It's possible he may need to be de-wormed again. Can you bring in a stool sample to the vet for testing? Our experience is that underweight dogs are usually that way because of parasites, not because they were underfed. Pups coming from shelters/pounds get de-wormed with Panacur here three times at ten day intervals ie. 3 days Panacur, 10 days without, 3 days Panacur, 10 days without, and 3 days Panacur again to ensure all life stages of parasites are eliminated. It's the most effective intestinal parasiticide we've used. We then follow up with a monthly topical treatment like Advantage Multi or Revolution.
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