Heavy Rains Spark Fears of Apple Snail Invasion as Red Eggs Appear in Shanghai Parks

Clusters of bright red apple snail eggs have been found on reeds, tree trunks and other structures beside waterways in several Shanghai parks, prompting concerns that heavy rain could accelerate the spread of the invasive species, Jiefang Daily reported today.

Red eggs have been recently spotted in Yixian Park in Baoshan District, Minhang Cultural Park in Minhang District and riverfront areas along the Suzhou Creek, according to the report.

Experts said the snails, which entered China in the 1980s and long thrived in southern rice fields, have increasingly appeared in urban parks in recent years as a result of human activity.

Liu Conghui, an associate researcher at the Shenzhen Institute of Agricultural Genomics under the Chinese Academy of Agricultural Sciences, said Shanghai's shallow waterfronts, aquatic plants, floating islands and landscape stakes provide suitable surfaces for the snails to lay eggs.

Heavy summer rainfall and drainage pumping can carry the snails from suburban waterways into urban rivers and park ponds, said Zhang Yinjiang, a professor at Shanghai Ocean University. The species can also spread through the release of aquatic animals, the transport of water plants and landscaping materials, and water sports equipment carrying young snails or egg masses.

The egg masses can damage aquatic biodiversity and ecosystems while reducing the visual appeal of waterfront parks, Zhang said. Apple snails are a major intermediate host for rat lungworm, and the snails and their mucus may carry parasite larvae. People who touch the snails or egg masses and then eat or rub their eyes without washing their hands could develop skin irritation or allergic reactions if toxins contact broken skin, he said.

Experts said the risk of parasite infection through skin contact is very low based on existing cases, but warned parents to keep young children and pets away. Accidental ingestion of apple snails can have serious consequences.

In areas used for water sports, the snails may also worsen eutrophication and water quality. If people fall into the water with open wounds or accidentally swallow it, they could face a risk of infection, Zhang said.

Residents who find snails or egg masses should report them. Without touching them directly, they can use gloves or a stick to push egg masses into the water so they cannot hatch, Liu said. After heavy rain, authorities should clear floating plants and debris, inspect waterways and remove egg masses to prevent the species from spreading, experts said.