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How Do We Get Rid of Roundworms?

Terms in this set (17)

Numerous deworming products are effective. Some are over the counter and some are prescription. Many flea control and/or heartworm prevention products provide a monthly deworming which is especially helpful in minimizing environmental contamination. Common active ingredients include:
• Febantel (active ingredient in Drontal and Drontal plus)
• Pyrantel pamoate (active ingredient in Nemex, HeartgardPlus and others)
• Piperazine (active ingredient in many over the counter products)
• Fenbendazole (active ingredient in Panacur)
• Milbemycin Oxime (active ingredient of Interceptor and Sentinel)
Products for Deworming
There are two important concepts to keep in mind about deworming. Medications essentially anesthetize the worm so that it lets go of its grip on the host intestine and passes with the stool. Once it has been passed, it cannot survive in the environment and dies. This means that you will likely see the worms when they pass so be prepared as they can be quite long and may still be alive and moving when you see them.
The other concept stems from the fact that larvae in migration cannot be killed by any of these products. After the worms are cleared from the intestine, they will be replaced by new worms completing their migration. This means that a second, and sometimes even a third deworming is needed to keep the intestine clear. The follow-up deworming is generally given several weeks following the first deworming to allow for migrating worms to arrive in the intestine where they are vulnerable. Do not forget your follow-up deworming.
Roundworms
Roundworms, often called 'ascarids,' are the most common parasite of the digestive tract in dogs and cats. Most puppies are infested with roundworms and when we look at the life cycle, we will understand why. There are 3 types of roundworms that affect dogs and cats and each has transport hosts.
Types of Roundworms
- Toxocara canis
- Toxocara cati
- Toxascaris leonina
Toxocara canis
Primary host: Dog, fox
Transport host: Small rodents
Toxocara cati
Primary host: Cat
Transport host: Small rodents, beetle, earthworms
Toxascaris leonina
Primary host: Dog, cat, fox, and other wild carnivores
Transport host: Small rodents
About Roundworms
All of these roundworms are widely distributed in North America. They are of considerable importance in young animals and in kennels. Because they can cause disease in humans, they are also very important to human health as well. The adult roundworms all live in the small intestine of the host, and their eggs look very similar. All the roundworms are prolific and an infested animal can pass millions of eggs in the feces each day. The roundworms differ, however, in their life cycles. These differences are very important when we look at how we can eliminate these parasites from our pets.
What are the Life Cycles of the Roundworms in Dogs and Cats?
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T. leonina
Of the roundworms, T. leonina has the simplest life cycle. After an animal ingests infective eggs, the eggs hatch and the larvae mature within the walls and lumen of the small intestine. The adult female worm lays eggs which are passed in the feces. The eggs become infective after remaining in the environment for at least 3-6 days. Animals become infected if they eat something contaminated with infected feces.
Mice can act as intermediate or transport hosts of T. leonina. The rodent ingests the eggs, the eggs hatch, and the larvae migrate through the tissues of the rodent. If a carnivore eats the mouse, the larvae are released in the digestive system of the carnivore and develop into adults in the wall and lumen of the intestine.
T. canis
Roundworms of the species T. canis have a more complicated life cycle and a very effective way of making sure its species will be passed from generation to generation.
An animal can acquire a T. canis infection several ways: ingestion of eggs, ingestion of a transport host, or by larvae through the uterus or milk. First let us follow the ingestion of infective eggs.

Ingestion of eggs: After a dog eats the eggs, they hatch and the larvae enter the wall of the small intestine. The larvae migrate through the circulatory system (migratory phase) and either go to the respiratory system or other organs or tissues in the body. If they enter body tissues, they can encyst (become walled off and inactive). They can remain encysted in tissues for months or years. This is the migration most commonly seen in older dogs. In very young puppies, larvae move from the circulation to the respiratory system, are coughed up and swallowed and reenter the stomach. There the larvae mature into adults. The adult worms lay eggs which pass out of the animal in the feces. The eggs need to remain in the environment 10-14 days before they become infective.

Ingestion of transport host: If an animal ingests a transport host having encysted larvae, the migration is similar to that of ingesting infective eggs. Larvae are released from the transfer host when it is eaten and digested. The larvae enter the circulation and either go to various tissues or the respiratory system.

Larvae through the uterus: A pregnant bitch that has T. canis encysted larvae in her tissues can pass them to her puppies in two ways. The larvae that were dormant in her tissues can migrate through the uterus and placenta and infect the fetal pup. This is in utero transmission. The larvae enter the lungs of the fetal pup. When the pup is born, the pup will cough up the larvae and they will mature in the pup's intestine. This is why so many puppies have roundworms - they are infected before they are born.

Larvae through the milk: Larvae can also enter the bitch's mammary tissues. The puppies can become infected through the milk while nursing. The swallowed larvae mature in the pup's intestine. If the larvae are passed out in the pup's feces before they can mature, they can infect the mother when she licks her pup.
About 4 weeks after a dog eats an infective egg or a puppy with a prenatal infection is born, the adult worm has matured in the animal's intestine and the next generation of eggs is passed.
T. cati
In some ways the life cycle of T. cati is similar to that of T. canis. The infective eggs are swallowed. The larvae hatch and penetrate the stomach wall. From there the larvae migrate through the liver, other tissues, and lungs. Some larvae may encyst in the tissues. Larvae that enter the lungs are coughed up and swallowed. The larvae mature in the stomach and small intestine, and the adult female worms start laying eggs.
Unlike T. canis, in utero infection does not occur with T. cati. However, during the perinatal period dormant larvae in the queen can start to migrate and can be passed from the mammary tissues to the young through the milk.
Mice can serve as intermediate hosts for T. cati in a manner similar to the other roundworms. Cats can also become infected by eating other transport hosts such as earthworms and beetles.
When do they Become Infective?
For all roundworms, the eggs need to remain in the environ-ment for 10 to 30 days before they become infective. Larvae encysted in the host's tissues can remain dormant there for the host's lifetime.
How Do Roundworms Cause Disease in Pets?
In the intestine, roundworms absorb nutrients from what the animal eats, interfere with digestion, and can damage the lining of the intestine. Animals with mild infestations of roundworms may not show any signs of disease. Animals with more severe infestations may be thin, have dull hair coats, and develop a pot-bellied appearance. Some may become anemic and have vomiting, diarrhea, or constipation. A cough may be observed in some animals due to the migration of the larvae through the respiratory system. In young puppies, the migration of the T. canis larvae in the lungs can cause pneumonia.
How are Roundworm Infestations in Pets Diagnosed?
Adult worms are usually 3-4 inches long, although some T. canis roundworms can be up to 7 inches. Adults may be seen in the feces or vomit. The worms are round on cross-section (hence the catchy name) and look a bit like spaghetti. The eggs are identified in the feces. A flotation solution is used to separate the eggs from the rest of the stool, and the resulting sample is examined microscopically.
How are Roundworm Infestations in Pets Treated?
There are many wormers that kill roundworms. Most wormers, however, kill the adult worms but do not affect the migrating or encysted larvae. This is why most manufacturers of wormers advise repeating the worming 2-4 weeks after the first treatment. By that time, most larvae that were migrating during the first treatment have come back to the intestine where they can be killed by the second treatment.
T. canis
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