McDonald's restaurants in the mid-west have pulled their salads after being linked to a large outbreak of Cyclospora. This comes after last month's outbreak linked to D
el Monte's trays of sliced vegetables.
The reference below lists some of the difficulties of this parasite...one is that it may be more resistant to sanitizers and the other is the ability to attach to produce.
So basically, the parasite gets into water used for irrigation. The source being fecal contamination from someone who became ill. Once on the crops, it may not be easy to get rid of it.
Not a lot is know about cyclospora, one of the issues being is that humans are the only known reservoir. This makes studying using animal models impossible.
CLINICAL MICROBIOLOGY REVIEWS,
Jan. 2010, p. 218–234 Vol. 23, No. 1
0893-8512/10/$12.00 doi:10.1128/CMR.00026-09
Copyright © 2010, American Society for Microbiology.
Update on Cyclospora cayetanensis, a Food-Borne and Waterborne Parasite
Yne´s R. Ortega* and Roxana Sanchez
University of Georgia, Center for Food Safety, Griffin, Georgia 30223-1797
"Individuals with Cyclospora infection excrete unsporulated oocysts in their feces (Fig. 1). These oocysts require 7 to 15 days to sporulate under ideal conditions (23 to 27°C) and presumably become infectious to a susceptible host. When food or water contaminated with infectious oocysts is ingested
by a susceptible host, the oocysts excyst and sporozoites are released to infect epithelial cells of the duodenum and jejunum."
"Cyclospora is highly resistant to disinfectants commonly used in food and water processing. This resistance may also be enhanced by the apparent higher binding affinities of the parasite for certain fresh produce. In the case of raspberries, which have been implicated in several outbreaks, the topography of the fruit is characterized by fine hair-like projections that facilitate the entrapment of the “sticky” Cyclospora oocysts. The microenvironment of the berry provides a favorable environment for parasite retention on the fruit. The stickiness of Cyclospora oocysts seems to be stronger than that of Cryptosporidium or Giardia oocysts. The adhesins responsible for this strong attachment to produce are unknown."
NY Times
https://www.nytimes.com/2018/07/13/us/mcdonalds-salads-illness-cyclospora-nyt.html
McDonald’s Salads Linked to Intestinal Parasite Outbreak in Midwest
By Matthew Haag
July 13, 2018