Lecture: Infectious disease and vaccination

Infectious disease and vaccination

Lecture Notes

Here we will discuss basic concepts of infections disease and vaccination for our dogs and cats

Infectious diseases

Lecture Notes

An infectious disease is a clinical illness that results from the presence of a pathogen; the most common pathogens involved in cat and dog infectious disease are viruses and bacteria.

Transmission of an infectious disease often occurs because the pathogen is shed in the animal's bodily fluids and can therefore affect other animals either directly…through animal to animal contact…or indirectly, through contact with contaminated bedding, bowls, people, etc….anything that comes in contact with the bodily fluids. Each disease will vary, but in general, shedding the pathogen in bodily secretions such as the saliva, urine, feces, and discharge from the nose and eyes.

For our dogs and cats, the population that is most at risk is the newborn and very young animals, because their immune systems are not yet developed to a stage that can help them fight infection. Unfortunately, the severity of the disease and mortality rate are highest in these younger animals.

Also, animals kept in crowded, stressful environments such as kennels or shelters are most susceptible to infections. It is difficult to control the spread of disease when housing many animals in one facility, and, as with human diseases, stress plays a major role in an organism's ability to fight infection.

Viral diseases: cause and effect

Lecture Notes

The majority of infectious diseases that affect cats and dogs are causes by viruses. Viruses cannot survive independently; they require host cells in the cat's or dog's body for replication.

Once a virus has gained access to a susceptible cell, it exerts control over some of that cell's biochemical processes, which allow replication and eventual infection of other cells.

When enough host cells are destroyed by this process, the damaged tissue and the animals' immune reaction to the infection result in signs of clinical disease.

Viral diseases: control and prevention

Lecture Notes

Very few viral diseases respond to antiviral medication, so control is mainly achieved by providing supportive therapy to the animal.

Supportive therapy includes providing fluids and electrolyte support, preventing secondary infections with opportunistic bacteria, providing excellent nutrition, and basically keeping the animal as comfortable as possible in an environment that encourages rest.

Fortunately, there are vaccines to help prevent many illnesses that affect cats and dogs. Vaccination has long been considered a primary tool in helping our companion animals live a long, healthy life.


Lecture Notes

Vaccines help prepare the body's immune system to fight the invasion of disease-causing organisms. Vaccines are composed of infectious agents that have been altered in some way to make them nonpathogenic. In other words, they look like the disease-causing pathogen to the immune system but don't actually cause disease. When the vaccine is introduced to the body, the immune system is mildly stimulated so that if a dog or cat is ever exposed to the real disease, his immune system is now prepared to recognize and fight it off entirely or at least reduce the severity of the illness.

Routes of administration

Lecture Notes

Vaccines can be administered to the animal as an injection into the muscle….as an injection under the skin…or the vaccine can be administered into the nasal passages. Each specific vaccine will have a recommended route of administration.

Vaccination guidelines for kittens/puppies

Lecture Notes

For most of the relevant vaccines, puppies and kittens should receive their first vaccinations at around 6-8 weeks, and then again every 3-4 weeks until they are about 16 weeks old.

What is the reason that puppies and kittens need a series of vaccinations? It's because of something called maternal antibody blocking.

Maternal antibody blocking -1

Lecture Notes

Puppies and kittens are born with immature immune systems which make them highly susceptible to contracting disease. Fortunately, we know that the first milk a mother cat produces, colostrum, contains antibodies that help protect her offspring from infectious disease until their immune systems are mature. These maternal antibodies are essential, but it presents some challenges.

Around 6 weeks of age, the antibodies that a puppy or kitten received from it's mother start to decline, and continue to decrease until they are undetectable by around 16 weeks of age if the mother was vaccinated and had a strong immunity. This antibodies may disappear much sooner if the mother was not vaccinated.

Maternal antibody blocking -2

Lecture Notes

As mentioned, around 6 weeks of age, the antibodies that a puppy or kitten received from her mother start to decline, and continue to decrease until they are undetectable by around 16 weeks of age.

Maternal antibody blocking -3

Lecture Notes

the challenge then is that during this window, is that the maternal antibodies may actually block the vaccine's ability to stimulate the kitten's or puppy's immune system…because the antibodies already present are recognizing the vaccine as something they should destroy.

That would not be a problem if the maternal antibodies were strong enough to prevent infection of the natural disease, but remember that they are declining during this period, so they may not be at a sufficient level to protect against the natural infection.

Maternal antibody blocking -4

Lecture Notes

So, during this window, while maternal antibodies may block a kitten's or puppy's active response to vaccination during this time, they may not be able to prevent infection with disease. We administer a series of vaccinations to help the puppy's or kitten's immune system to gradually build and overcome the potential for maternal antibody blocking during this time.

Example vaccination schedule for puppies/kittens

Lecture Notes

That is why we give a series of vaccinations. Again, these will start around 6-8 weeks and continue every 3-4 weeks until the animal is about 16 weeks old.

Rabies vaccination schedule

Lecture Notes

The rabies vaccination is handled a bit differently, and is usually mandated by state and/or local laws. The rabies vaccination is given to puppies and kittens as a single injection; the earliest age to receive the vaccination is 12 weeks and no later than 16 weeks.

Vaccination guidelines for adults

Lecture Notes

For adult animals then, you and your veterinarian can work together to best determine a vaccination schedule. This will depend on the type of vaccine, your animal's age, medical history, environment and lifestyle. It is standard that adults are given a booster of their core vaccines one year after the initial series. Beyond that, adults might be revaccinated annually or every three years.

As for rabies, after the first rabies vaccine has been given, an animal must have a booster one year later. After that, some areas require annual vaccination; others require a vaccination every three years. In almost all states, proof of rabies vaccination is mandatory.


Lecture Notes