Isosporiasis

Isosporiasis is a parasitic protozoal disease caused by Isospora parasitizing human intestinal mucosal epithelium, causing intestinal mucosal damage. Clinical manifestations include diarrhea, nausea, vomiting, and abdominal tenderness. Two species parasitize humans: Isospora belli and I. natalensis; human infection is mainly I. belli, with I. natalensis very rare.

Common Symptoms

Abdominal discomfort; diarrhea; anorexia; mucoid stool; low fever; nausea

Causes and Pathogenesis

(1) Etiology: I. belli parasitizes epithelial cells of the distal duodenum and proximal jejunum. Patient feces contain oocysts, the infective stage. Oocysts are elongated oval, about (20 to 33) μm × (10 to 19) μm, slightly narrowed at one end like a bottleneck; the cyst wall has two smooth transparent layers, the inner thin and film-like, the outer harder and less permeable. Freshly excreted oocysts usually contain one sporoblast, sometimes two; after excretion, the sporoblast divides into two and secretes walls to form sporocysts about (7 to 9) μm × (12 to 14) μm. Each sporocyst divides twice to form 4 slender crescent sporozoites and a granular residual body; thus each mature oocyst contains 2 sporocysts, each with 4 sporozoites. The life cycle includes schizogony, gametogony, and sporogony; the first two occur in the host. Humans ingest mature-oocyst-contaminated food or water; oocysts rupture in the small intestine, releasing sporozoites that enter epithelial cells and develop into trophozoites. After several schizogonic generations, abundant merozoites are released to invade adjacent cells. About one week later, some merozoites develop into male and female gametocytes and gametes; mating forms zygotes that secrete walls and develop into oocysts, which mature in vivo or after fecal excretion. (2) Pathogenesis: The mechanism is unclear. Invasion and repeated division cause mucosal erosion and impaired absorption; metabolic products may be toxic. Biopsy shows epithelial destruction, villous atrophy; some patients show elongated villi with thickened tips or focal ciliary flattening; the lamina propria has collagen deposition with abundant eosinophils, monocytes, and lymphocytes, and parasites at various developmental stages. In chronic patients, villi are shortened and crypts deepened; besides eosinophils, neutrophils infiltrate the lamina propria.

Treatment

Drug therapy, supportive therapy

Preventive Measures

Daily prevention of isosporiasis: 1. Do not drink cold water or eat raw food or unclean fruits. 2. Wash hands before meals and after using the toilet; trim nails frequently. 3. Cook food thoroughly, especially barbecued or hot pot meals. 4. Teach children to stop finger-sucking and nail-biting. 5. Dress children in closed-crotch underwear at night to prevent anal scratching. 6. Regularly clean toys or wipe with 0.05% iodine solution. 7. Strengthen water source management to avoid contamination.

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.