The Changing Epidemiology of Cryptosporidiosis in North West England
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Epidemiol. Infect. (2005), 133, 785–793. f 2005 Cambridge University Press doi:10.1017/S0950268805004772 Printed in the United Kingdom The changing epidemiology of cryptosporidiosis in North West England W. SOPWITH 1*, K. OSBORN 2,R.CHALMERS3 AND M. REGAN 1 1 Health Protection Agency, North West Regional Office, Liverpool, UK 2 United Utilities, Warrington, UK 3 Cryptosporidium Reference Unit, National Public Health Service for Wales, Swansea, UK (Accepted 24 May 2005) SUMMARY Between 1996 and 2000, rates of cryptosporidiosis in North West England were significantly higher than overall in England and Wales, particularly during the first half of each year. In addition, during the second quarter of each year in this period, up to 40% of all cases recorded in England and Wales were from the North West Region. In 2001, cryptosporidiosis dramatically decreased throughout the United Kingdom and the springtime excess of cases formerly seen in the North West was no longer apparent. This changed epidemiology was due to a decline in cases of Cryptosporidium parvum (formerly genotype 2), associated with zoonotic transmission. Although the initial loss of a spring peak of infection corresponded with the outbreak of foot-and-mouth disease throughout the United Kingdom, its continued absence relates to major structural changes in the North West public water supply. This study highlights the far-reaching public health benefit of local working relationships in addressing re-occurring disease issues. INTRODUCTION In the past 10 years, there have been several springtime clusters of cryptosporidiosis in the United Transmission of the protozoan parasite Crypto- Kingdom relating to various sources of drinking sporidium to humans has been documented by direct water [4–7]. In one outbreak in North West England, faecal–oral contact and through drinking water, oocysts of Cryptosporidium were isolated from recreational water and contaminated food and the Thirlmere reservoir, which supplied the public drink- potential also exists for mechanical transmission via ing water distribution system, and from sheep grazing transport hosts such as flies or even birds [1, 2]. In a nearby [8], while faecal contamination of water study of waterborne outbreaks of infectious intes- supplies by livestock has been implicated in other tinal disease in England and Wales, Cryptosporidium outbreaks [9, 10]. A case-control study in North was implicated in all outbreaks associated with Cumbria also identified drinking unboiled tap water public water supplies and public swimming pools [3]. from a public water supply as a significant risk factor These outbreaks largely involved unboiled chlori- for non-outbreak cases of cryptosporidiosis [11]. nated tap water or chlorinated swimming-pool water Human cases of cryptosporidiosis in England and and demonstrate that Cryptosporidium oocysts can Wales are seasonal with peaks both in spring and survive some water purification processes. autumn [12]. Similar seasonal patterns have been reported in Spain [13] and New Zealand [14]. Crypto- * Author for correspondence: Dr W. Sopwith, Health Protection sporidiosis in England and Wales is also associated Agency NW, DBH House, 105 Boundary St, Liverpool L5 9YJ, with foreign travel and this is likely to have a seasonal UK. (Email: [email protected]) component [15]. Downloaded from https://www.cambridge.org/core. IP address: 170.106.202.8, on 24 Sep 2021 at 21:51:44, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0950268805004772 https://doi.org/10.1017/S0950268805004772 . https://www.cambridge.org/core/terms , subject to the Cambridge Core terms of use, available at available use, of terms Core Cambridge the to subject , 21:51:44 at 2021 Sep 24 on , 170.106.202.8 address: IP . https://www.cambridge.org/core from Downloaded of cases in England and Wales reported from the North West, by quarter (secondary pronounced, more became Wales and England Fig. 1. neto in infection all of seasonality of Cryptosporidium Laboratory reports of cryptosporidiosis in England and Wales and in North West England between 1997 and 2004, by 4-week period. The line signifies the p pattern bimodal modest the 2000, and 1996 Between No. of cases 1000 1200 1400 1600 Epidemiology 200 400 600 800 0 1–4 RESULTS 5–8 9–12 13–16 199717–20 1998 1999 2000 21–24 25–28 [26]. lation 29–32 33–36 legis- Government to according enumeration and 37–40 41–44 45–48 filtration of procedure standard a by supplies water 49–52 oyt eeietfidi public in identified were oocysts 1–4 Cryptosporidium 5–8 9–12 13–16 [25]. oocysts 17–20 ngigNtoa olcinof Collection National on-going 21–24 Cryptosporidium 25–28 29–32 the of part as [24] methods published to according 33–36 37–40 41–44 Swansea in Unit Reference Cryptosporidium UK the 45–48 sruieygntpdby genotyped routinely is of lates 49–52 Cryptosporidium 1–4 5–8 9–12 iso- reported of half about of subset A London. in 13–16 17–20 Centre Surveillance Disease Communicable national 21–24 25–28 29–32 the at de-duplicated are received Data (CoSurv). 33–36 37–40 Wales and England in laboratories microbiology 41–44 45–48 sltsi hospital in isolates of reporting 49–52 Cryptosporidium 1–4 5–8 electronic the through Office) Regional West (North Specimen date(week no.) 9–12 13–16 17–20 Service Epidemiology Regional Agency Protection 21–24 25–28 Health the by obtained were presented Data 29–32 33–36 37–40 x 41–44 METHODS -axis not shown). 45–48 49–52 1–4 5–8 9–12 13–16 [23]. humans to seasonality bimodal similar a shows 200117–20 2002 2003 2004 21–24 25–28 cattle in infection and spring in peak strong a shows 29–32 33–36 sheep in Cryptosporidiosis [22]. spring in nating 37–40 41–44 predomi- with infection, of year of time 45–48 parvum C. , Total cases England and Wales; 49–52 sltsi uasdpne pnthe upon depended humans in isolates 1–4 parvum C. 5–8 9–12 to of proportion the ) and ( .hominis C. 13–16 parvum C. 17–20 21–24 2 genotype were sheep) and (cows livestock from 25–28 29–32 33–36 samples all that showed England from isolates of 37–40 41–44 study large A [21]. cases individual for infection of 45–48 49–52 source likely the indicate to used be can Genotyping 1–4 5–8 n nml n anan h name the maintains and animals and [20]. 9–12 parvum C. 13–16 17–20 humans from isolated been has 2 genotype whereas 21–24 25–28 encasfida eaaespecies, a separate as classified been , 29–32 hominis C. 33–36 37–40 now have and humans to limited exclusively almost 41–44 % 45–48 eoye1ioae are isolates 1 . Genotype of re-evaluation 49–52 parvum C. , North West cases. 1–4 5–8 a taxonomic prompting 19], [18, this supported 9–12 13–16 peto oeua yigfor typing molecular of opment has 17–20 Cryptosporidium 21–24 25–28 devel- subsequent and [17] person to person other 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% iso eepooe n18,oezooi n the and zoonotic one 1984, in proposed were mission Proportion of cases in England & Wales trans- of cycles Two [1]. mammals domestic and roportion reported from North West England wild of range wide a in described been has parasite trbtdto attributed 1] This [16]. rpoprdu parvum Cryptosporidium otcsso ua rpoprdoi aebeen have cryptosporidiosis human of cases Most 8 .Spihadothers and Sopwith 786 W. Cryptosporidiosis in North West England 787 14·00 12·00 10·00 8·00 6·00 4·00 2·00 Crude rate of disease/100 000 0·00 ababababababababa 1996 1997 1998 1999 2000 2001 2002 2003 2004 Fig. 2. Crude rates of cryptosporidiosis in England and Wales (%) compared with North West England (&), 1996–2004 by 6-month period (a=weeks 1–26; b=weeks 27–52). Rates are cases per 100 000 population. 200 180 160 140 120 100 80 No. of cases 60 40 20 0 JFMAMJJASONDJ FMAMJ JASONDJ FMAMJ JASONDJ FMAMJ JASOND 2000 2001 2002 2003 Fig. 3. Number of cases of cryptosporidiosis due to Cryptosporidium parvum (––––) and Cryptosporidium hominis (........) amongst isolates tested from North West England between 2000 and 2003, by month. peaking in 2000 with 610 and 938 cases occurring all cases reported in England and Wales during the in two distinct 4-week periods around early May second quarter of each year were from the North and late September respectively (Fig. 1). The seasonal West Region (Fig. 1). This increase also diminished pattern changed significantly in 2001 with the dimin- in 2001 and although there has been some seasonal ishing of the late spring peak, which was not seen variation in subsequent years, it has been less pro- in England and Wales subsequently between 2002 and nounced (Fig. 1). 2004 (Fig. 1). In the North West Region of England, Analysis revealed that increased rates of infection a similar early May peak of infection was seen between were seen in the North West Region compared to 1997 and 2000 but the corresponding September England and Wales between 1996 and 2000 (Fig. 2). peaks were less pronounced than in England and In addition, rates of infection in the North West Wales as a whole (Fig. 1). As in England and Wales, Region were consistently higher in the first 6 months the expected May peak of infection was not seen in of the year than in the second where rates in England North West England between 2001 and 2004. and Wales as a whole were about equal (except in To assess the contribution made by regional cases 2000).