Organ Damage

• Organ damage is only a long-term effect in cases of severe roundworm infection. With a heavy roundworm burden in your lower intestine, roundworms can lay eggs and travel to different parts of your body, damaging different organs. If this is the case, surgery will be required.
  
  

Weight Loss

• Because roundworms can lay eggs in your intestine, it can take a while to rid yourself of all of them. Roundworms will often devour food you put into your system before it is properly digested. This prevents you from getting all of the nutrients from the food, and can cause weight loss.
  
  

Vomiting and Diarrhea

• If roundworms find their way into your system, your body's first response will be to reject them. This will be done through vomiting and diarrhea. Your body may continue to do this in an effort to expel all roundworms and the eggs that they have laid.
  
  

Stomach Pain

• It shouldn't come as too much of a surprise that having roundworms living in your lower intestine can cause some abdominal pain. As long as they are in there living off food you put into your system, it is common to feel stomach pain until they are gone.