Shop bought wormer hasn't worked

Gave my dog Bob Martin 3 in 1 wormer a week ago and 3 months before. He has been scooting his bum and thought it was anal gland, he had 2 course of anti biotics and flush a few days ago, only to discover what looks like tapeworm in his stools today. What should I do now as he only had the wormer a week ago? He was a bit better but noticed he was biting his bum only yesterday.

Hello - It would not be unusual to pass worms after treatment with Praziquantel, which paralyses worms in the intestine and forces them to 'let go' of the intestine lining. Your vet or pharmacist can check whether this is a reasonable explanation under the circumstances / time scale identified.  Your vet could also work with you to identify the worms and to ensure that your dog has received / is receiving appropriate treatment, given the type and their lifestyle.  There are many reasons for licking the anus including itching or as a manifestation of pain.  Worms, inflammation (allergy) or full anal glands may account for this.  Where infection is proven, the MSD veterinary manual recommends an appropriate antibiotic applied directly to the area, but underlying factors may need to be identified and treated, depending on the situation.  Remember that anal gland disease is chronic (ie long-term with a habit of recurring), so it is a good idea to discuss long-term expectations and their specific case with your vet.  Wishing you and the patient all the best.