Rat lungworm disease has a typical life cycle where the worm eggs hatch in the lungs of rats, the larvae are excreted and infect snails or slugs, which are eaten by rats. But the worms can pass on to humans if infected snails are eaten. But other animals, called paratenic hosts, can eat the snails and then infect humans. Such intermediate hosts include freshwater shrimp, frogs, crabs and monitor lizards. Once inside the human body, the worms migrate to the brain, where they eventually die. While symptoms can be mild, infection can cause damage to the central nervous system, including brain inflammation, paralysis and even death. Infected humans cannot pass the disease to other people. Rat lungworm is still considered rare (there have been about 3,000 recorded cases around the world), and the disease is most prevalent in tropical and subtropical regions. In the United States, the parasites are endemic in the Hawaiian Islands; cases of rat lungworm have been reported as far north as Oklahoma.