Dermatology Flashcards
what are the most common signs presented by an animal with a dermatology issue?
pruritus scale alopecia crusting ulceration erosion nodules
what can pruritus be due to?
allergy
parasites
microbial infection
ears
what type of disorders are implied when scale is present?
keratinisation disorders
what are primary skin lesions?
those that develop within the skin of their own accord
what is alopecia?
hair loss - may also be secondary
what is a bullae?
localised collection of fluid >0.5cm in diameter and larger than a vesicle
what is erythema?
a diffuse or localised redness of the skin which disappears with diascopy
what is a macule?
flat skin discolouration <1cm in diameter without surface elevation or depression
what is a nodule?
solid elevation greater than 1 cm usually extending into the dermis
what are large nodules referred to as?
masses
what is a papule?
small solid elevation of skin up to 1cm in diameter
what is a papule caused by?
infiltration of inflammatory cells, fluid or foreign material (calcium), with oedema and epidermal hyperplasia
what is a patch?
localised flat change in skin pigmentation larger than 1cm in diameter (a big macule)
what is a plaque?
flat topped elevation of the skin >0.5cm, flatter than a nodule
what is a plaque formed from?
coalition of papules
what is a pustule?
small elevation of epidermis filled with purulent material
what is a vesicle?
small elevation of the epidermis filled with clear fluid <0.5cm in diameter (blister like)
what is a wheal?
sharply raised lesion consisting of oedema, appears and disappears within minutes to hours
what are secondary lesions created by?
scratching, chewing or other trauma to the skin
what are secondary skin lesions the result of?
infections
evolve from regressing primary lesions
what is an comedone?
dilated hair follicle filled with cornified cells and sebaceous material
what is a crust?
dried exudate, cells, pus and scale adherent to the surface
what is an epidermal collarette?
excoriation / erosion, superficial damage to the epidermis
what is a fissure?
linear cleavage into the epidermis
what is hyperkeratosis?
increase in thickness in the cornified layer of the skin
when is hyperkeratosis often seen?
chronic skin disease
what is hyper and hypopigmentation?
changes in skin colour
what is lichenification?
thickening of the skin resulting in a cobblestone appearence
what is scale?
accumulation of loose fragments of the cornified layer of the skin
what is ulceration?
full thickness loss of the epidermis exposing the dermis
what is erosion?
some level of damage to the epidermis
what is involved in the process of diagnosing dermatological issues?
history
physical exam
list of viewed signs/problems
differential diagnoses which inform diagnostic plan
what is the key part of diagnosis of dermatology diseases?
history
what areas of the body are included in a dermatological physical exam?
ears (otoscope)
pads
ventrum
what questions should be asked during history taking to aid diagnosis of dermatological issues?
diet
other animals in the house
any human skin issues - zoonosis
what are the main diagnostic techniques used in dermatology?
acetate tape skin scrapings impression smears flea comb trichogram skin biopsy
what can be found during acetate tape for cytology?
malassezia
bacteria
inflammatory cells
squames
what can be found from performing deep skin scrapings?
demodex mites
what can be found from performing superficial skin scrapings?
cheyletiella
sarcoptes
what can be found by performing impression smears of skin?
inflammatory cells
malassezia
bacteria
what bacteria may be found after performing impression smears?
staphylococci
bacilli - Pseudomonas
where should be swabbed when performing an ear swab?
bottom of vertical canal
what may be found when testing with a flea comb?
fleas
cheyletiella
what is a trichogram?
hair pluck
what is anagen hair?
new growth within follicle
what is telogen hair?
resting phase of hair growth
what may be found from a trichogram?
anagen and telogen hair mite and lice eggs evidence of pruritus dermatophytosis hair shaft abnormalities
how can evidence of pruritus be seen in trichogram?
broken ends of hairs
what is dermatophytosis?
infection of hair and skin caused by dermatophytes
what may be evidence of flea infestation seen from flea combing?
flea faeces - small red spots
what breed of cats is dermatophytosis often seen in?
persian
what are the signs of dermatophytosis?
scaling
alopecia
how can dermatophytosis be diagnosed?
Wood’s lamp
microscopy
dermatophyte test medium
culture
how does a Woods lamp test for dermatophytosis work?
use UV light to check for fluorescence of bacteria on skin
what test medium is used for dermatophytosis?
lactophenol cotton blue
how long will a dermatophytosis culture take?
2 weeks at room temperature
how can dermatophytosis be treated?
topical therapy
systemic therepy
what may apparent cure of small localised lesions of dermatophytosis be due to?
hosts immune response rather than products used
where may dermatophytosis infection spread to from obvious lesions?
up to 6cm away
what effect can clipping have on dermatophytosis?
reduce environmental and host load but can spread the disease around the animal
what shampoos can be used to treat dermatophytosis?
Malaseb
Microbex
what dips can be used to treat dermatophytosis?
Imaverol
what has Malaseb been proven to help with?
decontamination of infected cats environment
how should shampoos for treatment of dermatophytosis be applied?
twice weekly and rinsed after 10 minutes
when is systemic treatment of dermatophytosis used?
for generalised, chronic infection
what systemic treatment for dermatophytosis is available in cats?
Itraconazole
how should Itraconazole be used to treat dermatophytosis?
7 days
3 x per day
7 days between each
what forms is Itraconazole available in?
suspension or capsules
what drug is used for treatment of dermatophytosis in dogs?
Ketoconazole
what is a major source of environmental contamination with dermatophytes?
fungal spores on hairs
how can dermatophytes be removed from the environment?
combination of physical cleaning and use of chemical agents
grooming equipment, collars, bedding should be thrown away
washable items should be soaked in antifungal disinfectant and then washed above 50
what is the difficulty with using chemicals to clean the environment?
staining / damage of soft furnishings
what chemicals can be used to clean the environment following dermatophyte infection of animal?
bleach (1:100 dilution)
Enilconazole - spray or smoke bomb
what are the key indications for skin biopsy?
neoplasia (suspected or obvious)
unusual or serious generalised dermatosis
condition responding poorly to therapy
other diagnostic tests not helpful
vesicles, bullae, erosions or ulcerations
what forms of anaesthetic are used for skin biopsy?
GA - most common
LA and sedation
what skin prep is necessary for biopsy?
clip but no scrub as bacteria on skin need to be preserved
what lesions should be chosen for biopsy?
multiple sites
fully developed lesions
not chronic or traumatized sites
what are the 2 main types of skin biopsy?
punch (4/6/8mm)
excision
what tests may be performed on biopsied tissue?
histopathology
culture
cytology
what are the 4 main results of a skin biopsy?
diagnostic
compatible with clinical diagnosis
not compatible with a diagnosis
non-diagnostic
what histopathologist should be chosen to deal with skin biopsies?
one with interest in skin disease
what should be provided to lab along with sample?
full history (age, breed etc)
signs
differential diagnoses
what are “flare factors”?
central and additional influences on the perception of pruritus
what are the 4 main “flare factors”?
fleas
bacterial and yeast infection
dry skin and low humidity / sweating
psychological factors (stress, anxiety)
what scale is involved in assessment of pruritus?
visual analogue scale
who will complete a VAS relating to pruritus?
owner
clinican
what should owners be specifically questioned about in relation to pruritus?
foot liking and face rubbing which may be interpreted as grooming
head shaking - not solely related to ear infection and can be a sign of generalised pruritus
why must all factors contributing to pruritus be investigated?
animal without disease manifestations may tolerate a certain allergic load - small increase may push the animal over the threshold to showing clinical signs.
naturally occurring diseases alongside pruritus may also push animals over this threshold.
There is often more than one cause
what are the clinical signs of canine atopic dermatitis?
self trauma secondary bacterial and Malessezia (yeast) infections alopecia erythema excoriation hyperpigmentation lichenification
how is canine atopic dermatitis diagnosed?
rule out other conditions that cause pruritus
what is used to select allergens for immunotherapy for canine atopic dermatitis?
intradermal injections and blood testing
what breeds of dog are particularly prone to atopic dermatitis?
GSD
Terrier
animals with lots of skin folds
what is not confirmed by allergen testing?
diagnosis of atopic disease
what can allergen testing provide?
identification of allergens of clinical significance
basis for allergen specific immunotherapy (ASIT) / immunotherapy
what are the clinical signs of pyoderma?
intraepidermal pustules easily disrupted by grooming / scratching
transient primary lesions and secondary lesions of crusting
what is produced by peripheral spread of pyoderma?
annular lesion with epidermal collarette
what aspects of pyoderma are sometimes antibiotic responsive?
lesions and sometimes the pruritus
when will pyoderma reoccur?
if underlying cause is not identified and managed
what are the common underlying causes of pyoderma?
ectoparasites
allergy
endocrinopathies
what are the 2 main types of pyoderma?
superficial
deep
what happens during superficial pyoderma?
bacteria multiply on surface of skin and in hair folicles
what happens during deep pyoderma?
infection is deep into hair follicle - often caused by demodex mite
what antibiotic is often used to treat pyoderma?
clavanic acid and amoxicillin
when does superficial pyoderma usually respond to treatment?
3-4 weeks
why may pruritus associated with pyoderma resolve completely with treatment?
pruritus may be due to immune response to Staphylococci antigens
what must happen before any investigations into allergies or endocrinopathies is started?
treat bacterial infections throughly
what is concerning about treating pyoderma with antibiotics?
advent of meticillin resistant Staphylococcus pseudintermedius with repeated treatment
what therapy may be used for pyoderma instead of antibiotics or alongside?
topical (e.g. shampoos)
clipping of coat
what is beneficial about topical therapy for pyoderma?
removes scale, crusts and exudate from skin surface
reduces number of bacteria
promotes deeper drainage of lesions
reduction of pain and pruritus
how often and for how long should topical treatment for pyoderma be used?
2-3 times weekly until clinical remission
what do products normally used to treat pyoderma contain?
chlorhexadine
how long should the shampoo be on the animals coat before through rinsing?
10 mins
what is Malassezia?
opportunistic yeast pathogen
where on the body is Malassezia pachydermatis usually found?
external ear canal, chin, perioral and interdigital areas
what molecule is Malassezia pachydermatis dependent on?
lipids
what will Malassezia pachydermatis grow on in the lab?
Saboraud’s medium
what are the predisposing factors to Malassezia pachydermatis?
alterations in skin microclimate
allergic and bacterial skin disease
where is Malassezia pachydermatis found on the body?
generalised with ventral distribution
localised to the face, feet, perianal regions and skin folds
what sign is commonly seen with Malassezia pachydermatis?
severe pruritus
what is the appearance of the skin of an animal with Malassezia pachydermatis?
erythema scale hyperpigmentation oily scale malodour
how can Malassezia pachydermatis infection be diagnosed?
impression smears
Acetate tape
culture
what test is not recommended for Malassezia pachydermatis?
serology
how is Malassezia pachydermatis infection treated?
twice weekly bathing with miconazole/chlorhexidine based shampoos
bathing with shampoos that have keratolytic effects
systemic therapy with Itraconazole
what is a major sign of Malassezia pachydermatis infection?
otitis externa
how can otitis externa infection with Malassezia pachydermatis be treated?
topical or oral steroids will control glandular hyperplasia and prevent cerumen production within the ear canal - effectively starving the yeast
what is the most important feature of a fleas life cycle from a treatment perspective?
most of the intermediate stages may be found in the hosts environment
will the flea usually try to remain on the host?
yes but usually removed by grooming or scratching
why do allergic animals often have no signs flea infestation?
cats especially, are particularly efficient at removing fleas by grooming
what is the most common ectoparasite of cats and dogs in the UK?
flea - Ctenocephalides felis
what is the term flea bite hypersensitivity used to describe?
the clinical condition seen in animals that have become sensitised to antigenic components of flea saliva
what hypersensitivity reactions are seen with flea bite hypersensitivity?
type 1 and type 4 hypersensitivity reactions with late onset IgE and continuous basophil response
what signs are seen with flea bite hypersensitivity?
seen on animals dorsal and lateral areas allopecia excoration erythaema thickening of skin pruritus
what can be used to help diagnose flea bite hypersensitivity?
history
compatible clinical signs
evidence of fleas or flea excreta in the hair coat
evidence of flea infestation on in-contact animals
evidence of Dipylidium caninum infestation
positive response to flea control programme
elimination of differential diagnoses
positive responses to intradermal / serology testing with flea saliva allergen
what are the factors which influence the efficacy of flea control?
formulation hair coat length bathing or swimming use of insecticidal products on the animal insect growth development inhibitors
what are the best formulations of flea control?
spot on is best
sprays can work but a lot needs to be used
what do insect growth development inhibitors do to affect flea lifecycle?
decrease the viability of eggs
when are insect growth development inhibitors not effective?
pupae and pre-emerged adults remain unaffected and viable for long periods
what is the best mechanical control method for indoor management of fleas?
through vacuuming
what effect will vacuuming have on fleas in the environment?
removes larvae and eggs
removes organic debris / flea faeces which are nutritional support for larvae
improves efficacy of environmental spray treatment by aerating carpet before application
what is not recommended to remove fleas from the environment?
carpet shampooing and steam cleaning due to residual humidity providing optimum growing environment
what is the main aim of flea control for unaffected puppies, kittens and adults?
prophylaxis
how should unaffected puppies, kittens and adults be treated for fleas?
regular use of topical on-animal product with demonstrated efficacy, long duration of action and acceptable safety
effective, safe environmental product such as the IGIs
how do many owners realise that their pet has a flea infestation?
they are being bitten themselves
how should an infested dog, cat or environment be treated?
effective, fast acting pesticide is required for all in contact pets
treatment of environment that includes insecticide to deal with newly emerging adults
adequate vacuuming
how should animals with flea allergy dermatitis be treated?
on-animal insecticide
environmental insecticide
use of IGI to ensure long term control
adjunctive treatment with short acting glucocorticoids and/or antibiotics
what is crucial for animals with flea allergy dermatitis?
fast effective insecticide treatment followed by a preventative programme
what can lead to failure to achieve flea control?
failure to treat all animals in the house
failure to treat effectively with an on animal product
failure to remove fleas from environment
what histological changes are seen in an animal with demodex?
mural folliculitis - inflammation of hair follicle walls
folliculitis and furunculosis - superficial and deep boils
nodular dermatitis (itchy dumps on skin) in some cases
interface mural folliculitis
how is demodex diagnosed?
deep skin scrapings
hair plucks
skin biopsy
is skin biopsy a routine procedure for finding demodex?
no
under what circumstances does generalised demodicosis occur?
immune system is suppressed
in what animals is demodex common?
young dogs <18 months
also seen as adult onset
what proportion of demodex cases recover spontaneously?
50%
should animals with generalised demodocosis be used for breeding?
no - predisposition is inherited
what defines demodex as generalised?
more than 5 lesions
one major body region affected
2 or more feet affected
does localised demodicosis usually become generalised?
rarely
describe the signs of juvenile onset / localised demodicosis
focal areas of alopecia and erythema especially on legs and head
in principle should localised demodicosis be treated?
no - spontaneous resolution in up to 90% of cases
what should happen if a single adult demodex mite is found?
reassess in a couple of weeks to see if there is demodicosis
what can cause adult onset demodex?
suppression of the immune system corticosteroid therapy hyperadrenocorticism chemotherapy neoplasia hypothyroidism idiopathic
how can the trigger of adult onset demodex be disocvered?
look at history - including any drug therapies haematology serum biochemistry endocrine function tests urinalysis lymph node biopsy radiography
what is the main treatment for demodicosis?
acaricidal treatment (fluralaner, afoxolaner, sarolaner)
how can secondary bacterial pyoderma to demodicosis be treated?
oral cefalexin for 4-12 weeks
bathe with chlorhexidine 3 times a week
how long is the life cycle of sarcoptes?
up to 3 weeks
where are Sarcoptes eggs laid?
deep in burrows in the host created by the female
where are sarcoptes mites found?
superficial layers of the skin
what sign is sarcoptes infestation particularly associated with?
pruritus
why is sarcoptes associated with intense pruritus?
due to activity of mites in skin and the development of a hypersensitivity response
how can canine sarcoptes be diagnosed?
skin scrapings
skin biopsy
ELISA blood test
what skin scrapings should be taken to diagnose sarcoptes?
multiple, superficial - avoiding crusts and excoriated areas
is skin biopsy for sarcoptes diagnosis often useful?
only supportive, rarely diagnostic with no reliable histomorphological markers
how are sarcoptes mites transmitted?
close contact
fomites
red foxes
where may animals be exposed to sarcoptes?
kennel or grooming parlour - any contamination of the environment
how should concurrent staphylococcal infections be treated alongside sarcoptes?
appropriate antibacterial therapy including antibacterial shampoo
oral antibiotics for 3 weeks
what medication is used to treat scabies?
macrocyclic lactones or isoxazolines
when may corticosteroids be given to sarcoptes patients?
to alleviate pruritus through anti-inflammatory doses (only with sarcoptes treatment alongside)
what may accompany the onset of Otodectes cynotis infection?
acute signs of irritation
what may be developed by some cats in response to feeding Otodectes cynotis mites?
profound hypersensitivity
what is the main treatment for Otodectes cynotis?
selamectin is licensed in cats as a spot on
moxidectin (Advocate)
what should be done prior to application of a product indicated for killing Otodectes cynotis mites?
wax removed from ear
what are Cheyletiella?
large surface mites associated with cats, dogs and rabbits
where do Cheyletiella live on the host?
epidermal pseudo-tunnels
what do Cheyletiella feed on?
tissue fluids
where are Cheyletiella eggs attached?
to hair of host by fine fillaments
what type of parasites are Cheyletiella?
obligate - live full 35 day lifecycle on host
what may develop in the animal in response to Cheyletiella?
hypersensitivuty
who can Cheyletiella be transmitted to?
humans - is highly zoonotic
why is presence of Cheyletiella mites deemed to be so low?
due to flea control measures
what are the clinical signs of Cheyletiellosis?
variable - most commonly observed in young animals
lesions include scaling
mild pruritus
miliary dermatitis or symmetrical alopecia
how can Cheyletiella be diagnosed?
microscopic identification of mites or eggs from coat brushings, hair plucks, superficial skin scrapes and acetate tape impressions
what is the main method of treatment for Cheyletiellosis?
selamectin applied monthly
moxidectin
spraying with fipronil or permethrins
bathing with selenium sulphide or flea shampoos
what are Trombiculids known as?
harvest mites
what are harvest mites?
6 legged larvae of Trombicula autumnalis
where are Trombicula autumnalis found?
present in vegetation in mid to late summer and autumn - particularly in chalk uplands
when do Trombiculids attach to the host?
larvae attach and feed for 3 days before completing life cycle in the environment
where do Trombiculids parasitize?
relatively hairless skin (e.g. Henry’s pocket, interdigital spaces and ventrum)
can Trombiculids be seen with the naked eye?
yes - orange in colour and tend to group together
what are the signs of Trombiculids?
erythema
papules
crusting
- depends on development of hypersensitivity
how is presence of Trombiculids diagnosed?
observation of orange six legged larvae and confirmed by microscopy
what are the treatment options for Trombiculids?
spraying with flea products containing fipronil (every 2 weeks to prevent mite attachment) glucocorticoid therapy (if hypersensitivity reaction)
what are the 2 main types of louse?
biting - Felicola subrostratus
chewing - Trichodectes canis
what is the lifecycle of lice?
confined to the host and takes 14-21 days
where are lice eggs attached?
to the hairs
how many nymph stages of lice are there before the adult?
3
are lice contagious?
yes - but host specific
what are the clinical signs of lice?
pruritus and scaling of the dorsum
may develop severe self trauma
in what animals are lice common?
young animals
debilitated animals
overcrowded or multi-animal houselholds
how are lice diagnosed?
careful exam of the coat for adults or eggs
acetate tape impression
coat brushings and hair pluck
how are lice treated?
selamectin and moxidectin (licensed)
fipronil spray (one off)
clip heavily infested animals
why may clipping highly lice infested animals be an effective form of treatment?
reduces the burden of eggs and adults to allow effective use of topical therapies
what are the 3 main zoonotic ectoparasites?
fleas
sarcoptes (scabies)
cheylitellia
how many hosts are involved in a tick lifecycle?
3
why are ticks viewed as so dangerous?
due to what they carry rather than them themselves
how should you remove a tick?
using tool or fine tipped tweezers
grasp tick as close to the skin as possible
pull upwards firmly and steadily
don’t squeeze or crush tick body
where should exotic ticks be reported to?
UK tick surveillance scheme
how can ticks be treated?
fipronil licensed for monthly control of ticks
deltamethrin (dogs) and flumethrin (cats) based products in a collar
what is the main treatment option for dogs and ticks?
isoxazoline family of 4 drugs
pyripole based products
what parasites are included in the PETS travel scheme?
ticks
tapeworms
what tapeworm is prevented from infecting the UK by the PETS travel scheme?
Echinococcus multilocularis
what is the definitive host of echinococcus granulosus?
carnivores - have little impact on their health
what is caused by Echinococcus granulosus in the intermediate host?
cysts in the liver and lungs - take up space and affect organ function
what is the name of the cyst caused by echinococcus granulosus?
hydatid cyst
what is used to treat echinococcus granulosus in the definitive host?
praziquantil
how is echinococcus granulosus diagnosed and treated in the intermediate host?
diagnosis: PM, ultrasound or radiography
no treatment
how can echinococcus granulosus be controlled?
regular worming of dogs
keep dogs away from fields of sheep to prevent sheep becoming infected
meat should be carefully inspected
what are the 3 main zoonotic species of tapeworm?
echinococcus granulosus
taenia
echinococcus multilocularis
what are the taenia species found in dogs?
taenia multiceps taenia seralis taenia pisiformis taenia hydatigena taenia ovis
what is the main taenia species of cat?
taenia taeniformis
what is the intermediate stage of taenia hydatigena?
cysticerus larvae in abdomen or liver
what is the intermediate stage of taenia multiceps?
coenurus larvae in brain and spinal cord
what is the intermediate stage of taenia ovis?
cysticercus larvae in abdomen or liver
what is the intermediate stage of taenia taeniaeformis?
strobilocerus larvae in liver and abdomen
how are cats and dogs infected with taenia?
hunting / eating infected meat
how can taenia hydatigena be controlled?
stop dogs eating offal (don’t feed, remove dead sheep)
stop sheep eating eggs (prevent dogs defecating in pasture)
worming
what is caused in the intermediate host by taenia multiceps?
space occupying lesion
destruction of nervous tissue
what is the destruction of nervous tissue by taenia multiceps known as?
Coenurus cerebralis
why must all pets be wormed 1-5 days before entering the UK?
to prevent echinococcus multilocularis from entering the UK
how is echinococcus multilocularis spread?
in gut of DH (carnivore) - shed in faeces - attaches to GI wall of IH (rodents and humans) - DH infected when eats IH
how is echinococcus multilocularis prevented from becoming endemic in the UK?
foxes treated with praziquantil
PETS scheme to prevent entry to UK without praziquantil
how is diplidium canium spread?
egg packets expelled in faeces
eggs consumed by fleas (IH)
fleas ingested by DH
when does toxocara become infectious?
egg becomes embryonated - contains L3 larva - within the environment
what is the lifecycle of toxocara canis?
hatch in the gut
hepato-tracheal migration
can have somatic arrest in adults (stop growing) and be reactivated especially around pregnancy
what may reactivate toxocara canis?
pregnancy
how can T.canis be prevented and controlled?
routine worming of dogs
early worming of pups
care with pregnant bitches
where is a major source of toxocara canis eggs within the environment?
puppies
what may be used to treat toxocara canis?
benzimidazoles: fenbendazole
endectocides: milbemycin, moxidectin
piperazine citrate
what is the worming protocol for pups with toxocara canis?
2 wees old
then weeks 4, 6, 9 and 12
then every 3 months
how should the bitch be wormed before whelping to prevent toxocara canis being passed to her pups?
fenbendazole daily from day 42 - 2 weeks after whelping
moxidectin and selamectin spot on
what routine worm control is needed in adult dogs?
monthly (or every 3)
how should cats be wormed to protect kittens from toxocara?
no transplacental transmission (only transmammary) so kittens can just be wormed from 3-4 weeks
do cats need to be wormed against toxocara?
yes - paratenic hosts of T.cati
what are the clinical signs of angiostrongylus?
cough dyspnoea anaemia depression anorexia coagulopathy
what can angiostrongylus lead to?
pneumonia
how is angiostrongylus diagnosed?
antigen blood test
how is angiostrongylus treated and prevented?
no cure
prevention: moxidectin and milbemycin
