Todayโs path rounds are on ๐๐๐ซ๐๐ฅ๐๐ฉ๐ก๐จ๐ฌ๐ญ๐ซ๐จ๐ง๐ ๐ฒ๐ฅ๐ฎ๐ฌ ๐ญ๐๐ง๐ฎ๐ข๐ฌ, otherwise known as the meningeal worm!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐๐ซ๐๐ฅ๐๐ฉ๐ก๐จ๐ฌ๐ญ๐ซ๐จ๐ง๐ ๐ฒ๐ฅ๐ฎ๐ฌ ๐ญ๐๐ง๐ฎ๐ข๐ฌ is a parasite that primarily affects deer, but can accidentally infect other species as well. It is primarily known for invading into the ๐ฆ๐๐ง๐ข๐ง๐ ๐๐ฌ, the connective tissue protecting the brain.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
The primary species that this parasite infects are white-tailed deer. However, it does not cause very many signs in this species. If the worm accidentally makes it into a red deer, elk, moose, sheep, alpaca or llama however, it can have very significant effects!
๐๐จ๐ฐ ๐๐จ ๐๐ง๐ข๐ฆ๐๐ฅ๐ฌ ๐ ๐๐ญ ๐ข๐ง๐๐๐๐ญ๐๐?
Affected species that show clinical signs are ๐๐๐๐ซ๐ซ๐๐ง๐ญ ๐ก๐จ๐ฌ๐ญ๐ฌ, or animals that were not supposed to get the worm in the first place. P. tenuis eggs are shed in the feces of infected deer and develop into larvae, where they are picked up by an ๐ข๐ง๐ญ๐๐ซ๐ฆ๐๐๐ข๐๐ญ๐ ๐ก๐จ๐ฌ๐ญ, like a snail or slug. In the intermediate host, the larvae develop further and become infectious to mammals, and are excreted in the snail or slugโs mucus trail. The larvae are ingested by the aberrant host where it migrates from the stomach to the spinal cord, and eventually to the brain.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
The brain and spinal cord isnโt supposed to have worms around it! The larvae cause damage to the nervous tissue as the migrate, which leads to clinical signs. In ๐๐๐ฆ๐๐ฅ๐ข๐๐ฌ (the species family of llamas and alpacas), you may see lameness, incoordination, weakness, head tilt, blindness and circling.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Unfortunately, there are no ๐๐ง๐ญ๐๐ฆ๐จ๐ซ๐ญ๐๐ฆ (before death) tests available to identify this worm. So typically, a diagnosis is based on the clinical signs, as well as a history of exposure to deer.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Suspect cases are treated with anti-inflammatory drugs to try and reduce damage caused by the worms, and anti-parasitic medication to hopefully kill the worms directly. Unfortunately, the prognosis is quite poor, so animals are often euthanized if they do not respond to treatment.
๐๐จ๐ฐ ๐๐๐ง ๐ข๐ญ ๐๐ ๐ฉ๐ซ๐๐ฏ๐๐ง๐ญ๐๐?
Prevention is key for this disease, and is focused around preventing exposure to snails and slugs. Animals should be kept away from swampy areas, streams and ponds, and should have gravel paths on frequently travelled areas to reduce mud. Deer-proof fencing to prevent deer from entering the livestock areas can also help.
๐๐ก๐จ๐ญ๐จ๐ฌ
1) The life cycle of Parelaphostrongylus tenuis.
2-5) Examples of meningeal worms as seen at necropsy.
6-7) Cross-sections of meningeal worms seen on histology!
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 1. Sixth Edition.
Purdy, S.R. Meningeal worms in camelids. CDLE Newsletter, Vol 14:1 Fall 2010.
Photo 1 courtesy of S.R. Purdy.
Photos 2-7 courtesy of Noahโs Arkive.
