This is upsetting to watch. This is a video of a moose with “brainworm”, or Paralaphostrongylus tenuis. This is a parasite that infects a few cervines, mostly moose, deer, elk, and caribou, with white-tailed deer being the species most commonly infected.
The parasite starts out when infected feces is eaten by slugs in snails. A deer will come around grazing and might accidentally slurp up an infected slug. The parasite then finds a comfy home in the deer’s brain:
When larvae hatch, they get into tiny blood vessels and travel on down to the lungs. After that, they move up the respiratory system and into the throat, which the deer coughs up and then swallows. They go through the gastrointestinal tract and then are shit out, leaving infected feces for slugs, snails, and other cervines to eat. The deer who eats the feces/slug will have the parasite enter through the intestinal wall, crawl up the spinal cord and grow in the brain.
Because of how this parasite is transmitted, it’s extremely common where white-tailed deer are plentiful, and so culling is incredibly important. Animals who become infected with brainworm show signs in just a few days, and usually die a few months later.
This is also why elk and moose re-introductions into more southerly parts of the US has pretty much failed. Moose and to a lesser extent elk are exquisitely susceptible to neural disease from Parelaphostrongylus being incidental hosts. White-tailed deer, however, live asymptomatically with this parasite as they’re the natural host. Thus it’s a sort of “biological weapon” deer have against other cervids in the south.
I don’t have much interest in deer diseases because they’re done to death in my research group but this parasite is really cool.
Yup :(
I’ve also read that it’s been accidentally introduced into areas where it wasn’t previously, and the soil is now infected.
Very sad