Perhaps you have come across cases of tick infestation or tick-borne disease (TBD) during clinical practice. It is possible you have heard about the growing tick problem in a seminar delivered at a veterinary congress or a continuing professional development (CPD) event. Or maybe you have read about some facts and new trends related to ticks while browsing a website, magazine, or online resource. Whichever category of knowledge-seeker you fit into, you must have discovered that ticks and TBDs are always an evolving and interesting topic — and there is a reason for this.
Current unprecedented levels of climate change — besides melting the arctic ice and raising the sea levels — will certainly influence the prevalence and geographic distribution of pests, including ticks. Hence, the increasing prevalence and distribution of tick populations, at local and global scales, are expected to continue. For example, in summer 2018, a Hyalomma species of giant tick originating in Central Asia has appeared fully grown in Sweden for the first time (The Local, 2018). Another example is the Asian long-horned tick, Haemaphysalis longicornis, which was considered the first exotic tick to enter the US for the first time in 50 years (Beard et al, 2018). These exotic ticks can spread quickly and often carry fearsome diseases.
Exotic ticks have always been considered a major threat to public health, and to the health and welfare of pets and livestock. It has been nearly 3 years since the first four cases of babesiosis were detected in native dogs in Essex (Swainsbury et al, 2016). This incident has caused concern among many veterinary professionals that babesiosis might become endemic in the UK.
What is the role of the veterinary community, whether in clinical practice or in academia, in tackling this challenge? There have been some commendable efforts in the form of publishing timely articles and guidelines, conducting big tick surveys and national surveillance schemes, and increased awareness of the risk of exotic ticks and diseases that come along with these new arrivals.
Ticks: why are they serious?
Ticks can seriously compromise the health of affected animals through various mechanisms. For example, severe anaemia or immunosuppression can result from blood loss caused by the feeding and engorgement of dozens of female ticks. Secondary bacterial invasion of the bite sites can result in skin lesions or pyogenic infections. Exposure to neurotoxins secreted in the saliva of some ticks during a bite can also lead to tick paralysis (toxicity). Furthermore, because ticks are haematophagous (that is, they ingest blood from dogs and cats), they transmit many pathogens, which can cause diseases with far more impact than the direct damage caused by ticks themselves (Elsheikha, 2016).
For example, canine ehrlichiosis caused by Ehrlichia canis, and canine babesiosis caused by Babesia gibsoni can cause considerable illness in affected dogs. These infections may progress to chronic disease, resulting in immunosuppression and pancytopenia (in the case of ehrlichiosis) or haemolysis and shock owing to multiorgan ischaemia (in the case of babesiosis). Ticks are also responsible for the spread of zoonotic diseases to humans, such as Lyme disease, babesiosis, granulocytic ehrlichiosis, tularaemia and rickettsial diseases.
How should TBDs be managed?
Despite the high prevalence of ticks and the growing incidence of TBDs, there is still limited evidence to inform best clinical practice at the time of diagnosis, and during treatment as well as follow-up. Comprehensive diagnosis and clinical management of TBDs is beyond the scope of this article. However, readers can consult other relevant references (Sainz et al, 2015; Dantas-Torres and Otranto, 2016; Solano-Gallego et al, 2016) and guidelines (ESCCAP UK & Ireland, 2019) for information. Here, readers will be presented with seven common questions that may arise during the course of diagnosis and management of ticks and TBDs.
When should you test for TBDs?
In general, the presence of a TBD should be suspected in patients that have clinical signs of anaplasmosis, babesiosis, bartonellosis, borreliosis, ehrlichiosis or hepatozoonosis. Although infection can be asymptomatic and most presenting signs are non-specific, the presence of indicative signs should prompt veterinary practice staff to test for the most likely TBDs. Elaborate laboratory tests should be performed only for patients in whom there is clear suspicion of TBD, associated with tick exposure, based on the information obtained during the initial clinical encounter.
Why should patients and samples be handled wisely?
Veterinary nurses (VNs) are at risk of tick bite while handling tick-infested animals. Ixodes ricinus, for example, can transmit a large number of pathogens such as Borrelia burgdorferi (the causative agent of Lyme borreliosis), tick-borne encephalitis virus, Anaplasma phagocytophilum (agent of human granulocytic ehrlichiosis), Francisella tularensis (agent of Tularaemia), Rickettsia helvetica, Rickettsia monacensis, Babesia divergens, Babesia microti, louping ill virus, and tribec virus.
In any busy veterinary practice, a considerable number of biological samples can be collected from dogs and cats for diagnoses. These samples may contain live tick-borne pathogens, such as Bartonella, which can impose potential zoonotic risks on practice staff. Therefore, VNs should be well informed of the need to use personal protective equipment, practise frequent hand washing, and avoid cuts and needle sticks. VNs should thus avoid not only tick bites, and animal bites or scratches, but also direct contact with blood or bodily fluids from animals (Maggi et al, 2013; Breitschwerdt et al, 2014).
What should be done if ticks are observed on the pet?
Once found, ticks should be removed as rapidly and safely as possible in order to limit the chances of infection being transmitted. To remove ticks, they should be grasped straight, as close to the skin's surface as possible, with tweezers or by using a specially-designed tickremoval tool. After the tick has been removed, the skin should be cleansed with soap and water. Collected ticks should be identified using identification keys (e.g. http://www.bristoluniversitytickid.uk/). Members of the public and veterinary profession can also seek professional advice regarding tick species identification from Public Health England's ‘Tick Recording Scheme’ (https://www.gov.uk/guidance/tick-surveillance-scheme) or the ‘Big Tick’ Project (http://www.bigtickproject.co.uk/).
Accounting for co-infections
Co-infection with multiple pathogens can have serious health and therapeutic consequences due to the possibility of misdiagnosis and ineffective treatment. Dogs are under constant threat of attack by ticks and other vectors (such as fleas, mosquitoes and other biting flies). Clinical cases co-infected with multiple, potentially zoonotic, tick-borne pathogens have been reported (Kordick et al, 1999; Diniz et al, 2007; Breitschwerdt et al, 2014). Proper treatment of patients with co-infection cannot be achieved without correct identification of the patient's main clinical problem. Unless a multiplex diagnostic assay is used to test for more than one infection simultaneously, accurate diagnosis of co-infection can be challenging given the level of unavoidable uncertainty in current diagnostic approaches.
Which drugs should be used?
Acaricide drugs remain the mainstay tool in managing tick infestation and pathogens transmitted by these pests. Many classes of acaricides have been developed with various modes of action, speed of kill and spectrum of activity. While acaricides have increased in number and spectrum of activity, the next stride forward will come in the form of best possible evidence-based protocol.
Therefore, product selection should be based on the clinical need addressed by the product and the evidence of its efficacy. Choice of products should be also based on lifestyle factors, geographic location, previous tick exposure, travel to endemic region/country, affordability, and pet owner preference (tablet, collar or spot-on), as well as other drug needs for concurrent conditions in the pet.
What matters more, speed of kill or repellency?
In recent years, speed of kill has become an important commercial advantage for the marketed products because many vector-borne pathogens can be transmitted within minutes to hours, presenting serious health risks for dogs and cats. With the advent of the isoxazoline drugs with a fast onset of action, transmission of some tick-borne pathogens to dogs and cats can possibly be blocked. Isoxazoline drugs can kill ticks within 24 hours. For example, fluralaner has been shown to have a 4 hour onset of activity, an 8 hour speed of kill and achieved 100% efficacy at 12 hours against adult Rhipicephalus sanguineus (sensu lato) ticks attached to dogs (Burgio et al, 2016). These drugs are indicated for the treatment and control of tick infestation, and the treatment of flea infestation. Some examples are:
- Afoxolaner (NexGard, Merial)
- Fluralaner (Bravecto, MSD Animal Health)
- Lotilaner (Credelio, Elanco)
- Sarolaner (Simparica, Zoetis).
Although transmission time for Borrelia and Babesia is 1–2 days, transmission can occur in less than 16 hours and the minimum attachment time for transmission of infection is still unknown. Also, it is possible that rickettsias and Ehrlichia can be transmitted quickly (within 3–4 hours). In general, transmission is correlated to duration of tick attachment; hence in this scenario, it is sensible to use a product that kills or repels ticks as quickly as possible to reduce the risk of disease transmission. In this regard, the advent of long-lasting acaricides that can repel/kill ticks has been transformational for the management of ticks and associated TBDs. These products contain pyrethroids, which have a tick-repellent (prevent ticks from taking a blood meal), as well as insecticide and acaricide effects. The 10% imidacloprid/4.5% flumethrin collar (Seresto, Bayer Animal Health) is approved for the prevention of tick and flea infestations in dogs and cats by offering up to 8 months of protection in one application. Seresto can also provide significant risk reduction against Bartonella spp. infection in outdoor cats under field conditions (Greco et al, 2019).
Are there any other options for tick control?
Integrated management of tick infestation should be conducted using both chemical (e.g. acaricides as discussed) and non-chemical means. The latter include measures such as avoidance of tick habitat (such as heavily wooded and grassy areas), using repellents, and frequent tick checks (at least one check per day) to pick up and remove ticks before they can transmit any infection.
Understanding what pet owners want should be taken seriously
VNs can play important roles in educating pet owners, identifying their needs and meeting their expectations. Owners should be informed that their pets can easily pick up ticks, by walking in long grass and vegetation where ticks wait to latch onto passing animals. VNs can encourage clients to be ‘tick savvy’, especially during the peak times for tick activity (late spring, early summer and autumn).
Understanding what and how much information pet owners should receive about a product is essential to developing client-oriented treatment information and thus meeting their expectation. Some pet owners may want a combined tick and flea treatment, while others may be concerned about fleas and lungworms. Also, while some owners may prefer topical application, others may choose oral medications. Monthly applications might be considered manageable by some clients, whereas others prefer longer-acting products for more convenience.
Pet owners want to use only safe and effective products for their pets. While many owners are aware of the sensitivity of collie dogs to avermectin compounds, a few pet owners may be unfamiliar and require guidance in using licensed products correctly. Likewise, pet owners should be educated regarding permethrin toxicity in cats in order to avoid accidental application of permethrin-based products. Furthermore, VNs should inform pet owners that isoxazoline drugs act systemically and thus do not prevent the attachment of ticks. Only a repellent product can deter ticks from attaching and feeding.
Conclusions
In recent years, the geographic range of ticks and some TBDs has expanded. Tick bites spread Lyme disease and other infections to animals and humans. Using effective preventative measures is therefore more important than ever.
In this article, the author has outlined seven key points to support VNs' approach to effective management of ticks and TBDs based on the best available data. VNs should engage with pet owners in an informed conversation incorporating assessment of risk of exposure to ticks and potential TBDs, especially prior to travel to endemic regions. These measures will reduce the risk of TBDs and enable the development of preventative strategies targeting the appropriate, at-risk, populations.
Finally, whether VNs learn about ticks and TBDs through clinical experience, reading journals or digital resources, or attending scientific and professional events, whenever possible, they should always seek out new information that is most clinically relevant to ensure high-quality, patient-tailored care.
Key Points
- Management of tick infestation remains an important health issue in both veterinary and human medicine.
- Ticks can cause discomfort, pain, and severe skin signs, and anaemia in heavy infestations.
- Ticks can vector many life-threatening disease agents (viral, bacterial, protozoal and helminthic) to both pets and humans.
- There are a number of effective anti-tick products that can be used to reduce pets' risk of exposure to ticks.
- Using a preventative tool to kill and repel ticks (e.g. Seresto collars) can help to reduce the risk of transmission of TBDs, such as Bartonella spp. infection in cats.
- Tick treatment of pets entering the UK, although not obligatory, is still recommended to protect travelling and local pets.