By Dr. Karen Shaw Becker
Certain diseases that affect dogs are the result of factors such as lifestyle (for example, obesity and diabetes) and genetics (e.g., brachycephalic airway syndrome in breeds with pushed-in faces such as Pugs), and there is a wealth of information here at Mercola Healthy Pets on how lifestyle and genetics influence your pet's health.
But the topic today is contagious diseases your canine companion can acquire from other dogs, and specifically the life-threatening diseases every puppy should be vaccinated against: parvovirus, distemper, infectious hepatitis and rabies.
4 Contagious and Potentially Fatal Canine Diseases
Canine parvovirus type 2, or CPV-2, is a virus that attacks the gastrointestinal (GI) tract of both domesticated and wild puppies and adult dogs. In addition to the gastrointestinal effects of parvo, in very young and unborn puppies, it can damage the heart muscle as well.
Parvo is extremely contagious and is passed by direct dog-to-dog contact and contact with contaminated feces, environments and people. The virus can contaminate everything your dog touches, food and water bowls, collars and leashes, and the people who handle your dog and their clothing.
Parvo is a hardy virus that can survive extremes in temperature and humidity levels. It lives in the environment for long periods of time. Even tiny amounts of parvo-infected stool can contaminate an area and transmit the disease to other dogs entering the area. Parvo can be easily spread from one location to another on a dog's hair or feet, on a contaminated pet carrier and on shoes and other objects.
Canine distemper, which is also known as Carre's disease and was once called hard pad disease, is a highly contagious virus that primarily affects young dogs, both domesticated and wild, between the ages of 2 and 6 months. The disease can be fatal, especially in puppies and wildlife.
Non-immunized dogs that come in contact with an infected animal carry a high risk of contracting distemper, as do puppies born to an infected mother, and young dogs under extreme stress or who are immunocompromised. Dogs exposed to wildlife may also have a heightened risk of contracting the disease.
Bacterial infections, especially of the respiratory or GI tract may also make dogs more susceptible to the virus. On rare occasions, improperly attenuated (formulated) CDV vaccines have also been implicated as a cause.
However, most dogs are exposed to the virus that when they inhale the respiratory secretions of an infected animal, or come in direct contact with infected feces, urine or saliva. CDV can also be spread through direct or indirect contact with the bedding, bowls or other items belonging to an infected dog.
In susceptible dogs, the virus first reproduces in the respiratory tract and then moves on to the lymph nodes and the lymph and blood circulatory systems throughout the body. CDV can also infect a dog's skin, GI and urogenital tracts, central nervous system and other areas of the body. Infected dogs can shed the virus for several months after infection, even when they are not showing clinical signs of illness.
3. Infectious Hepatitis
Infectious canine hepatitis, or ICH, is caused by the canine adenovirus type 1 (CAV-1). The infection can cause damage to cells throughout a dog's body, especially those located in the liver, kidneys and eyes. At one time, there was a vaccine available to protect dogs from type 1 adenovirus, but it was discontinued because it caused a condition called blue eye, which is a protein deposit that resulted in a bluish tint to one or both eyes of vaccinated dogs.
These days, we vaccinate against canine adenovirus type 2 (CAV-2), which is a kennel cough virus, and the same core vaccine provides cross-protection against canine adenovirus type 1 as well.
ICH is found all over the world, and is spread by bodily fluids, including nasal discharge and urine. The most common method of transmission is direct contact with an infected dog, especially the dog's urine. Contaminated kennels or living quarters, bowls and other supplies, and human hands and shoes can also transmit the virus.
Dogs that recover from infectious canine hepatitis can shed the virus for up to a year in urine, which makes it very difficult to determine exactly what locations might be contaminated.
The infectious particles enter a dog's body through the nose or mouth and invade the tonsils, where the virus replicates and then infects nearby lymph nodes. The cytotoxic particles spread from the lymphatic system to the bloodstream in about a week. Once travelling through the blood, the virus infects other target organs, including the liver, kidneys and eyes, with the liver almost always being the most severely affected organ.
The rabies virus, also called acute viral encephalomyelitis, is an extremely serious, usually fatal inflammatory infection that affects the brain and central nervous system (CNS). In dogs (and cats) in the U.S., the rabies virus is most often transmitted when an infected fox, raccoon, skunk, coyote or bat bites a pet. Infectious virus particles are present in the saliva of these animals to more efficiently transmit the disease.
It's extremely rare, but transmission has also been documented to occur through exposure to the escaping gases of an infected decomposing animal. This form of transmission usually occurs in caves where there are large populations of infected bats. It's something to think about if you have a hunting dog or you like to explore caves with your dog.
Rabies is a zoonotic disease, meaning it can also be transmitted to humans by infected animals. Once the rabies virus enters a pet's body, it multiplies in muscle cells, and then spreads to nearby peripheral sensory and motor nerves, which move it to the brain and central nervous system (CNS).
During the incubation period before the virus enters the CNS, the infected animal doesn't exhibit symptoms and can't transmit the disease. The virus moves relatively slowly, with the average time between exposure to brain involvement being three to eight weeks in dogs. However, incubation periods as long as six months have been reported in dogs.
Responsible Immunization Is the Key to Keeping Your Dog Safe From These Highly Contagious, Potentially Fatal Diseases
I realize many pet parents are against all veterinary vaccines. And many vaccines conventional veterinarians recommend do provide more risk than benefit, in particular bacterin-based vaccines and non-core vaccines. But in some situations, leaving your puppy unvaccinated poses a much greater risk than benefit (those of you working in shelters and rescues know exactly what I'm talking about).
It's important to understand that not vaccinating your pet against the four diseases I discussed above means he's unprotected from infection. He'll be safe if you never let him outdoors or socialize him, which is obviously unthinkable. Your dog is a social creature — you can't isolate him and expect a good outcome.
Dogs deserve to go outside, run, breathe fresh air, move their bodies through the woods, sniff things and interact with other dogs. However, all these behaviors pose a risk to their health if they aren't protected against highly contagious, potentially deadly diseases. Over-vaccination is a terrible problem in the veterinary community, but in my professional opinion, providing baseline protection against these four diseases provides your pet with lifetime immunity — and you with peace of mind.
The Core Vaccine Protocol I Recommend
My vaccine protocol for puppies is to administer a first round of distemper, parvo and adenovirus before 12 weeks of age, usually around 9 to 10 weeks. I give the second round between 15 and 16 weeks. Two weeks after the second round, I titer to insure the dog has been immunized and not just vaccinated.
When it comes to rabies, I prefer to give the first vaccine at 6 months, and then as required by law, a booster one year later and every three years thereafter. Until immunity is established through titering at the two- to four-week mark after your pup's second round of shots, use extreme care if you take her to places where other dogs congregate, including:
- Pet stores
- Dog parks
- Puppy or obedience classes
- Doggy daycare or boarding facilities
- Grooming shops
Also, don't let your dog of any age come in contact with the poop of other dogs or wild animals, and properly dispose of your own pet's poop as well. If your dog is vomiting or has diarrhea or has been exposed to an ill dog, keep him away from any area where he might come in contact with other dogs or wild animals.
Unvaccinated dogs should not be exposed to ill dogs or those with questionable health or immunization histories. And if you are in contact with a sick dog, avoid contact with other dogs until you've washed your hands thoroughly and changed clothes, if necessary.