9 – Mites Flashcards
Arachnida 3 main groups
- Burrowing mites: short legs
- Surface mites longer legs
- Ticks
General life cycle of mites
- Adults (8 legs) on host
- Eggs on host
o Resistant to some treatment - Larvae (6 legs) on host
- Nymphs (8 legs) on host
- *10-21 days
Pathogenesis of mite acariasis
- Range from no effects to severe dermatitis (mange)
- Hypersensitivity
- Excoriation and secondary bacterial infection
Burrowing mites
- Dorso-ventrally flattened
- Short legs
Burrowing mites: examples
- Sarcoptes sp. (canine scabies mite)
- Notoedres sp. (feline scabies mite)
- Demodex sp. (demodectic mange mite)
Sarcoptes scabei: dogs
- Highly contagious with other dogs, wild canids
- Transiently zoonotic (self resolving)
- *high scratching
- *EVERYWHERE
Sarcoptes adults
- Short legs
- Long unjointed pedicles
- Survive in cool, humid environments for up to 3 weeks
- Many ‘spikes’ to burrow in the skin
Sarcoptic mange
- Hairless areas (ears, elbows, ventrum, tarsal)
- INTENSE pruritus (hypersensitivity)
- Erythema
- Crusts
- Hair loss, excoriation
- Hyperkeratosis
- +/- mites (depends where you take a skin scrape from)
o Ex. ear: wont find them
o Go along edges! - *TREAT IT REGARDLESS!
Human skin lesions associated with zoonotic Sarcoptes
- Some red marks
Notoedres sp.: cats
- Highly contagious among cats
- Transient zoonoses
Notoedres cati: adults
- Smaller than Sarcoptes
- Do NOT survive in environment
- *would look at the species it came from!
Notoedres sp. : feline scabies
- Ears
- Face and eyelids (+/- feet and perineum)
- Intense pruritus
- Dry, crusty skin
- Hair loss, excoriation
- Hyperkeratosis
- Lymphadenopathy
Demodex spp.
- Not zoonotic, not contagious
o Except D. gatoi - No environmental survival
- ‘vertical’ transmission: close contact with dam
Demodex spp. adults
- Live in hair follicles and sebaceous glands (squeeze!)
- Eight legs on throax
- Clinical significance: number of adults AND larvae&nymph:adult ratio
- *’long cigar’
Demodectic mange in dogs: clinical presentations
- Most asymptomatic (normal fauna)
- Localized demodicosis
- Generalized demodicosis
- Pododemodecosis
Localized demodicosis
- Young (3-18months)
- Mouth, ears, forelegs, rarely ear canals
- Focal alopecia
- Squamous
- Silver scaling
- Not pruritic
- Self-resolving: most self-cure within 1-2 months
Generalized demodicosis
- Any age, prognosis better for young
- Starts face and limbs
- *when 5 or more lesions
- Pustular form
- Folliculitis
- Hyperkeratosis
- Painful, not pruritic unless secondary
- Even sepsis, death
Pododemodecosis
- Do NOT scratch as much
- Manifestation or sequalae of generalized form
- Least common form of disease
- *usually all 4 paws
Demodecosis: young animals (3-18 months), localized and generalized form
- Localized: excellent prognosis (self-recovery)
- Generalized: depends on history and family, good prognosis with treatment
Demodecosis: older animals (>1.5 years), generalized form
- Often underlying immune deficiency, concurrent disease, reproductive stress
- Poor prognosis, difficult to treat
Demodecosis treatment
- Isoxazolines, moxidectin
- Antibiotics, nutritional support, grooming
- Do NOT use parents or pups for breeding
Feline demodecosis (RARE): D. cati
- Eyelids, head, neck
- Localized often resolves spontaneously
- Generalized: check for underlying disease (FLV, FIV)
Feline demodecosis (RARE): D. gatoi
- Pruritic, contagious
- Often no underlying disease
- *show and pedigree cats
Surface mites: types
- Cheyletiella spp: rabbit fur mite (walking dandruff)
- Otodectes sp: ear mite
- Eutrombicula spp.: harvest mite
Cheyletiella spp.
- Contagious within and among species
- Zoonotic
C. yasguri: species
- Dogs
C. blakei: species
- Cats
C. parasitivorax: species
- Rabbits
- common
Cheyletiella adult
*contagious among species
- PALPAL CLAWS
- Can survive in cool environment for more than 10 days
Cheyletiella clinical signs
- Often subclinical
- Starts as dorsal scaling
- +/- MILD pruritis, hair loss
- Rarely: hypersensitivity, miliary dermatitis, dorsal hypotrichosis
- Ex. Harvey and McKeever skin diseases
Human Cheyletiella infestation
- Self limiting
- Red spots where ‘animals’ are being held
Otodectes cynotis (CATS, dogs): ear mites
- 50% of otitis cases in cats
- <10% of otitis cases in dogs
- *highly contagious, usually not zoonotic (transient)
Otodectes adults
- Longer legs
- Can survive in cool, humid environments for months
- Short pedicel or stalk
- Caruncle or sucker=close
Otodectes mites: clinical signs
- Not always restricted to ears: can be SYSTEMIC
- Pruritus, shaking, behavioural disturbances (hypersensitivity)
- Worse in young and immunocompromised
Eutrombicula spp. (NA, harvest mite or chigger)
- Free living mites
- Only LARVAE PARASITIC (wide range of hosts)
- *zoonotic (from environment, NOT host-host)
- Seen mostly in fall
- RARE
Eutrombicula spp. larva
- *ONLY 6 legs!
- Plumose setae (‘feather’): bright red=see with naked eye
Eutrombicula clinical signs
- Larvae around eyes
- Head, eyes, ears
- Feet
- Ventrum
- Can be mild-severe pruritus associated with stylostome (feeding tube)
- Infestation transient
Diagnosis of burrowing mites
- Multiple, deep skin scrapings +/- KOH digest
- Biopsy?
Diagnosis of surface mites
- Tape
- Comb
- Vacuum
- Hand lens
- Fecal (cats!)
Diagnosis: ear/nose
- Otoscopy/rhinoscopy and swab (mineral oil)
What do you treat with?
- Macrocyclic lactones (oral, topical, paraenteral)
o Ivermectin, selamectin - Isoxazolines (oral)
Mange management: Cheyletiella
- Treat all animals in contact
- Zoonotic
- Can survive in environment (>10days)
Mange management: Otodectes
- Treat all in contact with dogs and cats
- Zoonotic (rare, transient)
- Can survive in environment (months)
Mange management: Eutrombicula
- Don’t need to treat others, unless same source exposure
- Zoonotic (from environment)
- Can survive in environment (most of life cycle outdoors)
Mange management: Sarcoptes
- Treat all in contact
- Zoonotic (transient)
- Can survive in environment (weeks)
Mange management: Notedres
- Treat all in contact with cats
- Zoonotic (transient)
- Can NOT survive in environment
Mange management: Demodex
- Only treated affected
- Not zoonotic
- Do NOT survive in environment
