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Canine ehrlichiosis

Alert

Infection with Ehrlichia canis is a nationally notifiable disease.

E. canis, the causative agent of canine ehrlichiosis, was detected in a small number of domesticated dogs in the Halls Creek and Kununurra area in May 2020. This was the first detection of E. canis in Australia. Further detections have occurred in the Pilbara region of Western Australia.

E. canis was subsequently confirmed in domesticated dogs in Katherine, a community west of Alice Springs in the Northern Territory in June 2020.

E. canis has not been detected in Queensland

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

Canine ehrlichiosis is a tick-borne disease of dogs caused by infection with the bacteria Ehrlichia canis. Dogs become infected with E. canis after being bitten by an infected tick, primarily the brown dog tick (Rhipicephalus sanguineus).

Ehrlichiosis is an intracellular bacterial infection that primarily infects the cells of the immune system. Infected dogs can present with a range of clinical signs.

Scientific name

Canine ehrlichiosis

Cause

The bacteria Ehrlichia canis

Other names

  • Canine monocytic ehrlichiosis
  • Canine tropical pancytopenia
  • Tracker dog disease
  • Canine haemorrhagic fever
  • Canine typhus

Distribution

Ehrlichia canis is found in most of the world and follows the distribution of the vector, the brown dog tick Rhipicephalus sanguineus.

The distribution of E. canis in Australia is being investigated following the detection of E. canis in Western Australia and in Katherine, a remote community west of Alice Springs in the Northern Territory.

Hosts

Dogs and other canids are considered to be the reservoir hosts.

Infected ticks, primarily the brown dog tick (Rhipicephalus sanguineus), are vectors for E. canis infection between dogs.

Life cycle

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

Affected animals

  • Domesticated or wild animals in the family Canidae including dogs and foxes

Symptoms

Disease phases

Canine ehrlichiosis has 3 disease phases:

  • acute
  • subclinical
  • chronic.

The severity of clinical signs can vary considerably among dogs.

The incubation period for the development of acute disease is about 1–3 weeks although the chronic form may not show any clinical signs until months or years after infection.

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. This phase typically lasts for 2–4 weeks.

Subclinical phase

Some dogs that recover from the acute phase can become subclinically infected. There is also a subset of dogs that show mild or no early clinical signs, but are subclinically infected. This phase can persist for months to years.

Subclinical dogs either:

  • clear (get rid of) the organism
  • 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
  • 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.

Diagnoses

Ehrlichiosis is diagnosed through a combination of:

  • consistent clinical signs
  • blood tests.

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

Read more detailed information for veterinarians on Ehrlichia canis.

How it is spread

Transmission between dogs and other canids

Transmission between canids requires the tick vector. Canids become infected with E. canis after being bitten by an infected tick. Canids may also become infected through blood transfusions.

As E. canis is not naturally directly transmissible between dogs, possible pathways for its spread include movement of:

  • actively infected vectors that may infect naïve dogs (dogs that haven't been exposed to the bacteria before) in new locations
  • acutely infected dogs that infect naïve tick populations in new locations
  • chronically infected dogs that infect naïve tick populations in new locations.

Transmission to humans

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

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 will help refine the risk area. This website will be updated as more information becomes available.

Movement conditions and obligations of dog owners

If you are moving dogs from the Western Australian local government areas of Broome, Derby-West Kimberley, Halls Creek and Wyndham-East Kimberley, dog movement conditions apply. Contact DPIRD for more information on dog movement conditions.

There are currently no movement controls of dogs to Queensland from the Northern Territory; however, as a dog owner in Queensland, you have a general biosecurity obligation to be aware of and manage the risk of E. canis infection. Managing the risks may include effective tick control and treating infected dogs. It may also include not moving clinically consistent dogs from the Northern Territory or Western Australia into Queensland.

E. canis has not been detected in Queensland. Dog owners are requested to remain vigilant and if you suspect the presence of this disease in any canid, you must report it to Biosecurity Queensland on 13 25 23 or contact the Emergency Animal Disease Watch Hotline on 1800 675 888.

Control

Prevention

To help prevent disease in dogs from ticks:

  • maintain an effective tick control program
  • avoid taking dogs into tick-infested areas, such as the bush, as much as possible
  • inspect dogs for ticks after being in tick-infested areas and carefully remove any ticks.

Veterinarians can provide advice on tick control programs, products and tick removal.

Treatment

In addition to removal of ticks and applying an appropriate tick control program, E. canis infections in dogs may be treated by antibiotics. In some cases, supportive therapy and hospitalisation may be necessary. Early treatment provides the best chance of recovery.

Further information