The Giant Protozoan Parasite: An Overview of Balantidiasis

Balantidiasis, caused by Balantidium coli, the largest protozoan and the only ciliate infecting humans, is an emerging zoonotic disease of medical and veterinary importance. Pigs are the natural hosts, while humans acquire infection through ingestion of food or water contaminated with infective cysts. Most cases remain asymptomatic, but severe infections may result in ulcerative colitis, fulminant dysentery, hemorrhage, and rarely, systemic involvement. Pathogenesis is linked to hyaluronidase secretion and mechanical invasion of colonic epithelium, producing amoebic-like ulcers. Diagnosis relies on detection of trophozoites and cysts in stool or tissue samples. Although globally distributed, prevalence is low (<1%) and mainly associated with pig-rearing communities in tropical regions. Tetracyclines are the treatment of choice, with alternative drugs including nitroimidazoles and paromomycin. Prevention relies on sanitation, pig management, and improved hygiene. Greater research is needed on epidemiology, transmission dynamics, diagnostic tools, and One Health approaches to control this neglected protozoan infection.