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United States Department of Agriculture

Agricultural Research Service


item Thurston Enriquez, Jeanette
item Watt, Pamela - UNIV OF ARIZONA
item Dowd, Scot - UNIV OF ARIZONA
item Enriquez, Ricardo - UNIV OF ARIZONA
item Pepper, Ian - UNIV OF ARIZONA
item Gerba, Charles - UNIV OF ARIZONA

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2001
Publication Date: N/A

Interpretive Summary: Human pathogenic protozoan parasites, Giardia cysts, Cryptosporidium oocysts and microsporidia, were detected in waters collected in Central America (Panama, Costa Rica and Mexico) and the United States. These waters are used for irrigation of vegetable crops that require little processing before consumption. Examples of crops irrigated with the sampled waters include lettuce, tomatoes, cilantro, peppers, celery, onions, carrots and potatoes. The majority of samples, 22 out of 25, were collected in Central America. For these samples, higher concentrations of Giardia cysts and Cryptosporidium oocysts were detected compared to samples collected in the United States. The nucleic acid of human pathogenic microsporidia species were detected in at least one sampling location in Mexico, Costa Rica and the United States. Since infection can occur by ingestion of a small number of Giardia cysts and Cryptosporidium oocysts, their presence in irrigation waters used for the production of crops traditionally consumed raw suggests that there may be an increased risk of infection to consumers who come in contact with, or consume these products.

Technical Abstract: The occurrence of human pathogenic parasites was investigated in irrigation waters used for food crops traditionally eaten raw. Polymerase chain reaction was used to detect human pathogenic microsporidia in irrigation waters from the United States and several Central American countries. In addition, the occurrence of both Cryptosporidium oocysts and Giardia cysts was determined via immunofluorescent techniques. Twenty-eight percent of the irrigation water samples tested positive for microsporidia, 60% positive for Giardia cysts and 36% positive for Cryptosporidium oocysts. The average concentrations in samples from Central America containing Giardia cysts and Cryptosporidium oocysts was 559 cysts and 227 oocysts per 100 L. In samples from the U.S., an average of 25 Giardia cysts and < 19 (average detection limit) Cryptosporidium oocysts per 100 L were detected. Two of the samples, which were positive for microsporidia, were sequenced and subsequent database homology comparisons allowed the presumptive identification of two human pathogenic species; Encephalitozoon intestinalis (94% homology) and Pleistophora species (89% homology). The presence of human pathogenic parasites in irrigation waters used for the production of crops traditionally consumed raw suggests that there may be a risk of infection to consumers who come in contact with or consume these products.

Last Modified: 12/1/2015
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