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United States Department of Agriculture

Agricultural Research Service

Title: Infectivity of Cryptosporidium Parvum Oocysts Stored in Water at Environmental Temperatures

Authors
item Fayer, Ronald
item Trout, James
item Jenkins, Mark

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 1998
Publication Date: N/A

Interpretive Summary: Occysts are the stage of the parasite Cryptosporidium parvum that initiate infection in humans and animals. The ability of oocysts to survive a wide range of environmental temperatures determines whether they are present and available to initiate infections. The present study has provided for the first time detailed information on the survival of infective oocysts at temperatures ranging from -10C(14F) to 35C(95F) at intervals up to 6 mo. From this study it is apparent that oocysts can survive and remain highly infectious at temperatures from 5-20C (41-68F) but lose viability quickly as temperatures become progressively higher or lower. This information is important to epidemiologists predicting duration of outbreaks and for scientists developing methods to reduce oocyst infectivity.

Technical Abstract: Oocysts of Cryptosporidium parvum obtained from calves were cleaned of fecal debris by density gradient centrifugation and suspended in deionized water in microcentrifuge tubes. The tubes were placed in circulating water baths at temperatures of -10, -5, 0, 5, 10, 15, 20, 25, 30, or 35 C and two tubes were removed from each water bath 1, 2, 4, 8, 12, 16, 20, and 24 wk later. Oocysts from one tube were administered to 2 liters of neonatal BALB/c mice. The second tube was assayed for amylopectin concentration. Oocysts held at -10C were infectious up to 1 week of storage and those held at -5C were infectious up to 8 wk of storage. Oocysts held at 0, 5, 10, 15, and 20C were still infectious after 24 wk of storage. Those held at 25 and 30C each produced infections up to 12 wk after storage. Those held at 35C produced light infections after 2 wk of storage. Amylpectin concentration decreased as either length of storage time or temperature increased. These findings provide a guide for estimating the potential duration of oocyst infectivity within a wide range of environmental temperatures and demonstrates the relationship between amylopectin concentration and infectivity.

Last Modified: 4/18/2014