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The Guardian
18 hours ago
- Health
- The Guardian
What is rat lungworm disease and why are cases rising in dogs in Australia?
Cases of rat lungworm disease have been increasing in dogs on Australia's east coast over the past five years, according to new research from the University of Sydney. A very rare but sometimes deadly condition caused by worm larvae travelling up the food chain, the disease has been found in a small but increasing number of dogs in areas affected by heavy rain, and occasionally also in humans. So why are cases growing and how worried should we be? The rat lungworm, or Angiostrongylus cantonensis, is a parasite that originated in south-east Asia but has spread to other parts of the world, including North America, Europe and Australia. The parasite's natural host is feral rats, but it can accidentally make its way to other animals through a complicated transmission process involving snails and slugs as intermediate hosts. When it finds its way into humans and dogs, rat lungworm can cause a disease called neural angiostrongyliasis. In humans, it's diagnosed as a kind of meningitis, or eosinophilic meningoencephalitis. Symptoms in humans include headaches, a stiff neck, tingling or pain in the skin, fever, nausea and vomiting. Symptoms in dogs include hindlimb and tail paralysis, urinary incontinence and abnormal pain responses. The time between eating the infected slug or snail and getting sick is usually between one and three weeks. University of Sydney doctoral researcher Phoebe Rivory, lead author of the recent paper, explained that it's not the parasite itself that does the damage but the body's attempts to fight it. 'In dogs and humans, the parasite enters the brain but rather than progressing to the lungs like it does in rats, it is killed in the brain by our own immune response. It is that overt immune response that causes severe headaches and sensations,' Rivory said. New South Wales Health says it is rare for humans to develop meningitis in response to rat lungworm, and most people who contract rat lungworm have no symptoms at all, while others may have only mild, short-lived symptoms. Rats infected with adult worms excrete larvae in their faeces, which is then ingested by snails and slugs. Dogs and people are most likely to contract the parasite when they deliberately or accidentally eat a raw snail or slug carrying the larvae, or unwashed vegetables, such as lettuce, contaminated with infected slime. The parasite is not contagious from person to person. In a well-known case, Australian man Sam Ballard contracted eosinophilic meningoencephalitis in 2010 after being dared by his friends to eat a slug. He fell into a coma for 420 days, and acquired a brain injury. Ballard died in 2018, aged 29. In another well-known case, an American woman was found to have rat lungworm disease after multiple attempts to seek medical help for strange symptoms after a holiday to Thailand, Japan and Hawaii. The University of Sydney researchers have been examining the prevalence of rat lungworm disease in dogs on the basis that they are a sentinel population for humans – that is, increased rates of the disease in dogs can be an early warning sign of human disease risk. Researchers analysed 180 clinical samples taken between 2020 and 2024 from dogs suspected to have had the disease, and confirmed 93 cases, all in or around Sydney and Brisbane, and a 'gradual upward trend'. They also discovered a spike of 32 cases in 2022, correlating with high levels of rainfall, which tends to supercharge snail and slug proliferation. Confirmed cases of the disease in dogs are still very low, restricted to NSW and Queensland, and have fallen since the 2022 spike identified by the researchers, although not to 2019 levels. The researchers suggest that educating communities about how to avoid infection, and what symptoms dog owners should look out for in their pets, may be worthwhile. Rat lungworm is not a notifiable disease in NSW due to its rarity. In both NSW and Queensland, preventative anti-parasitic treatments for people, especially children, known to have ingested slugs or snails can be accessed through the health system.
The Age
2 days ago
- Health
- The Age
Deadly ‘rat lungworm' on the rise in Sydney, experts warn
Infections by a parasitic worm carried by rats, snails and slugs that can cause lethal brain infections in humans are increasing in dogs on Australia's east coast, a Sydney study has found. Rat lungworm is an extremely rare but potentially fatal disease caused by larvae of the parasite Angiostrongylus cantonensis, which is found naturally in feral rats after it spread to Australia from South-East Asia. Infection causes dangerous inflammation in the brain. 'In dogs and humans the parasite enters the brain, but rather than progressing to the lungs like it does in rats, it is killed in the brain by our own immune response,' said Phoebe Rivory, who has submitted her PhD thesis on the disease to the Sydney School of Veterinary Science. 'It is that overt immune response that causes severe headaches and sensations.' Dogs and humans are considered accidental hosts but infection can be disastrous. At least two people have died from rat lungworm, including Sam Ballard, who ate a slug as a dare in 2010. The Sydney man contracted the parasite and entered a coma for 420 days; he emerged from it with severe brain injuries before he died in 2018. The researchers analysed five years of data and discovered 93 cases of rat lungworm in dogs around Sydney and Brisbane. There has been an increasing number of cases since 2010, 'suggesting escalating human health threats', they write in The Journal of Infectious Diseases. live in Sydney.
Sydney Morning Herald
2 days ago
- Health
- Sydney Morning Herald
Deadly ‘rat lungworm' on the rise in Sydney, experts warn
Infections by a parasitic worm carried by rats, snails and slugs that can cause lethal brain infections in humans are increasing in dogs on Australia's east coast, a Sydney study has found. Rat lungworm is an extremely rare but potentially fatal disease caused by larvae of the parasite Angiostrongylus cantonensis, which is found naturally in feral rats after it spread to Australia from South-East Asia. Infection causes dangerous inflammation in the brain. 'In dogs and humans the parasite enters the brain, but rather than progressing to the lungs like it does in rats, it is killed in the brain by our own immune response,' said Phoebe Rivory, who has submitted her PhD thesis on the disease to the Sydney School of Veterinary Science. 'It is that overt immune response that causes severe headaches and sensations.' Dogs and humans are considered accidental hosts but infection can be disastrous. At least two people have died from rat lungworm, including Sam Ballard, who ate a slug as a dare in 2010. The Sydney man contracted the parasite and entered a coma for 420 days; he emerged from it with severe brain injuries before he died in 2018. The researchers analysed five years of data and discovered 93 cases of rat lungworm in dogs around Sydney and Brisbane. There has been an increasing number of cases since 2010, 'suggesting escalating human health threats', they write in The Journal of Infectious Diseases. live in Sydney.
ABC News
2 days ago
- Health
- ABC News
Researchers uncover spike in potentially fatal 'rat lungworm disease'
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.
