Parasitic skin diseases in small animals Flashcards
What is meant by flea allergy dermatitis?
- Flea bite hypersensitivity
- Pruritic dermatitis due to hypersensitivity to salivary proteins of flea (type I or IV)
- Does not indicate infesation
What organisms, other than fleas, can animals develop hypersensitivities to?
- Insects e.g. mosquitoes, flies, lice
- And mites e.g. Sarcoptes, Otodectes
Briefly outline mosquito bite hypersensitivity (cause, species, prevalence)
- Presume antigens in mosquito saliva
- Cats mainly, but no exclusive
- Summer-autumn
- Usually animals with outdoor access
What is canine nasal (eosinophilic) folliculitis/furunculosis?
Inflammation of hair follicles
How does furunculosis develop?
- Inflammation of follicle wall so bad, breaks down, keratin from hair follicle gets into dermis and causes foreign body inflammatory reaction
- Keratin breaks down very slowly, long time for inflammation to reduce
- Furunculosis may occur in deep pyoderma
Describe the development of canine nasal folliculitis/furunculosis
- Comes up very quickly, within 12 hours, wildly pruritic and lots of reaction
- Cause unknown, bites and stings from insects strongly suspected
Describe the common clinical signs of FAD in the dog
- Pruritus: scratching, biting skin, jumping up suddenly, excessive licking, overgrooming
- Secondary results: alopecia, skin inflammation +/- skin infection, crusting, lichenification
Which areas of a dog are classically most affected with FAD?
- Caudal dorsum
- Tail base, thighs, inguinal area
Describe the common clinical signs of FAD in the cat
- Variable
- Miliary dermatitis
- Alopecia (due to overgrooming)
- Eosinophilic granuloma complex lesions
- Head and neck pruritus
What is miliary dermatitis?
Gritty, crusty papular lesions of the skin
Describe the clinical signs of pediculosis
- Operculated eggs attached to hairs may be seen
- Often asymptomatic
- may see poor hair coat, scaling, papules, crusts, variable pruritus
- Heavy infestation can cause anaemia and lethargy
- Infestation may reflect poor hygiene, nutrition or immunity
Describe the clinical signs associated with mosquito hypersensitivity
- Papules
- Eruptions
- Hairless regions most affected e.g. bridge of nose, preauricular skin, occasionally footpads
Describe the appearance of canine nasal (eosinophilic) folliculitis/furunculosis
- Acute eruption mainly affecting muzzle and ears
- Papules
- Nodules (+/- ulcerated)
- variable pruritus but can be intense
List common differential diagnoses for flea allergic dermatitis in the dog and cat
- Environmental atopy (but would commonly see signs on feet, ventrum and face)
- IN cat, clinical signs are same as food atopy or environmental atopy
- Other ectoparasites
- Microbial infections
Briefly outline the life cycle of lice
- Adults survive off host for 3 days
- Life cycle approx 3 weeks
- Nits can cause indirect infestation from bedding, blankets, esp. if large no. of dogs
Describe the diagnosis of FAD in the dog or cat
- Flea comb
- Vigorous coat brushing and examine debris on moistened paper
- Microscopy of flea dirt collected on combing or tape stip
- Known down fela spray for demonstration of dead fleas e.g. permethrin on dogs
- Examine faeces for tape worm segments
- False negatives common, esp. in cat as groom well
- Intradermal allergy testing for FAD
- In vitro/serological testing for FAD
- Response to therapy
Why is examination of the faeces for tapeworm segments a valid method for the diagnosis of the presence of fleas on a dog or cat?
Dipylidium caninum is spread by fleas
Discuss the use of intradermal allergy testing for FAD
- May test with other environmental allergens
- Up to 30% false positive reactions with flea saliva
- FAD can involve type I or type IV reactions, can take 48 hours to see reaction but this is rarely assessed
Discuss the use of in vitro/serological testing for FAD
- Measure antigen specific IgE (type I)
- Does not document type IV reaction
- Negative does not exclude FAD
- Rarely done
Discuss the use of response to therapy as a method of diagnosis
- Best method
- Range of effective products available
- Diagnosis is confirmed by response to thorough flea control trial
Outline the management of FAD
- Pupae not responsive to treatment so need to cover emerging adults
- Can take 140 days for pupae to emerge so need to cover this period i.e. treatment may take more than 3 months treatment
- Permethrin household adulticide, lasts 6-7 weeks, repeat
- Whole life cycle usually complete in 3-4 weeks, can be as short as 2 or as slow as 6mo depending on environmental conditions
What control measures are available for fleas?
- Mechanical removal (flea comb, vacuum house)
- Repellents (limited in cats to only flumethrin)
- Adulticides, larvicides, ovicedes
- Products that inhibit development e.g. IGRs, chitin synthesis inhibitors (lufenuron)
Which drugs have an effect on environmental and adult life stages of fleas? Discuss
- Imidacloprid
- Selamectin
- Indoxacarb
- BUT incomplete, imidacloprid only in hair and dandruff that falls off animal
- Need to use household spray as well for complete coverage
List the drugs that are effective against adult fleas
- Dinetofuran
- Permethrin, flumethrin, tetramethrin
- Fipronil
- Pyriprole
- Nitenpyram
- Afoxolaner, flurolaner, sarolaner, spinosad
- Imidacloprid
- Selamectin
- Indoxacarb
List the drugs that are effective against the environmental life stages of fleas
- Pyriproxyfen
- S-methoprene
- Lufenuron
Give an example of a spot on product consisting of a pro-drug that is only activated by the parasite
Indoxacard
Give an example of a spot on produce that kills fleas and sarcoptic mage, but has no action against demodicosis
Selamectin
Give examples of flea adulticides that will not lose efficacy with repeated bathing
Spinosad, isoxazolines
Give an example of a very short acting (24h) knock down flea adulticide
Nitenpyram (rarely used)
Give an example of an oral product effective against fleas and ticks (and likely demodicosis but off label), and lasts for 3 months
Flurolaner
How is pediculosis diagnosed?
Demonstration of live/eggs with magnifying glass or under microscope from coming, unstaned acetate tape strip or hair pluck
Outline the treatment for pediculosis
- Relatively easy as entire life cycle is on host
- Many flea adulticides are effective incl. imidacloprid, fipronil, selamectin, permethrin
- Treat all in contacts
- recommended environmental cleaning incl. removal and washing of bedding
Outline the management of mosquito hypersensitivity
- avoid outdoors, esp. dawn and dusk
- Use insect repellents (permethrins are toxic to cats, flumethrin can be used)
- Symptomatic treatment with glucocorticoids
Outline the management of canine nasal eosinophilic folliculitis/furunculosis
- Glucocorticoids, antihistamines
- Insect repellents
Outline the life cycle of Cheyletiella
Life cycle 3-4 weeks, may survive off host for 5-6 weeks
List the surface and deep mites that affect dogs and cats
- Surface: Cheyletiella, Otodectes, Neotrombicula
- Deep: Sarcoptes,, Demodex
Describe the clinical signs of Cheyletiella
- Pruritus, scaling
- Esp dorsal trunk
- Walking dandruff
- Often very dramatic in rabbits, less so in dogs and cats (often just pruritus)
What are the key differential diagnoses for a condition that presents similarly to Cheyletiella?
- Flea infestation
- Scabies
- Atopy
What species are at risk of cheyletiellosis and define the risk?
- Dogs, cats, rabbits, guinea pigs, humans
- HIGHLY contagious
How is cheyletiellosis diagnosed?
- Microscopic examination of superficial skin scrapings, unstained tape strips, coat brushings/combins
- Brushings/combings most sensitive, few in coat if mild and otherwise easy to miss. Collect debris, place in LP on slide
Outline the management of cheyletiellosis
- Environmental treatment important, household flea spray
- Contaminated materials must be burnt, steam cleaned or chemically treated
- no licensed products but effective treatments available
- Topical: fipronil q3-4 weeks, selenium sulphide shampoo weekly, amitraz (not for cats) q2weeks 3x
- Systemic: selamectin spot on q2-4 weeks, isoxazolines (anecdotal)
Describe the clinical signs of Otodectes cynotis
- Ear irritation
- Head shaking
- Excessive ear wax
- Occasional irritation of face or body
What are important differential diagnoses for a presentation similar to that for Otodectes cynotis?
- Malassezia
- Flea infestation
How is Otodectes diagnosed?
- Visualise ear mites by otoscopy
- Detect ear mites/eggs in cerumen
How long is the life cycle of Otodectes?
3 weeks
Describe the treatment of Otodectes cynotis
- Topical in ears: acaricidal in ears 2xdaily for 3 weeks. Surolan, canaural licensed but contain no anthelmintic, but effective
- Systemic: selmectin, moxidectin spot-ons, sarolaner licensed
- Regular ear cleaning
- Must treat in contact animals
Why must topical ear drops be used for 3 weeks in the treatment of Otodectes cynotis?
Eggs are resistant to treatment so have to treat over 3 weeks to cover life cycle and kill adults
Describe the occurrence of trombiculosis
- Seasonal (summer and autumn)
- regional geographic distribution
Which species are affected by Neotrobicula autumnalis?
- Dog, cats, occasionally humans
- NB humans infested from environment rather than dog or cat
What is the clinical significance of trombiculosis in dogs?
- Can cause discomfort
- But also associated with seasonal canine Illness
Briefly outline Seasonal Canine Illness
- Disease that kills dogs in Thetford forest, Clumber park, Sherwood forest
- Acute gastroenteric disease, collapse, often fatal
- Have large number of harvest mites in them
- Very regional, unknown cause
Describe the clinical signs of trombiculosis
- Papules
- Crusts
- Pruritus
- esp. interdigital spaces, pinnae (Henri’s pocket) ventral abdomen, anal region
- Visible orange larvae
How is trombiculosis diagnosed?
- Demonstration of larvae on skin
- Skin scrapings in liquid paraffin
Describe the treatment for trombiculosis
- No licensed product but various products used
- Fipronil q2weeks
- Selamectin limited efficacy
- Isoxazolines to be determined
How long is the life cycle of Sarcoptes scabiei?
3 weeks
Which species of Sarcoptes affects dos and foxed?
Sarcoptes scabiei var. canis
Is there a risk to humans from Sarcoptes scabiei?
Yes - zoonotic
Describe the clinical signs of Sarcoptic mange
- Intensely pruritic
- Positive pinnal-pedal scratch reflex
- Papules, crusts, especially on pinnal margins, elbows, hocks, sternum
- Other areas may be affected
What methods are used in the diagnosis of sarcoptic mange
- Clinical signs (if dog cannot stop itching, high suspicion), acute onset, unresponsive to prednisolone
- Skin scrapings
- Treatment trial
- IgE serology
- ELISA serology
- Histopathology
Describe the method for skin scrapings in the diagnosis of sarcoptic mange
- Multiple, minimum 6 deeps scrapings
- Difficult to detect (50% sensitivity)
- Choose primary lesions in areas avoiding secondary cahnges
- Look for mites, eggs, mite faeces using LP and coverslip
Discuss the use of IgE serology in the diagnosis of sarcoptic mange
Cross-reactivity with house mites, may give false negative/false positive for house mites
Discuss ELISA serology in the diagnosis of sarcoptic mange
- Detects anti-sarcoptes IgG, highly sensitive and specific
- Can have false positive due to cross-reaction with Abs to house dust mites
- False negatives may occur as seroconversion takes 3-4 weeks
Discuss the use of therapeutic trials in the diagnosis of sarcoptic mange
- Good if no mites detected but are suspicious
- Helps distinguish from atopic dermatitis
Evaluate the use of histopathology in the diagnosis of sarcoptic mange
- Litlle use in diagnosis as are unlikely to see mites
- Non-specific inflammatory picture with eosinophils and mast cells more likely
What is Norwegian scabies?
Simply means a large number of mites found, need to look for underlying immunosuppression
Give the treatment options for sarcoptic mange
- Steroids ineffective
- Systemic acaricidals effective e.g. selamectin, moxidectin
- Licensed use: 2 spot on applications 4 weeks apart
- Off label: 3 spot on applications 2 weeks apart
- Sarolaner: oral tablet monthly, licensed
- Topical: amitraz solution or lime sulphur, both weekly for 4 weeks
Compare the use of spot on treatments for sarcoptic mange in the licensed method, or as the off label method
- Licensed: safe, well tolerated
- Off label: never for collies/herding breeds, elderly, young, debilitated animals, animals at lower margin of bodyweight band
Compare the use of amitraz and lime sulphur in the treatment of sarcoptic mange
- Amitraz: long coats need clipping, +/- prewash with keratolytic shampoo. toxicity concerns for pet and in cotact peple, use gloves, aprons, face-shileds. No longer used due to isoxazolines being better and safer
- Lime sulphur: effective, well tolerated, stains, pungent, dyes white hair yellow, but works where other treatments have failed
Describe the management of sarcoptic mange
- Zoonotic, as well as contagious
- Avoid contact, decontaminate or destroy items e.g. bedding, brushes
- Treat all in contacts with acaricide
- Use insecticidal spray for environment
- Glucocorticoids may help control intense pruritus
How long is the Demodex life cycle?
10-12 days
When does demodicosis usually occur?
In animals with immunoincompetence e.g. young animal, underlying dsiease
Explain how infection with demodex occurs
- Is a normal inhabitant of canine skin
- Not contagious, passed form dam to offspring in first few days of life
Outline the potential consequences of demodicosis
- Excessive multiplication in hair follicles and sebaceous glands leading to follicular disease on skin, folliculiis, alopecia, furunculosis, often with erythema
- Can cause deep pyoderma
Described the distribution of demodicosis on an animal
Can be localised or generalised
Describe localised demodicosis
- <6 multifocal lesions
- Well circumscribed, scaling, alopecia, +/- erythema
- Often young dogs
- Not usually pruritic
- Occasionally secondary to bacterial/Malassezia infection
- 90% self cure, 10% progress to generalised condition
What is the criteria for generalised demodicosis?
- Any of:
- > 6-10 lesions
- Entire body region
- 1 or more feet affected
Describe generalised demodicosis
- Feet affected worst prognostically
- Secondary bacterial infection common, potentially severe leading to pyrexia, lymphadenopathy, depression, occasional death
- More frequently pruritic than localised form
- Generalised alopecia and erythema
- Comedones and pustules (+ follicular casts) common
Why does pododemodicosis carry a poor prognosis?
More refractory to treatment than other areas
Compare the appearance of Demodex injai to canis
Extra long bodies, 50-100% longer than canis
Describe the key features of Demodex injai
- Sit in pilosebaceous units
- Especially on dorsal trunk of adult dogs
- Especially terriers and WHWT
- Often present with excessive greasiness
- Key differential is atopic dermatitis
Compare Demodex to Demodex canis
- Short bodies, 50% length of D. canis
- Mainly located on skin surface an follicular openings, interdigital surfaces
- Now thought to be variant of D. canis
When is demodicosis classes as juvenile onset?
1-12mo, especially common 3-6mo
What is the prognosis for juvenile onset demodicosis?
Good, usually resolves with sexual maturity if localised, as immune response improves
What is the main consequence of juvenile onset demodicosis?
Should not be bred from
When is demodicosis classed as adult onset?
4yo or more, uncommon
How does adult onset demodicosis occur?
- Usually secondary to immunosuppression
- Endocrinopathic, neoplastic, infectious etc.
What is the prognosis for adult onset demodicosis?
Guarded if underlying cause cannot be corrected, may end up with recurrent demodicosis
Describe the diagnosis of demodicosis
- Deep skin scrapes, squeeze skin before scraping
- +/- plucks (esp. face and feet), not useful alone but good ajuncive
- +/- if skin scarred or very thick e.g. Shar Pei (may see mites, folliculitis, furunculosis)
- Preparation thin otherwise will not see anything
Identify the treatment options for demodicosis
- Localised usually self resolves
- Generalised may self resolve but better to use acaricide e.g. sarolaner, moxidectin, amitraz
- Advocate
- Sarolaner
- NOT steroids
- Avermectins off license
- Treatment of secondary infection, underlying cause, relapses
Discuss the use of amitraz in the treatment of canine demodicosis
- Precautions and indications must be followed
- Can be toxic
- Weekly application
- Clip and degreasing bath first
- Care re. MAOI cross reactions
- Contraindicated in Chihuahuas and care with other small breeds
Discuss the use of Advocate in the treatment of canine demodicosis
- Imidacloprid and moxidectin spot on
- Licensed for monthly use, but info for weekly use in serious cases
- Do not go off license in collies/herding breeds
Discuss the use of isoxazolines in the treatment of canine demodicosis
- Sarolaner licensed, other unlicensed
- Use at same frequency as for fleas/ticks
- Can take up to 60 days to see significant effect
Discuss the use of steroids in the treatment of canine demodicosis
- Cannot be used
- Immunosuppression is the underlying problem and steroids will add to this
Discuss the use of avermectins in the treatment of canine demodicosis
- Superseded by isoxazolines
- Milbemycin daily PO, some risk of side effects and costly
- incremental dose increase over 10-24 days in all cases and close monitoring for adverse effects
Outline the treatment monitoring for canine demodicosis treatment
- Regular scrapings i.e. monthly
- Same sites scraped
- Record numbers of each stage of life cycle (egg, larvae, nymph, adult)
- Record dead vs alive
- Treat until have 2 negative scrapings with minimum 1 month interval
- Treatment may be required for months
Describe Demodex cati
- Follicular
- Long slender mite
- Uncommon
Where is Demodex cati found?
- In follicles and sebaceous glands
- can be locaslised to head and neck
- Or generalised
What is generalised feline demodicosis usually associated with?
Underlying immunosuppression e.g. FIV, FeLV, diabetes mellitus
Describe the clinical signs of Demodex cati
- +/- waxy otitis externa
- Patchy alopecia, erythema, scale
- May have comedones, secondary pyoderma
- Pruritus variable
What are the 2 demodex species that infect cats?
Demodex cati and gatoi
