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Parasitic Dermatoses of the Dog and Cat

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Candace A. Sousa, DVM, Dipl. ABVP, Dipl. ACVD VetScope 2021-09-01

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Parasitic Dermatoses of
the Dog and Cat
Candace A. Sousa, DVM
Diplomate (Emeritus) American Board of Veterinary Practitioners,
Canine and Feline Practice
Diplomate (Emeritus) American College of Veterinary Dermatology

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Diagnosis Begins with Relief

Stop the Itch
Rule out Parasites
Treat Skin Infection
Conduct Diet Trial
Confirm Atopic Dermatitis

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Canine Pruritus
Infectious Diseases
1. Sarcoptes scabiei
2. Malassezia colonization
3. Staphylococcal pyoderma
Demodex Hypothyroidism
Conformation (obesity)
4. Other (dermatophytosis, Cheyletiella, lice, etc)

Allergic Diseases
1. Flea allergy dermatitis
2. Atopic dermatitis
Food Non IgE (atopiclike)
Environmental allergens
3. Other allergic diseases (Drug eruptions, contact
allergy, etc)

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Flea Allergy Dermatitis
Ctenocephalides felis
Flea bite hypersensitivity is the most common allergic disease of the dog and cat
Pruritus concentrated on the caudal half of the body
Cats also have crusted papules around the neck

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Distribution of flea allergy dermatitis, canine
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Distribution of flea allergy dermatitis, feline
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Flea allergy dermatitis with secondary Staphylococcal folliculitis
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Flea allergy dermatitis
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Flea allergy dermatitis
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Chronic chewing can cause wear of the teeth, especially the incisors
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Distribution of flea allergy dermatitis in the cat, lateral
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Distribution of flea allergy dermatitis in the cat, dorsal
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Miliary dermatitis secondary to flea allergy
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Miliary dermatitis secondary to flea allergy, close up
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Severe miliary dermatitis, post clipping
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Seizures due to fleas in a cat
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Diagnosis of Flea Allergy Dermatitis
History and physical examination
Presence of fleas or flea dirt
Intradermal test
1:1000 w/v dilution of Greer antigen
Positive and negative control
Doesnt work well in cats

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Fleas on the pet
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Dead fleas on the exam table after alcohol based flea spray
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Flea feces on the pet
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Flea feces in water
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Positive intradermal test to flea antigen, dog
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Intradermal test to flea antigen, cat
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Treatment of Flea Allergy Dermatitis
Collars
Insect growth regulator (IGR)
Juvenile hormone analogue
Pyriproxyfen (Nylar) (i.e. Knockout)
Methoprene
Adulticidal
Methylcarbamate (i.e. BreakawayTM)
Flumethrin (Seresto)

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Treatment of Flea Allergy Dermatitis
Topical Adulticides
Fipronil (i.e. Frontline, Frontline Plus)
Imidacloprid (i.e. Advantage, Advantix)
Permethrin (i.e. Duraspot)
Caution dogs only
Spinetotram (Cheristin)
Cats only
Dinotefuran (i.e. Vectra)
Selamectin (Revolution, Revolution Plus)
Also works to control other dermatologic parasites (ear mites, lice, Cheyletiella, nasal mites)

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Treatment of Flea Allergy Dermatitis
Oral flea control
Oral systemic IDIs
Lufenuron (i.e. Program)
Oral adulticides
Nitenpyram (Capstar)
Spinosad (i.e. Comfortis, Trifexis)
Afoxolaner (NexGard)
Fluralaner (Bravecto)
Sarolaner (Simparica, Simparica Trio, Revolution Plus)
Lotilaner (Credelio)

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Treatment of Flea Allergy Dermatitis
Control of pruritus
Apoquel (oclacitinib) PRN
Treatment of secondary infections
Improvement usually seen within 7 to 14 days after elimination of the fleas

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Lice
Both biting and sucking lice in dogs and biting lice in cats
Species specific
Diagnosis Identification of the lice or eggs

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Biting / Chewing Lice (cat) Mallophaga
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Felicola subrostratus

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Biting / Chewing Lice (dog) Mallophaga
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Trichodectes canis

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Sucking Lice (dog) Anoplura
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Linognathus setosus

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Louse nit cemented to the hair shaft
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Louse nits (eggs) attached to hairs
Anemia due to sucking louse infestation

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Lice on a puppy

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Louse
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Treatment Lice
No licensed, approved product for treatment
Revolution (selamectin) q month 2
Pyrethrins weekly 3
Ivermectin q 2 weeks 3
Fipronil (chewing lice)
Isoxazolines (?)
Treat for 1 month
Treat all incontact animals
Environmental cleaning
2 Shanks, DJ, Gautier, TL, McTier, TL, et al. Efficacy of selamectin against biting lice on dogs and cats. Vet Rec 152:23437, 2003 3 Scott, DW, Miller, Jr, WH, Griffin, CE. Muller & Kirks Small Animal Dermatology, 6th Ed. 2001

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Sarcoptes scabiei
Primarily a problem in canids
Burrow into the cornified layer of the epidermis and lay eggs
Severe pruritus develops as an IgEmediated reaction to intestinal proteins found in the fecal material

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17 to 21 days
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Sarcoptes scabiei Clinical Signs
Pruritus with lesions most severe on the edges of the pinnae, elbows, hocks, and ventrum
Alopecia, erythematous papules, excoriations, crusts
Positive pinnalpedal reflex

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Scabies
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Scabies, periocular
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Scabies, edge of the pinnae
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Scabies
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Scabies, close up
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Scabies, end stage
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S. scabiei in a cat
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Scabies, human arm
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Diagnosis Sarcoptes scabiei
Identification of mites, eggs, or fecal pellets on a skin scraping; can be difficult
Positive ELISA test (2 to 4 weeks after infestation)
Response to therapy

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Sarcoptes scabiei (note egg in abdomen)
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S scabiei fecal pellets, eggs

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S. scabiei, histopathology

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Treatment Sarcoptes scabiei
Selamectin (Revolution) q month
AdvantageMulti q 24 weeks
Lime sulfur rinses q week
Organophosphate rinses q 2 weeks
Amitraz q 2 weeks
Ivermectin 0.3 mg/kg q 2 weeks
Caution on HW positive dogs or Pglycoprotein deficient animals
Fipronil spray q 2 weeks
Milbemycin 2 mg/kg q week (or EOD)

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Treatment Sarcoptes scabiei
Now we have the isoxazolines
Afoxolaner (NexGard)
Fluralaner (Bravecto)
Sarolaner (Simparica , Simparica Trio)
Lotilaner (Credelio)
Treat all incontact canids
Continue treatment up to 1 month following resolution of clinical signs

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Notoedres cati
Primarily a problem in felids
Burrow into the cornified layer of the epidermis and lay eggs
Severe pruritus develops as an IgEmediated reaction to intestinal proteins found in the fecal material

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Notoedres cati Clinical Signs
Pruritus with lesions most severe on the edges of the pinnae, face, periocular areas, and neck
In severe cases, feet and perineum involved
Papules, alopecia, excoriations, crusts
Positive pinnalpedal reflex

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Notoedres , head
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Notoedres , pinnae
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Notoedres , kitten
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Notoedres, forelegs
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Notoedres cati
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Notoedres cati, eggs
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Treatment Notoedres cati
No licensed, approved treatment
Revolution, Revolution Plus(selamectin) q month 6
Lime sulfur rinses weekly 7
Amitraz q 2 weeks 7
Ivermectin q 2 weeks 7
Continue treatment up to 1 month
Treat all incontact felids
6 Beale, KM, Fujioka, C. Effectiveness of selamectin in the treatment of Notoedres cati infection in cats. Proc AAVD/ACVD, 2001 7 Scott, DW, Miller, Jr, WH, Griffin, CE. Muller & Kirks Small Animal Dermatology, 6th Ed. 2001

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Dogs Demodex spp.
Demodex canis
Follicular
shortbodied Demodex
Surface stratum corneum
Demodex injai
largebodied Demodex

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20 to 35 days
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Demodex canis, adult
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Demodex canis, larvae
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Demodex canis, egg
100X

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Short tailed demodex, canine
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Short tailed demodex larvae, canine
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Demodex injai
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Why arent dogs with demodicosis usually pruritic?
Normally found in the hair follicles and sebaceous glands
Demodex mites dont have a terminal anus Protein byproducts are converted into guanine crystals that are deposited under the exoskeleton
After they die or are killed they will break open releasing intestinal contents which can cause pruritus
...except Demodex

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Puppies with short tailed demodex
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Puppies with short tailed demodex
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Demodicosis
Localized
Fewer than 5 spots; does not involve an entire body region or more than 1 paw
Spontaneous resolution within 3 months
No treatment is necessary
Reports of < 10% progressing to generalized demodicosis

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IMAGE

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Demodicosis
Generalized
Five or more localized lesions
Involvement of an entire body region
Involvement of 2 or more paws
A cause of ceruminous otitis externa
Often complicated by deep pyoderma
Can be pruritic, mainly from bacterial overgrowth

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Generalized Demodicosis
Juvenileonset vs. adultonset
18 months
Dogs with juvenileonset generalized demodicosis should never be bred
In adultonset, evaluate the dog for potential underlying causes

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Generalized demodicosis, juvenileonset
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Generalized demodicosis, juvenileonset
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Comedones and pustules secondary to follicular plugging by D. canis
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Generalized demodicosis Red Mange
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Generalized demodicosis

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Seborrhea secondary to generalized demodicosis
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Generalized demodicosis, post clipping
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Generalized demodicosis, post clipping
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Pododemodicosis secondary to corticosteroids (?)
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Pododemodicosis secondary to corticosteroids, close up
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Generalized demodicosis, 7 year old M American cocker spaniel
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Generalized demodicosis, 7 year old M American cocker spaniel
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Ear canal
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Generalized demodicosis, 7 year old M American cocker spaniel, paw
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Pododermatitis is demodicosis until proven otherwise
Pitbull
Chihuahua
Akita
Bulldog

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Demodicosis Diagnosis
Multiple deep skin scrapings
Biopsy
Chronic granulomatous lesions
Chinese Shar Pei
Pododemodicosis
Hair plucks

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Biopsy

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Biopsy

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Localized Demodicosis Treatment
Will selfcure
Doesnt become generalized
Benzoyl peroxide gel (Pyoben)
Rotenone (Goodwinol)
Dont use amitraz (Mitaban) to spot treat
Not labeled for this condition
Mite resistance?
Failure to differentiate localized from generalized disease at a later time
Systemic antibiotics if needed
Pruritus usually secondary to pyoderma

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Generalized Demodicosis Treatment
30 to 50% of juvenileonset cases will spontaneously resolve
Systemic antibiotics if needed
Pruritus usually secondary to pyoderma
Avoid corticosteroids as they make the pyoderma worse

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Now We Have the Isoxazolines
Fluraner (Bravecto Merck)
Afoxolaner (NexGard Merial)
Sarolaner (Simparica, Simparica Trio® Zoetis)
Lotilaner (Credelio Elanco)
Fourie JJ, Liebenberg JE, Horak IG, Taenzler J, Heckeroth AR, Frénais R. Efficacy of orally administered fluralaner (BravectoTM) or topically applied imidacloprid/moxidectin (Advocate®) against
generalized demodicosis in dogs. Parasit Vect 2015; 8:187.
Beugnet F, Halos L, Larsen D, de Vos C. Efficacy of oral afoxolaner for the treatment of canine generalised demodicosis. Parasite 2016; 23;14.
Six RH, Becskei C, Mazaleskia MM, Fouriec JJ, Mahabira SP, Myersa MR, Slootmans N. Efficacy of sarolaner, a novel oral isoxazoline, against two common mite infestations in dogs: Demodex spp.
and Otodectes cynotis.. Vet Parasit 2016; 222: 6266.

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Demodex spp. Cats
Demodex cati
Rare
Usually secondary to a serious underlying condition
Demodex gatoi
More common
A cause of overgrooming (fur mowing)
Mistaken for psychogenic alopecia
Contagious
Some cats may be asymptomatic carriers
Mites can be difficult to find with either superficial scrapings or acetate tape
preparations
Can occasionally be found with fecal flotation

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Demodex gatoi

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Feline demodicosis, D. gatoi

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Feline demodicosis, D. gatoi

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Feline demodicosis, D. gatoi

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Feline Demodicosis, D. gatoi Treatment
Lime sulfur rinses q weekly for 4 6 weeks
Case reports on the efficacy of Bravecto and Revolution Plus
Treat all incontact cats

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Cheyletiella spp.
Symptoms range from absent to intense pruritus
Scaly dermatitis
Mites are easy to kill since they are surface feeders

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3 to 5 weeks
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Cheyletiellosis

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Cheyletiellosis, 3 cats

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Cheyletiellosis, close up

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Cheyletiellosis, puppy

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Cheyletiellosis

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IMAGE

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IMAGE

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Cheyletiellosis, human arm

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Cheyletiella sp.

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Cheyletiella spp. Treatment
Isoxazolines will probably work
Selamectin (Revolution, Revolution Plus)12,13
Not approved but shown effective in 2 clinical trials
Pyrethrincontaining products
Lime sulfur rinses
Organophosphate rinses
Ivermectin
Treat all cats and dogs +/ the environment

12 Chailleux, N, Paradis, M. Efficacy of selamectin in the treatment of naturally acquired cheyletiellosis in cats. Proc AAVD/ACVD, 2001
13 Mueller, RS, Bettenay, SV. The efficacy of selamectin in the treatment of canine cheyletiellosis. Vet Rec 151:773, 2002

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Otodectes cynotis
The most common ear mite of dogs and cats
Can also be found on the skin
Pruritus is caused by the production of IgE antibodies
All incontact animals should be treated

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3 to 4 weeks
IMAGE

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Ear mites, cat

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Otodectes cynotis

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Otodectes cynotis, adult, egg

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Otodectes cynotis Treatment
Clean the canals first if possible
Revolution®, Revolution Plus (selamectin) 14
Pyrethrins
Rotenone
Thiabendazole
Ivermectin

14 Shanks, DJ, McTier, TL, Rowan, TG, et al. The efficacy of selamectin in the treatment of naturally acquired aural infestations of Otodectes cynotis on dogs and cats. Vet Parasit 91:28390, 2000

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What we didnt cover
Ticks
Hookworm dermatitis
Pelodera
Mosquito bite hypersensitivity
Cuterebra
Dracunculiasis
Nasal mites

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QUESTIONS??

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