OxyFile #201

UI  - 91105566
AU  - Perrine D
AU  - Georges P
AU  - Langlais B
TI  - [The efficacy of water ozonation on the inactivation of oocysts
      of Cryptosporidium]
AD  - Laboratoire de parasitologie, UFR des Sciences pharmaceutiques,
AB  - Cryptosporidium oocysts are currently found in surface waters.
      Their incomplete removal by sand filtration and their high
      resistance to chlorinated disinfectants make possible waterborne
      cryptosporidiosis outbreaks after drinking treated water. Because
      ozone is an alternative to chlorine for final drinking water
      disinfection the aim of our study was to determine the ozonation
      conditions able to eliminate the infectivity of oocysts. Feces
      from horses naturally infected by C. parvum were mixed with
      distilled water. The obtained suspension was clarified by passing
      through a graded series of four sieves (pore sizes, 315, 200, 125
      and 63 microns). The clarified suspension was decontaminated by
      adding a 10% sodium hypochlorite solution. After a 10 minute
      contact time at room temperature, the chlorine residual was
      neutralised by the exactly requisite volume of a 0.01 N sodium
      thiosulfate solution. Oocysts in the suspension were purified by
      centrifugation and washing of pellets in distilled water. Oocysts
      in the finally obtained suspension were numerated by counting in
      a Malassez haemocytometer. Ozonated water containing dissolved
      ozone residuals ranging from 0.44 mg/l to 1.09 mg/l were
      inoculated with a number of oocysts ranging from 1.10(6) to
      1.10(8). Contact times with ozone were 4.6 or 8 minutes. After
      destroying the ozone residual by sodium thiosulfate, ozonated
      oocysts were administered by oral route to male Sprague-Dawley
      rats weighing between 180 to 200 g and beforehand
      immunosuppressed by a regimen of 25 mg hydrocortisone acetate
      subcutaneously twice a week, 5 weeks before and 3 weeks after
      Cryptosporidium challenge. Oocyst shedding was daily controlled
      by phase contrast microscoy in smears of fecal suspension mixed
      with carbolfuchsine solution.(ABSTRACT TRUNCATED AT 250 WORDS)
LA  - Fre
SO  - Bull Acad Natl Med 1990 Jun-Jul;174(6):845-50; discussion 850-1