Both dogs and puppies can be infested with a common intestinal parasite called the roundworm, but the infection tends to have a more severe effect on puppies. The roundworms, or ascarids, of the dog are Toxocara canis and Toxocara leonina. Toxocara canis is the most common species that affects canines; almost all puppies are born already infected by their mother. Other possible modes of roundworm infection include either ingestion of infective eggs from the environment or prey that harbor the parasite.
These long, white, tubular adult worms can reach lengths of eight to 12 centimeters long. The roundworms live in the small intestine, moving against and feeding upon the flow of food being digested by the animal. When multiple worms are present, they are capable of causing inflammation and distention of the bowel. As a result, canines with roundworms can experience colic and will not absorb needed nutrients from the food they eat. Diarrhea is a common symptom of an infection, but more serious problems can occur. Canines with roundworms often have a potbellied appearance and an unhealthy coat.
Roundworms pass large numbers of microscopic, round eggs in the feces of the infected dogs. If these eggs are spread in an environment conducive to infestation, they will mature and become ready to infect the next animal. Humans, most commonly children, can become afflicted by the Toxocara canis larval stage by accidentally ingesting soil or feces containing roundworm eggs. In people, the larvae can migrate through the eyes and other important organs, leading to vision impairment or other serious illnesses.
