sarcoptes, otodectes & demodex · mite of cats and dogs in the world •over 50% of otitis...
TRANSCRIPT
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Sarcoptes, Otodectes & Demodex
Dr Lee Strapp BVetMed MRCVS
Veterinary Scientific Liaison
Bayer Animal Health
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Overview
• Sarcoptes, Otodectes, Demodex
• Three different mites, all commonly encountered
• Obligate parasites - entire life cycle on host
• Skin disease termed mange:
– sarcoptic, otodectic or demodectic
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Sarcoptes
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Introduction
• Sarcoptes scabiei var. canis
• Burrowing mite, found in the lower stratum corneum of the epidermis
• Relatively common in dogs, foxes, other canidae
• Very rare in cats (host specific Notoedres cati)
• Zoonotic; can infest humans
• Often referred to as Sarcoptic mange / fox mange
• Known as scabies in human medicine
• Highly contagious – whole household
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Life Cycle
• Exclusively on host
• 2 to 3 weeks
• Mating on surface
• Egg laying in
burrows
• Transmission;
close contact
1 Egg 4 Tritonymph
2 Larva 5 Adult
3 Protonymph
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Clinical Signs
• Pruritus (often intense)
• Alopecia
• Erythema
• Papules
• Crust
• Excoriations
• Secondary pyoderma
• Pinna-pedal reflex often present
• Predisposed sites; ears, muzzle & elbows
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Clinical Lesions
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Clinical Signs (Chronic)
• Ongoing pruritus
• Extensive self trauma
• Scale
• Hyperpigmentation
• Lichenification
• Untreated can spread to whole body
• Systemic signs may be seen – Lethargy / malaise / inappetance
• Histopathology – Chronic inflamm. / hyperkeratosis / parakeratosis
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Typical Distribution of Lesions
• Head
– Periocular
– Pinnal margin
• Ventral abdomen
• Chest
• Legs
– esp. elbows
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Pinna-Pedal Reflex
• Rub pinnal
margins
– frantic scratching
• Common
– BUT not always seen
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Sarcoptic Mange in a Puppy
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Identification
• Sarcoptes scabiei mites are rotund, ventrally flattened and dorsally convex, with short legs
• The dorsum is covered in spines and there is a terminal anus
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Diagnosis 1
• Presumptive diagnosis is often made on the basis of history & clinical signs – Dermatitis affecting dog & in contact dogs +/- humans
– Nature and distribution of cutaneous lesions
– Positive pinna-pedal reflex highly suggestive
– Pruritus minimally responsive to steroids
• Similarity with a number of differential diagnoses, aim for a laboratory diagnosis
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Diagnosis 2
• Confirmatory diagnosis by skin scrapings
• As many as possible; edges of lesions, not from open wounds or chronically inflamed excoriations
• Preferred locations are those covered in visible raised yellowish crusts and papules
• Sites of predeliction; edges of ears, elbows and limbs especially around tarsal joint
• Mites, mite eggs, mite faeces
• Low sensitivity ~25% confirmed by scrapes
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Sarcoptes scabiei microscopy
• 10% potassium hydroxide (KOH) solution can be added to the collected material and then gently warmed to help clear the debris to reveal the mites
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Sarcoptes egg
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Diagnosis 3
• Serological testing – commercial ELISA tests (demonstration of anti Sarcoptes scabiei var canis IgG) sensitivity up to 90%
– False negatives, as seroconversion can take ~5 weeks
– Positive results DO NOT indicate active infestation but do indicate prior exposure
– Time taken to be seronegative - several months +
– Do not use to declare failure of treatment
• Histology – not usually conclusive, unless find mites themselves by chance
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Treatment
• Systemic acaricides
– 10% imidacloprid / 2.5% moxidectin spot-on 0.1ml/kg, twice 4 weeks apart
– Selamectin spot-on 6-12mg/kg, twice 30 days apart
• Topical acaricides
– Amitraz, weekly sponge on
• Systemic isoxazolines
– Sarolaner, twice at monthly intervals
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Sarcoptic Mange – Response To Treatment
Before treatment
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22 days after initial treatment
Sarcoptic Mange – Response To Treatment
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50 days after initial treatment
Sarcoptic Mange – Response To Treatment
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Efficacy of Treatments
• “Both products were highly effective against sarcoptic mange with a parasitological cure rate on Day 56 of 100%.”
• “…dramatic reduction in the clinical signs associated with sarcoptic mange from the first application.”
• Must treat in-contact animals!
Australian Veterinary Journal – Vol. 84, February 2006’ Fourie et al.
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Sarcoptic Mange in a Human
• Severe clinical cases in humans are frequently associated with host adapted S. scabiei var. hominis
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Otodectes
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Introduction
• Otodectes cynotis is the most common mange mite of cats and dogs in the world
• Over 50% of otitis externa cases in dogs and 85% in cats involve infestations with Otodectes
• The mites do not burrow; they live on the surface of the skin of the outer ear canal
• They feed, causing irritation and the canal becomes full of cerumen, blood & mite faeces
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Life Cycle & Transmission
• Entire life cycle on host; complete in ~3 weeks • Eggs hatch into larval ear mites in ~4 days • One larval & two nymphal stages then adult
• Transmission usually by direct contact: – especially from infested dams to their young
– also from dogs to cats and vice versa
• Transmission through cerumen expelled from ear during scratching & head shaking is rare
• Large proportion of cats & dogs harbour a small population of mites
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Clinical Signs
• Brown waxy discharge in external ear canal
• Ear mites may be seen
• Pinnae & ear canal erythema
• Mild to severe pruritus – physical presence of mites & mite saliva is an irritant
• +/- Ulceration
• Signs of secondary trauma – Excoriation & wet eczema
• Head shaking +/- Aural haematoma – Tympanic membrane may be perforated
» Torticollis / Circling / incoordination
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Discharge from Otodectes
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Diagnosis
• Dark brown to black crumbly crusts or waxy deposits + pruritus highly suggestive
• Visualisation of mites on direct otoscopic examination (BUT avoid light!)
• To confirm diagnosis, ceruminous debris removed from ear canal and examined microscopically for mites +/- eggs
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Otodectes on Microscopy
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Treatment
• Ear cleaning products remove ceruminous debris
• Ear drops applied directly into the ear canal usually twice daily for several days
– repeat course 7-10 days later is required
• Topical spot-ons incorporating systemic active ingredients, such as moxidectin or selamectin
• In some clinical cases, anti-inflammatory medications are used to ease secondary signs
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Advocate Treatment
• ‘Do not apply directly to the ear canal’
• ‘Examination 30 days after treatment is recommended as some animals may require a second treatment’
• Efficacy 98-99%
• Treat in-contacts
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Demodex
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Introduction
• Demodex canis is a common mite of dogs
• Low numbers - normal part of cutaneous fauna
• Other Demodex species are very rare: – longer body mite Demodex injai (greasy skin, Terriers)
– shorter body mite Demodex sp. (cornei)
• Demodex cati & Demodex gatoi of cats are extremely rare (often associated with FeLV/FIV) – NB: D. gatoi is unlike all the other Demodex species,
being transmissable and causing a sarcoptes like intense pruritus
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Transmission
• Demodicosis is not considered a contagious disease; no horizontal transmission (except D. gatoi)
• Mites are only transmitted from the bitch to nursing puppies – Stillborn pups from infected dams free of mites – Puppies delivered by Caesarean do not have mites if not
allowed contact with the dam
• Tendency to develop clinical disease, demodicosis, influenced by: – genetic T-cell defect (hereditary) – Immunosuppression due to debilitating disease – Immunosuppressive medications (e.g. steroids)
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Demodicosis Predisposing Factors
• As well as immunosuppression from disease or medications, other predisposing factors:
– Short hair
– Poor nutrition
– Stress
– Oestrus
– Endoparasites
– Pyoderma
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Life Cycle
• Exclusively on host • Fusiform eggs (lemon shaped) • 6 legged larvae (2 stages) • 8 legged nymphs (2 stages) • Adults • 18-24 days
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Clinical Signs 1
• Erythema
• Papules
• Comedones
• Alopecia
• Scaling
• Hyperpigmentation
• Pruritus not usually a feature unless secondary factors
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Clinical Signs 2
• Secondary pustule formation
• Severe disease; follicles rupture = furunculosis with deep lesions & crusting
• Lesions anywhere on body; face & feet most commonly affected
• Generalised cases may also show depression, lethargy, lymphadenopathy
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Human Demodicosis
Canine Demodicosis
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Diagnosis
• Deep skin scrapings +/- trichograms
• A small area of skin (1-2 cm2) scraped in direction of hair growth until capillary bleeding – A blade covered with liquid
paraffin is used
• Follicular papules or pustules are good sites for scraping
• Squeezing skin helps push mites out of follicles
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Demodex canis on microscopy
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Deomodex in Skin Scrapings
• Demodex mites are a normal part of cutaneous fauna so occasional mites can be found normally
– extremely rare to see more than one Demodex canis mite in a dog not affected by demodicosis
• Note the site of scraping & relative numbers of adults, larvae, nymphs & eggs per field
• Assessment of response to therapy relies on comparison of such numbers
• Scrapings ideally repeated at the same sites monthly
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Categorisation of Disease
• LOCALISED
• GENERALISED
1) Juvenile Onset
2) Adult Onset
• (PODODEMODICOSIS)
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Localised Demodicosis
• 3 to 6 months
• Up to 4-6 focal lesions
• Mild signs, especially periocular & top of head
• Lesions often wax & wane
• Majority; spontaneous resolution in 6 to 8 weeks
• Good prognosis
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Generalised Demodicosis 1
1) JUVENILE ONSET • 3 to 18 months
• 12 or more lesions or large patches of coalesced lesions and/or paw involvement
• More severe dermatological presentation
• Systemic signs
• Good prognosis
• Up to 50% of cases in dogs <1 year old resolve spontaneously
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Generalised Demodicosis 2
2) ADULT ONSET
• 4 years+ with no prior history of Demodicosis
• Usually follows some form of immunosuppression
– Neoplasia
– Hyperadrenocorticism (Cushings)
– Hypothyroidism
– Immunosuppressive treatments e.g. glucocorticoids, chemotherapy
– Atopy
• Often poor prognosis
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Pododemodicosis
• Pedal lesions
• Extremely uncomfortable
• Difficult to treat
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Treatment - Localised
• Often resolves spontaneously
• Miticidal therapy may not be required; however, may expedite improvement in clinical signs eg. Advocate monthly
• Treatment may be necessary for concurrent bacterial infections
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Treatment - Generalised
• Advocate
– Can be used monthly; better results weekly
• Use weekly for 6-8 weeks, assess response based on mite counts, if improving continue weekly until resolution (often takes many months)
– Skin scrapes / hair plucks at least every month & continue treatment until no live mites found at two scrapes a month apart
• Amitraz wash sometimes used
• full dog clip & prolonged contact time
• + Additional treatments for underlying disease
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Treatment of Demodex
• Expectation! – it’s not 100% like Sarcoptes
– resolution of clinical cases often takes many months
– understandably vets often give up much sooner
• Treatment aim is to control mite numbers back to a commensal level rather than ‘cure’
• Mild to moderate first opinion cases
– Licensed products good first line option
• Severe generalised cases often need referral & dermatologists use oral off label ivermectin
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Additional Treatments
• Multi-factorial disease - advisable to also treat any underlying disease appropriately (in particular in adult onset disease)
• Treat accompanying skin signs, e.g. pyoderma
• Treat underlying systemic disease
• Response to any therapy may be incomplete unless predisposing factors are addressed.
• DO NOT USE STEROIDS
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day -1
day 112
Advocate Examples
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Control
• Eliminate demodex carriers from breeding line; castrate affected males, spay affected females
(NB also a chance of relapse of disease during season so
beneficial to individual too)
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Summary
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Sarcoptes scabiei var. canis
• Relatively common in dogs
• Extremely rare in cats
• Intense pruritus especially ears and elbows
• Highly contagious & zoonotic
• Do not rely on blood test
• Responds well to treatment; 2 Advocate applications at 4 week interval
• Treat all in-contacts
• Prognosis good
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Otodectes cynotis
• Very common in dogs and cats
• Pruritus & dark brown / black wax
• Contagious – close contact
• Responds well to treatment - 2 Advocate applications at 4 week interval
• Treat in-contacts
• Prognosis good
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Demodex canis
• Low numbers; normal fauna in many dogs
• Disease often indicates underlying disease (esp. in older dogs)
• Alopecia +/- pruritus
• Non contagious (horizontally)
• Spontaneous resolution in some localised cases
• Advocate best results weekly
• Generalised cases often difficult to treat over many months and prognosis may be poor
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