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Roundworms, known as ascarids or “spool worms,” are thick-bodied, whitish-to-cream-colored worms that can inhabit the small intestine of dogs and cats.

This is one of the most common intestinal parasites affecting dogs and cats and young puppies and kittens. In fact, research has demonstrated that over 95 percent of all neonates are born with roundworms.

Adult worms exist unattached within the intestinal lumen and can grow up to 8 inches in length. If present in sufficient numbers, adult roundworms can cause prominent malnutrition and gastroenteritis.

In some severe instances, rupture of an intestine jam-packed with roundworms has been known to happen. Immature roundworms can cause problems, too, since they might migrate throughout the lungs, liver, and other tissues of the body before settling down as adults within the intestines.

Unlike tapeworms, roundworms do not require an intermediate host for their transmission. Each female worm sheds thousands of eggs into the environment by the way of feces. These eggs, which are covered by a thick shell, are very resistant and might remain viable in an environment for years prior to being consumed by an unsuspecting pet.

After consumption of a roundworm egg, it is possible for the hatched larvae to develop into adults without ever leaving the intestine. However, this is the exception rather than the rule. Usually the larvae penetrate the bowel wall and migrate to the liver and the lungs, maturing and growing along the way.

Once inside the lungs, they can enter the airways, then be coughed up and swallowed again, allowing them to finish their development into adults within the intestines. Alternatively, from the lungs, these larvae can enter the bloodstream and circulate throughout the body.

In female dogs and cats, these larvae might settle down and become dormant within the mammary tissue until such time as lactation begins. In this way, newborns can ingest roundworm larvae through their mother’s milk. But this isn’t the only reason for the high incidence of roundworms in neonatal puppies and kittens.

They can also be exposed to the circulating roundworm larvae via the umbilical cord while they are still in the womb, and actually be born with active infestations! The clinical signs seen with a roundworm infestation depend on the age of the pet affected, the stage of maturity that the worms are in, and their location within the body.

As a general rule, the younger the pet, the more severe the signs tend to be. In fact, some older dogs and cats can actually develop a resistance to these parasites. If adult worms are within the intestines, signs often include stomach pain with a prominent “bloated” appearance to the abdomen, vomiting, and diarrhea. In many instances, actual adult worms might be revealed within the vomitus or stool.

Ruptured bowels and intestinal obstructions can result if not treated promptly. Because of the migration through the lungs, coughing, breathing difficulties, and other signs of pneumonia might be present. In severe cases, seizures and other nervous system problems can occur. Veterinarians can diagnose roundworms by using a microscope to look for eggs in a stool sample.

Clinical signs and the pet’s history are helpful in those cases where eggs might be absent from such a sample. There are a wide variety of deworming drugs effective at removing roundworms from the intestines. You can buy relatively inexpensive dewormers at supermarkets and pet supply stores.

Be sure, however, to consult a veterinarian before using one of these to be certain that it contains the correct ingredients for your pet’s particular problem. Repeat deworming should be performed 3 weeks later to ensure that any migrating larvae that reached the intestines since the first deworming are killed.

Young puppies and kittens suffering from roundworm-induced pneumonia require intensive veterinary supportive care to prevent life-threatening complications from arising. Most will recover with such care.

All puppies and kittens should be dewormed for these parasites, even if parasite eggs are not seen on an initial stool exam. These dewormings should commence at 3 weeks of age, and should be repeated at 6 and 9 weeks of age. Periodic stool exams are warranted to confirm a puppy or kitten’s negative status.

Good sanitation procedures will help prevent reinfections and spread to other dogs and cats. Realize, however, that once roundworms enter an environment, they are almost impossible to totally eliminate because of the hardy nature of the eggs.

As a result, annual stool checks by a veterinarian are indicated to ensure that pets remain parasite-free. Visceral larva migrans, a human disease syndrome caused by migrating roundworm larvae, does pose a serious public health threat.

As a result, good personal hygiene after handling pets plus routine stool exams and treatments are a must to minimize the threat from this disease. Most heartworm preventive medications on the market today also help prevent roundworm infestations if given on a regular basis.

In those instances where environmental contamination is difficult to control, administering such a preventive year-round is one way to keep a pet free of these parasites.