Strep Zoo in Dogs: What UK Pet Professionals Need to Know

Over recent years, veterinary researchers have highlighted Streptococcus equi subsp. zooepidemicus (commonly shortened to S. zooepidemicus or Strep zoo) as an emerging bacterial pathogen in dogs, particularly in settings where animals are housed closely together.

This article is intended to support UK pet professionals working in multi-dog or group care settings by providing context, not diagnosis.

What is Strep zoo?

S. zooepidemicus is a type of bacteria belonging to the Group C streptococcus. It was first identified in the early 1900s and can affect several animal species, most commonly horses.

In horses, the bacteria often lives harmlessly as part of their normal respiratory flora and doesn’t usually cause illness. However, in other animals, including dogs, it can sometimes act as an opportunistic infection, meaning it may cause disease when an animal is stressed, unwell, or exposed in certain environments

In dogs, the bacterium has been linked to severe respiratory illness, including cases of acute pneumonia, sometimes with a rapid onset and significant clinical impact.

Canine infection is typically associated with specific risk environments rather than routine day-to-day contact.

History and identification in dogs

Although S. zooepidemicus was first associated with canine infection in the 1970s, reports of illness caused by this bacterium have become more frequent in the last decade. UK vets and researchers, including those at the Royal Veterinary College, have observed an increasing number of cases and are actively researching its behaviour and impact in dogs.

Signs and symptoms

In severe cases, affected dogs may show symptoms such as fever, lethargy, nasal discharge (sometimes blood-tinged), rapid breathing and sudden deterioration within 48 hours. This reflects the bacterium’s ability to cause aggressive, pneumonia-like disease and immediate veterinary treatment should be sought.

However, it’s important to note that:

• S. zooepidemicus infection in dogs is relatively uncommon overall.

• Many dogs with respiratory signs will have more typical infections (e.g. kennel cough).

• Dogs with mild symptoms may recover well with appropriate veterinary care.

Diagnosis and treatment decisions must always be made by a qualified veterinary surgeon.

Where cases have been seen

Reports of Strep. zoo in dogs worldwide have included rescue centre outbreaks and multi-dog environments. Large-scale outbreaks are more often reported internationally Strep. zoo has occurred in the UK in connection with kennel or group housing situations. The recent identification of two dogs with the disease at a dog show in the midlands has brought the issue to the forefront.

Outbreaks tend to occur where dogs are mingling, such as kennels, rehoming centres, and racing or working environments that bring many dogs into close contact.

Transmission and risk factors

The bacterium is typically spread via direct contact — such as sniffing, licking or close proximity — and through shared surfaces or items like water bowls and bedding. Kennelled or stressed dogs are often at increased risk of developing severe disease when exposed.

For pet professionals, these risks reinforce the importance of intake checks, hygiene protocols, and clear escalation pathways to veterinary care.

Prevention and management

• Good hygiene and thorough disinfection in multi-dog settings can help reduce bacterial spread.

• Early veterinary assessment for dogs with significant respiratory signs is crucial.

• There is no specific vaccine currently available for S. zooepidemicus in dogs.

Veterinary research is ongoing to better understand the best diagnostic and control measures, as well as to map how the bacterium behaves in different canine populations.

Pet professionals should never attempt to manage suspected infectious disease without veterinary input.

Key points for professionals

✔ S. zooepidemicus is a recognised bacterial cause of respiratory disease in dogs, especially in group settings.
✔ UK cases indicate higher risk in kennels and group housing environments.
✔ Severe disease is possible, but most companion dogs do not encounter it in everyday life.
✔ Hygiene, early recognition and veterinary care remain the best strategies for managing risk.

Summary

Strep Zoo isn’t a “new mystery disease” but rather a recognised bacterial infection with increasing reporting in dogs, particularly where animals congregate. Awareness, good husbandry and collaboration with your vet are the strongest tools pet professionals have in responding appropriately.

S. zooepidemicus is uncommon, but awareness matters in group settings. Clear hygiene protocols, prompt veterinary referral, and calm, informed responses protect both animal welfare and professional confidence.

For most pet professionals, good hygiene, vigilance, and collaboration with vets remain more important than concern.