Ehrlichia canis information for veterinarians

Assessment of suspect infections

If you suspect E. canis (the causative agent of canine ehrlichiosis) infection in a dog, it is important to seek epidemiological and clinical information about the likelihood of E. canis infection to inform diagnostic and treatment priorities. The specimen advice sheet – Ehrlichia canis supplement should be used as a guide for information collection.

High-priority cases

Based on the epidemiological information provided, a likelihood assessment will inform high-priority cases. High-priority cases will be of dogs with any of the following:

• living in northwest, north or far north Queensland (particularly the local government areas of Mount Isa, Cloncurry, Carpentaria, Doomadgee, Mornington, Kowanyama, Townsville, Hinchinbrook and Mareeba)
• a travel history from northwest, north or far north Queensland, the Northern Territory, the Kimberley, Pilbara, Gascoyne and northern Goldfields regions of Western Australia, or Port Augusta or northern South Australia
• a travel history from areas where E. canis is likely, but not confirmed, to be active
• a history of tick-borne related disease
• a history of a blood transfusion
• a history of clinical disease consistent with E. canis
• pyrexia of unknown cause and thrombocytopaenia (as priority indicators).

Cases determined to meet the above criteria should be notified to Biosecurity Queensland on 13 25 23 or the Emergency Animal Disease Hotline on 1800 675 888, and samples submitted directly to the Biosecurity Sciences Laboratory (see 'Where to submit samples' below).

Moving dogs within or into Queensland

Before moving dogs within or into Queensland from areas where E. canis is known to be active, the likelihood of E. canis infection should be assessed by the dog owner, dog carers, person(s) in charge of the dog or managing the movement of the dogs, and/or a registered veterinarian.

Key criteria for assessment are:

• the health status of the dog
• the dog's medical history
• the dog's life history
• whether the dog has been on an effective tick preventative
• whether the dog has been present in areas where E. canis is known to be active
• whether the dog has been present in areas where E. canis is likely to be active, but which is yet undetermined
• whether the dog has had close contact or is a cohort of a dog which has a confirmed or suspected case of E. canis.

Veterinarians may be asked by dog owners for advice around mitigating the risk of their dog becoming infected or preventing disease spread. Advice will vary from general advice to advice associated with travelling. It may include:

• undertaking a thorough veterinary clinical examination
• undertaking diagnostic testing for clinically consistent dogs
• inspecting dogs and cohorts for ticks regularly, with removal of any ticks
• maintaining the dog on an effective tick prevention and control program, including use of external tick controls that kill ticks on contact
• avoiding taking dogs into tick-infested areas (e.g. the bush)
• for dogs originating from known-infected areas and travelling into or within Queensland:
  • undertaking a complete blood count and/or diagnostic testing prior to travel, with negative results before travel
    • observation that the dog is, and remains, clinically healthy between the time of testing and travel
    • isolating dogs from other dogs and tick vectors commencing at the start of a testing regime.

Veterinarians can discuss risk mitigation measures with a Biosecurity Queensland veterinary officer by contacting the Customer Service Centre on 13 25 23.

Where to submit samples

Submit samples from high-priority cases directly to the Biosecurity Sciences Laboratory (BSL), including the specimen advice sheet (Form A) (PDF, 188KB) and the specimen advice sheet—Ehrlichia canis supplement. Samples can also be submitted for travelling dogs where it is considered necessary to confirm their infection status before travel.

E. canis testing of healthy dogs, or ticks from healthy dogs, prior to movement, or for any other reason, will incur a laboratory fee.

Testing of dogs showing signs clinically consistent with E. canis are performed as disease investigations at no charge but wider diagnostic testing will not be undertaken. Submit additional samples to your preferred commercial veterinary laboratory if wider diagnostic testing is required.

Samples from lower priority cases, where E. canis infection forms part of a range of differential diagnoses, should be submitted to your preferred commercial veterinary laboratory. Where E. canis infection is to be ruled out, samples will be referred from the commercial veterinary laboratory to the BSL for fully subsidised E. canis testing.

Samples required

The required samples from live or recently deceased/euthanased animals are:

• blood
  • 2-5ml in an EDTA tube (purple top)
  • 2-5ml in a plain tube (red or grey/red speckled top). If possible, a 1–2ml aliquot of clear serum should be obtained
• ticks collected from the affected dog and placed in 70% ethanol or 40% propylene glycol.

Samples to collect from dead animals are:

• unclotted heart blood (if available)
• fresh samples of lung, spleen, liver, kidney, and submandibular lymph node, in separate screw-top containers, and a range of formalin-fixed tissues
• ticks collected from the affected dog and placed in 70% ethanol or 40% propylene glycol.

Tick collection kits

Tick collection kits have been distributed to a number of Department of Agriculture and Fisheries (DAF) offices and veterinary practices in Queensland. You can also request kits through the Customer Service Centre on 13 25 23 or directly from the Biosecurity Sciences Laboratory.

Alternatively, ticks may be submitted in 5ml tubes with 2.5ml of 70% ethanol along with other diagnostic samples if transporting by road. Ethanol cannot be transported by air or through Australia Post.

Laboratory diagnosis

E. canis can be detected by real-time polymerase chain reaction (PCR). Serological tests include enzyme-linked immunosorbent assay (ELISA) and an indirect fluorescent antibody test (IFAT). The ELISA is the standard serological test and, along with the PCR, is conducted at the BSL.

Application of the following diagnostic interpretation matrix to the PCR and ELISA results will assist in determining a dog's infection status.

Treatment

To prevent onward transmission, dogs known or suspected to be infected with E. canis should immediately be treated with a registered acaracide. Topically acting products that repel and kill are recommended. Treatment of the dog's home environment should also be advised.

Doxycycline at 10mg/kg PO SID (or 5mg/kg BID) for 28 days is the recommended treatment for acute and chronic ehrlichiosis.

Consider supportive treatments and management of immune complex pathology or comorbidities, as appropriate.

Also consider

• Read the Canine monocytic ehrlichiosis - A guide for veterinarians.
• Read the Ehrlichiosis: additional veterinary guidelines for managing CME in Australia.
• Read the canine ehrlichiosis disease overview.