|dc.description.abstract||As a part of an ongoing study of the geographic spread and long term population effects of chronic wasting disease (CWD) in southwestern Saskatchewan, we captured and radio-collared female mule deer (Odocoileus hemionus) in the winter of 2009, 2010 and 2011 and, in the subsequent spring, we captured their newborn fawns. Fawns were blood sampled, radio-collared and ear tagged, released and then continuously monitored for survival status until the following February or March. During the winter capture we also sampled blood, tonsils and feces from juvenile mule deer which were approximately 8 months old. Our primary objectives were to 1) estimate female reproductive indices and evaluate fawn survival rates within the first 8 months of life and 2) detect exposure to selected infectious agents in neonates and 8-month old juveniles.
Pregnancy rate, as determined by ultrasound in 2010 and 2011 winter was 100% (n=84); the overall average number of fetuses per doe was 1.99 ± SD 0.33 (167 fetuses, 84 does) with a predominance of twins. Mean birth rate was 1.29 ± SD 0.72 fawns per doe (139 neonates, 108 does). During the 3 capture years, we captured and radio-collared 118 neonates (n=38 in 2009, n=41 in 2010, n=39 in 2011). Probability of fawn survival was 0.334 ± SD 0.047 for the first 8 months of life from 2009 to 2011 and did not differ among capture years (P = 0.411). The most common known cause of mortality was predation. Having a longer body length at birth reduced the risk of fawn death for 0 - 7 day postpartum period. Members of larger litters had a higher risk of death during 8 – 30 day postpartum period. However, subclinical CWD status of dam was a poor predictor of fawn survival during the first 8 months of life.
We performed various laboratory tests on feces, blood and tonsils of 8-month-old deer to detect prevalence of parasitic agents shed in feces, CWD in tonsils, mule deer lymphotropic herpes virus (mule deer-LHV) in buffy coat and presence of antibody titers in serum to bovine viral diarrhoea virus (BVDV), bovine herpes virus-1 (BHV-1), parainfluenza 3 virus (PI3), and the protozoan parasite Neospora caninum. Fecal analysis revealed a high prevalence for Orthostrongylus sp.: 86% (80/93), and moderate prevalence for Moniezia: 29% (27/93) and Thysanasoma: 29% (27/93). Seroprevalence for BHV-1, BVDV, PI3 virus and Neospora caninum was 3% (3/92), 20% (19/93), 22% (20/93), and 3% (3/91) respectively. Prevalence of mule deer-LHV was 15% (13/85). In 2010 and 2011, we detected subclinical CWD infection in 2 and 1 juveniles, respectively, with an overall prevalence of 3% (3/95). Serology on neonate blood revealed 12% (13/106) were seropositive for N. caninum and all dams that were seropositive for Neospora gave birth to at least one fawn.
Mule deer in the Antelope Creek area of southwestern Saskatchewan have low fawn survival rates which may, in combination with high adult mortality due to hunting or CWD, result in population declines. Given the long incubation of CWD, even a low prevalence of CWD in 8 month old fawns suggests high infection pressure on resident deer. The high prevalence of gastrointestinal parasites and moderate seroprevalence for BVDV and PI3 virus at 8 months of age indicates frequent exposure to pathogens spread via the environment and by direct transmission. Because these are routes of transmission shared by CWD, this moderate to high prevalence of exposure to infectious agents also supports the hypothesis that fawns are potentially exposed to CWD at a young age. To understand factors responsible for the observed annual variability in exposure to Orthostrongylus, BVDV, and PI3 virus requires investigation of these infectious agents in sympatric species including livestock in the area.||en_US