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Viruses:
Infectious
Canine Hepatitis, CAV-1 |
| Infectious
Canine Hepatitis affects (but is not limited to) the following:
- Liver
- Kidneys
- Eyes
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An
Overview of Infectious Canine Hepatitis
Infectious
Canine Hepatitis (ICH) is caused by canine adenovirus type-1 (CAV-1),
a pathogen
closely related to yet distinct and very different from canine adenovirus
type-2 (CAV-2) with a long and varied history. ICH was first documented
in the silver fox in 1925, but the disease did not appear in domestic
dogs until the 1930s and 1940s. It wasn’t until two decades after
that, in 1962, that the disease-causing virus was thoroughly researched
and classified.
Thanks
to the extensive availability of effective vaccines, CAV-1 triggered
ICH is much less common today, but young dogs are still dangerously
vulnerable to the viral particles. The disease has the potential to
do a great deal of damage to cells throughout the body, but especially
those located in the liver, kidneys, and eyes. Though it is not as widely
known and recognized as afflictions such as distemper, it is important
to be aware of and vaccinate against CAV-1 and ICH.
Why
and how might my dog become infected?
Every
viral pathogen has its own unique method of attack and invasion. CAV-1
particles are generally picked up through contact with an infected animal’s
urine. The virus can remain in a recovered dog’s kidneys for up
to one year, making it all the more difficult to determine what locations
might be contaminated. The particles enter the body through the nose
or mouth and make their first home in the tonsils. Here the virus replicates
and proceeds to invade the nearby lymph
nodes.
This process
of replication continues for anywhere from 4 to 8 days, at which point
the virus spreads out of the lymphatic system and enters the bloodstream.
Once in the blood, CAV-1 particles beat a path to the target organs
– the liver, kidneys, and eyes. The viral particles themselves
are cytotoxic
which is why they are capable of doing so much damage. The liver is
almost always the hardest hit organ, with consequences including disturbance
of protein and fat manufacture, problems with bile secretion, and difficulty
detoxifying drugs, chemicals, and bacteria from food.
ICH is
not always fatal, but when it is, death is usually a result of massive
hemorrhage, fluid leakage from a severely damaged liver, and central
nervous system trauma which triggers seizure and coma.
How will my vet reach a diagnosis of ICH?
Since
symptoms of ICH overlap significantly with symptoms for other disorders,
your veterinarian must differentiate between ICH and distemper or various
kinds of toxicity. This process of differentiation is accomplished using
a variety of different methods, but generally involves the combination
of laboratory tests, clinical observations, and information regarding
individual exposure risk.
A characteristic
early sign of ICH is leukopenia,
or low white blood cell count, but this alone is not enough for a definitive
diagnosis.
Other
symptoms attributed to cases of ICH include nausea, vomiting, loss of
appetite, jaundice, light-colored stools, and painful swelling of the
abdomen. More severe cases may involve high fever, tearing eyes, tonsillitis,
laryngitis, swollen lymph nodes, jaundice,
and pale gums, tongue, and nose. A condition known commonly as “blue
eyes” may develop following the retreat of gastrointestinal symptoms.
This condition is a result of the presence of viral particles in the
eyes and usually resolves itself given time. Occasionally however “blue
eyes” will evolve into a more serious condition such as glaucoma.
Urinalysis
and blood tests may be run in an attempt to detect viral antibodies.
Similarly, viral antibodies can be detected using immunofluorescent
techniques. In addition, the ELISA
test may be used to look for the presence of viral particles in the
feces of a sick animal.
What are the treatment options for dogs with ICH?
Treatment
for dogs suffering from ICH is mainly supportive and can be extremely
variable depending upon the specific symptoms being exhibited by an
individual animal. If damage to cells is severe, an intravenous catheter
should be inserted immediately in order to administer fluid and glucose
to restore blood sugar balance. It is generally recommended that patients
avoid consuming solid foods for several days. Blood transfusions may
be in order if the level of hemorrhaging is great, and eye drops are
sometimes administered to help alleviate eye irritation.
As is
the case with other viral diseases, all bodily functions should be steadily
monitored, and the ailing dog should be provided with a clean, warm,
and comfortable environment in which to reside. A hospital stay may
be warranted, but not in every case.
How can I vaccinate my pet against CAV-1?
Vaccines
are complex substances and raise many questions. For information about
vaccines in general, please go to An
Introduction to the World of Vaccines.
The number
of vaccines currently on the market for CAV-2 is large, but few exist
exclusively for CAV-1, and those that do often cause serious complications.
Thankfully, because CAV-2 and CAV-1 are so closely related, vaccination
against CAV-2 also produces effective immunity against CAV-1. CAV-2
antibodies are often included in the combination vaccine administered
to combat distemper and parvovirus. This shot is given at 3 to 4 week
intervals from the time a puppy is 6 weeks old until at least 16 weeks
of age.
How else can I help prevent the disease?
The CAV-1
virus with its non-enveloped particles is rather resistant to deterioration,
and is capable of withstanding exposure to many chemicals and even certain
frequencies of UV radiation. Further, the viral particles can survive
for days at room temperature and for even longer at temperatures less
than 4°C (39°F). They can however be inactivated after only
5 minutes at temperatures of 50 to 60°C (122 to 140°F), making
steam cleaning a viable option for disinfecting carpets or similar materials.
Chemical
disinfection of contaminated areas is effective with the use of cleaning
solutions containing sodium hydroxide, iodine, or phenol.
The best
methods of prevention are of course vaccination and avoidance. Unprotected
puppies or adult dogs should be kept away from contact with other dogs
or with public areas until they have established sufficient levels of
immunity through a course of vaccinations.
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Additional
resources on the web: