Composition of the bacterial flora accompanying Balantidium coli in th
e rectum content of pigs affected by acute (Group 1) and symptom-free
(Group 2) balantidiosis was studied. The course of balantidiosis was f
ound to be dependent on composition of the bacterial flora. B. coli vi
rulence towards the host's tissues may be a secondary effect of the ch
anges in biological, chemical, and physical conditions of the parasite
's biotope.