Sporadic human cryptosporidiosis caused by Cryptosporidium cuniculus, United Kingdom, 2007-2008.
ABSTRACT To investigate sporadic human cryptosporidiosis trends in the United Kingdom, we tested 3,030 Cryptosporidium spp.-positive fecal samples, submitted for routine typing in 2007-2008, for C. cuniculus. C. cuniculus prevalence was 1.2%; cases were mostly indigenous and occurred across all age groups. Most occurred during August-October and may be linked to exposure opportunities.
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ABSTRACT: Cryptosporidium spp. have been found in the faeces of over 150 mammalian host species, but the risks to public health from wildlife are poorly understood. In summer 2008, the Cryptosporidium sp. rabbit genotype was identified as the aetiological agent in an outbreak of waterborne human cryptosporidiosis. The source was a wild rabbit that had entered a treated water tank. To establish current knowledge about Cryptosporidium spp. infecting lagomorphs, especially the host range and biological characteristics of the rabbit genotype, and the potential risks to public health that rabbits may pose in the transmission of zoonotic cryptosporidiosis, we undertook a literature and data review. The literature returned demonstrates that although the European rabbit (Oryctolagus cuniculus) has been the most widely studied lagomorph, few large scale studies were found. The prevalence of Cryptosporidium spp. in wild rabbit populations in the two large scale studies was 0.9% (95%CI 0.2-5.0) and 0.0% (95%CI 0.0-1.6). Neither study provided age nor sex profiles nor typing of Cryptosporidium isolates. The infecting Cryptosporidium species was confirmed in just four other studies of rabbits, all of which showed the rabbit genotype. Human-infectious Cryptosporidium species including Cryptosporidium parvum have caused experimental infections in rabbits and it is likely that this may also occur naturally. No published studies of the host range and biological features of the Cryptosporidium rabbit genotype were identified, but information was generated on the identification and differentiation of the rabbit genotype at various genetic loci. Both pet and wild rabbits are a potential source of human cryptosporidiosis and as such, good hygiene practices are recommended during and after handling rabbits or exposure to their faeces, or potentially contaminated surfaces. Water supplies should be protected against access by wildlife, including rabbits.Zoonoses and Public Health 12/2010; 57(7-8):e1-13. · 2.09 Impact Factor
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ABSTRACT: To assess the prevalence and public health significance of rabbit cryptosporidiosis, a total of 1,081 fecal specimens were collected between October 2007 and April 2008 from rabbits on eight farms in five different areas in Henan Province, China, and were examined by microscopy after Sheather's sucrose flotation and modified acid-fast staining. The average infection rate of Cryptosporidium was 3.4% (37/1,081 samples). There was a significant association between the prevalence of Cryptosporidium and the age of animals (chi(2) = 57.13; P < 0.01); the prevalence of cryptosporidiosis in 1- to 3-month-old rabbits was the highest (10.9%). The Cryptosporidium species in microscopy-positive specimens were genotyped by sequence analyses of the 18S rRNA, 70-kDa heat shock protein (HSP70), oocyst wall protein (COWP), and actin genes and were subtyped by sequence analysis of the 60-kDa glycoprotein (gp60) gene. Only the Cryptosporidium rabbit genotype was identified, with 100% sequence identity to published sequences of the 18S rRNA, HSP70, COWP, and actin genes, and the strains belonged to three gp60 subtypes (VbA36, VbA35, and VbA29). In view of the recent finding of the Cryptosporidium rabbit genotype in human outbreak and sporadic cases, the role of rabbits in the transmission of human cryptosporidiosis should be reassessed.Journal of clinical microbiology 09/2010; 48(9):3263-6. · 4.16 Impact Factor
- Unusual Cryptosporidium genotypes in human cases of diarrhea DOI: 10.3201/eid1411. Emerg Infect Dis 14 1800-2080239..
S poradic Human
c unic ulus,
United K ingdom,
Rachel M. Chalmers, Kristin Elwin,
Stephen J. Hadfi eld, and Guy Robinson
To investigate sporadic human cryptosporidiosis trends
in the United Kingdom, we tested 3,030 Cryptosporidium
spp.–positive fecal samples, submitted for routine typing in
2007–2008, for C. cuniculus. C. cuniculus prevalence was
1.2%; cases were mostly indigenous and occurred across
all age groups. Most occurred during August–October and
may be linked to exposure opportunities.
Most cases in the United Kingdom are caused by C.
parvum or C. hominis; rare infections with other species
and genotypes include C. meleagridis, C. felis, C. canis,
C. ubiquitum, C. hominis monkey, skunk, horse, and
rabbit (1–3). In summer 2008, the rabbit genotype caused
a waterborne outbreak in drinking water (4). Previously,
only 1 human infection, also identifi ed in the United
Kingdom, was known (1), although routine typing based on
RsaI restriction fragment-length polymorphisms (RFLPs)
within the Cryptosporidium oocyst wall protein (COWP)
gene (2) does not differentiate the rabbit genotype from C.
hominis (4). After phylogenetic and biologic investigations,
the rabbit genotype has been renamed C. cuniculus (5).
However, information is lacking about the occurrence
and epidemiology of animal and human infections outside
the outbreak, which mainly involved adult females (5–7).
To investigate trends in humans, we conducted enhanced
testing of Cryptosporidium spp.–positive fecal samples
from patients with sporadic diarrhea (submitted for routine
typing during 2007–2008) with the purpose of identifying
and characterizing C. cuniculus.
he protozoan parasites Cryptosporidium spp. are
major causes of gastrointestinal disease worldwide.
Archived DNA from all samples received for typing
during January 2007–December 2008 that showed C.
hominis COWP PCR-RFLP RsaI profi les were retested by
single-round small subunit (SSU) rRNA PCR-RFLP using
SspI, which generates a pattern unique to C. cuniculus (4).
An exception occurred during the outbreak period (July and
August 2008) when all Cryptosporidium spp.–positive stool
samples were tested by a pan-genus nested PCR specifi c for
the SSU rRNA gene and products digested with SspI and
VspI (4). Although differentiating more species/genotypes
than the COWP PCR-RFLP (7), this assay is unsustainable
for typing large numbers of samples on a routine basis. C.
cuniculus was confi rmed by sequencing ≈830 bp of the
SSU rRNA gene and ≈850 bp of the 60-kDa glycoprotein
(GP60) gene by using nested PCR protocols (4).
Data were analyzed in Epi Info version 6 (Centers
for Disease Control and Prevention Atlanta, GA, USA).
Incomplete data for Northern Ireland were excluded, but
no C. cuniculus cases were identifi ed there. Case-patients
with sporadic C. cuniculus, C. parvum, and C. hominis
infections were compared by age using the Mann-Whitney
2-sample test, by sex using the Mantel-Haenszel version
of the χ2 test, by month of specimen submission, and by
Government Offi ce Region (England and Wales) or Health
Board (Scotland) of the primary diagnostic laboratory.
In total, 37 (1.2%) of 3,030 infections were caused by C.
cuniculus: 23 in 2007 and 14 in 2008 (online Appendix Table,
fi ve were in patients from England and Wales, and 12
patients were from Scotland. Other cryptosporidia detected
were C. parvum (n = 1,506, 49.7%), C. hominis (n = 1,383,
45.6%), C. meleagridis (n = 26), C. felis (n = 8), cervine
genotype (n = 8), co-infection C. hominis and C. parvum
(n = 5), novel or unidentifi ed genotypes (n = 5), and C.
hominis monkey genotype (n = 1); 88 did not amplify with
the PCR primers. Substitution of routine typing with the
SSU rRNA nested PCR-RFLP during the outbreak did not
increase the number of “unusual” cryptosporidia, apart
from C. cuniculus, indicating the routine COWP PCR-
RFLP is otherwise appropriate for typing for epidemiologic
purposes in the United Kingdom.
The age range of patients with sporadic C. cuniculus
infection was 1–74 years (mean 29 years; median 31
years), signifi cantly older than C. hominis case-patients
(range 0–83 years; mean 19 years; median 13 years)
(Mann-Whitney 2-sample test value = 11.12, df = 1, p =
0.0009) and C. parvum case-patients (range 0–86 years;
mean 17 years; median 29 years) (Mann-Whitney 2-sample
test value = 15.24, df = 1, p = 0.00009) (Figure 1). The
sex distribution was 14 (37%) female and 22 (58%) male
patients, with the sex of 1 patient not known, compared with
sporadic C. parvum (781 [51.9%] female) and C. hominis
536 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 3, March 2011
Author affi liations: Public Health Wales Microbiology–Singleton
Hospital, Swansea, UK
Cryptosporidium cuniculus, UK, 2007–2008
(736 [53.2%] female) cases, although the difference was
not signifi cant (χ2 = 4.01, df = 2, p = 0.13).
More C. cuniculus cases were detected in the late
summer and autumn than in the winter and spring, similar
to infections with C. hominis but not C. parvum (Figure
2). Three C. cuniculus cases were identifi ed in the East
Midlands, the outbreak affected region, but none were
found in Northamptonshire, the outbreak-affected area.
Most cases (24%) were in the Eastern region of England.
Two case-patients had traveled outside the UK, one to
Spain and the other destination not known, during the
Occupational and environmental exposure data were
available for 14 C. cuniculus case-patients from patient
questionnaires administered by local Environmental Health
Departments. No occupational risks were linked to rabbits.
One patient (a 9-year-old boy) reported direct contact with
rabbits (a pet), and 2 patients had potential environmental
contact (a 63-year-old woman played golf, and a 36-year-
old man sat on grass during a walking holiday). Two case-
patients reported diarrhea in other residential contacts.
None of the patients reported links with (lived in, had
visited or received visitors from) the outbreak-affected
area. Available clinical details were insuffi cient for all
cryptosporidiosis case-patients for comparative purposes.
One C. cuniculus case-patient was an immunosuppressed
child who had received a kidney transplant.
Two GP60 subtype families, Va (n = 18) and Vb (n
= 19), were detected in sporadic C. cuniculus isolates,
linked to patient sex; 10/14 (71.4%) female patients had
Va subtype, compared with 7/22 (31.8%) male patients
(χ2 = 5.24, df = 1, p = 0.022). No signifi cant difference
in age or regional distribution was found, but cases with
Va occurred only in August through December, while Vb
cases occurred all year but mostly in August (Figure 2).
Representative sequences have been deposited into
GenBank: GU971631–GU971650 (GP60) and GU971628–
GU971630 (SSU DNA). The latter are identical to those
deposited previously (EU437413, FJ262724–FJ262726)
(1,4) and are C. cuniculus (5).
C. cuniculus was fi rst identifi ed as a human pathogen
during a waterborne outbreak, and its epidemiology has now
been described for sporadic cases in the United Kingdom.
Although the numbers are small, and the data need to be
interpreted with caution, it was the third most commonly
identifi ed Cryptosporidium species in patients with diarrhea
during the study period, after C. parvum and C. hominis.
All C. cuniculus isolates identifi ed by PCR-RFLP were
confi rmed by sequence analysis, indicating the reliability
of the test algorithm used, although the development of
specifi c probes will enhance testing capability. All ages
were infected with little age delimitation <50 years, after
which numbers declined. Contrast this to C. parvum
and C. hominis, which are both linked to young age. C.
cuniculus distribution is seasonal, peaking in August
through November, and differences in seasonal distribution
of GP60 subtypes were marked.
Rabbits are the natural hosts for C. cuniculus (5),
and seasonal distribution and variation in humans may
refl ect rabbit breeding seasons and infections, although
good epidemiologic studies of Cryptosporidium spp. in
wild rabbits are lacking (7). Studies of farmed and wild
rabbits so far indicate that GP60 subtype Vb predominates
(7–9), although the outbreak was caused by Va (4). Unlike
with C. hominis, seasonal distribution of cases was not
linked to foreign travel. The C. cuniculus outbreak had
occurred in July when few sporadic cases were detected.
The distribution of sporadic cases was the opposite of
the outbreak in which more case-patients were female
(6). The association between GP60 subtypes and patient
sex is intriguing. A small number of case-patients had
possible exposure risks, although this requires further
Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 3, March 2011 537
Figure 1. Age distribution of patients with sporadic cases of
Cryptosporidium cuniculus, C. hominis, and C. parvum infection in
England, Wales, and Scotland, 2007–2008.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
No. C. cuniculus infections
Figure 2. Monthly distribution of sporadic cases of Cryptosporidium
cuniculus, C. hominis, and C. parvum infection in England, Wales,
and Scotland, 2007–2008.
investigation. The only known hosts of C. cuniculus are
humans and European rabbits (Oryctolagus cuniculus)
(5,7–9), and until population-based studies of rabbits are
undertaken, the risks cannot be fully evaluated, nor the
human epidemiology fully explained.
We thank Nigel Crouch and Brian Campbell, Cryptosporidium
Reference Unit, for technical support, and the Health Protection
staff who provided patient data.
This work was supported by the Department for
Environment, Food and Rural Affairs and managed by the
Drinking Water Inspectorate under project DWI 70/2/241. The
national Cryptosporidium typing program was funded for England
and Wales by Welsh Assembly Government and for Scotland by
Health Protection Scotland.
Dr Chalmers is head of the UK Cryptosporidium Reference
Unit, Public Health Wales. Her main research interests are the
epidemiology, management, and control of Cryptosporidium spp.
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Address for correspondence: Rachel M. Chalmers, UK Cryptosporidium
Reference Unit, Public Health Wales Microbiology, Singleton Hospital,
Swansea, Wales, SA2 8QA UK; email: email@example.com
538 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 3, March 2011
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