Demodicosis
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Caused by Demodex
Pathogenesis and epidemiology
- Squamous demodecosis
- Less serious
- Dry reaction
- Alopecia, desquamation and skin thickening
- Absent to mild pruritus
- Follicular/pustular demodecosis
- More serious
- Skin invasion by staphylococci
- Skin becomes wrinkled, thickened and contains pustules which ooze serum, blood or pus
- Affected animals may be seriously disfigured
- Severe pruritus is associated with secondary infection
- Immune factors are important in determining the severity and occurrence of demodecosis
- Familial susceptibility
- Immunosuppression
- Immunosuppressant therapy
Diagnosis
- Liquid paraffin applied to a skin fold
- Deep skin scraping
Control
- Not easily accessible to acaricides due to their deep location in the skin
- Repeat treatments needed
- Recovery may take several months
- To aid acaricide penetration, clipping a dog's coat and washing is recommended
From Pathology
- Demodex are normal inhabitants of hair follicles and sebaceous glands
- Have to have increased number of immature mites to classify as infestation
- Host-specific
- Occurs in dogs, cattle, sheep, goats, pigs, horses and cats
- Transmits during nursing from dam to offspring
- Demodex canis in dogs:
- Generalised or localised
- Mainly young dogs affected or adults with other disease (hyperadrenocorticism, hypothyroidism)
- Often inherited in pure bred
- Grossly:
- Localised: scaly, erythematous, macular, alopecic areas; usually face or front legs
- Generalised: large, coalescing lesions, patches, erythema, alopecia, scales, crusts
- Microscopically:
- Localised: lymphoplasmacytic perifolliculitis with hyperkeratinisation, sebaceous adenitis, low pigment, intraluminal mites
- Generalised: perifolliculitis and follicular hyperkeratosis, follicular pluggingf, bacterial proliferation, bacterial neutrophilic folliculitis
- May cause folliculat rupture -> furunculosis, cellulitis, lymphadenitis and septicaemia