicosis
- Wait and monitor monthly
- If it resolves, no genetic defect
- If it progresses to generalized, then there is a genetic defect and the animal should not be bred
When does juvenile generalized demodicosis present?
- Starts <18 months of age
What characterizes juvenile generalized demodicosis?
- Many localized lesions (maybe greater than 6-12)
- Involves head, trunk, leg, 2+ feet
Juvenile generalized demodicosis clinical signs
- Large aras of alopecia
- Erythema
- crusts
- Papules
- Hyperpigmentation
- Comedomes
- Pustules
- Epidermal collarettes
Clinical signs of concurrent pyoderma?
- Papules, pustules, epidermal collaretteS
- Crusts, exudate
- Pain
- Pruritus
- Lymphadenopathy
- Systemic illness
- Sepsis
Generalized demodicosis pododermatitis
- What is involved?
- How to diagnose?
- Complications?
- may have feet involvement
- Usually complicated by secondary infections
- Can occur with body lesions
- Difficult to scrape and treat (may consider hair plucks)
Where should you scrape for demodicosis?
- Scrape at the comedomes
Summary of the features of juvenile onset generalized demodicosis
- Starts as localized
- <1 year age
- GENETIC predisposition
- Hence, DO NOT BREED these animals
When does adult onset generalized demodicosis tend to occur?
- Usually >4.5 years
- Rare
What diagnostic test should you run on all old dogs with pyoderma?
- Skin scraping
What should you look for with older dogs with generalized demodicosis?
- UNDERLYING DISEASE OR DRUGS
- e.g. hypothyroidism, iatrogenic HAC, neoplasia, etc.
- > 50% have no underlying cause
What underlying diseases can contribute to generalized democisosis in adults?
- Excessive corticosteroid use
- Endocrinopathies (hyperadrenocorticism or hpothyroidism)
- Parasitism
- Neoplasia
- Poor nutrition
What diagnostics should be run for adult generalized demodicosis?
- CBC/Chem/UA
- Heartworm and fecal checks
- T4/TSH
- ACTH stim or LDDST
- Radiographs +/- U/S for neoplasia
Why should you look for underlying disease with adult generalized demodicosis?
- You’re more likely to be successful if you find and treat the underlying disease
What drugs can contribute to generalized democisosis in adults?
- Apoquel
- Prednisone
- Chemotherapeutics
What are the two primary methods to diagnose demodex?
- Skin scrapings (multiple)
- Hair plucks
- Could also do a fecal float
Equipment needed for skin scrapings?
- # 10 blade
- Mineral oil
- Slides and cover
- Microscope
Where do you perform hair plucks?
- Near eyes and feet
Sensitivity of hair plucks compared to skin scrapings?
- About 50%
How do you perform skin scrapings?
- Want blood on your blade
- Squeeze affected skin to extrude mites from hair follicles
- Minimum of 3 scrapes from lesional skin
Microscope tricks to view demodex?
- 10x objective and lower your condenser
Where do you perform skin scrapings ideally?
- Scrape over comedomes
What would histopathology findings show with generalized demodicosis?
- Folliculitis/furunculosis +/- mites
Which breeds may need a biopsy to diagnose demodicosis?
- Chinese Shar Peis, Old English sheepdogs, Scottish terriers
- May require a biopsy to diagnose demodicosis
What should you never use to treat demodicosis?
- CORTICOSTEROIDS
How to treat secondary bacterial pyoderma for localized disease (either intact or spayed animals)?
- Oral antibiotics
- Topical treatment (2-4% chlorhexidine
or Mupirocin ointment) - Benzyl peroxide (follicular flushing properties and antibacterial/anti-staph properties)
- Gel or shampoo, but shampoo is drying
Goodwinol ointment for treating localized demodicosis?
- don’t use
General treatment principles for localized demodicosis
- Optimize health (improve nutrition and deworm)
- Treat secondary pyoderma (oral antibiotics and topical treatments like benzoyl peroxide or chlorhexidine)
- Recheck dog and rescrape in 3-4 weeks
What % of dogs with localized demodicosis will progress?
10% progress to generalized form
90% improve without treatment
Should you use miticidal drugs for localized demodex?
- No, you should not
Treatment options for generalized demodicosis?
- Weekly Mitaban (Amitraz dips)
- Daily oral ivermectin
- Daily oral milbemycin (interceptor)
- Imidocloprid with moxidectin (advantage multi) which is weekly to biweekly
- Isoxazolines
Golden rule for length of treatment for generalized disease?
- TREAT ONE MONTH BEYOND 2 negative skin scrapings one month apart
Amitraz drug class
- Inhibits monoamine oxidase (MAOI) and prostaglandin synthesis
- Alpha-2 adrenergic agonist
What is labeled treatment for amitraz, and what is actually effective?
- Approved is every two weeks
- Weekly dips have increased efficacy
Amitraz/mitaban side effects
- Sedation
- Disorientation
- Bradycardia
- Ataxia
- Hypothermia
- Vomiting/diarrhea
- Pruritus
- Hyperglycemia
Antidotes for mitaban/amitraz if overdosed?
- Yohimbine
- Antisedan
What is the only licensed treatment for demodicosis?
- Amitraz or Mitaban dips
How to use Amitraz or Mitaban?
- Use every week
- Mix 1 vial in 2 gallons water
- Sponge on entire mixture of product on patient
- Let animal drip dry
- Use half dose in small dogs
In which cases should you avoid Mitaban/Amitraz?
- Sedated animals because it can impact HR
- Deep pyoderma
- Diabetics (affects BG)
- Small dogs (use half strength)
- Concurrent use of Anipryl, amitriptyline, clompramine (MAO inhibitor)
- Concurrent use of hydroxyzine
Drug class of ivermectin?
- Macrocyclic lactone
MOA of ivermectin
- Potentiates GABA gated chloride channels
WHich solution of ivermectin should you use and how should it be given?
- Bovine/equine injectable product
- Oral dose daily
- Use loading schedule to monitor for side effects
Is ivermectin for demodicosis on or off-label?
- OFF
Which breeds shouldn’t get ivermectin and why?
- Collies and shelties
- Australian shepherds
- Old English sheepdogs
- White feet, don’t treat
- MDR1 mutation can lead to accumulation and neurotoxicity
Which drugs should not be combined with ivermectin?
- Milbemycin
- Selamectin
- Mitaban
- Ketoconazole
MDR1 gene mutation
- Abnormal P-glycoprotein pumps in blood brain barrier (typically responsible for pumping out the ivermectin)
- Ivermectin accumulates in neurons, and neuro signs develop
Side effects of ivermectin
- Mydriasis
- Anorexia
- Ataxia
- Tremors
- Seizures
- Coma
- Death
What do you need to make sure about your patient before giving milbemycin oxime or ivermectin?
- Make sure they are negative for heartworm disease
Milbemycin oxime (interceptor) drug class
- Macrocyclic lactone
Milbemycin oxime - mechanism of action?
- Similar to ivermectin
Dose of milbemycin for demodicosis relative to the dose of milbemycin for heartworm?
- MUCH higher dose than for heartworm prevention
Relative safety of milbemycin oxime for herding dogs?
- Generally safer
Cost of milbemycin oxime
- Expensive
Side effects of milbemycin?
- Neurologic side effects like tremors and ataxia
- Start with 1 mg/kg and increase in 1 month if not responding (no change in mite count)
Drugs that shouldn’t be used with milbemycin?
- Mitaban
- Ivermectin
- Selamectin
What is the treatment of choice for generalized demodicosis? Is it on or off label?
- Isoxazolines
- These are off label
MOA of isoxazolines
- Inhibit GABA and glutamate gated chloride channels
Efficacy of isoxazolines
- VERY effective
Isoxazoline safety in herding dogs?
- Safe in MDR1 +
Are isoxazolines insecticidal or acaricidal?
- They are BOTH
Which dose of isoxazolines should you use?
- Intended labeled dosage
Available products of isoxazolines
- Bravecto
- Simparica
- Nexgard
- Credelio
How long does Bravecto last?
- 3 months
Which isoxazolines are safe for dogs with food allergies?
- Bravecto (hydrolyzed pork)
- Simparica (hydrolyzed soy)
- Nexgard and Credelio are not
Frequency of administration for Bravecto vs Simparica vs Nexgard vs Credelio
- Bravecto is 90 days
- All the others are every 28-30 days
Bravecto use in dogs under 6 months of age
- He wouldn’t hesitate to use, but in theory the puppy might outgrow the dosage within 3 months
What are five keys to success with treating generalized demodicosis?
- Use of isoxazolines (Bravecto and others)
- Minimum of three months of therapy (USUALLY longer)
- Avoid steroids (alters immune system and likely worsens clinical signs)
- Spay or neuter
- Treat secondary pyoderma
How long to treat generalized demodicosis?
- Minimum of three months
- Treat one month beyond 2 negative skin scrapings that are one month apart
Monitoring while treating generalized demodicosis?
- Monthly scrapes
- CLinical cure BEFORE parasitologic cure!
- Historical treatments could take months to get a negative scrape
- Isoxazolines are very effective
- Negative scrapes ON YEAR after last treatment
WHat are you evaluating durning monthly skin scrapings?
- Ratios of live to dead mites
- Immature to mature
- Look for eggs
- Evaluate overall clinical picture and responsive
Prognosis for generalized form
- Guarded for complete cure unless you can find an underlying cause of disease
- Excellent for clinical improvement and quality of life especially with isoxazolines
- May need lifelong therapy
- DO NOT breed juvenile onset generalized demodicosis
What should be avoided for generalized demodicosis for the life of the patient?
- Avoid steroids lifelong if possible
- Avoid other immune-modulatory, anti-itch treatments like Apoquel and Atopica
- Unless no other drug options exist or a medical emergency occurs
What is considered a clinical cure for generalized demodicosis?
- Considered cured if no clinical signs and mites are found 1 year after discontinuing treatment
Appearance of Demodex injai
- Long bodied mite
Where does D. injai live?
- Follicular mite that also lives in sebaceous glands
Where is D. injai found?
- Usually occurs or is found along the dorsum
Clinical signs of D. injai
- Seborrhea oleosa (greasy dermatitis) is a common clinical sign +/- alopecia
What breeds get D. injai?
- Typically terriers
Treatment of D. injai
- Treat like D. canis
Appearance of Demodex cornei?
- Short-bodied mite, basically D. canis (PCR)
Clinical signs of D. cornei
- May be pruritic, otherwise like D. canis
Treatment of D. cornei
- Treat like D. canis
What does MDR-1 code for?
- P-glycoprotein
Which drugs are concerning with MDR-1 gene?
- Ivermectin
- Loperamide
- Vincristine
- Doxorubicin
- Digoxin
How to test for ivermectin sensitivity?
- Cheek swab, $60 per test
What are the three types of feline demodicosis?
- Demodex cati
- Demodex gatoi
- Unnamed species
How common is Demodex cati?
- Rare
Is D. cati contagious or pruritic?
- Not contagious
- Not considered pruritic
What forms of demodicosis can occur with D. cati?
- Either localized or generalized
Which form (generalized/localized) is more common with D. cati?
- LOCALIZED
Where does localized demodicosis usually occur with cats?
- Nose, periocular skin, neck
- 1 to several small areas
Signs associated with localized demodicosis in cats
- Alopecia
- Erythema
- Crusting
- Variable pruritus
- Hyperpigmentation
- Ceruminous otitis
Generalized form of D. cati - clinical signs and location?
- Same clinical signs
- Head, neck, trunk, limbs
What concurrent diseases can cause generalized D. cati?
- FeLV/FIV
- Diabetes mellitus
- Neoplasia
- Hyperadrenocorticism
- Toxoplasmosis
Dfdx for D. cati in cats
- Dermatophyte
- Pyoderma
- Causes of miliary dermatitis
What is highest on the list for causes of folliculitis in cats?
- Dermatophyte!
- Pyoderma and demodicosis are both rarer
Diagnosis of generalized demodicosis in cats
- Underlying disease search (minimum data base, FeLV/FIV, fecal, radiographs)
- Skin scraping
Treatment for localized demodicosis in cats
- May be self limiting
- Isoxazolines (Bravecto)
- Lime-sulfur dips
Generalized disease treatments for demodicosis in cats
- Isoxazolines (Bravecto)
- Lime sulfur
- Amitraz
- Ivermectin
How long to do lime sulfur dips for generalized demodicosis in cats
- Weekly until 1 month past negative scrapes
Ivermectin in cats adverse effects
- Can cause toxiciity
Mitaban in cats adverse effects
- Can cause ptyalism and sedation
Prognosis for generalized D. cati treatment
- Depends on ability to treat underlying disease
What does ceruminous otitis look like in cats (i.e. clinical signs)?
- Dirty ears
- Pruritus possible
Treatment for ceruminous otitis secondary to Demodex in cats?
- Topical ear mite treatments like Tresaderm
How id Demodex gatoi different from other demodex mites?
- SUPERFICIAL MITE (lives in stratum corneum)
- PRURITIC
- CONTAGIOUS
- Short fat body
Appearance of Demodex gatoi
- Short, fat body
Is D. gatoi contagious?
- Yes
Is D. gatoi pruritic?
- Yes
Where is Demodex gatoi?
- In the stratum corneum
State distribution of D. gatoi?
Gulf states
Clinical signs with D. gatoi?
- PRURITUS***
- Alopecia
- Excoriations
- Crusting
Where on the body does D. gatoi tend to be?
- Head
- Neck
- Rear limbs
- Flanks
- Abdomen
Dfdx for D. gatoi
- Allergies
- Psychogenic alopecia
- Feline scabes (notoedric mange)
Diagnosis of D. gatoi in cats
- BROAD superficial scrapings
- Scrape other cats
- Treatment trial
- Fecal**
What objective should you use to find D. gatoi?
- 10x and LOWER CONDENSER
Treatment for D. gatoi?
- TREAT ALL CATS
- Lime sulfur dips for 6 weekly dips minimum
- Improvement sometimes seen after 3 dips but may take as long as 12-15 weeks
- Maybe Bravecto might help!