Mostly, when writing these posts – I discuss current common medical conditions. Ehrlichiosis is not one of those.
This is different.
It is uncommon.
Its spreading slowly south and Queensland is definitely in the firing line.
Late last year I attended a briefing by Australian veterinary pathologists and government veterinarians concerning a newly detected disease in Northern Australia. Canine Ehrlichiosis is a bacterial parasitic disease spread by the Brown dog tick. It is endemic in most other continents and it was detected in Australia in the first half of 2020.
Common tick preventatives do not prevent infection.
It is important that all dog owners understand the risk and the options they have for prevention.
If all this is too much to read…
What is Canine Ehrlichiosis
Canine ehrlichiosis is caused by the bacteria Ehrlichia canis, which is transmitted by Rhipicephalus sanguineous, commonly known as the brown dog tick. As its name suggests, the tick prefers to dine on dogs; other animals, including humans, are far less prone to infection. The infection is spread by an infected tick and thus we class it as a vector borne disease; it doesn’t pass directly from dog to dog. It falls into a category of diseases known as arthropod – borne disease. Other examples of human diseases in this category are:
- Lymes Disease (bacteria)
- Rocky Mountain spotted fever (bacteria)
- Ross River Virus (virus)
- Dengue Fever (virus)
- Malaria (not bacterial or viral – parasitic cell)
Zoonotic (Can it infect humans)
Little is known about the zoonotic potential of E. canis, though one study(link) in 2006 found that it had sickened a handful of people in Venezuela. Experimentally infected Rhesus monkeys exhibited severe signs of infection.
The infection usually has three phases: acute, subclinical and chronic.
Clinical signs arise one to three weeks following the bite of an infected tick, and may include :
- loss of appetite,
- enlarged lymph nodes ( thse are your immune system glands)
If treated during the acute phase most dogs recover, but if untreated or inadequately treated, they may enter a subclinical phase in which they appear normal.
This phase can last months or even years the bacteria hides away in the spleen.
Dogs may not ever progress to the chronic phase. However, if they become sick again – signs include:
- severe fever
- inflammation in the eyes
- abnormal bleeding
- including from lesions on the skin
- and nose bleeds.
- including from lesions on the skin
Diagnosis is made by detecting genetic material of the bacteria (with a polymerase chain reaction, or PCR, test) or by detecting antibodies in the patient’s blood (through serology). We can take a sample for testing here at the clinic and have access to a wide range of laboratories offering different testing options for our pets.
How far has ehrlichiosis spread – should we be worried?
A veterinarian, located in the far north of Western Australia, initially detected the disease. They noted clinical signs in a few dogs that were not consistent with common diseases. A pathology lab received samples and the bacteria was identified during pathological screening. Once that had occurred more cases were identified in the Northern Territory. Last month a case was identified in South Australia and New South Wales has identified several dogs as well. There were dogs moved from the Northern Territory into Queensland prior to diagnosis. The disease has thus been recorded in 5 States or Territories of Australia. It should be expected to spread to any area that the Brown Dog Tick is endemically embedded.
There has been surveillance testing conducted in Western Australia and the Northern Territory – with many vets sending samples in of sick dogs. Of 867 dogs sampled so far in Western Australia and the Northern Territory, 323 have tested positive for the disease, with a mortality rate of about 10%, according to a spokesperson for Australia’s federal agriculture department.
Is Ehrlichiosis likely to Spread further?
E. canis had been endemic in parts of every continent except Australia for the past 80 years. The pathogen was first identified in the 1930s by French scientists in Algeria. Coming to prominence in the 1960s and 1970s after it killed scores of American military dogs serving in the Vietnam War.
The brown dog tick, preferring warmer climates, is more likely to flourish in tropical and subtropical regions. However Irwin thinks it’s only a matter of time before canine ehrlichiosis becomes more widespread in Australia. Australia has quite a varied climate but the adaptability of the tick leave the potential for the disease to crop up in big cities such as Sydney, Brisbane and Perth, where brown dog ticks are present in small numbers.
“Movement of aimals and the fact that the tick itself is very adaptable — it enjoys living in urban dwellings that can be well outside its tropical range — are factors that will lead to the slow and steady dissemination of this disease around the country,“Dr Peter Irwin
Over the longer term, climate change is likely to play a role expanding the ticks’ preferred habitat. Increasingly warm environments will expand the range of the vector, the Brown Dog tick.
The biggest factor that will slow the spread is the use of preventatives. There are communities in Queensland where there is a low socioeconomic index combined with high unemployment lead to a very low compliance with any sort of tick control. Many of the dogs will carry ticks year round. The nature of the disease having a very long sub clinicial period means theses animals are the perfect vector.
How did this happen?
Australia’s Bio-security has been considered somewhat of a fortress comparatively to other countries, with many relying on our excellent record and using us as a check point for themselves. e.g. Vanuatu and other pacific islands. If we cannot identify to entry point then we may not be able to maintain our disease free status for other canine diseases. There are theories, none of which currently have any solid evidence. This leads to the 2nd important but related reason best voiced by Dr Irwin:
“This outbreak of ehrlichiosis has heightened everyone’s nervousness about rabies, If an infected dog had somehow eluded testing with ehrlichiosis, it’s theoretically possible that the same thing could happen with rabies, which is dangerous to humans.”Dr Peter Irwin – referring to another lethal disease that has never been detected Down Under. (Others include foot-and-mouth disease and avian influenza).
Hopefully with genetic analysis we can at least identify the potential source and look to better control that entry point.
How do we prevent it?
Currently in Brisbane most vets and Pet stores will recommend you use products like Bravecto, Nexgard and Simparica. These products are examples of a tick and flea control product that circulate in your dogs blood stream killing any flea or tick that feed on the dog in a matter of hours. It has worked very well, causing the number of real cases of Paralysis tick envenomation in our area to reduce by a huge factor and we rarely see cases of severe flea infestation any more. These products do also kill Brown Dog tick and will slow the spread of ehrlichiosis but they do not prevent infection in your dog.
HOWEVER they will not prevent your dog becoming infected if an ehrlichiosis infected tick was to bite your dog.
I am not trying to be sensational or cause panic, nor am I suggesting you rush out and change your preventative.
Currently the use of repellents and on-contact acaricidal (tick lethal) products is the recommended way to prevent infection (ehrlichiosis) on an individual animal.
Below is a summary table of some of the Products and the relative efficiency at preventing ehrlichiosis.
|Speed of Kill
(Imidacloprid / flumethrin)
|>90% after 12 hours
assume as per nexgard.
Continue to use your current tick preventative. The most important disease to prevent in Brisbane is still Tick Paralysis. That being said – the common preventatives, Bravecto, Nexgard and Simparica only prevent 40-70% of infected ticks from passing on the infection. This is because they require the tick to feed on your pet to work.
If you are travelling north into country that might have large feral or wild dog populations, or possible areas where compliance is lower – consider fitting a Seresto collar to your pet before travelling (at least a week prior). Alternatively use any other preventative that acts as a repellant or on contact tick killer.
IF you are concerned that your pet may have already been exposed or has lived in one of the endemic areas in the past consider calliing us and getting them tested.
Comparative efficacy of oral administrated afoxolaner (NexGard™) and fluralaner (Bravecto™) with topically applied permethrin/imidacloprid (Advantix® ) against transmission of Ehrlichia canis by infected Rhipicephalus sanguineus ticks to dogs (Funded by Bayer)
A further article (Imidacloprid 10 % / flumethrin 4.5 % collars (Seresto®, Bayer) successfully prevent long-term transmission of Ehrlichia canis by infected Rhipicephalus sanguineus ticks to dogs) details how effective one particular tick collar is.