
Agree with Anna 100%. I bred, exhibited and judged longcoat cavies for 25 years. In the old days Ivermectin was only actually licensed for cattle, but I was a member of the Cambridge Cavy Trust, and offered research results to my vet. He was willing to supply me with drugs and needles in bulk - I had 300 cavies then.
I told him it wasn't necessary to inject, and it had been proved successful given orally. One drop on the tongue for babies, a couple of drops for adults. I loathed giving up my Cooper's Fly and Scab, but sheep dip became impossible to get hold of (my vet used to cover his ears whenever I mentioned how great it was), he knew it worked, but it was being phased out, and supplies dried up.
Most people that showed to any great extent, would make sure that their show pigs were given Ivermectin before going to a show, as a precaution. If using Ivermectin orally, dose the guinea pigs at 10 day intervals. 3 doses should do it, and I would always treat animals in the same cage, as, even if showing no signs, they are often "carriers".