Controlling of Fleas, Mites & Lice in Cats and Dogs

Cats and dogs are susceptible to many external parasites, the level depending on the environment, the time of the year, contact with others and habitat to name but a few. This guide outlines the most common external parasites and how to control them.

Mange Mites

There are numerous mange mites, some of which are species specifi c. The entire life cycle of the mange mite takes place on the animal or within its skin, but many of the stages can remain infective for several days off the animal. Animal to animal contact is not always necessary for transmission therefore and the environment often harbours the parasite while off the host animal.

There are three types of mites:em>

1. Surface mites – i.e. those that live in surface skin debris e.g. Chorioptes and Cheyletiella.
2. Those that tunnel into the skin surfaces, e.g. Sarcoptes (Scabies)
3. Those that live deep in hair follicles e.g. Demodex.

All mange mites are tiny and on careful inspection they may appear like walking scurf. It is normal for skin scrapings and a microscope to be needed to visualise them and identify them. Generally mange mites cause skin disease with mite lesions being intensely pruritic (itchy), some can produce an allergic reaction (e.g. Sarcoptes) and others induce susceptibility to secondary bacterial infection (e.g. Demodex). Mites are predominantly from the following species:

Otodectes - Ear Mites

These are commonly found in dogs and cats and occasionally in horses. The condition of Otitis externa in dogs and cats is often due to or initiated by ear mites. In early infection they may be seen with a microscope but later they may be indistinguishable due to excessive infl ammation and secondary infection. They can be treated with ear drops.

Cheyletiella

This surface living mite can infect the dog or cat where it causes pruritis and hair loss with dry scaling of the skin. It is also a common cause of alopecia (baldness) in the rabbit and guinea pig. The mite can temporarily infest man causing itchy papules where it bites.

Sarcoptic Mange

This disease is a zoonosis i.e. it can be transferred from animals to man. The sarcoptic mange mite burrows just under the surface of the skin and lives there, though it may also be found deep in scabby material exuded from the damaged skin. Dogs can be affected with lesions around the ears, elbows, hocks and sternum. It is very itchy and the dog may do serious damage to itself by rubbing and biting. There is often a strong mousey smell. In cats the mite involved is Notoedres cati and initially lesions are seen round the ears, spreading to face, neck, elbows and feet, again being extremely itchy.

Demodectic Mange

Demodex lives in hair follicles and sebaceous glands. In Britain Demodectic mange as a disease is usually only seen in dogs and small animals such as hamsters. Dogs are probably infected by their dams soon after birth. It is usually seen in puppies three to nine months old and may show either as a pustular infl amed skin or as a thickening and keratinisation with hair loss. The disease often starts on the head and fore limbs but may spread over the body.

Mange Control

This depends upon the host species and the mite species. Injectable preparations and spot-ons can be used for sarcoptic mange. Demodectic mange in dogs is very difficult to cure. As most treatments do not kill eggs they should be repeated at ten day intervals at least once unless residual chemicals are left within the animal or on the coat so that all mange are killed and the young are not left untreated to continue the infection and discomfort.

Fleas

Fleas are wingless insects with laterally compressed bodies. They have six legs well adapted for jumping. Their size varies with species but in general they are around 2mm long. Farm mammals are not infested by fleas but they can affect chickens and pigeons as well as cats, dog and man. Fleas can carry disease, e.g. bubonic plague of rats and man and myxomatosis of rabbits. In addition they can carry the tapeworm Dipylidium caninum that is of importance.

The flea is a very active parasite and may spend some time off the host. It can be quite difficult to find one even on a heavily infested animal as they move through hair very quickly. It is often their faeces that is the only sign of their presence. Eggs will fall off as they are not sticky. After 2-16 days the larvae hatch, looking like small highly active maggots. These larvae often live in crevices, under carpets or in the animal’s bedding. After a week or longer the larvae enters the pupal stage and hatches as a flea two weeks to several months later.

Heavy flea infestations of animals that are old or ill can cause an increasing loss in condition with some animals tolerating fleas showing little irritation at their presence. Others show varying degrees of hypersensitivity to flea saliva - resulting in itchy spots at the site of bites or even moist exudative dermatitis with secondary bacterial infection. A common reaction in cats is thinning of the coat from excessive grooming and miliary dermatitis may be associated with infestation.

Flea Control

1. Kill the adult flea on the host. Flea collars may be used but some animals are sensitive to them. There are sprays, injectables, washes, powders or “pour-ons”. Care should be taken when selecting a preparation suitable for cats.
2. Kill the developmental stages in the environment. This can be done by thorough vacuum cleaning and washing the animal’s bedding. There are insecticide/insect growth regulator (IGR) combinations available for household use.
3. The dosing of dogs and cats using the newer spot-on formulations which have both larvicidal and adulticidal properties has given significantly better control of flea infestations.

Lice

Lice are small wingless insects which can occur in large numbers on cattle, sheep, pigs, horses, companion animals and birds. There are several different species and two distinct types.

• Sucking Lice - have a pointed head with a piercing proboscis, and feed regularly on blood.
• Chewing Lice - have a broad head bearing strong chewing mouth parts and feed on epidermal scales, scurf and wool.

All lice attach their eggs to the hair or wool of the host animal and the first-stage nymph breaks out through a special cap at the apex. The life cycle is simple: there is no metamorphosis or changes but all lice pass through four ‘nymphal’ stages before reaching a stage of adult sexual maturity. The generation from egg to egg is brief - 14-21 days under optimum conditions. Heavily louse infested animals can show severe rubbing hair loss and skin thickening, scurfiness and their overall health is generally poor with them appearing to lose weight due to the time taken up relieving the irritation rather than eating. In heavy infestations, particularly of sucking lice the animal can become anaemic due to the amount of blood being taken by the lice from the host animal. Transmission is usually by direct contact i.e. animal to animal.

Lice Control

Good management and feeding provides the best protection against lice infestation. For dogs and cats the sprayon insecticides are often convenient though powders and washes are also available.

Ticks

Ticks are not insects but are arachnids and are therefore related to the spider. Ticks are found in upland areas often with bracken cover. In Britain the tick life cycle lasts three years with the adult attaching itself to a convenient bare or hairy area of the body.

The ticks then simply wait on vegetation for a convenient host to walk by. Their importance is in diseases they can carry, e. g. Lyme disease in man and dogs.

Tick Control

It is normal to tackle ticks when they are actually present on an animal and the key is to completely remove them to prevent infection. Alcohol and temperature are often used to remove them or a special tick remover.