archived dna from all samples received for typing during january 2007december 2008 that showed c. hominis cowp pcr - rflp rsai profiles 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 specific 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 confirmed 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 identified 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  test , by month of specimen submission , and by government office 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 ( table a1 ) . twenty - five 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 unidentified 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 174 years ( mean 29 years ; median 31 years ) , significantly older than c. hominis case - patients ( range 083 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 086 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 ( 736 [ 53.2% ] female ) cases , although the difference was not significant (   =  4.01 , df  =  2 , p = 0.13 ) . age distribution of patients with sporadic cases of cryptosporidium cuniculus , c. hominis , and c. parvum infection in england , wales , and scotland , 20072008 . 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 identified 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 incubation period . monthly distribution of sporadic cases of cryptosporidium cuniculus , c. hominis , and c. parvum infection in england , wales , and scotland , 20072008 . occupational and environmental exposure data were available for 14 c. cuniculus case - patients from patient questionnaires administered by local environmental health departments . 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 . 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 (   =  5.24 , df  =  1 , p = 0.022 ) . no significant 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 : gu971631gu971650 ( gp60 ) and gu971628gu971630 ( ssu dna ) . the latter are identical to those deposited previously ( eu437413 , fj262724fj262726 ) ( 1,4 ) and are c. cuniculus ( 5 ) . c. cuniculus was first identified 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 identified cryptosporidium species in patients with diarrhea during the study period , after c. parvum and c. hominis . all c. cuniculus isolates identified by pcr - rflp were confirmed by sequence analysis , indicating the reliability of the test algorithm used , although the development of specific 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 reflect 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 ( 79 ) , although the outbreak was caused by va ( 4 ) . unlike with c. hominis , seasonal distribution of cases was not linked to foreign travel . the distribution of sporadic cases was the opposite of the outbreak in which more case - patients were female ( 6 ) . a small number of case - patients had possible exposure risks , although this requires further investigation . the only known hosts of c. cuniculus are humans and european rabbits ( oryctolagus cuniculus ) ( 5,79 ) , and until population - based studies of rabbits are undertaken , the risks can not be fully evaluated , nor the human epidemiology fully explained .