Cryptosporidiosis

Cryptosporidiosis is an infectious disease caused by Cryptosporidium parvum, though other Cryptosporidium species occasionally cause it. Symptoms usually appear about 7 days after infection, including abdominal pain, watery diarrhea, vomiting, and fever; symptoms last 6 to 10 days in most patients but may persist for weeks. Patients with immune deficiency can develop severe, life-threatening disease. Since its formal reporting in 1976, the disease has been found widespread and is a common cause of traveler's diarrhea; AIDS patients frequently develop it.

Common Symptoms

Epigastric discomfort; bacterial infection; vitamin deficiency; test; hypokalemia; diarrhea; abdominal pain; nausea; dehydration

Causes and Pathogenesis

(1) Etiology: Cryptosporidium is an obligate intracellular parasitic protozoan, of the class Sporozoa, subclass Coccidia, order Eucoccidiida, suborder Eimeriina, family Cryptosporidiidae, genus Cryptosporidium. The organism is spherical, 2 to 4 μm in diameter. Its life cycle, similar to other Sporozoa, includes asexual schizogony, sexual gametogony, and sporogony, all within the same host. Oocysts are oval, 2 to 6 μm, with smooth walls; mature oocysts contain 4 crescent sporozoites. After ingestion by humans or animals, oocysts excyst in the small intestine; sporozoites escape through wall fissures, attach to the brush border of small intestinal epithelial microvilli, and are enclosed in parasitophorous vacuoles to develop into trophozoites undergoing schizogony, first into 8-nucleus trophozoites then into type I schizonts with 8 merozoites. Upon schizont rupture, merozoites reinvade other epithelial cells, continuing type I schizogony or developing into type II schizonts with only 4 merozoites. Merozoites released from mature type II schizonts differentiate into female (macrogametocytes) and male (microgametocytes), producing gametes that fuse into zygotes developing into oocysts. Oocysts have thin and thick walls; thin-walled oocysts (~20%) are weakly resistant, their sporozoites directly invading new host cells to cause autoinfection. Thick-walled oocysts sporulate within the host with a double wall, highly resistant and infective upon fecal excretion; 10% formalin or 5% ammonia inactivates them, and 30 min at 65°C abolishes infectivity. At least 6 Cryptosporidium species are known; human and mammalian infections are almost always C. parvum, though Zuo Yangxian et al. reported finding both C. parvum and C. muris oocysts in a 33-day-old calf. (2) Pathogenesis: The exact mechanism is unclear; most believe widespread intestinal epithelial damage and villous atrophy cause malabsorption. Some speculate C. parvum produces enterotoxin, finding enterotoxin-like activity in stool supernatants from infected calves. Massive water and electrolyte loss results from small intestinal mucosal damage and intestinal dysfunction; loss of disaccharidases and other mucosal enzymes also contributes to diarrhea. Prostaglandin E2 from infected intestinal epithelial cells stimulates active Cl- secretion and inhibits neutral NaCl absorption. Pathological changes in humans and animals are similar, mainly in the small intestine and colon, sometimes involving the stomach and esophagus. Affected small intestinal villi are atrophied, shortened, or absent; crypt epithelial cells proliferate with deepened crypts; surface epithelial cells are short columnar with irregular nuclei; mononuclear and multinucleated inflammatory cells infiltrate the villus epithelium and lamina propria. Colonic changes resemble those of the small intestine and can normalize after recovery. Gallbladder involvement causes acute and necrotizing cholecystitis with thickened, hardened walls and flattened mucosal ulcers; lung biopsies show active bronchitis and focal interstitial pneumonia.

Treatment

Drug therapy, supportive therapy

Preventive Measures

Daily prevention: Strengthen management of patient and animal feces to prevent food and water contamination; pay attention to personal hygiene. Oocysts resist the environment and common disinfectants; 10% formalin heated to 65 to 70°C for 30 min kills them. Endoscopes and bedpans used by patients should be soaked in 3% clarified bleach solution for 15 min before washing. Patients should be appropriately isolated; pay attention to personal hygiene and protection.

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.