I had the opportunity to sit with Cannoli for a while last week and decided to inspect her fur. Imagine my chagrin when I found little wriggly things in several places. Ew! (Photo of the little critters can be seen here.)
It's one of the risks of letting my guinea pigs have outdoor time. It happens infrequently; I've dealt with infestations only two or three times in the last 15 years. The last time it was little tiny bugs. This was the first time my pigs picked up something that looked wormy. I inspected Pinniped and found a few on her as well. Neither pig seemed to be bothered their passengers, but I wanted them gone!
Ivermectin is often used to treat guinea pigs that have lice or mites, and it works on all sorts of blood-sucking parasites. I have treated my pigs with ivermectin before, for mites as well as what they've picked up outdoors. I've tried both the oral paste and the pour-on treatment. Of the two, the topical ivermectin is so much easier to measure and use. The oral paste requires diluting it, because it's so strong. I was very nervous about preparing it correctly. The 0.5% pour-on can be used straight out of the bottle, so it makes dosing much easier.
Unfortunately, my last bit of pour-on ivermectin had dried up, so I had to buy more. It's inexpensive, but the smallest bottle is 250ml. At 0.1ml per kg, for two treatments to a 1kg guinea pig... that's enough to treat 1,250 guinea pigs. More than I'll ever meet! I've heard that other countries sell ivermectin treatments for birds in much smaller vials and in different concentrations.
It turns out, guinea pig was not the creepy-crawlies' host of choice. Their numbers had dwindled by the time I bought the ivermectin. Regardless, I treated the girls just to make sure. Ivermectin dosing is based on weight and should be measured accurately. The dose was 0.08ml for Pinni and 0.11ml for Cannoli, which was a few drops per pig. They got a little behind each ear, and a bit on the middle of their rumps. Some of my pigs have been annoyed by the application (I think the stuff tingles on the skin), but these two didn't seem the least bit bothered. I stripped their cage at the same time and put everything into the wash.
They'll get a second application 7-10 days after the first and hope this will be the end of it. I'll need to get into the habit of regular inspections after they've been outside.
Disclaimer - I am not a veterinarian. These are my experiences with guinea pig parasites and treating them with ivermectin. If you have questions about diagnosing and treating your guinea pig for parasites, you should consult your veterinarian. For more information, I would recommend reading up on ivermectin and other parasite treatments on the Guinea Lynx website and forum.