Domestic dogs exposed to new disease outbreak

Person using tweezers to remove insects from dog

Dog owners in the north west of Western Australia, and throughout Australia’s north, are being warned to keep a look out for a disease inflicting the four-legged friends of human-kind.

Emeritus Professor in the School of Veterinary Medicine at Murdoch University, Peter Irwin said while Australians’ minds are occupied with the ongoing coronavirus pandemic, another disease has emerged which is cause for considerable alarm for dog owners.

This disease – canine ehrlichiosis – is caused by a bacterium called Ehrlichia canis (E. canis) transmitted specifically via a bite of the brown dog tick, an arthropod parasite which is widespread in warm and humid areas of Australia.

Canine ehrlichiosis is a life-threatening disease for dogs,” Professor Irwin said. 

“Until the first cases were discovered, the Australian continent was considered free of the disease.

“Every pet owner who has travelled into Australia with their dogs would know about the stringent testing procedures in place to ensure their canine companions do not bring canine ehrlichiosis, or other diseases, into the country. 

“It is one of only a few diseases dogs are screened for prior to their arrival from other countries.”

Dr Charlotte Oskam, senior lecturer and team leader of the Vector and Water-Borne Pathogens Research group at Murdoch University said in addition to the border controls, Australia’s island status has provided a further, physical barrier to the establishment of canine ehrlichiosis. 

“As with other serious animal diseases such as African Swine Fever and Screw Worm Fly, for which there is constant surveillance by biosecurity authorities, E. canis is highly prevalent in tropical regions, including our closest northern neighbours,” Dr Oskam said.

“However, research we have previously conducted has shown a southwards expansion of the brown dog tick’s geographical range. 

Worse, it is also adapted to indoor living and readily establishes within kennels or homes, and even in cooler climates.

“The conditions are favourable in Australia for E. canis to spread to most parts of the country.”

Professor Irwin said the response by the state and Commonwealth veterinary authorities to the outbreak of canine ehrlichiosis has been swift. 

“It is a notifiable disease in Australia so all new cases must be reported immediately – though it is not notifiable in other countries,” Professor Irwin said.

“The disease, which is diagnosed using blood tests conducted by state and federal veterinary laboratories, is treated with antibiotics and other supportive measures, and most dogs will improve, however some may develop a chronic infection that usually has a terminal outcome.

“In terms of safeguarding your pets, dogs that don’t get bitten by ticks will not contract the disease, so it is vital that animal owners Australia-wide are proactive with the application of parasite prevention for their dogs.”

Dr Oskam said since the first cases of canine ehrlichiosis were diagnosed, questions have been raised about how the disease arrived despite Australia’s strong border controls.

“There are legitimate questions about how the infection entered Australia,” Dr Oskam said.  

“Was it carried in undetected by a dog travelling from an endemic country, or did contaminated ticks arrive from overseas? Was there an incursion from a neighbouring country to the north? If this were the case, there are implications for other, potentially far more serious diseases such as rabies, entering onto the Australian continent in a similar manner.

‘The discovery of E. canis in dogs in Australia is a reminder of the importance of quarantine measures to protect our pets, just as we take such measures seriously for the protection of humans,” Dr Oskam concluded.

Background on E. canis

The disease first came to the attention of veterinary scientists on a global scale in the 1960s-1970s after affecting scores of military working dogs, often German Shepherd dogs, in southeast Asia during the Vietnam War.

After being injected into dogs by the tick, E. canis enters white blood cells and multiplies rapidly, causing signs of illness that are only first noticed by the owner about two weeks after transmission.

The disease is characterised by fever, decreased appetite, lethargy, and bleeding tendencies, such as nose bleeds. Some dogs develop severe and rapid weight loss, swollen limbs, difficulty in breathing, blindness and neurological signs.

One of the most serious effects of this disease in the canine patient is on the bone marrow, where blood cells are made, with a frequently fatal outcome. Some dogs die of septicaemia as they can no longer fight off even the most innocuous of infections, or they bleed uncontrollably.

Posted on:

27 Nov 2020



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