Susceptibility of five strains of <i>Cryptosporidium parvum</i> oocysts to UV light

Abstract

Previous evaluations of the effect of ultraviolet (UV) light on <i>Cryptosporidium parvum</i> oocysts have been limited to a single strain-the Iowa strain. This study investigated the response of five strains of <i>C. parvum</i> to UV. A collimated beam apparatus was used to apply controlled doses of monochromatic (254 nm) UV to oocysts of the Iowa, Moredun, Texas A&M, Maine, and Glasgow strains. Irradiation was measured using a calibrated radiometer and sensor. Inactivation was quantified through animal infectivity by inoculation of cohorts of CD-1 neonatal mice with UV-treated and untreated control oocysts of each strain followed by examination of intestinal sections for infection using hemotoxylin and eosin staining. A UV light dose of 10 mJ/cm² achieved at least 4-log₁₀ inactivation of all strains evaluated. All five strains of <i>C. parvum</i> were shown to be highly susceptible to low levels of UV light.