Nobody wants to see lice on their pet, any more than they do on their kids. Lice cause intense itching and scratching, and can make pets a bit crazy with all the crawling and biting. The good thing is that lice seldom cause long-lasting problems.

Like human head lice, dog lice are usually transmitted in situations where dogs are gathered together. In this respect, lice infestations are a sign of a pampered pet! The dogs most likely to get lice are those who go to dog day care, puppy classes, agility, dog shows, or on group walks. The lice move straight from dog to dog by direct contact.

There are two general groups of lice that infest dogs and cats - biting lice and sucking lice. They differ only in how they feed. All lice have powerful claws on all 6 legs, with which they cling to the hair shafts. They are able to hang on tightly enough that even vigorous scratching and biting will not dislodge them.

Unlike fleas, lice live out their entire life cycle on the animal. The adult female lice lay eggs, gluing them tightly to the hair shafts. The eggs are referred to as "nits". In the photo to the left you can see two nits from a dog seen at our clinic. The eggs are actually glued on to the hairs. One has hatched (the empty shell) and one is going to soon (the brown egg). Nymphs hatch from the eggs. These nymphs look the same as adults to the naked eye; they are just smaller versions. They molt several times and become adults. The entire process from egg to adult takes 2-4 weeks.

The biggest problem that the lice create is itching and its attendant loss of sleep and general misery. In severe infestations animals can become anemic due to blood loss; this is generally only seen in young puppies or kittens. Lice can carry tapeworms, so infested dogs should be treated for tapeworms once the lice are under control. They can also (fairly rarely) transmit other diseases.

Clinical signs

The first sign of lice that most people notice is the scratching. Suddenly the dog is intensely itchy. Upon close inspection, you might see some small, tan to medium brown colored critters down near the skin. You can tell lice from fleas by the color (fleas are quite dark) and the speed (lice are quite sluggish movers, while fleas usually zoom out of sight before you are really sure you saw anything).

You might also notice the nits on the hairs. They are quite difficult to see with the naked eye. The empty shells look most like little bits of dandruff or dead skin. One way to tell is to use a flea comb to collect hair from the area you are suspicious of. If you can shake the hair and the 'flakes' fall off onto the countertop, it's just dandruff or debris. If the 'flakes' stick tight to the hair, they may be nits.

Dog lice on people

There is no need to panic if your dog gets lice! Dog lice do not like to infest humans. Most lice are quite species-specific; that is, dog lice like dogs and people lice like people. It is definitely possible for a dog louse to get on a person, and it might even bite or try to feed, but it will not set up an infestation. If you see a louse from your dog on yourself, just pick it off or squish it (once you've finished screaming).

Treatment of all in-contact pets

Treatment of lice is relatively straightforward. Many insecticides kill lice. Most flea shampoos contain pyrethrins or organophosphates and do a good job of getting rid of louse infestations. Topical insecticides like imidacloprid (Advantage) applied topically every 2 weeks will also kill lice. Selamectin (Revolution), while not labeled specifically for lice, may also be effective. Permethrins (different from pyrethrins) are also effective insecticides but due to the potential for accidental toxicity to cats, I rarely recommend using permethrins for dogs.

Use extreme caution when applying permethrin-containing products to dogs with cats in the home.

Permethrins are very toxic to cats, and can get onto the cat from contact with the dog. 

Never, ever apply permethrins to cats - read all packaging carefully!
 

You have to keep in mind two things. First, that nothing will "kill" the eggs. No insecticides will penetrate the shell of the egg and zap the growing nymph. And second, most insecticides (there are some exceptions) do not have much "forward" effect. That is, they don't last very long on the dog's coat and skin.

If you bathe the dog once, or apply one treatment of Revolution, you will kill the adults and nymphs. In a week or two, though, the nits will hatch and you will have a whole new generation of lice. Unless you have used a persistent insecticide (like Advantage) there is nothing left on the dog to kill this new generation.

This brings us to the various recommendations for treating lice, and you can now appreciate the logic behind them. In order to get rid of the lice on your dog effectively and permanently, you will need to reapply insecticide on a routine basis for at least 4 weeks. All animals in the household should be treated whether you have seen lice on them or not.

Any of the following should be effective at ridding your poor beleaguered pet of lice. There is no need to use more than one kind of treatment.

1. Advantage or Advantage Multi topical, applied every 2 weeks for a total of 3 treatments. That is, applied when the problem is first seen, then again 2 weeks later, and 2 weeks after that. The label on Advantage calls for re-application every 4 weeks. The "problem" with this (for lice) is that the Advantage does tend to wear off and become less potent over that 4 week period. It is safe to re-apply it after 2 weeks, and you will be keeping the concentration of Advantage nice and high in order to zap the newly hatched lice as soon as they emerge.

2. Insecticidal shampoos once a week for 4-6 weeks. A good flea shampoo containing pyrethrins or organophosphates will work very well. Make sure that you follow the directions on the label regarding contact times. Most insecticides should be left on the coat for a 5-10 minute period in order for them to kill the lice. Each product will state on the label how long to leave the shampoo before rinsing it off. If you rinse too soon it will not be as effective.

3. Revolution, applied every 2 weeks for 3 treatments.

4. For those who do not want to use insecticides, lime-sulfur dips are extremely safe, non-toxic to pets (we used to use it on tiny kittens to treat ringworm) and very effective. They have the disadvantage of staining the coat yellow (temporarily) and having a somewhat objectionable odor (sulfur). They should be repeated weekly for 4-6 weeks.

5. Flea combs will help to remove both living and dead lice. Clean the comb afterward by immersing it in a container of water with some flea shampoo or other insecticide and letting it sit for at least 10 minutes, or until you don't get the heebie-jeebies touching it, whichever is longer.

Environmental decontamination

Wash all bedding in hot water. I would dispose of all combs and brushes or other grooming equipment, as they may have nits stuck to them that will be hard to remove. They will also be hard to see you may never know whether the combs are really nit-free. It's better to just chuck the lot and start over again with clean instruments.

Everything else that your pet is in contact with is also fair game for a hot water wash, from doggie sweaters and other clothing to leashes and collars to kids. (Mostly kidding about the kids, but any excuse for a bath is a good thing.)

Quarantine

During treatment for lice your pets should be kept away from situations where they will be in contact with other animals. They can go to the parks and for walks, but they should not play with other dogs until at least 4 weeks of treatment have passed. They should especially not go to dog daycare or other high contact places. While the insecticides may have killed the adults on your pet, you never know when those pesky eggs are going to hatch and release more nymphs, which are definitely contagious to the next dog.