Balantidium coli, a large, ciliated pathogen, is known to cause balantidiasis in humans. We report a case of B.coli infection in a 37-year-old male with tuberculosis and presenting with fever, anorexia, mild abdominal pain, and episodes of loose stools for 1 week.
Balantidium coli, an uncommon ciliate protozoan parasite, is known to cause balantidiasis. B.coli is found to have a global distribution and is most commonly associated with pigs. Infection in rats, hogs, and monkeys have also been reported. B.coli is said to be the only pathogenic member of the ciliate family Balantidiidae. , Infection in human is generally a rare encounter, acquired by ingestion of food and water contaminated by cysts. Majority of the infections lead to asymptomatic carriers. The trophozoites are capable of attacking the intestinal epithelium, creating ulcers, and causing bloody diarrhea similar to that of amoebic dysentery.  These complications are most commonly seen in malnourished people, individuals in close contact with pigs, cattle, etc. and in poor-hygienic setup.
A 37-year-old male with complaints of loose stools (3-4 episodes per days) was hospitalized. Physical examination of the patient revealed anorexia, fever, mild abdominal pains for 1 week, and he admitted to be chronic alcoholic. The patient was suffering from hypertension for the past 6 months and had a previous history of pulmonary tuberculosis diagnosed a year back, for which he was under antituberculous treatment for 6 months. Due to this, he developed leukopenia along with liver dysfunction related to his treatment. A patient on antitubercular chemotherapy was said to have leukopenia if he has any of the following:  (1) White blood cell (WBC) became <3000/mm 3 during chemotherapy for patients with pretreatment WBC more than 4000/mm 3 or (2) WBC decreased more than 1000/mm 3 in patients with pretreatment WBC between 3000 and 4000/mm 3 . His total leukocyte count was <3000/cc 3 during antituberculous chemotherapy with pretreatment. The ultrasonography report also showed parenchymal liver dysfunction, which was further confirmed by liver function test, where the level of gamma globulin was increased and albumin levels were found to be lower than the normal. The patient's aspartate aminotransferase level was higher than 31 IU/l and alanine aminotransferase higher than 34 IU/l.
Freshly passed loose stool sample from the patient was received in the parasitology section, Department of Microbiology, JIPMER. The stool specimen was watery and contained blood and mucus. Routine stool microscopy was performed immediately after receiving the sample, which showed the presence of motile trophozoites about 65 μm in length and 30 μm in width and cysts of varying sizes ranging from 15 to 30 μm in diameter. The active ciliated trophozoites were identified as B.coli[Figure 1] and [Video 1] and the cysts were identified as cysts of Entamoebacoli[Figure 2]. Trichrome staining (Wheatley modification for the fecal specimen) was performed after wet mount examination for the confirmation of the wet mount findings and better visualization of the internal structures [Figure 3].
Figure 1: Wet mount examination of trophozoites of Balantidium coli
The treating team was immediately informed of the condition and was advised to start the treatment and review his antitubercular therapy as it was the factor responsible for the patient being relatively immunocompromised along with his alcoholic state. Further work up on the patient showed no extraintestinal manifestations such as peritoneal spread or other necrotizing lung infections, or any genitourinary lesions.
The patient was treated with metronidazole 750 mg three times daily for 5 days and the patient improved gradually. The patient slowly improved with therapy after 1 week and his antitubercular therapy was also reviewed. He was discharged after 5 days with advice to change his life style and for follow-up after 1 month.
Balantidiasis is a zoonotic infection associated with pigs, cattle, hogs, rats, etc.  Infection in healthy humans is rare and is mostly prevalent in immunocompromised patients as it is said to have low virulence. B.coli has a world-wide distribution and astoundingly is the only pathogenic member of the family Balantidiidae.  Moreover, the prevalence of the organism was reported to be around 0.02-1% that may vary according to the geographical location. Areas of high prevalence of B. coli include regions of The Latin America, Iran, Papua New Guinea, the Philippines, and some countries of the Middle East.  Due to factors such as poor sanitation, climatic variation, and cultural practices, B.coli is restricted to tropical and subtropical countries. Cases of B.coli from cattle,  pigs,  rats, etc., have also been previously reported from India. To our knowledge, Previously, very few cases of human infection with B.coli has been reported in India. , Umesh et al., demonstrated case of urinary balantidiasis reported from urine of a 29-year-old woman in Mumbai, India, but this report failed to demonstrate B.coli in stool examination that was required to confirm the hypothesis of extraintestinal infection of B.coli in humans. In a study by Kaur etal., in 2002, parasitic causes of intestinal diarrhea in children in New Delhi were determined by direct wet mount examination.  Out of the 127 cases examined, 59 cases were positive for intestinal protozoans and helminths. B.coli was found to be a cause of diarrhea in 2.4% of the cases. Our report illustrates the case of intestinal balantidiasis in a patient from India, who was on antitubercular chemotherapy, where motile B.coli trophozoites have been demonstrated from loose stools collected from the patient.
In our demonstrated case, the patient had no history of contact with any animals that could be a probable reservoir for B.coli. Therefore, the possible mode of transmission could have been intake of contaminated food or water.
B. coli, the largest protozoan, is the only ciliate capable of infecting human, especially the immunocompromised individuals and, people living in poor sanitary set-ups. The population of immunocompromised individuals is also increasing at an alarming rate, which could pose a global threat by this ciliated pathogen. Hence, it is important to look for B. coli along with other agents commonly associated with dysentery. This will aid in better understanding of the parasite, its distribution, and epidemiology.