Testicular atrophy in a mule deer population

Area of Science:

• Wildlife biology
• Reproductive endocrinology
• Environmental toxicology

Background:

• Mule deer (Odocoileus hemionus) populations at the Hanford Site exhibit reproductive abnormalities.
• Previous studies have not documented such high prevalence or geographical confinement of testicular atrophy in wild deer.

Purpose of the Study:

• To investigate the prevalence and characteristics of testicular abnormalities in male mule deer at the Hanford Site.
• To determine the potential causes and physiological impacts of these reproductive issues.

Main Methods:

• Monitoring and capture of adult male mule deer for physical examination and biological sampling.
• Analysis of antler morphology, testicular development, serum hormone levels, and pathogen serology (Brucella spp., EHDV-2, BTV-11).
• Comparison of affected and unaffected deer regarding age, hormonal profiles, and disease markers.

Main Results:

• 23% of monitored male mule deer displayed abnormal antlers and testicles.
• Testicular atrophy, leading to permanent sterility, was prevalent, particularly in deer over 5 years old.
• Affected males showed decreased testosterone and compensatory increases in luteinizing hormone and follicle-stimulating hormone.
• Higher seropositivity for epizootic hemorrhagic disease virus (EHDV-2) and bluetongue virus (BTV-11) was observed in affected deer.

Conclusions:

• The observed testicular atrophy in Hanford Site mule deer is severe and geographically localized, suggesting factors beyond typical age-related changes or common environmental toxins.
• Hormonal pathway disruption and potential viral co-infections (EHDV-2, BTV-11) are implicated in the reproductive impairment.
• Further research is crucial to understand the full impact on the mule deer population's reproductive capacity and identify specific etiological agents.