Ehrlichia Canis (E. canis): What you need to know

Canine ehrlichiosis is a deadly tick-borne disease of dogs caused by infection with the bacteria Ehrlichia canis.  This bacterium is carried primarily by the Brown Dog Tick (Rhipicephalus sanguineus) and is spread to dogs when an infected tick bites them.

Ehrlichiosis is an intracellular (inside the cell) bacterial infection that primarily affects the cells of the immune system.  Infected dogs can present with a range of clinical signs.

Due to its highly infectious nature, E. canis is deemed a notifiable diease.  This means all vet clinics and persons who suspect the presence of the diease, must report it to authorities (Biosecurity Queensland or Emergency Animal Disease Watch Hotline).

Life cycle

E. canis is maintained in cycles between ticks and either domesticated or wild animals in the family Canidae, including dogs, dingos and foxes.

Ticks acquire E. canis by feeding, as larvae, on infected canids. Once infected, the larvae maintain their infection and may transmit the infection to other canids when feeding as nymphs or adults. Adults may then produce eggs which are not infected with E. canis.

Dogs do not transmit the disease to each other, however, the organism can be transmitted directly from dog to dog through blood transfusions.

Disease phases

Canine ehrlichiosis has 3 disease phases:

-  Acute

-  Subclinical

-  Chronic

The severity of clinical signs can vary considerably among dogs.

Clinical signs

Acute phase

This phase is characterised by non-specific clinical signs, including:

-  Fever

-  Lethargy

-  Enlarged nymph nodes

-  Anorexia

-  Weight loss

-  Discharge from the nose and eyes

-  Bleeding disorders such as nosebleeds or bleeding under the skin that looks like small spots, patches or bruising.

There are usually abnormalities on blood tests including low platelets and mild anaemia (low red blood cells).  The acute phase of the disease can be fatal even with veterinary treatment.  If your animal survives, they are very unlikely to be completely cleared of the infection, but instead move to either the subclinical or the chronic phase of the disease. 

The incubation period for the development of acute disease is about 1–3 weeks.

Subclinical phase

Some dogs that recover from the acute phase can become subclinically infected.  This means that they have the infection but show no clinical signs of illness.  This phase can persist for months to years.

Subclinical dogs either:

-  Remain asymptomatically infected

-  Progress to the chronic form of ehrlichiosis

Chronic phase

Clinical signs are similar to the acute phase but are more severe. They can include:

-  Fever

-  Weakness

-  Weight loss

-  Bleeding disorders

-  Pale mucous membranes (gums)

-  Eye abnormalities

-  Neurological abnormalities

Infected dogs may be more susceptible to secondary infections.  Blood tests often show severely low platelets, low white blood cells and anaemia. This form of the disease can be fatal, and is extremely resistant to treatment.

Diagnoses

Ehrlichiosis is diagnosed through a combination of:

-  Consistent clinical signs

-  Blood tests

If you see clinical signs consistent with ehrlichiosis, consult a veterinarian.

Zoonotic potential

Infected dogs do not transmit E. canis to people.  In rare cases, people may become infected with E. canis after being bitten by an infected tick.

Prevention

There is no vaccine against E. canis in Australia.  The only way to prevent your dog from infection is to use appropriate tick prevention (outlined below) and to perform daily tick searches on your dog. 

Currently the only product in Australia registered to protect against E. canis is the Seresto Tick Collar.  As with all products, in order to ensure protection you must follow the instructions for application carefully, be vigilant in changing the collar at the correct time and not allowing it to go past its expiry date.  Pay particular close attention to the label as it protects against fleas longer than it does against ticks. 

For 98% protection against this disease, you must use a Seresto Tick Collar paired with either a Nexgard or Bravecto flea/tick product.

Using a flea/tick prevention product (e.g Nexgard or Breavecto) on its own is not enough - these products take 6-8 hours to kill ticks.  An infected tick only needs to be attached for 30 minutes for them to pass on the bacteria to your dog.

Distribution

E. canis can be found in most of the world, anywhere the Brown dog tick is found.  Australia has previously been free of E. canis.

In May 2020, the first detection of E. canis was made in Halls Creek and Kununurra area of Western Australia.

Further detections have occurred since in:

-  The Pilbara region of Western Australia

-  Throughout the entire Northern Territory

-  APY lands (Aṉangu Pitjantjatjara Yankunytjatjara) in northern South Australia

-  Cape York, Queensland

The most recent case, in December 2022, has been detected in a local dog of Townsville, Queensland, that had not travelled outside the area.  This means that the deadly bacterial disease has reached our local tick population of the North Queensland region.

Monitoring and action

Surveillance

Areas where the brown dog tick exists may pose a risk of ehrlichiosis to dogs.  Surveillance to determine the distribution of the brown dog tick and E. canis is continuing to help refine the area where E. canis is known to be active.

Movement conditions and obligations of dog owners

As a dog owner in Queensland, you have an obligation to be aware of and manage the risk of E. canis infection.

You should maintain your dog on an effective tick prevention and control program as discussed in the 'Prevention' section, avoid taking your dog into tick-infested areas as much as possible and regularly inspect your dog for ticks.

Even if you are taking these steps, if you are moving your dog from an area where E. canis is known or likely to be active you should assess your dog's health before entering or moving within Queensland.  If your dog has not been on a tick prevention program, is unwell, or you are unsure, seek veterinary advice.

People moving or bringing dogs from interstate or adopting rescue dogs should always ask questions about where the animal has come from, their history, their health status and what tick prevention they've been on prior to bringing them to Queensland or moving them within Queensland.

Checking dogs prior to movement will help ensure only healthy dogs are moved and E. canis is not introduced or unknowingly spread within Queensland.

Dog owners are requested to remain diligent in managing the risk of E. canis and remain vigilant to the signs of disease.

If you suspect the presence of this disease in any dog, you must report it to Biosecurity Queensland on 13 25 23 or contact the Emergency Animal Disease Watch Hotline on 1800 675 888.