Modern medicine has struggled mightily over the last 100 years to help humans rid their bodies of parasites. Now some researchers believe we may have gone too far. Without parasites our immune systems may sometimes attack our own tissues. That’s why a Massachusetts company is trying to develop a treatment for autoimmune diseases like Crohn’s or rheumatoid arthritis that involves purified pig parasites. More than 200 subjects will be recruited to take either a placebo or porcine whipworm eggs. This parasite does not survive well in humans so the treatment does not lead to permanent infection or illness. Researchers hope that exposure to the parasite will distract the immune system so that it no longer damages joints or other sensitive tissue.