First of all, it is important to define ulcerative colitis. This is is a chronic affection of the large intestine also known as the colon. In fact, it is a form of what is called inflammatory bowel diseases that also include the well-known Crohn’s disease. Ulcerative colitis causes the presence of inflammation and ulcers in the colon and is associated with many other gastrointestinal symptoms , such as bloody diarrhoea and abdominal pain. The real causes of ulcerative colitis are still unknown, but some explanatory hypotheses have been proposed. Nevertheless, none of the current hypotheses include the involvement of some parasitic diseases as a trigger for ulcerative colitis, which means that parasites have not been involved so far in the development of this disease. However, it is not sufficient to rule out this possibility completely, as the real causes are still unknown. Only the future will tells us.
It is interesting to note that there is actually a lot of confusion in the formal diagnosis of inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, and also of the related irritable bowel syndrome, another intestinal symptom-based diagnosis. The boundaries between the different criteria to effectively diagnose and distinguish these diseases do not seem to be very clear at the moment. Furthermore, as parasitic infections can lead to a myriad of gastrointestinal symptoms similar to the ones observed in people affected by these diseases, it is quite likely that parasitic infections be misdiagnose as one of these diseases. This assumption is also reinforced by the fact that parasitic diseases are not the first things to come to mind when patients in developed countries suffered from gastrointestinal symptoms.
It is noteworthy that helminths seem to offer a kind of protection against the inflammatory bowel diseases rather than to cause them. As a matter of fact, the lower number of cases of infection with helminths reported in developed countries seems to be one of the causes of the rise of diseases like ulcerative colitis and Crohn’s disease, as helminth infections have a protective effect on this type of diseases. Consequently, a new controversial type of therapy called helminthic therapy consisting of the inoculation of some helminth’s eggs in the body is under investigation and is now promising to control inflammatory autoimmune diseases including ulcerative colitis and Crohn’s disease.
Source: Merck Manual