Infectious canine hepatitis (ICH) is a viral disease caused by canine adenovirus type 1 (CAV-1). Early on it can look like parvovirus or distemper, so your veterinarian may need tests to tell them apart. It mostly affects young dogs that are unvaccinated or not fully vaccinated, though an unprotected adult can still catch it. That is why early vaccination matters, and why a puppy that has not finished its vaccines should not mix with dogs of unknown vaccination history. The infographic below gives a quick overview. If you suspect your dog might be infected, see your veterinarian as soon as possible.
What is infectious canine hepatitis?
ICH, also called Rubarth's disease, is a contagious infection of dogs. The virus targets the cells lining blood vessels and the liver, and also reaches the kidneys, spleen and lungs. The blood vessel damage is a big part of why severe cases bleed and bruise.
Despite the name, it has nothing to do with human hepatitis. It is not a dog version of hepatitis B or C, and CAV-1 does not infect people. It is also separate from chronic hepatitis in dogs, which has other causes.
How dogs catch it
Dogs pick up CAV-1 through the nose or mouth from the urine, feces or saliva of an infected dog, or from contaminated hands, bowls and clothing. The virus multiplies first in the tonsils and nearby lymph nodes, then spreads through the body.
Three things make it hard to get rid of:
- Recovered dogs keep shedding. A dog that has recovered can pass the virus in its urine for 6 months or more.
- It lasts in the environment. CAV-1 can survive outside the body for weeks or months. Steam cleaning and household bleach inactivate it; ask your veterinarian what to use.
- Wildlife carries it. Foxes, wolves, coyotes, bears, raccoons and some other wild species can be infected and may keep the virus circulating.
ICH is uncommon where dogs are routinely vaccinated, but it has not disappeared. Sporadic cases are still reported, and comebacks in Europe have been linked to puppy trading and possible wildlife spillover.
Which dogs are most at risk?
Most cases are in dogs under 1 year old with an incomplete or unknown vaccination history, but age alone does not protect a never-vaccinated adult. Take extra care with puppies from unknown sources and imported dogs, whose vaccine status may be uncertain.
Signs of infectious canine hepatitis
Signs usually appear 4-9 days after exposure. The first is often a fever over 104°F, which commonly comes in two waves. Many infected dogs probably show no signs at all; others range from a mild illness to sudden death.
Common signs include:
- fever, lethargy and poor appetite
- increased thirst
- a painful belly, vomiting and diarrhea, which may be bloody
- coughing
- inflamed tonsils and swelling of the head and neck
- bleeding problems: small bleeds on the gums or skin, bleeding around the baby teeth, bruises or blood-filled swellings
Jaundice is uncommon. Most dogs with acute ICH do not turn yellow, so a dog can have this "hepatitis" without yellow gums or eyes. Nervous system signs are also unusual.
Blue eye is the sign people remember. The clear front of the eye (the cornea) turns cloudy and bluish because it swells with fluid, which vets call corneal edema. According to the Merck Veterinary Manual, it develops in about a quarter of recovered dogs, during or shortly after the illness, and usually clears on its own. A cloudy eye can also mean uveitis or another painful eye problem, so it always needs a veterinary exam, not home treatment.
Call your veterinarian now if a puppy or unvaccinated dog has a fever with lethargy, vomiting, bloody diarrhea, bleeding gums, unexplained bruising or a suddenly cloudy eye.
How vets diagnose it
A veterinarian will suspect ICH in a young dog with a questionable vaccine history that has severe liver problems, a bleeding disorder or a cloudy cornea. Because the early signs overlap with canine distemper and parvovirus, those infections are ruled out too, and a dog can have more than one at once.
Tests your veterinarian may use include:
- bloodwork, including liver values, and clotting tests
- PCR testing, which detects the virus's genetic material
- ELISA and antibody (serologic) tests
Antibody results need care. Vaccination also produces antibodies, so a single positive result does not prove infection. A rise in antibody levels between two samples taken 2-3 weeks apart, together with matching signs, supports the diagnosis.
Treatment and outlook
No treatment targets the virus itself. Care is supportive: it treats the effects of the infection while the dog's immune system clears it. Sick dogs usually need hospital care, and your veterinarian chooses the specific treatments and doses. Supportive care can include:
- intravenous (IV) fluids
- blood or plasma transfusions for bleeding problems
- antibiotics if a secondary bacterial infection develops
- nutritional support
- comfort care for the eyes, chosen by your veterinarian
Steroid medications given by mouth or injection are not used for the corneal clouding of ICH.
Most dogs recover, but the disease can be fatal. Merck puts the death rate at 10% to 30%, highest in very young puppies, and parvovirus or distemper at the same time makes the outlook worse. Some survivors keep lasting liver or kidney damage and may need follow-up checks.
Prevention: the core vaccine
Vaccination is the reason ICH is now uncommon. Modern vaccines use a related virus, canine adenovirus type 2 (CAV-2), which protects against CAV-1. The 2022 AAHA Canine Vaccination Guidelines list CAV-2 as a core vaccine (one every dog should get) mainly for this reason, and WSAVA's global guidelines do the same.
Older vaccines used weakened CAV-1. They could cause temporary blue eye and shed virus in urine, so they were replaced by CAV-2 strains, which give strong cross-protection without causing corneal edema. CAV-2 is the adenovirus part of the combination core vaccine many owners know as DHPP.
Puppies get a series of shots because antibodies from their mother can block the vaccine in the first weeks of life. Your veterinarian sets the schedule based on your dog's age, history and risk. Until a puppy finishes the series, keep it away from dogs of unknown vaccination status and places where unknown dogs relieve themselves, and ask your veterinarian how to socialize it safely in the meantime.
CAV-2 has a second role too: it is one of the causes of kennel cough.
Summary
ICH is now uncommon in vaccinated dogs, and the core CAV-2 vaccine prevents it. If a dog, especially a puppy that is not fully vaccinated, shows fever, bleeding, vomiting or a cloudy eye, see your veterinarian right away.
Sources
- Merck Veterinary Manual: Infectious Canine Hepatitis
- AAHA: 2022 AAHA Canine Vaccination Guidelines
- WSAVA: 2024 guidelines for the vaccination of dogs and cats (Journal of Small Animal Practice)
- Cornell University Animal Health Diagnostic Center: Canine Adenovirus 1 Serum Neutralization
- Sykes JE, Canine and Feline Infectious Diseases (Elsevier): Infectious Canine Hepatitis
This article is for general information and is not a substitute for advice from your veterinarian.
