For some reason they are called Japanese snails in our part of the globe.
It must have been brought to the Pacific Islands, including the Philippines, during WWII by the Japanese to be propagated as part of their source for food sustenance.
Thus, the history of the Japanese snails in the country is as long and akin to the dark days of the Japanese occupation before liberation from the Americans happened.
But, they are actually the same infestation that is causing havoc in yards and gardens in South Florida, especially when they start devouring plants and other greens – either newly planted or transplanted – that are in the way of their path.
They can also make look the outer walls of the house dirty when they start slowly climbing up and leaving in its wake not only their slime, but also their excrement that coat walls and pavement when it hardens up.
Only, South Florida calls them for what they really are – giant African snail (Achatina fulica) – which can grow as big as a rat and gnaw through stucco and plaster for the calcium content they need for their shells.
One way I have learned of effectively killing these pests, other than crushing them, is by pouring salt on them. They seem to shrink from oozing too much fluid and die.
They seem to be copulating all the time, which is the reason why they cannot be eradicated fast, with the female storing countless eggs inside her body.
In some Caribbean countries, such as Barbados, which is said to be overrun with the creatures, the hard, matured snails’ shells blow out tires on the highway and turn into hurling projectiles from lawnmower blades
For an interesting and educational read about these giant African snails and the disease it carries with them that could be inflicted on people, let me invite you to open up this link: http://colintyner.wordpress.com/2010/07/10/giant-african-snails-an-ecology-of-an-aggressor/