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 Sarcoptic Mange – Response To Treatment

22 days after initial treatment Sarcoptic Mange – Response To Treatment

50 days after initial 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

Advocate Examples

day -1

day 112 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