Seasonal temperature fluctuations induces rapid inactivation of Cryptosporidium parvum

Xunde Li, Edward R Atwill, Lissa A. Dunbar, Ted Jones, Jimmy Hook, Kenneth W. Tate

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


This study measured the inactivation rate of bovine genotype A Cryptosporidium parvum oocysts attributable to diurnal oscillations of ambient temperature and solar radiation typical of California rangelands and dairies from spring through autumn. We first measured the relationship between air temperature and the internal temperature of bovine feces exposed to sunlight on commercial operations throughout California. Once maximum air temperature exceeded the mid 20 °C, diurnal thermal regimes of bovine fecal material exhibited peaks of over 40, 50, 60, and 70 °C. These diurnal thermal regimes were emulated using a thermocycler, with oocysts suspended in distilled water orfecal-water mix. Using oral inoculations of 105 C. parvu oocysts per neonatal Balb/c mouse (>1000-fold the ID50), no infections were observed using 1 to 5-day cycles of these thermal regimes. Loss of infectivity induced by these thermal regimes was primarily due to partial or complete in vitro excystation during the first 24-h diurnal cycle and secondarily to thermal inactivation of the remaining intact or partial oocysts. These results suggest that as ambient conditions generate internal fecal temperatures ≥40 °C via conduction, radiation, and convection, rapid environmental inactivation occurs at a rate of ≥3.27 log reduction d -1 for C. parvum oocysts deposited in the feces of cattle.

Original languageEnglish (US)
Pages (from-to)4484-4489
Number of pages6
JournalEnvironmental Science and Technology
Issue number12
StatePublished - Jun 15 2005

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Science(all)
  • Environmental Chemistry


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