Two geographically separated food-borne outbreaks in Sweden linked by an unusual Cryptosporidium parvum subtype, October 2010

Abstract

The number of sporadic cases of Cryptosporidium identified in the Stockholm county area increased above the expected limit during October 2010. Additionally, two food-borne outbreaks of cryptosporidiosis occurred in two other Swedish cities: Umeå (4 October) and Örebro (9 October). The outbreak investigations did not reveal any responsible food item, however fresh herbs were suspected. Thirty stool samples, originating from all three events, tested positive for Cryptosporidium oocysts. Polymerase chain reaction (PCR) and subsequent restriction fragment length polymorphism (RFLP) revealed that 27 individuals were infected with C. parvum, two with C. hominis, and one with C. felis. Using sequence analysis of the GP60 glycoprotein gene, a polymorphic marker with high intra-species diversity, we identified the same C. parvum subtype IIdA24G1 in samples from both the Umeå outbreak and the Stockholm area cases, thus indicating a possible outbreak in the Stockholm area and establishing a link between these two events. C. parvum IIdA24G1 has not previously been described in connection with a food-borne outbreak. For the outbreak in Örebro, another subtype was identified: C. parvum IIdA20G1e. These findings demonstrate that subtyping C. parvum isolates using GP60 gene amplification can be used to link cases in an outbreak investigation and we recommend its use in future similar events.

An evaluation of the potential use ofCryptosporidiumspecies as agents for deliberate release

“…Both PCR-restriction fragment length polymorphism analysis and fluorescence in situ hybridisation proved to be useful for the identification of C parvum from faeces at species level 28. Molecular typing, for example, by sequence analysis of the GP60 glycoprotein gene, a polymorphic marker with high intraspecies diversity, may help to link different outbreak events or atypical clusters of infections 29 30. However, careful interpretation is required regarding potential deliberate transmission events because spatially unrelated ‘natural’ outbreaks in different parts of a country due to a single clone have been described 30.…”

“…Molecular typing, for example, by sequence analysis of the GP60 glycoprotein gene, a polymorphic marker with high intraspecies diversity, may help to link different outbreak events or atypical clusters of infections 29 30. However, careful interpretation is required regarding potential deliberate transmission events because spatially unrelated ‘natural’ outbreaks in different parts of a country due to a single clone have been described 30. Even in a large water-borne cryptosporidiosis outbreak in the UK associated with the consumption of cold tap water provided by a particular water company, no legal steps were taken because the evidence for causality was insufficient 31.…”

Socioeconomic burden of foodborne parasites

“…The lack of appropriate diagnostic tools to isolate the parasite along with piecemeal testing of food sources is a key constraint to estimating the foodborne burden of disease due to Cryptosporidium (Slifko et al, 2000). However, recent advances in molecular techniques and superior reporting systems (Gherasim et al, 2012) have resulted in increased detection of Cryptosporidium transmission through food handlers (Ethelburg et al, 2009), imported produce (Insulander et al, 2008), ready-to-eat salads (Amoros et al, 2010), shellfish (Potasman et al, 2002), meat (Budu-Amoako et al, 2011), and milk (Robinson et al, 2014).…”

Annual report of the Emerging Risks Exchange Network 2013

“…Food-borne outbreaks on the other hand, are less often detected and described than water-borne outbreaks (Gherasim et al, 2012).…”