Source (CC-BY-SA-4.0)

Cryptosporidium outbreak in Queenstown – Expert Reaction

boil water notice is in place for Queenstown and Frankton, as officials work to find the source of a cryptosporidium outbreak.

The parasite can infect people through faeces, and can also be transmitted through water supplies. However no clear link has been established yet between the 15 confirmed cases so far.

The SMC asked experts to comment. 

Professor Bruce Russell, Parasitologist, University of Otago, comments:

“This gut parasite (not a virus or bacteria) spreads when people consume water or food that is contaminated by animal poo containing the infective cryptosporidium oocyst. The infective stage of the Cryptosporidium parasite is resistant to chorine treatment, but boiling water will kill these stages.

“This outbreak is not unexpected. This preventable disease is one of the most important (yet neglected) causes of gastro in NZ. We get around 500-1000 cases every year, and around 10% need hospitalisation. The highest rates of Cryptosporidium are seen in South Canterbury, Southern, Taranaki and Waikato DHBs.

“If cryptosporidium is in Queenstown and Frankton’s water, it could take until the end of lambing season, or November, for the water supply to return to normal.

“Our lab has tried to get funding since 2018 to tackle these problems with no major successes. Our lab will close at the end of this year. We are the only lab in the southern hemisphere which can screen drugs targeting cryptosporidium, and only one of three in the world that can do this.

“There are no vaccines or registered drugs for Cryptosporidium. We use supportive care, or IV fluids in severe cases.”

No conflict of interest.

Anthony Pita, Laboratory Technician, Massey University, comments:

Cryptosporidium can be transmitted via waterways by faecal contamination from animals and humans. The parasite can be passed from person to person through the fecal-oral route.

“Two or more cases linked to a common source is classified as an outbreak. With a boil water notice in place this should mitigate the risk of further infection if the source is in the water supply, but household transmission of the disease is possible. The largest Cryptosporidium outbreak was recorded in Milwaukee in 1993 where an estimated 400,000 people were infected.

“It could be a major problem if Cryptosporidium is the water supply, and existing treatment barriers are not sufficient to remove the organisms. Note that Chlorine treatment is not effective against removing Cryptosporidium.

“This outbreak has not yet been definitively linked to water supplies, but after the 2016 Havelock North Campylobacter outbreak there have been numerous changes to the drinking water regulations as well as the health systems. Neither Taumata Arowai nor Te Whatu Ora existed in 2016. However, since Covid-19 we have also seen fewer outbreaks, so from a detection and response perspective, this will be an interesting test case.”

No conflict of interest declared.