Re: how do people get worms?

There are two  large groups of "worms" that  can be found in the  intestine of 
animals, including man: roundworms (scientifically  known as nematodes)  and 
flatworms or tapeworms ( known as cestodes). Together, the two  groups are also  
called "helminths". Many  of these helminths need to  spend some time in the 
soil  as part of their life cycle.

Cestodes: eggs are passed out the affected animalīs feces and they  remain in 
the soil  for  many  months. When another animal  eats soil  that contains these 
eggs, the egg will reach the intestine where  it can "hatch" and  and a larval 
(immature)  form of the worm is freed.  Then one of two things can happen:  1). 
the larva  penetrates the gut wall and  goes to  the animalīs tissues and stays 
there as a larval form or 2) the larva  will  mature into  an adult  worm and  
will  produce eggs that   will  be  eliminated with the feces. It  all  depends 
on the species of  cestode.

Roundworms: Depending on the family  to  which  the worm belongs, animals  can  
acquire the infection either  by  eating eggs that are contaminating soil (just 
like cestode eggs) or because the soil  contains infective larvae that  will  
penetrate through  the animalīs skin. These larvae come from eggs that have 
hatched in the soil.

 Usually  worms are very host specific, that  is  worms  that  infect humans  
will only  infect other humans while worms that  infect dogs stick  to  dogs.  
However a few species of worms that infect animals  will occasionally  infect 
humans. One of these dog worms is Toxocara canis which is acquired by  eating 
eggs that are in the soil (the soil  of course is contaminated with  dog feces). 
In the  case of the dog, the egg hatches in the intestine , the  larva 
penetrates the  gut wall, passes to  the blood,  goes to  the lungs where it 
will  mature, then ascends via the bronchii  to  the  trachea, and passes from 
there to  the esophagus and returns this way  to  the intestine where it  
becomes an adult worm. If a human swallows one of these eggs,  it will  hatch , 
the larva  passes the gut wall and into  the bloodstream. In the majority  of 
the cases, the immune system will  kill the larva at this point and nothing 
happens to  the human. However, sometimes the larva escapes the immune system 
and starts migrating and will  produce  a disease known as Visceral  Larva 
Migrans that will  eventually  dissappear because it s a self limiting disease. 
Note. this  larva will  NEVER  become an adult  worm  in humans!
Humans  then, can acquire  dog worms when they handle soil  that is  infected  
with   dog feces  that  contains eggs or larvae. So  it is very  important to  
wash your hands very well as well as all raw vegetables!