Toxocara

Toxocara, the most frequently encountered roundworm in puppies, and indeed almost universal in very young puppies, has been implicated in a rare specific type of eye disease in children.

 Roundworms that are ingested by a species other than their normal host may encyst and settle in almost any part of the body, but are known to invade the eye.

These cysts have been known to cause blindness. Such an accident is extremely rare but, of course, a tragedy for the child and his or her parents if it happens.