Intestinal Parasite FAQs

It’s a fact:

  • There are 65 million dogs in the U.S.
  • Heartworm disease has been reported in all 50 states.
  • The Companion Animal Parasite Council (CAPC) recommends year-round treatment with broad-spectrum heartworm medicine that has activity against parasites with zoonotic potential “because dogs may be exposed to and become infected with roundworms, hookworms, tapeworms and other parasites throughout the year. Consequently, stages capable of transmitting parasites can be shed into the environment, regardless of season or climate*.”
  • One intestinal parasite worm can produce more than 100,000 eggs a day.
  • Over 10,000 cases of human roundworm infections are reported annually in the U.S.
  • Stomach ache, skin rashes, pneumonia, and blindness may result from human infection by zoonotic internal parasites.
  • Roundworms may work their way through the body into the eye.
  • Hookworm progress can be seen under the skin as it migrates from the penetration site.
  • You can actually see tapeworms. As the rice-like segments are shed in the feces, some may remain under the dog’s tail. Owners often find these slimy, white, wiggling segments on their carpets, furniture, and clothing.

*Reprinted from CAPC Guidelines. For more information on pets and parasites, visit

Can roundworms and hookworms infect people?
Yes. These infections, like others acquired from animals, are called zoonotic infections or zoonoses. You owe it to yourself and your family to find out about these zoonotic infections. Learn how to prevent them.

How do pets get worms?

Dogs and cats of any age may get roundworms and hookworms, but they are most vulnerable when they are very young. In fact, it is not unusual for puppies of only 2-3 weeks of age to harbor a significant number of worms. That’s because these worms are often passed from a mother to her puppies before birth, Sometimes they are passed shortly after birth, through her milk.

How do these worms infect people?

Dogs and cats infected with these worms contaminate their surroundings by passing eggs or larvae in their feces (waste). Because pets will pass feces anywhere, they may contaminate a large area quickly. These eggs and larvae are resilient and can survive in areas such as parks, playgrounds, and yards. Even inside homes. People get roundworm and hookworm infections through direct contact with infected feces. This usually happens by chance ingestion of contaminated soil, sand or plant life, Hookworm larvae penetrate the skin. Children are more vulnerable to infection than adults, perhaps because they play on the ground with dirt that may be contaminated. Maybe it’s because kids are more likely to put dirty objects into their mouths. Some children pass through a stage in which they eat dirt (pica). Thus, they are more prone to get these infections.

How can I protect my pets – and my family and myself against worm infections?

Your veterinarian can recommend treatments to eliminate and help prevent these worm infections. Since these products are available in many forms, you and your vet can choose which one works best for your dog or cat. Ask for the product that is most effective against the worms to which pets in your area are likely to be exposed.

Take steps to prevent roundworm & hookworm infection:

  • Have puppies and kittens dewormed by your vet at an early age.
  • Start or keep your pets on a preventive drug program that treats and controls these worms.
  • Learn to recognize and avoid possibly contaminated soil, sand, plants, and other objects. Teach children to do the same.
  • Keep play areas, lawns, and gardens around your home free of animal waste by bagging and disposing of pet feces and covering sandboxes when not in use.
  • Obey leash laws.


Roundworms are the most common canine intestinal parasite. Almost all dogs will have roundworms at some time, usually as puppies. They spread easily and can be contracted in different ways-through the mother’s milk or by eating larvae in the environment. Roundworm eggs from an infected dog’s feces can remain dormant in the soil for years, posing a risk to your family.

Signs of Roundworm Infection:

  • Diarrhea
  • Adult Worms Can Be Visible in Feces
  • Respiratory Distress
  • Weakness
  • Swollen Abdomen

How do roundworms harm people?

Roundworms enter the body when ingested as eggs that soon hatch into larvae. These larvae travel through the liver, lungs, and other organs. In most cases, these “wandering worms” cause no symptoms or apparent damage. However, in some cases they produce a condition known as visceral larva mignon. The larvae may cause damage to tissue and sometimes affect the nerves or even lodge in the eye. In some cases, they may cause permanent nerve or eye damage, even blindness.


Hookworms attach to the intestinal wall and feed on your dog’s blood. This parasite can be lethal to puppies. Hookworm eggs enter the environment through an infected dog’s feces and hatch into larvae which live in the soil. Hookworms can infect your dog through the paws, belly or licking (cleaning).

Signs of Hookworm Infection:

  • Diarrhea
  • Weakness
  • Weight Loss
  • Black Tar-Like Stool

How do hookworms harm people?

Hookworm larvae typically move about within the skin, causing inflammation in the affected skin. This is called cutaneous (skin) larva migrans. One type of hookworm can penetrate into deeper tissues and cause more serious damage to the intestine and other organs.


Tapeworms are one of the most common internal parasites pet owners can actually see. They are repugnant and absorb vital nutrients that your dog needs. Dogs get tapeworms by ingesting infected fleas or by eating infected rabbits or small rodents. Tapeworms are seen in dogs of all ages.

Signs of Tapeworm Infection:

  • Visible segments on feces, haircoat, or on bedding (appear as small white worms that may look like grains of rice or seeds)
  • Scooting (dog rubs bottom along floor)


Whipworms are scientifically classified as Trichuris vulpis, Trichuris campanula (canine) and Trichuris serrata (feline) are called as such because they are slender and whip-like on one end and thick and flat on the other, hence giving the appearance of a whip; the front portion of which being the “whip” and the caudal part representing the “whip handle.”

Although these parasites can be as menacing as Hookworms and can sometimes be fatal, there have been very few reports of humans being infected, and most of the cases are often caused by Trichuris vulpis. It is known to infect both cats and dogs directly, but since cats are not as prone to Whipworms as dogs are if you own a dog, then this article is best suited for you.

Whipworms exist as very minute parasitic eggs with thick brown outer coverings that are tough and impenetrable, thus allowing the eggs to survive untouched in the soil for years. They are also highly resistant to freezing and are unaffected by exposure to extreme heat and sunlight. And for the above reasons, it can subsist for long, until a dog accidentally ingests it.

When that happens, it is known that Whipworms live in the large intestines and the cecum (which is the junction of the large and small intestine) of man’s best friend. They attack a dog’s body by burying its head into the outer linings of the large intestines and cecum only. It is specific and precise in choosing its host, and once it settles in a canine, the parasite begins to cause havoc in their body.


Giardiasis is an intestinal infection caused by a parasitic protozoan (single celled organism) called Giardia lamblia. These protozoans are found in the intestines of many animals, including dogs and humans. This microscopic parasite clings to the surface of the intestine or floats free in the mucous lining the intestine. Veterinary research documents suggest that 5% to 10% of all dogs in North America have giardiasis at any given time. Surveys also show that about 14% of the adult dog population and over 30% of dogs under one year of age were infected at some point during their life, and thus contributed to passing along this intestinal infection to other dogs. Another Vet research article I found suggests that 100% of kennel dogs, 50% of pups, and 10% of well-cared for dogs carry giardia.

How did my dog get Giardia?

Giardia lives and reproduces in the small intestine of host animals. Giardia Vophozoites, the free-living stage of the organism, form infective cysts that are passed out in the feces. If the cysts are present in a wet or damp environment, they can survive in a viable state for a few weeks to several months. Giardia infections are transmitted via ingestion of trophozoites or cysts in contaminated water or food. If a giardia cyst is ingested, the cyst wall is broken down during the digestive process, and the trophozoite stage begins to colonize the upper small intestine. Transmission also occurs by direct contact, especially with asymptomatic carriers. More recently, giardiasis has also been recognized as being able to be sexually transmitted. Giardia is so prevalent throughout North America because it is highly contagious. The ingestion of as few as one or more giardia cysts may cause the disease, as contrasted to most bacterial illnesses where hundreds to thousands of organisms must be consumed to produce illness,

What harm does Giardia do to my dog?

Giardia causes its unpleasant effects on the body not by invading the tissues, but simply by being in the way. It multiplies to the point where it sort of paves the lining of the intestine and blocks normal digestion (malabsorption). This causes only partially digested food to get lower in the digestive tract than it should, causing diarrhea.

What are the clinical signs associated with infection?

The trophozoites divide to produce a large population, and then they begin to interfere with the absorption of food. Clinical signs range from none in asymptomatic carriers to mild recurring diarrhea consisting of soft, light-colored stools, to acute explosive diarrhea in severe cases. Other signs associated with giardiasis are weight loss, listlessness, fatigue, mucus in the stool, and anorexia. These signs are also associated with other diseases of the intestinal tract and are not specific to giardiasis. These signs, together with the beginning of cyst shedding, begin about one week post-infection. There may be additional signs of large intestinal irritation, such as straining and even small amounts of blood in the feces. Usually, the blood picture of affected animals is normal, though occasionally there is a slight increase in the number of white blood cells and mild anemia. Without treatment, the condition may continue, either chronically or intermittently, for weeks or months.

How can I be sure my dog has Giardia?

Diagnosing giardia is not easy. Diagnosis can be done in one of two ways: via fecal sample by a vet or via educated evaluation of clinical findings by the breeder/owner. Via fecal sample is not straightforward. Even when a flare is at its worst, the cysts will not be shedding in every single stool. Therefore, a negative report does not rule out giardia.


Coccidiosis is an intestinal disease that affects several different animal species including canines and humans. Coccidia is one of the most prevalent protozoal infections in North American animals, second only to giardia. Eimeria and Isospora are the two genera that are often referred to as “coccidia.” These two genera contain a large number of species that infect a variety of animals throughout the world. The diseases caused by these microscopic protozoal parasites are referred to collectively as coccidiosis, and they vary tremendously in virulence. Some species cause diseases that result in mild symptoms that might go unnoticed (i.e., mild diarrhea) and eventually disappear, while other species cause highly virulent infections that are rapidly fatal. The causative agent is a protozoan that can multiply rapidly. The major damage is due to the rapid multiplication of the parasite in the intestinal wall, and the subsequent rupture of the cells of the intestinal lining. Several stages of multiplication occur before the final stage, the oocyst is passed in the feces. Oocysts are extremely resistant to environmental stress and are difficult to completely remove from the environment. Oocysts are frequent contaminants of feed and water, and when the sporulated oocysts are ingested by other animals, they start the life cycle over in the new host.

Clinical Signs

Clinical signs of coccidiosis usually are present or shortly following stress such as weather changes; weaning; overcrowding; long automobile or plane rides; relocation to a new home and new owners; and unsanitary conditions. Symptoms or signs of coccidiosis will depend on the state of the disease at the time of observation. In general, Coccidiosis affects the intestinal tract and symptoms are associated with it. In mild cases, only watery diarrhea may be present, and if blood is present in the feces, it is only in small amounts. Severely affected animals may have a thin, watery feces with considerable amounts of intestinal mucosa and blood. Straining usually is evident, rapid dehydration, weight loss and anorexia (off feed) also may be clinically visible. One of the most prevalent canine coccidias is S. tenella and during autopsies of dead animals appears as microscopic muscle cysts in the host animal. Oocysts in the feces of dogs are also microscopic in size and can only be positively identified through lab tests or direct observation under a microscope.

“Nervous coccidiosis” is a nervous system condition associated with coccidial infection. Signs arc consistent with central nervous system involvement and include muscle tremors, convulsions and other central nervous system symptoms. A consistent sign in “nervous cocci” dogs is that stimulation of any type seems to trigger the symptoms.

Death may follow the acute disease either directly or from secondary diseases such as pneumonia. Animals that survive for 10 to 14 days may recover, however, permanent damage may occur. Research has indicated that canines may experience reduced food consumption for up to 13 weeks following clinical infection. Diagnosis usually is obvious, but confusion does exist – apparently, normal animals can also have oocysts present in their feces. Diarrhea may be present in the animal before the oocysts can be found. Therefore, a confirmed laboratory diagnosis may not always be possible. Laboratory findings should be correlated with clinical signs for a diagnosis.

The susceptibility of animals to this disease varies. The ingestion of oocysts may not produce the disease; some animals constantly carry them without being affected.

Recovered animals develop immunity and seem to be partially resistant to reinfection.

Coccidiosis is frequently referred to as an opportunist – a disease that will develop when other stress factors are present. For example, the highest incidence of coccidiosis is in the first 21 days after a dog has changed owners and moved to a new residence. If a normal animal carries oocysts, it is relatively easy for rapid development when the conditions are right – adverse weather, shipping, dog food changes, new owners, new residence, and other stresses are important.

In the case of a confirmed outbreak of coccidiosis in a kennel full of Beagles, the following steps should be started immediately:

  1. Separate the sick animals from the healthy ones.
  2. Treat sick animals with effective medications.
  3. Medicate all the dogs in the kennel or home, as the other animals are likely infected.

General information on coccidiosis in canines:

  1. Coccidiosis is an opportunistic disease – it generally affects stressed animals.
  2. Kennel conditions provide ideal circumstances for an outbreak.
  3. In most confinement situations, prevention with sulfaditnethoxine drug such as Albon® is recommended.
  4. Mass treatment of all dogs in an entire kennel is usually the only effective method.
  5. Sick animals should be treated as soon as possible and isolated from the healthy animals.
  6. Have your veterinarian confirm positive diagnosis of the coccidia protozoa in your dog’s feces through the use of lab tests or positive identification through direct observation under a microscope.

How can I be sure my dog has Coccidia?

Diagnosing coccidia is not easy. Diagnosis can be done in one of two ways: via fecal sample by a Vet or via educated evaluation of clinical findings by the breeder/owner or the Vet. Via fecal sample is not straightforward. Even when a flare is at it’s worst, the oocysts may not be shedding in every single stool. Therefore, a negative report does not rule out coccidia.

Heart Worms

Heartworms – long, spaghetti-like worms that can grow 10-inches in length, live in the hearts, lungs, and bloodstreams of infected dogs. Heartworm disease is spread when a mosquito bites an infected dog. Microfilariae in the dog’s blood mature into infective larvae in the mosquito, which are transferred to another dog by the mosquito’s bite. In approximately six months, the larvae mature into adult heartworms.

Untreated, heartworms can lead to death in dogs. These are undoubtedly among the most devastating of canine parasites. Fortunately, needless pain and suffering can be prevented with an animal heartworm test, and the medicine veterinarians prescribe most – IVERHART MAX and IVERHART PLUS.

Signs of Heartworm Disease:

  • Coughing
  • Lethargy
  • Exercise intolerance
  • Heavy Breathing
  • Weight Loss

Fleas and your pet

Fleas can make the life of any dog or cat miserable. Just one bite to a pet that is allergic to fleas can put him in agony from constant rubbing and scratching of the irritated skin. Also called “pruritus,” this unpleasant itching can become so intense that pets will actually scratch until the skin bleeds.

The Flea Cycle

Fleas spend most of their lifetime off the pet. They go through a life cycle that includes egg and cocoon stages. While adult fleas are relatively easy to kill with insecticides, the egg and cocoon stages are very resistant.

The entire life cycle of the flea (from egg to larva, from larva to cocoon, from cocoon to adult) can vary from 14 days during warm, moist weather, to several weeks or months under extremes of climatic conditions.

The adult flea must dine on your pet’s blood to survive. Fleas can jump from 16 to 36 inches. For their size, this is like a human jumping over the Washington Monument!

  • Successful flea control must be directed at both the pet and the environment.
  • Always coordinate treatments to break the life cycle of the flea and to treat the environment and pet at the same time.

Flea Bite Allergies

Fleas can cause a condition known as allergic dermatitis. Because some dogs and cats are allergic to flea saliva, a single flea bite causes the animal to chew and scratch the area where the flea has bitten. This can cause redness, sores and hair loss. One or two fleas on an allergic animal may trigger the same response as a hundred flea bites.

Some pets need medication to control the scratching and chewing until a flea control program can be started. Animals with severe allergic dermatitis may require intermittent use of prescription medications during those periods when fleas are most active: during hot, humid months.

Remember, use of these medications is not a substitute for a flea control program.

Medical Problems Associated with Fleas

  • Skin Infections: “Hot spots” arc frequently seen in animals with flea infestations. Hot spots can pop up from intense scratching and licking. Hot spots can also be found on non-allergic animals as the result of problems unrelated to fleas.
  • Tapeworms: Fleas are an essential link in the life cycle of the tapeworm in the cat or dog. A good flea control program should accompany the treatment of your pet for tapeworms. The tapeworm is a segmented worm that is only occasionally passed whole. Instead, you will usually only see some individual white segments passed in the stool, around the cat’s anus, or on her bedding. These may have the appearance of rice grains.
  • Anemia: A pet heavily infested with fleas can lose a significant portion of its circulating blood. This may lead to decreased resistance to other disorders and cause your pet to act lethargic.

Did you know? Sir Isaac Newton, who first described the principle of gravity, also invented the swinging cat door for the convenience of his many cats.