The Public Health Agency of Canada (PHAC) said the source of the outbreak has not been identified.
Previous outbreaks in Canada and the US have been linked to imported fresh produce.
British Columbia has five cases and Ontario 15. Individuals became sick between May and early June and the majority (60%) are male with an average age of 53 years.
There have been no hospitalisations or deaths.
Parasite not common in Canada
PHAC said Cyclospora infections can be prevented by ensuring fresh produce is grown in countries where the parasite is not common, such as Canada, the US and European countries.
The agency added that washing produce does not always get rid of the Cyclospora parasite.
When contaminated food or water is ate or drunk, it may take seven to 14 days for symptoms to appear. Most people have symptoms for six to seven weeks.
Most people develop symptoms within one week after being infected with Cyclospora.
A total of 87 cases were reported in four provinces last year. Imported fresh produce were investigated but the source was not identified.
The US Centers for Disease Control and Prevention (CDC) noted 384 laboratory-confirmed cases of cyclosporiasis with illness onset in 2016.
The number of domestically acquired Cyclospora infections declined in 2016 compared to the three previous years.
The FDA has taken steps to combat Cyclospora cayetanensis foodborne illnesses linked to fresh cilantro grown in Puebla, Mexico including detaining it without physical examination and refusing admission except for producers on a ‘green list’.
CDC was notified of 546 people with confirmed Cyclospora infection from 31 states in 2015.
Last year, Public Health England (PHE) recorded 320 cases since June, with 230 reporting travel to Mexico (94 from England, 122 from Scotland and 17 in the rest of the UK).
Study of norovirus outbreak
Meanwhile, between November 2016 and March 2017 more than 400 Canadians developed norovirus gastroenteritis associated with eating British Columbia oysters.
Over 100 cases occurred mid-November in those at a Tofino oyster festival and six were from people attending a December oyster barbecue in Victoria.
Raw and cooked oysters led to illness with insufficient cooked to inactivate norovirus. Oysters should be cooked to an internal temperature of 90 °C for at least 90 seconds.
Trace-back of oysters consumed by infected individuals led to the closure of 13 geographically dispersed marine farms in British Columbia.
“Genotypic analysis of norovirus isolated from the cases included several variants of genogroup I (GI) early in the outbreak and both genogroups GI and GII later in the outbreak,” said researchers.
“Both GI and GII norovirus were detected in oysters from shellfish farms. This suggests that oysters bind and act as a reservoir for community outbreak strains and disseminate those strains to consumers.”
The infective dose of norovirus is estimated to be as few as 18 particles.
“Given the low infective dose and the viability of norovirus in cold water, we postulate that sewage spread by ocean currents may have contaminated geographically dispersed farms,” said researchers.
“Among potential sources under investigation are sewer overflows, metropolitan and local wastewater treatment plants, municipal raw sewage discharge, and commercial fishing vessels.”
Source: BCMJ, Vol. 59, No. 6, July, August 2017, page(s) 326, 327 BC Centre for Disease Control
“BC oysters and norovirus: Hundreds of cases in months with an “r””
Authors: Lorraine McIntyre, Eleni Galanis, Natalie Prystajecky, Tom Kosatsky