Internal Parasites

All animals harbor internal parasites. Some of these parasites, such as the intestinal flora, are beneficial. Others, such as the protozoa and worms, can cause severe damage and even death, if left unchecked. Dogs come in for a share of these internal parasites. Of the two major types of internal parasites infest­ing dogs—worms and protozoa—worms are by far the most common and troublesome.

Every dog owner should know something about the life cycles of the various worms and protozoa and how these para­sites enter the dog's body. While there are treatments and drugs to expel these parasites, your dog can become reinfested at any time. Only by breaking up or destroying the life cycles of these parasites can reinfestation be prevented. Prevention, then, is your best weapon against internal parasites.

WORMS

Worms can be very damaging to your dog's health. They are particularly dangerous to young puppies. Worms sap the dog's strength, make him irritable, and open the door for more serious conditions by lowering his resistance.

Ascarids

The most important ascarid infesting dogs is the large ascarid (erroneously called roundworm), Toxocara canis.

This worm measures from 1 to 7 inches and is found in the small intestine and very frequently in the stomach. It is widely distributed throughout the United States and in some sec­tions of the country presents a serious threat to the health of dogs.

Ascarids are passed from infected dogs into the feces as unsegmented eggs. Other dogs pick up the eggs by coming into contact with the feces containing the eggs. The eggs enter the dog's body by way of the mouth. When the eggs reach the dog's small intestine, they penetrate the intestinal wall and move into the bloodstream. Next, they are carried to the lungs, where they go into the air passages and migrate up to the trachea and into the esophagus. From the esophagus, they are swallowed and move down again to the intestines where they mature into worms. This migration from small intestine and back again takes 10 days. The entire life cycle, from egg to mature worm, is completed in 75 to 90 days.

Young dogs and puppies are the most frequent victims of ascarids. Many ascarids in young puppies are the result of prenatal infestation of the mother. Intra-uterine infestation by T. canis is common. Even though older dogs can become infested with ascarids, such infestations are usually light and rarely cause any serious damage. But the situation is very different in puppies; ascarid infestations can be devastating and lethal.

In most cases where pups have become infected with ascarids in the uterus, the larvae localize in the liver of the newborn pup. Some of the ascarid larvae may move to the lungs. Within 24 hours after the puppies are born, the imma­ture ascarids begin to move along their way to the intestines where they will mature. Eggs of ascarids may appear in the feces of puppies 21 to 24 days after birth.

As the pup grows older, his susceptibility to ascarids les­sens. Females are more immune to ascarids than males. They arrive at this immunity at a much earlier age, too. Females reach immunity at six months and males at 36 months. How­ever, this immunity is not absolute and older males and females can have infestations.

The most noticeable symptoms of ascarid infestation in puppies are a distended abdomen, poor hair, diarrhea and a "sweetish" breath odor. Vomiting often occurs and mature ascarids are seen in the vomit. Since the ascarid larvae migrate to the lungs, pneumonia is always a danger and frequently accounts for the sudden death of infected pups. Once the ascarids mature in the pup's intestines, they can cause various complications ranging from persistent diarrhea to complete blockage of the intestinal tract.

Although the larvae of T. canis do not ordinarily mature in the human intestinal tract, children are sometimes infested with these ascarids. Immature T. canis larvae have been found to cause a disease of children known as visceral larval migrans. Somehow or other, children manage to ingest the T. canis ova and become infected. The ascarid larvae are also sus­pected of causing other diseases and allergic reactions in human beings. Research is now being conducted to deter­mine the extent of human infestations by canine ascarids.

Since ascarids are passed to puppies while still in the uterus, most dog breeders worm the pups shortly after birth. But the age at which puppies are wormed for ascarids is very important. If it's too early, very few ascarids will be expelled. Remember that infectious larvae can still be migrating from the lungs. These would not be affected by worm medicine. At 4 weeks of age, most of the inherited ascarids will be in the intestinal tract and can be expelled. The job may take more than one worming, though, and you should be prepared to do follow-up wormings.

If your dog is infested with ascarids, the veterinarian may prescribe a series of wormings at 2-week intervals. This series may continue until your pup is 3 months old, after which the worming may be reduced to a once-a-month basis until the pup is mature. If you have a female, treatment for ascarids can be stopped when she reaches 7 to 8 months of age. If a male, he will have to be wormed at intervals until he is 2 or 3 years old. Such prolonged treatment is not intended to "pad the bill." It is the most practical course to follow for the total elimination of ascarids until the dog has the natural immun­ity of age.

Fortunately, the process of removing ascarids is a simple one. There are a number of worm compounds or vermicides that are safe and effective. The main problem in treating for ascarids is not which compound to use, but when to use it for the best results. Remember that your pup can become reinfected with ascarids at any time. Sanitation then becomes an extremely important measure in eradicating infectious ova. You should concentrate on destroying the life cycle. Treating the soil with chemicals is of little value, since T. canis ova are resistant to chemicals ordinarily used for this purpose. But the ova are highly susceptible to drying or direct sunlight. So, if your dog lives in a doghouse and kennel, expose the house to sunlight and fresh air.

As we outlined in the chapter on the new puppy, the best procedure to follow if you suspect worms is to take a speci­men of his bowel movement to the veterinarian. The veteri­narian will take it from there. But if you decide to worm the pup yourself, do so with care. There are a number of ver­micides on the market that will expel T. canis. Follow the directions explicitly. Vermicides are given on the basis of the dog's weight. Don't guess at his weight, weigh him. Use a bathroom scale and first weigh yourself. Next, hold the dog and step on the scale. Subtract your weight from the new reading and the result will be the weight of the dog. If you have a large dog, such as a Great Dane, you will have to find a platform scale. Coalyards, lumberyards and other concerns dealing with heavy materials usually have platform scales. Perhaps the owner or manager will let you weigh the dog.

Hookworms

Hookworms derive their names from the toothlike struc­tures in the cheeks or mouth cavities. With these hooklìke structures, the hookworms fasten onto the dog's intestinal walls where they feed on blood.

Several species of hookworm infest dogs, but the most common is Ancylostoma caninum, found throughout the southern United States. A "northern" hookworm, Uncinaria stenocephela, while infesting dogs, is not as significant as A. caninum. On the small side, A. caninum measures 8 to -w of an inch in length when straightened out. Hundreds of these hookworms may be found in a single dog. And all of them will be firmly hooked onto the intestinal walls.

The female hookworm is capable of producing thousands of eggs each day. Hookworm eggs are passed in the feces, but usually they will not start to develop until certain optimum conditions exist. These optimum conditions include plenty of oxygen, moisture and warmth. The eggs thrive in sandy soil and a damp, shady spot. Exposure to direct sunlight, wind or freezing temperatures will kill the eggs.

When the hookworm eggs get the optimum conditions, they develop into infectious larvae within 5 days. After being ingested by the dog, the larvae mature into hookworms in the alimentary tract. Dogs can be infected through the skin and this is a very common mode of entry for hookworms. Prenatal infection is also common with hookworms.

Upon entering the dog's bloodstream, the larvae move to the lungs where they soon find their way to the trachea. From the trachea, the larvae are coughed up and swallowed, thus gaining entrance to the intestinal tract. The larvae mature in the small intestine and very often in the cecum. The migratory phase, from bloodstream to trachea to the small intestine or cecum, takes approximately 3 days. The complete life cycle, from egg to mature hookworm, requires 21 days.

As with ascarids, young dogs and puppies are the most frequent victims. Many puppies born with hookworm larvae have very little chance of survival. The early symptoms of hookworm infestation include anemia (pale gums, eyelids, etc.), listlessness, bloody bowel movements, and loss of weight. In the later stages of hookworm infestation, many distemper-like symptoms appear: nasal and eye discharge, coughing, temperature above 103°F., and others.

The treatment or elimination of hookworms can be long and drawn out. Furthermore, the outlook is often discourag­ing. Many pups with hookworm infestation suffer from mal­nutrition and are in a very weakened state. An overdose of worm medicine can be fatal. The problem becomes one of having to build up the puppy and eliminate the hookworms. In many cases, the pup has to be built up before worming can be attempted. There are specific worm medicines for hookworms, but many of them are toxic in the wrong dosages. Your safest procedure would be to have the veterinarian handle the hookworm problem. If the pup is run-down, the veterinarian can prescribe a special diet to bring the dog back to health, as well as the correct type and dosage of vermicide.

You will have to practice rigid sanitation to prevent any reinfestation of hookworms. Keep the kennel run and dog­house clean. Sodium borate will help to kill hookworm eggs and larvae. It is toxic to dogs and cannot be left where the dog can eat it. Work it into the soil; do not scatter it on the surface. Feed the dog a diet high in protein; this will help give him resistance to strength-sapping hookworms.

Whipworms

Whipworms are small whip-shaped worms that infest the colon and cecum. The whip-like part of the worm's body— the long esophageal section—makes up three-quarters of the overall body length, which is roughly 3 inches. Whipworms are widely distributed throughout the United States. Only one species is known to infest dogs, Trichuria vulpis. Whipworms are often difficult to eradicate, since they bind or sew themselves into the lining of the colon or cecum.

The eggs of the whipworm are passed in the feces of an infected dog and begin to divide within 24 hours. This divi­sion or fission is the first stage in the development of the larvae. No further change takes place until the eggs are in­gested by the dog. Once inside the dog, the whipworm larvae work their way to the colon or cecum where they mature.

The complete life cycle of the whipworm takes from 90 to 100 days. Since the life cycle is a long one, puppies under 3 months of age do not have mature whipworms. While whip-worms are often found in the colon, they prefer the cecum. Inflammation of the colon and cecum, accompanied by pain and tenderness in those regions, loss of weight, and diarrhea are symptoms of whipworm infestation.

Heavy infestations of whipworms are usually found in dogs that are over two years old. Whipworms, of course, lower the dog's resistance to other disease. Dual infestations—hook­worms and whipworms—are not uncommon and have been found in old, but otherwise well-cared for dogs.

Not too long ago, surgery was the only way to get whip­worms out of the dog's colon and cecum. But now several whipworm compounds have been developed that are effec­tive in eradicating whipworms. One of these compounds, Whipcide, manufactured by the Pittman Moore Company, Indianapolis, Indiana, has shown great promise in the elim­ination of whipworms. Inasmuch as whipworms are difficult to eradicate, the job is best left to the veterinarian. You can help break up the whipworm life cycle by practicing rigid sanitation in the dog's house and kennel run.

Tapeworms

Two species of tapeworms infest dogs. These are Dipylidium caninum and Taenia pisiformis. Both species are similiar in that they have a head, neck and numerous body segments. There is a wide variation in the size of tapeworms but the ones infesting dogs usually measure from 1 to 2 feet in length. D. caninum and T. pisiformis are widely distrib­uted throughout the United States.

Fleas and lice are carriers of tapeworm eggs. Your dog can ingest tapeworm eggs when he bites and swallows fleas or lice. Tapeworm eggs are also found in fish, reptiles or small mam­mals that are secondary hosts for these parasites. After gain­ing entry into the dog's intestinal system, the tapeworm eggs mature in 3 to 4 weeks. At maturity, the segments of the tapeworm below the neck get larger and wider, with the last few segments longer than the rest. These rear-end segments contain the eggs. The eggs pass out of the intestinal tract with or without a bowel movement. If they are not passed out in a bowel movement, the eggs work out of the anus and adhere to the hair around the dog's anus. Here they dry up until they resemble small brown-rice kernels. This is another method by which the tapeworm eggs are spread. Dogs always sniff each other's rear ends and it is more than likely that tapeworm eggs can be passed this way.

Tapeworms feed on the dog's intestinal walls. But the damage they cause is nowhere near as much as that done by hookworms or ascarids. The most common symptom of tape­worms is an irritation of the anus. This causes the dog to drag or slide his rear end over the ground or floor. But, since this is also a symptom of anal gland trouble, a positive diag­nosis of tapeworms should be made only when actual seg­ments with eggs are seen. Or by an examination of the bowel movement under a microscope. Occasionally, dogs infested with tapeworms will show signs of being nervous or "jumpy." Most of the time, the tapeworms will cause a chronic enteritis. Now and then, they will block the intestinal tract. T. pisi­formis is the tapeworm most apt to cause a blockage.

Tapeworms are easy to expel. Various tapeworm com­pounds are on the market. When using any of these patent worm medicines, do so with caution. There is always the danger of overdosing the dog. The prevention of tapeworm infestation is largely a matter of sanitation. Keep your dog free of fleas, lice and ticks. (See Chapter 15) Also, eliminate rodents that may be secondary hosts for tapeworms. If you give the dog fish, see that it is well cooked.

Heartworms

The dog heartworm, Dirofilaria immitis, is more prevalent than originally suspected. Infesting the dog, cat, fox and wild­cat, the heartworm was discovered in 1856 by Dr. Joseph Leidy. At first thought to be a tropical parasite, canine heart-worms have been located in dogs in more than thirty states. The heaviest infestations of heartworm are in dogs that live in the Gulf States and the Eastern Seaboard to as far north as southern Maine.

More cases of heartworm are found among the working and hunting dogs than in house dogs. This is readily under­stood when we consider the fact that the mosquito and flea are carriers of the heartworm eggs. The mosquito is respon­sible for spreading the parasite more quickly than the flea. And since the Gulf and Seaboard states are plagued with mosquitoes, the incidence of heartworm infestation is highest in these areas. The heartworm is comparatively unknown in the dry inland states that have little or no mosquito problem.

The adult heartworms locate in the right ventricle of the heart and in the pulmonary artery. But they may also appear in other areas. Heartworms are round, slender and longish worms, measuring from 5 to 14 inches. They have a diameter of less than 1/8of an inch. The female heartworm is oviviparous; that is, she produces eggs that are hatched within her body. When the eggs are hatched, they produce numerous living microfilariae that swim in the bloodstream of the infected dog. These microfilariae are removed from the bloodstream by sucking intermediate hosts, such as the flea and mosquito. In the flea and mosquito, the microfilariae develop into infective larvae.

After undergoing several changes inside the mosquito or flea, the microfilariae are ready for the true host, the dog, cat, fox or wildcat. They are transferred to the dog or other susceptible animal by the bite of the flea or mosquito as it feeds. Once inside the dog's bloodstream, the microfilariae develop into mature heartworms in approximately 8 months.

The symptoms of heartworm infestation are varied. In hunting dogs, the first noticeable symptom is that the dog tires very quickly. He may also gasp, cough, breathe with great difficulty and go into a fit or convulsion. There may be abdominal dropsy or a swelling of the lower chest region. Pustular lesions between the toes and on the dog's head are occasionally seen as a result of an allergy to dead or living heartworms. Many dogs infested with heartworms become depressed and are usually nervous, starting a fight with other dogs at the slightest pretense. Dogs with heartworms will also seek out dark or shady corners of the kennel or house. They show a marked aversion to light. This tendency to seek dark corners and aversion to light are also symptoms of rabies and distemper.

A positive diagnosis of heartworms will have to be made by the veterinarian. The treatment is also his job. Prevention is your problem. The destruction of the primary hosts—the flea and mosquito—should be your main objective. If you live in a heavily infested mosquito region, screen the dog's kennel. Keep him well covered with insect powder and give him a weekly dip in an approved insecticide. Cut down any weeds, brush or other foliage that might act as a resting place for mosquitoes. While the dog will need shade in summer, trees can be the resting places for heartworm-carrying mos­quitoes. Provide shade in the form of awnings. The soil and wooden parts of the doghouse and kennel can be treated with spray containing lindane, chlordane or methoxychlor. Also, you can mix a pound of 25% lindane or chlordane with sand and work it into the soil. Concrete or asphalt runs will, of course, offer the most protection against parasites. If you live in the heartworm region and have a hunting dog, you will be wise to have him blood-tested for heartworm micro-filariae several times a year.

Esophageal worms

These parasites are found in the dog's esophagus. The esophageal worm requires an intermediate host to complete its life cycle. The intermediate host is the dung beetle. Dogs pick up the parasite by eating dung or manure containing the infected beetle.

Esophageal worms cause lumps in the esophagus, vomiting and extreme difficulty in swallowing. Remember, however, that difficulty in swallowing is also a symptom of rabies or an obstruction in the throat. The lumps caused by esophageal worms may exert pressure on the windpipe, which, in turn, brings about coughing, labored breathing and—in extreme cases—suffocation.

Esophageal worms require veterinary attention. Help pre­vent your dog from becoming infected by restricting him to a kennel, except when taken out for walks. Keep him away from dung or manure piles.

Other worms

While not as common as the ascarids, hookworms, etc., the lungworm, kidneyworm and eyeworm are found in dogs. The diagnosis and treatment require veterinary knowledge.

Flukes(Trematodes)

Flukes or trematodes infest the dog's small intestine. They are dangerous parasites because they may be carriers of a rickettsialike organism that causes a condition known as "salmon or fish poisoning." Flukes are small, flattish para­sites. They require two intermediate hosts: the snail and fish. Dogs fed raw fish, especially salmon or trout, may ingest the fluke and the disease organism. So far, "salmon or fish poisoning" is localized in northern California, Oregon, Washington, and southwestern Canada.

The symptoms of "salmon or fish poisoning" include a discharge from the eyes and nose; bloody diarrhea; swollen face and sunken eyes; no appetite; increased thirst; sub­normal temperature—below 101°F; and prostration. The condition is extremely serious and requires immediate veter­inary attention. Do not feed your dog raw fish; if you feed fish, bone and boil it.

INTESTINAL PROTOZOA

Next to worms, the intestinal protozoa are the most troublesome of parasites. The common protozoa infecting dogs are the coccidia. There are four species of coccidia capable of infecting dogs and other animals, including poul­try. Usually, however, each of the four species prefers its own specific host, such as the dog, cow, or chicken. But it is possible for a dog to become infected with the poultry-type coccidia if he eats raw chicken viscera that are infected.

Coccidia fasten onto the cells that line the small intestine and the tissue under the intestinal lining. They reproduce and develop into what are know as oöcysts. These oöcysts are oval-shaped cells with a membrane and one or two gran­ular bodies floating within the cell. Oöcysts are highly infec­tive. They are eliminated from the dog's intestinal tract with the feces. Your dog can become infected, therefore, by com­ing into contact with the infected feces of other dogs. It is also possible—if your dog has coccidia—for him to reinfect himself by eating his feces that contain oöcysts.

Coccidiosis has distemper-like symptoms: nasal and eye discharge; soft bowel movement (changing to a watery or bloody diarrhea); weakness, emaciation and a rise in tempera­ture. There is also a progressive weight loss. Puppies are very susceptible to coccidia. Very often they become infected as early as 3 to 4 weeks of age. If left untreated, puppies deteriorate very rapidly, ending with convulsions and death.

A positive diagnosis of coccidiosis is easily made by a microscopic examination of the feces for oöcysts. Both the diagnosis and treatment should be left to the veterinarian. You can take preventive measures that include keeping the dog's sleeping and living quarters clean. Keep out strange dogs and avoid an accumulation of feces in the yard or kennel.

Other protozoa

For many years, it was believed that the coccidia were the main protozoa affecting dogs. Now we know that others are responsible for intestinal troubles. Among these are organ­isms belonging to the Entamoeba, Giardia and Trichomona groups. The symptoms caused by these organisms are similar to those of coccidiosis. Diagnosis and treatment are jobs for the veterinarian.

INTERNAL PARASITE CONTROL

It may not be possible for you to achieve 100% control or elimination of internal parasites. The best you can hope for is to minimize or reduce the dog's chances of infection. This you do by trying to prevent your dog from coming into contact with infected matter, and by breaking up the life cycle of internal parasites.

Veterinary parasitologists are constantly working on meth­ods to eradicate and break up the life cycles of parasites. Re­cently, a medicated dog food containing a vermicide for ascarids was developed and placed on the market. This medi­cated dog food is in the form of a meal and is manufactured by Best Foods Division, Corn Products Company, New York. It is dispensed only through veterinarians.

In the initial tests with this medicated dog food, 7-week-old puppies were put on a diet of the food. A second group of puppies the same age was fed a regular dog food. After six weeks of continuous feeding, the two groups were compared as to eradication of ascarids and general health. The results showed that the pups on the medicated dog food had a marked decrease in ascarid infestations and were in better health than the other group. The medicated dog food definitely proved effective in controlling ascarids. Studies were also done on mature dogs infected with Toxocara canis. At the completion of a three-week trial, those older dogs fed the medicated food were almost free of ascarids.

You will recall that the main problem in eliminating as­carids is that they migrate in the dog's body. The principle of the medicated food is that the daily feeding will eliminate ascarids as they appear in the intestines. The theory is a sound one, since ascarids do migrate. However, the possibility of ascarids developing resistance—or mutations—to the medi­cated dog meal must be taken into consideration. This has happened in the case of antibiotics and bacteria. Certain bac­teria, notably Staphylococcus aureus, developed resistance to most antibiotics. The same is true for certain insects. During World War II and shortly thereafter, DDT was the wonder insecticide. It was used to control all kinds of insects, from gnats to ticks. Eventually, the insects developed mutations that were resistant to DDT. Consequently, other insecticides had to be developed.

KENNEL SANITATION

Until these new methods of eradicating and preventing in­ternal parasite infection have been proven by the test of time, you will have to stick to old-fashioned sanitation.

Thoroughly clean the doghouse and kennel at least twice a month. Choose a good detergent and disinfectant. Com­pounds containing both a detergent and disinfectant are available. Pick one that is nontoxic and with a high degree of efficiency against the major organisms. The compound should be soluble in water. Follow the directions on the label —don't guess at the amounts to be used. Also, allow enough time for the compound to work; germs are not killed in a minute.

I£ possible, hose down the doghouse and kennel before using the detergent and disinfectant compound. This will wash away any feces or solid matter. Next, scrub all walls, floors and wooden bases with the compound. Work it into the cracks and corners. Take out any movable fixtures and wash them. Let the solution remain for about a half hour. After­wards, you can rinse off any excess compound. Follow up the housecleaning by spraying with an insecticide containing lindane, chlordane, pyrethrum or rotenone. Dirt kennels can be sprinkled with lime which is then worked into the soil. Con­crete or asphalt runs can be flushed, treated with the deter­gent and disinfectant compound, then rinsed.

To sum up the situation on internal parasites and their control: in most cases the diagnosis and treatment should be left to the veterinarian; prevention is largely your responsi­bility. Practice rigid sanitation in the doghouse and kennel. A periodic examination of the dog's bowel movement for in­ternal parasites is good management and good sense. It will prevent serious complications and it will enable you to keep the dog in top condition.

If you have a hunting dog and work him in mosquito-in­fested country, have a blood test for heartworm filariae done every three or four months. Finally, if you decide to do your own worming for ascarids and tapeworms, adhere to the in­structions on the label. A puppy can be seriously harmed, possibly killed, by an overdose of worm medicine. Remem­ber, worm medicines are poisons, that's why the worms are killed. If in doubt, better let the veterinarian

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