Cats and dogs are exposed to a wide range of parasites such as Toxo-cara spp.., Echinococcus granulosus, Angiostrongylus vasorum and tick-borne diseases, which may cause significant disease in pets or present zoonotic risks to owners (Morgan et al, 2005; Overgaauw and van Knapen, 2013; Craig, 2014). Although there are few data on current UK disease incidence from these parasites, the consequences of infection are potentially severe. This article discusses some of these clinical syndromes and risk factors, as well as the role of veterinary nurses in assessing this risk, and developing subsequent parasite-control plans.
Determining parasitic risk and treatment strategies
Strategies to limit parasitic disease rely on a combination of practical control measures and preventative drug treatments; these form the basis of parasite-control protocols for individual pets. Parasite-control programmes are becoming increasingly popular and important as treatment options and potential parasite threats increase. Parasite-control programmes allow for bespoke advice based on regional risk and lifestyle of the pet. Asking questions surrounding lifestyle, previous treatment adverse effects, and owner preferences will also help to maximise compliance, and therefore the effectiveness of any recommended treatment. The collection of information required to formulate a parasite-control plan is a team effort and the veterinary nurse plays a vital role.
Some parasites with disease and zoonotic potential are ubiquitous and exposure is practically impossible to avoid. For UK cats and dogs, this is true of the roundworm Toxocara and cat fleas. Regular treatment for Toxocara and fleas is essential and should therefore form the basis of all cat and dog parasite-control programmes. Other parasite prevention is risk-assessed on the basis of lifestyle and geographical distribution. Parasites to consider in the UK would be ticks (Ixodes spp., Dermacentor reticulatus), tapeworm (Dipylidium caninum, Taenia spp., Echinococcus granulosus) and lungworm (Angiostrongylus vasorum).
Fleas
Cat fleas are thriving in the UK with successive mild winters and wet, warm summers. Central heating allows environmental stages of the flea life cycle to persist all year round in the home. This combination of factors leads to increased flea challenge and, without routine preventative treatment, will allow flea infestations to establish (Coles and Dryden, 2014). Although cat fleas cannot live and reproduce on people, they can bite leading to human irritation. They are also a source of revulsion, eroding the human–animal bond. They are a cause of fleaallergic dermatitis, anaemia in heavy infestations, and vectors for a variety of infections including Bartonella spp. (cause of cat scratch disease), Rickettsia felis (cause of spotted fever) and Haemoplasma spp. (cause of feline infectious anaemia).
To prevent flea egg-laying and break the reproductive cycle, an effective adulticide treatment is required. Adulticides should kill 100% of fleas to prevent egg-laying. Adult fleas can lay eggs within 24 hours so effective adulticides must kill fleas within that time. They must also be administered frequently enough to continue to prevent flea egg-laying. The time after application of the adulticide at which fleas survive long enough to lay eggs is known as the reproductive break point. If the reproductive break point is reached, flea control will fail. Treatment of the environment with insecticides and growth regulators is also important to eliminate existing infestations. Daily vacuuming of areas frequented by flea-infested pets and washing of bedding has also been demonstrated to reduce pupae numbers in the environment. Vacuumed debris should be disposed of after each cleaning session.
Roundworm
All puppies and kittens are infected with Toxocara canis (T. canis) and T. cati respectively, at, or shortly after birth (Overgaauw and van Knapen, 2013). This occurs through transplacental (in the case of puppies) and transmammary (in the case of puppies and kittens) infection. This results in approximately 5–10% of adult domestic dogs and 10–20% of adult domestic cats shedding Toxocara eggs at any one time if left untreated (Turner and Pegg, 1977; Wright and Wolfe, 2007; Overgaauw and van Knapen, 2013; Wright et al, 2016). These eggs are not immediately infected but contaminate the environment where they can develop to embryonated eggs. Once embryonated, they represent a zoonotic risk that, if ingested by humans, can lead to visceral pain, lethargy, blindness and increased risks of chronic conditions such as asthma, epilepsy and dermatitis (Buijs et al, 1997; Pinelli et al, 2008; Quattrocchi et al, 2012).
It has been demonstrated that the use of a licensed anthelmintic every 3 months significantly reduces Toxocara spp. ova shedding (Wright and Wolfe, 2007), and there is no evidence that treating any less frequently than this will have any effect on egg output. Therefore, administration of a suitable product every 3 months should be a minimum recommendation. Monthly treatment, however, will reduce egg shedding by 90% or more. Monthly treatment should therefore be considered for cats and dogs on raw, unprocessed diets; those that hunt; or those in regular contact with young children or immunocompromised individuals. A wide range of mammals and birds have been demonstrated to act as paratenic hosts, so the feeding of any raw diet of animal origin or predatory behaviour should be considered a risk.
Ticks
The risk of exposure to ticks in the UK has increased with a milder climate allowing feeding throughout much of the year (Smith et al, 2011). On UK dogs, 2.37% of ticks have been found to be carrying Borrelia spp. (Abdullah et al, 2016), and the reported annual incidence in the human UK population of Lyme disease is increasing. In addition, an endemic focus of Babesia canis has established in Essex, which can be fatal to dogs if not treated rapidly. Dogs walking in land shared by ruminants and deer, and in tall grass, bracken and undergrowth, will be at increased risk of exposure. Areas of high tick densities are recognised, however, and have been highlighted in recent UK distribution maps (Abdullah et al, 2016). Dogs living in or visiting Essex should currently be assumed to be at an increased risk of exposure to babesiosis due to the recent outbreak (Phipps et al, 2016). Cats and dogs with a history of tick exposure are likely to be re-exposed. Owners who have reported ticks on clothing or attached to themselves are also likely to have pets with a greater risk of exposure due to shared outdoor environments.
No preventative treatment for ticks is 100% effective but the use of a drug that rapidly kills ticks such as an isoxazoline (Bravecto™, Nex-Gard®, Simparica™) or repellents, such as pyrethroids, will greatly reduce disease transmission. Removal of ticks with a tick hook using a twist-and-pull action within 24 hours of attachment also reduces Lyme disease and Babe-sia canis transmission (Matjila et al, 2004).
Tapeworm
E. granulosus is zoonotic with hydatid cysts developing in the bone, liver, central nervous system (CNS) and heart. These cysts form after ingestion of eggs passed in the faeces of dogs, and are fluid-filled cysts containing infective tapeworm stages. The increasing hydrostatic pressure and space occupied by these cysts as they grow can lead to pathological bone fractures, CNS damage, and organ damage in infected humans. Dogs in turn are infected through the ingestion of these cysts in sheep and cattle offal. The risk of infection to people is therefore from infective eggs passed in dog faeces. Cats and dogs with flea infestations, that hunt or are on raw unprocessed diets, may also develop large taeniid tapeworm burdens (Wright, 2013).
The prepatent period of E. granulosus is 6 weeks. Therefore, dogs living in endemic areas (Herefordshire, Mid Wales and Western isles of Scotland) should be treated with praziquantel at least every 6 weeks to suppress egg production. Administration of praziquantel 4 times a year reduces zoonotic transmission over time; therefore, this should be recommended in dogs with access to raw unprocessed food, offal or carcasses outside these areas (Craig, 2014). Hunting cats and dogs may require more frequent tapeworm treatment to eliminate segment shedding (Wright, 2013). Prevention of segment shedding due to Dipylidium caninum (D. caninum) infection and zoonotic risk is best achieved through flea control.
Lungworm
A. vasorum is transmitted through the ingestion of slugs and snails, and may cause a range of disease syndromes in dogs. The most common of these is bronchitis and associated cough, but coagulopathies, neuropathies and cardiac disease can also occur. A. vasorum is now thought to be endemic throughout the UK, but distribution is not uniform with some areas remaining free of infection. Infection can be fatal and coagulopathies can therefore be a serious concern in patients planned for surgery. Preventative treatment should be advised in dogs present in known endemic high-prevalence foci. Elsewhere, routine preventative treatment should be employed for at-risk dogs. These include dogs living in areas where cases have been reported, and those that deliberately eat slugs and snails, or serially eat grass. Many slugs are smaller than a 5p piece (Figure 1) and are easily accidentally consumed along with grass. Knowledge of local cases, use of case-distribution maps such as the one compiled by IDEXX, and screening of suspected cases will help to build a picture of whether A. vasorum is prevalent in a particular location. Dogs that have previously been infected should also be routinely treated as there is no lasting protective immunity to lungworm and lifestyle is likely to lead to re-exposure.
Monthly use of a product that is effective against lungworm should be employed for at-risk dogs in the absence of other strategies. This will effectively reduce transmission due to the ubiquitous nature of the mollusc intermediate host. Other measures that have been considered for A. vasorum control include:
- Eradication: this is impractical due to the intermediate host and wildlife reservoirs
- Use of molluscicides: this may increase the risk of exposure due to exposure to dead slugs and snails
- Reduction of exposure to intermediate host: this is difficult due to the ubiquitous nature of gastropod intermediate hosts. Some slugs on grass are very small and may be accidentally consumed by dogs that eat grass
- Use of nematophagous fungi: these fungi predate lungworm larvae, preventing mollusc infection, but they are not currently commercially available
- Picking up dog faeces: this is important in the control of other parasites such as Toxocara spp. but of limited use in A. vasorum control due to wildlife reservoirs.
In the absence of other suitable control strategies, use of preventative lungworm treatment in at-risk dogs is required.
Parasite-control plans
Parasite-control plans are bespoke recommendations for clients regarding routine parasite protection for their pets. Any recommendation needs to be clear and the reasons behind them explained based on consideration of geography and lifestyle factors that will affect parasite infection risk and compliance. Collection of the information required and formulation of these plans can be a practice team effort. Nurses are ideally placed in clinics, at reception, and in consults to acquire this information and formulate a plan. Consistency of message across the practice is vital if the owner is to trust a recommendation and not become confused, which could reduce subsequent compliance.
Risk factors
Treatment every 3 months for Toxocara infection and routine flea treatment frequently enough to prevent egg-laying should be the minimum parasite-control recommendation for any cat or dog. In addition, monthly treatment for Toxocara and preventative treatment for ticks, lungworm and tapeworm may also be required based on risk factors the pet is exposed to. These risks and need for additional protection can be assessed by asking just 3–4 questions in regard to each parasite.
Monthly Toxocara treatment
- Does pet hunt?
- Does pet eat unprocessed raw food or have access to carcasses?
- Are children in the household?
- Are immune suppressed individuals in household?
Requirement for tick treatment
- Does dog walk in Lyme disease ‘hot spot’ areas, high-tick density areas or live in/visit Essex?
- Does dog walk in pasture shared by deer or domestic ruminants, bracken or tall grass?
- Does dog have a history of tick exposure?
Requirement for lungworm prevention
- Does pet deliberately consume slugs or snails?
- Does dog have a history of lungworm infection?
- Is the pet a serial grass consumer?
- Is lungworm prevalent locally on basis of regional cases?
Requirements for tapeworm prevention
- Does pet hunt?
- Does pet eat unprocessed raw food or have access to carcasses?
- Does pet visit/live in E. granulosus endemic area?
Compliance factors
Having established which parasites the pet requires preventative treatment for, factors affecting owner compliance or efficacy of the product also need to be considered. Some useful questions to discuss are:
- Does the owner shampoo the pet or does the pet frequently swim? The efficacy of compounds that are absorbed in the sebum layer such as fipronil and imidacloprid will be affected by sebum-stripping shampoos and may also be affected by frequent swimming which also strips sebum
- Does the owner prefer a tablet, spot-on preparation or collar? Some pets may have a history of skin reactions or vomiting after previous administration of parasite-control products. The owner may also feel more able to apply some forms of medication than others. A product may need to be applied in the surgery to maximise efficacy where all forms of treatment are difficult for the owner to apply
- Is a product licensed for prevention of the parasite in question? If two or more products are equally suitable for parasite control and compliance, a licensed product should be selected first under the cascade.
General recommendations
In addition to advice given regarding preventative treatments for pets, other advice regarding parasite control may be given as part of an overall plan. Examples are.
- Picking up of dog faeces: environmental contamination with dog faeces will lead to increased numbers of ova from potentially zoonotic parasites such as T. canis, E. granulosus and Giardia spp.. Councils have invested substantial amounts of time and money to promote awareness of this with poster campaigns (Figure 2) and to make disposal of faeces easier (Figure 3.). Despite this, a minority of dog owners not picking up their dogs’ faeces and disposing of it in an appropriate manner remains a significant problem. Nurses have a part to play in alerting owners of the risks and promoting responsible behaviour
- Covering of sandpits: to reduce cat faecal contamination (as does covering fruit and vegetables in allotments and gardens). Fresh fruit and vegetables should also be washed thoroughly before raw consumption
- Daily monitoring for ticks and careful removal of ticks with a tick hook: removal of ticks with a tick hook such as the O'Tom Tick Twister® (Figure 4) within 24 hours of attachment reduces the risk of tick-borne disease transmission
- Good hand hygiene: zoonotic infections such as Toxocara spp., Toxoplasma gondii (T. gondii), Giardia spp. and E. granulosus are all predominantly transmitted through the faecal oral route; therefore, good hand hygiene will block their spread. This is an important message to promote as some infections such as Giardia spp. and T. gondii have no effective preventative treatment.
Role of the veterinary nurse
The veterinary nurse plays a vital role in the education of clients on parasite-control plans. Often the veterinary nurse is best placed to discuss parasite control rather than veterinary surgeons, as clients may perceive nurses to be more approachable and feel they can ask questions which they feel vets may consider to be trivial (Yeates, 2014).
Parasite clinics offer the opportunity for nurses to ask questions relating to risk and compliance and build up a picture of the client's needs. Active listening is where the veterinary nurse repeats back to the client what they have said, enabling both the client and veterinary nurse to check understanding, and allow the client to expand on their answers if required (Loftus, 2012).
All patients should undergo a basic head-to-toe examination and should be weighed. If any abnormalities are detected, the patient should be referred to a vet for further examination (Orpet and Welsh, 2011).
A description of the parasite's life cycle will enable clients to better understand the importance of the different stages of prevention. Visual aids and questionaires such as those provided by ESCCAP UK & Ireland (http://www.esccap.org) are useful in helping clients to identify possible parasite risks. The veterinary nurse should also demonstrate how to administer the chosen product(s) and provide the client with written guidance to refer to at home.
Conclusions
Parasite-control plans are becoming more popular due to the increasing parasite threat and risk of disease to both pets and humans (zoonosis). Parasite-control plans allow practical control measures and preventative drug treatments to be individualised for the pet based on their lifestyle and geographical location/level of risk. Through the instigation of veterinary nurse-led parasite clinics, the veterinary nurse plays a vital role in the education of clients, obtainment of relevant information and client compliance. Veterinary nurse clinics not only benefit the patient and client, but also provide the veterinary nurse with increased motivation and job satisfaction.
Key Points
- Veterinary nurses play a vital role in the development of bespoke parasite-control plans.
- Patient wellbeing and client compliance can be improved through the development of these plans in nurse-led parasite prevention clinics.
- Parasite-control plans and recommendations are developed through identification of lifestyle factors that may affect parasite exposure risk and compliance.
- All UK cats and dogs should be treated for fleas and Toxocara as these parasites are ubiquitous and exposure cannot be avoided.
- Geography and lifestyle may also lead to pets requiring routine preventative treatment for ticks, lungworm and tapeworm.