Cryptosporidiosis in Finland is predominantly of domestic origin: investigation of increased reporting, 1995–2020

Abstract

Background

Cryptosporidiosis is gastroenteritis caused by Cryptosporidium. Since 2017, reporting of cryptosporidiosis has increased in Finland.

Methods

We describe demographics of cryptosporidiosis cases notified to Finnish Infectious Disease Register (FIDR) during a 21-year surveillance period, 1995–2020, and a retrospective investigation of increased cryptosporidiosis in Ostrobothnian hospital districts in summer 2018.

Results

Incidence of cryptosporidiosis during the period 2017–2020 represented 20-fold increase from the period 1995–2016, with the highest incidence detected in Ostrobothnia. In 2018, cryptosporidiosis in Ostrobothnia was associated with living on or visiting a farm where the production animals had diarrhoea, noticing more flies than usual, gardening or handling manure and having a family member with gastroenteritis. Four gp60 subtypes were identified in patient samples: IIaA18G1R1, IIaA15G2R1, IIaA13G2R1 and IIaA15G1R1.

Conclusions

In Finland, Cryptosporidium has been included in gastrointestinal PCR diagnostic panels in most clinical laboratories since 2016. Since then, the number of reported cases has subsequently increased, indicating improved diagnostics and awareness of the illness. In 2018, several C. parvum subtypes were identified in patients suggesting that the increase was not caused by a single source. Cryptosporidiosis increased in Finland in 2020 despite hand washing recommendations and travel restrictions imposed during the COVID-19 pandemic, indicating that domestic cases are more frequent than previously considered. To monitor cause and origin of cryptosporidiosis and the effect of control measures, Cryptosporidium should be identified at subspecies level, and travel history should be included in FIDR notification. Those working with cattle and calves require precise instructions on how to prevent C. parvum infection.

Keywords:

• Cryptosporidiosis
• demography
• disease outbreaks
• Finland
• humans

Acknowledgements

The authors thank the health officials from the hospital districts of Ostrobothnia for their valuable work in the outbreak investigation. The authors also thank the personnel of the Finnish Institute for Health and Welfare’s Infectious Diseases Control and Vaccination unit and the personnel of the Finnish Food Authority’s Veterinary Bacteriology and Pathology unit.

Ethical approval

The investigation was mandated by Finnish Communicable Diseases Act 1227/2016.

Disclosure statement

No potential conflict of interest was reported by the author(s).