Fleas and Ticks: How to Instigate Effective Prophylactic Regimes
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Vet Times The website for the veterinary profession https://www.vettimes.co.uk Fleas and ticks: how to instigate effective prophylactic regimes Author : Jenny Helm Categories : Clinical, RVNs Date : March 12, 2015 Flea infestation is a common concern among pet owners; nevertheless, many owners fail to implement an effective anti-flea strategy (perhaps by buying ineffective products, overlooking treating all life stages/the home environment or simply forgetting to apply the products within a suitable time frame). Figure 1. A tick removed from a dog. To facilitate establishment of a good anti-flea strategy, it helps to understand a little about these ectoparasites. Why worry about fleas? Fleas are small, yellow, brown or black wingless insects that have incredibly powerful legs, enabling them to jump up to 200 times their own height. They belong to the order Siphonaptera and, as such, can parasitise many species of mammals and birds. They are permanent parasites that have no need to leave their hosts to complete their life cycle. Several species of fleas exist in the UK. These include: 1 / 10 Ctenocephalides canis (the dog flea, rarely affects cats) Ctenocephalides felis (the cat flea, but also commonly infests dogs) Archaeopsylla erinacei (the hedgehog flea, but very occasionally also found on dogs) Spilopsyllus cuniculi (the rabbit flea, but very occasionally also found on dogs) Pulex irritans (the human flea, but very occasionally also found on dogs) Flea diseases To implement a successful anti-flea strategy, pet owners should be made aware of the impact of flea infestation on the household and the diseases fleas may cause both in animals and humans (especially children) living alongside their pets. Flea-bite dermatitis Flea-bite dermatitis can affect cats and dogs, and causes pruritus, alopecia and crusting – commonly along the back – due to trauma caused by the pet scratching or nibbling itself. Flea allergy dermatitis/flea-bite hypersensitivity Figure 2. Flea allergy dermatitis on a cat. Flea allergy dermatitis/flea-bite hypersensitivity causes more severe skin signs compared to flea- bite dermatitis and is caused by the animal’s own immune system having an exaggerated response to flea infestation. It is the most common dermatologic disease of dogs and also often affects cats (Dryden, 2009). The disease causes alopecia, pruritus and can lead to moist dermatitis, with redness and intense skin inflammation (Figure 2). Transfer of Dipylidium caninum 2 / 10 The flea acts as an intermediate host for the tapeworm Dipylidium caninum. If a flea infected with this tapeworm is eaten by a cat or dog (often during grooming) an adult tapeworm can form within its intestines. This tapeworm can cause an itchy anus (owners may see their pets “scooting” across the floor) or gastrointestinal upset (vomiting, diarrhoea and/or weight loss). Blood loss anaemia Very heavy flea infestation may cause blood loss and, consequently, iron deficiency anaemia – especially in young puppies or kittens. However, thankfully this is a very rare sequelae. Transfer of infectious anaemia Other infectious agents may also be transferred by fleas; these include Bartonella henselae (the cause of cat-scratch disease), Mycoplasma haemofelis, other haemoplasmas and rickettsiae, and possibly even feline leukaemia virus. Transmission of these pathogens can cause several clinical signs (including anaemia, lethargy, joint disease and weight loss). Impact on human health Fleas can also bite humans, which can cause intense itching and discomfort. Painful, more severe reactions may occur if an individual is allergic or hypersensitive to flea bites and secondary bacterial infection may occur if the bites are scratched. Why worry about ticks? 3 / 10 Table 1. The scientific classification of ticks Ticks are obligate blood-feeding ectoparasites that can parasitise a variety of mammals, birds, reptiles and amphibians. Their scientific classification is shown in Table 1. They can be seen with the naked eye, but their exact colour and size depends on their species, gender, life stage and also how much they have fed (Figure 1). There are many species of tick in the UK (in fact, 700-plus species exist around the world). These species are usually divided into two groups depending on the density of their body wall – hard ticks and soft ticks. Soft ticks are so called because of their soft backs, which reach forward and form a hood over the tick’s mouthparts (making it impossible to see from above), whereas the hard tick has a hard, plate-like back and its mouthparts are seen easily from both above and below the tick. Ixodes ricinus (the European sheep tick) is the most common species in northern and central Europe, and is, therefore, the most important tick in the UK. It is known as the three-host tick, meaning three separate hosts are required for each life cycle stage. Its life cycle takes about three years to be completed, with each stage taking about one year. 4 / 10 Ixodes hexagonus (the hedgehog tick) is the second most common tick of dogs in the UK. Out of the 20 species of tick found here, the sheep and hedgehog tick are the most likely to cause illness in pets and people. Life cycle Ticks are arachnids (like spiders, scorpions and mites) and, as such, have eight legs. However, ticks hatch from their eggs as larvae, with only six legs. These newly hatched larvae look for a host to feed on (quite often a rodent or a bird) before moulting to become nymphs. They then feed once more before moulting again to become adults. While on the final host (quite often a large mammal, which could be a dog or cat) the female tick feeds. During this time its eggs are fertilised by the male while they are both still on the host. The female then falls from the host and lays its eggs in the environment for the life cycle to start over again. Importantly, all life cycle stages can potentially attach to and feed from humans and/or pets. This is a description of the basic life cycle of the Ixodes ticks; different ticks have different feeding and breeding habits. Ticks may live for only a few months to several years. Acquiring a tick infestation Ticks usually use wildlife (often deer, small mammals and foxes) and livestock as hosts during times of feeding; however, pets and humans can be affected by ticks when walking in areas of tick habitation. Acquiring tick infestation is considered high risk when walking in “wilderness” locations as ticks are often found on grass, leaf litter and low plants, which are mostly present in forests, wooded areas or moorland. However, it is also possible to acquire ticks from some suburban areas, urban parkland and even household gardens. Most infestations are highest in spring and early summer, then again in autumn, although tick infection is possible all year round during milder weather (higher than 3.5°C). Safe tick removal 5 / 10 Figure 3. A recommended tick removal device. Safe tick removal is essential; if a tick is unduly stressed or injured during removal then transmission of disease from the tick to the host animal is much more likely. The body, small head and mouth parts, which are often buried into the host’s epidermis, must be removed in their entirety. To avoid bursting or causing stress to the tick, older techniques such as applying petroleum jelly, alcohol or burning should be avoided. In ideal circumstances a specific tick removal device should be used (Figure 3); however, fine-point tweezers or forceps may serve as a suitable alternative. Previously, it was thought ticks needed to attach for more than 48 hours to transmit diseases such as ehrlichiosis or borreliosis; however, reports suggest this may not be the case (Kidd and Breitschwerdt, 2003; Nicholson et al, 2010). The author would recommend, where feasible, ticks are removed (as described previously) as soon as they are observed and, if possible, within 24 hours. To prevent any attachment at all, owners should be encouraged to use veterinary recommended tick repellant products for their pets. 6 / 10 Tick-borne disease Ticks are second only to mosquitoes in their ability to transmit disease to animals and humans. Because they feed on blood they are well positioned to transmit diseases caused by infectious agents such as viruses, bacteria and protozoa. Table 2. Examples of tick-borne diseases It is very probable, in years to come, tick-borne disease will become more of a concern for UK veterinary practices and pet owners. This is due to the geographical expansion of tick-borne disease and, as such, disease is emerging in previously unaffected areas. Factors causing this include increasing transportation of pets (for sport, leisure activities or simply taking pets on holiday); climate change, which may increase the density of vectors in an area or cause them to drift northwards; increasing urban sprawl with increased proportions of wildlife reservoirs having a closer association with human and pet activity (for example, the expansions of urban fox populations); and changes in farming practices (banning of certain sheep dips for example). Table 2 lists some of the tick-transmitted diseases. Ticks can also cause bacterial infection at the attachment site and/or anaemia if there is a very high burden. 7 / 10 Flea and tick prevention protocols When promoting effective flea control, it is of vital importance to consider the pet (or all pets in a multi-animal household) and the environment. Our modern household environments, with double glazing and cozy soft furnishings, are ideal for fleas to complete their life cycles. Given the optimal temperatures for completion of the flea life cycle are approximately 18°C to 25°C, our modern, centrally heated homes support this perfectly and mean flea infestation is now a year-round problem.