balantidium coli ( b. coli ) is the only ciliated protozoan that is known to infect humans . balantidiasis is a zoonotic disease occurring in humans via the feco - oral route from the normal host , the pig . however , it may be found in rare extraintestinal sites such as liver , lung , and genitourinary tract . b. coli can become an opportunistic parasite in immunosuppressed hosts living in urban environments , where pigs are not a factor in infection . in this case report , b. coli was incidentally found in the urine of a patient having chronic obstructive pulmonary disease ( copd ) who was on steroids for a long time . the patient had no history of diarrhea , other gastrointestinal ( gi ) symptoms , previous urinary tract infection , or urethral discharge . he was also taking bone broth / soup . as a routine work - up urine sample was received . , several oval - to - oblong ciliated parasites that were approximately 75  50 m in size were seen swimming rapidly across the slide [ figure 1a ] . two to three pus cells per high power field and few candidal pseudohyphae and spores were also present . cytosmears were prepared from the urine sediment to identify the morphology . both hematoxylin and eosin ( h&e ) and giemsa staining were done . in h&e stained smears [ figure 1b ] , cytoplasmic food vacuoles and macronucleoli were seen and faint impression of cilia was noted . in giemsa stained smears [ figure 1c and d ] , the parasite was identified and the body was covered with short and delicate cilia that were all of uniform length . to exclude contamination , we examined two repeat urine samples that were collected under sterile condition . based on the morphology and swimming pattern , a diagnosis of urinary balantidiasis was made . oval - to - oblong ciliated trophozoites containing cytoplasmic food vacuoles ( thin arrows ) . ( b ) ( h&e , 40 ) trophozoites of b. coli in urine showing cytoplasmic food vacuoles and faint impression of cilia ( thick arrow ) . ( c and d ) ( giemsa , 40 ) trophozoite of b. coli in urine covered with short and delicate uniform length cilia ( thin arrows ) complete hemogram and biochemistry profiles were within normal limits . serology for human immunodeficiency virus ( hiv ) and hepatitis b surface antigen ( hbsag ) were negative . his fecal samples and bronchoalveolar lavage fluid samples were negative for trophozoites / cysts of b. coli . the patient was very sick at the time of admission , later he was intubated and kept on ventilator . malmsten was the first to recognize b. coli in two humans with dysentery in the year 1857 . the pig is the common reservoir of infection but the parasite is harmless to the host as the parasite thrives mainly on starchy food that is abundant in pig 's intestine . the scarcity of starchy food in the human bowel explains the rarity of balantidial infection in man . cyst is the infective stage , when ingested liberates trophozoites in the large intestine , which may remain in the bowel or may invade submucosal coat of the bowel . the trophozoites and cysts of b. coli are shed in feces and if the cysts , in particular , contaminate drinking water or food , the infection can be spread to other pigs or humans . the trophozoite measures 30 - 150 m in length and 25 - 120 m in width ; the cyst , which may be spherical or slightly ovoid , measures 40 - 60 m in diameter . the mouth ( oral apparatus ) is located at the tapering anterior end , and the cytopyge ( anus ) is located at the rounded posterior end . balantidium causes no serious disease of the gi tract ; however , in conditions such as malnutrition , alcoholism , or a compromised immune system , it can lead to disease . in our case , the source of infection is not clear . the patient had no history of contact with pigs , but he had history of intake of bone broth . third hypothetical possibility is the ascending infection from the urine pot that was washed with plain contaminated water . b. coli should be differentiated from trichomonas vaginalis ( t. vaginalis ) , entamoeba histolytica ( e. histolytica ) , ciliocytophthoria phenomenon . in urine it can be differentiated easily from b. coli by its morphology and motility . in stool , it moves on the slide surface by means of an anterior ectoplasmic pseudopod and is smaller ( around 25 m ) in diameter . in addition , mature cysts are smaller and quadrinucleate as compared to binucleate b. coli cysts . in case of samples taken from anatomic locales that are lined by ciliated columnar epithelium ciliocytophthoria are much smaller ( average 12  10 m ) anucleated cells with cilia along one edge . many cases of b. coli infection in the stool sample have been reported worldwide . however , in urine there were only a few case reports available . we have found only two case reports of isolated urinary balantidiasis from india while the rest showed coinfection with t. vaginalis . umesh reported a case of a 29-year - old woman with cystitis due to b. coli . reported urinary balantidiasis in a 68-year - old farmer having diabetes and chronic kidney disease . to the best of our knowledge , this is the third case report of isolated urinary balantidiasis from india . rapid spiraling motility and cytosmears stained with giemsa and h&e satins are very useful in morphological identification . effective sanitation , use of clean water , and consumption of properly cooked food are probably the most effective ways to prevent balantidiasis in humans .
balantidiasis is a rare zoonotic disease in humans . 
 balantidium coli is the causative ciliated protozoan . 
 we present a case of urinary balantidiasis in a patient having chronic obstructive pulmonary disease ( copd ) who was on steroids for a long time . 
 he has no symptoms of bowel or urinary involvement . 
 we are reporting this case because of its rarity in human urine and also for future references .