Closed Case Friday: Drive-thru Salads & Diarrhea

Earlier this week, we gave you a hypothetical patient with the following case:

This week's hypothetical patient has been experiencing watery diarrhea with frequent (often explosive) bowel movements, bloating, fatigue, and nausea over the last week and a half. The patient's physician did a physical examination and order an analysis of our patient's stool. The physician informed the patient that there has been a local outbreak of people exhibiting similar symptoms and that they would be testing the patient's stool for a specific pathogen. Like many other patients with similar symptoms, this patient reported eating a salad from a local fast-food chain a few weeks ago. The lab found relatively large oocysts that demonstrated a blue autofluorescence under ultraviolet epifluorescence microscopy. These results confirmed the presence of the suspected pathogen. The physician prescribed trimethoprim-sulfamethoxazole and told the patient to rest and get plenty of fluids.

Today, we reveal that our hypothetical patient was diagnosed as having: 

Cyclosporiasis

To be fair, this patient's symptoms could have indicated the presence of a wide range of pathogenic organisms. However, the indication of an outbreak from contaminated salad, the description of the laboratory results, and the prescribed drug point more specifically to the presence of a coccidian parasite known as Cyclospora cayetanensis. This parasite is often the center of outbreaks involving contaminated fruits and vegetables, including an actual outbreak among patients who had consumed salads from a fast-food chain in the Midwest during July of this year. (You can read about this and other 2018 outbreaks of C. cayetanensis here.)

Typical wet mount preparations of stool samples can reveal the presence of this parasite, but is more reliably diagnosed with the use of staining/fluorescence examinations. Depending upon resources and outbreak severity, other diagnostic tests, such as immunodiagnostics or PCR, can also be used to confirm cases of cyclosporiasis.

Symptoms of this disease typically present after about a week post-infection. Over this period of time, the parasites are developing into their infective forms and impacting the intestines and these organs' abilities to form and pass fecal material. There is little water reclamation occurring in the large intestines of infected individuals, leading to watery stools and frequent bowel movements. For this reason, patients need to increase their intake of fluids to prevent dehydration and rest to allow antibiotics and the immune system time to clear the body of infection.

You can read more about domestic cases of Cyclosporiasis that occurred in 2018 here.

Thanks for joining us for this week's Mystery Case and we hope to see you next week!