Pruritic Cat in a Multi-Cat Shelter with Limited Isolation Space
A municipal shelter with 40 cats in two rooms has 6 cats with intense pruritus, self-inflicted excoriations on the face and neck, and crusting along the ear margins. Two cats also have papules on the abdomen. The shelter has one isolation room with 4 cages, which is currently occupied by 3 cats with upper respiratory signs. Intake is open and the shelter is at capacity. Ringworm culture from one cat is pending; a prior dermatophyte culture from the room was negative 2 months ago. Staff have been using the same gloves between cats and cleaning cages with a quaternary ammonium product. The shelter veterinarian must decide how to manage the outbreak without depopulating.
1. What differential diagnoses would you rank, and what is the most likely single cause given the signalment and lesion distribution?
Read the worked answer
Top differentials for intensely pruritic, crusted facial/ear-margin and abdominal papular disease in a group-housed cat population:
- Notoedres cati (feline scabies) - intensely pruritic, crusting on ear margins, face, and elbows; highly contagious; human transient lesions possible. This fits the ear-margin crusting and rapid spread best.
- Sarcoptes scabiei (less common in cats but possible).
- Cheyletiellosis - pruritic, often with dorsal scaling; zoonotic.
- Demodex gatoi - contagious, pruritic, often with less obvious crusting.
- Hypersensitivity (flea, food, atopic) - usually not this explosive across 6 cats simultaneously.
- Dermatophytosis - usually less pruritic and more alopecic, but must remain on the list in a shelter.
- Otitis externa / ear mites (Otodectes) - pruritus focused on ears, but the facial/abdominal papules point elsewhere.
The most likely single cause is Notoedres cati, given the ear-margin crusting, facial excoriations, and rapid cluster of cases. Diagnosis: superficial skin scrapings (multiple sites, with mineral oil) and/or fecal flotation; mites may be hard to find, so a therapeutic trial is reasonable. Dermatophyte culture should still be run to rule out concurrent ringworm.
2. Given only 4 isolation cages and 3 occupied, propose a workable control plan, including treatment and environmental measures.
Read the worked answer
A pragmatic shelter plan:
Triage and cohorting
- Move the 3 URI cats to a separate area if clinically stable (or discharge to foster) to free isolation. If not possible, create a cohort ward: designate one room for the 6 pruritic cats (cohort treatment), keeping them physically separated from the general population.
- Stop new intakes into the affected rooms until control is achieved; divert to foster.
Diagnosis and treatment
- Skin scrapings on all 6; treat presumptively for Notoedres while awaiting results because of contagion risk.
- Treat all in-contact cats in the affected rooms (not just the 6) - scabies is contagious before signs appear.
- Systemic options: selamectin or ivermectin (repeat in 2 weeks per label/protocol); treat all cats in the cohort. Confirm product and dosing with the veterinarian; avoid ivermectin in heartworm-positive or MDR1-suspect animals and follow label species restrictions.
- Treat secondary bacterial infection if present; provide Elizabethan collars for self-trauma.
Environment
- Mites survive off-host for days; clean and disinfect cages, bedding, and fomites. Quaternary ammonium is inadequate against many parasites - use mechanical cleaning plus an appropriate acaricidal/environmental product and discard porous bedding.
- Change gloves between cats and use dedicated equipment per cohort; this is a major transmission route.
Monitoring
- Re-scrape or reassess at 2 and 4 weeks; treat until two negative scrapings or clinical resolution.
- Track new pruritic cases weekly; if cases appear outside the cohort, expand treatment.
Communication
- Notoedres is zoonotic (transient itchy papules); advise staff and adopters. Document the plan and review at 2 weeks.