Sarcoptes, Otodectes & Demodex · 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

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 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

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 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

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

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 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.

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 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

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