Environmental inactivation of Cryptosporidium oocysts in catchment soils.
OBJECTIVE
To generate field-relevant inactivation rates for Cryptosporidium oocysts in soil that may serve as parameter values in models to predict the terrestrial fate and transport of oocysts in catchments.


RESULTS
The inactivation of Cryptosporidium oocysts in closed soil microcosms over time was monitored using fluorescence in situ hybridization (FISH) as an estimate of oocyst 'viability'. Inactivation rates for Cryptosporidium in two soils were determined under a range of temperature, moisture and biotic status regimes. Temperature and soil type emerged as significantly influential factors (P < 0.05) for Cryptosporidium inactivation. In particular, temperatures as high as 35 degrees C may result in enhanced inactivation.


CONCLUSIONS
When modelling the fate of Cryptosporidium oocysts in catchment soils, the use of inactivation rates that are appropriate for the specific catchment climate and soil types is essential. FISH was considered cost-effective and appropriate for determining oocyst inactivation rates in soil.


CONCLUSIONS
Previous models for predicting the fate of pathogens in catchments have either made nonvalidated assumptions regarding inactivation of Cryptosporidium in the terrestrial environment or have not considered it at all. Field-relevant inactivation data are presented, with significant implications for the management of catchments in warm temperate and tropical environments.
Davies
C M
CM
Centre for Water and Waste Technology, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, Australia. c.davies@unsw.edu.au
Altavilla
N
N
Krogh
M
M
Ferguson
C M
CM
Deere
D A
DA
Ashbolt
N J
NJ
D000818:Animals; D003458:Cryptosporidium; D004784:Environmental Monitoring / Q000379:methods; D017404:In Situ Hybridization, Fluorescence; D033661:Oocysts; D012987:Soil; D012988:Soil Microbiology; D013696:Temperature; D013997:Time Factors; D018508:Water Purification
D012987:Soil