Mites and Lice
Mites are a group of small parasites that may attack dogs. There are three main mites that might be found on dogs: the ear mite, Otodectes; the sarcoptic mange mite, Sarcoptes; and the demodectic or red mange mite, Demodex. Skin problems caused by mites are often referred to as mange. Demodex is not contagious, though ear mites and sarcoptic mites are. They will spread among dogs, from cats to dogs, and (rarely) even to people! If one pet in your household is found to have mites, it is a good idea to check them all carefully. Lice are also parasites that attack dogs via their skin, though they aren't very common in dogs.
Ear mites tend to be found in dogs that live with cats. You might notice dark, coffee-ground type buildup in your dog's ears, and she may be scratching a bit. Your veterinarian can diagnose a mite infestation by examining a swab of the discharge under a microscope. Most cases can be treated with topical ear medications, though severe cases may need a parasiticide.
A dog with sarcoptic mange is usually very unhappy and uncomfortable. These mites burrow into the top layers of the skin, where even a few of them can stimulate a very strong itch response. Dogs with sarcoptic mange can barely walk, as they keep stopping to scratch. With all the scratching, they have open skin areas, which are then in danger of infection. Sarcoptic mange mites are contagious, and dogs with these parasites often have picked them up from local wildlife, including foxes and squirrels.
Diagnosing sarcoptic mange can be tricky. Skin scrapes are the best method, but it can be hard to find mites. If your veterinarian suspects sarcoptic mange, he may start treatment even with a negative skin scrape.
Skin scrapes are used to diagnose cases of mange. Your veterinarian will choose a couple itchy areas of skin and pucker it to scratch a sharp blade across the top. The thin skin layers are then examined under a microscope. It may take many skin scrapes to find a sarcoptic mite, but Demodex are usually easy to find.
Sarcoptic mange is often treated with a combination of drugs along with baths or dips. Any related infections must also be treated, and your veterinarian will try to make your dog comfortable and relieve some of the itching.
Demodex — Mite of the Red Mange
Demodex is a tiny mite that can be found in normal dogs. Most dogs get along quite well with their demodectic mites and have no problems. Unfortunately, some dogs have immune problems that are either temporary, as may be seen in puppies or debilitated dogs, or permanent from immune defects. In these dogs, the mites overgrow and cause skin reactions. A few red spots on a puppy may be treated topically or may clear by themselves with no treatment. Dogs that have more than five spots or large areas of reddened, sore skin have generalized Demodex. As mentioned, this is a marker for immune problems.
Demodex is usually easily diagnosed by a skin scraping. Dogs with generalized Demodex will need serious treatment, often with both drugs and dips combined. Since this condition is associated with a genetic defect, dogs that suffer from it should be spayed or neutered and not bred.
Cheyletiella — Walking Dandruff
Cheyletiella is a short-lived mite most often seen on puppies. It shows up as a line of dandruff down their backs. This mite is not usually a serious threat to your dog's health and can be treated by medicated baths.
Lice come in two main types — biting and sucking. Biting lice tend to be smaller and can move quickly. Lice tend to be host-specific, which means they rarely move from people to dogs or vice versa. Neither type is very common in dogs. Puppies may sometimes have lice from a dirty environment and may spread to them from their mother. A large number of lice could make a puppy anemic, but normally the effects are just poor coats and nits or eggs attached to hair shafts. In most cases, medicated baths or dips will take care of this parasite.