Transmittance of Chronic Wasting Disease in White-Tailed Deer through the Courtship Ritual

Abstract

Chronic Wasting Disease is a transmissible spongiform encephalopathy specific to Cervidae, and there has been increasing concern for the white-tailed deer of Wisconsin since 2001. The Department of Natural Resources and other scientists have been studying how the disease is transferred through the white-tailed deer population in efforts to determine potential ways to reduce its spread. Transmissible spongiform encephalopthies are diseases that affect the nervous system of humans, bovine and particular species of Cervidae. The illness is caused by the mis-folding of proteins; the prions cause masses to form within the tissue creating a sponge-like appearance. The clinical symptoms generally include dementia, lack of coordination, and eventual loss of brain function. Visible signs of Chronic Wasting Disease are apparent only in the last stages of the disease, and include an abnormal pelt, lack of muscle mass and fat storage and the individual carrying head and torso lower than spine. Studies of relatable diseases suggest that urine, feces, blood by transfusion, and saliva can all be possible factors of transmittance. Many forms of deer behavior can be under-lying factors for CWD contraction. For example, white-tailed bucks will slurp urine of females in rutting season to determine if a doe has entered estrus and is viable to mate, and this might increase CWD transmission if it is transferred via urine. Also if urine is the mechanism of transfer, populations with lower male to female ratios are expected to have higher infection rates among males because males will be mating with more females, increasing risk of contraction through the mating ritual. This hypothesis is supported by the fact that the prevalence of CWD from the years 2002 to 2008 indicates that males are infected almost double the amount than female deer are infected despite the consistently closer proximity of females throughout the year. Using data from the 2009 Wisconsin deer hunting season sex ratios and population densities of CWD infected deer were compared between two locations. The two locations spanned over three counties; Iowa, Dane, and Rock county where a total of 1,620 deer were tested for CWD. While studying these forms of transmittance it was expected to find male CWD infection rates to be higher than females; which was found to be true in both sites; CWD-MZ 77A and CWD-MZ 70A.