Researchers also suggested increasing cyclosporiasis risk awareness among travellers to Mexico, reporting cases early and collaborating in investigations to identify sources and assess the extent of outbreaks.
Over the summers of 2015 and 2016, the UK reported outbreaks of cyclosporiasis in travellers returning from Mexico, mainly the Riviera Maya and Cancun regions.
As the source was not identified, there was the potential for a similar outbreak to re-occur.
UK tried to curb increase
This year at least 78 cases have been reported in the UK, of which 37 travelled to Mexico, 20 are awaiting travel history, 14 went to nine other places overseas and seven had no overseas travel.
The UK incident management team (IMT) met in May this year in advance of an anticipated increase in cases to coordinate response and focus on early communications and raising awareness.
“Cyclospora is not routinely tested for in primary diagnostic laboratories in the UK and requires additional microscopical procedures to identify the parasite.
“Maintaining competencies in identifying the parasite can be difficult when laboratories are not routinely observing Cyclospora.”
To improve testing, reminders were sent to diagnostic laboratories to consider Cyclospora in cases where individuals had compatible symptoms and travel history.
Discussions among UK parasitology reference labs looked at sharing confirmatory methodologies (fluorescence and stained microscopy and/or PCR), reviewing usefulness of quantitative PCR for monitoring assay development and performance and considering methods for genotyping and progression of whole genome sequencing.
The World Health Organization (WHO) was informed and alerts were sent to European Union countries via the Early Warning and Response System (EWRS) and the European Centre for Disease Prevention and Control (ECDC) Epidemic Intelligence Information System (EPIS).
Cyclosporiasis is transmitted through contaminated food, water or beverages and has an average incubation period of seven days after ingestion of sporulated oocysts.
Only two other EU countries have reported cases (France: nine in 2016; Belgium: four in 2017).
“The fact that only a very limited number of cases were reported from other European countries could be explained by under-diagnosis, under-reporting and/or because their citizens stayed in other regions of Mexico that were not affected by Cyclospora.”
Ongoing US and Canadian outbreaks
The Public Health Agency of Canada (PHAC) is investigating locally acquired infections in three provinces.
A total of 130 cases have been reported in British Columbia (13), Ontario (115) and Quebec (2).
Individuals became sick between May and mid-July with an average age of 47 years.
The Centers for Disease Control and Prevention (CDC) said it had been notified of 570 laboratory-confirmed cases of cyclosporiasis from 35 states. Texas has reported 197 cases.
At least 251 did not report international travel and were likely infected in the US and became ill on or after 1 May.
The agency said no specific vehicle has been identified and investigations to identify a potential source of infection are ongoing.
Previous outbreaks
Public health authorities in the UK and Canada reported an outbreak in travellers returning from Mexico in 2015; 79 in the UK and 97 in Canada.
In June 2016, Health Protection Scotland (HPS) was informed of cyclosporiasis among travellers returning from Mexico. Cases were also detected in England, Wales, Jersey and Isle of Man.
Individuals were a probable case if they had a sample date between 1 June and 28 October and travelled to Mexico in the previous 14 days and if oocysts were identified in stool specimens by a diagnostic lab.
Confirmed cases were probable cases confirmed microscopically by a national reference laboratory.
Between 1 June and 28 October, 440 cases were reported in the UK, of which 289 were confirmed.
The source of infection was likely a contaminated food or drink item supplied to multiple hotels.
Source: Eurosurveillance, Volume 22, Issue 32, 10 August 2017
“Cyclosporiasis in travellers returning to the United Kingdom from Mexico in summer 2017: Lessons from the recent past to inform the future”
Authors: DFP Marques, CL Alexander, RM Chalmers, R Elson, J Freedman, G Hawkins, J Lo, G Robinson, K Russell, A Smith-Palmer, H Kirkbride