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How to Choose the Vaccines That Will Best Protect Your Dog Against Infections

Core vaccines (see Chapter 3) should be given to any dog, wherever it lives.

On the opposite, non core vaccines are optional vaccines that can be administered upon a careful consideration of your dog's exposure to infective pathogens.

Non-core vaccines is a concept developed by a board of veterinary experts from the World Small Animal Veterinary Association. The goal of the Vaccination Guidelines Group (VGG) is to help design vaccination schedules that provide maximum protection to dogs and reduce the vaccine load to a minimum.

The VGG recommends that non-core vaccines should be prescribed only after examination of the regional situation, the local environment and dogs' lifestyle. These vaccines usually have a shorter duration of immunity than core vaccines and boosters should be administered once a year.

They complement core vaccines that should be given to any dog and protect against diseases that are very contagious and often fatal .

They respond to 3 types of health concerns:

  • Respiratory diseases
  • Lyme diseases
  • Leptospirosis

Vaccines for infectious respiratory diseases

Kennel Cough is the most commonly used name for dog infectious respiratory diseases. But you may read other names: infectious tracheobronchitis (ITB), canine infectious respiratory disease (CIRD), or even canine infectious respiratory disease complex (CIRDC).

Infectious respiratory diseases are generally initiated by viruses:

  • Canine parainfluenza virus (CPiV)
  • Canine adenovirus-2 (CAV-2)
  • Canine influenza virus (CIV)
  • Canine distemper virus (CDV)

Or a bacterium: Bordetella Bronchiseptica.

Other pathogens can be recovered from dogs with Kennel Cough. They are considered as secondary or opportunistic pathogens, meaning that they should not cause the disease, but are present and potentially aggravate the symptoms. They are:

  • Viruses: canine respiratory coronavirus (CRCoV) and canine pneumovirus (CnPnV).
  • Bacteria: Streptococcus zooepidemicus, Pseudomonas, Escherichia coli, Klebsiella and Mycoplasma

Often, a single pathogen doesn't act alone and a combination of viruses and bacteria are involved in the most severe forms of respiratory diseases.

A study on dogs with canine infectious respiratory disease in Germany illustrates the situation, although the pathogens involved here may differ a lot in other regions of the world.

Repartition of pathogens involved in canine respiratory infections in Germany

Some respiratory pathogens

Canine Parainfluenza Virus (CPIV)

  Canine parainfluenza virus identification card

CPIV is a common and very contagious virus. It settles in the nose, pharynx, larynx, trachea and bronchi where it replicates. It attacks the mucosa and bares very rapidly important parts of the epithelium by destroying the cilia.

CPIV is responsible for the well-known goose honk cough. The infection often resolves spontaneously within 6-14 days except in the cases of co-infection with another virus or with Bordetella.

Bordetella bronchiseptica

  Bordetella bronchiseptica identification card

Bordetella bronchiseptica is the most virulent bacterium involved in canine respiratory diseases.

Bordetella resides in the respiratory tract of healthy dogs. For some still unknown reasons, it can wake up and start colonizing respiratory tissues.

Bordetella is virulent in many ways. It paralyzes the ciliary movements that help clear away foreign bodies from the mucosa. (see Chapter 1: the first line of defense of the immune system). It then binds to the respiratory epithelium thanks to filamentous proteins (hemagglutinin, fimbriae).

Bordetella releases many toxins. Some of them induce respiratory epithelium necrosis whilst others help elude the host's immune defense.

Canine Influenza Virus (CIV)

  Canine influenza identification card

After infection through air or contaminated objects, the virus incubates for 2 to 4 days. It colonizes the nasal cavity, the trachea and the conducting airways causing inflammation (rhinitis, tracheitis, bronchitis and bronchiolitis) and opening the door to bacterial infection.

The symptoms are coughing and nasal discharge. The disease typically lasts for 10-20 days. Over that period of time the dog keeps on shedding viruses and being contagious. It should be kept away from other dogs (and cats).

Canine Adenovirus type 2 (CAV-2)

  Canine adenovirus type 2 identification card

CAV-2 is part of the core vaccination recommendation (see Chapter 3)

CAV-2 enters the body through the nose or mouth. It replicates in the upper respiratory tract and in non-ciliated bronchiolar epithelial cells.

The infection peaks at 3-6 days after infection and recedes within 9 days. It causes inflammation in the airways.

Without co-infective pathogens the symptoms in adult dogs are mild (cough, expectoration of mucus), although damage in the lungs may be extensive.

Canine Distemper Virus

  Canine distemper virus identification card

Canine Distemper Virus is part of the core vaccination recommendations (see Chapter 3).

The virus is usually airborne, but can also contaminate dog food. It first replicates in some white cells of the immune system and then colonizes many other organs.

In addition to the signs of infectious respiratory disease (nasal and eye discharge, coughing) dogs may display digestive or neurologic symptoms.



As always in infectious diseases, the symptoms and outcomes are more severe for young puppies than for adult dogs.

In adult dogs the symptoms of a viral infection range from intense episodes of coughing and expectoration lasting for 1 to 2 weeks to hardly any symptoms at all.

Bacterial superinfections add other types of symptoms: fever, dyspnea (irregular breathing) purulent nasal and ocular discharge and loss of appetite.

The infection may develop into a life-threatening pneumonia, especially in puppies.

Treatment and prevention

Numerous antibiotics from different classes can be prescribed against the bacteria involved in respiratory diseases.

They complement supportive therapies, that treat symptoms but not the cause of the disease: antitussives, glucocorticoid anti-inflammatories and/or bronchodilators.

Vaccination is the only protection against respiratory viruses. Your vet may advise you to complement the core vaccination program with vaccines against respiratory pathogen if he thinks your dog is particularly exposed.

Canine adenovirus-2 (CAV-2) and canine distemper virus (CDV) are already part of the core vaccination program that should be administered to any dog.

Vaccines against Bordetella bronchiseptica, canine parainfluenza virus, and canine influenza virus are optional, non-core vaccines. Because these pathogens are very contagious, they are recommended for dogs that can get in contact with other dogs in kennels, in shelters or in co-housed environments.

Non-core respiratory vaccines are NOT INDICATED if your dog is NOT EXPOSED to other dogs.

Here is an example of a vaccination schedule (exposed dog):

Example of a vaccination schedule for a dog exposed to respiratory pathogens

Years of age Core vaccines Non-core vaccines
1 DHP unless this was given at 26 weeks in the puppy schedule CPi, Bb
2   CPi, Bb
3   CPi, Bb
4 DHP or serology CPi, Bb
5   CPi, Bb
6   CPi, Bb
7 DHP or serology CPi, Bb
8   CPi, Bb
9   CPi, Bb
10 DHP or serology CPi, Bb

Bb: Bordetella bronchiseptica - Cpi: Canine parainfluenza virus - DHP: Canine distemper virus, canine adenovirus, canine parvovirus type 2

Main references


Borrelia burgdorferi

Borrelia burgdorferi is a spirochete bacterium that causes Lyme borreliosis also known as Lyme disease (or Lyme arthritis in humans). It is transmitted exclusively by ticks of the genus Ixodes.

Spirochetes are long and slender bacteria with a characteristic helical or corkscrew shape. They are mobile in a liquid environment thanks to their flagella that makes the cell body undulate.

As a consequence, and unlike other bacteria, spirochetes do not rely on fluid movement to progress in hosts' body fluids (blood and lymph). They can swim. It makes them very invasive, enables them to get deeper in tissues and to colonize many organs.

Canine influenza identification card


Borrelia burgdorferi is transmitted by ticks of the genus Ixodes: mainly Ixodes scapularis and Ixodes pacificus in North America or Ixodes ricinus in Europe. In some very rare cases, it can also be transmitted in utero or through the urine or the mothers milk.

Ticks have three development stages: larval, nymphal and adult. At each stage they have to find a different host on which they feed for a period of 3 to 5 days. During their stay on an animal, they feed on its blood and increase their size up to 3 times.

They need this blood meal to continue their lifecycle. Once fed, they detach from their host and molt towards the next stage (larvae or adult) or lay eggs (when they fed on the host as adults).

A tick gets infected by the bacterium Borrelia in its earlier stage as a larva or even as a nymph when feeding on an infested mammal, usually a rodent. Borrelia then migrates to the gut of the tick where it replicates and resides, waiting for the next host and the next blood meal.

On a new host, a tick walks around for a suitable place to feed on. It then bites by inserting its capitulum in deeply the hosts derma. It sucks blood for 3 to 5 days. In many occasions, it regurgitates saliva back into the host.

Ticks saliva contains many different types of molecules that help:

  • Cement the capitulum to the host skin
  • Inhibit blood coagulation and platelet aggregation
  • Vasodilate blood vessels
  • Prevent itching and pain

In addition to Borrelia, ticks saliva may also contain other pathogens got from a meal on a previous host: tick-borne encephalitis virus (TBEV- other name for Powassan virus), Babesia, Anaplasma and Ehrlichia bacteria. They respectively may cause encephalitis, human babesiosis, anaplasmosis, and ehrlichiosis.

These pathogens are transmitted during the regurgitation episodes.

It is widely recognized that the transmission of Borrelia in a new host, let say a dog, takes place 24-48 hours after the beginning or the feeding process. However, a very recent study shows that it could be much quicker and occur only a few hours after the beginning of the meal (to be confirmed).

To get infected your dog needs to live in places 1/ where Ixodes ticks live and 2/ where there are rodents infected with Borrelia burgdorferi.

As the infective process is the same as for humans you can refer to human epidemiology of Lyme disease. For the US you can find the map here

You'll notice that living in the North Eastern part of the US is more risky.

There is no such map for Europe. Instead, you may track the presence of the vector tick, Ixodes ricinus in Europe


Lyme disease is a major public health concern. In the US, it is the second infectious disease (300 000 cases) just after AIDS. In Germany estimates go up to 1 million people!!

First human symptoms consist of a characteristic erythema migrans that develops over a few days after the tick has bitten. It corresponds to the replication of the bacteria within the skin. It may be associated with fever or nasal discharge.

The infection should be treated early. Because the most serious part comes well after, sometimes years after, in the form of chronic systemic disorders affecting the heart, the brain, the joints(read more at The Center for Disease Control and Prevention - Lyme disease).

In dogs, the disease is not that bad. Only 5% of dogs infected with Borrelia Burgdorferi develop symptoms: transient fever, anorexia, and arthritis (Littman et al. 2006). It affects mainly puppies and the signs resolve spontaneously within a few days.

Nevertheless, the infection deserves some attention on the long run. Dogs tested positive to Borrelia specific antibodies tend to develop a certain type of renal disease (protein-losing nephropathy).

In addition, co-infection with other pathogenic micro-organisms (bacteria, parasites) usually transmitted by Ixodes ticks may lead to some sort of lameness or arthrosis.

Diagnosis and treatment

Lab exams assess Borrelia serology. If positive, the test indicates that your dog was contaminated with the bacterium, recently or a long time ago, or that it was vaccinated.

If your dog is seropositive AND displays the symptoms that are consistent with Lyme disease, your vet may prescribe an antibiotic treatment. The standard treatment is doxycycline twice a day for one month. Without symptoms no antibiotic treatment is necessary.

If your dog is seropositive, your vet should consider the possibility of a renal disease and of a co-infection by another tick-borne parasite or micro-organism.


You should first consider the place where you live. Can you find here Ixodes ticks that carry Borrelia?

To answer this question you should either ask your vet and/or look at epidemiologic maps (see above).

If so, it means that your four-legged friend is exposed. But more importantly, that you and your family are also at risk!!

Borreliosis is a much more severe disease in humans than in dogs. And ticks can bite you just the same way as they do on dogs.

Priority #1: protect yourself and your family whenever you are going in a possibly contaminated area (typically, tick-infested woods:

  • Wear long trousers and shirts with sleeves.
  • Prefer bright clothing, because its easier to spot ticks on them
  • Use skin repellent
  • After your walk , have a shower and use a washcloth
  • Examine your body (or ask for help). Pay special attention to hot and wet areas: the armpits and groins. Dont forget that before they feed, tick are very small, especially the larvae. If you find one, detach it with a tick removal forceps. Never use chemicals that may make the tick regurgitate. Monitor the place where the tick bit for an erythema migrans.

Priority #2: protect your pets against parasites.

There are some ticks repellents on the market that prevent bites (at least part of them). Ask your vet about them.

Priority #3: consider vaccinating your dog

There are a few vaccines available. 2 injections, 2 to 4 weeks apart, should be administered to young puppies, and then booster should be injected once a year.

There are some adverse events in less than 2% of the cases. They involve an unwanted immune reaction. This is this the same type of reactions that caused the vaccines in humans to be discontinued.

Should you vaccinate your dog against Borrelia burgdorferi?

Vaccination in non-endemic regions is not necessary.

In endemic areas, the issue is still controversial. Some vets vaccinate, most experts don't (ACVIM Small Animal Consensus Statement on Lyme Disease in Dogs). Opponents to vaccination argue that the disease in dogs is mild and can be cured easily with a proper antibiotic treatment. They also point out that vaccination against Borrelia doesn't prevent the transmission of the other tick-borne pathogens (namely, TBEV virus, Babesia, Anaplasma and Ehrlichia).

Anyway, this is a medical decision that only you can make with the help of your vet.

Main references


Leptospira interrogans

Leptospirosis is also a very important public health issue. It is a zoonosis: it can be transmitted directly from dogs to humans.

The bacterium Leptospira interrogans is widely spread all over the world. 5 to 30% of infected people die (see Word Health Organization brochure on the topic). Children are especially vulnerable and the disease is more frequent in hot and developing countries.

Leptospira interrogans is a spirochete bacterium. As every other spirochete, it is long and thin and has a flagellum that makes it very mobile and very invasive. It can infect any organ.

There are different subtypes of the bacterium. They are called serovars. Its important you are aware of these variations because they have some practical implications on the serological diagnosis of the disease and on the vaccination strategy.

The serovars that are found in dogs are: Canicola, Icterohaemorrhagiae, Grippotyphosa, Pomona, and Bratislava

Leptospira interrogans in dogs identification card


Leptospira bacteria are shed in the urine of infected mammals. They survive longer in humid and warm environments.

They contaminate the soil or the water a new mammal host may drink. They can also enter a new host's body by a wound in the skin or any type of mucosa: mouth, nose, eye conjunctiva.

The transmission is direct. Rodents serve as a reservoir for the bacterium. They can pass it to dogs or directly to humans. Contamination may also come from large animals: horses, bovines or swine.

Professionals such as veterinarians, farmers, breeders, pet shop workers that work or live in close relationships with animals are more at risk to get infected.

Disease mechanism

Leptospira first incubates for 4 to 20 days in the tissues close to the entry point.

It then migrates to different organs, mainly the kidneys, the liver, the lungs or stays in the blood. It is the acute stage of the disease.

If the infected animal is an incidental host, the bacteria are finally eliminated by the immune system. If it is a reservoir host, the infection becomes chronic, Leptospira bacteria remain and replicate within the kidney and keep on shedding in the urine.


In dogs, as for the other mammals, they can vary from mild to very severe and death.

Leptospira attacks primarily the kidneys, the liver, the lungs and the blood. Note that several organs can be affected at the same time.


Acute kidney insufficiency (= acute renal failure) is the main symptom in dogs infected by Leptospira. The kidneys lose their ability to produce urine. As the blood can't be filtered anymore, toxins accumulate. Excess of water in the body can't be eliminated and causes overhydration. It is characterized by the rapid onset of vomiting, diarrhea and anorexia (get more information here).

This is a matter of emergency. It is reversible if treated on time by fluid and supportive therapy. However this episode of acute kidney failure may trigger the onset of an irreversible, slowly progressing chronic kidney disease. In practice, if your dog was infected by Leptospira, you should ask your vet to monitor regularly its renal function.


Leptospira causes liver cells destruction. It is generally considered that the disease develops when the liver has lost 70% of its initial mass. Symptoms are not specific to the disease and many are similar to those of kidney disease: anorexia, vomiting, abdominal pain, and/or diarrhea) which makes the diagnosis difficult. In addition the dog may suffer from excessive thirst and urination.

In the more severe cases, the dog may develop icterus (jaundice) and/or hepatomegaly (liver enlargment) accompanied by abdomen edema.

The diagnosis is confirmed by blood tests and imaging.


Severely affected dogs may develop a pulmonary hemorrhage which is the most frequent human manifestation of the disease. It is not common in dogs though. More frequently dogs only exhibit coughing and irregular breathing (dyspnea).


The manifestations are diverse. It may be small red spots of blood just under the skin (petechial hemorrhage), nosebleed (epistaxis), bleeding of the intestinal tract causing black tarry stools (melena) and/or vomiting of blood (hematemesis).


This graph shows the repartition of the symptoms in about 250 dogs with leptospirosis examined at the Veterinary University of Bern (Switzerland). A single dog may have different manifestations of the infection at the same time.

Obviously, in this study almost all dogs have a renal disorder.

Organ Involvement N affected/N total % affected
Renal 255/256 99.6%
Pulmonary 194/253 76.7%
Hepatic 66/254 26.0%
Hemorrhagic 38/209 18.2%

source:Major A et al. Increasing Incidence of Canine Leptospirosis in Switzerland. Int J Environ Res Public Health. 2014 Jul; 11(7): 7242–7260

Diagnosis and treatment

As leptospirosis symptoms are not specific to the disease, your vet can't rely on them to make a diagnosis. Complementary tests and imaging are necessary.

The first step is to try to understand where the symptoms come from. What organs are affected. Your vet will first perform blood and urine test.

Blood tests:

  • Abnormal values in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and/or hyperbilirubinemia reveal hepatic disorder
  • Changes in urea and creatinine signal kidney disease
  • Abnormal blood phosphate, potassium, sodium or chlorine suggest leptospirosis.

Urine tests: the presence of protein, glucose or blood signals renal failure.

Imaging (radiography and/or echography) is usually performed to get a better view of the damages to the lungs kidneys or liver with their possible consequences such as edemas.

When a leptospirosis is suspected, theres still a need for confirmation. 2 types of test can be used:

MAT (microscopic agglutination test) test detects anti-Leptospira antibodies. It has some limitations and is subject to false positive or false negative results. In case the dog was previously vaccinated against Leptospirosis, the veterinarian will have to perform the test twice to make the difference between infectious and vaccinal antibodies.

PCR (polymerase chain reaction) test looks for Leptospira DNA. It should be performed on both urine and blood. A positive result on blood with clinical signs indicates the dog is infected. A positive result on urine shows that it is shedding bacteria in the urine and therefore contaminates the environment. There may be some false negative though.

Diagnosing leptospirosis in dogs is far from easy. But it is necessary. This is matter of public health. You can't afford to risk your dog contaminating your household or your neighborhood.

Fortunately treating leptospirosis is easy. A 14-day treatment with doxycycline, ampicillin, penicillin or amoxicillin is usually recommended.

However, you vet may also need to take care or hepatic, renal or respiratory disorders, on the long term. This is another story


Vaccination against Leptospira is not considered as core by the board of WSAVA experts. This is because some indoor dogs kept away from wildlife, environmental water sources or any other source of contamination may not need it.

However, this is not a common situation and it is highly recommended to vaccinate all other dogs. Leptospirosis is a severe disease that is not easy to diagnose and that is transmissible to humans.

Newer, quadrivalent vaccines are recommended. They offer protection against Canicola, Icterohaemorrhagiae, Grippotyphosa and Bratislava serovars.

Main references


Not recommended vaccines

Some vaccines are not recommended by the WSAVA's Vaccines Guidelines Group.

Canine corona vaccines

This recommendation of the VGG rests on 2 considerations:

  • there is insufficient evidence that coronaviruses vaccines are protective: it is unclear whether available vaccines protect against the most virulent variants of the virus
  • enteric coronavirus is not a significant canine pathogen

Canine Adenovirus type 1 vaccines

Canine adenovirus type 1 vaccines protect against Canine adenoviruses type 1 and type 2. The same is true for canine adenovirus type 2 vaccines that protect against both viruses.

Against adenoviruses, you would rather adminster live attenuated vaccines that are more effective and trigger both humoral and cellular immunity.

The issue here is that live vaccines may revert back to their wild virulent form, and canine adenovirus type 1 cause a much more severe disease than the type 2.

This is why, whenever possible, using canine adenovirus type 2 live vaccines is preferrable.

Killed Canine Parvovirus type 2 vaccines

Live vaccines are much more effective than killed vaccines because they better simulate a real infection. They should be preferred over killed vaccines.

Main references