Officials in New Zealand are investigating six Listeria infections spread over four years that appear to be connected.

The Nelson Marlborough Public Health Service (PHS) has received four reports of listeriosis in the past 12 months — one each in December 2019, August, September and November 2020. There are also two historic patients from 2016 and 2018.

The Institute of Environmental Science and Research (ESR) has confirmed through testing that all six cases are linked, meaning they may be from a common food source.

Patients appear to be linked
Dr. Andrew Lindsay, public health physician and medical officer of health at Nelson Marlborough Health, said the investigation is ongoing.

“There are six cases that, on the basis of laboratory testing, appear to be closely genotypically related. The first in this group was notified in 2016 and the last was notified in November 2020,” he said.

“Five of six cases currently under investigation are from across Nelson, Marlborough and Tasman. One case resides elsewher in New Zealand but visited Nelson.”

Lindsay said because of the low number of cases, and in respect to patient privacy, he was unable to confirm if people had needed hospital treatment or died or share information on age range and gender.

The Ministry for Primary Industries (MPI) and PHS are trying to determine the source of contamination. MPI has published three food recalls in recent weeks affecting two premises in Nelson and Marlborough.

Earlier this week, New Zealand Food Safety advised the public to return Pestell’s Rai Bacon Company Ltd. ham products distributed to certain supermarkets and retailers nationwide, as they may contain Listeria monocytogenes. The agency confirmed there had been reports of illness.

Listeria recalls

Specific batches of Pestell’s champagne ham, cooked ham on the bone, boneless ham, boneless ham pieces, and sliced ham off the bone were affected. It also involves Pestell’s sliced ham served over the counter at seleced supermarket delicatessens with a use-by date up to and including Dec. 7, 2020.

Pestell’s Rai Bacon Co. started a recall as testing by a customer identified Listeria in products.

In mid-October, there was a product recall due to potential Listeria in ready-to-eat (RTE) meat products at Pak’N Save Blenheim, a supermarket in New Zealand.

Pak’N Save Blenheim found Listeria during routine testing and recalled products sold with a packed-on date between Oct. 6 and 11, 2020.

In late November, there was a further recall because of the risk of Listeria in RTE meat products at the store. This involved ham, chicken, polish sausage, pastrami and beef.

Melinda Sando, New Zealand Food Safety national manager of food compliance services, said Listeria is commonly found in the environment.

“An earlier recall at the store in October followed the detection of Listeria in some packaged meat products. Subsequent visits by MPI, as well as testing at the store revealed the presence of Listeria on equipment, resulting in a precautionary recall to ensure risk to consumers is minimized.”

Contamination occurred at Pak’N Save Blenheim. Products from the manufacturers listed in recalls sold in their own packaging at the store or elsewher were not affected.

A link between the Listeria recalls at Pak’N Save Blenheim and the Pestell’s Ham recall is still being investigated and no conclusions have been made. MPI is continuing to search for the source of the Listeria.

“Investigation into the source of the Listeria at Pak’N Save Blenheim continues and includes follow up of suppliers of the cooked ready to eat meats to the supermarket. Pestell’s is a supplier to Pak’N Save Blenheim,” said a spokeswoman for New Zealand Food Safety.