Animal contact linked to large Cryptosporidium outbreak

Researchers have provided details about one of the largest Cryptosporidium outbreaks in England in recent years.

The outbreak of Cryptosporidium parvum was associated with a multi-day lamb petting event in the south-west of England in 2023. The primary hypothesis was that exposure to lambs within designated petting pens was the source of Cryptosporidium.

A study published in the journal Epidemiology and Infection detailed how an outbreak investigation found 23 laboratory-confirmed primary Cryptosporidium parvum cases, while the cohort study identified 83 cases of cryptosporidiosis-like illness. Individuals who held or cuddled a lamb within a pen were more likely to develop cryptosporidiosis-like illness.

More than 4,000 laboratory-confirmed infections of the parasite are recorded in England every year. An industry Code of Practice supports minimizing infection risks from animal contact at visitor attractions.

In April 2023, routine surveillance by the UK Health Security Agency (UKHSA) identified significantly higher Cryptosporidium lab notifications in the south-west of England compared to seasonally expected levels. A review of surveillance questionnaires found that many cases visited a single venue in the preceding Easter holiday period for a lamb petting experience. 

Access to the venue allowed entry to one of four lamb pens for petting and bottle feeding while adults watched from outside the pen. Although handwashing facilities and signage were present, they were not near the sites of animal contact, which potentially reduced their use and effectiveness, said scientists.

Because the event had ended by the time of the site review, no animal or environmental sampling was done, given the likely low yield from testing and the absence of an ongoing public risk. 

Several patients hospitalized

Across the 16 days, 1,372 tickets were pre-ordered for the animal contact event.

Five of the 23 confirmed primary cases reported hospital admission, with two more people being assessed and discharged by emergency care. The median age of primary cases was 11, ranging from 2 to 49 years old; 65 percent were female; and the median time from event attendance to symptom onset was seven days, ranging from 2 to 8 days.

For the cohort study, a survey was sent to 647 email addresses linked to ticket bookings. The analysis included 157 responses, 75 primary cases, and eight secondary cases.

Among primary cases, 40 were children under 18 years of age. Self-reported symptoms, including diarrhea, were consistent with Cryptosporidium infection. Over half of the cases had symptoms lasting for six days or more, and four reported hospital admission.

Evidence showed that awareness of the potential for disease transmission on-farm sites reduced a person’s risk of illness.

“There is likely a need for greater awareness among clinicians on the public health benefit of fecal sampling for patients presenting with diarrheal disease following contact with livestock and primarily an improved understanding for the public on both the risks of disease transmission during animal petting activities and the symptoms to act upon post-exposure,” said researchers.

Parasite in vegetables

Another study has assessed the presence of Cryptosporidium in pre-washed ready-to-eat (RTE) vegetables from retailers in the UK. In May and July 2023, 36 samples were purchased from four supermarkets in Canterbury.

Findings published in the journal Parasitology Research revealed 14 samples were PCR-positive. Four had significant similarities to Cryptosporidium parvum.

Scientists said finding the point in the chain where contamination occurred is complicated by multiple vegetable varieties in a package. Vegetables from individual chain supermarkets are packaged in their central facilities and distributed nationwide. 

Dr. Anastasios Tsaousis, from the University of Kent, said consumers need to be more aware of the storage of vegetables and handwashing before eating.

“While our 2023 study cannot distinguish between live and inert Cryptosporidium, it is nevertheless important in that the presence of Cryptosporidium in pre-washed vegetables could mean revisiting the sanitation methods employed by suppliers along the chain of production, such as improved hygiene measures during harvesting, processing, packaging, transportation, and storage.”

(To sign up for a free subscription to Food Safety News, click here.)