Rat Lungworm Disease in Australia: Should You Be Worried?

Experts Warn of Spike in This Rare but Potentially Fatal Infection

Cases of a rat-borne parasite that can severely affect the brain are on the rise in pets—and could threaten human health in eastern Australia. Here’s what you need to know.

What is rat lungworm disease?

Rat lungworm disease is caused by a parasite known as Angiostrongylus cantonensis. It lives in rats but spreads to snails and slugs through infected rat droppings. People and dogs can accidentally become infected by ingesting these intermediate hosts.

Why is this disease in the news?

A University of Sydney study has shown an alarming increase in cases among dogs in Sydney and Brisbane since 2019. The peak was in 2022, following unusually wet conditions caused by La Niña. Experts now warn this trend could signal a growing risk for human infections.

Can humans get rat lungworm disease?

Yes. Although rare, humans can become infected by:

  • Eating a raw or undercooked snail or slug

  • Consuming contaminated slime on unwashed vegetables, such as lettuce

  • Accidentally ingesting larvae from handling snails or slugs during gardening

Once inside the body, the parasite migrates to the brain, triggering an immune reaction.

What are the symptoms?

Symptoms typically appear 1 to 3 weeks after exposure. These may include:

  • Headache

  • Neck stiffness

  • Tingling or pain in the skin

  • Fever

  • Nausea and vomiting

In serious cases, the parasite can cause eosinophilic meningitis, a dangerous inflammation of the brain and spinal cord.

Have there been deaths in Australia?

Yes. The most well-known case involved Sydney man Sam Ballard, who died years after developing brain damage from eating an infected slug as a dare in 2010. His case brought national attention to the disease’s risks.

What is happening in pets?

Dogs are especially vulnerable. Vets in Sydney and Brisbane have reported dozens of cases since 2019. Like humans, dogs can develop neurological symptoms and even die if untreated.

How is the disease diagnosed?

Doctors suspect rat lungworm disease when patients with meningitis have high levels of eosinophils (a type of white blood cell) in their blood or spinal fluid. A history of eating raw produce or contact with snails or slugs also helps guide diagnosis.

How is it treated?

Most people recover fully without treatment. However, in cases of severe meningitis, hospitalisation and specialist care may be required.

Preventative treatment with a medication like albendazole may be recommended if someone is known to have recently eaten a snail or slug—speak to a doctor immediately in such cases.

Is it contagious?

No. Rat lungworm disease cannot be spread from person to person or from dogs to people. It is only caught through ingestion of the parasite itself.

Who is most at risk?

Those most at risk include:

  • Children playing outdoors

  • Gardeners who handle soil, snails or slugs

  • People who eat raw vegetables without washing them

  • Travellers to countries where the parasite is more common, such as parts of Southeast Asia and the Pacific Islands

How can it be prevented?

Follow these tips to protect yourself and your pets:

  • Don’t eat raw snails or slugs

  • Thoroughly wash all fruits and vegetables before eating

  • Supervise children in gardens and outdoor spaces

  • Wear gloves when gardening or handling soil

  • Wash your hands after outdoor activities

  • Control rats, snails and slugs around your home and garden

  • Use bait safely to avoid accidental poisoning of children or pets

Is there a vaccine for rat lungworm?

No, there is currently no vaccine available for humans or animals. Prevention is the only protection.

What should I do if I think I’ve been exposed?

If you’ve eaten a slug or snail—either accidentally or on purpose—or eaten unwashed leafy vegetables and experience symptoms, seek medical advice immediately. Early intervention can help prevent complications.

Conclusion

While rat lungworm disease is still considered rare, the recent spike in pet infections across eastern Australia is a timely reminder to take preventive measures seriously. Washing your hands and produce, and staying vigilant during wet weather, could make all the difference.

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