INTERNAL AND EXTERNAL PARASITES OF THE DOG

Caring For Your Dog

INTERNAL PARASITES

Of all the subjects which cause anxiety to owners concerning their dog's health, worms can be placed at the top of the list. Over the years a great deal of superstition and mythology has built up regarding the supposed symptoms caused by worms and the weird and horrific folk remedies which were used to get rid of them. There is really no need for this excessive alarm. Firstly, worms do not cause a great number of conditions which are attributed to them and secondly, with modern drugs, they can be quite safely eliminated without causing any distress to the patient. All dogs, at some time in their lives, have worms. Usually this is during their puppyhood, and at this time the owner should treat routinely for worms, whether symptoms are obvious or not. A dog that appears quite healthy can be carrying worms, may pass or vomit a worm, and be shedding hundreds or thousands of worm eggs in their faeces. There has been a great deal of publicity in recent years regarding the risk of infection to children through contamination of parks and playgrounds by faeces from dogs infected with roundworms (see "Danger to Children" later in chapter). What is not generally realised is the fact that control of these worms by the regular dosing of dogs with roundworm medicines is cheap, effective and harmless to the pets. If all dogs were regularly treated, the risk to human health could be minimised. The worms found in dogs in Britain fall into two main categories; roundworms and tapeworms. They are not blood-sucking worms, but live on the partly digested food material in the stomach and intestine. Unless they are present in very large quantities they are unlikely to produce symptoms of illness, except in the case of young puppies. If you see definite signs of worms (see "What to look for") you should, both for the dog's sake and in the interest of hygiene, take measures to get rid of them. However, if your dog becomes ill, never assume that worms are the cause and commence treatment without consulting a Veterinary Surgeon.

ROUNDWORMS (TOXOCARA CANIS)

Roundworms, also called ascarids, are mainly of importance in young puppies and pregnant bitches. They only infrequently cause problems in dogs of two years and over. However, these animals still carry infections, and continue to shed worm eggs to reinfect other dogs, so they still need to be wormed. In appearance they are round-bodied, rather similar to a tiny earth worm. They can be up to nine inches in length but are usually much smaller, and are of whitish colour or pinkish brown due to ingested material. The life cycle of the roundworm is quite simple. They are spread directly from dog to dog. The eggs, which are microscopic in size and invisible to the naked eye, are passed in the faeces. They are ingested again by licking, and when swallowed develop in the intestines of the dog into larvae, or microscopic immature worms. These migrate through the blood stream to the lungs. They are then coughed up and swallowed again. These larvae grow to maturity in the intestines and begin producing eggs, so completing the life cycle. The adult worms are sometimes noticed at this time when they may be vomited or passed in the faeces. In young puppies, there is no natural immunity to worms, and this cycle readily completes without interference. Since puppies constantly reinfect themselves and each other, there is a need to repeat treatment on a two-weekly basis, as wormers have no residual effect. As the dog matures, it develops an immunity to the worms, and is able to put up a degree of self-defence. In the adult dog, this immune reaction causes the majority of developing larvae to become trapped in the dog's muscles as harmless cysts. As fewer worms make it all the way to the intestine, treatment is needed less frequently, and intervals of three months are generally recommended between treatments. However, if female dogs later become pregnant, the resulting drop in immunity, brought about by hormonal changes, allow trapped larvae to break out of their cysts and resume their travels around her body. At this time, some of the larvae will cross the placenta and enter the unborn puppies. Virtually all puppies are born with worms, and treatment of the bitch and litter is essential from two weeks of age onwards (see "Treatment"). Roundworms Symptoms of worm burdens can vary from quite serious to very mild. In young pups worms may cause abdominal distensions, pain, collic, loss of weight, vomiting or diarrhoea and even, on rare occasions, rupture of the bowel. At post-mortem examination, the stomach and intestines of these pups may be found to contain hundreds of worms. The migrating larvae in the lungs may also cause coughing, which can be an important symptom. These larvae may also travel through the liver, brain or other tissues.

Modern treatment for roundworms does not necessitate starving the dog, and usually causes no distress at all. The remedies are palatable and easy to administer, and generally are very effective. Puppies should be treated from two weeks of age, and the treatment repeated at fortnightly intervals up to three months of age. At each of these treatments, the bitch should also be treated. Remember that reinfection can easily occur. Thereafter, treat the pups every four weeks until twenty-four weeks of age. After this, they can be treated according to the recommended adult regime of once every three to four months. Treatment It is possible to administer worming treatments to pregnant bitches, but this should only be done of the in- under the supervision of a veterinary surgeon. whelp bitch Unfortunately, wormers do not exist, either from your pet shop or your Veterinary Surgeon, that What are able to kill the larvae trapped in the cysts in the body, so timing of treatment of the pregnant wormer to bitch is very important if ante-natal infection of the puppies is to be prevented. Only one type of use wormer, available only from your Veterinary Surgeon, is recommended for this use, and needs to be given to the bitch every day for a period of 25 days. Even this is not 100% effective. You may prefer to wait until your bitch has had her puppies, and then treat both her and the litter together. Adult dogs only need treatment every three months unless they become pregnant. There are many products available to treat roundworms. Unweaned puppies need only be treated for roundworm, but following weaning, tapeworms should also be considered. Read the label of each product before buying, to ensure it is recommended for use in your own pet. If in doubt, ask the pet shop owner or your Veterinary Surgeon for further advice. Danger to Although the roundworm is thought unable to complete its life cycle in humans, ingested eggs can children cause serious, though fortunately rare, conditions in children. They hatch into larvae in the gut and can then migrate to various organs of the body, including the liver, lungs, eyes, and brain, where they can become permanently encysted. It is therefore of the greatest importance to see that puppies which are in contact with children are kept free from worms, and that a good standard of hygiene is maintained. The dog's excreta should be cleared away as soon as possible from gardens or exercise runs to prevent the ground becoming heavily contaminated with worm eggs, which can lay dormant in the topsoil for several years. Likewise, dogs should be discouraged from fouling public places where children play. N.B. worm eggs found in fresh faeces are not infective, so there is no danger to you if you clear up after your dog straightaway.

TAPEWORMS (TAENIA AND DIPYLIDIUM SPECIES)

Tapeworms are most commonly found in the adult dog. It always has to be remembered that tapeworms have to have an intermediate host (i.e. spend a part of their life in another animal), and therefore successful treatment includes elimination of the intermediate host as well as removing the adult worms from the dog. Recognition This worm consists of a number of whitish coloured segments which are joined together to form the tape, terminating at the narrow end in a head which is attached by minute hooks to the lining of the intestines of the dog. They vary in length from a few cm, to 5 m, but it is more often the individual segments (containing the eggs) which are seen as they are shed in the faeces. These may appear as short strings of white segments, or white wriggling particles, looking like grains of rice, in the faeces (they are often mistakenly described by owners as roundworms), or attached to the hair in the tail region. How they Tapeworms are never transmitted directly from dog to dog, but always through an intermediate spread host. These may include mice, rabbits and lice, but the most common one for town dogs is the flea. The dog may swallow the flea containing the larva of the tapeworm while grooming, or may be infected while hunting rabbits, etc. or eating uncooked animal carcasses. The larva grows into a tapeworm and attaches itself to the intestine of the dog where it remains until it is mature and commences to shed segments containing the microscopic eggs. These eggs are then eaten by the intermediate host to repeat the cycle. What to look Except in the case of massive infestation, digestive symptoms do not occur. Tapeworms do not for? usually cause loss of weight, and fat dogs as well as thin ones may be heavily infested. The dog may show signs of anal irritation as a result of shedding segments but it should be noted that this is rarely the case. Most dogs showing irritation around their hind end are, in fact, not infected by worms but either have problems with their anal glands, or a heavy flea infestation. Control Treatment should be carried out both for the sake of the dog, and for aesthetic and hygienic of the reasons. If reinfestation is to be avoided, measures must be taken to get rid of the intermediate Intermediate host. In the case of fleas, this involves regular bathing or spraying with a suitable insecticide. For those dogs that are inveterate hunters and rely on other intermediate hosts to keep up their tapeworm infestation, the only answer is a regular dosing with tapeworm remedies. Cooking meat will destroy tapeworm cysts.

Tapeworms may sometimes prove rather difficult to eliminate as unless the head, or scolex, is destroyed, the worm will soon start to grow again, even though a considerable part of the tape has been shed. If segments start to appear immediately after dosing, it suggests that the treatment has not been fully effective and should be repeated, taking care to use a preparation that is designed specifically for tapeworm. If segments reappear after a few weeks, it is more likely that reinfestation has taken place, and you should ensure that you are also dealing with the intermediate host of the tapeworm at the same time as you repeat the treatment. Make sure that you select a product suitable for your own pet. Tapeworms are only very rarely transmitted to humans. However, infestation with humans Echinococcus, a less common species, can very occasionally occur, and may be serious.

HOOKWORMS (UNCINARIA)

These are much less commonly seen in Britain, but they are blood-sucking worms and can cause serious loss of condition. They are susceptible to treatment with some drugs, but if in any doubt, consult a Veterinary Surgeon.

WHIPWORMS (TRICHURIS)

This is a rather rare type of worm infestation which would be diagnosed by a Veterinary Surgeon, since they are unlikely to be observed by owners.

EXTERNAL PARASITES

Even under present day conditions, dogs are liable to become infected with the common ectoparasites, that is to say, the parasites which live in, or on the skin. You may feel that because your house is kept spotlessly clean this is unlikely to happen, but any dog which is taken out for exercise and socialises with other dogs can pick up fleas, lice or, less commonly, ticks, and suffer accordingly. Indeed, these parasites actually prefer to live in a clean coat. Make a point of giving your dog a thorough grooming several times a week and keep a careful watch for these parasites, especially in the summer months when they are most prevalent. The best form of prevention is to be prepared before a problem takes hold. Ideally, treat your house (carpets in all rooms to which your dog has access, soft furnishing and bedding) with a household flea product before the beginning of the "flea season" (i.e. April is ideal). These products give effective, long-lasting control for up to one year. Additionally, you may wish to bath your dog with an Insecticidal Shampoo occasionally, as a precautionary measure. Flea collars are also available and, used correctly, provide prolonged protection. Without suitable treatment, flea eggs and larvae can persist in carpets and upholstery for many weeks. Symptoms The first sign of parasitic infestation that you will notice is persistent scratching and loss of hair. If you fail to take action on this, you may then be confronted with open sores, where the dog has bitten or scratched itself raw as a result of intense irritation. Trans-mission It seems that some dogs, like some people, are much more attractive to these insects and you may find that where two dogs are kept together, one will be constantly attacked by fleas or lice while the other remains apparantly flea-free. Fortunately, there is little risk of transmission to humans. Dog lice never attack people, dog fleas will will only occasionally bite people, and ticks very infrequently attach themselves to people, usually in moorland or heathland districts. None of these parasites will breed on people.

THE FLEA

By far the most common flea found on dogs, is the cat flea (Ctenocephalides tells). The dog flea (C. Canis) is much more rare. Very occasionally, hedgehog fleas are also found on dogs. Even rarer still are human fleas, rabbit fleas, and bird fleas. Fleas are most common in summer and autumn, when it is warm enough for their life cycle to be completed in a short time. However, with the advent of central heating, household infestations can occur even in winter months. The adult flea spends all its life on the dog, where it feeds, breeds, and lays eggs. The eggs are extremely smooth and non-sticky so that they fall out of the pet's coat easily and drop onto carpets or bedding. After a few days, they hatch into tiny larvae which feed on dust, debris, and adult flea faeces until they are big enough to form a pupa. The pupa disguises itself with particles of dust and fluff which are stuck to its outer casing. In the pupal stage, the flea life cycle can remain dormant for up to twelve months just waiting for an increase in temperature or the vibration made by a pet walking close by. Once the pupa hatches, a young juvenile flea is released and begins its search for a host to live on to continue the life cycle. At the height of summer, this life cycle from egg to flea may take as little as three weeks. Recognition Fleas are blackish-brown, shiny and roughly one-sixteenth of an inch in size. They tend to run very rapidly through the coat rather than jumping, and can be quite difficult to detect. They may sometimes be found in clusters on the abdomen, or at the base of the tail. They are blood-sucking insects, and their characteristic black, ash-like excreta can often very readily be seen on the dog's coat or on the bedding. Symptoms The dog will start to scratch and there may be loss of hair. Later, bare places will develop and there may be open sores, especially at the base of the tail.

Treatment by the use of any a flea product is usually very effective. Blankets should be washed if possible and all boxes or baskets disinfected or sprayed with an insecticide, as should any other place where the dog spends time lying. To prevent reinfection,Flea Collars are an easy option. These are thin collars Treatment impregnated with insecticide which is slowly released over time, and gives continuous protection for up to four months. Flea life cycle Hedgehogs If at any time your dog finds a hedgehog in the garden, he may come in with his ears or face covered with tiny black insects. These are hedgehog fleas, and while they may cause mild discomfort for a very short time, they do not live on dogs. Treatment, using a flea powder or spray, is very quickly effective, but be very careful to avoid eyes, nostrils, mouth, and inner ears.

THE COMMON DOG LOUSE

Lice are only rarely found on dogs. The dog louse (also called Trichodectes Canis) is tiny, pinkish-white in colour, and rather spherical in shape. They are quite slow-moving and attach themselves to the dog's skin, where they feed. They may be found all over the body, but more especially in the hair of the ears, particularly of the long-eared breeds. The eggs, or nits as they are called, have very much the appearance of scurf. However, if they are examined under a magnifying glass it will be seen that they are oval and shiny, and that each one is firmly attached to an individual hair. Lice can also be intermediate hosts for the Dipylidium tapeworm.

Persistent scratching, loss of hair and sore places, especially on the flaps of the ears. In very young pups severe pediculosis or infestation with lice can, on very rare occasions, lead to anaemia and even death. Consult your Veterinary Surgeon for a product suitable against lice.

TICKS

Ticks (Ixodes and other species) are bluish-brown and bean-like in appearance. Their size varies, but they may be up to half an inch in diameter when engorged with blood. At this stage they are sometimes mistaken for a skin cyst. Examination under a magnifying glass will show the presence of legs and a biting mouthpiece, by which the tick is attached to the dog. Ticks are found mainly on moors and heathland, and in country districts where they are normally parasitic on sheep. They will attach themselves to a dog, or very rarely to a person, if the opportunity occurs. Ticks are also found on hedgehogs, and this is sometimes the source of infestation in town dogs.

A freeze spray is an easy-to-use spray for simple removal of ticks. The spray freezes the tick, causing it to lose its grip, when it can more easily be removed with tweezers. Ticks will usually drop off on their own after a few days, having taken their blood meal. However, they may have transmitted microscopic parasites into your dog's blood stream by then, so it is better to remove them as soon as possible.

HARVEST MITES (Trombicula autumnalis)

These are harvest bugs which cause considerable annoyance to humans as well as dogs in the countryside during the late summer. They are actually a kind of mite, and in dogs they are found most frequently in the skin between the toes or up the length of the leg. They are just visible to the naked eye, and groups of them have a red or yellowish appearance. Consult your Veterinary Surgeon for a product suitable against harvest mites.

CHEYLETIELLA YASGURI

This is another form of microscopic mite, and is often difficult to recognise. There is irritation and usually a very thick white scurf forms, mainly along the back of the infected animal. If the scurf is examined accurately it may be seen to move (the infection is sometimes known as "walking dandruff").

is very similar to that of Sarcoptic Mange (see later) and it is usually best to consult your Veterinary Surgeon if you believe your dog has this condition. This mite may also cause a rash on humans, particularly young children.

THE EAR MITE

This mite (Otodectes cynotis) is of considerable importance to the dog owner, as it lives only in the ear canal of dogs (and cats), where it causes great irritation. The dog reacts to this by shaking the head and scratching, causing exudation, and sometimes haemorrhage and thus pre-disposing to many of the intractable and chronic ear conditions which are seen. Cats, while they are very susceptible to ear mites, appear to be less sensitive to them. The condition in cats, and especially young kittens, is sometimes not suspected until a dog living in the house picks up the infection, and immediately shows his discomfort. Ear mites are just visible to the naked eye as pin point greyish dots, and they are easily visible under a magnifying glass. The main symptom is persistent shaking or scratching of the ears. On examination, the ears are often found to be full of dry, dark brown wax. If the diagnosis is certain, relief can quickly be obtained by the application of ear drops designed to destroy mites. This should be repeated at weekly intervals to catch the new mites as they emerge from the eggs. If the condition has persisted for some time, secondary bacterial infection is almost certain to have taken place, and veterinary advice should be sought. A sudden onset of violent head shaking, especially after a walk through long grass, may indicate the presence of a grass seed in the ear, rather than an ear mite infection, and in this case also veterinary help will be needed. There are three other important external parasites which can affect the dog. These are not visible to the naked eye, and they can only be definitely diagnosed by microscopic examination of a scraping of skin from the affected animal. There are two types of mange, and ringworm, and they are of special interest because, in the case of two of them, there is considerable risk of transmission to man, particularly where dogs are allowed to sleep on chairs or beds.

SARCOPTIC MANGE

This is the most common type of mange, and it is caused by the mite Scarcoptes scabiei. This mite burrows into the superficial layers of the dog's skin, where it lives and lays its eggs, causing intense irritation to its host. It is most common in puppies and young dogs, and it may become a serious problem in kennels if proper hygienic measures are not taken to control it. Recognition In the early stages, sarcoptic mange is characterised by persistent scratching, followed, as a result of this, by the appearance of reddish patches of inflammation of the axilla (arm pits) and on the inside of the thighs. There are often bare places around the eyes and scaly thickening of the ear flaps. The condition, if not checked, may spread all over the body of the dog with the formation of scabs, sores, and bare places throughout the coat. There may be a general loss of condition as a result of the constant irritation. Diagnosis may be confirmed by a Veterinary Surgeon, who will examine a skin scraping taken from one of the affected places under a microscope. Trans- sarcoptic mange is readily transmissible both to other dogs and to people, when it is known as mission scabies. Children are especially susceptible, probably because of their more delicate skin, and the fact that they are more likely to come in close contact with their pets while playing. In humans, the first signs of infection are usually red irritant patches, or streaks on the fingers or wrists. If you have any reason to suspect infection, consult your doctor as soon as possible.

Advice on a suitable course of treatment should be sought from your Veterinary Surgeon. The dog should not be allowed to come into contact with other animals. The bedding should be boiled each week and the basket or box, as well as all collars and harnesses, thoroughly scrubbed with disinfectant. Any swabs or cotton wool used for applying skin dressing should be disposed of by burning, if possible. The owner should remember the importance of washing the hands each time after handling or dressing the dog. Finally, remember that because mange mites live in the layers of the skin, it is hard to be certain when they have been totally eliminated. It is necessary, therefore, to persevere with treatment and hygienic measures for some time after the external symptoms have disappeared, or you may be disappointed by a recurrence of the problem.

DEMODECTIC OR FOLLICULAR MANGE

This type of mange is caused by Demodex canis, a rather cigar-shaped mite recognisable only under a microscope. This mite lives in the hair follicles, coming to the skin surface only intermittently in its life cycle. It will be understood, therefore, that it is a much more difficult condition to treat effectively. Recognition Initially, the appearance of dry scaly places in the dog's coat may be seen (typically between the toes and around the eyes). Short-coated varieties, and in particular Dachshunds and Dobermans, seem to be most often affected and the dog may have a rather characteristic "musty" or "mousy" odour. The bare places may remain quiescent for some time but usually, as a result of scratching, bacterial infection follows, often with the presence of very resistant staphylococci and formation of small discharging pustules or abscesses. The dog's skin tends to become thickened and wrinkled, especially on the limbs, and, if the condition is not checked, it may lead to a severe illness, or even death, as a result of a generalised bacterial infection or septicaemia. Diagnosis Diagnosis may be confirmed, as with sarcoptic mange, by a skin scraping, but it is sometimes less easy to demonstrate the presence of mites, because of their tendency to invade the deeper tissues of the dog's skin. Trans- Demodectic mange is not transmissible to humans, and not readily transmissible between adult mission dogs. Transmission is thought to take place only from mother to pups in the very early stage of life. The pups may show signs of infection at once, but sometimes the mites may remain dormant in the tissues without giving any visible signs of their presence. This explains the sudden appearance of the lesions of demodectic mange in a dog which has obviously not been in contact with a case. It is wiser not to breed from bitches which have had demodectic mange.

Treatment is always best carried out by your Veterinary Surgeon. Demodectic mange is extremely resistant and difficult to treat, but, with the use of modem antibiotics and other drugs, it is usually possible to produce a great improvement, if not always a complete cure.

RINGWORM

The extremely contagious skin condition known as ringworm is actually caused by a fungus (the most common type affecting the dog is called Microsporum canis) which invades the individual hairs, causing them to break or to die and fall out. The lesions caused by ringworm are rather variable and it is, for this reason, difficult to diagnose with certainty or to distinguish from other skin conditions. Typical ringworm is seen as circular lesions, usually rather pink and inflamed, with raised crusty edges. However, there may be simply irregular, smooth, bare places anywhere on the dog's coat. Irritation may sometimes, but not always, be present. The hairs at the edges of the bare places tend to be stubby and broken, and pull out easily. It cannot be too strongly stressed that ringworm is extremely contagious, not only to other animals, but to humans and especially children. Medical advice should be sought at once if there is any suspicion that anyone in the family may be affected. The condition in dogs may be caught from calves, mice and rats, and also sometimes from other dogs and cats (or from humans). In the case of infection from mice or rats, the bare places may appear first on the muzzle. Dogs in the country may be infected from contact with gates or fences, where calves have been scratching. The spores of ringworm can remain alive on woodwork, furniture, or upholstery for several years.

Diagnosis should be carried out by a Veterinary Surgeon. He may examine the dog under a Wood's lamp (an ultra violet light which causes the ringworm to glow, or fluoresce, in the dark) or examine a skin scraping taken from the dog under a microscope. Occasionally, it may be necessary to culture or grow the fungus in the laboratory to confirm the diagnosis.

If you suspect ringworm, always consult your Veterinary Surgeon. Never attempt treatment on your own. Modern methods of treatment, including a very effective oral drug (a tablet) now make the condition much easier to control. However, remember that it is important that you persevere in carrying out the measures that your Veterinary Surgeon advises. The disappearance of the symptoms does not necessarily mean that you have got rid of the ringworm. Great care should be taken over disinfection, and beddings, baskets, and collars are better burned. A failure to observe these precautions may lead to a flare-up of infection, even after many months.

Blendbetter Carlisle. Blendbetter Pet Foods, Westlinton, Carlisle. CA6 6AA. 01228 791608
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