Outbreak of leptospirosis, which can be fatal in humans, attributed to increased construction in Sydney

This article is more than 1 year old

This article is more than 1 year old

Seven dogs have died in Sydney from a disease that can kill pets in 48 hours, is transmitted by rat urine and has emerged in New South Wales for the first time, possibly owing to construction “stirring up” rodent populations.

Leptospirosis is a bacterial infection that causes haemorrhages, organ failure and swelling of the brain and is potentially fatal to both dogs and humans.

Before this year NSW had never had a reported canine death from the disease. In the past three months there have been seven.

Prof Jacqueline Norris, an expert in veterinary medicine from the University of Sydney, said vets were grappling with the disease.

“We’ve never had leptospirosis,” Norris said. “Now we’ve got seven fatalities in three months. It’s like zero to 100 in a short period of time.”

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A vaccine against leptospirosis exists, and is widely used in Queensland, but it is not regularly prescribed in NSW owing to the rarity of the disease.

Pet owners are now advised to seek out the vaccination, keep their dogs away from puddles and ponds, wash their hands when feeding or touching their dogs, and remove food scraps that could attract rodents.

The disease infects dogs and humans through the gums, the mucous membranes in eyes and abrasions in skin – and can stay alive in water and moist environments.

On Sunday a vet in Potts Point warned that two infected dogs had played at the same park – Ward Park on Devonshire Street – and blamed flooding caused by the construction of light rail.

In February, after a spate of rat sightings, the City of Sydney said unprecedented levels of construction were creating “increased rat movements”.

At the same time a larger, hungrier breed of rat is slowly gaining supremacy in the city against other breeds, potentially furthering the spread of leptospirosis.

Affected dogs become lethargic, abnormally quiet and develop haemorrhages on their skin, or blood in their urine, Norris said.

“In Sydney, some of the fatal cases presented because they weren’t producing urine because the kidneys shut down,” she said. “The cases that have come in to us have been dead within 48 to 72 hours. It really knocks them down quite quickly.”

The president of the Australian Veterinary Association, Dr Julia Crawford, said the group was monitoring the situation. She advised owners to be cautious.

“If you have a dog that really likes to chase down holes, or you know your backyard is full of rats, don’t let your dog down there until we know more,” she said. “Or get your dog vaccinated.”

All the confirmed deaths from leptospirosis have been in a few inner-city Sydney suburbs.

“Speak to your vet about the actual situation in your local area,” Crawford said. “It’s a really nasty infectious disease.”

Norris said humidity and moisture were what allowed the disease to spread.

“In moist environments it will survive for a short period of time,” she said. “If rats have gone and urinated somewhere and you touch it, and you eat with hands without washing, that is a possible source.

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“There is a commercial vaccine that will protect against the strain we are seeing in Sydney at the moment. We have never recommended it for dogs in NSW and don’t routinely vaccinate against it because we haven’t seen leptospirosis in NSW for forever.

“The vaccine is routinely used in northern Queensland. Now we are emailing all the vets in the local inner west area to let them know.”

In February the City of Sydney said vibrations from construction were creating “increased rat movements” after five rats were spotted a Portuguese chicken shop and one in a dumpling restaurant.

On Wednesday Peter Banks, an ecology expert from the University of Sydney, told Sydney’s Daily Telegraph that the brown rat – which is bigger and eats more – was chasing away smaller black rats in Sydney.

Norris said her colleague’s findings could explain the spread of the disease but that experts were still searching for more information. “We are not yet sure of the point of source,” she said. “The possibilities could be contaminated waterways – until we know, avoid letting your dog swim in lakes and ponds.

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“We haven’t seen leptospirosis in Sydney dogs … So something has changed, whether movement of the rat population, whether it has something to do with construction with the tram lines, I can only speculate at the moment.”

Fifty-two people across Australia have also been infected with leptospirosis – and eight in the first 10 days of June – according to the latest statistics from the national notifiable diseases surveillance system.

But none of those infections have been in Sydney, and only four have been in NSW. There have been 37 infections in Queensland, five in Victoria, three in the Northern Territory and two in Western Australia.

NSW Health warns that leptospirosis can frequently be confused for the flu in early stages.

In humans, symptoms include fever, headache, vomiting and red eyes. In severe cases, it can lead to kidney failure, liver failure and jaundice, haemorrhages and meningitis (inflammation of the brain).