A creature that lives off another animal is a parasite. They can feast on skin and blood or leach on inside, eating your dog's leftovers. If your dog itches one spot too much and starts to pull her hair out, she may get a hot spot (acute pyotraumatic dermatitis that is not due to a single underlying cause ). Go to the doctor immediately.

External

Fleas, lice, and mites are the most common external parasites found on the dog.

Fleas

Fleas do not transmit disease from dog to another dog or from dog to human. But they are a pest that causes annoyance not just to the dog but the human companion and cat too. Its important to understand that defleaing just the dog is not sufficient to cure your flea situation. The flea lays its eggs in bedding grass, the dog's favorite piece of furniture, carpeting, and in your car, basically anywhere the dog goes.

The flea lays hundreds, possibly thousands of eggs and these eggs hatch in about 8-10 days. It is; therefore, important to deflea all these areas at the same time you deflea the dog.

There are excellent products on the market that can halt the eggs from hatching and many of these products are very long lasting. There are new products that need be applied only once monthly to the dog. The liquid is applied in one place on the dog's back and kills the flea eggs. Excellent results are being reported. It is only available through your vet.

The yard must be treated and there are biodegradable and non-toxic products that work well. Check with your veterinarian as well as your local pet shop. This process must be started in early spring in some parts of the U.S. and continued until fall.

Lice

The lice that are found on dogs are not the same lice found on humans. There is no threat from dog lice, as it is not interested in human blood. There are many varieties of lice, mostly all are specific to humans. The specific dog lice are Linognathus setosus and L. piliferus. Linognathus refers to the structure of the mouth; setosus refers to bristles and piliferus to hair.

Mice

The three types of mites found on dogs are:

• Otodectes which is an ear mite,
• Sarcoptic Mange which causes severe itching, thickening skin and odor, and
• Follicular Mange which lives in the hair follicles and causes the hair to fall out, the skin to redden and eventually forms postules. You should always consult your veterinarian for diagnosis and treatment.

Ticks

Ticks are most often found in wooded areas and beaches. These need to be removed from the dog by using tweezers or paper making sure to wear gloves as the ticks blood can contain organisms which can infect humans with dangerous disease.

Internal

Internal parasites are worms.

Roundworms

The common roundworm is found most often in puppies where they hatch in the intestines. If it is treated when the dog is young, rarely will a heavy infestation be found when the dog is older. These worms may be passed on occasion through the stool and look like thin spaghetti about 1-3 inches longs, whites, firm and sometimes coiled or curled.

Hookworms

Hookworms are also common in puppies but a dog of any age can be infected. This worm in a heavy infestation can cause death and it will usually attack a weak, sickly animal. Things to look for are weakness, anemia, and thin, mucous-like diarrhea possibly with blood. Call your vet if you see these symptoms.

Whipworms

Whipworms respond well to oral medicine. Symptoms may be on and off diarrhea, poor condition and the coat may seem dry and brittle.

Tapeworms

Tapeworms are often found in the older dog. There are two species of this worm. One spends part of its cycle in the flea. When your dog eats a flea it becomes infected. The other spends part of its cycle in the rabbit or mouse. When the dog gets hold of and eats one of these animals it also becomes infected.

This worm attaches itself to the lining in the intestines and some segments will break off and come out with the stool. It is usually easy to identify this worm and a stool sample can be taken to your vet for confirmation. Oral medicine is very effective for this worm but only lasts on a temporary basis. Once a flea, rabbit, or mouse is ingested medicine is again required.

Coccidia

Coccidia lay their eggs in stools. Dogs become infected by eating other dogs stools. They are not from the worm family. They are protozoans that line the intestinal track causing loose, watery stools, bloating, vomiting and weight loss. Treatment is quick and easy.

Giardia

Another protozoan, these water-loving creatures are found in most outdoor water sources and once ingested, they feast on the inner lining of the small intestine. This creates inflammation leading to loose stools, bloating and weight loss.

Dogs pick this up by drinking infected water or digesting the stools of other infected dogs so bring fresh water for your dog if you are picnicking by a pond. Treatment involves the use of a drug that can have side-effects over long-term use.