Balantidiasis

Balantidiasis is a common parasitic protozoal disease caused by Balantidium coli parasitizing the human colon. Clinical manifestations include abdominal pain, diarrhea, mucoid bloody purulent stool, tenesmus, and fever; chronic persistent patients have alternating constipation and diarrhea or periodic diarrhea. The disease is confirmed in 22 provinces, municipalities, and autonomous regions of China.

Common Symptoms

Dysentery; borborygmus; intestinal perforation; diarrhea; abdominal distension; tenesmus; abdominal pain; constipation; fatigue; nausea

Causes and Pathogenesis

(1) Etiology: B. coli was first discovered by Malmsten in 1857 in the feces of two acute dysentery patients; Leuckart found it in pig large intestine in 1861; Stein assigned it to the genus Balantidium in 1862. Classification: Protozoa, Ciliophora, Litostomatea, Vestibulata, Trichostomatida, Trichostomatina, Balantidium, B. coli. 1. Morphology: B. coli is the only ciliate parasitizing humans and the largest human protozoan. Its life cycle includes trophozoite and cyst forms. (1) Trophozoite: round or oval, colorless transparent or grayish-green, about (30 to 200) μm × (25 to 120) μm, ventrally flattened and dorsally convex, with ridge-like elevations and groove-like depressions running from front to back; cilia extend from grooves to the exterior, their beating propelling the organism. The surface has a pellicle over transparent ectoplasm and inner endoplasm; the anterior end is slightly tapered with a cytostome food vacuole; undigested material exits through a small anal pore at the posterior. Trophozoites have electron-dense bodies, two contractile vacuoles for osmotic regulation, polysaccharide granules, food vacuoles, and mitochondria at the periphery. (2) Cyst: round or oval, about 40 to 60 μm, thick transparent wall, pale yellow or greenish; active trophozoites may be seen in fresh cysts. Cysts resist the external environment, surviving 2 weeks to 2 months at room temperature, dying only after 3 h in direct sunlight; they also resist chemicals, surviving 4 h in 10% formalin. 2. Life cycle: The cyst is the infective stage; humans ingest cyst-contaminated food or water. In the digestive tract, digestive fluids excyst the organism into trophozoites in the large intestine, feeding on food residue, bowel wall cells, and bacteria. Trophozoites reproduce mainly by transverse binary fission and also by budding. Some trophozoites, influenced by stool formation and water loss, round up and secrete a cyst wall to form cysts excreted in feces. Pigs form many cysts in the intestinal lumen, but humans form few; during encystment the nucleus does not divide, so one cyst excysts into one trophozoite. (2) Pathogenesis: Most believe B. coli is pathogenic; when humans have chronic disease, malnutrition, or intestinal dysfunction, the organism invades, multiplies, and causes disease. It requires time to adapt to the intestinal flora, then multiplies rapidly. Intestinal bacteria such as Klebsiella, S. aureus, Enterobacter, and other parasites promote growth and lesion development. Invasion requires mechanical ciliary movement and hyaluronidase secretion; hyaluronidase dissolves intercellular matrix. Glycogenase and hemolysin have also been isolated from heavily infected pig feces. These factors cause colonic mucosal inflammation, necrosis, and ulcers, with secondary bacterial infection aggravating lesions. Pathology resembles E. histolytica intestinal disease, mainly in the cecum and sigmoid colon, occasionally the terminal ileum and appendix; rare cases involve mesenteric lymph nodes, liver, lung, pleura, and urogenital tract. The mucosa is congested and edematous with petechial hemorrhages; early lesions show crater-like ulcers a few mm in diameter that enlarge and merge into flask-shaped ulcers with small openings and irregular margins; unlike amebic ulcers, these have slightly larger openings and short thick necks. Ulcer bases are usually in the submucosa, with abundant trophozoites in surrounding mucosa; inter-ulcer mucosa may be normal, edematous, or hemorrhagic, with lymphocyte and eosinophil infiltration.

Treatment

Drug therapy, supportive therapy

Preventive Measures

Health education: This disease is orally transmitted, so emphasize dietary and personal hygiene. Strengthen human and pig fecal management, prevent pig feces from contaminating food and water, and actively treat infected pigs. B. coli cysts resist the external environment, surviving 2 weeks at room temperature, 2 to 3 months in moist environments, and 4 h in 10% formalin, so hygienic disposal of patient and pig feces is critical for controlling the epidemic.

Department to Visit

It is recommended to visit the Gastroenterology department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.