Infectious Diseases and Conditions in Dogs

Veterinarian staring at bulldog

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The health benefits of owning a dog are numerous. Studies have shown that a dog can influence social and cognitive development in children and promote an active lifestyle for the families that care for them. The catch is that you only remain happy if your dog is healthy and happy, too. Learn how to keep your canine a healthy member of your household by arming yourself with information about common infectious diseases that can affect dogs and ways to prevent dog illness.


Canine brucellosis is a highly contagious infection caused by the bacterium, Brucella canis. Infected dogs usually develop an infection of the reproductive system or a venereal infection. The disease can cause reproductive problems such as infertility, spontaneous abortions, and can spread to the intervertebral discs, the eyes, the kidneys, or the brain. This disease is more common in dogs that have not been spayed or neutered.


Coccidiosis is a parasitic infection that most commonly causes watery, mucus-type diarrhea. If it is not treated, it can damage the lining of the intestinal tract. Treatment is routine and effective. Diagnosis is made by microscopic examination of the feces. Readily available drugs eliminate the parasite to the point that the animal's immune system can clear the infection. Permanent damage to the gastrointestinal system is rare and a dog will usually suffer no long-lasting negative effects


Canine distemper is a very contagious and serious viral illness which has no cure. It can infect some wild animals such as racoons, foxes, and coyotes as well as dogs. The virus spreads through the air and by direct or indirect contact with an infected animal (such as a pet bed or water bowl). The disease first affects a dog’s tonsils and lymph nodes before attacking the respiratory, gastrointestinal, urogenital, and nervous systems.  


Ehrlichiosis is also known as "tracker dog disease," "canine hemorrhagic fever," and "tropical canine pancytopenia." Bacteria are spread by the brown dog tick and the Lone Star tick. Infected dogs may have a fever, swollen lymph nodes, weight loss, bleeding disorders, and, occasionally, neurological disturbances. Treatment includes a long course of antibiotics, usually for four weeks or so.


Although many dogs may show no symptoms, if your dog or puppy gets giardia, a protozoan commonly responsible for causing diarrhea in dogs, the stool may range from soft to watery, and occasionally contains blood and mucus. Vomiting may occur in some cases. In severely affected dogs, anorexia and weight loss may occur. If your dog is diagnosed with this disease, a antiparasitic medication may be needed to wipe it out.

Kennel Cough

Kennel cough (also known as canine infectious tracheobronchitis) is a highly contagious respiratory disease that can cause dogs to have a honking cough. This disease spreads to other dogs easily through the air, direct contact, and shared water and food bowls. It is called kennel cough because boarding and daycare facilities are known as the most popular place where this disease is spread around. It is highly treatable with an antibiotic and cough medicine to help alleviate the coughing, which can irritate the dog's trachea. It is preventable. A vaccine can be given to dogs annually to protect against the bordatella bacterium, the most common cause of kennel cough.


Leptospirosis is a bacteria that lives in water contaminated by the infected urine of wildlife, rodents, and domestic animals. It commonly leads to kidney disease but some of the strains can result in liver damage, bleeding disorders, neurologic issues, and eye inflammation. Signs of leptospirosis may include fever, shivering, muscle tenderness, reluctance to move, increased thirst, changes in the frequency or amount of urination, dehydration, vomiting, diarrhea, loss of appetite, lethargy, and jaundice (yellowing of the skin and mucous membranes). This disease can be treated with antibiotics and supportive care, however even with aggressive treatment it can be fatal in up to 20% of cases; it is preventable with a vaccine.

Lyme Disease

Though Lyme disease is one of the most common tick-transmitted diseases, only 5 to 10 percent of dogs infected with the bacterium that causes this disease show symptoms. The symptoms can include lameness, swollen joints, and fever. A small percentage of dogs can develop a severe complication in their kidneys known as Lyme nephritis. Prevalent in New England, it is believed that 10-20 percent of dogs in the Northeast have the disease but never show symptoms. Antibiotics are effective at treating the symptoms in most dogs, however once a pet is chronically infected, it is almost impossible to clear the bacteria from their system completely. In addition, antibiotics are not typically effective against Lyme nephritis which can be highly fatal. The best way to prevent the disease is to remove ticks immediately and use tick prevention products like collars and spot treatments. There is a Lyme disease vaccine.


Parvovirus typically attacks rapidly dividing cells of the intestinal tract and bone marrow. The disease is usually characterized by vomiting, foul smelling, bloody diarrhea, weight loss, and loss of appetite. Parvovirus has a high fatality rate at the damage to the intestines can result in intestinal bacteria getting into the bloodstream and causing sepsis. The incidence of parvovirus has reduced greatly with early vaccination in puppies. Since this is a virus, there is no real cure for it. The best way to help a dog recover from this is to treat the symptoms and not allow the dog to dehydrate or develop a secondary bacterial infection while sick. This usually requires aggressive in hospital treatment with intravenous fluids and antibiotics.


Rabies, contained in saliva, can be transmitted from the bite of an infected animal, most commonly found in the wild, like skunks, bats, raccoons, coyotes, and foxes. An unvaccinated dog that was bitten by a known rabid animal must be quarantined for up to six months. This virus is 100% fatal in animals once they develop symptoms. A human can also be infected by a bite from an infected animal, and possibly even a scratch if there is saliva on the animal's nails. The rabies vaccination, required in most states in the U.S., is considered highly effective in preventing the spread of rabies in the community.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.