Published Date: 2001-05-04 23:50:00
Subject: PRO/AH/EDR> Cryptosporidiosis - UK (Northern Ireland) (02)
Archive Number: 20010504.0862
CRYPTOSPORIDIOSIS - UK (NORTHERN IRELAND) (02)
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See Also
Cryptosporidiosis - UK (Northern Ireland) 20010421.07802000
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Cryptosporidiosis - UK (Northern Ireland) 20000524.0823
Cryptosporidiosis - UK (Northern Ireland) (02) 20000904.1508
Cryptosporidiosis - UK (Scotland) 20000605.0903
1999
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Cryptosporidiosis - UK (NW England) 19990514.0788
1998
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Cryptosporidiosis - UK 19980510.0927
Cryptosporidiosis - UK (04) 19980520.0963
1995
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Cryptosporidium - UK (press report) 19950816.0690
Cryptosporidium - UK: update (3) 19950903.0789
Date: 3 May 2001
From: <promed@promed.org>
Source: Eurosurveillance Weekly Issue 18 [edited
<http://www.eurosurv.org/update>
Outbreak of cryptosporidiosis in Northern Ireland
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During the first week of April [2001, 12 cases of cryptosporidiosis were
reported to the Eastern Health and Social Services Board in Northern
Ireland, and 21 more the following week. These weekly totals were
considerably greater than would be expected in April. Most of the cases
lived in an urban area, and few had been abroad or had had contact with
animals.
By mapping postcodes of laboratory confirmed cases against water supply
zones, authorities found that the attack rate among those served by the
Dunore water treatment works only was 2.8/10 000 population compared with
0.14/10 000 in those who receive water from other sources. Similar
investigations in the adjacent Northern Board into a rise in reported cases
of cryptosporidiosis over the same time noted similar attack rates in those
receiving water from this water treatment works. By 25 Apr 2001 there were
a total of 110 confirmed cases within the Dunore supply area.
The Dunore water treatment works uses slow sand filtration and supplies
some 100 000 properties in the Greater Belfast and south Antrim areas,
which includes parts of the population of the Eastern and Northern Boards.
Cryptosporidiosis has not been associated with this water treatment works
before.
Daily monitoring of continuous water samples in part of this supply area
began on 24 Feb 2001: oocyst counts varied between 0 and 0.62/10 L up to 21
Apr 2001. Small peaks were noted over a 4-day period at the end of February
(max 0.22 oocysts/10 L), over a 7-day period in mid-March (max 0.41
oocysts/10 L) and 29 March (0.62 oocysts/10 L). Allowing for an average
7-day incubation period, these would approximately correspond to the peaks
noted in the epidemic curve.
Of the positive fecal specimens examined so far, 25 have been
_Cryptosporidium parvum_ genotype 1 and 4 _C. parvum_ genotype 2. All the
genotype 1 specimens have been identified from patients living in the
affected supply area of both health boards.
A detailed investigation has shown that a blocked drain at the water
treatment works may have allowed the entry of a small quantity of untreated
water into the filtration system. Remedial action at the water treatment
works was completed on 22 Apr 2001.
The outbreak control team managing the incident reminded the public,
hospitals, and general practitioners of previous expert advice that all
water, from whatever source, that might be consumed by people with impaired
immunity should be brought to the boil and allowed to cool before use.
Reported by Brian Smyth
Public Health Laboratory Service
Communicable Disease Surveillance Centre
Northern Ireland, Belfast
<bsmyth@phls.org.uk>
--
ProMED-mail
<promed@promed.org>
[This is the second year in a row that there has been a cryptosporidiosis
outbreak in Northern Ireland associated with public water supply systems.
Contamination of drinking water with surface water is a classical route of
transmission. The work leading up to the identification of the source of
the contamination is a nice piece of classical epidemiological
investigation. - Mods.MPP/EP
..............mpp/ep/pg/ds
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