Common Diseases and Symptoms in Dogs

Old purebred blind jack russell dog with cataracts in eyes

Dog owners must know that canines are susceptible to a variety of common diseases. Some are treatable and others are preventable. Recognizing the symptoms of an illness helps ensure that your pet receives medical intervention as soon as possible, which increases the chances of recovery.


Not unlike how the disease process affects people, dogs may develop different types of cancer. Some types form localized tumors and others are more likely to spread or metastasize throughout the body. Different veterinarians may also have varied views concerning treatment options. While the reason cancer occurs remains unknown, genetic and environmental factors may contribute to malignancy development. Cancer symptoms include:

  • Lumps or unusual swelling
  • Sores that do not heal
  • Abnormal discharge from any body region
  • Persistent bad breath
  • Generalized unexplained fatigue
  • Unexplained weight loss
  • Difficulty breathing, having bowel movements or urinating
  • Black, tarry-looking bowel movements
  • Lameness in the absence of injury

Diagnosing cancer may involve a needle biopsy performed on abnormal growths to examine the cells under the microscope. Blood tests and imaging studies are also commonly used. Treatment may involve surgical removal of the malignant growth, chemotherapy, radiation or a combination of therapies.

Cancer may occur in any dog species at any age. However, older dogs and certain breeds are more susceptible. Boston terriers, boxers and golden retrievers are more prone to mast cell tumors or lymphomas. Large and giant breeds, which include great Danes and saint bernards are more prone to developing bone cancer.

Neutering male and female dogs at an early age is one way to dramatically reduce the chances of pets developing cancer in later years.


Similar to humans, dogs develop diabetes when the body becomes insulin resistant or the pancreas does not produce sufficient amounts of insulin. Without insulin, sugar cannot nourish cells and remains in the blood. If left untreated, hyperglycemia causes many different health problems. Although an exact cause is unknown, autoimmune disorders, genetics, medications, obesity and pancreatitis are thought to contribute to the development of the disease. Symptoms of diabetes include:

  • Increased appetite
  • Increased water consumption
  • Vomiting
  • Weight loss
  • Increased urination
  • Dehydration
  • Unusual fatigue
  • Sweet-smelling breath
  • Cataract formation
  • Skin problems that do not heal
  • Frequent urinary tract infections

Females and obese dogs have a greater risk of developing diabetes. The disorder is typically diagnosed when the animal is between six and nine years of age. Certain breeds also seem to carry a greater risk. These dogs include Australian terriers, dachshunds, keeshounds, miniature and standard-sized poodles and samoyeds. Juvenile diabetes is not uncommon in golden retrievers and keeshounds.

Diagnosing the disease process involves evaluating symptoms, performing a physical examination and evaluating blood and urine samples. Treatment is determined based on the severity of the disease and other possible health problems. Some dogs merely require oral medications or dietary changes. Some need routine insulin injections. Seriously ill dogs require hospitalization to monitor and lower their blood sugar.


The disease is caused by a parasitic worm that travels through the bloodstream while damaging blood vessels, which eventually infects the heart, lungs, kidneys and liver. Complete infestation typically takes six months after the initial exposure. The parasite is transmitted by mosquitoes. The animal must become infected with a male and female worm before parasitic reproduction occurs. If not detected, over the course of five to seven years, the dog may be infested with hundreds of worms. When not caught in time, the disease causes death. Symptoms of heartworm include:

  • Difficulty breathing
  • Coughing
  • Nausea and vomiting
  • Weight loss
  • Fatigue after little physical activity
  • Some dogs may not have symptoms until latter stages

Diagnosis involves a physical examination, imaging studies and a blood test. Dogs should undergo blood testing every spring before receiving a preventative prescription. Treating an infected dog involves a series of injections with adulticides. Although the medication has a high cure rate, dogs must be monitored and kept calm during the process in order to prevent further cardiovascular damage.

Animals living in hot, humid climates are at greater risk of becoming infected. However, infections have been recorded in every U.S. state with the exception of Alaska.

Kennel Cough

The generic phrase refers to bacterial, fungal or viral respiratory infections, which cause inflammation throughout the animal’s throat and may venture downward to cause bronchitis. The affliction is not unlike a chest cold that affects people. Depending on the underlying cause, the infection often resolves without treatment. However, it is extremely contagious to other dogs. Kennel cough symptoms include:

  • Chronic, dry, honking cough
  • Gagging
  • Coughing foamy, white phlegm
  • Nasal congestion and discharge
  • Fever

The infection occurs in many different ways. Dogs may inhale microbes from the air. They might become infected after coming in contact with an ill dog or contaminated objects. Animal shelters, kennels, and other enclosed environments having poor air circulation are breeding grounds for microbes. Very young dogs and any dog not vaccinated against Bordetella and parainfluenza are at greater risk. If not treated, the infection could lead to pneumonia.

Infected dogs must be isolated from others. Humidifiers, vaporizers or other steam-producing environments help open breathing passages. Veterinarians may prescribe cough supressants and antimicrobial medications. Ensure the animal continues eating and drinking. Eliminate stress and over active behavior.