Which tick product?

Since the recently reported cases of Babesia canis in dogs in Essex there has been a great interest in the efficacy of tick products. B. canis, a protozoal parasite is transmitted to dogs by infected ticks. Parasite specialists from ESCCAP UK & Ireland say that it takes at least 24 hours for the parasite to be transmitted after a tick bite, so owners should check their dogs daily for ticks and remove any found. They strongly advise the use of a tick preventive product for dogs in the area where Babesia has been reported, to reduce the risk of disease  transmission, and they recommend using a product that either repels or rapidly kills ticks. In this article we explain what is meant by repellent and rapid killing effect and list the products that meet these criteria.

Since the recently reported cases of Babesia canis in dogs in Essex there has been a great interest in the efficacy of tick products. B. canis, a protozoal parasite is transmitted to dogs by infected ticks. Parasite specialists from ESCCAP UK & Ireland say that it takes at least 24 hours for the parasite to be transmitted after a tick bite, so owners should check their dogs daily for ticks and remove any found. They strongly advise the use of a tick preventive product for dogs in the area where Babesia has been reported, to reduce the risk of disease  transmission, and they recommend using a product that either repels or rapidly kills ticks. In this article we explain what is meant by repellent and rapid killing effect and list the products that meet these criteria.

Which tick product?

Ticks have been in the news a lot over the past few months. First there was the very well-publicised report from the Big Tick Project, a survey involving 12,096 dogs in 1,094 practices across the UK, by researchers from the University of Bristol and the pharmaceutical company MSD. It aimed to assess tick abundance in dogs presenting to UK practices. (Abdullah et al 2016) Here are some key findings:

  • Dogs in the UK are most likely to be bitten by Ixodes ricinus: this was the species on 89% of the dogs that had ticks. The next most common tick was Ixodes hexagonus, found on 10% of dogs with ticks. Both ticks are widely distributed throughout the UK.

  • Dogs in urban areas were as likely as those in rural areas to be infected with ticks.

  • The overall prevalence of ticks was 30%. It was highest in the south west of England, East Anglia and Scotland. The study authors explain that this figure is higher than in other studies and may be an overestimate because of the way practices were recruited to the survey: those who enrolled might have had a greater interest in ticks and tick-borne disease or were from practices with a known history of tick problems. Nevertheless the study provides a baseline for measuring changes in prevalence in future surveys.

  • A few dogs that had travelled to the Mediterranean region were infected with Rhiphicephalus sanguineus. This shows the importance of appropriate protection against ticks for dogs travelling abroad, and the persistent threat of introduction and establishment of non-endemic ticks and their pathogens into the UK.

  • 10 dogs were infected with Dermacentor reticulatus (a vector for Babesia canis); these were mainly in south-west England and west Wales.

Another important piece of research came from SAVSNET and the University of Liverpool, focusing on the risk of Babesia canis infection in the UK. (Sánchez-Vizcaíno et al 2016) The researchers confirmed the likelihood of a local infected Dermacentor tick population in the Chelmsford area of the UK, where there had been a cluster of Babesia canis cases in dogs that had not travelled abroad. In the rest of the UK they found a low level of sporadic cases of Babesia which they considered most likely to be associated with dogs arriving, or returning, from abroad.

Finally, a consensus statement from ESCCAPUK&Ireland gives practical information on controlling ticks and tick-borne diseases with the aim of promoting consistent advice throughout the veterinary profession. The document stresses that the degree of risk depends on the pet’s lifestyle, the history of previous tick exposure and geographical location. It advises that veterinary professionals should make a risk assessment of tick exposure for dogs as part of an overall parasite control programme and recommends routine tick treatment for pets travelling abroad. See the full document, ESCCAP UK & Ireland tick and tick borne disease advice consensus statement, here: www.esccapuk.org.uk in the News section.

Which tick product?

If a risk assessment indicates a need for a tick product, there is a very wide range to choose from. To be effective a product needs to be used correctly and consistently, which means choosing a formulation (collar, spot-on, spray, or tablet) that suits the pet and owner. No product is 100% effective and regular checking for, and removal of, ticks is crucial.

Tick products either contain a drug that kills ticks (an acaricide), or one that kills and repels ticks (i.e. a pyrethroid: deltamethrin, flumethrin or permethrin). Tick-borne disease transmission becomes more likely the longer the tick is attached, so any product which kills or repels ticks will reduce the risk of disease transmission and the more rapidly this occurs, the greater the protective effect.

Evidence of rapid-killing effect

Up until now, the medicines licensing regulations have required tick products with a killing effect to be shown to reduce tick count by 90% within 48 hours of product application. More recently some companies have done studies to show their products have a killing effect within 24 hours. Two of the newest acaricide products (Bravecto, a chewable tablet containing fluralaner, and Simparica, a chewable tablet containing sarolaner) provided evidence to the regulatory authority that they begin to kill Ixodes ricinus ticks within 12 hours of attachment (and a statement reflecting this is in the products’ SPCs). The company that markets Nexgard (a chewable tablet containing afoxolaner) published a clinical trial showing that killing effect begins within 12 hours of I. ricinus attachment (Halos et al. 2014). Other products that have been shown to have an onset of effect within 24 hours are: fipronil + amitraz + (S)-methoprene (Certifect spot-on) (I. ricinusR. sangineus and D. reticulatus) (Baggott et al. 2011); and permethrin + fipronil (Frontect spot-on) (I. ricinus and R. sangiuineus) (Beugnet et al. 2016).

Products for dogs with fast-acting tick killing or repellent effect

 If a dog lives in, or is travelling to, an area where there is a high risk of contracting a tick-borne disease it makes sense to use a product that has been shown to have a fast-killing or repellent effect. There’s a wide range available, so it should be possible to find a formulation and parasite coverage that suits a particular animal.

Products containing a tick repellent or fast-acting acaricide

The table was compiled using the Veterinary Prescriber Parasiticide Guide. For more on parasite control, go to our series of modules on “Parasiticides for cats and dogs: a rational approach”. The six modules include: an introduction to risk assessment and parasiticide products; puppy worming; adult dogs; kitten worming; adult cats; and creating a practice parasiticide policy. They are evidence-based, highly practical and independent of the pharmaceutical industry.

No guarantees

A product won’t work if it’s not used correctly, so choice of formulation is important. No product is 100% effective, and the possibility of ticks biting and transmitting a disease cannot be ruled out. So dogs should still be checked for ticks on a daily basis.

References

Baggott D et al. Efficacy of a novel combination of fipronil, amitraz and (S)-methoprene for the treatment and control of tick species infesting dogs in Europe. Vet Parasitol 2011; 179: 330-4.

Beugnet F et al. Assessment of the prophylactic speed of kill of Frontline Tri-Act against ticks (Ixodes ricinus and Rhipicephalus sanguineus) on dogs. Parasite 2016; 23: 2.

Committee for medicinal products for veterinary use. Guideline for the testing and evaluation of the efficacy of antiparasitic substances for the treatment and prevention of tick and flea infestation in dogs and cats, November 2007.

Committee for medicinal products for veterinary use. CVMP assessment report for Bravecto (EMEA/V/C/002526/0000), December 2013.

European Medicines Agency. Guideline for the testing and evaluation of the efficacy of antiparasitic substances for the treatment and prevention of tick and flea infestation in dogs and cats. Draft. 2015.

Halos L et al. Immediate efficacy and persistent speed of kill of a novel oral formulation of afoxolaner (NexGard) against induced infestations with Ixodes ricinus ticks. Parasit Vectors. 2014; 7: 452.