A parasite is an organism that lives on or in another organism (its host) and gets its food from or at the expense of its host. Parasites can cause disease in their hosts. A few parasites live in other animals but most parasites live inside the bodies of humans.
Most people think of parasites as dirty, nasty organisms that cause diseases. However, there are many different types of parasites, and not all of them are harmful to humans. Some parasitic relationships are actually beneficial to both the parasite and its host. For example, certain algae live on the shells of turtles and help to keep the turtles clean. This relationship is called commensalism, which is a type of symbiotic relationship where one organism benefits while the other is neither harmed nor helped.
Other parasitic relationships are not so benign. Many parasites actually cause harm to their hosts by stealing food or damaging tissues. These harmful relationships are called parasitism. Some common examples of human parasites include tapeworms, fleas, lice, and ticks.
Most human parasites enter our bodies through contaminated food or water or by direct contact with an infected person or animal. Once inside our bodies, they can travel to different organs where they may live for years without causing any symptoms (asymptomatic infections). In some cases though, these infections can cause serious illness (symptomatic infections). The severity of symptoms depends on various factors such as the type of parasite involved, how many parasites are present, how long they have been present in the body, and a person’s overall health status.
Some common symptoms associated with parasitic infections include: diarrhea; constipation; abdominal pain; nausea; vomiting; fatigue; weight loss; anemia; allergies; and difficulty breathing. In some cases, these symptoms may be severe enough to require hospitalization. If you experience any of these symptoms after returning from travel outside of the United States or if you have had contact with someone who has been infected with a parasite, it is important to see your healthcare provider right away so that appropriate testing and treatment can be done