Cryptosporidium meleagridis from humans: Molecular analysis and description of affected patients

Objectives: To genetically characterize an unusual genotype of Cryptosporid ium from the stools of humans with diarrhoea and to identify risk factors i n the affected patients. Methods: DNA was extracted from human faeces where Cryptosporidium oocysts were detected by light microscopy. Cryptosporidial gene fragments from six different loci were analysed by PCR alone, PCR/RFLP and by DNA sequencing. Oocysts were characterized by light and immunofluorescence microscopy and e pidemiological data was collected from the affected patients. Results: Analysis of the Cryptosporidium oocyst wall protein (COWP) gene am plified from > 2000 human faecal samples identified 19 patients all of whic h produced an unusual RFLP profile. Subsequent DNA sequence analysis of thi s and an additional four genetic loci (including I SS rRNA sequences) confi rmed these as a homogeneous group which was genetically distinct from Crypt osporidium parvum. The isolates were identified as Cryptosporidium meleagri dis since the gene sequences were identical to those from this species reco vered from birds. Conventional microscopy showed oocysts indistinguishable from C. parvum and reacted strongly with two different commercially availab le anti-oocyst monoclonal antibodies. None of the patients showed risk fact ors unusual for cryptosporidiosis; however, ten of the cases occurred durin g the summer/autumn, six had a history of foreign travel, four were co-infe cted with Giardia, two were HIV positive, and six were without identifiable immunocompromising, factors. Conclusions: This study further confirms that C. meleagridis, in addition t o C. parvum, is involved in human disease. The study also highlights the la ck of basic information on the host range of this genus of parasites, the c omplexity of the transmission routes involved in human cryptosporidiosis, a nd the value of molecular techniques in identify hitherto unrecognised diff erences in Cryptosporidium from human faeces. (C) 2001 The British Infectio n Society.