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