The severity of the disease varies considerably among dogs. In infected areas in Northern Australia, disease has been reported in up to 100% of the dog population and up to 30% of these cases have been fatal.

Some dogs may become infected and never show signs of clinical disease (sub-clinical infection). These dogs can present a spread risk if they come into contact with brown dog ticks. Some apparently healthy infected dogs may also go on to develop the disease months or years later.

In dogs that develop the disease, ehrlichiosis can be roughly divided into early (acute) disease and long-standing (chronic) disease.

Acute ehrlichiosis develops approximately one to three weeks after the tick bite and typically lasts 2-4 weeks. While dogs’ benefit from treatment, some may appear to spontaneously recover. Of the dogs that appear to recover, many will remain infected without showing signs of disease. Some of these will go on to clear the infection and fully recover while others will subsequently develop the chronic form of the disease months or years later.

Chronic ehrlichiosis tends to be more severe, is often unresponsive to treatment and is frequently fatal. Even with intensive care in referral hospitals, the majority of dogs with chronic disease will not recover.

Signs of infection can include:

• fever
• lethargy
• weakness
• enlarged lymph nodes
• loss of appetite
• discharge from the eyes and nose
• spongy swelling of limbs or scrotum
• excessive panting or rapid breathing at rest
• bleeding disorders (spontaneous bleeding from the nose or gums, blood in faeces, urine or vomit, sudden lameness with swollen joints, pinpoint to widespread bruising on the skin and gums)
• pale or yellow gums and inner eyelids
• collapse and/or seizures

Dogs will usually have abnormalities on blood tests and the bacteria can be detected on a diagnostic test.

If you suspect ehrlichiosis in a dog, you have a legal duty to notify your suspicion within one working day by calling Local Land Services on 1300 795 299, or the Emergency Animal Disease Hotline 1800 675 888 or by contacting NSW Department of Primary Industries via animal.biosecurity@dpi.nsw.gov.au.

You should consult your veterinarian if you think your dog has ehrlichiosis to develop a risk management plan. This plan may include:

• Appropriate tick control for dogs travelling into areas where E. canis is known or suspected to occur. Note: adequate protection from E. canis generally requires a combination of products that your vet can recommend.
• Close monitoring of your dog for clinical signs and seeking prompt veterinary attention for diagnosis and treatment of E. canis.
• Ongoing appropriate tick control if your dog has originated from or travelled through an E. canis endemic area or if it has ever tested positive for E. canis, even if it is currently well.

Diagnostic testing of dogs from E. canis endemic areas prior to entry into NSW is recommended, even in apparently healthy animals. However, it is important to remember that a proportion of dogs that test negative will actually be infected and some of these dogs may go on to develop a chronic and fatal disease. It is therefore vital that any dogs relocating from E. canis endemic areas should be accompanied (where possible) by records of where the dog is from, its medical and travel history, and whether the dog has been on an effective tick prevention treatment whilst in high risk areas.

Infection with E. canis can mimic many other diseases so laboratory testing of unwell dogs is important in diagnosing canine ehrlichiosis. Testing should also be performed in apparently healthy or recovered animals being imported to NSW. Any dog that is diagnosed with ehrlichiosis is assumed to be infected for life whether they are showing signs of disease or not. There are currently no tests to indicate whether an apparently healthy dog is persistently infected or whether that dog is likely to develop disease down the track.

Your veterinarian will arrange for testing. Elizabeth Macarthur Agricultural Institute (EMAI), Woodbridge Road, Menangle NSW 2568. A specimen submission form must accompany specimens submitted to the laboratory. Please contact EMAI to arrange a courier or to obtain further advice, during business hours on 1800 675 623 or at laboratory.services@dpi.nsw.gov.au. Details on samples to collect can be found at https://www.dpi.nsw.gov.au/biosecurity/animal/humans/ehrlichia-canis/sample-submission-guidelines

Dogs become infected with E. canis after being bitten by an infected tick, and the bacteria passes into the dog’s bloodstream. E. canis is transmitted primarily by the brown dog tick (Rhipicephalus linnaei). This tick is widely distributed globally and is present in much of northern Australia including areas of Northern NSW.

Dogs do not transmit the disease to each other. The disease is maintained by a cycle of transmission between brown dog ticks and dogs. Dogs relocating from or moving through E. canis endemic areas are the most likely route of introduction of the disease to NSW.

While infected dogs do not transmit ehrlichiosis to people, in rare cases, infected ticks may transmit E. canis to people. See the Department of Health website for information on human health implications associated with ticks, as well as prevention, removal and first aid advice.

Prevention and treatment

There is no vaccine available for ehrlichiosis and it can only be prevented by controlling ticks on dogs. Any dog relocating from or travelling through an E. canis endemic area should be maintained on appropriate continuous tick control for the rest of its life to manage the risk of ongoing transmission in NSW. This usually requires a combination of products that can be recommended by your vet.

This is especially important if you live in an area with brown dog ticks. Depending on your specific circumstances, this may include:

1. Maintaining dogs on an appropriate tick control program – ask your vet for the most suitable product and application regime.
2. Avoiding taking dogs into tick-infested areas such as the bush where possible.
3. Inspecting dogs daily for ticks after being in tick-infested areas, paying particular attention around the head, ears, neck, belly, armpits, between their toes and around their mouth and gums) (Figure 2) and carefully remove any ticks. Your vet can advise on the best methods of tick removal. Keeping coats clipped short can help
4. Having any tick infestations in your house or yard managed by a pest controller.

Treatment of acute ehrlichiosis generally involves prolonged antibiotics, supportive care and hospitalisation. While this may be beneficial in hastening convalescence, it often fails to completely clear the infection. Any dog that is diagnosed with ehrlichiosis is assumed to be infected for life whether they are showing signs of disease or not. Chronic ehrlichiosis is usually non-responsive to therapy and animals are euthanised on welfare grounds or succumb to the disease.

Veterinary Laboratory Submissions

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