Guinea Pig Lice

2012 August 18

Back in the June 13 posting about rat lice, I closed with this:
And in the future, any time that we get a new pet, you can bet we are going to check them over for lice first thing.”
Well, after the last rat died of old age a while back, Sam ran a family vote on what the next small-animal pet was going to be, and we settled on a guinea pig. We found some really cute young guinea pigs at the local pet shop, brought one home, and started looking him over. There was nothing immediately obvious to the eye, but when we combed him with our steel “nit comb”, there were a couple of tiny little white objects. They were a bit smaller than the commas in an average printed text, and they moved pretty briskly.

To get pictures, we had to shake them off of the comb and onto a piece of sticky-side-up packing tape. This one landed on its back, and lay there with its little feet waving in the air.

Yes, they’re lice all right. These lice are clearly distinct from the rat lice. The guinea pig lice are more elongated, slimmer, less hairy, and move a lot faster.

These look to be Gliricola porcelli, the “slender” or “running” guinea pig louse. Unlike the rat lice, which were “sucking” lice that actually pierce the skin and suck blood, these were in the distantly-related “chewing” lice family. The chewing lice eat skin flakes, and chew through soft/thin areas of skin to get at the blood and fluids that seep out. And, like most other lice, these are very host-specific and won’t make the jump to the dog or to the humans in the house (or, if we still had them, to rats)[1].

At any rate, they aren’t fun for the guinea pig, so we wanted to get rid of them. First step was thorough combing with the nit comb, followed by treatment with “Revolution” (selamectin), which is applied topically right between the shoulder blades. We used this instead of the “Frontline” (fipronil) that we used on the rats because we found some suggestions online that fipronil could be excessively toxic to guinea pigs, while being less effective for killing guinea pig lice than the selamectin is. This treatment was followed up with cleaning out the cage, and continued groomings with the nit comb[2]. We were prepared to give a second treatment to make sure we got them all, but regular nit-combings over the next few months did not turn up any new lice. And now, we still nit-comb periodically to check, but overall the problem seems to be solved.

[1] Sandy is amused by the implications of this: there are no wild hosts living around here for the guinea pig louse, so these lice must have been carried from the original range of the guinea pig. Which is South America. These lice have been exclusively on domesticated guinea pigs for probably the last 100 years, maybe more. To the point where we could almost consider the lice to be domesticated. It occurs to me that there is a real possibility that these lice might even have adapted to the point that they couldn’t go back to living on the most likely wild ancestor of the domestic guinea pig (Cavia tschudii).

[2] One of the principles of pest control is not to depend entirely on a single pest-control method. Using multiple control methods helps to prevent resistance from developing. If we depended entirely on the selamectin, and there were a couple of resistant mites, then those survivors could quickly lead to a selamectin-resistant population that would be much harder to eradicate. But if we combine the selamectin with the mechanical louse removal, there are very good odds that we will get and eliminate any resistant stragglers, greatly increasing the likelihood that they will be wiped out entirely.

5 Responses
  1. August 19, 2012

    What a fascinating post!


  2. August 20, 2012

    Wow! What camera/lens are you using to shoot these?

  3. August 20, 2012

    Thanks, Ernie

    KT: I used a reversed 50 mm lens from my old film SLR, attached to the front of my 100 mm macro lens with a reversing ring. This makes the focusing distance of the lens shorten to about 1-2 inches, and approximately doubles the magnification of the macro lens. At the cost of making it a bear to find and focus on things.

    We have an actual microscope that showed them even better than this, but unfortunately I don’t have a good way to get a camera on it. Shooting through the eyepiece Does Not Work.

  4. August 21, 2012

    How do you reverse the lens?

  5. August 21, 2012

    You reverse the lens with one of these Macro Coupling Rings:

    This screws into the filter threads on both lenses so that the second one is on backwards. I like using this method, because then the reversed lens is essentially just a big, high-quality screw-on adapter that supplements the normal macro lens.

    There are also reversing rings, so that you can convert your DSLR’s normal lens into a macro lens by putting it on backwards:

    These are specific to particular makes of camera, and the lens becomes an inert, fully-manual hunk of glass because you lose all the electrical connections, but it is way cheaper than a dedicated macro lens. I got one of these for my Canon 10D, and experimented with it for a bit before Sandy bought me a proper 100 mm macro lens as a present. The reversing ring works, but the proper macro lens is way more convenient to use.

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