Molecular genotyping of human cryptosporidiosis in Northern Ireland: epidemiological aspects and review.

Background: Cryptosporidium parvum is the most common of the protozoal pathogens associated with gastrointestinal disease in Northern Ireland. Genotyping techniques are valuable in helping to elucidate sources and modes of transmission of this parasite. There have been no reports on the prevalence of genotypes in Northern Ireland, mainly due to a lack of discriminatory genotyping techniques, which recently have become available.
Aim: To investigate the genotype of C. parvum oocysts isolated from human faeces in sporadic cases of cryptosporidiosis in Northern Ireland.
Methods: Thirty-nine isolates of C. parvum, representing 79.6% of the total 1998 laboratory reports for the Eastern Health and Social Services Board, were investigated. Following DNA extraction from oocysts the thrombospondin-related adhesive protein 2 (TRAP-C2) locus was amplified by polymerase chain reaction (PCR) and subsequently sequenced.
Results: The majority of isolates (87.2%) were classified as bovine genotype II with the remainder (12.8%) being the human genotype I.
Conclusions: There is a high prevalence of the bovine genotype II parasite in sporadic cases around the greater Belfast area. Epidemiologically, this suggests that the most frequent mode of transmission may be from animals to humans, but does not suggest a high proportion of human to human spread.