media captionJon Ablett, from the UK's Natural History Museum, spoke to the BBC in 2013 after an outbreak of the snails in Florida
Live snails, fresh leaves and a quarter-pound of beef were found this month – not on a plate or grocery store but inside luggage at a Texas airport.
A passenger arriving from Nigeria initially disclosed the dried beef in her suitcase, before adding 15 giant African land snails to her declaration.
The snails, which were handed over to the US Department of Agriculture (USDA), can cause meningitis in humans.
They are illegal to own in the US without a permit.
Giant African land snails are among the most damaging snails in the world.
They are native to West Africa, where they are considered a delicacy
But they're also known to carry a parasite with a rather menacing name: rat lungworm. This parasite can cause meningitis, an inflammatory illness that affects the brain and spinal cord.
More than 2,800 cases of the disease have been reported across 30 countries, according to the US Centers for Disease Control and Prevention (CDC).
In most cases, infected people have mild symptoms, like headaches, a stiff neck, and nausea – or no symptoms at all.
These snails also pose a potentially serious threat to the environment, damaging local ecosystems and buildings. They are known to eat at least 500 types of plants, but if fruits and vegetables aren't readily available, they can turn to tree bark and even paint and stucco on houses.
They're also stubborn guests: once they arrive, they're hard to get rid of.
The species was first found in the US, in southern Florida, in the 1960s, according to the USDA. It took 10 years and $1m (£730,000) to eradicate them.
In 2011, the snails made their return to Florida, and efforts to remove them are again underway.
The process can be a race against the snail's speedy reproductive system. A single giant African snail can produce about 1,200 eggs in a year.
The July discovery by Houston border agents is one of an estimated 250 pests found each day at US ports of entry.