There are some type of blastocystis, which can cause synptomatic infection along with other types of infection. However, normally these parasite simply remains in the gut and do not affect in general.
There is as such no treatment for blastocystosis, and the infection usually gets clear on its own. However, if signs and symptoms do not improve within a time period, a doctor may recommend some medicine. Research in this area is still going on, but researchers have not reached to a conclusion of exact cause of Blastocytosis.