Dandruff and scabs

Question
For the last few months, our 9 year old rex, has had dozens of scabs ranging in size from  1-8 mm all over her back (mostly around her spine). She has a lot of dandruff, too. In fact, it's hard to tell if the scabs are truly scabs or maybe just thick flakes or clumps of dandruff. (Although, if they are removed, they sometimes leave a little raw bald patch.) We were afraid she had mites, so in spite of multiple negative skin scrapings, both she and her buddy (who has no symptoms) are being treated weekly with oral ivermectin. It's been three weeks now, and there's no change. The vet also suggested flax oil, which we tried, but stopped because it made her poops very messy and soft.

She has severe spondylosis (she's on maximum doses of metacam and tramadol), and can't groom her back very well, so we brush her gently a couple times a day. She seems itchy when we brush her, but it's hard to tell otherwise, because she can't use her  back legs to scratch. She doesn't have any crusts or scabs around her ears or face.

Do you have any idea what this could be? Should we try a different mite medication? Is there anything else we can do in terms of grooming her that might help? We hate to think that she might be uncomfortably itchy, but unable to show us by scratching. Any ideas you can offer would be greatly appreciated! Thank you.

Answer
Dear Leah,

If these lesions are being caused by Cheyletiella (fur mites), which are more likely if there is dandruff, then you might have better success with Revolution than with ivermectin.  The former stays on the skin longer, which is what you need to combat fur mites, since they eat dead skin.  Revolution is topically applied, and lasts for about 4 weeks.  I'd give that a try before eliminating mites from your list of possible culprits.

If that doesn't work, then I'd suggest asking the vet about excising one of the lesions and have it sent to a lab for histopathology and identification.  It could be bacterial or fungal, though the signs you describe don't sound typical for that.

Ask the vet if a bit of Benadryl might help with any itching she's suffering, at least for temporary relief.

Hope that helps.

Dana