Managing Gastrointestinal Parasites in Farmed White-tailed Deer Sydney L. Cottingham, Juan M. Campos-Krauer, DVM, PhD Cervidae Health Research Initiative, University of Florida, Gainesville, FL, USA
Introduction Gastrointestinal parasites are ubiquitous on pasture where white-tailed deer are maintained and pose constant infection pressure on farmed herds. Though most infections by gastrointestinal parasites are subclinical or produce only mild clinical disease in ruminant livestock hosts, a few species of parasitic roundworms are capable of causing marked disease and economically significant production loss (Waller 2006; Stromberg and Gasbarre 2006; Charlier et al. 2014; Verocai et al. 2020). One such species is Haemonchus contortus (barberpole worm, large stomach worm), an abomasal (real stomach) roundworm capable of causing disease and mortality in young or immunocompromised deer (Prestwood and Kellogg 1971; Davidson et al. 1980; Forrester 1992). The life cycle of H. contortus and other important nematode parasites of deer includes a free-living larval stage, and all infections with these species are acquired through the ingestion of infective larvae from pasture. Consequently, management of these parasites depends on reducing the number of eggs shed into the environment and reducing subsequent exposure of deer to infective larvae on pastures. Seasonal Parasite Pressure Survival of free-living larvae on pastures is determined by environmental factors, most importantly, temperature and moisture (Waller 2006; Besier et al. 2016). In warm temperate regions such as Florida, warm, wet spring and summer conditions are especially permissive to rapid hatch rates and survival of free-living H. contortus larvae on pasture (Besier et al. 2016). In moist environments, hatch rates increase with temperature. The optimal temperature range for H. contortus egg development and larval survival is 68-86ËšF (Besier et al. 2016).
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