Hookworms are parasites which get their name from the hook-like mouth they attach to the intestinal wall with. The are only 3 mm long (about 1/ 8 inch) and minimal in diameter so are hard to see with the naked eye, but easily seen under a microscope. 

Despite their small size, they suck large amounts of blood from the tiny vessels in the intestinal wall. A large number of hookworms can cause anemia. This problem is most common in puppies, but it will occasionally occur in adult dogs.

How did my dog get hookworms?

Dogs may become infected with hookworms by four routes: 1. orally, 2. through the skin, 3. through the mother's placenta before birth, and 4. through the mother's milk. A dog may become infected when it swallows hookworm larvae (immature worm). The larvae may also penetrate the skin and migrate to the intestine to mature and complete its life cycle. If a pregnant dog has hookworms, the pregnancy may reactivate larvae. These larvae will enter the female's circulation and pass to the puppy through the placental blood flow. Finally, puppies may become infected through the mother's milk. This is considered to be an important route of infection for puppies 

How can I tell if my dog is infected?

The most significant problems appear related to intestinal distress and anemia. Blood loss results from the parasites sucking blood from intestinal capillaries. The presence of pale gums, diarrhea, or weakness might suggest the need to specifically determine the dog's red blood cell count. Some dogs experience significant weight loss, bloody diarrhea, or failure to grow properly with hookworm infection. Skin irritation and itching can be one of the common signs of a heavily infested dog. The larvae burrow into the skin and cause the dog a great deal of itching and discomfort. 

Hookworms are diagnosed with a microscopic examination of a small stool sample. Since there are so many eggs produced on a daily basis, they are rather easily detected. One adult female hookworm can produce as many as 20,000 eggs a day! In puppies, large numbers of worms usually must be present before eggs are shed into the stool. For this reason, fecal examination may be less reliable in very young puppies than in adult dogs. 

How are the hookworms treated?

There are several very effective drugs that will kill hookworms. These are given by injection or orally and have few, if any, side-effects. However, these drugs only kill the adult hookworms. Therefore, it is necessary to treat again in about 2-4 weeks to kill any newly formed adult worms that were larvae at the time of the first treatment. 

A blood transfusion may be necessary in some dogs because of the rather severe anemia which can be produced if left undiagnosed for too long. Since the dog's environment can be laden with hookworm eggs and larvae, it may be necessary to treat it with a chemical to kill them. There are some available that are safe to use on grass.


Roundworms are worms which have round bodies. On average, they are about 7-12 cm  (3-5 inches) long. They live in the dog's intestines and consume partially digested food. Unlike hookworms, they do not attach to the intestinal wall; rather, they literally swim in their food. Roundworms, sometimes called ascarids, pass moderate numbers of microscopic eggs which are found in the dog's stool. Like hookworm eggs, they must be found with a microscope.   

How did my dog get roundworms?

Puppies born to mothers that have had roundworms at any time in the past can transmit them to their puppies before birth. This is true even if the mother tests negative for roundworms because roundworm larvae (immature worms) encyst in the mother's muscle tissue and are not detected by our tests for adult worms. Another major source of roundworm infection for puppies is the mother's milk. Roundworm larvae may be present in the mother's mammary glands and milk throughout the period of nursing the puppies. 

Dogs may become infected by swallowing roundworm eggs which contain infective larvae. The larvae hatch out in the dog's stomach and small intestine and migrate through the muscle, liver, and lungs. After several weeks, the larvae make their way back to the intestine to mature. When these worms begin to reproduce, new eggs will pass in the dog's stool, and the life cycle of the parasite is completed. Obviously, roundworm eggs passed in one dog's stool may be infectious to other dogs. A large number of other animal species have been found to harbor roundworms and represent potential sources of infection for dogs. These include cockroaches, earthworms, chickens, and rodents. 

How is roundworm infection diagnosed?

Roundworms are diagnosed by a microscopic examination of the dog's stool. They pass a moderate number of eggs, so examination of more than one stool sample may be necessary to find them. Occasionally, the mature worms can be found in the dog's stool or vomit. 

How are roundworms treated?

Treatment is quite simple. Several very safe and effective drugs are available to kill roundworms in the intestine. Some of these drugs temporarily anesthetize the worms so that they pass out of the dog with a normal bowel movement. The live or dead worms are found in the stool. Because of their large size, they are easily seen At least two or three treatments are needed; they are typically performed at 2-4 week intervals. None of these treatments will kill the immature forms of the worm or the migrating larvae.

The eggs are highly resistant to most commonly used disinfectants and to even harsh environmental conditions. Therefore, removal of the dog's stool is the most effective means of preventing re-infection. A 1% solution of household bleach can be used to remove the sticky outer coating of the eggs, making it easier to rinse them away. This does not, however, kill the eggs. Remember the obvious limitations about where bleach may be safely applied. 

Canine roundworm is infectious to humans

Many cases of roundworm infection in humans are reported each year. Children, in particular, are at risk for health problems should they become infected. A variety of organs may be affected as the larvae migrate through the body. In suitable environments, the eggs may remain infective to humans (and to dogs) for years. Check with your vet about conditions in your part of the country.

What can be done to control roundworm infection in dogs and to prevent human infection?

  • Pregnant bitches should be de-wormed in late pregnancy to reduce potential contamination of the environment for newborn puppies.
  • All new puppies should be treated by 2-3 weeks of age. To effectively break the roundworm life cycle, puppies should be de-wormed on the schedule recommended by your veterinarian.
  • Prompt de-worming should be given when any parasites are detected; periodic de-worming may be appropriate for dogs at high risk for re-infection. Adult dogs remain susceptible to re-infection with roundworms throughout their lives.
  • Dogs with predatory habits should have a fecal examination several times a year. Rodent control is desirable since rodents may serve as a source of roundworm infection for dogs.

Prompt disposal of all dog feces is important, especially in yards, playgrounds, and public parks. Strict hygiene is especially important for children. Do not allow children to play in potentially contaminated environments.

Most heartworm prevention products contain a drug that will prevent roundworm infections. However, these products will not kill the adult roundworms so they must be treated if present.



Whipworms are intestinal parasites which are about 6 mm (1/4 inch ) long. They live in the cecum and colon of dogs where they cause severe irritation to the lining of those organs. This results in watery, bloody diarrhea, weight loss, and general debilitation. They are one of the most pathogenic worms found in dogs. 

How did my dog get whipworms?

Whipworms pass microscopic eggs in the stool. The eggs are very resistant to drying and heat, so they can remain viable in the dog's environment for years. They mature and are able to re-infect the dog in 10-60 days. The eggs are swallowed and return to the lower intestinal tract to complete the life cycle. 

How do I know my dog has whipworms?

Whipworms are diagnosed with a microscope by finding eggs in examination of the stool. However, multiple samples are often required because these parasites pass small numbers of eggs on an irregular basis. Any dog with chronic diarrhea can be reasonably suspected to have whipworms, regardless of several negative stool examinations. It is an accepted practice to treat for whipworms based on assumption of infection. Response to treatment is an indication that whipworms were present but could not be detected on fecal examination. 

How is whipworm treated?

Heartworm medications now contain ingredients that prevent whipworms.

There are several drugs that are very effective against whipworms. Two treatments are needed at a 3-4 week interval, but because re-infection is such a problem, it is advisable to treat again every 3-4 months. Whipworms are not nearly as common now because of widespread use of the types of heartworm prevention products.


Tapeworms represent the minority of the parasites that are seen in dogs, but do occur. They apparently do not stimulate any immunity by the host. The common tapeworms of dogs pose no threat to humans. However,  Echinococcus, an uncommonly found tapeworm but increasingly found, is potentially fatal to humans.

How did my dog get tapeworms?

Two common tapeworms of dogs are Dipylidium caninum and Taenia pisiformis. They are passed to the dog by ingestion of the Dipylidium.

  • The flea is the intermediate host of Dipylidium.

  • Rabbits and rodents are the intermediate host for Taenia.

How do I know my dog has a tapeworm?

Dogs ingest the intermediate host and release the intermediate stage of the tapeworm into the GI of the canine host where the parasite matures to an adult in the small intestine. Eggs are shred to the environment from the GI of the dog in small segments that look like small pieces of rice. These segments can sometimes be seen in the fresh feces or attached to the adjacent tissues of the dog's anus. As the segments desiccate, they release microscopic eggs into the environment for the cycle to begin again.

What is the treatment for tapeworms?

Mature adult Dipylidium and Taenia reach 5-cm or more in length. Signs of Dipylidium and Taenia infestation are unapparant. Their only threat is their repugnancy and potential to further debilitate an ill pet. Treatment for these two tapeworms is several drugs taken either oral or by injection under the skin.

How do I prevent tapeworms?

Prevention of Dipylidium consists of good flea control. Prevention od Taenia is difficult if the dog has contact with rabbits or rodents and may require de-worming several times a year.

1. Echinococcus multilocularis is a small tapeworm that lives in the artic fox, wolf, domestic cat and dog as the final host. Diagnosis in the dog is primarily by microscopic fecal exam. The intermediate host is the rodent, such as moles, shrews and field mice. This parasite is moving south and is now found in some of the northern tier states of the US. The threat comes from the ingesting fruit, food or water contaminated by the feces of the fox, cat or sled dog. The camping has exposed more humans and their pets to the potential of Echinococcus. Once the eggs of the Echinococcus infects a human, they form a large cyst of the liver. The only treatment is surgical removal. The cyst itself is very fragile and can rupture with manipulation resulting in death.

Treatment  for Echinococcus in dogs is use of the same drugs as other tapeworms.

2.Diphyllobothrium latum (DL) is the largest tapeworm of the dog. It is uncommon accept in remote areas of the northern US and Canada, where dogs, humans and wildlife may come in contact. The final host in addition to the dog is man, but it also exists in the cat, fox and bear.  The worm enters the final host by ingesting raw or undercooked fish. Eggs are shed direcly into the feces. If shed into water, small crustaceans swallow the egg which are then consumed b fresh water fish and ultimately the final host. The worm is asymptomatic in the dog, but in man can produce severe anemia. Treatment is no different than other tapeworms in the dog. Diagnosis is by microscopic fecal exam.


Heartworms are a major parasitic disease in dogs worldwide. Canine heartworm,  (Dirofilaria immitis), is transmitted from dog to dog by mosquitoes. Many different species of mosquitoes can carry heartworm larvae, so controlling the mosquito is not a feasible method of prevention

Development of Heartworm

The life cycle of heartworm is developed in the following stages: 

Adult heartworms reside in the right heart, pulmonary arteries, and vena cava of the dog.

The heartworm larvae (microfilaria) are released into the dog's blood.

The mosquito ingests the larvae with the dog's blood.

After 10 to 30 days, the infective larvae appear in the salivary gland of the mosquito.

The mosquito bites another dog, and transmits the infective larvae.

The larvae migrate in the dog's body for about four months before reaching the dog's heart.

Worms mature into adults during the next two to three months.

The heartworm larvae appear in the dog's blood. 

Although most cases of heartworm are transmitted by this life cycle, there are two important exceptions.

1.The first exception is that larvae can be passed from infected female dogs to her unborn puppies through the placenta..

2.The second exception is that the heartworm larvae can be passed during blood transfusions from donor dogs to recipients. Consequently, all donor dogs must be clear of heartworm disease before being used in a transfusion program. 

How do I know if my dog has heartworms?

Many heartworm-infected dogs are free of symptoms. In dogs without symptoms, any sign of heartworm depend on the number of worms the dog is infected with. The higher the number of worms, the more severe the disease. The most common symptoms are coughing, respiratory distress, and exercise intolerance. In more severe cases, a dog will cough up blood because the pulmonary blood vessels have been ruptured. 

Heartworm disease is caused by damage from the adult worms once they get into the blood vessels of a dog's lungs. The worms cause the blood vessels to swell and become scarred. As the blood vessels shrink in diameter, blood flow becomes increasingly restricted. In the right lung, blood pressure begins to rise, which causes pulmonary hypertension. This increased vascular pressure means that the right side of the dog's heart has to work harder to pump blood through the lung. Eventually, the pressure will lead to failure of the right heart. 

How do I prevent heartworms?

The preferred method for prevention is testing and giving medicine during the months mosquitoes are present in the environment. Regular testing for heartworm is a critical part of prevention. It is the only sure way to determine that prevention has been successful. Every dog over six-months old must be tested before prevention is started. 

Puppies should be started on preventative treatment as soon as it is safe, usually by six to eight weeks. Adult dogs should start treatment shortly before the local transmission season, and continue treatment until two or three months after the season. Dogs that live in warm climates, such as Florida, should be given yearly prevention. 

Talk to your vet to see what is recommended for your part of the country.


A one celled protozoans that are intracellular parasites of the lining of the small intestine that occur with some frequency. Eimeria 
and Isospora are the two most common coccidia of the dog. Infection occurs upon ingestion of contaminated feces or food. Upon ingestion, the 
parasite colonizes the lining of the small intestine and reproduction begins. As reproduction progresses the new coccidia are shed through the 
feces to the environment. Shedding of the protozoan can be asymptomatic or associated with signs of diarrhea and bloody stools. Puppies are most 
commonly affected.

Most infections are not apparent and resolve on their own by self immunization.. Treatment for coccidia consist of antimicrobials that are bacteriostatic. These drugs stop the growth of coccidia and then the host¹s immune system responds to rid the intestine of the parasite.

In kennel environments, prevention is essential. Usually good steam cleaning of kennels will eliminate the infestation of the environment.

A tiny coccidia that is can be difficult to confirm on routine microscopic fecal exams. special stains are required. The 
organism infects man, cats and dogs. Puppies are primarily at risk. The disease produces voluminous watery diarrhea that varies with the severity 
of the organism and the health of the host. Immunocompromised dogs are at severe risk. Puppies are most likely to show signs. No treatment is 
available for eliminating the organism although coccidiastats have been used with questionable success. Antibiotics may have some effect. 

Treatment is primarily symptomatic to combat fluid loss.

Another protozoan intestinal parasite that infects many mammals including man.  The parasite is one of 
several flagellates (mobile tails attached to the single cell) that infect mammals. The disease produced is variable depending on the 
individual and age. Young puppies are most often affected. Signs usually occur 1-2 weeks after infection and often the disease goes unnoticed or 
is self limiting after a bout of diarrhea. It can produce severe diarrhea and fluid loss. Most cases that show signs are mild with  minimal 
depression. The parasite is passed in the feces and is consumed directly by the next host. Giardia is very hardy and can remain in the environment 
for a number of months waiting for a suitable host. In addition, contaminated water is a frequent source of the flagellate. Diagnosing 

giardia can be demanding and may require frequent microscopic fecal examinations. Giardia responds very well to treatment.

Caused by a protozoan in the Leishmania species. A dog may have the disease and not appear ‘sick’ for up to five years after they contract it. There is an intermediate host, the sand fly, that bites an infected animal and passes it on the same way.  It is believed to take 3-6 months or longer from infection to possible detection.  The symptoms may not appear for up to five years and resemble other disorders - most closely limes disease. Skin disease, polyarthritis (arthritis in multiple joints), mucosal disorders (lumps on tongue, gums, etc.), damage to internal organs and possibly bleeding disorders. The skin signs seen with this disease include loss of hair, scaling of the skin, ulceration of the skin on the limbs or ears, formation of nodules on the body and sometimes pustules. All the time the parasite is destroying the liver, kidneys and other organs.

There is a blood test for this desease but no cure. If it is discovered early enough, there are medicines that will maintain the dog but the dog may still be contagious. In the latter stages of the disease, little can be done and the best course of action is to put the dog to sleep. Humans can contract this disease.


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