Spotted in city: Invasive snail species poses health risks

Chennai: The Giant African Snail (Lissachatina fulica), one of the world's worst invasive species and a known carrier of parasites that can cause brain inflammation in humans, has infested parts of the city and on its outskirts. Experts warn that its presence poses serious risks to city residents, particularly during floods when the snails can spread rapidly.A research team confirmed populations of the invasive snail at St Thomas Mount, Tirusulam, and Perungalathur Hills. The team conducted opportunistic field surveys between Sept and Nov 2024 across urban and semi-urban locations. The study warned that the snail is not only an agricultural pest but also a vector for parasitic nematodes such as Angiostrongylus cantonensis and A. costaricensis, which cause eosinophilic meningoencephalitis (brain infection) and abdominal angiostrongyliasis in humans. These infections, often spread through ingestion of contaminated gastropods or their residues, present major public health threats wherever the snail has established populations."Chennai faces significant risks from the presence of L. fulica, a vector for zoonotic diseases, which poses serious public health concerns," said Phillmon Smart Edward, corresponding author of the paper, citing previous studies. "The city's susceptibility to flooding during the monsoon exacerbates the spread of infections, as floodwaters disperse snails and contaminate resources. This risk is heightened during the rainy, winter months when snails emerge from hibernation."The study, published in the newsletter Zoo's Print, was carried out by the Centre for Landscape Ecology, Fedstan GMC, Chennai, the University of Trans-Disciplinary Health Sciences and Technology (Bengaluru), and the Bombay Natural History Society.Researchers said the snail, capable of surviving in many habitats with a varied diet, feeds on more than 500 plant species, including crops, and has been consistently listed among the ‘100 Worst Alien Invasive Species' worldwide. This makes documentation of its spread and assessment of its ecological impact urgent.The species' history in India dates back to 1847, when malacologist William Henry Benson gifted a pair of snails brought from Mauritius to a friend in Kolkata, who then released them in his garden. Since then, the species travelled from East Africa to India through merchant ships and spread across several states, including Kerala, Tamil Nadu, and Karnataka. A 1984 study already recorded its presence in districts such as Chennai, Chidambaram, Coimbatore, and Chengalpet.