Sarcoptes, Otodectes & Demodex Dr Lee Strapp BVetMed MRCVS - - PowerPoint PPT Presentation

Sarcoptes, Otodectes & Demodex

Dr Lee Strapp BVetMed MRCVS

Veterinary Scientific Liaison Bayer Animal Health

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

Sarcoptes

Introduction

• Sarcoptes scabiei var. canis
• Burrowing mite, found in the lower stratum corneum
• f 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

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

Clinical Signs

• Pruritus (often intense)
• Alopecia
• Erythema
• Papules
• Crust
• Excoriations
• Secondary pyoderma
• Pinna-pedal reflex often present
• Predisposed sites; ears, muzzle & elbows

Clinical Lesions

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

Typical Distribution of Lesions

• Head

– Periocular – Pinnal margin

• Ventral

abdomen

• Chest
• Legs

– esp. elbows

Pinna-Pedal Reflex

• Rub pinnal

margins

– frantic scratching

• Common

– BUT not always seen

Sarcoptic Mange in a Puppy

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

Diagnosis 1

• Presumptive diagnosis is often made on the basis
• f 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

Diagnosis 2

• Confirmatory diagnosis by skin scrapings
• As many as possible; edges of lesions, not from
• pen 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

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

Sarcoptes egg

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

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

Sarcoptic Mange – Response To Treatment

Before treatment

22 days after initial treatment

Sarcoptic Mange – Response To Treatment

50 days after initial treatment

Sarcoptic Mange – Response To Treatment

Efficacy of Treatments

• “Both products were highly effective against

sarcoptic mange with a parasitological cure rate

• n 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.

Sarcoptic Mange in a Human

• Severe clinical cases in humans are frequently

associated with host adapted S. scabiei var. hominis

Otodectes

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

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

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

Discharge from Otodectes

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

Otodectes on Microscopy

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

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

Demodex

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

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)

Demodicosis Predisposing Factors

• As well as immunosuppression from disease or

medications, other predisposing factors:

– Short hair – Poor nutrition – Stress – Oestrus – Endoparasites – Pyoderma

Life Cycle

• Exclusively on host
• Fusiform eggs

(lemon shaped)

• 6 legged larvae (2

stages)

• 8 legged nymphs

(2 stages)

• Adults
• 18-24 days

Clinical Signs 1

• Erythema
• Papules
• Comedones
• Alopecia
• Scaling
• Hyperpigmentation
• Pruritus not usually a feature unless

secondary factors

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

Human Demodicosis Canine Demodicosis

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

Demodex canis on microscopy

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

Categorisation of Disease

• LOCALISED
• GENERALISED

1) Juvenile Onset 2) Adult Onset

• (PODODEMODICOSIS)

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

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

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

Pododemodicosis

• Pedal lesions
• Extremely

uncomfortable

• Difficult to treat

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

Treatment - Generalised

• Advocate

– Can be used monthly; better results weekly

• Use weekly for 6-8 weeks, assess response based
• n 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

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

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

day -1 day 112

Advocate Examples

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)

Summary

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

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

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