A good diet and plenty of exercise are important to a dog's health, but they can't make a dog totally immune to illness. Early detection is the key to helping your dog overcome any health problem. If your pet's stools become very loose, or you notice a marked decrease in your dog's appetite and/or that she is very lethargic, she may just have a short-term "bug." On the other hand, if any symptoms continue for more than a few days, you should have your veterinarian examine her for parasites and infections.

Diarrhea is a common symptom in dogs, especially puppies. It can be triggered by stress or a sudden change in food, but also by a virus, bacteria or parasites. Diarrhea causes dehydration, which can be deadly to dogs. It is extremely dangerous in puppies, because they dehydrate faster than mature dogs. If your dog has diarrhea for more than a day, contact your veterinarian for further instructions. You will probably be asked to collect a sample and bring it in so they can examine it to determine the cause and proper treatment.

Coughing, sneezing, and discharge from your dog's nose and/or eyes often indicate a respiratory infection. A lethargic dog with no appetite is likely fighting an Upper Respiratory Infection (URI). URI, caused by airborne viruses and bacteria, is highly contagious among dogs, but is not transmitted between dogs and humans. Early detection of URI is important; ignored dogs suffer from severe dehydration and risk developing pneumonia. Bortadella, also called 'kennel cough" is another contagious respiratory disease commonly contracted in animal shelters, boarding kennels, or anywhere groups of dogs have close contact with one another. It is a short-term disease, and most dogs get over it with a few days of rest and tender loving care from you. It is possible to have your dog vaccinated against Bortadella-a good idea if you plan on boarding her or placing her in "doggie daycare."

Vaccinations are also available to protect your dog against more deadly diseases such as rabies, distemper and parvovirus. Most municipalities require that all dogs are vaccinated against rabies; some include distemper and parvovirus as well. Making these vaccinations mandatory protects the health of all dogs, and, in the case of rabies, human health as well. If your dog was vaccinated as a puppy, she's off to a good start. However, without yearly booster shots, your dog is at risk of great suffering from one of these diseases.

Dogs serve as hosts to a number of parasites. You will probably be asked to bring a fecal sample to your dog's yearly vet appointment, so that the staff can check for the presence of internal parasites. If you notice small, rice-like granules on your pet's bedding or around her anus, she is suffering from an infestation of worms and needs to be seen by your vet to get proper treatment.

Other parasites take up residence on the outside of your dog's body. Mange and sarcoptic mites live on the hair follicles and skin of dogs, while ear mites live on the inside of the ear. These parasites are so small you might not see them, but they cause your dog extreme discomfort. Head shaking and pawing at ears are signs of ear mites. Frequent scratching and skin-biting can indicate either skin mites or a dog's worst enemy-fleas.