Streptococcal Pneumonia in Dogs

An Emerging Respiratory Disease That Can Kill

The Canine Infectious Respiratory Disease (CIRD) Group at the Royal Veterinary College (RVC) are currently researching a bacterial disease that has been increasingly implicated in fatal cases of infectious pneumonia in dogs over the past five years. They are calling for dog owners and vets to recognise the signs of the potentially fatal disease Streptococcal pneumonia to ensure rapid treatment and contribute to research to reduce further spread.

The bacterial infection Streptococcus zooepidemicus causes a severe, bloody pneumonia in dogs, producing signs similar to those associated with toxic-shock syndrome in humans.

How is Streptococcus zooepidemicus transmitted?

streptococcal pneumonia

Some dogs can be ‘carriers’ of the bacterium which causes Streptococcal pneumonia but show no symptoms

The bacterium can be ‘carried’ by dogs in their upper respiratory tract (most likely their tonsils) without showing any symptoms of disease and it is likely that, as yet unknown, bacterial, host or environmental factors, possibly including an over-exuberant immune response to the bacteria, are responsible for the severe pneumonia observed in the worst cases. These ‘carrier’ dogs may be an important source of infection if introduced to new populations, especially in rehoming kennels where dog come and go all the time.

What are the signs of Streptococcal pneumonia in dogs?

Infected dogs develop the following signs:

  • Sudden-onset fever
  • Sneezing
  • Rapid, shallow breathing
  • Bloody discharges from the nose or mouth
  • Lethargy (tiredness)
  • Reluctance to eat

Some dogs may collapse, which indicates a developing septicaemia. In most cases this occurs within 12-24 hours of the onset of the first symptoms (which may be mistaken for classical ‘kennel cough’ caused by viruses). In a small proportion of cases, the disease has been known to be fatal to dogs within 24 hours of contracting the infection.

How likely is the disease to occur in pet dogs?

streptococcus zooepidemicus

Outbreaks can particularly occur in situations where dogs mix in groups, such as rehoming or boarding kennels and in hunting and racing greyhound communities.

In most cases there seems to be a trigger-factor such as a significant stressful event, for example rehoming, strenuous activity such as a race, or preceding illness. Outbreaks are isolated and tend to occur where dogs mix in large groups. Although it is rarer in family pets, it is still important for owners to be aware of the symptoms, especially if they regularly visit kennels or go to events where animals gather. In the initial stages, signs are similar to those of the more common ‘kennel cough’, which occurs in similar environments. However, in Streptococcus zooepidemicus outbreaks, dogs quickly become seriously ill and show very severe signs. In contrast, most dogs with kennel cough will usually have a relatively mild illness and deaths are rare.

Can pneumonia caused by Streptococcus zooepidemicus be treated?

Treatment of Streptococcal pneumonia is often ineffective unless started rapidly following onset of the first symptoms and is currently based on a suspected diagnosis. If owners notice the sudden onset of a fever in their dog, accompanied by sneezing, nasal discharge which is often bloody, and their animal becoming lethargic, they are advised to seek veterinary help immediately. With prompt identification, medical treatment and supportive care, dogs can make a full recovery from streptococcal pneumonia.

Dr Priestnall and collaborators at the Animal Health Trust and University of Nottingham are engaged in a study to investigate the prevalence of Streptococcus zooepidemicus in the wider UK dog population, including the role of potential carrier animals. As part of this work a rapid and sensitive diagnostic test is being developed which has already been shown to be much more sensitive at detecting possible carriers of the bacterium at low levels than traditional bacterial culture techniques alone. Further research into Streptococcus zooepidemicus is required however to shed light onto how this bacterium causes the most severe and fatal infections.