Common Dog Diseases and Health Problems

Dog Health


by Dr. Duane Rice and Dr. Diana Longfellow

Whether your dog is a working companion, champion show animal, hunting partner, or just a best friend, the kindest and most responsible thing you can do for him is to provide proper health care. Knowing about common dog diseases and being aware of appropriate prevention and treatment can better help you provide that care.

Many Diseases Can Be Prevented

Some of the most common and serious dog diseases have been made less common through vaccines; however, these diseases continue to threaten a dog that lacks proper immunization. Puppies may be vaccinated as early as 4-6 weeks, depending on each situation and the veterinarian’s advice. Through mother’s milk, puppies receive disease-fighting antibodies, which last 6-16 weeks. Vaccinations then take over. Yearly boosters should be given throughout your dog’s life, including old age when your dog may become more susceptible to some diseases.

The following diseases can be prevented through vaccinations:
Distemper. Canine distemper is caused by a highly contagious, airborne virus. It affects the dog’s respiratory, gastrointestinal, and nervous systems. Early symptoms are those of a “cold” — runny eyes and nose, fever, cough, and often diarrhea. Later in the course of disease there may be nervous twitching, paralysis, and seizures (convulsions). There is no successful treatment.
Hepatitis (Adenovirus). Canine infectious hepatitis is a viral disease transmitted by urine, feces, or saliva of infected animals. It affects the liver, kidney, and blood vessels. The signs are fever, tissue swelling, and hemorrhage. Treatment may require blood transfusions and intensive care; often it is not successful.
Leptospirosis. Canine leptospirosis is caused by bacteria spread through contact with nasal secretions, urine, or saliva of infected animals. The disease also can infect humans. Lepto infects the kidneys and causes fever, vomiting, diarrhea, and jaundice. Treatment requires antibiotics, intensive care, and intravenous (IV) fluid therapy. Dogs that recover may be left with permanent kidney damage.
Kennel Cough. Canine infectious tracheobronchitis is caused by several viruses (including parainfluenza) and bacteria (including bordetella). This highly contagious disease attacks the respiratory system, causing a chronic, dry, hacking cough. It is generally a mild infection, but it may progress to severe pneumonia in young pups or old dogs. Treatment can be helpful.
Parvo. Canine parvovirus is a deadly contagious viral disease that is spread by contact with infected fecal material. The virus is difficult to kill and is easily spread. It attacks the gastrointestinal system, causing fever, lethargy, vomiting, bloody diarrhea, and rapid dehydration. Treatment requires intensive IV fluid and supportive therapy and has a variable rate of success.
Corona. Canine coronavirus is a highly contagious viral infection attacking the gastrointestinal tract. Signs are similar to parvovirus infection, except it is generally milder and more effectively treated.
Rabies. Rabies is a viral infection of all mammals, including man. It is transmitted by the bite of an infected animal. The virus infects the central nervous system, causing a brain infection (encephalitis), which is always fatal. There is no treatment for dog or man after symptoms appear. However, a vaccine is effective in preventing the disease in people if it is administered soon after their possible exposure. Because of the serious public health threat, Indiana law requires a rabies vaccination for all dogs.

Internal Parasites

The most common internal intestinal parasites are tapeworms and roundworms.
Tapeworms. Tapeworms are long, segmented worms. They are transmitted when a dog ingests a larval stage of the worm found in a flea or the raw meat of small mammals. A dog that hunts on its own or has had fleas will likely develop tapeworms. Individual tapeworm segments are easily seen in freshly passed feces or around the anus of an infected dog. Special dewormers are required for treatment.
Roundworms. The roundworm classification encompasses many worm types, including ascarids, hookworms, whipworms, and heartworms. The intestinal worms are transmitted by the ingestion of feces or feces-contaminated soil that contains worm eggs. The transmission of the heartworm, however, requires an intermediate host such as a mosquito for propagation. Your veterinarian will perform a specialized microscopic examination of feces (for intestinal worms) or blood (for heartworms) to determine the presence of roundworms. Treatment or prevention with medication is effective, but it should be repeated regularly and monitored to determine if reinfection has occurred. Deworm a dog with a veterinarian’s supervision.
The following describes in more detail the four types of roundworms mentioned above.
Ascarids are long, thin spaghetti-like worms that inhabit the intestine. Some types of these worms can be seen in an infected dog’s feces. These worms commonly create a problem in pups, where they cause stunted growth, lethargy, diarrhea, vomiting, and a pot-bellied appearance. In severe cases, ascarids can cause seizures (convulsions).
Hookworms are tiny worms that attach themselves to the intestinal wall and suck blood from the dog. They can be transmitted in utero and via the mother’s milk to newborn pups. Consequently, pups may have hookworms at a very early age. Signs of infection include lethargy, stunted growth, anemia, and dark, tarry feces. Hookworms are a life-threatening parasite at any age. Blood transfusions may be necessary in advanced cases.
Whipworms are tiny worms that inhabit and develop in the lower bowel. They often cause chronic watery diarrhea and weight loss. Their life cycle is longer than most intestinal parasites, and proper timing of repeated deworming is important for their control.
Heartworms are devastating internal parasites that live in a dog’s heart and in the big vessels near the heart, where they cause severe damage to the circulatory system and lungs. They are transmitted by the bite of a mosquito that has bitten an infected dog. Treatment is difficult, but preventive measures are available. Dogs should have a blood test for heartworms in early spring before mosquito season begins. If the test is positive, treatment may be attempted. If the test is negative, preventive medication can be given to your dog daily or on a monthly basis throughout the mosquito season. Consult with your veterinarian to determine the best heartworm prevention plan for your dog.

External Parasites

External parasites are “bugs” (insects) that live on the outside of a dog’s body. They include fleas, ticks, lice, flies, mosquitoes, mites, and others. They not only cause irritation, but also may transmit diseases and cause disease in humans. Careful skin examination by a veterinarian can detect these parasites.

Fleas are readily seen in a dog’s haircoat. They are pencil-lead size, brown, compressed side to side and seem to be in constant motion. They are seen most easily at the base of the tail, between the ears, or in the short hair on the abdomen. Even if the flea is not visible, black specks of excrement may be seen. Many treatments are available; however, the dog’s environment must be treated just as vigorously, since the flea actually spends more time off the dog than on. Flea control should be implemented at the earliest sign of flea infestation because fleas multiply rapidly and a small problem becomes a major one in just a few days. While most dogs scratch with fleas, some dogs are also allergic to flea saliva. For them, one flea bite can set off an allergic reaction of severe skin inflammation. A flea-allergic dog will require medication to relieve the skin inflammation in addition to flea control.

Ticks are most prevalent in early spring and are most commonly found on outdoor dogs that get into underbrush and wooded areas. Ticks can transmit several diseases (including Rocky Mountain Spotted Fever) and should be removed with care. Grasp the tick near its head with a pair of tweezers and pull away from the skin with a firm tug. Do not try to kill the tick first with fire or chemicals. Disinfect the area with alcohol to prevent infection. Ticks should be controlled by daily inspection and removal or, in heavy infestations, by the regular use of chemical dips.

Lice are small, light-colored parasites that are transmitted dog to dog. They can be seen at the base of the hair. Signs of lice infestation (pediculosis) are a rough and dry haircoat, matted hair, and scratching and biting of the skin. Lice are effectively treated with a variety of chemicals available from a veterinarian.
Mange mites cause two types of mange in dogs. Sarcoptic mange is caused by the sarcoptic mite, a microscopic parasite similar to a chigger. These mites are transmitted from dog to dog and can also infect human skin. They burrow into the skin and cause severe itching and consequent skin irritation and inflammation. Hair loss can be severe and generalized over the body. Diagnosis by a veterinarian is essential, and treatment is usually quite effective. All animals in contact with the infected dog should be treated at the same time.

Demodectic mange is caused by demodectic mites that destroy the hair follicle in which they reside. This causes small patches of hair loss that can spread to the entire body. The initial skin lesions may become infected and are difficult to treat. The tendency to develop demodectic mange is thought to be hereditary. It is seen most frequently in purebred dogs. Demodectic mange is not contagious. Diagnosis and treatment by a veterinarian are necessary; treatment is difficult.
Ear mites tunnel in the skin of the outer ear canal. They are easily transmitted from dog to dog or cat to dog. They can be seen in the ear with magnification. Ear mites are suspected when dark coffee-ground debris is present in the ears. Infestation signs are head shaking and scratching at the ears. Left untreated, ear mites predispose the ear to secondary bacterial infection. Treatment requires cleaning of the ear by a veterinarian and use of mite-killing insecticide. Be sure to treat any other cats or dogs in the household.

Other Common Problems

Ear infections are a common problem in dogs, especially those breeds with a heavy earflap. Infections are caused by bacteria or yeast that grow in the ear when the ear’s normal environment is changed for any reason. Ear mites, ticks, and water or grass awns in the ear can be predisposing factors. (Grass awns are slender, bristlelike appendages on the tips of many grasses. Dogs can get them in their ears as they run through fields.)
Signs of ear infections are head shaking, pawing or digging at the ear, pain, redness, and inflammation of the ear canal, and a foul smell in the ear. Any ear infection should be examined by a veterinarian for proper treatment. To prevent ear problems:

  • Examine your dogs ears at least once weekly
  • Try to prevent water from getting in your dog’s ears when bathing the dog
  • Ask a veterinarian for advice on wax control and routine ear cleaning.

Dental problems arise frequently and need attention. Drooling and/or foul odors coming from the mouth are signals. Regular veterinary advice and maintenance programs are necessary to prevent this disorder.

Dog anal sac problems also occur, causing considerable animal discomfort. Anal glands may become infected, causing drainage and foul odors at times. The dog may exhibit uneasy behavior such as rear-end scooting or nipping at the tail area. A simple procedure may relieve the animal; in severe cases, antibiotic treatment or surgical intervention is necessary.

Regular visits to the veterinarian are important to prevent or correct serious health problems. To provide proper care and comfort for your dog, be aware of potentially serious situations and take preventative measures.


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