Everything You Need To Know About Ehrlichiosis

The Tick-Borne Disease Emerging in Australia


This article is written by Pet Circle veterinarian, Dr Carla Paszkowski BVSc (Hons)

In May 2020, a few dogs in the Kimberly region of northern Western Australia were confirmed to be infected with a microbe called Ehrlichia canis. The disease has since extended to other parts of Australia and is being investigated by the Department of Primary Industries and Regional Development in West Australia and Northern Territory.

This is the first time Ehrlichiosis has been detected in dogs in Australia that have not been imported. Until May, Australia was generally considered free of the disease. Understandably, such an outbreak has sparked a great deal of concern among authorities, vets, and pet owners alike.

Skip To A Section:
Transmission: How Do Dogs Catch Ehrlichiosis?
What are the signs of Ehrlichiosis?
Can Cats Catch Ehrlichiosis?
Distribution: Where in Australia is Ehrlichiosis?
Prevention: How to protect your pet from Ehrlichiosis
Reporting Ehrlichiosis and Further Links

Dr. Carla discusses Ehrlichiosis in Dogs with Bill McDonald on 4BC Brisbane Radio, 24th Feb 2021. View more here.

How is Ehrlichiosis Transmitted?

Light micrograph of Ehrlichia canis, inside a white blood cell. Photograph provided by Profa. Dra. Machado, R. Z.

Ehrlichia canis is a small rickettsial organism (a type of bacterium) that lives within the cells of a host animal. Ehrlichiosis is also called 'tracker dog disease' or 'tropical canine pancytopenia' because of its original presentation in military dogs from Vietnam.

Transmission occurs when an infected tick bites your dog. The species of tick that transmits E. canis is the brown dog tick (Rhipicephalus sanguineus), which is widespread in Australia. Although brown dog ticks are generally associated with tropical and subtropical environments, they can complete their life cycle indoors. This allows them to potentially survive in colder climates, like those in southern regions.

The Brown Dog Tick (Rhipicephalus sanguineus). Source DPIRD WA.

A brown dog tick may become infected after feeding from an infected dog, and the tick may remain infectious for up to 5 months. Any species of dog from the family Canidae may maintain the cycle between ticks and dogs - including domestic dogs, foxes, and dingos.

Infected dogs do not directly transmit the disease to other dogs. Nor can they transmit the disease to humans or cats. Humans can theoretically become infected if they are bitten by an infected tick - but this is very rare.

What are the Signs of Ehrlichiosis?

Ehrlichiosis has three phases, as outlined below:

1. 'Acute' phase - where initial signs of infection are vague and may last 2-4 weeks.

2. 'Subclinical phase' - where there are no obvious signs of disease. The subclinical phase can last for months to years, and dogs may recover, remain infected without symptoms, or move to the chronic stage.

3. 'Chronic phase' or long-term stage, which involves similar signs to the acute phase but in a more severe presentation.

Photo: Nosebleed in an infected dog. Dr John Beadle, All Creatures Veterinary Clinic, Broome

This disease has a fairly high mortality rate, and is particularly deadly to younger or older dogs that are immunocompromised.

German Shepherds are particularly susceptible to the chronic phase and tend to develop a severe haemorrhagic condition known as tropical canine pancytopenia, which is often fatal.

Can Cats become infected with Ehrlichia canis?

In cats, symptomatic disease caused by E. canis is extremely rare, and as yet has not been reported in the current Australian outbreak. Cats are not the primary host for this organism, and disease is therefore uncommon. But infection in cats may be possible if they are bitten by an infected tick, so up-to-date tick prevention is still recommended for cats in high-risk areas.

Distribution of Ehrlichiosis

Where in Australia is this tick-borne disease found?

West Australia: Most heavily affected. According to the Australian Government's Outbreak Website, Ehrlichiosis has been confirmed in dogs in the north of Western Australia including:
- Halls Creek
- Kununurra
- the Kimberley regions of Broome and Derby
- The Pilbara regions of South Hedland and Port Hedland

Northern Territory: Heavily affected. Ehrlichiosis has also been confirmed in dogs in the Northern Territory town of Katherine, and a remote community west of Alice Springs.

South Australia: Affected In January 2021, laboratory tests confirmed the presence of E. canis in ticks collected from dogs in the far north regions of South Australia. Currently, areas of concern include those north of Port Augusta and throughout the APY (Aṉangu Pitjantjatjara Yankunytjatjara) lands.

Queensland: Affected A Queensland dog tested positive in July 2021 after travelling through Western Australia and the Northern Territority. In early 2022 a dog tested positive for Ehrlichiosis in northwest Queensland. Concerningly, this dog had not travelled outside the state - leading veterinarians to suspect this was a locally acquired case.

New South Wales: Low risk E. canis has not been detected in dogs originating in NSW. However, three dogs that were brought into NSW from the Northern Territory tested positive for E. canis and are under veterinary supervision.

During this current outbreak, Ehrlichiosis has not been reported in Victoria, Tasmania, or ACT.

Prevention: How To Keep Your Pet Protected

It is recommended that all pet parents in affected regions stay vigilant. To prevent your pet from getting Ehrlichiosis, take the following steps:

1. Keep your pet on tick prevention (see below for our top recommendations)

2. Complete regular tick searches on your pet. This involves running your fingers through your pet's coat, feeling the skin for small bumps. Pay particular attention to the head, neck, ears, chest, lips, eye folds, and between the toes.

3. If you are travelling to an affected area, be particularly careful around tick infested environments such as bush and long grass.

4. Contact a vet if your dog is showing signs such as lethargy, fever, enlarged lymph nodes, reduced appetite, discharge from the eyes or nose, nosebleeds, or spots on the skin.

Is there a vaccine for Ehrlichiosis?

There is no vaccine for this tick-borne disease, but antibiotic treatment may prove curative if the dog is treated early enough. Chronic, severe, or complicated cases may need a long treatment course and the dog may never fully recover. Tick prevention is the main protective measure against this disease.

Tick prevention is the number one way to keep your pet safe from this tick-borne disease. Because it only takes a short time for the tick to transmit Ehrlichia canis, external prevention which repels ticks before they can bite your dog are preferred over internally-acting treatments which requre a tick to bite in order for them to work. It's important to remember that tick treatments work in different ways - ie. oral treatments and many topical liquids work by being absorbed into your pet's bloodstream, which requires the tick to attach and feed off your pet in order to take effect.

However, if you are in a high-risk area, we recommend doubling up your protection by teaming the Seresto collar with a systemic tick treatment such as Bravecto, Nexgard Spectra, or Simparica. There is no risk of adverse effects when combining Seresto and a systemic treatment.

Tick treatments that work EXTERNALLY to repel ticks

- Seresto - registered to reduce transmission of E. canis
- Advantix

Tick treatments that absorb SYSTEMICALLY, requiring a tick bite

- Bravecto spot on and oral chew
- Nexgard and Nexgard Spectra
- Revolution Plus
- Simparica

Reporting and Relevant Links

If you suspect your dog has Ehrlichiosis, go to your vet for an examination. Ehrlichiosis is a nationally notifiable disease which means that incidences must be reported to the Emergency Animal Disease Watch hotline on 1800 675 888.

Media Release: Ehrlichiosis Confirmed in dogs in the Kimberley

National Pest & Disease Outbreaks: Current Situation of Ehrlichiosis

Department of Primary Industries and Regional Development, WA - Ehrlichiosis factsheet

Queensland Government Business Queensland - Canine ehrlichiosis factsheet

Information for Moving Animals

This animation on Canine ehrlichiosis has been developed by AMRRIC.