Hawke’s Bay: Study reveals main cause of lepto outbreak after Gabrielle

The aftermath of flooding in Hawke's Bay following Cyclone Gabrielle. Photo / Warren Buckland

The main cause of a Hawke’s Bay leptospirosis outbreak after Cyclone Gabrielle floods was urine from livestock, not rodents, a new study has found.

A Massey University team carried out the study, which is being presented at a NZ Veterinary Conference in Wellington this week.

Internationally, post-flood leptospirosis (lepto) cases in humans are largely linked to rodents.

However, the new research discovered the main source behind a rise in cases in Hawke’s Bay in 2023 was from sheep, cattle and deer.

The bacterial disease can spread from livestock urine into flood waters, and then be transmitted to humans through cuts or scratches.

Hawke’s Bay farmer Nick Lepper contracted the disease after Cyclone Gabrielle.

He suspects he became infected cleaning flooded Pōrangahau homes.

“About three weeks after the cyclone, the first symptom was a loss of appetite,” he said.

His skin turned yellow, and his vision began failing.

Lepper visited Hawke’s Bay Hospital ED and was quickly diagnosed and given treatment, although he struggled on antibiotics due to a penicillin allergy.

“It was a slow journey. I lost 14kg in two weeks,” he said.

“I couldn’t keep [food] down.”

He was off work for a long period and was often bedridden with little or no energy.

He was 23 at the time, and said he was surprised at how serious it was.

It took six months to fully recover.

Professor Jackie Benschop led the study with a team from Massey University. Photo/ Supplied

Lepto is a bacterial disease transmitted from animals to humans.

It cannot be transmitted from human to human.

Hawke’s Bay had 38 confirmed cases of lepto in 2023, more than triple the number in previous years, making it the region with the highest increase.

Nationwide, there were 162 confirmed cases in 2023, about double the number on previous years.

Jackie Benschop, Massey University professor of veterinary public health, said a key finding from the study was the link between livestock and the Hawke’s Bay outbreak.

“The strains of lepto that were associated with [Hawke’s Bay] cases were livestock-associated rather than rodent-associated,” she said.

“The reason that is important is globally, internationally, flooding and lepto are associated with rodents.”

It was a “surprise for us”, she said.

Masters student Preeti Pandey discovered the livestock link.

A Navy rescue of a cow trapped neck deep in silt near the Tūtaekurī River after Cyclone Gabrielle. Photo / NZ Navy

Elsewhere, there was a clearer link to rodents.

Professor Benschop said the findings highlight the need to vaccinate dry stock (cattle, sheep and deer), and educate farmers about how to better protect themselves, such as covering wounds or wearing protective equipment.

Gary Hamilton-Irvine is a Hawke’s Bay-based reporter who covers a range of news topics including business, councils, breaking news and cyclone recovery. He formerly worked at News Corp Australia.