Technically, ticks and mites, two nasty little creatures that torture dogs, aren't six-legged insects at all, but eight-legged arachnids related to spiders. External parasites not only make dogs miserable but also may transmit serious diseases, some of which can be passed to people, via saliva. Some parasites are recognizable at a glance, while the presence of others can be suspected from the symptoms they cause.
The Acrobatic Flea
If you spot a bug jumping in your dog's fur, it's likely a flea. These wingless, reddish-brown insects, about the size of sesame seeds, can leap vertically as high as 8 inches and horizontally up to 14 inches. The most common external parasite affecting dogs, fleas have three pair of legs extending from the thorax, each leg ending in a claw, and their saliva can transmit diseases including typhus, bubonic plague and tapeworm. They like to congregate at the base of the ears and around the rump and groin area of dogs, leaving behind feces in the form of black specks. More than 2,000 species exist and have different scientific names, but popular names mostly reflect the host species -- dog, human, rat, hen and chigoe fleas. A dog can be infested with more than one flea species at the same time.
The Inflatable Tick
The bodies of ticks are unsegmented and, according to veterinary parasitologist Pablo Junquera of Vetparcs, a Swiss veterinary parasitology consulting firm, don't even have a proper head, only an abdomen with mouth parts sticking out one end. After sinking these mouth parts into a dog's skin, ticks stay put, gorging themselves on blood and inflating like balloons. The bodies of females, who eat the most, can bloat 50 to 100 times their prefeeding size. At that stage, they're so big -- the size of a hazelnut or larger -- that they shouldn't be difficult to see or feel. After females are so full that they can't absorb any more, they drop off the host to lay eggs. In North America, diseases transmitted by ticks include encephalitis, Lyme disease, Rocky Mountain spotted fever, anaplasmosis, babesiosis and hepatozoonosis.
Lice: Look For Evidence Close to the Skin
If you see what appear to be specks of dirt in your dog's fur close to the skin, they could be lice, although you won't be able to make out much more detail than that without a microscope. Even though these wingless insects don't transmit diseases directly, the terrible itching they cause can make dogs scratch or bite their skin raw, creating conditions ripe for secondary bacterial infections. Female lice make their whitish eggs, called nits, highly resistant to removal by attaching them to the base of hairs with a cement-like "glue" extruded from their abdomens. Lice species tend to have specific preferences for host species, so dog lice won't infest other animals or people. Dog lice fall into two broad categories, blood-sucking and chewing; a bad infestation of blood-suckers can cause anemia.
The Misery of Mites
You can't see mites with the naked eye, but you can see evidence of a bad infestation from allergic reactions and skin diseases such as scabies, also known as sarcoptic mange, as well as a few other varieties. The mites burrow into the dog's skin, digesting the proteins in it with their saliva and creating lesions so unbearably itchy that dogs will often mutilate themselves trying to find relief. The combined inflammatory effects of mites and broken skin create lesions that scab over to form crusts. When mites invade hair follicles, patchy hair loss, or alopecia, results. These injuries can easily become infected with bacteria or attract other parasites such as flies, which lay eggs in the open wounds.
Other Biting Bugs
Some other bugs that bother dogs are only too familiar to humans. Mosquitoes can inject heartworm larvae into a dog's bloodstream. When dogs rile bees, wasps, hornets, spiders and ants, they're just as apt to get stung, with the same itchy, painful consequences, as people who do the same thing. If a human household is infested with bedbugs, these flat, oval, brownish-colored insects also can colonize dog bedding and though they prefer human blood, in a pinch, they'll feed on dogs too.