Canine adenovirus type 1, or CAV-1, is a contagious virus belonging to the Adenoviridae family. It is known to infect canids, a group that includes domestic dogs, wolves, coyotes, and foxes. The virus is the specific cause of a systemic disease that can have serious health consequences for these animals. Although widespread vaccination programs have made the disease less frequent, CAV-1 continues to pose a threat, particularly to puppies and unvaccinated dogs who lack immunity.
The Disease Caused by the Virus
Infection with canine adenovirus type 1 leads to a disease known as Infectious Canine Hepatitis (ICH). The virus has a primary affinity for the liver, kidneys, and the endothelial cells that line the interior of blood vessels. This targeting of tissues leads to the wide spectrum of clinical signs observed in affected dogs, ranging from very mild to life-threatening. The severity of the illness often depends on the age and immune status of the dog.
Initial symptoms of ICH can be subtle, often starting with a fever, lethargy, and a decreased appetite. As the virus multiplies and spreads through the bloodstream, more severe signs may develop. These can include significant abdominal pain due to an enlarged liver, vomiting, and diarrhea. Damage to the blood vessels can impair clotting, leading to spontaneous bruising or bleeding from the mouth and nose.
In about 20% of dogs that recover from the acute phase of the illness, a condition called corneal edema, or “hepatitis blue eye,” can appear. This results from the body’s own immune response to viral particles within the eye, causing the cornea to become swollen and take on a cloudy, bluish appearance. In the most severe cases of ICH, extensive liver necrosis can lead to organ failure and death.
Transmission and Spread
The primary route of transmission for canine adenovirus type 1 is through direct or indirect contact with the bodily fluids of an infected dog. The virus is present in the saliva, feces, and urine of sick animals. Infection occurs when a susceptible dog ingests or inhales viral particles, which then replicate first in the tonsils before spreading throughout the body. Contaminated objects like food bowls, toys, and bedding can also serve as sources of infection.
A significant factor in the spread of CAV-1 is the prolonged period during which a recovered dog can shed the virus. Even after symptoms resolve, a dog can pass the virus in its urine for six to nine months, meaning seemingly healthy animals can infect other non-immune dogs.
The virus is resilient and can survive outside a host for weeks or months, which increases the risk of indirect transmission from contaminated areas. Disinfection with appropriate cleaning agents is necessary to eliminate the virus from surfaces in kennels, parks, and homes.
Diagnosis and Treatment
A veterinarian diagnoses Infectious Canine Hepatitis based on a combination of the dog’s clinical signs, a history of potential exposure, and specific laboratory tests. These tests often reveal abnormalities consistent with liver damage, such as elevated liver enzymes (ALT and AST), and issues with blood clotting, indicated by a prolonged prothrombin time. A low white blood cell count, known as leukopenia, is also a common finding during the febrile stage of the illness.
There is no specific antiviral medication that can cure a CAV-1 infection. Therefore, treatment is centered on intensive supportive care to manage symptoms and help the dog’s body fight the virus. This care is tailored to the individual patient’s needs but frequently involves hospitalization for intravenous fluids to correct dehydration and maintain electrolyte balance.
Nutritional support is provided for dogs that are not eating, and medications may be administered to control symptoms like vomiting. In cases where blood clotting is severely affected, blood transfusions may be necessary to prevent life-threatening hemorrhage. Because the virus can weaken the immune system, antibiotics are sometimes used to prevent or treat secondary bacterial infections that can complicate the disease.
Prevention Through Vaccination
Vaccination is the most effective method for preventing Infectious Canine Hepatitis. The vaccine for this disease is considered a core vaccine, meaning it is recommended for all dogs regardless of their lifestyle or location. Puppy vaccination series typically begin when they are between six and eight weeks of age, followed by booster shots to ensure a robust and lasting immune response.
The vaccine most commonly used today is not for canine adenovirus type 1, but for canine adenovirus type 2 (CAV-2). CAV-2 is a related virus that is a cause of respiratory disease, or “kennel cough,” in dogs. Veterinarians switched to the CAV-2 vaccine because it provides excellent cross-protection against CAV-1 without the risk of certain side effects associated with the original CAV-1 vaccine.
The older, modified-live CAV-1 vaccines were effective but could sometimes cause the development of “blue eye” (corneal edema) and kidney inflammation as a post-vaccinal reaction. The modern CAV-2 vaccine immunizes a dog against Infectious Canine Hepatitis while avoiding these complications, and regular booster vaccinations are important to maintain this protection.