Trichomonas infection. Light micrograph of a cervical smear containing normal squamous cells from the cervix (pink/blue) and Trichomonas vaginalis parasites (smaller blue patches). The black dots are the nuclei of white blood cells. T. vaginalis is a flagellate protozoan that is usually, but not always, sexually transmitted. The initial acute infection causes vaginitis and cervicitis associated with a frothy discharge. Cervical smear tests are routinely carried out to check for abnormalities in the cells of the cervix, which might indicate the onset of cancer. Magnification: x1150 when printed 10cm wide.