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How Do We Get Rid of Roundworms?

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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.