Meningeal Worm

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DISEASE INFORMATION​

​Parasitic Transmission

Adult meningeal worms infect the tissues around the brain and spinal cord of white-tailed deer. They lay eggs, which enter the bloodstream and lodge in the lungs. The eggs hatch into larvae that migrate up the trachea, are swallowed, and exit the body in the deer’s feces. Snails and slugs that come into contact with the feces become infected and serve as intermediate hosts, which is necessary for the parasite’s development. When deer ingest these infected snails or slugs while grazing, the larvae migrate to the spinal cord and brain, completing the life cycle. 

In elk and other unintended hosts, the larvae similarly migrate to the spinal cord and brain, but the parasite cannot complete its life cycle. Instead, the larvae cause severe neurological damage by burrowing into neural tissue. Because the worms cannot reproduce in these hosts, elk are considered aberrant or dead-end hosts

  (The meningeal worm in the meninges inside the skull.)
Photo courtesy of Michigan Department of Natural Resources​

Symptoms

White-tailed deer, as the natural host, show no symptoms of infection. Infected elk, however, may exhibit symptoms such as aimless wandering, circling, listlessness, loss of fear of humans, isolation from the herd, lameness, stiffness, blindness, abnormal head or neck positioning, and paralysis.​

Risk to People and Other Animals

Meningeal worm is a threat to elk and livestock, such as sheep, goats, llamas, and alpacas, but it does not affect people, domestic dogs or cats. Meat from infected animals is safe to eat, provided it is cooked to an internal temperature of of 165°F​ or higher, which kills any parasites, bacteria, or viruses that are present.

​​​Prevention​

Meningeal worm poses a significant threat to elk populations in the eastern U.S., where white-tailed deer are widespread. Controlling its spread is challenging due to the parasite’s complex life cycle, which involves wild hosts such as deer, snails, and slugs. One effective strategy is managing white-tailed deer populations through hunting. Controlled burns can also help reduce both the parasite and its gastropod hosts. Reporting sick or dead deer or elk to Kentucky Fish and Wildlife is crucial for tracking the prevalence of meningeal worms in both whit​