Roundworm Infection in Dogs
Roundworms (nematodes or Ascarids) are intestinal parasites that live freely in the intestine, feeding off of partially digested intestinal contents. Their name is derived from their tubular or “round” shape.
Toxocara canis and Toxascaris leonina are two important species of roundworms in dogs. Toxocara canis causes more significant disease and also may be transmitted to humans.
How did my dog get roundworms?
Microscopic eggs are passed from infected dogs in the feces. These are ingested by sniffing or licking infected feces. They are also spread by other animals such as rodents and birds. In these animals, the roundworms are merely transported. They do not mature into adults but if this paratenic host is eaten by a dog, completion of the life cycle will occur and the dog can become infected.
In the dog, the roundworm undergoes a complicated life cycle before mature roundworms are found in the bowel. This involves several stages and also migration through various tissues. Roundworm larvae (immature worms) can encyst in the host’s tissues. This is important in the female dog because these encysted larvae will start to develop during pregnancy and ultimately cross the placenta into an unborn puppy. Thus puppies can be born with roundworms and can pass fertile eggs from adult worms in their stools by the time they are approximately eleven days old. Roundworm larvae may also enter the mother’s mammary glands and be transmitted through the milk.
Are roundworms a threat to my dog?
Roundworms are most threatening to puppies. The most common consequence of roundworms is growth reduction. Since roundworms feed off of partially digested food, they rob the growing puppy of vital nutrients. These puppies often have a characteristic “pot-belly” that is due to the growing roundworms inside the puppy’s abdomen.
The life cycle of Toxocara canis is more complicated than that of other nematode worms found in dogs. Roundworm larvae swallowed by adult dogs usually encyst in the dog’s tissues. Few roundworms will mature in the bowel. Consequently few eggs are passed in the stool leading to difficulty in definitive diagnosis and treatment.
How are roundworms diagnosed?
In puppies we consider clinical signs such as stunted growth, potbelly, and recurrent diarrhea as a good indication of roundworm infection. Definitive diagnosis is made by microscopic examination of the dog’s feces.
Is it true that children can get roundworm infections?
If the infected eggs of Toxocara canis are swallowed by people, the larvae can invade the tissues and become encysted in various organs. Humans act like any other paratenic host. If a large number of infected eggs are ingested, clinical disease may become apparent. This is particularly important if children are infected with roundworms.
Very rarely, liver problems may result from roundworm larval migration (visceral larval migrans). Even less commonly, the larvae can migrate into the eye and cause blindness (ocular larval migrans).
How are roundworms treated?
Treatment is simple and effective. There are many safe and effective preparations available to kill roundworms in the intestine.
In addition, many heartworm preventives are also effective against intestinal roundworms and help prevent future infections.
Unfortunately, the majority of preparations available today kill only the adult worms and do not affect migrating or encysting larvae. It is therefore important that repeated treatments are administered. Your veterinarian will advise you on the best treatment and prevention plan for your pet.
What about roundworm eggs shed in the environment?
Initially the eggs are not infective. After a period, which may vary from weeks to months, the eggs develop into infective larvae. Under ideal conditions, this takes approximately four weeks. These infective larvae can remain viable in the environment for a considerable time and are particularly resistant to changes in temperature and humidity.
The best environmental treatment is prevention. Remove your dog’s feces as soon as possible to prevent the spread and transmission of roundworms.
What is the most effective strategy I can use to control infection in my dogs, protect my family and reduce contamination of the environment?
Deworm pregnant dogs in late pregnancy, after the 42nd day or after six weeks of pregnancy. This will help reduce potential contamination of the environment for newborn puppies.
Puppies should be dewormed, starting at about two weeks of age and repeated regularly. Your veterinarian will design the most appropriate deworming schedule for your pets.
Adult dogs are susceptible to re-infection with roundworms throughout their lives. Routine deworming and prevention is important.
1.Rodent control is important since rodents can serve as a source of infection.
Dogs should be restrained from defecating in children’s play areas and there should be prompt disposal of all dog feces, especially in gardens, playgrounds and public parks.
Practice strict hygiene particularly with children. Do not allow them to play in potentially contaminated environments.
Roundworm Infection in Cats
Roundworms are one of the most common intestinal parasites of the cat. They can be an important cause of illness, and even death, in kittens. As their name implies, these are large-bodied round worms, averaging about 3-6 inches (8-15 cm) in length. They do not attach to the wall of the intestine, as do some worms. Instead, they are literally “swimming” freely within the intestine.
The scientific name for the feline roundworm is Toxocara cati. Another less common roundworm, Toxascaris leonina, can infect both dogs and cats. Roundworms are sometimes called ascarids and the disease they produce is called ascariasis.
What cats are likely to get roundworms?
Risk factors for roundworm infection include female cats with pre-existing infection, environments that are heavily contaminated, and the presence of intermediate hosts such as roaches, earthworms and birds.
What are the clinical signs of roundworm infection?
Roundworms are not particularly pathogenic or harmful to adult cats, but large numbers may cause life-threatening problems in kittens and debilitated older cats. In kittens, common clinical signs include a pot-bellied appearance, abdominal discomfort, depressed appetite, vomiting and diarrhea, or poor growth.
In both kittens and adult cats with small numbers of worms, there may be no clinical signs of infection.
How do cats get roundworms?
Trans-mammary or milk-borne infection is the major route of roundworm transmission to kittens. The immature roundworms called larvae are present in the mother’s mammary glands and pass through her milk to the kittens. Additionally, both kittens and adult cats may become infected by swallowing eggs that contain infective roundworm larvae. These eggs may come from the feces of infected cats or from the tissues of intermediate or paratenic hosts. Common intermediate hosts for roundworms include earthworms, cockroaches, rodents and birds.
Once ingested, the roundworm larvae hatch out in the cat's gastrointestinal tract and migrate through the muscle, liver, and lungs. After several weeks, the larvae return to the intestine to mature. When these worms begin to reproduce, eggs will pass into the cat's stool, thus completing the life cycle of the parasite.
How are roundworms diagnosed?
To diagnose roundworm infection, a small amount of the cat’s stool is mixed into a special solution that causes the eggs to float to the top of the solution. The sample is covered with a glass slide on which the floating eggs will collect, and the slide is examined under a microscope. The distinctive eggs are easily recognized under the microscope. Roundworm eggs are usually plentiful but, in some cases, it may take more than one fecal examination to find them. Occasionally, intact adult roundworms can be found in the cat's stool or vomit.
What is the treatment for roundworms?
Fortunately, treatment is safe, simple, and relatively inexpensive. The dead and dying roundworms pass into the stool after administration of the anthelmintic or deworming medication. Since none of these treatments will kill the immature forms of the worm or the migrating larvae, at least two or three treatments are needed; they are typically performed at two to three week intervals. Ideally, kittens are dewormed with each visit for booster vaccinations.
What is the prognosis for a cat diagnosed with roundworms?
The prognosis of a roundworm infection is good if appropriate medication is given promptly. However, in some instances, extremely debilitated kittens may die.
Can I prevent my cat from getting roundworms?
Prevention of roundworm infection should include the following measures:
Breeding queens should be dewormed prior to pregnancy and again in late pregnancy. This will reduce environmental contamination for new kittens.
New kittens should be appropriately dewormed as recommended by your veterinarian. The first deworming should be given at two to three weeks of age. Note that this is prior to the time most kittens are seen for first vaccines. It is entirely appropriate to present new kittens for deworming only.
Adult cats remain at risk for re-infection with roundworms throughout their lives. Whenever roundworms are seen, the cat should be promptly dewormed. It is appropriate to routinely deworm all cats that remain at high risk for reinfection. For example, it is advisable for cats with predatory habits or indoor/outdoor cats to have a fecal examination several times a year.
Monthly heartworm and flea preventive products that are effective against roundworms can be administered. This is the easiest and simplest method for preventing roundworms. Your veterinarian can advise you of the appropriate time to give these products, based on your specific geographical area.
Control of insects and rodents is important since they may serve as sources of roundworm infection for cats.
Stool should be removed from litter boxes daily, if possible. Litter boxes can be cleaned with a bleach solution (one cup of chlorine bleach in one gallon of water) to facilitate removal of eggs. Rinse the litterbox thoroughly to remove all bleach since it is toxic to cats. Surfaces that may be contaminated with roundworm eggs can also be treated with this bleach solution. This solution makes the eggs easier to rinse away but does not kill the eggs. Always wash your hands after handling litterbox material.
Appropriate disposal of cat and dog feces, especially from yards and playgrounds, is important. Roundworm eggs may remain viable in the environment for long periods unless they are exposed to direct sunlight or very dry conditions.
Strict hygiene is especially important for children. Do not allow children to play in potentially contaminated environments. Be mindful of the risk that public parks and non-covered sandboxes pose. Even though stool may not be visible, roundworm eggs may be present. Sandboxes that have fitted covers are popular and help prevent infection of children with roundworms.
Contact your animal control officials when homeless animals are found.
Are roundworms a danger to me or my family?
Roundworms can be a health risk for humans. The most common source of human infection is by ingesting eggs that have come from soil contaminated with cat (or dog) feces.
As many as 10,000 cases of roundworm infection in humans have been reported in one year in the United States. Children are at an increased 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 cats for years.
This client information sheet is based on material written by Ernest Ward, DVM
© Copyright 2005 Lifelearn Inc. Used with permission under license. January 13, 2017
This client information sheet is based on material written by Ernest Ward, DVM.
© Copyright 2005 Lifelearn Inc. Used with permission under license. January 13, 2017