In Thailand, two types of freshwater snails are commonly consumed. The first group is comprised of the larger Apple snails (Pomacea canaliculata), while the other group is simply referred to as Freshwater snails (Sinotaia sp. & Filopaludina sp.). Both of these genera can be found in abundant quantities throughout the region wherever there is fresh water available year-round.
General information about Apple snails
The apple snail, also known as the Golden apple snail, is commonly harvested in Thailand. They can be found in abundant quantities throughout the region wherever there is freshwater year-round. The peak season for collecting and eating apple snails in Thailand is generally from July to October, during the rainy season when the snails are most abundant.
Originally from South America, apple snails were first bred for food in snail farms in Taiwan. However, their rapid spread to other countries such as Japan, Vietnam, Thailand, Indonesia, and Malaysia has resulted in a pest problem. They can devastate rice fields at an alarming rate, faster than they can be harvested for food. In cases of heavy infestations, they are either sprayed with insecticides or fought biologically by releasing ducks or breeding carp fish. Manual harvesting is recommended by authorities only if the snail population on a paddy field is small.
Apple snails and their conspicuous eggs
A female snail reaches maturity and begins laying eggs at the age of two weeks. In the absence of natural predators, a female can lay up to one million eggs per year. The snail’s pink eggs are highly visible, typically appearing as a pink patch on wooden stems and structures above the water surface. Laying her eggs above the water’s surface protects them from fish predation. Apple snails have a tubular siphon for breathing air while submerged, which reduces their vulnerability to attacking birds. Both adaptations have helped these snails to survive and propagate. When paddy fields dry out, these snails can hide in the earth for up to eight weeks before making their way back up when the fields are irrigated.
Snails as carriers of parasites
Water snails are a common and regular part of the diet for many rural people. These have adapted to and eliminated harmful parasites in their staple food. However, water snails, along with swamp eels (Pla Laat, Ophisternon bengalense), mollusks, and fish, can contain trematodes, which are parasitic flatworms commonly known as flukes. Boiling these water snails for about 8 minutes will render the trematodes harmless.
On a related note, vegetables collected from water bodies in the region should not be consumed raw. They must be put into boiling water for a few seconds before consumption. This will kill any flukes floating around in search of a host for new development stages.
Lessons learned about freshwater snails for food:
- Apple- and other freshwater snails are a staple food for a large population in upcountry Thailand.
- The main harvest time for these snails is from July to October, which falls during the rainy season.
- Apple snails are becoming a pest in rice fields due to their ability to lay up to 1 million eggs per year and their effective predator avoidance strategies.
- It is necessary to thoroughly boil all snails before consumption to ensure food safety.
