Flea and tick preventive treatments in cats and dogs remain vitally important for pet health, biosecurity and management of zoonotic risk.
This is true for both the old enemies in the form of cat fleas and endemic ticks (Ixodes species and Dermacentor reticulatus), plus more exotic ticks and their pathogens from abroad.
A milder climate has allowed cat fleas to thrive and ticks to feed all year round. Increased pet travel and imports in the face of increased tick and tick-borne disease distributions across Europe have also led to an increased risk of exotic ticks and their pathogens being introduced to the UK.
Routine preventive flea treatment in all pets – and tick preventive treatments for those at risk of exposure – have, therefore, never been more important.
The flea and tick prevention market is changing as rapidly as the distribution of the parasites themselves, however, so careful consideration of core flea and tick control principles – as well as the lifestyle of pet and owner – must be taken in selecting suitable products to maximise compliance and meet the needs of individual pets. In doing so, human and pet health can be optimised, while increasing profits in a responsible way.
Oldest enemy
The cat flea (Ctenocephalides felis) causes human irritation and revulsion, creates flea allergic dermatitis in susceptible pets and acts as a vector for a variety of infections.
Bartonellosis is of particular concern as a common zoonosis spread through flea faeces, as well as cat scratches. Successive mild winters and wet summers have favoured proliferation of cat fleas in the UK.
Central heating also allows environmental stages of the flea life cycle to persist all year round in the home. This combination of factors has led to increased flea challenge, and any break in flea treatment on any pets in a household will allow flea infestation to establish or continue. All UK cats and dogs should, therefore, be treated for fleas frequently enough to prevent egg production and household infestation establishing.
Ticks in the UK
Seasonal peaks of tick activity occur in the UK during the spring and summer (Smith et al, 2011), but growing evidence suggests questing and feeding occur throughout the year.
Exactly 2.37% of ticks on UK dogs, and 1.8% on cats, have been found to be carrying Borrelia species (Abdullah et al, 2016; Davies et al, 2017), demonstrating both cats and dogs are being exposed to the causative agent of Lyme disease.
In addition to the risk of Lyme disease, an endemic focus of Babesia canis has established in Dermacentor ticks in Essex (Phipps et al, 2016). This parasite can be highly pathogenic in dogs if not treated rapidly and the parasite has already spread from its original focus in Harlow, Essex, with new cases now being reported in Romford, east London; and Ware, Hertfordshire. Cats and dogs may also be exposed to other potential pathogens, such as Babesia microti, Babesia vulpes and Anaplasma phagocytophilum, through infected Ixodes species ticks.
Emerging threats
Rhipicephalus sanguineus, which is capable of carrying a wide range of tick-borne diseases pathogenic to humans and pets, are being seen regularly on imported dogs, and those having travelled to southern and eastern Europe.
The Big Tick Project, which examines dogs across the UK for ticks, found that of all the dogs that had travelled in the two weeks prior to their inclusion in the study, 30.2% were infested with R sanguineus (Abdullah et al, 2016).
The European Scientific Counsel Companion Animal Parasites (ESCCAP) UK and Ireland has also seen an increased number of Ehrlichia canis cases transmitted by R sanguineus reported in travelled dogs in 2017.
Although it is unlikely R sanguineus would currently establish outdoor endemic populations in the UK, it can complete its life cycle in three months, which has allowed it to infest UK homes in a similar way to fleas (Hansford et al, 2015). This is a concern, as these ticks may carry zoonotic pathogens such as Rickettsia conorii. Records of R sanguineus received by the Tick Surveillance Scheme are increasing each year and, in the past two years, two house infestations have been confirmed (Hansford et al, 2017).
A Hyalomma lusitanicum tick was also found on a dog that had returned to the UK from Portugal. This species of tick is a potential vector of Crimean Congo haemorrhagic fever virus (CCHFV), which is highly pathogenic to humans (Hansford et al, 2016).
In addition to these risks, Dermacentor ticks carrying B canis may be encountered almost anywhere in Europe, as may Ixodes species ticks carrying tick-borne encephalitis – another life-threatening zoonosis. Its presence in imported pets or Ixodes ricinus ticks presents a risk of it establishing in the UK in the endemic Ixodes species population.
This combination of threats makes tick prevention vital before, during and after pets have travelled abroad, and close surveillance essential for ticks in pets entering the country.
Prevention advice
For flea elimination programmes to be successful, adult fleas must be killed on the pet before they can produce eggs. While use of growth regulators and environmental insecticides are useful at reducing larvae and eggs, they will have minimum effect on pupae in the environment – so effective, rapid killing of adults is required to completely break the reproductive cycle. Top tips for this include:
- The use of an effective adulticide to prevent egg laying. This requires fleas to be killed within at least 24 hours and for an effective product to be applied frequently enough that this time isn’t exceeded and eggs are produced.
- Effective environmental control to reduce environmental life stages. Without treatment of the environment, some flea infestations will take many months to eliminate (Dryden et al, 2000).
- Management of client expectation. Heavy infestations of fleas may still take at least three months to eliminate, even when environmental treatment and an effective treatment is used (Dryden et al, 2000).
Year-round prevention for all cats and dogs is essential to prevent infestations establishing and disease transmission taking place. Even pets with no outdoor access may be exposed to fleas through introduction from visiting pets, stray cats or wildlife. People may also trigger outdoor flea pupae to emerge and then mechanically transfer the newly emerged adult fleas inside the home.
No preventive treatments for ticks are 100% effective, but the use of a drug that rapidly kills ticks, such as an isoxazoline (examples include Bravecto, Credelio, Nexgard or Simparica) or pyrethroid repellents will greatly reduce disease transmission.
Preventive treatment for ticks is, therefore, important in dogs walking in tall grass, rough pasture or areas where deer and ruminants have access, and in cats with prolonged and regular outdoor access. It is also important for cats and dogs with a history of tick attachment.
All dogs living in and visiting Essex, and adjoining counties, with outdoor access should be considered at an increased risk due to the presence of B canis in the region.
Because no tick preventive product is 100% effective, it is also important to check pets and remove any ticks found with a tick hook or fine-pointed tweezers. If tweezers are used, the tick should be removed with a smooth upward pulling action. If a tick hook is used, a simple “twist and pull” action is employed.
Compressing or crushing ticks in situ with blunt tweezers or fingers will stress the tick, leading to regurgitation and emptying of the salivary glands, potentially leading to increased disease transmission. Traditional techniques to loosen the tick, such as the application of petroleum jellies and burning, will also increase this likelihood and are contraindicated.
Know your enemy
Identification and recording of ticks found on dogs and humans is important so their distribution can be mapped and the potential introduction of exotic ticks to the UK can be monitored. Records are also helpful in establishing the risk of household infestations and identifying the pathogens that may have been passed on to dog or owner.
Ticks can be sent to Public Health England for identification (www.gov.uk/guidance/tick-surveillance-scheme) or identified using the Bristol tick ID website (www.bristoluniversitytickid.uk)
Client questions
The following are questions that should be asked of owners:
Does the pet already receive regular preventive treatment? If so, which product is used and at what frequency? If an effective flea product is already being used at the correct frequency, it may not be necessary to change it. However, if treatment is not adequate it opens up the opportunity to explore why and what might improve compliance.
A client may tell a member of the practice team he or she is flea-treating a pet effectively and believe this is the case, so it is important to obtain information on treatment product and frequency to ascertain if this is the reality. Similarly, tick treatments should also kill rapidly or repel and kill, and be applied at the correct frequency.
Has the pet had a previous reaction to treatment? Even if the treatment reaction is suspected rather than confirmed, the product should be avoided as fears surrounding possible reactions will reduce compliance.
Does the licence have a preference for tablets, collars or spot-on solutions? It is important clients feel happy and confident with the type of product they are prescribed. Demonstrating how to use and apply products is also useful in increasing compliance.
Where a client is unable to administer a flea or tick treatment in any formulation, applying it at the surgery is a useful option to maximise compliance and bond clients to the practice – especially where the pet is not particularly stressed visiting the clinic.
Does the pet frequently swim or is shampoo applied? The efficacy of some flea and tick treatment products containing fipronil, imidacloprid or pyrethroids can be affected by swimming and shampoo.
Does the pet suffer from flea allergic dermatitis? In these cases, a product that rapidly kills fleas and/or minimises bites is required to limit exposure to flea saliva.
Travelling pets
Pets travelling in Europe should be treated with a tick preventive product to minimise exposure to tick-borne diseases and reduce the risks of tick vectors being introduced to the UK.
Because E canis may be transmitted within a few hours and because southern Europe is endemic for Leishmania infantum, pets visiting central, southern and eastern Europe should be treated with a repellent pyrethroid. Licensed tick repellent spot-on preparations and collars are available for dogs (for example, Activyl Tick Plus, Advantix, Frontect, Scalibor, Seresto and Vectra 3D) and a licensed collar for cats (Seresto). Treatment should be started a week before travel and continued at least a week after return to the UK.
Four pillars
ESCCAP UK and Ireland recommends four key steps when dealing with all imported or travelled pets arriving in the UK:
1. Check for ticks and subsequent identification of any found.
This is important, even if tick treatment has been administered, in case any ticks have survived. Identification of ticks allows the introduction and distribution of exotic tick species to be monitored in the UK, but also indicates the tick-borne diseases the imported pet may have potentially been exposed to.
2. Treat dogs again with praziquantel within 30 days of return to the UK and treat for ticks if treatment is not already in place.
This will ensure Echinococcus multilocularis is eliminated from imported pets, regardless of the timing of their compulsory treatment, or if doubt exists about it having been administered correctly/at all.
Tick treatment will increase the likelihood of attached ticks being killed if they are missed on examination. Ticks are easily missed in large or long-coated breeds, and in cats and dogs that are reluctant to be examined.
3. Recognise clinical signs relevant to diseases in the countries visited or country of origin.
While it is not possible to be familiar with every exotic parasite, a thorough and comprehensive clinical exam of imported pets will identify adverse clinical signs and these can then be compared to parasitic diseases in the countries the pet has visited.
4. Screening for Leishmania species and exotic tick-borne diseases in imported dogs.
Both Leishmania infantum and tick-borne diseases can have long incubation periods and carrier states. Infection can also be lifelong and, in some cases, carry a poor prognosis. Screening for these parasites will lead to early diagnosis, preparing the owner for what could be a lifetime of potential treatment, while indicating any associated zoonotic risk and limiting wider spread through effective tick control.
The four pillars concept allows veterinary professionals to prepare owners if parasites are present, improve prognosis of clinical cases, minimise the risk of spread of any disease, and carry out effective disease and parasite surveillance.
Conclusions
Flea and tick control has never been more important in cats and dogs as flea numbers in the UK increase and pets are exposed to ticks for longer periods at home and abroad.
Preventive products form a vital part of this control and time should be taken with clients to assess personal preferences and compliance issues, and ensure an effective regime using a suitable product for the individual is established. In doing so, efficacy, compliance and sales can all be maximised for the good of client, pet, veterinary practice and national biosecurity.
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