What Is Demodicosis?
Demodicosis (demodectic or red mange) is caused by the overgrowth of Demodex canis — a microscopic mite that normally inhabits the hair follicles of all dogs in small numbers. When the dog's immune system (particularly cellular immunity) fails or in genetically predisposed breeds, the mite multiplies unchecked.
Clinical Forms
Localised (<5 areas, paws not affected):
- Patchy hair loss in 1-5 spots, typically the face (eyes, muzzle) or forelegs.
- Mild redness or scaling, minimal itching.
- Mostly in puppies 3-18 months old. Resolves on its own in 90 % of cases.
Generalised (>5 areas or two or more paws affected):
- Extensive hair loss across the body.
- Secondary bacterial infections (pyoderma): crusts, pustules, odour.
- In young dogs (juvenile form) or adults with immunosuppression — always investigate the underlying cause (hyperadrenocorticism, hypothyroidism, neoplasia, immunosuppressive drugs).
Diagnosis
Deep skin scrape (reaching the follicle) + microscopy. Biopsy for difficult cases.
Treatment
Localised: watch and wait 1-2 months. Start treatment if no improvement.
Generalised:
- Isoxazolines (current first-line): fluralaner (Bravecto), sarolaner (Simparica), afoxolaner (NexGard), lotilaner (Credelio). Highly effective, well tolerated. Treat for 3-6 months until two consecutive negative scrapes.
- Ivermectin or milbemycin: older alternative. CONTRAINDICATED in MDR1/ABCB1 mutation breeds (Collies, Shelties, Australian Shepherds — severe neurotoxicity risk).
- Treat secondary bacterial infections with systemic antibiotics.
- In adult-onset: treat the underlying immunosuppressive cause.