Killer snail alert: “They slaughter dogs but pose a risk to humans too”

A small, insidious enemy that hides in gardens and thrives on rain. There is great fear in eastern Australia , particularly in the Sydney and Brisbane areas, over the rapid spread of the so-called “killer snail” or rat lungworm (Angiostrongylus cantonensis), a dangerous parasite that is causing an increasing number of serious infections, often fatal or with permanent neurological consequences, in dogs. Research from the University of Sydney has confirmed 93 cases in dogs between 2020 and 2024 , but lead researcher Phoebe Rivory warns that this is likely just “the tip of the iceberg”, with many more cases going undiagnosed.

The disease, rare but potentially lethal even for humans, is transmitted by the larvae of the parasite present in wild rats. These larvae are expelled through the feces of rodents and ingested by snails and slugs, which become intermediate hosts. When a dog ingests them, even accidentally, it can become infected and develop serious neurological symptoms. In some cases, the consequences are irreversible.

The infection and spread seems to be favored by climate change and increasing urbanization.

In recent years, particularly rainy weather has favored the proliferation of snails and slugs, contributing to the increase in cases. Researchers at the University of Sydney have observed a direct correlation between heavy rainfall and the growth of infections , with the highest peak recorded in 2022: 32 dogs affected in a single year. The risk, according to experts, is greater in the two to ten months following extreme weather events, when the parasites multiply more easily in humid environments. Professor Jan Šlapeta, one of the leading researchers on the phenomenon, explained that the worm larvae, once they enter the body of a dog or a human, can migrate to the brain, where they trigger potentially fatal inflammation. Researchers consider dogs a "sentinel population", which is why the cases recorded in Sydney and Brisbane are being monitored very carefully.

It is not only pets that are at risk . The increase in infections among pets may herald a growing danger for humans as well, who can contract the infection , albeit in rarer cases.

The disease, also known as neural angiostrongyliasis, can cause severe neurological symptoms, including eosinophilic meningitis , and lead to paralysis or even death. Between 1971 and 2018, 28 human cases were documented in Australia. The best-known case was that of Sam Ballard, a young rugby player from Sydney, who accepted a dare from friends to eat a garden snail in 2010. Sam contracted the parasite, fell into a coma for 420 days, and battled severe brain damage for eight years, until his death in 2018 at the age of 28. According to the New South Wales Department of Health, humans can be infected by eating snails or raw vegetables contaminated by their slime. Most people typically recover without complications, but 18 percent of cases can be fatal, and 14 percent can cause permanent neurological damage.

Health authorities recommend preventive measures, especially for those who live in high-risk areas: wash fruits and vegetables thoroughly, avoid dogs from eating snails, slugs or wet grass in parks after rain, and wear gloves when gardening. Prevention is essential, because once the parasite reaches the brain, the chances of recovery are drastically reduced.