21 Jul 2020
Ticks and tick-borne diseases are becoming an increasing problem for humans and animals.
The prevalence of ticks is increasing globally, resulting from climate change, urban sprawl, pet transportation, bird migration, and increasing host numbers (such as in deer).
Not only are tick numbers increasing, but the “season” is longer, and ticks are now found in new areas and even new countries.
Ticks are most commonly found on animals and people that spend time outdoors – for example, fishing, camping, farming, forestry, walking and playing. However, they can also be found in urban locations, and some can live and thrive indoors1-3.
Ticks can carry many zoonotic organisms (bacteria, protozoa and viruses) that can infect humans and animals – the only vector that can carry and transmit more pathogens is the mosquito4.
The prevalence of tick species in the UK is changing rapidly, along with increased human and pet travel, and the importation of ticks on animals into the UK1.
To the frustration of many veterinarians and public health officials, the pet passport scheme no longer requires anti-tick treatment for travel into the UK (since January 2012)5.
Not surprisingly, between 2010-16 Public Health England’s Tick Surveillance Scheme documented 399 imported ticks on animals from 15 countries (for many reasons this is an underestimate)6.
Tick species and the type of pathogens they carry varies geographically. For example, the prevalence of Borrelia burgdorferi (the organism that causes Lyme borreliosis) in ticks on cats and dogs in the UK is approximately 2% overall; however, in certain areas of the UK, the prevalence of B burgdorferi in ticks is as high as 67%2,7,8.
Dog owners are usually aware of the risk of ticks, so they check their dogs regularly. However, few people are aware of the risk of ticks to their cats; therefore, cats often go unchecked.
Additionally, while dogs in the UK are most commonly bitten by Ixodes ricinus (the deer tick), with the adult ticks being easy to see, cats are almost equally likely to be infested by I ricinus and Ixodes hexagonus (the hedgehog tick).
When cats are infested by I hexagonus, it is most frequently by nymphs or larvae, which are smaller and more difficult to detect, despite often being in large numbers7,9.
For these reasons, many ticks on cats go unnoticed and untreated. At present, one product is licensed to eliminate I hexagonus – as well as I ricinus – from cats and dogs in the UK.
Tick-borne diseases in dogs and cats are being recognised with increased frequency. This results from a real increased frequency of infection and increased clinical awareness, plus new and more affordable diagnostics.
Cats are thought to be more resistant to clinical disease from tick-borne pathogens; however, several tick-borne diseases have been reported in cats and more are being detected, including tick bite-associated granuloma and/or cellulitis, Lyme borreliosis, anaplasmosis, ehrlichiosis, haemoplasmosis (although this is more commonly from fleas), bartonellosis (cat scratch fever), tularaemia, babesiosis, hepatozoonosis and cytauxzoonosis. These are not all in the UK – at least, not yet10-12.
The authors recently reported on two UK cases of Lyme borreliosis in cats (VT50.21); they both presented with marked bradyarrhythmia (which can also be seen in humans and dogs with Lyme borreliosis). While one cat died of heart failure, the other fully recovered after treatment with doxycycline.
The authors suspect many more cases of tick-borne disease will emerge in cats as their prevalence and awareness increases.
It is more important than ever to use appropriate ectoparasiticides on cats, as well as dogs – many licensed products are available in the UK
