MULE-DEER PLAGUED BY BLINDNESS
One of Dr. Williams' last cases was an unusual cause of blindness in a mule deer. She was presented with the carcass of a recently shot adult male mule deer. Hunters east of Laramie noticed that the animal was blind and stumbling into trees and bushes. The major gross change was severe inflammation of both eyes, primarily keratitis and uveitis. Histologically the uveal tract and anterior and posterior chambers contained large colonies of coccobacilli, with associated necrosis.
Dr. Mills' laboratory isolated Yersinia pestis in pure culture from the media of the eye and from conjunctival sac. Other lesions in the deer were severe necrotizing nephritis, adrenalitis and lymphadentitis. The organisms in tissues stained immunohistochemically for antigens of Y. pestis. The deer was beyond unlucky, since it also tested positive for chronic wasting disease ("every animal is entitled to two diseases" - Dr. Stuart Young). CWD was probably incidental since the animal was in excellent nutritional condition. No lesions were present in brain.
Plague is unusual in big game since ungulates are considered resistant. There is a published report of plague in a free-ranging mule deer in Wyoming,1 an unpublished, laboratory-confirmed case in a mule deer in Montana,2 and bilateral plague-associated necrotizing panophthalmitis in a black-tailed deer in California.3 Ocular plague has been seen in Colorado (Dr. M. Miller, Colorado Division of Wildlife, unpublished observations; see image). As an aside, ocular plague also occurs rarely in people.4
If you are presented with a deer that is blind and hunters ask you if it is safe to eat, bear in mind the possibility that it may be plague. Leviticus had it right: we should not eat sick animals.
Dr. Williams' graduate student, Dave Edmunds, will present this case at the annual meeting of the AAVLD this November. Donal O'Toole/Beth Williams
1. Thorne E. T., Quan, T.J., Williams, E. S., Walthall, T.J., Daniels, D.: 1987, Plague in a free-ranging mule deer from Wyoming. J Wildl Dis 23(1): 155 - 159
2. http://archives.foodsafetynetwork.ca/animalnet/2003/9 2003/animalnet_september_12.htm#PLAGUE
3. Jessup, D. A.; Murphy, C. J.; Kock, N.; Jang, S.; Hoefler, L Ocular lesions of plague (Yersinia pestis) in a black-tailed deer (Odocoileus hemionus columbianus) Journal of Zoo and Wildlife Medicine 20 (3), 1989 p.360-363.
4. Carter, D. B., Ellis, P. P.: 1987, Yersinia pestis endophthalmitis. Am J Ophthalmol 103 (5): 721 - 722.
http://wyovet.uwyo.edu/Newsletters/Vol_6/Iss_3.pdf#search=%22David%20Edmunds%2Ccwd%22