There are four main worms types that invade digestive tract of the dog;
tapeworms, whipworms, hookworms and roundworms. Digestive tract
worms can trigger symptoms ranging from no symptoms, to
dogs that show symptoms such as weight loss and diarrhea. All four
digestive tract worms can be spread from one dog to another. There is
also a risk of hookworms and roundworm being transmitted to humans.

RoundWorm pictured to the left  is the most common of the intestinal worms in dogs. Roundworms are round, up to seven inches long, and white to pale brown in color (they look a little like spaghetti noodles). They hang out in
the intestines, soaking up nutrients from the dog's diet.

seen commonly- especially in puppies

larvae can infect humans ,

complex life cycle


Worms can infect dogs a number of ways: puppies can be infected with larvae while still in their mother's uterus (a very common route of infection for puppies). Puppies can ingest larvae through their mother's milk. Ingesting eggs (which hatch into larvae after being eaten). Eating rodents who have been infected with the larvae


Signs and Symptoms of Roundworms: Roundworms can produce any of the following symptoms, though symptoms may only appear with heavy infections:-puppies will sometime vomit up roundworms or pass them in their feces-failure to gain weight, or weight loss-dull hair coat-pot-bellied appearance-diarrhea-sometimes coughing due to the larval migration through the lungs. Rarely, very heavy infections can lead to blockage of the intestines, which will make a puppy very ill (vomiting, lethargy).

This picture was taken from DogBreedInfo.com a great site filled with tons of information. .