Roundworms is the common name for several species of nematodes or ascarids. The name roundworms is derived from the tubular shape of the worms. Several species can infect dogs, but the species Toxocara canis can cause significant problems in humans as well as the species found in raccoons, Baylisascaris procyonis.
Dogs can become infested with roundworms by ingesting the eggs in the environment deposited in fecal matter, through the placenta while in the womb, or in the milk when nursing. The larvae then migrate through the liver and lungs of the puppy where they enter the air way, are coughed up, and then swallowed. They then settle in the intestinal tract absorbing the nutrients that should be meant for your puppy. A lot of damage is done when they are migrating through the body.
In humans, accidental ingestion of roundworm eggs can also migrate internally causing a syndrome know as visceral larva migrans. Signs of VLM can be characterized by hepatomegaly (liver enlargement), lung disease, and increase in eosinophils from allergic reactions. The larva can also migrate through the nervous system causing neurologic disease. In some children, the larvae can migrate to the eyes causing inflammation and may result in blindness.
Contamination of the environment by raccoons has caused significant problems in some regions. The migration of the raccoon roundworms also cause more significant disease problems. Accidental ingestion has also occurred when children may have chewed on firewood, or when playing in contaminated sandboxes or playgrounds. The best defense for this is to be sure children do not chew on objects that may have been contaminated and to wash their hands after playing outside.
Because of the potential infection of people, puppies and dogs should be de-wormed every 2 weeks starting at 2 weeks of age and then once a month as maintenance when 4 months old. The newer heartworm and flea preventions also include a dewormer to control hookworms and roundworms. Dogs infested with roundworms can pass thousands of eggs in their feces. These eggs can survive in the environment and be infective for several years.
For more information, visit Pets and Parasites
Roundworms -Ascariasis http://www.cdc.gov/parasites/ascariasis/index.html