Although cyclospora is associated with subtropical and tropical climates, the hardy parasite can survive periods of freezing temperatures. Killing cyclospora with cold temperatures requires that it be frozen for 24 to 48 hours at temperatures between 24.8˚ F and -4˚F or lower, according to the Guide for Foodborne Pathogens.
At freezing temperatures above 25˚ F, cyclospora can survive. That was was the case in June 2000, when an outbreak in Philadelphia was linked to raspberries in a wedding cake.
After illnesses were reported and stool specimens from wedding guests collected and tested positive for the parasite, epidemiological testing confirmed the presence of cyclospora in the cake. Raspberries imported from Guatemala were the only produce ingredient used to make the wedding cake. The catering company received four shipments of fresh raspberries June 1–3 and served some of them fresh at events on June 3 and 4. None of the people who ate these berries became sick.
The remaining berries were frozen for 1–4 days. The catering company thawed two to three pints of leftover, unwashed raspberries, crushed them into pieces, and folded into the butter cream filling used in the cake. The cake was then frozen for another 4–5 days until it was thawed, served and eaten at the wedding reception June 10.
Cyclospora is spread when the feces of an infected human contaminate food that is eaten by others. Once it is shed in the stools, the oocyst, or immature form of the parasite, has to mature for a time in the environment before it becomes infective. So, unlike foodborne bacteria such as E.coli, Salmonella or Listeria, cyclospora, does not spread directly from person to person.
The catering companies guests who ate the fresh berries on June 3 or 4 and did not get sick may have ingested oocysts that were not yet mature or the batch of berries may not have been contaminated. The cake was likely frozen at a temperature above 25˚ F, allowing the the oocysts to survive and mature to the infective stage.
The imported berries were from the same Guatemalan farm as those associated with an outbreak in Georgia. That outbreak sickened guests at a bridal brunch in May 2000.
Symptoms of a cyclospora infection, called cyclosporiasis, can last up to two months and include diarrhea, that can be explosive, abdominal cramping, bloating, gas, nausea, fatigue, loss of appetite and weight loss. Vomiting, body aches, low-grade fever are also possible. Cyclosporiasis is normally treated with the antibiotic combination trimethoprim-sulfamethoxazole. If untreated, relapse is possible.
