Parasites

From a medical standpoint, parasites describe a number of multi-cellular organisms that are able to survive on or within the human body, but have side effects that are harmful to human health. Technically speaking, a parasite has two characteristics:

• Part of its life cycle must be spent within a host body; and
• It requires sustenance from the host in order to survive during this period.

However, the term 'parasite' is usually used to refer to any organism that meets either of these characteristics.

Parasites do not include single-celled organisms, such as bacteria, amoeba or viruses that can cause disease. It also excludes multi-cellular creatures that normally inhabit the human body and rarely have harmful side effects, like dust mites.

Parasitic diseases

Many serious diseases are caused by parasites. Two of the most common are malaria, which is transmitted largely by mosquito bites, and tapeworm, which is transmitted by eating parasitic cysts in undercooked food, typically fish and pork. It is very rare for parasitic diseases to be transferred from person to person.

Parasitic diseases are rare in North America and Europe, although they are very common in the developing world. Most Western patients who develop parasitic infections were exposed while traveling. As such, it is usually vital for a medical history to contain a patient's full travel itinerary for the past several years. However, there are a few parasitic diseases that are endemic to North America.

Appearances

Patients on House often suffer from parasitic infections. A few episodes where the disease was caused by a parasite are Fidelity, Failure to Communicate, Euphoria (Part 2), and Hunting.

Parasitism at Wikipedia