Canine ehrlichiosis, a tick-borne disease affecting dogs, has now been detected in Australia.
The mere mention of paralysis ticks is enough to strike fear into the heart of any pet owner, certainly for those on the east coast where there are localised areas of heavy infestations of the paralysis tick, Ixodes holocyclus. However, there is a new disease for dog owners to be concerned about – canine ehrlichiosis, which is carried by the brown dog tick, Rhipicephalus sanguineus.
Canine ehrlichiosis is caused by the bacterium Ehrlichia canis. After being bitten by an infected tick, the bacteria enter the host’s white blood cells and multiply rapidly. The first symptoms will start to appear around two weeks after being bitten. High temperature, decreased appetite and lethargy are common symptoms, with bleeding (e.g. nose bleeds) being a distinguishing symptom of this disease. As the disease develops, animals can experience weight loss, swollen limbs, breathing difficulties and sometimes blindness. As would be expected for a disease that attacks the white blood cells, its impact on the bone marrow can be fatal – not only are animals incapable of fighting off mild disease, but they can die from haemorrhaging or septicaemia.
Canine ehrlichiosis is known in the tropical parts of the world outside Australia, but was first detected in Australia in May 2020. Scientists aren’t exactly sure when it arrived in Australia, but from the level of infection in the tick population, they estimate several years. Although it was initially confined to dogs in Western Australia and the Northern Territory, infected ticks have now been detected in South Australia. Whilst the brown dog tick itself is normally confined to more tropical areas, there is evidence that it is spreading southwards in Australia, so the issue may become more widespread.
The disease is not infectious; dogs actually have to be bitten by an infected tick to get the disease. The potential for humans to also become infected from a tick bite is somewhat unknown. A similar disease, human monocytic ehrlichiosis (HME), is caused by a related bacteria in humans. Studies overseas have shown that some patients exhibiting HME were in fact infected with a strain of E. canis. Although native marsupials are not known to be impacted by this disease, there are concerns that it could have an impact on the dingo population.
The challenges in controlling the brown dog tick are different to the paralysis tick in that the brown dog tick is also well adapted to living inside buildings, even in cooler climates. So in addition to a veterinary-prescribed, on-pet treatment, pest managers have a role to play in providing tick treatments in affected areas.
Prevention is part of management. Ticks are typically brought into yards on native animals, so suitable fencing – preferably half buried to prevent bandicoot entry – is a good starting point. As ticks generally remain in the leaf litter when not attached to an animal, as it provides a warm humid environment, keeping the grass short and gardens well maintained will make this environment less attractive to ticks. A recently cut lawn is also important before treating the whole yard for ticks. Insecticides labelled for tick control will kill any ticks present and provide some residual protection. This action will take care of both paralysis ticks and brown dog ticks.
However, since brown dog ticks can quite happily become established inside buildings, pet bedding and resting areas need to be inspected. Pet bedding needs to be thrown out (preferably), washed in hot water or placed in a sealed plastic bag in the sun for many hours to kill any ticks or tick eggs on the bedding. Indoor areas need to be treated with a suitable insecticide – the young ticks will often hide in cracks and crevices such as between floorboards and along the edges of rooms. In severe infestations ticks can be seen crawling up walls!
Brown dog tick treatments are not going to be big business in the near future, but with the ticks on the move (along with the disease threat) much of the coastal fringe of Australia could be susceptible to increasing tick issues in the coming years.