Vet Times The website for the veterinary profession https://www.vettimes.co.uk

Control of , ticks and worms in companion

Author : Hany Elsheikha

Categories : Companion , Vets

Date : January 25, 2016

ABSTRACT

Fleas, ticks and worms are arguably the most prevalent parasite groups in companion animals and can seriously affect their health and welfare if left untreated. Control of these parasites is essential, not only to avoid economic losses and maintain the health and welfare of the pets, but also to protect public health from zoonotic diseases. Mitigating disease threats caused by these parasites are challenging, partly because of uncertainty about disease dynamics in reservoir hosts, the complex mode of transmission and the shift in their epidemiology, which makes it difficult to identify best management approaches.

Despite the existing challenges effective control of these parasites is still possible, but requires the implementation of an integrated approach, which incorporates the judicious use of antiparasitics, non-chemical control measures and informed education of responsible pet owners. Cooperation among veterinarians, parasitology experts and owners who demand the best for their pets is essential if efficient parasite control is to be achieved. This article covers the clinical impact and management of each of these parasite entities.

Dogs are among the earliest domesticated animals, with recent evidence indicating domestication started during the upper palaeolithic period (~35,000 BP). It’s no wonder then occupy a very special place in modern society (Figure 1).

1 / 11 Figure 1. Dogs with their owner having a good time on the beach.

Many people tend to use she, he, her and him pronouns when they chat about their pets and not the normal form it or its. Some owners even write pets into their wills. One survey reported 94% of owners considered their pet to have human-like personality traits and 93% said they would risk their own life for their pet (Galibert et al, 2011).

People not only value live pets, but also robotic animals, such as the robotic baby seal Paro, which is being used therapeutically in the US, and Sony’s Aibo , which has become a popular pet in Japan. The benefits of the human-animal relationship are numerous, including the healing power of pet ownership and its positive influence on ageing, cardiovascular diseases, and behavioural, physiological, and psychological well-being (Havener et al, 2001; Wu et al, 2002; Creagan et al, 2015). A recent study reported significant positive effects of assisted animal therapy (AAT) on the therapeutic progress and recovery process in children and adolescents admitted to the psychiatry hospital for acute mental disorders (Stefanini et al, 2015).

For many reasons there is a growing desire for pet ownership. In the EU, nearly 27% of 70 million households own at least one dog, and in the UK there are about eight million dogs (The European Pet Food Industry Federation, 2012). Pet ownership is also rising in the US (~75 million purebred registered dogs), with nearly 54.4% of all US households owning a dog and 42.9% home to a . Each household spends an average of US$500 (£330) per year on pets, accounting for nearly 1% of the total annual spending for an average income family. Americans are forecast to spend an estimated US$60.59 billion (£40 billion) on their pets in 2015 – up from US$58.04 billion (£38.3

2 / 11 billion) in 2014 (a 4.4% growth rate) despite the economic situation (American Pet Product Association, National Pet Owners Survey, 2015 to 2016), confirming the high value people place on their pets.

Even though pet ownership can enhance the quality of life of people, diseases caused by pet- associated parasites can be shared with humans. With this backdrop, there are increasing concerns among health care professionals, policy makers and the public about the human acquisition of zoonotic diseases from close encounters with pets.

Regardless, people’s interactions with pets are unlikely to diminish. It is, therefore, important to raise awareness among owners and professionals of the parasites so more efficient and pre- emptive measures are put in place to protect animals and humans. The following sections discuss three major parasite groups affecting companion animals and humans – fleas, ticks and worms.

Fleas

Figure 2. An adult .

Ctenocephalides felis (Bouché 1835) is referred to as the (Figure 2) because it was first found on a cat, despite being able to infest approximately 50 of animals, including dogs, , , rabbits and hedgehogs. The dog flea canis is found infrequently on dogs and rarely on , although it may be found more often in more temperate climates, such as the Republic of Ireland. The globally distributed human flea irritans can also attack humans and pets.

Biology

3 / 11 Herein, the biology of fleas will be discussed in some detail because it is fundamental to the effective control of flea infestation. Fleas are holometabolous that complete their life cycle from to adult through larval and pupal stages (Figure 3). Once on a host, fleas begin feeding within minutes and soon after begin breeding. A female flea can start laying pearly white (20 to 50 eggs/day) within one to two days of jumping on to a host. Flea eggs fall off the host into the environment and larvae hatch in three to five days under appropriate conditions.

Flea larvae develop through three larval stages; however, most larvae do not survive to become adult fleas. The larvae (mostly L3) are photophobic and thus can be found hidden in places, such as under carpets. Fully mature larvae spin a cocoon and pupate. Following development the adult emerges from the pupal case immediately or may be delayed for about six months in the absence of appropriate stimuli, such as pressure, increased temperature and CO2. Newly emerged adult fleas actively seek a host, although, in the absence of a host, they can only survive for a few days. Adult female fleas require a large amount of blood (~15 times their bodyweight in blood each day) to feed their offspring because their larvae feed mostly on digested blood in flea faeces.

The maximal recorded longevity is 160 days, but most fleas survive for about one to three weeks as they are groomed out of the host. Depending on the temperature, it can take three weeks to several months for the infestation to run its course. Because the pupae is in the environment and cannot be eliminated by , this results in the environmental infestation being difficult to control and could take 90 days or more with indoor infestations and often cannot be eliminated outdoors.

Clinical importance

Flea infestation is a common cause of pruritus (itching) and irritation and, in severe infestation, skin lesions and hair loss. Fleas can also feed on humans temporarily if they cannot find a dog or a cat host, which manifest as small red bites around the ankle/calf region. Because fleas feed on the pet’s blood it is possible for them to cause iron deficiency, anaemia and even death in very small kittens and puppies or in pets that are ill for other concomitant reasons.

Some cats and dogs suffer from an allergy to the flea dirt and/or salivary proteins during the act of feeding, leading to flea allergy dermatitis, which is one of the most common and serious skin diseases in dogs and a major cause of feline miliary dermatitis.

Management

4 / 11 Figure 3. Life cycle of fleas showing all its forms – egg, , and adult.

Insecticides are the mainstay in the management of fleas. Anti-flea products can be divided into adulticides (those that kill adult fleas) and growth regulators (IGR; those which prevent the development of flea eggs and larvae). In the past few decades, significant progress has been made in the development of insecticides against fleas and the number of safe and effective host-targeted flea-control compounds has increased.

A wide range of anti-flea products are available to the pet owner who is looking for effective flea control, such as dusts, collars, bombs, foggers, sprays, spot-ons and oral formulations. The main groups of insecticides in use against fleas include topical (imidacloprid, dinotefuran, pyriprole, fipronil, metaflumizone, selamectin) and oral (spinosad, nitenpyram) adulticides. Some adulticides may also have an effect on flea eggs or larvae with direct contact.

Some flea control formulations combine adulticides with IGRs (for example, methoprene, pyriproxyfen) or insect development inhibitors (IDI; for example, lufenuron). Methoprene and pyriproxyfen act by mimicking insect growth hormone, preventing immature stages from developing into the next life stage. Lufenuron acts by preventing the egg tooth from hardening, such that the larva cannot hatch from the egg.

Two methods of applying IGRs can be used. Whether directly in the environment – for example, in the form of sprays, foggers or bombs typically used for existing infestations – or when used in combination with an adulticide on the animal, they prevent infestations by putting a barrier in the reproductive flow.

Although most adulticides will kill fleas within 24 hours before egg laying begins, owner compliance is generally poor, hence some fleas will survive for long enough to lay eggs at the end of the

5 / 11 treatment interval. The presence of an IGR on the pet at this stage will render the eggs that can be laid non-viable, and thus unable to cause a household infestation.

Considerations when choosing a chemical product include the drug’s mode of action, spectrum of activity, mode of application, speed of action required, efficacy/duration/frequency of reapplication (that is effect of wetting/bathing), resistance, target species to be treated, withdrawal periods, age restrictions, contraindications/drug interactions, cost, and ecotoxicity to non-target species.

The best flea control results can be obtained via the implementation of an integrated flea control approach, which is based on the application of the following steps:

1. Use an effective and long-lasting adulticide to kill fleas on the animal. 2. Use an IGR to prevent the development of flea eggs, larvae and pupae in the home. 3. Mechanical control methods, such as vacuuming the carpets, furniture cushions and rugs regularly, increasing heat and humidity within the home and washing the pet’s bedding (>60°C). 4. Raise awareness with the pet owner of the understanding of the flea life cycle within the home environment.

Because adult fleas are only 5% of the flea problem, considerable time and effort needs to be placed on controlling environmental stages. The need for using host-targeted and environmental insecticides, and non-chemical means of reducing or eliminating environmental flea stages present in the pet’s environment, has led to the combined use of an animal adulticide/repellent together with a separate environmental flea control regimen. By attacking the problem from different angles, owners can ensure they are combating each stage of the flea life cycle.

Ticks

6 / 11 Figure 4. The mouthparts is the blood-feeding apparatus of the tick and the organ responsible for disease transmission.

Ticks have been known as a source of disease for more than a century (Swanson et al, 2006) and today no country is safe from the threat caused by these pests. Ticks are temporary ectoparasites because they attach to the host for a short period of time to take a blood meal. However, due to their haematophagous (blood-feeding) nature, ticks have a remarkable ability to transmit a wide variety of pathogens to animals and humans compared with any other vectors.

Ticks can transmit pathogens biologically, with the pathogen developing within the tick. They can also transmit infectious (bacterial, viral and protozoal) pathogens to the host mechanically when they move from one host to another and their mouthparts (Figure 4) are soiled with blood- containing germs.

More than 900 tick species have been identified, with some more prevalent than others. Ixodes ricinus (sheep tick, pasture tick or deer tick) and Ixodes hexagonus (hedgehog tick) are the most prevalent and widely distributed ticks seen on companion animals or humans. A third species, Ixodes canisuga, feeds on dogs and is known to be associated with boarding kennels. Of the three tick species, I ricinus is the most efficient vector of tick-borne diseases (TBD) and has been reported on dogs across the UK. Also, its range is expanding northwards and increasing in abundance due to the warmer, wetter winters; I hexagonus appears to be a more southerly species (Smith et al, 2011).

Interestingly, Dermacentor reticulatus, regarded as a continental species, has been reported in the southern parts of England, representing a newly established population besides foci formerly identified on the Welsh coast and the Welsh border with Shropshire. These facts indicate the epidemiology of ticks and TBDs has changed during the past few decades, which has probably

7 / 11 been driven by the increasing travel of companion animals, climate change (Gray et al, 2009), changes in land use and increasing wildlife populations. The same factors also increase the risk of introducing exotic ticks – particularly D reticulatus and Rhipicephalus sanguineus.

Further information and advice to pet owners and animal care professionals is provided from The European Scientific Counsel for Companion Animal Parasites UK (ESCCAPUK) website.

Management

The majority of tick-prevention programmes stress habitat modification (for example, burning tick habitat, leaf litter and so on) and adopting protective measures, such as avoiding tick habitats, including knowledge of when people can be at risk, avoiding heavily wooded and grassy areas, wearing protective clothing (especially during the time of highest tick activity), using repellents, and frequent tick checks (at least one every 24 hours) to locate and remove ticks before they can transmit disease.

A number of anti-tick products can be used to reduce the risk of exposure of pets to ticks. Check the latest product information provided by the manufacturer of each drug for relevant species of tick, adverse effects, required duration of action, potential for drug interactions, accidental contact and so on. Some of the disease prevention products need to be administered well before potential exposure to the disease-causing agents. An assessment of the risks facing each pet is required and will depend on which country/countries the pet will be visiting and the season of year the travel will be scheduled.

Further information on tick control, including the anti-tick products available, can be found on the ESCCAPUK website. Tick treatment of companion animals entering the UK, although not obligatory, is still needed to protect travelling and resident pets.

Worms (helminths)

Dogs and cats are host to many helminthic parasites, which have the pathogenic capacity to cause intestinal and extra-intestinal diseases. For example, the respiratory nematodes (the canine Angiostrongylus vasorum species and the feline Aelurostrongylus abstrusus species) or the intestinal species – such as the roundworm Toxocara canis, the hookworm Ancylostoma caninum, and the whipworm Trichuris vulpis – are important to animal health because of their high prevalence and significant clinical impact.

Canids infected with A vasorum (Figure 5) exhibit persistent cough, dyspnoea, pneumonia, arrhythmias, thrombosis, disseminated intravascular coagulation and, in severe cases, death. The hookworm A caninum can cause intestinal pathologies, bleeding and anaemia, and can accidentally infect humans, leading to cutaneous larva migrans. Zoonotic transmission of T canis to humans usually occurs through the ingestion of infective embryonated/larvated eggs present in

8 / 11 contaminated soil, unwashed hands or raw vegetables. Within humans Toxocara larvae emerge from eggs and migrate through the body, causing damage to the tissues they encounter.

Management

Figure 5. The respiratory canine nematode Angiostrongylus vasorum species in the heart of a .

Anthelmintics play the largest role in the management of worm infections. A large number of anthelmintic products, with various mechanisms of action, are available to treat various worm infections. Some are endectocides, made either by having one active ingredient with a broad spectrum of activity or by combining active ingredients.

Veterinarians are often faced with the need to treat and prevent both ectoparasites (fleas or ticks) and endoparasites (intestinal and cardiorespiratory worms). In this case endectocide products can be used to control both worms and ectoparasites. The precise spectrum of activity varies according to the active ingredients. Matching the spectrum of activity to the infection present, or the risk for individual animals, is a key part of managing a parasite infection. Remember, what is needed is a balance between minimising zoonotic and animal health risk while managing environmental contamination and minimising the risk of selection for drug resistance.

Apart from evidence of resistance to pyrantel in canine hookworms, drug resistance has not been reported for pet worms, perhaps because of a decreased intensity of treatment compared to farm animals. Therefore, the cost of treatment and the potential for resistance selection must be balanced against the health risks to achieve a management regimen that works well for an

9 / 11 individual animal or group of animals.

The drugs used for treatment or prevention of companion animal parasites, including active ingredients and the spectrum of activity of products in the NOAH compendium, are available on the ESCCAP website.

Despite the efficacy of anthelmintic therapeutic interventions (pharmacological therapy) using dewormers, along with other (non-pharmacologic therapies) modalities, including evidence-based treatment, tailored treatment, accurate and timely diagnosis, and engaging pet owners and veterinary professionals, should be instituted to provide optimal parasite management outcomes with the least possible risk.

Conclusions

While not all companion animal parasites carry the same public health profile, they all have potential to cause disease and continue to present challenges to animal and human health. Not only has there been emerging evidence of antiparasitic resistance, but the epidemiology of these parasites also continues to change and the risk of clinical infections with fleas, ticks and worms is unlikely to diminish.

The expanding geographic distribution of these parasites and the increasing number of clinical (including exotic) cases indicates more effective measures are needed to manage these diseases. Given the large number of pets in the UK, and the bond between pets and owners, the need for understanding and preventing the diseases these companions bring with them are eminent.

Veterinarians, parasitologists, physicians and pet owners should be aware of the factors that increase risk of exposure to fleas or ticks and their associated diseases and should employ effective measures to prevent the spread of these diseases.

Acknowledgements

The author declares he has no competing interests associated with this publication.

Because of space limitation, he notes he was unable to comprehensively cite many worthy contributions to the field.

References

Creagan ET, Bauer BA, Thomley BS and Borg JM (2015). Animal-assisted therapy at Mayo Clinic: the time is now, Complement Ther Clin Pract 21(2): 101-104. Galibert F, Quignon P, Hitte C, André C (2011). Toward understanding dog evolutionary and domestication history, C R Biol 334(3): 190-196.

10 / 11 Gray JS, Dautel H, Estrada-Peña A, Kahl O and Lindgren E (2009). Effects of climate change on ticks and tick-borne diseases in Europe, Interdiscip Perspect Infect Dis 2009: 593232. Havener L, Gentes L, Thaler B, Megel ME, Baun MM, Driscoll FA et al (2001). The effects of a companion animal on distress in children undergoing dental procedures, Issues Compr Pediatr Nurs 24(2): 137-152. Smith FD, Ballantyne R, Morgan ER and Wall R (2011). Prevalence, distribution and risk associated with tick infestation of dogs in Great Britain, Med Vet Entomol 25(4): 377-384. Stefanini MC, Martino A, Allori P, Galeotti F and Tani F (2015). The use of animal-assisted therapy in adolescents with acute mental disorders: a randomized controlled study, Complement Ther Clin Pract 21(1): 42-46. Swanson SJ, Neitzel D, Reed KD and Belongia EA (2006). Coinfections acquired from Ixodes ticks, Clin Microbiol Rev 19(4): 708-727. The European Pet Food Industry Federation (2012). Facts and Figures 2012, www.fediaf.org Wu AS, Niedra R, Pendergast L, McCrindle BW (2002). Acceptability and impact of pet visitation on a pediatric cardiology inpatient unit, J Pediatr Nurs 17(5): 354-362.

11 / 11

Powered by TCPDF (www.tcpdf.org)