Parasitic Zoonoses – Beware the flea!

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This article is sponsored content brought to you by Boehringer Ingelheim.

Pets are an important part of many Australian households. Whilst the benefits of pet ownership for mental and physical wellbeing are well recognised, increased pet ownership and changing dynamics of human-animal interactions may result in an increase in opportunities for transmission of zoonotic disease as dogs and cats may carry a range of different zoonotic organisms, including parasites. 

Throughout history fleas have wrought destruction on societies disproportionate to their physical size through their role as biological and mechanical vectors for several important pathogens. The classic example is plague (“Black Death”), caused by Yersinia pestis, responsible for killing approximately one-quarter of the population of Europe in the Middle Ages. Whilst Australian veterinarians and pet owners need not be concerned with fleas transmitting plague, in Australia fleas may transmit organisms such as Bartonella henselae, the causative agent of cat-scratch disease and Rickettsia felis, the causative agent of flea-borne spotted fever (FBSF, also known cat flea typhus). 

Rickettsia felis is an emerging zoonosis throughout many regions of the world. Like other rickettsial organisms it has a lifecycle involving a reservoir host in which the organism multiplies and is maintained, and vector species via which the organism is transmitted horizontally to new hosts. Dogs are thought to be the primary reservoir host and fleas, specifically the ubiquitous cat flea (Ctenocephalides felis), the primary vector. Infected dogs and cats usually show no clinical signs and are not a direct source of zoonotic infection. What really matters then is the prevalence of R. felis in fleas, which in Australia have been reported as high as 19.8% in eastern Australia and up to 36% in regional centres in Western Australia. 

Humans may be infected with R. felis through the bite of an infected flea. The clinical signs associated with infection include fever, muscle and joint pain, skin rash, and fatigue, although infection may be associated with no clinical signs. The disease course can be long, and in some cases can result in ongoing illness. Occasionally more severe manifestations, including neurological and multi-systemic disease, have been recorded. 

Regular exposure to fleas may be an occupational hazard for veterinarians, with an Australian study finding 16% of veterinarians positive for R. felis exposure, 4.6% for another rickettsial species (R. typhi), and a further 35.1% positive for rickettsial exposure, but unable to be differentiated to a single species. Interestingly, in this study veterinarians who reported that they recommended flea control measures to their clients had a statistically significant reduction in the risk of exposure to R. felis

Companion Animal Zoonoses Guidelines – Managing the risk 

In 2020, Boehringer Ingelheim brought together a panel of veterinary and human infectious disease experts (the Australian Companion Animal Zoonoses Advisory Panel) to review and discuss the latest research and make evidence-based recommendations around the control of zoonotic diseases associated with dogs and cats. The resulting guidelines were released in June 2021 and cover 19 important potentially zoonotic pathogens, providing recommendations and strategies to minimise the risk of zoonotic disease transfer from dogs and cats in the veterinary clinic and community setting. When considering the risk of zoonoses from parasites, key panel recommendations include the year-round use of ectoparasiticides (effective against fleas and mites) as well as monthly deworming.

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To download a copy of the Companion Animal Zoonoses Guidelines, go online to www.animalhealthacademy.com.au and sign in. If you don’t already have an account, it is simple to create one using the access code: myAcademy. 

Click on “Guidelines” in the menu bar and then select “Companion Animal Zoonoses”. 

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