In mid-October 2010, the NYSDEC Wildlife Pathology Unit, which is responsible for diagnosing and monitoring causes of sickness and death in New York State’s animals, examined a two and a half year old male moose exhibiting abnormal behavior in the Town of Steuben, Oneida County. The moose was lying down in a cow pasture and appeared blind; it could not stand when prodded by a DEC Biologist. The moose was subsequently euthanized and submitted to the Wildlife Pathology Unit for necropsy (animal autopsy) where it was diagnosed with brain worm infection (review the case report online).
Brain worm is a nematode (roundworm) called Parelaphostrongylus tenuis that commonly parasitizes white-tailed deer (the definitive host) and typically causes the deer little to no harm. When P. tenuis infects moose, sheep, llamas, or elk it will result in abnormal behavior that leads to loss of body condition and eventual death.
Over the years, several biologists have speculated that New York’s large white-tailed deer population with its attendant P. tenuis infections would limit the population growth of moose in New York; however, this has yet to be seen. The Wildlife Pathology Unit has confirmed brain worm infections in six of 18 moose examined in 2009-2010, which were found in Clinton, Essex, Oneida, Rensselaer, and Saratoga Counties.