ATLANTA-Guatemalan raspberries have been fingered as the delectable vehicle of this spring’s outbreaks of Cyclospora cayetanensis. And while the epidemiologic links to the caviar of fruit accumulated, a cousin berry was exonerated. Despite much scuttlebutt, the strawberry got a clean bill of health.   Yet the disturbing question remains as to why this enteric pathogen, a coccidian parasite, is suddenly emerging. This spring Cyclospora caused such symptoms as recurrent diarrhea, cramps, profound fatigue, and anorexia in more than 900 U.S. and Canadian adults and a few children in 15 states, mainly east of the Rockies. Many cases were lab-confirmed, and 16 patients were hospitalized.   For therapy, the CDC advises 160 mg of oral trimethoprim and 800 mg of sulfamethoxazole twice a day for a week for adults. For kids, it’s 5 mg/kg per dose of TMP plus 25 mg/kg SMX.   The reasons for C. cayetanensis’ seasonal occurrence, its reservoir, and its emergence remain enigmas. So more than 70 CDC and FDA investigators, epidemiologists, microbiologists, state health officers, and fruit-company officials met here to try to learn from this spring’s raspberry-associated outbreaks.   Berries were implicated during Cyclospora outbreaks in Houston in May. First 16 of 26 execs at a luncheon meeting there developed severe diarrhea after eating dessert. Reports conflict on whether they ate strawberries alone or strawberries, raspberries, and blackberries.   Then 10 of 14 people who ate at another Houston restaurant became infected after eating desserts garnished with a strawberry and possibly a raspberry and blackberry.   At first, strawberries were blamed. The $600-million-a-year strawberry industry battled ensuing sharp dips in sales by testing nearly everything-berries in fields and stores, the water for irrigation and washing, the pickers, even the predatory mites used to control strawberry pests. All seemed negative. What’s more, no clusters of Cyclospora were reported in California, where strawberries are produced and consumed in great quantities.   Raspberries turned into the chief suspect. CDC found that raspberries had been served at the 42 Cyclospora events it studied, which had attack rates of 50% to 80%. At 12 events they were the only berries, or they were served separately from other berries. The epidemiologic evidence is “quite compelling,” says CDC’s Dr. Barbara Herwaldt.   Investigators homed in on Guatemalan raspberries. Dr. Robert Ball, the South Carolina health department’s infectious-disease consultant, says its investigation of 38 cases among 64 adults who attended a lunch near Charleston showed that most of the patients had eaten Guatemalan raspberries.   That so few children have been infected by Cyclospora may be because expensive raspberries aren’t served at kids’ parties, says Dr. Ball.   The parasite that CDC field reps sought in farms in parts of Guatemala was identified as Cyclospora in 1993 by Dr. Ynés Ortega’s University of Arizona team in stools of diarrhea patients in Peru. Resembling Cryptosporidium, it’s an 8- to-10 µm wide sphere that often looks mottled red after modified acid-fast staining.   Though there’s no known animal reservoir for C. cayetanensis, other Cyclospora species have been found in rodents, reptiles, and insectivores.   The environmental conditions oocysts of the human species need to fully sporulate and remain infectious are present in the summer, Dr. Ortega notes, which may explain the seasonal occurrence of infections.   But CDC’s Dr. Dolores Katz says the May arrival of Guatemalan raspberries may partly explain the spring occurrence of more than 100 cases in Florida this year.   Though CDC says Cyclospora is “truly emerging,” it doesn’t know why. Dr. Sue Binder suggests it may be due to changes in antibiotic use, food-handling procedures, or because some labs are looking for it harder.   The first recognized U.S. outbreak was at Chicago’s Cook County Hospital in July 1990. Tap water in a physicians’ dormitory was considered the most likely source of the organism that was then designated a blue-green algae-like body. It infected 21, including 14 house staff physicians.   Some of the physicians had myalgia, headaches, vomiting, chills and fever, severe diarrhea, cramps, and anorexia, says Dr. Philip Huang’s CDC team. Five of six physicians said they had cycles of relapses and remissions of up to several weeks.   Three outbreaks in Katmandu, Nepal, the first in 1989, were ascribed to a “coccidia-like body” in “tainted” food and water. The three infected 245 travelers and expatriates seen at the Canadian International Water and Energy Consultants Clinic there. The illness, which lasted an average of 42 days, began with the explosive onset of watery diarrhea, often with fever. Cramps, fatigue, nausea, and anorexia were common.   In a controlled trial, Dr. Charles Hoge’s CIWEC team found Cyclospora infection doesn’t respond to broad-spectrum antibiotics but that it does to TMP plus SMX. He advises seven days of therapy, but New York gastroenterologist Bradley Connor, who worked in the clinic in Nepal, notes that uncontrolled data suggest as little as two or three days may be enough for some persons.   Cyclospora interferes with small-bowel absorption. In the duodenum of infected patients, Dr. Connor found endoscopic evidence of acute and chronic inflammation, disarray of surface epithelium, villus atrophy, and crypt hyperplasia. -Elsie Rosner