Reducing the threat of tick-borne diseased for dogs in the UK

TICKS HAVE NEVER SEEN SO MUCH ATTENTION in the veterinary and consumer media, but what is behind the media noise and how should vets be reacting? There is a drive, rightly so, to increase awareness of tick-borne diseases (TBD) due to their importance in global “one health”. But specifically in the UK, increasing reported cases of tick-borne disease have driven the media agenda. Within the profession, reports of expansion of the distribution of ticks already endogenous to the UK have also been frequent. As a result, more than ever before veterinary professionals are expected to remind pet owners of the importance of parasite prevention, particularly tick prophylaxis, to reduce the threat of TBD. The content below collates the most relevant studies and information to help vets understand the true scale of risk and effectively discuss preventive treatment options with their clients.

Tick prevalence on the increase

The profession is seeing an expansion of the distribution of ticks already endogenous to the UK, with a predominant emphasis on the west and south coasts of England. This geographical expansion of tick species and subsequent TBD is likely to be multifactorial and factors causing this may include:

• Increasing transportation of pets (for sport, leisure activities or simply taking pets on holiday).
• Climate change, which may increase the density of vectors in an area or cause them to drift northwards.
• Increasing urban sprawl with increased proportions of wildlife
• reservoirs having a closer association with human and pet activity (for example the expansions of urban fox populations) and changes in farming practices (banning of certain sheep dips, for example).
• Increasing populations of natural hosts (for example wild deer).
• The move in 2012 to encourage harmonisation within the EU regarding pet travel rules. This removed the need for compulsory tick treatment for travelling pets returning to the UK.

Tick-borne disease: emergence of new threats

Some species of tick such as Ixodes ricinus appear to be increasing1, but also a number of other tick species are appearing in the UK. For example, the tick Dermacentor reticulatus – an important vector of canine babesiosis in Europe and Rhipicephalus sanguineus; the vector for Hepatozoon spp; Erhlichia spp. and some
species of Babesia. Specifically, Public Health England has reported two cases of infestations with this brown dog tick, Rhipicephalus sanguineus, in residential properties in the UK (Leicestershire and Essex). In these cases the ticks were originally thought to have been introduced into households by dogs imported from Mediterranean Europe. However, infestation was able to become established and ticks were able to survive over winter in both cases.2 Of recent interest, three cases of canine babesiosis in dogs with no travel history have been reported in Essex, England.3
The tick host (Dermacentor) was found in the surrounding area (possibly also recovered from two of the affected dogs). Prior to this outbreak, Dermacentor ticks were also found in West Wales and Devon4 and a fatal case of Babesiosis was reported in an untravelled dog from Kent.4 The reasons for the geographical spread of tick species and subsequent TBD are likely to be multifactorial and factors that may cause this are listed above.

Importance of tick bite prevention

Given the recent reports of emerging threats and the existing endemic TBD
risk, it is more important than ever to recommend adequate tick prophylaxis.
Previously it was thought that ticks needed to attach for more than 48 hours to transmit diseases; however, reports now suggest that this might not be the case.5,6 Ticks carrying Ehrlichia canis have been shown to infect dogs in as little as three hours after attachment.7 The author would recommend that,
where feasible, ticks are removed (ideally using a specific removal device) as soon as they are observed (and if possible within 24 hours). However, it is ideal to recommend precautions to avoid the tick from biting the animal in the first instance. During feeding, ticks (and/or other ectoparasites such as fleas) inject a small amount of saliva into the skin and pets may become sensitised or allergic to this, resulting in stress and possibly other dermatological conditions. Using a product which repels ticks can also help towards halting the transmission and spread of harmful diseases such as Lyme disease and Babesiosis. The extended tick season Historically, vets and the public have been educated about a specific tick season. Typically tick numbers are expected to be increased in the UK between March and November when favourable climatic and environmental factors support tick survival and biting activity. Although most infestations are highest in spring, early summer then again in autumn, tick infestation is in fact possible all year round during milder weather (>3.5°C). Preventive treatments which offer up to eight months’ efficacy against flea and tick bites are now available, providing the longest level of protection for dogs and cats.

Year-round flea prophylaxis?

Although not attracting the same media attention as tick-borne diseases, fleas are also capable of transmitting disease to animals and humans. When promoting effective flea control, it is of vital importance to consider the pet (or all of the pets in a multi-animal household) and the
environment. Given that the optimal temperatures for completion of the flea lifecycle are around 18 to 25°C, our modern centrally-heated homes support this perfectly throughout the year. This means that flea infestation is now a year-round problem and the efficacy duration of preventive treatment should be considered to prevent household infestation.

References

1. Dobson, A. D. M., Randolph, S. (2011) Modelling the effects of recent changes in climate, host density and acaricide treatments on population dynamics of Ixodes ricinus in the UK. J Appl Ecol 48: 1,029-1,037.
2. Hansford, K. M., Pietzsch, M. E., Cull, B., Medlock, J. M. and Wall, R. (2015) Overwintering of the brown dog tick in residential properties in England: raising awareness. Vet Rec 177: 156.
3. Swainsbury, C., Bengtson, G. and Hill, P. (2016) Babesiosis in dogs. Vet Rec 178: 172.
4. Holm, L. P., Kerr, M. G., Trees, A. J., McGarry, J. W., Munro, E. R. and Shaw, S. E. (2006) Fatal babesiosis in an untraveled British dog. Vet Rec 159: 179-180.
5. Kidd, L. and Breitschwerdt, E. B. (2003) Transmission times and prevention of tick-borne diseases in dogs. Compendium 25 (10): 742-751.
6. Nicholson, W. L., Allen, K. E., McQuiston, J. H., Breitschwerdt, E. B. and Little, S. E. (2010) The increasing recognition of rickettsial pathogens in dogs and people. Trends in Parasitology 26 (4): 205-212.
7. Fourie et al. (2013) Transmission of Ehrlichia canis by Rhipicephalus sanguineus ticks feeding on dogs and on artificial membranes. Veterinary Parasitology 197: 595-603.