Derm 3: parasitic & infectious dermatoses Flashcards
what is the most common allergy type in north America? what is the allergen?
flea allergy dermatitis (FAD)
hypersensitivity to salivary antigens (high flea burden isn’t always an issue)
likely less relevant in Alberta bc it’s so fucking dry
what are the C/S of flea allergy dermatitis (FAD)?
dogs: dorsolumbar, inguinal, sometimes neck region (classic and consistent) [imagine dog wearing a pair of shorts
cats: can present with any of the 4 feline hypersensitivity patterns, most often affected on dorm and demonstrate military dermatitis
no ears or paws involved!!
PRURITIS!!!
increase in FAD in CAD
how do you definitively diagnose flea allergy diagnosis?
- demonstration of fleas on animal (adults or flea dirt)
- compatible C/S
- response to appropriate treatment
This patient (Gorp) comes into your clinic with pruritis and this distribution of lesions (see picture). what is your diagnosis?
flea allergy dermatitis
how do you differentiate between flea dirt and regular dirt/debris?
moisten flea dirt on gauze –> turns reddish bc it’s digested blood
dirt won’t do this lol
how do you treat flea allergy dermatitis?
- itch relief –> lokivetmab, oclacitinib, cyclosporine
- flea preventative for all in contact animals –> isoxazolines (all of the -laners, including fluralaner AKA Bravecto, sarolaner AKA Revolution Plus, and afocolaner AKA Nexgard) [reminder that products containing permethrin can be deadly to cats]
- environmental treatment (recommended when flea burden is high, esp when humans start to get bit) –> sprays > foggers, daily cleaning, professional services (fleas don’t like sunlight so focus on shaded areas)
what is the species that causes scabies/sarcoptic mange in dogs?
Sarcoptes scabei var canis (canine scabies mite)
tell me about the behaviour of Sarcoptes scabei in relation to scabies
epidermal mite that burrows in superficial epidermis
C/S typically happen after 1 week of infestation
mite can only live off host 48h-6 days
disease can be caused in people, but milder
What species is this? What disease does it cause?
Sarcoptes scabei var canis
causes scabies / sarcoptic mange
how are fleas transmitted?
direct contact, touching fomites/animals with fleas, fleas can also jump from host to host!
how is sarcoptic mange transmitted?
direct contact with infected host (other dogs, wildlife –> fox, coyote)
prefer skin with little hair (explains site predilections)
what are the C/S of scabies? what sites are affected?
- intense PRURITIS (most pruritic condition in vet med) that does NOT respond fully to anti-itch meds
- scaling, crusting, erythema, alopecia, lichenification develops after some time of no treatment
sites: pineal tips/margins, elbows, hock, ventrum (with time, lesions can become widespread)
This dog, named Bark Twain, presents for intense pruritis. based on this sign and the body sites affected, what is the most likely diagnosis?
Sarcoptic mange/scabies
how do you find fleas on a pet’s body?
flea comb, can sometimes be seen moving around in fur, looking for flea dirt
how do you find scabies mites on a pet’s body?
superficial skin scrapes, esp of crusty ear tips or mid-ventrum
look for mites, eggs, or fecal pellets
is scabies considered zoonotic? why or why not?
yes it is, because it has been known to infect cats, foxes, and humans
human disease shows up within 24h of contact and most likely regress spontaneously. human pruritis is worse when warm (in bed under blankets, after hot shower)
you do a superficial skin scrape on a dog for practice and find 1 Sarcoptes scabei mite. Is this animal considered diseased with scabies?
yes! finding even 1 mite, egg, or fecal pellet is considered diagnostic
how do you diagnose scabies?
- finding the mites/eggs/fecal pellets on a dog’s body (1 of these things is considered diagnostic)
- pinnal-pedal reflex (can also be positive with CAD)
- ELISA serology (not commonly done)
how do you treat sarcoptic mange?
isoxazolines (Bravecto, Nexgard, etc) = best
sulfur dips weekly, Selamectin or Moxidectin topicals, Revolution, Ivermectin
what are these?
Sarcoptes scabei var canis eggs
what species of mites cause Demodicosis in dogs?
Demodex canis, and to a lesser extent D. injai and D. cornei
how does a dog get demodicosis? like what is transmission like, what causes disease, etc
demodex mites are considered normal residents of dog skin and are thought to be present in small #sin most dogs.
numbers are so low that they are nearly impossible to get on skin scrapings.
transmitted from puppies from bitches within first 3 days of life.
entire life cycle spent on host.
not considered contagious bc most dogs have mites (but they can go from dog to dog)
if host-demodex balance tips in parasite’s favour, then clinical demodicosis occurs.w
where do Demodex species live on the dog?
in hair follicles and to a lesser extent sebaceous glands
how do you tell the difference b/t the 3 demodex species in dogs?
D. canis: long
D. injai: longer
D. cornei: short
injai more likely to be in sebaceous glands, on the dorsum, and in terriers
canis more likely to be in hair follicles
how do you tell the difference b/t the 2 demodex species in cats?
D. cati: long
D. gatoi: short
technically there is an unnamed species that infects cats, and this mite is medium
you get this organism from a skin scraping from a dog. what is it?
Demodex canis
tell me about the pathogenesis of demodicosis.
genetic: bulldogs, pitbulls, Shar Pei, boston terries, WHWT, Great Dane, scottie
immunologic abnormality: hypothyroidism, Cushings, immunosuppressive drugs, neoplasia, immune system abnormalities
young dogs should be assessed for concurrent parasitic infections, poor nutrition, or other stressors
adult onset dogs should be assessed more carefully for underlying immunosuppressive conditions -
Who is this man?
Otodectes cynotis (ear mite)
What is Cheyletiellosis? Who does it affect? What are the C/S?
infection with Cheyletiella, a large, non-burrowing mite. They infect dogs, cats, and most often rabbits. They are highly contagious and zoonotic (humans)
typical presentation is scaling dermatosis over dorsum in dogs + cats. Some cases present with minimal lesions and with progression, dermatologic signs can become widespread with secondary lesions.
“Walking dandruff”
pruritis ranges from mild to severe
Who is this man?
Cheyletiella (there are 3 species, but I don’t wanna remember them lmao)
tell me about the different kinds of lice that infect dogs and cats.
sucking (Anoplura) and chewing (Mallophaga) lice.
Linognathus setosus (Anoplura) and Trichodectes canis (Mallophaga) = dogs
Felicola subrostratus (Mallophaga) = cats
species specific, , don’t survive well off animal
ova are operculated and firmly attached to hair shaft (vs Cheyletiella ova)
sucking lice can cause anemia and severe illness
sucking lice are slower and easier to catch compared to chewing lice
worse in winter – high heat in coats in summer kills lice
who is this man?
Notoedres cati
they have a dorsal anus, compared to Sarcoptes mites having a terminal anus
what are the C/S of feline scabies?
severe pruritis, crusting, alopecia, lichenification
head and pinnae, but becomes widespread with chronicity
what does superficial bacterial folliculitis look like? like what are C/S, who gets it, etc
usually an underlying predisposing disease (allergy, parasite, endocrine, immune-mediated, neoplastic)
lesions are commonly on trunk and inguinal regions, but all body sites can be affected
epidermal collarettes, crusts, papules, pustules, patchy alopecia
often presents with classic lesions of ringworm (“if you see a dog with ringworm, it probably has pyoderma”)
pruritis can be intense or there can be none present
what does deep pyoderma/deep folliculitis/furunculosis/cellulitis) look like? like what are C/S, who gets it, etc
deeper infection, caused by progression of pyoderma beyond the hair follicle (rupture of follicles = furunculosis). S. pseudintermedius usually involved, but also can involve E. coli, Proteus, or Pseudomonas
more severe, quite painful, can become systemically ill
localized or widespread
trunk (esp in GSD), interdigital skin (esp in short-haired dogs), chin/muzzle in young (<12mo) short haired dogs
always consider Demodex as underlying cause
nodules, hemorrhagic crusts, plaques, erosions, draining tracts
what does pyotraumatic dermatitis (hot spots) look like? like what are C/S, who gets it, etc
develops rapidly from self-trauma
circular alopecia or matted, erythematous, moist, exudative area
usually very acute and spreads rapidly
usually seen in thick-coated dogs (Goldens), and ectoparasites should be ruled out
what does fold pyoderma/intertrigo look like? like what are C/S, who gets it, etc
surface infection in a body fold (any body fold)
bulldogs and pugs are prone (coz they be wrinkly)
due to moisture, lack of airflow, maceration
what does mucocutaneous pyoderma look like? like what are C/S, who gets it, etc
affects mucocutaneous junctions of lips, nasal plank, perianal (less often) region
GSDs are prone, often bc of underlying allergy
main ddx for DLE
what is this?
post-grooming furunculosis
unique presentation in dogs seen shortly after grooming or bathing, can be associated with shampoos contaminated with bacteria
a type of deep pyoderma
how do you diagnose pyoderma?
C/S + cutaneous cytology
on cytology: cocci (intra or extracellular)
pustules are best lesions to sample
there’s a rating system based on types of bacteria found and numbers:
0: no bacteria or inflammatory cells
1+: occasional bacterial or inflammatory cells, but side must be scanned carefully for detection
2+: bacteria or inflammatory cells present in low numbers, but detectable rapidly without difficulties
3+: bacteria or inflammatory cells present in larger numbers, and detectable rapidly without any difficulties
4+: massive amounts of bacteria or inflammatory cells present and detectable rapidly without difficulties
what are the C/S of dermatophytosis?
scaling, crusting, alopecia
feline: usually ≥1 roughly circular areas of alopecia with/without scaling and erythema. pruritis is variable, but tends to be absent or mild
canine: variable presentation, can be “classic” ringworm, or severe facial dermatitis that looks like pemphigus foliaceus, or fungal kerions (highly inflammatory nodular lesions, usually from M. gypseum)
basically, dermatophytosis can look like just about anything. consider it high on ddx for cats
most common sites: face, pinnae, paws, tail, but can affect any area
how do you diagnose Malassezia?
cytology (tape technique)
fungal cultures are NOT useful for diagnosis
remember to look for underlying causes (allergy, seborrhoea, endocrine, etc)
