The Giant African Land Snail (GALS), scientifically known as Lissachatina fulica, is globally recognized as one of the most damaging invasive species. These mollusks are impressive in size, with some individuals reaching up to eight inches in length, about the size of an average adult fist. Despite their seemingly benign appearance, their rapid spread and sheer size conceal a two-fold threat to public well-being and the environment.
The Risk of Rat Lungworm Disease
The most direct threat the GALS presents to human health is its role as a carrier for the parasitic nematode Angiostrongylus cantonensis, commonly known as Rat Lungworm. This parasite’s life cycle involves rats as the definitive host, but the snails and slugs act as intermediate hosts, harboring the infectious larvae. People become infected when they accidentally ingest these larvae, often by consuming raw or undercooked infected snails or slugs, or by eating raw produce contaminated with the parasite’s larvae or the mollusk’s slime trails.
Once ingested, the larvae travel through the body and can invade the central nervous system, where they cause a serious condition known as eosinophilic meningitis. Symptoms of this illness include severe, progressive headaches and neck stiffness, often accompanied by nausea and vomiting. In some cases, neurological symptoms like tingling or painful feelings in the skin (paresthesia) may develop. The infection can occasionally lead to more severe complications, though the parasite cannot complete its life cycle in humans and eventually dies.
In areas where the snails are established, precautions are necessary to prevent infection. Thoroughly wash all fresh produce before consumption to remove any small snails, slugs, or slime trails that may be present. Direct contact with any wild snail or slug should be avoided, and protective gloves should be worn if they must be handled.
Destructive Agricultural and Ecological Impact
The GALS is a formidable invasive species capable of causing massive physical damage to crops and infrastructure. The snail is an extremely opportunistic feeder, documented to consume over 500 different types of plants, including a wide array of agricultural crops and native flora. They target high-value crops like papaya, beans, and various cucurbits, often causing significant yield loss that poses a severe economic threat to local agriculture.
Their reproductive capacity is a primary reason for their invasiveness and destructive potential. These snails are hermaphrodites, meaning a single individual can reproduce without a mate, although they typically mate to produce a clutch of eggs. A single snail can lay up to 1,200 eggs per year, often in clutches of several hundred, allowing a population to explode rapidly in a new location.
The snails also pose a unique threat to human-built structures due to their need for calcium to maintain their large shells. As a result, they have been known to consume non-plant materials like paint, plaster, and stucco from the sides of houses and buildings. This behavior can cause considerable structural damage and increases the financial burden of managing an infestation beyond just crop loss.
Strict Regulatory Controls and Public Safety
Due to the dual public health and environmental risks, the Giant African Land Snail is subject to strict regulatory controls in the United States and many other countries. It is illegal to import, possess, or transport this species within the United States without a specific permit. The U.S. Department of Agriculture (USDA) and the Animal and Plant Health Inspection Service (APHIS) actively enforce these regulations under the authority of the Plant Protection Act.
When an infestation is discovered, such as the recurring outbreaks in Florida, an extensive and costly eradication program is immediately initiated. These efforts often involve a combination of large-scale surveys, physical removal of the snails, and the application of molluscicides like metaldehyde. Eradicating an established population is a lengthy process, exemplified by a recent Florida outbreak that took ten years and millions of dollars to successfully eliminate.
If an individual encounters a GALS, they should not touch or handle it, as the snail’s slime can carry the Rat Lungworm parasite. Instead, authorities like the state agricultural department must be contacted immediately to allow trained personnel to confirm the species and begin quarantine and eradication efforts.