Efficiancy of UV light in Inactivating Cryptosporidium parvum Oocysts

1
Efficiancy of UV light in Inactivating
Cryptosporidium parvum Oocysts

• Morita S, Namikoshi A, Hirata T, Oguma K,
• Katayama H, Ohgaki S, Motoyama N, Fujiwara M.

Applied Environmental Microbiology 2002
Nov68(11)5387-93
2
What is UV light?
3
(No Transcript)
4
UV
5
(No Transcript)
6
Background
Cryptosporidium parvum (zoonotic parasite)
Diarrhea (not bloody)
Very infective
Infects all ages
Immunity acuired
Resistant oocysts
No good cure
Transmitable via other mammals
Dangerous for immunocompromised mammals
Can be dangerous in combination with other
diseases
7
Background
Problem
Cryptosporidium parvum common in surface
water/rivers
C. parvum resistant to normal water treatment
(chlorine)
Mineral water must be pathogen free
8
Background
Solution UV water treatment
No/little hazard
Easy to maintain
Good results with virus and bacteria
Inactivates virus and bacteria (DNA)
9
Background
Problems with UV water treatment
DNA repair
Photoreactivation (enzyme lesion repair by near
UV-light)
Dark Repair (repair in absence of light)
Previous Studies In Vitro excystation Vital
Dye Methods
No inactivation of C. parvum
10
Background
11
Materials Methods
Treatment

SCID
C. parvum oocysts
Purified C. parvum oocysts
12
Materials Methods
Summary Experimental Conditions
Table 1
UV dose (mWs/cm2) 0 1.2 1.68 1.80 1.82
2.40 40 80 120 160 240
- -
- - - - -
T (50C) T (100C) T (200C) T (300C)
- -
- - - - -
-

- -
- - - - -
Animal Infection
In Vitro Excystation
13
Materials Methods
UV treatment and Recovery
Table 2
200C and 0.10 mW/cm2
UV dose (mWs/cm2) 0.5 1.0 1.5 Evaluation
FL dose (mWs/cm2) 150 X
X 180 X 300 X
X 360 X 540 X 720 X Stor
age (h) 4 X 12 X X
X 24 X
X X Not Treated X
X X
Animal Infection (AI) Endonuclease-sensitive
site asssay (ESS)
14
Materials Methods
Animal Infection
Increasing infection dose (oocysts) (n5-8
mice/group)
Relatice Risk of infection
15
Materials Methods
In Vitro Excystation
Excystation rate (V)
IO Intact Oocysts (prior excystation) S free
Sporocysts PO Partially excysted Oocysts EO
Empty Oocysts
V?V?
Survival Rate (Sr)
V? Excysting rate (UV irradiated) V?
Excysting rate (control)
16
Results
Excystation Metod
Oocysts
Preincubation Hanks balanced salt solution, 5 min
Oocysts
Woodmansee DB 1987
Sodium hyochlorite
Taurocholic acid solutions, 7 pH
Incubation 370C, 60 min
17
Results
Figure 1 UV dose vs. Infectivity (mice)
½ dose needed for infectivity reduction
according to litterature (16 mWs/cm2 recommended
for 2 log10 reduction)
1 log10 reduction
2 log10 reduction
4 log10 reduction
18
Results
Figure 2 UV dose vs. Survival (oocysts)
230 mWs/cm2 dose needed for 2 log10 reduction in
viability
...dose 200 time higher than reduction in
infectivity (1 mWs/cm2)
Contact time (CT) for Chlorine 18 times higher
for viability reduction
Contact time (CT) for Ozone 3 times higher for
viability reduction
Conlusion oocyst excyst but do not infect with
tested doses
19
Results
Figure 3 UV dose vs. Relative Infectivity (mice)
Dose increase for 2 log10 reduction in
infectivity was 7 at 100C decrease
UV as disinfectant farily stable at normal
temperatures (in contrast to eg. Ozone)
5 0C ? 10 0C ? 30 0C
Water temperature
2 log10 reduction (mWs/cm2) 1.20
1.07 1.02
20
Results
Figure 4 UV dose vs. Relative Infectivity (mice)
UV Dose for 2 log10 reduction in infectivity
was 1.15 mWs/cm2 ...for 0.048 mW/cm2 1.20
mWs/cm2 ...for 0.12 mW/cm2 1.34 mWs/cm2 ...for
0.60 mW/cm2
8 UV dose increase ? 10 fold increase in
intensity
Conclusion figure 34 UV irradiation can
inactivate C. parvum without regard to water
temperature and intensity
0.048 mW/cm2 ? 0.12 mW/cm2 ? 0.60 mW/cm2
21
Results
Figure 5 Fluorescent light dose vs. ESS (DNA)
Increased UV dose induced pyrimidine dimers
repaired with increased exposure time to
fluorescent light
30-50 reduction in ESS at 750 mWs/cm2 dose
0.5 mWs/cm2 ? 1.0 mWs/cm2
22
Results
Figure 6 Dark Storage vs. ESS (DNA)
UV induced pyrimidine dimers were repaired with
dark storage periods
Dark storage recovery was slower than fluorecent
light exposure
60 ESS repair in 24 hours
Conclusion figure 56 Both fluorecent light
exposure and dark storage can repair UV
irradiated damage to C. parvum oocyst
0.5 mWs/cm2 ? 1.0 mWs/cm2
23
Results
Infectivity of fluorecent irradiated reactived
oocysts
UV irradiation with... 0.50 mWs/cm2 led to 0.98
log10 reduction in infectivity 1.00 mWs/cm2 led
to 2.00 log10 reduction in infectivity 1.50
mWs/cm2 led to 3.15 log10 reduction in infectivity
...but no change in infectivity when reactivated
with fluorecent irradiatiation
24
Results
Infectivity of dark storage reactived oocysts
No change in infectivity when reactivated in dark
storage for 4 and 24 hours
Conclusion UV irradiation of oocysts does not
recover infectivity though DNA damage is
documented
I) Dark repair occurs parralel with fluorecent
light reactivation
II) Remains of DNA damage still affect infectivity
III) Unknow lesions on DNA inhibits infectivity
25
Thank you for listening