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What is a parasite?

Parasites are symbiotic organisms living in or on another organism that depend completely on their host for survival. These organisms range from being microscopically small, like the protozoa that cause malaria, to large enough to be plainly seen by humans, like Helminth hookworms. Surprisingly to some, parasitism is actually one of the most common, and successful lifestyles on earth, and over 100 species of human host-specific parasites have been identified. Some parasites coexist benignly and can go unnoticed by their host, and there is even emerging research about some strains that may be beneficial to the host, such as protecting against more serious diseases. But, most parasites are in some way harmful to their host and can cause an array of issues in humans, ranging from diarrhea to infectious diseases and more serious illnesses. While some may associate parasitic diseases with tropical rainforests, they are prevalent around the world, with Chagas disease and toxoplasmosis commonly occurring in the United States. 

Intestinal parasites in humans

Intestinal parasites, particularly helminth worms, are unfortunately a significant cause of disease and death in developing countries. Yet there are also plenty of well-known intestinal parasites that exist in developed countries like the US that contribute to a number of gastrointestinal issues and infections, such as Giardia and pinworms. Intestinal parasitic infections are also frequently found in HIV-infected patients due to severe immunosuppression in the body. Current treatment options include several antibiotics and anti-worm drugs, yet intestinal parasitic infections can sometimes be difficult to treat as they have developed clever mechanisms to evade the immune system in order to live their symbiotic lifestyle. Researchers believe vaccines may be the only way to completely eradicate these infections, and while many have been in development, there currently are none available.

How do you get parasites?

There are several ways parasites can gain access to a host, but they are typically associated with poor hygiene and sanitation and can spread through contaminated water, food, soil, blood, and even sexual contact.  Compromised immune systems, undernutrition, inflammatory conditions, and disturbed gut microbiomes have all been linked with an increased susceptibility to parasitic infections. 

The connection between your microbiome and parasites

Research has shown that there is a clear connection between parasitic infections and the unique composition of a person’s gut microbiome. A balanced gut microbiome works with the immune system to help protect against invaders, and an imbalance in this composition that results in gut dysbiosis can lead to systemic inflammation and certain gastrointestinal illnesses. It may also lead to a weakened defense system, and potentially increase the risk of getting a parasite. From the other end of this relationship, it is believed that certain intestinal parasites may have a long lasting impact on commensal gut microbiota that can result in a persistent perturbed balance of the gut ecosystem. This can lead to downstream consequences that may harm the gut mucosa or lead to enduring gastrointestinal issues. An example of this is seen with IBS, as a large number of cases have been associated with having  an onset after a parasitic infection like Giardiasis and Campylobacter. Researchers have also found that the presence of certain bacteria strains can serve as microbiome biomarkers in predicting a past or present infection.