Worming: Key Decision Factors and Ways to Improve Compliance

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Worming: key decision factors and ways to improve compliance

Author : Emma Gerrard

Categories : RVNs

Date : February 1, 2013

Emma Gerrard DipAVN(Small animal), DipHE, CVN, BSc(Hons), RVN, K-SQP, PHC reviews UK endoparasites and looks at ways of engaging clients

Summary

WHEN choosing appropriate worming treatments and the frequency of administration, it is important to determine which parasites pose a threat to the animal in the area it lives in. An assessment should take place to establish the risk level based on the interactions between the pet, the owner and the environment. Inadequate worming has serious implications for both the animal’s health and from the perspective of zoonotic disease. Therefore, it is important to ensure owners understand why they need to regularly treat their pets with an appropriate worming product.

Key words

Endoparasites, pet lifestyle, compliance, wormer, VN clinic

VETERINARY nurses (VNs) are perfectly placed to offer information on worming to clients because they can provide a good, informative service and, ultimately, become the first port of call for worming queries and advice. First and foremost, it’s important that VNs can confidently speak to clients about why worming matters and develop a holistic approach for each pet to ensure each individual’s needs are met. This holistic approach to worming should take into account an animal’s lifestyle and its owner’s ability to carry out any suggested worming protocol. This must

1 / 10 then extend to practice reminder systems, which can, ultimately, result in improved owner compliance.

Why should we worm?

There are several reasons why it is important to worm pets:

• public health;

• animal health; and

• aesthetic reasons.

Endoparasites of dogs and cats in the UK

Cestodes (tapeworms)

Tapeworms do not cause harm to their hosts unless present in large numbers; however, treatment is important for hygiene reasons and because some species are zoonotic. Tapeworms – both in their fully grown and larval (cystic) stages – pose a threat to the health of the animal and humans when they act as accidental host, after eggs are ingested.

There are three main types of cestode:

• Dipylidium canium;

• Echinococcus granulosus; and

• Taenia species.

Dipylidium caninum

This is the most common helminth and affects both dogs and cats. Adult worms live in the intestine and can grow up to 50cm in length. Eggs are passed in motile egg capsules in the faeces and are ingested by the flea larvae, which is the intermediate host. The life cycle is completed when the flea is ingested by an animal during grooming, which emphasises the importance of incorporating flea and tapeworm treatments together. This must be discussed when developing a parasite programme for an animal.

Taenia species

Numerous species of this tapeworm exist, some of which are responsible for serious infections in

2 / 10 humans. Animals that have access to raw meat, such as farm dogs and hunting cats, can become infected and, in turn, cause infection of intermediate hosts (sheep and cattle), with a cystic stage. These cysts affect the brain, liver or muscles of the intermediate hosts (Figure 1). This can be seen in sheep, where the worm migrates to the brain, causing a condition called gid. Sheep dogs should, therefore, be treated with a broad spectrum anthelmintic.

Echinococcus granulosus

This is a rare cestode of dogs that may be found in parts of Wales and the Hebrides (Swanton and Wildsmith, 2008) and it is an important zoonosis. Humans who ingest a proglottid or egg may act as an intermediate host, in which the larval stage may present as hydatid cysts in the lungs or liver. Sheep are the most common intermediate host and are infected when eggs are ingested from their environment.

Nematodes

Ascarids (roundworms)

• Toxocara cati;

• Toxocara canis; and

• Toxascaris leonina.

Hookworms (canine)

• Uncinaria stenocephala (fox hookworm or northern hookworm).

Whipworms

• Trichuris vulpis.

Cardiovasular system

• Dirofilaria immitis; and

• Angiostrongylus vasorum (lungworm/French heartworm).

Lungworms

• Aelurostrongylus abstrusus; and

3 / 10 • Oslerus osleri.

Urinary

• Capillaria plica (bladder worm).

Toxocara canis

T canisis a significant ascarid because of its zoonotic potential and the disease it causes in puppies. Adult worms can grow up to 10cm in length and infection can occur via three routes.

Adult dogs ingest infective eggs from the environment through contact with faecal matter. Worms develop in the intestine and eggs are shed in the faeces. Eggs can take several weeks to become infective – exact time is dependent on environmental temperature.

After ingestion of infective eggs, larvae can migrate to different tissues and during pregnancy these larvae cross the placenta, infecting unborn puppies. Larvae will also pass to puppies in milk during lactation.

Infected puppies can suffer as larvae migrate via the liver to the trachea and are coughed up and swallowed, developing into adult worms in the intestines. Large numbers of worms are then present in the faeces of puppies.

Most dogs are asymptomatic, but puppies with a heavy worm burden can have diarrhoea and the typical pot-bellied appearance. Some puppies may also present with respiratory symptoms, such as coughing or tachypnoea due to large numbers of migrating larvae. Further clinical signs can include vomiting, anaemia, intestinal obstruction and is potentially fatal.

Humans who ingest T canis eggs or larvae are at risk of potentially serious disease and there are two recognised types of disease in humans:

• Ocular larval migrans occurs when larvae migrate to the eye, leading to pain and, potentially, blindness.

• Toxocariasis or visceral larva migrans is an illness caused by larvae migrating to organs through the blood stream where they encapsulate themselves in the connective tissue. Symptoms differ according to the organ affected, but may include blindness, hepatomegaly, asthma-like symptoms, central nervous system disorders and lameness. It was thought that only T canis could cause disease in humans; however, there is evidence to suggest that T cati can also pose health risks to humans (Fisher, 2003).

Toxocara cati

4 / 10 T cati (Figure 2) is similar to T canis, where eggs can remain in the environment for long periods of time, with the potential to cause human infection. However, this occurs less frequently than with T canis. Larvae are transmitted via the mother’s milk (not the placenta) in kittens and older cats by ingesting the paratenic host. Clinical signs in kittens can be respiratory, as larvae migrate to the lungs, or intestinal, such as poor growth, a pot-bellied appearance or diarrhoea. Adult cats often have no clinical signs of infection but they may vomit up worms. Cats are easily infected because of their tendency to roam and their hunting activities.

Toxascaris leonina

This ascarid is less common and may be seen in adolescence. The infection is passed on when the definitive host (dog, cat or fox) eats the intermediate host (rodents or birds), allowing ingested eggs to hatch into the intestines, developing into adult worms.

Uncinaria stenocephala

This worm affects dogs, with the main route of infection via ingestion of larvae, which can be present in damp sandy soil. Adult hookworms embed in the intestinal wall of the large intestine. Low numbers of worms may be well tolerated, but a heavy infection can result in bloody diarrhoea and low-grade anaemia. Children and adults fond of gardening or lying on beaches where dogs are walked may be at increased risk from zoonotic infection.

Angiostrongylus vasorum

A vasorum (Figure 3) is seen in dogs and has recently been found to be of increasing prevalence across the UK (Helm et al, 2009; Yamakawa et al, 2009). Adults live in the pulmonary artery and cause serious disease associated with many clinical signs and may be fatal. The intermediate hosts are slugs and snails, although frogs may act as paratenic hosts.

Infection with this worm may cause multisystemic clinical signs. Signs may include respiratory disorders, exercise intolerance, haemorrhagic diathesis and cardiac failure (Perry et al, 1991), all of which are variable and inconsistent.

Cardiorespiratory signs vary from mild coughing and gagging to severe exercise intolerance, dyspnoea, tachypnoea, and cyanosis. Right-sided congestive heart failure may develop as a result of chronic lung disease and subsequent pulmonary hypertension, and coagulopathies can include excessive bleeding from minor wounds, epistaxis, ocular bleeds and anaemia. Neurological signs can include seizures, behavioural changes, cranial nerve deficits and ambulatory problems.

Lifestyle considerations

5 / 10 It is important to establish the lifestyle of the pet and consider the environment in which it resides, so that the VN can advise the client on the correct worming protocol. Certain factors will require a more intense approach to worming, whereas others may indicate a less aggressive programme.

The following factors must be considered when devising a worming programme:

• animal’s age;

• reproductive status;

• history;

• health status;

• environment;

• nutrition;

• location; and

• travel.

Adult animals

An active adult dog or cat that hunts and scavenges and is regularly outdoors – for example, a working dog or farm cat – will have different requirements from an animal that is walked on a lead or spends a lot of time indoors. The former will very often have access to rodents, slugs, snails, raw fish and meat – including viscera, placenta and aborted foetuses – and may be at risk of acquiring endoparasites such as Taenia species, A vasorum, and E granulosus.

Reproductive status

Pregnant and lactating bitches may pass on T canis larvae in utero or via milk. Lactating queens may pass on T cati in their milk to suckling kittens.

Puppies and kittens

Puppies and kittens under six months of age require a different approach to worming, depending on the type of wormer being prescribed and/or dispensed. The usual recommended protocol for puppies and kittens is to worm monthly from two weeks of age in puppies and three weeks of age in kittens (ESCCAP, 2010). This is because Toxocara is usually present in puppies and kittens from these ages. It is essential to worm from an early age because Toxocara causes serious

6 / 10 diseases in young animals and almost all will be infected.

Children and pets

Good personal hygiene should be encouraged, especially for children, and advice should include washing hands after handling animals, discouraging face licking and ensuring nails are kept short. It should also be advised that children’s play areas are well fenced off and sand pits are covered.

Pet Travel Scheme (PETS)

Animals that are travelling to certain geographic areas, such as for holidays, house moves, in kennels or for shows, may be at increased risk of infection from non-UK parasites. For example, Echinococcus granulosus has been found in parts of Wales and the Hebrides (Swanton and Wildsmith, 2008).

Under PETS, it is mandatory for dogs to be treated for tapeworm. For dogs entering the UK after travel, a treatment for tapeworms containing praziquantel is essential. The treatment must be administered by a veterinary surgeon not less than 24 hours and not more than 120 hours (one to five days) before its scheduled arrival in the UK (DEFRA, 2012). It is therefore important to advise clients about the appropriate endoparasite protocols.

Two main types of worm should be discussed with owners of travelling pets:

• Echinococcus multilocularis; and

• Dirofilaria immitis.

Echinococcus multilocularis

This is similar to E granulosus in that it also causes hydatid cysts. Currently it is not in the UK, but it is endemic in continental Europe. The intermediate hosts are rodents, with foxes as the final host, and it can infect dogs and cats to a lesser extent. To prevent E multilocularis becoming established in the UK, it is a requirement that pets travelling under PETS are treated against tapeworms before they enter the country, because of its zoonotic risk.

Dirofilaria immitis

This is the largest worm and is commonly referred to as the heartworm. It affects dogs and occasionally cats. The intermediate host is the mosquito; therefore, it is not endemic in the UK. However, climatic changes favourable to parasitic development and an increase in travelling pets have increased the risk of infection (ESCCAP, 2010). Pets travelling to other parts of the world, such as southern Europe, the United States and Australia, should be treated with a suitable broad

7 / 10 spectrum anthelmintic. Adult worms live in the pulmonary artery and right ventricle of the heart, where they cause significant disease, weight loss, immunosuppression and heart failure.

Nurse clinics

Preventive health care clinics provide the VN and client time to discuss a pet’s lifestyle and allow the appropriate worming advice to be given and protocols to be drawn up tailored to the needs of both pet and client. Inviting clients into the practice is an effective way of giving worming advice, among other things.

Puppy and kitten clinics and puppy parties are an excellent means of passing on information and clients with new pets are often enthusiastic and eager to learn about all aspects of preventive health care. Many clients are more comfortable discussing matters with VNs, being reluctant to “take up too much of the vet’s time”, so second vaccination clinics are also good opportunities to get the message across.

Parasite clinics are another great way of getting clients into the surgery. These are often useful for clients who are unable to medicate their pets, and who are impressed when a VN administers a worming tablet with ease. Nurse clinics may be promoted through interesting and eyecatching notice boards within the waiting area. These are ideal when trying to get the clients’ attention and they encourage questions during the clinic. Drug manufacturers often run campaigns and/or have promotional materials available to support preventive health campaigns in practice.

Owner compliance

Owners often forget to worm their pets and may only be reminded when parasites are seen. The use of reminders can help to increase owner compliance for treating their pets with preventive worm treatments. It is vital to educate owners about the importance of a regular worming programme to protect their pets, other animals and people from the risk of disease.

VNs should advise owners on the implementation of individual worming programmes, based on a pet’s lifestyle and then follow on with treatment reminders, which is an excellent way to improve client compliance. Continual engagement with the subject of worming is paramount and this is where the different types of reminder come into play. They are used to reiterate the importance of worming, offer regular worming treatments and provide information and advice. Benefits of improved levels of client care through the implementation of a worming protocol will not only provide a value-added service, but will ultimately increase client satisfaction, aid client compliance and boost loyalty, as well as increase wormer sales and practice profitability.

Worming frequency

8 / 10 ESCCAP recommends that dogs and cats are wormed every three months with a reputable anthelmintic to ensure they are worm free and to prevent shedding of eggs into the environment. In increased risk, such as kennels or households where there are children, monthly treatments may minimise the risk of infection. Cats that hunt should be wormed on a monthly basis, while breeding/lactating bitches and queens should be wormed accordingly to reduce the risk of infecting puppies and kittens. Puppies should start to be wormed from two weeks of age, with two-weekly treatments until they are 12 weeks old, reducing to monthly treatments until they are six months old and then three-monthly treatments.

Kittens should begin a fortnightly worming programme from three weeks of age; this is because prenatal infection does not occur in kittens. Treatment should continue every two weeks until weaning, then monthly until six months of age. A programme should then be developed according to a cat’s lifestyle. Treatments should be given according to the manufacturer’s recommendations (Table 1).

Conclusions

In compliance with the BSAVA’s assessment criteria and guidelines for worming, comprehensive parasite prevention programmes can be designed in the practice to meet a pet and owner’s needs. This makes it necessary to assess a pet’s needs on a case-by-case basis. A benefit-risk assessment of each individual case should determine both choice of anthelmintic, spectrum of anthelmintic activity and frequency of administration. In cases where zoonotic potential is high risk or increased, maximum control according to the manufacturer’s recommendation is recommended. In other cases, the risk of reinfection may be so low as to recommend intermittent anthelmintic therapy with longer treatment intervals. Information about the local environmental risk should determine the spectrum of anthelmintic used – for example, anthelmintics for lungworm prevention.

References and further reading

Fisher M (2003). Toxocara cati: an underestimated zoonotic agent, Trends in Parasitology, 19(4): 167-170. Gerrard E (2012). Worming – the many ways of sending reminders and maintaining client compliance, VN Times 12(8): 8-10. Gerrard E (2012). Worms in companion animals – the types, their life cycles and the anthelmintics available to treat them, Animal Health Advisor 1(1): 6-8. Helm J, Gilleard JS, Jackson M et al (2009). A case of canine Angiostrongylus vasorum in Scotland confirmed by PCR and sequence analysis, JSAP 50(5): 255-259. Morgan E and Shaw S (2010). Angiostrongylus vasorum infection in dogs: continuing spread and developments in diagnosis and treatment, JSAP 51(12): 616-621. Perry W A, Hertling R and Kennedy M J (1991). Angiostrongylosis with disseminated larval infection associated with signs of ocular and nervous disease in an imported dog, Can Vet J

9 / 10 32(7): 430-431. Swanton S and Wildsmith J (2008). Prevalence of the hydatid diseasecausing tapeworm Echinococcus granulosus among stray dogs in southeast Wales, United Kingdom www.cieh.org/jehr/prevalence_of_hydatid_ disease-causing_tapeworm_echinococcus.html Yamakawa Y, McGarry J W, Denk D et al (2009). Emerging canine angiostrongylosis in northern England: Five fatal cases, Veterinary Record 164: 149-152.

Reviewed by Mark Overend, BVMS, GPCert(Cardio), MRCVS

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