It's like something out of the movie Aliens, but it's science, not fiction. Luckily, only a very small number of people get these symptoms, and you can take steps to reduce the risks for your pet and for you. Toxocara canis is one of the most common intestinal parasites of dogs. Almost every puppy is born with this parasite. Kittens, unlike puppies, are not infected before birth but rather obtain the infection through their mother's milk.
Puppies get the infection before birth through the placenta and after birth via the mother's milk.
Even if the mother has been dewormed, larvae encapsulated in her liver, skeletal muscle, and kidneys are not killed. Late in the pregnancy larvae move to the mammary glands, and by the fifth day of nursing they infect the milk. Eggs are passed in the puppy's feces about 3 weeks after birth. Two weeks later the egg of Toxcara canis may be capable of infecting humans. Infected puppies typically have a rough coat, pot bellies, bad breath, general failure to thrive, and sometimes vomiting and diarrhea.