Published Date: 2002-11-24 23:50:00
Subject: PRO/EDR> Amebic meningoencephalitis - USA (Arizona) (05)
Archive Number: 20021124.5886
AMEBIC MENINGOENCEPHALITIS - USA (ARIZONA) (05)
A ProMED-mail post
ProMED-mail, a program of the
International Society for Infectious Diseases
Date: 23 Nov 2002
From: ProMED-mail <email@example.com>
Source: Maricopa County Department of Public Health [edited]
More Water Samples Come Back Positive for _Naegleria fowleri_
Officials from Maricopa County Public Health and Environmental Services'
Departments and Arizona Departments of Environmental Quality and Health
Services announced today additional water sample results from the Centers
for Disease Control and Prevention in Atlanta.
As was reported earlier this week, officials were waiting for results on 2
water samples as well as a refrigerator filter. CDC confirmed today that
one of the samples taken from Rose Valley Water's Tank 3 and the filter
taken from the refrigerator of the grandparents of one of the boys who died
in October were both positive for _Naegleria fowleri_. The remaining water
sample from Rose Valley was negative for the ameba in question.
Rose Valley's system was taken offline 3 Nov 2002, so residents have been
receiving only safe water since that time. Before the system will be able
to provide water to residents, it must meet all County requirements,
including disinfection of all water system components and installations of
a permanent mechanical chlorination system.
The refrigerator filter was taken for testing on 21 Oct 2002, before Rose
Valley Water began chlorination. Rose Valley customers have already been
advised to change their refrigerator filters after the switch to Peoria
water. Those who did not are advised to do so now.
"Again, all the data show that a residual level of 0.5 parts per million of
chlorine will kill this organism in a chlorinated system," said Dr.
Jonathan Weisbuch, Director of Maricopa County Department of Public Health.
"We have no reason to doubt this. I want to stress again, no new amebic
meningitis cases have been reported since the chlorination process began."
"We understand that this is frustrating information," said Maricopa County
Supervisor Max Wilson, "We are frustrated too and pledge to continue to
work with federal officials to search for answers."
As county, state and federal officials continue to search for additional
answers, unchlorinated water systems are asked to test often for total
coliforms as indicator bacteria. If a test comes back positive, systems in
Maricopa County are asked to contact Maricopa County Environmental Services.
A County hotline has been established at 602-506-6616 that offers emergency
numbers to answer questions from residents. A recorded message also is
available at 602-506-1040. For questions about health issues call
602-506-6900 during normal business hours.
Residents are reminded to not swim in warm, stagnant water, ponds, or
unchlorinated pools. Also, keep pools, jacuzzis, and spas properly cleaned
Sample Results from Centers for Disease Control and Prevention:
Sample # / Location / Result
1/ City of Peoria Well Westbrook / Positive
2/ Rose Valley Tank One / Negative
3/ Rose Valley Tank Two / Negative
4/ Rose Valley Tank Three / Positive
5/ Rose Valley Well Two / Negative
6/ Rose Valley Well Three / Negative
7/ Refrigerator Filter / Positive
Jonathan B. Weisbuch, M.D., M.P.H.
Director, Maricopa County Department of Public Health
1845 E. Roosevelt St.Phoenix, AZ 85006
For more information, contact:
Doug Hauth at (602) 506-4926
Pager: (602) 205-3002
[Free-living amebae are ubiquitous in fresh water at temperatures above
25C. The ameba has 3 life stages: the growing trophozoite form, the motile
biflagellate form, and the dormant cyst form. The 2 active forms are easily
inactivated by chlorination, but the cyst needs a concentration of 4
mg/liter for at least 10 minutes to be inactivated. Experience shows that
the chlorine level needs to be maintained throughout the water systems to
control growth of the ameba. _Naegleria fowleri_ is neurotropic, with
infection seen almost exclusively in the central nervous system. This is
why the route of infection was thought to be directly though the olfactory
cells of the nose. It is highly unlikely that infection can be acquired by
drinking water containing free-living amebae. -Mod.EP]