Emerging Disease - EHRLICHIOSIS IN DOGS

Ehrlichiosis is a tick borne disease affecting primarily dogs. It is not transmitted from dog to dog, transmission only occurs through infected ticks, the main one being the brown dog tick.

The brown dog tick is widespread throughout mainland Australia. No brown ticks have been found in Tasmania. While ticks are mostly coastal, they can be found further inland.

Ehrlichiosis is the disease that is caused by a tick borne bacteria called Ehrlichia Canis. Once a dog has been bitten by an infected tick, there are 3 stages of infection: -

1. Acute or early phase (3-4 weeks)
2. A subclinical phase (months to years)
3. Chronic or long term stage. (months to years)

Symptoms include fever, lethargy, enlarged lymph nodes, loss of appetite, discharge from the eyes and nose, weight loss, anaemia and bleeding disorders such as nosebleeds or bleeding under the skin that looks like small spots, patches or bruising.

The severity of symptoms varies considerably between dogs. The incubation period is 1-3 weeks after the tick bite, but the chronic form may not manifest for months or years following infection. PCR and ELISA tests give the most accurate diagnosis along with comprehensive blood tests. Affected dogs require veterinary treatment and supportive care, the earlier this is diagnosed and treated the better. Usually these dogs are treated with tetracycline drugs for a minimum of 4 weeks, shorter treatment periods may result in subclinical carriers. Seronegative PCR tests will indicate if the infection has cleared.

If not properly treated these dogs can and do die.

Distribution

This disease can be found worldwide, particularly in tropical and subtropical areas. Once the disease is in the brown dog tick population, it is very difficult to control. German Shepherds and Siberian Huskies are predisposed to develop more severe signs of disease with a worse prognosis (reduced cell-mediated immune response).

In extremely rare cases, infected ticks may infect people, however the species of Ehrlichia that affects humans have not yet been detected in Australia.

Ehrlichosis is a nationally notifiable disease and the Government is conducting surveillance testing of dogs, particularly in the far north of Western Australia, Northern Territory and far north Queensland. The Kimberly and Pilbara regions are two areas affected in WA, along with Katherine and Alice Springs in the NT.

Dogs from affected areas are being monitored and their movement limited. Dogs moving from these areas could be required to be tested prior to movement and only travelling with healthy dogs that are on an effective tick control program.

Prevention

Maintain dogs on a tick control program – ensure you do not run over time before treating again, even 2-3 days late could cause issues.

Avoid taking dogs into tick infected areas such as the bush and long grass, especially on coastal areas.

Inspect you dogs for ticks daily for 5-6 days after being in tick infested areas.

Travelling

The most likely way this disease will spread is by the transport of dogs interstate. Dog exhibitors like to travel far and wide for shows, often interstate. We should all be vigilant with providing tick control measures and renewing these before we travel!

Do not take dogs running along beaches, through the bush etc without adequate tick prevention. Be aware at some shows, the grounds may back onto bush, do not walk your dogs through these areas.

Long Term

We have to be aware that this disease will in all probability become far prevalent and widespread over the next 10 years. Tick prevention should become second nature especially when travelling.

Dr Karen Hedberg BVSc
ANKC Canine Health & Wellbeing Committee Chairperson
16 July 2021