Researchers uncover spike in potentially fatal 'rat lungworm disease'

Australia Broadcast Center

16-06-2025

Researchers are warning dog owners to be vigilant as a new study reveals a wet weather-driven spike in a potentially fatal disease.
Rat lungworm disease is caused by a parasite and is generally picked up by dogs after eating infected slugs and snails.
Dogs can die from an infection or be left paralysed if it isn't treated.
There have also been two human deaths from the disease in Australia, including Sydney man Sam Ballard who consumed a slug as a dare in 2010 and reportedly contracted the disease before dying from it in 2018, researchers said.
A team at the University of Sydney has confirmed at least 93 positive cases of the disease, otherwise known as canine neural angiostrongyliasis, across the country over a four-year-period from 2020 to 2024.
Cases peaked at 32 in 2022, which coincided with a La Nina event, and they found hotspots in both Brisbane and Sydney.
Lead author Phoebe Rivory said that's likely the "tip of the iceberg" and many more cases were likely both undiagnosed and untested.
"The main findings were that we saw a strong relationship between the number of cases and rainfall," Dr Rivory said.
"That makes sense, as you know, when you see lots of rain coming down, all these slugs and snails from your garden will emerge.
"We also saw a relationship with prior rainfall, indicating some priming of the environment. You know more vegetation, lusher gardens."
Researchers said it was likely Brisbane and Sydney recorded higher rates of the disease than elsewhere due to their similar climates.
They said high rates of pet ownership and access to emergency care also contributed to sample bias.
According to Jan Šlapeta from the University of Sydney's School of Veterinary Science, who also worked on the study, the invasive parasite rat lungworm was introduced to Australia from South-East Asia sometime after World War II.
As the name suggests, it's carried by rats but also by slugs and snails, which act as intermediary hosts after consuming rat faeces.
Professor Šlapeta described it as an "interesting" parasite because when it jumps to a host animal like a dog or a human, it travels directly to the brain, where it is killed.
It is then the immune response that can cause "serious headaches", and, in some cases, death.
He said the first reports of the disease were made in Brisbane in the 1990s and in Sydney in the early 2000s.
But prior to the recent study, no-one had set out to identify how prevalent the disease was.
It was thanks to a recent development in testing techniques that the team was able to do so.
The study proved it was, and with climate change likely to bring more wet weather, the researchers believe those numbers will only increase.
Professor Šlapeta said his aim was not to be alarmist, but rather to increase awareness about the disease for dog owners, particularly during high-risk periods like during heavy rain.
In particular, he said it was vital owners knew to keep their pets, especially young "inquisitive" dogs, away from slugs and snails and stop them from eating them.
Dr Rivory said simple tips that could help pet owners included washing outdoor water bowls.
For some reason, cats aren't at risk of contracting the disease, she said.
If a dog is infected, it may not start showing any symptoms for a "good couple of weeks", Dr Rivory said.
Then, symptoms might include paralysis, especially of the hind legs, or pain in the spine.
"They [may] get wobbly or non-functioning hind legs, because it kind of progresses from the rea to the front," she said.
Other signs might include confusion or fatigue.
Treatments are available if the dog is taken to the vet and treated early.
Veterinarian Sasha Miles from the Unusual Pet Vets on the Sunshine Coast agreed early detection was key, as by the time it led to paralysis, it was often too late to do anything about it.
"I think … it would be unlikely that they would make a full recovery … I think euthanasia would be on the table," she said.
She said other symptoms to look out for in dogs included a cough and muscle weakness.
Dr Miles hadn't treated the condition in dogs, but has seen it in some species of birds.
She agreed with taking preventative measures like daily washing water bowls with detergent and ensuring aviaries were snail and slug-proof for birds.
"And I guess just if it's been raining heaps … supervising your animal and … looking around the back garden for snails and slugs and if they are there then not letting the pet out in that area," Dr Miles said.