Vet Times The website for the veterinary profession https://www.vettimes.co.uk Tick threat and control methods Author : Hany Elsheikha Categories : Farm animal, Vets Date : May 29, 2017 ABSTRACT Ticks are a complex group of ectoparasites considered the most important vector of pathogens in the northern hemisphere. Control of ticks in companion animals (dogs and cats) is essential – not only to maintain the health and welfare of the animal, but also to protect people from tick infestation and the potential transmission of serious zoonotic infections. A large number of effective acaricides are already available; however, optimal management of ticks is a task that has always been difficult to accomplish. This is due to many variables, including the large number and ecological complexity of tick-borne pathogens, the geographic expansion of the tick vectors, the broad range of reservoir hosts, and limitations associated with diagnosis and treatment of tick-borne pathogens. Integrated interventions tailored to each animal and engaging pet owner to enhance drug compliance are the way forward if we are to achieve effective tick control. Also, knowledge of the indications and safety of available acaricide drugs is crucial when choosing the appropriate treatment for the individual animal. In this article, the clinical impact of tick infestation is discussed and information regarding the control of ticks is provided. Ticks are arthropods belonging to the class Arachnida. To date, more than 900 tick species exist worldwide and they are classified as hard ticks (Ixodidae) or soft ticks (Argasidae). Ticks can cause physical damage to their victims and, in some instances, death. Indeed, companion animals have always suffered from a broad range of tick infestations. Irritation, allergic reactions and fatal illnesses can occur in infested animals. Ticks are efficient blood suckers and among the most dangerous haematophagous ectoparasites. All stages of ticks feed on blood of their hosts. Therefore, they can transmit many tick-borne pathogens to animals and humans. Ticks vector a broad range of disease-causing pathogens and 1 / 7 are second only to mosquitoes in their capacity to transmit disease agents of importance to human and animal health. Figure 1. Adult females of the common tick species of dogs and cats in the UK. (A) Ixodes ricinus (the sheep tick, wood tick, deer tick or castor bean tick), (B) Ixodes hexagonus (the hedgehog tick), (C) Ixodes canisuga (the British dog tick), (D) Dermacentor reticulatus (the ornate cow tick or the marsh tick), (E) Haemaphysalis punctate (the red sheep tick) and (F) Rhipicephalus sanguineus (the brown dog tick or kennel tick). Figures A to D show the dorsal view of the tick and Figures E and F show the ventral aspect of the tick. Scale bar = 1mm. IMAGE: University of Bristol tick ID online (http://bristoltickid.blogs.ilrt.org) with permission of Richard Wall. Therefore, better understanding of the tick epidemiology and available approach to control tick infestation is more important than ever. Health impacts of tick infestation Tick infestation can seriously compromise the health of the affected animal through multiple ways. Firstly, severe anaemia or immunosuppression can result from blood-feeding and engorgement of many adult female ticks (Figure 1). Secondly, bacterial infection of bite sites can lead to dermal pathologies or pyogenic lesions. Thirdly, toxins secreted in the saliva of certain ticks can cause tick paralysis. More importantly, ticks can transmit many pathogens, which can cause diseases more serious than the damage caused by ticks themselves (Elsheikha, 2016). For example, canine ehrlichiosis due to Ehrlichia canis and canine babesiosis due to Babesia gibsoni and Babesia canis can significantly cause ill health of dogs. 2 / 7 Infections may progress to a chronic disease, resulting in immunosuppression and pancytopenia in cases of ehrlichiosis or haemolysis, and shock due to multi-organ ischaemia during babesiosis. Fortunately, babesiosis is rare in British dogs – most cases are acquired abroad. However, the detection of a cluster of dogs with babesiosis in Harlow in the year 2016, and bearing in mind some of the affected dogs have not travelled abroad, has raised concerns babesiosis might become endemic in the UK. In nature, risk of exposure to ticks is high. Dogs can be infested with hundreds of ticks and infestation may involve different tick species. Dogs with heavy tick exposure can be infected at a high rate with multiple tick-borne pathogens. Indeed, clear evidence exists for simultaneous acquisition and transmission of various pathogenic species and strains in dogs following tick bites (Diniz et al, 2007; Breitschwerdt et al, 2014). Ticks are also responsible for the spread of zoonotic diseases to humans. During the past two decades, a dramatic increase has occurred in human infection with tick-borne pathogens such as Borrelia, Anaplasma, Ehrlichia and Rickettsia. Tick control methods Given the complexity and diversity of ticks and their life cycles, it is sensible to expect tick control to require an integrated approach combining off-host and on-host treatment. Chemotherapeutic treatment and prevention A number of anti-tick (acaricide) products can be used to reduce the risk of exposure of pets to ticks. However, the selection of acaricide-resistant ticks and environmental impacts due to chemical residues are the only two limitations of using chemical acaricides (Eiden et al, 2015). This was the reason for the increased interest in exploring plant extracts as eco-friendly acaricides or repellents against ticks (Benelli et al, 2016). Regardless, acaricides remain the mainstay to achieve effective tick control. Choice of acaricide product should be based on animal lifestyle factors, geographical location, previous tick exposure, travel to an endemic region/country, owner affordability, and preference and any other drug needs for the pet. Some products contain pyrethroids, which have a tick- repellent (prevent tick from taking a blood meal), as well as insecticide and acaricide effects. Besides ticks and tick-borne diseases, many other diseases are transmitted by other arthropod vectors. Those should be also take into account when devising chemical control strategy for pets. It is important to know cats can develop toxicity if a canine permethrin product is applied inappropriately or via secondary contact with a dog treated with a spot-on product containing permethrin. So, it is best to avoid the use of permethrin-containing products on a dog that shares a home with a cat. Cat collars that contain small amounts of permethrin may be appropriate for use 3 / 7 on cats. For more information on ectoparasiticides, Veterinary Prescriber created the parasiticides database to guide practitioners on the available products (www.veterinaryprescriber.org/subscribers-content/2014/7/10/ecto). A tutorial also exists on how to use the parasiticides guide (www.veterinaryprescriber.org/free-articles/2015/4/16/how-to-use-the-ectoparasiticide-guide). Protective measures and tick removal Tick control can be effective without the adoption of some protective measures. These include avoidance of tick habitat, avoiding heavily wooded and grassy areas, using repellents, and frequent tick checks (at least one check per day) to pick up and remove ticks, with a tick removal device or fine pointed tweezers, before they can transmit disease. Although the transmission time for Borrelia (agent of Lyme disease) and Babesia is one to two days, transmission can occur in less than 16 hours and the minimum attachment time for transmission of infection is still unclear. It is also possible Rickettsia and Ehrlichia can be transmitted quickly (within three to four hours). In general, transmission is correlated to duration of tick attachment, hence it is advisable to use products that kill or repel ticks as quickly as possible to reduce the risk of disease transmission. Ticks can be collected directly from the animals by hand-picking. This method involves manual search for ticks on the body and fur of animals. Pet owners should be advised to check pets for ticks after walks. If a tick is found on the body, it should be removed completely. The body of the tick should be grasped gently and vertical traction applied, using blunt, medium-tipped, angled forceps, until it displaces. Commercially available devices (known as tick twisters) especially designed for tick removal using “twist and pull” action can also be used. Some tick removal methods should be avoided, such as applying a hot match to the tick body, covering the tick with petroleum jelly, nail polish, alcohol, or gasoline, using lidocaine and passing a needle through the tick. If any of these improper techniques is applied, parts of the mouth may remain in the skin, which can lead to infection or elicit inflammation. Vaccination has been shown to be a feasible tick control method in cattle and offers a cost- effective, environmentally friendly alternative to chemical control (Jonsson et al, 2000). However, identification of tick-protective antigens remains the limiting step in vaccine development. Tick antigens exposed naturally to the host during tick feeding and those concealed have both shown promise as candidate vaccine antigens. Development of effective vaccines against multiple tick species infesting dogs and cats may be possible using highly conserved tick-protective antigens that exhibit immune cross-reaction to different tick species or using a combination