What do black pus and pimples mean on dog skin?

[FutureVet]

My dog Corea was recently adopted by my boyrfriend and I from a shelter in April. When we adopted her she had no hair and thousands of bumps on her skin as a result from a severe infection of mange. She was deemed cured in August and received all the shots necessary after she was off her treatment. She had a beautiful coat and was healthy. However, in the past two weeks she started getting bumps on her skin and losing her hair. We gave her a bath with some oxydex hoping it would help but it only worsened. We also wiped her with some Clearasil wipes and that seemed to help. But, this morning we found she ha some black pimples and when we took a closer look it seemed like black pus was coming out of some of her pimples. What does this mean? Does she have mange again?
Note that we did recently find out that our building had a bed bug infestion and we have thrown out the matress and done extrenous cleaning of our apt. Could this be due to bed bugs? Help.

[Kimberly Coyner, D.V.M., DACVD]

Pimples and hairloss mean there is infection in the hair follicles. The 3 kinds of infection are bacteria, demodex, and dermatophyte (ringworm). With your dog's history, a recurrence of the demodex mites and a secondary bacterial skin infection are most likely. I recommend taking your dog into your veterinarian this week for skin scrapings. If demodex is found again, then treatment will need to be restarted. Options are topical amitraz every 1-2 weeks, ivermectin orally daily, or milbemycin orally daily. Regardless of the treatment, medication is continues until no live or dead mites are found on skin scrapings, and then one more month for insurance; the average duration of treatment is 3 months, and dogs will look normal 1-2 months before they are cured, so monthly skin scrapings are important to evaluate when it is safe to stop treatment. The most common reasons for demodex recurrence are stopping treatment too soon, or using too low a dose of medication, but in about 10% of dogs, a poor immune system makes the mites recur each time medications are stopped despite appropriate therapy. In these dogs, antiparasite treatment such as daily ivermectin or milbemycin is given for 3 months, and then on Mon/Wed/Fri for long term control. Hopefully this will not be the case with your dog, and with luck one more prolonged course of therapy will cure her this time.
Good luck,
Kimberly Coyner, DVM DACVD
www.dermvetvegas.com