Case 3 報告人 : 胡鴻祥 時間 : 指導老師 : 盧章智主任

Previously healthy 32-year-old woman, diarrhea, alternating with constipation, abdominal discomfort, vomiting, anorexia, intense fatigue, myalgia, and other "flu-like" symptoms for several weeks,went to her internist for treatment No traveling history but remarked that her symptoms had developed a few days after she attended a June wedding in Florida several other guests at the wedding had developed similar symptoms

Routine tests for enteric pathogens were Routine tests for enteric pathogens were reported as being negative Modified acid-fast-stained smear revealed spherical structures approximately 8 to 10 μm in diameter, showing a range of intensity from colorless to dark red The spherical structures showed auto- fluorescence when viewed using a UV microscope.

Q1.Which intestinal protozoan parasite might be causing this patient's symptoms? Explain your answer based on the results of laboratory tests.

Ans: 1.Cyclospora cayetanensis 2. 因為在 modified acid-fast stain 中卵囊會 被染成紅色而且在 uv microscope 下會自 己發光, 再加上 oocyst 大小 8-10μm

Q2:List two other protozoan parasites which might be confused with this parasite. How may these three parasites be distinguished from each other?

Ans: 1. Cryptosporidium Parvum 2. Isopora bellui

Cyclospora cayetanensis 的 oocyst 通常很 少存在, 若存在的話, 會 8-10μm, 且有些會 含 granules or have a bubbly appearance(wrinkled cellphone), auto- fluorescence when viewed using a UV microscope.

Cryptosporidium Parvum 不會有 auto- fluorescence when viewed using a UV microscope 而他的 oocyst 大小約 4-5μm

Isopora bellui 的 oocyst 會 auto- fluorescence when viewed using a UV microscope 且形狀為 oblong 而且較其他 兩者為大

Q3:How does this patient's history correlate with this diagnosis?

Ans:1.Diarrhea 2.Abdominal discomfort, vomiting, anorexia, intense fatigue, myalgia, and other "flu-like" symptoms 3.Several other guests at the wedding had developed similar symptom 4.The routine tests for enteric pathogens were reported as being negative

Q4:Where have outbreaks of this infection occurred?

Ans: Since 1990, at least 11 foodborne outbreaks of cyclosporiasis, affecting approximately 3600 persons, have been documented in the United States and Canada.

Q5:Does this parasite cause more serious illness in immunocompromised individuals?

Ans: In an immunocompromised host, onset is more insidious, and the condition becomes chronic

Q6:Should the patient be treated? If so, how?

Ans: This disease can be self-limited and we can give supportive treatmrnt first but if the symptom became severe,we can prescribe Trimethoprim - sulfamethoxazole(Immunocompetent host: 160 mg TMP/800 mg SMZ PO bid for 7 d Immunocompromised host: 160 mg TMP/800 mg SMZ PO qid for 10 d, followed by prophylaxis with 160 mg TMP/800 mg SMZ 3 times/wk )

Q7:How can this infection be controlled and prevented?

Ans: 1. Practice good hygiene. 2. Avoid water that might be contaminated. 3. Avoid food that might be contaminated. 4. Take extra care when traveling.

When freshly passed in stools, the oocyst is not infective (thus, direct fecal-oral transmission cannot occur; this differentiates Cyclospora from another important coccidian parasite, Cryptosporidium). In the environment, sporulation occurs after days or weeks at temperatures between 22°C to 32°C, resulting in division of the sporont into two sporocysts, each containing two elongate sporozoites. Fresh produce and water can serve as vehicles for transmission and the sporulated oocysts are ingested (in contaminated food or water). The oocysts excyst in the gastrointestinal tract, freeing the sporozoites which invade the epithelial cells of the small intestine. Inside the cells they undergo asexual multiplication and sexual development to mature into oocysts, which will be shed in stools. The potential mechanisms of contamination of food and water are still under investigation.

Thanks for your attention

參考資料 : 1.Medical parasitology,7 th 2.The 10-minute Diagnosis Manual 3.Home page:Division of parasitic disease 4.Home page:E-medicine