Brazil under pressure

Oct 22, 2007 08:23 GMT  ·  By

In some countries, people drool when thinking about snails, while in other people`s case the only reaction is?yuck! And what was meant to be a big business has actually become a major nuisance for Brazil: the giant African snail (Achatina achatina). The invader measures up to 8 inches (about 20 centimeters, 5 times more than a garden snail of the Helix genus) and weighs over 1 pound (500 grams) and now thrives in almost every Brazilian state. Its eradication seems near impossible.

"Raining season starts in November, and that's when they like to [lay] eggs. The snails will show up more, so we do expect the situation to get worse." said Silvana Thiengo, a mollusk expert from Brazil's national health organization, the Oswaldo Cruz Institute.

The giant was brought from eastern Africa as a possible profitable substitute for the common garden snail, employed for escargot. A 1988 agribusiness fair in southern Brazil could have triggered the invasion. People were offered kits with snails and brochures with instructions on raising them.

This looked promising: the African giant snails delivered more meat, grew more rapidly, were less pretentious to food and were more resistant to disease than Helix snails. Brazilians started to grow them in their backyards, in order to deliver their stuff to fancy restaurants. But escargot is not popular in Brazil and the few people enjoying the dish were not willing to change the food they were familiar with for a new exotic species, so different in texture and taste.

Thousands of giant snail growers released the snails in the wild, where they thrived.

"If bred in captivity, the snail is unlikely to carry any parasites. But out of rigid control, they can get contaminated," said F?bio Faraco of the Brazilian Environmental Institute.

The snail can spread several pathogens and it is used as an intermediate host for worms that induce severe parasitoses in humans.

"The garden snail, found in some areas of the country, can also carry the same worms," he added.

One nematode worm, Angiostrongylus costaricensis, causes strong abdominal pain, internal bleeding and fever, while A. cantonensis, causes a type of meningitis which in extreme cases induces blindness and paralysis.

Two 2007 meningitis cases in the state of Esp?rito Santo were linked to nematodes coming from the African giant snails. People get the parasites from touching the traces left by the snails on the ground, or feeding on vegetables partially eaten by the snail. A 2007 research led by Thiengo revealed the damage produced by the invader to the environment and that the snail has integrated into the food chain.

"For example, there has been an increase in populations of rats and snakes that eat the snails," said Thiengo.

The giant African has also started to compete with many Brazilian big native snail species, already vulnerable due to habitat loss. While native Brazilian snails lay a few eggs at a time, Achatina has clutches of up to 400 eggs and lays up to 1,200 eggs annually, living up to 10 years (Helix snails live about 4 years).

Experts do not speak about eradication, but control. A national plan was made in 2004, but the suggested control method, picking up the snails by hand and destroying their shells, would mean much more commitment from ordinary Brazilians. Achatina also hides underground for long periods of time (just like Helix), and this hampers the control of the species.

"Everyday I have to collect at least six in my back garden. They like to come out at night, especially when it rains. I can't water my plants at night anymore." said Luiz Roberto Bragan?a of Niter?i, a town close to Rio de Janeiro.