Adenovirus in dogs

The two canine adenoviruses

Canine adenovirus type 1 (CAV-1) causes infectious canine hepatitis. It mainly attacks endothelial cells, the inner lining of blood vessels, as well as the liver, kidneys, spleen and lungs [1].

Canine adenovirus type 2 (CAV-2) affects the airways. It is one of the causes of kennel cough, most often together with Bordetella and canine parainfluenza virus [2].

The genomes of the two viruses are about 75% identical, and antibodies to them cross-react [5]. That is why a CAV-2 vaccine also protects against CAV-1 [3].

In Russian-language veterinary literature, the disease caused by CAV-1 is usually called infectious hepatitis, and the disease caused by CAV-2 is called "adenovirosis" [6].

How dogs get infected

The main route is nose and mouth contact with the urine, feces or saliva of a sick dog. Infection through objects is also possible [1]. Dogs that have recovered shed the virus in their urine for at least 6 months [1].

Not only dogs get CAV-1: infectious hepatitis has been described in foxes, wolves, coyotes, bears, lynxes and some pinnipeds (seals and their relatives) [1].

Symptoms of infectious canine hepatitis

The incubation period is 4–9 days. The course can be anything from a mild fever to sudden death [1].

• the first sign is usually a temperature above 40 °C (104 °F); it lasts 1–6 days and usually rises in two waves [1];
• belly pain and vomiting, including vomiting blood [1];
• conjunctivitis, eye and nose discharge, clouding of the cornea [1];
• bleeding that is hard to stop, for example around the baby teeth [1].

In about 25% of dogs that recover, the corneas of both eyes turn cloudy 7–10 days after the acute symptoms; this is "blue eye" [1]. If the dog also has parvovirus or distemper at the same time, the outlook is worse [1].

CAV-2 and kennel cough

Kennel cough, which can be caused in part by CAV-2, starts suddenly, 5–10 days after contact with other dogs. The main sign is a honking cough, like a goose, which may be followed by gagging [2].

Diagnosis and treatment

Diagnosis can use ELISA, serologic tests and PCR [1]. Treatment of infectious canine hepatitis is supportive [1]; a veterinarian decides exactly what the dog needs.

Vaccination

The World Small Animal Veterinary Association (WSAVA) classifies vaccination against canine adenovirus type 1 as a core vaccine, along with vaccines against distemper and parvovirus. These are core vaccines for dogs in every country [4].

• puppies get their first dose at 6–8 weeks [4];
• then every 2–4 weeks until the puppy is 16 weeks old or older [4];
• an extra dose at 26 weeks or a little later [4];
• after that, revaccination no more often than once every 3 years [4].

Dogs are vaccinated with a canine adenovirus type 2 vaccine: it also protects against CAV-1, that is, against infectious canine hepatitis [3]. Older CAV-1 vaccines caused corneal clouding and kidney damage and are now rarely used [3] [1]. For example, the Russian combination vaccine Multican-4 contains a strain of canine adenovirus type 2 [7]. A veterinarian sets the schedule for each individual dog.

Is canine adenovirus dangerous to humans

No. Canine adenoviruses type 1 and type 2 are not considered zoonotic, meaning they are not dangerous to humans [3]. Human and canine adenoviruses belong to the same genus but to different species [8].

A 2019 systematic review found isolated evidence of cross-species transmission of adenoviruses, including some involving dogs, but this is not evidence of people getting sick from canine adenoviruses [9].

How to disinfect your home and kennel

CAV-1 is hardy in the environment and survives outside the body for weeks to months. It is killed by steam cleaning or a 1–3% sodium hypochlorite solution, that is, household bleach [1].