title: Wild deer as potential vectors of anthelmintic-resistant abomasal nematodes between cattle and sheep farms.
abstract: Gastrointestinal (GI) nematodes are among the most important causes of production loss in farmed ruminants, and anthelmintic resistance is emerging globally. We hypothesized that wild deer could potentially act as reservoirs of anthelmintic-resistant GI nematodes between livestock farms. Adult abomasal nematodes and faecal samples were collected from fallow (n = 24), red (n = 14) and roe deer (n = 10) from venison farms and areas of extensive or intensive livestock farming. Principal components analysis of abomasal nematode species composition revealed differences between wild roe deer grazing in the areas of intensive livestock farming, and fallow and red deer in all environments. Alleles for benzimidazole (BZ) resistance were identified in β-tubulin of Haemonchus contortus of roe deer and phenotypic resistance confirmed in vitro by an egg hatch test (EC50 = 0.149 µg ml(-1) ± 0.13 µg ml(-1)) on H. contortus eggs from experimentally infected sheep. This BZ-resistant H. contortus isolate also infected a calf experimentally. We present the first account of in vitro BZ resistance in wild roe deer, but further experiments should firmly establish the presence of phenotypic BZ resistance in vivo. Comprehensive in-field studies should assess whether nematode cross-transmission between deer and livestock occurs and contributes, in any way, to the development of resistance on livestock farms.
authors.affiliation: School of Veterinary Sciences, University of Bristol, , Bristol BS40 5DU, UK, Moredun Research Institute, , Penicuik EH26 0PZ, UK.
authors.forename: C
authors.initials: C
authors.lastname: Chintoan-Uta
authors.forename: E R
authors.initials: ER
authors.lastname: Morgan
authors.forename: P J
authors.initials: PJ
authors.lastname: Skuce
authors.forename: G C
authors.initials: GC
authors.lastname: Coles
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology / Q000627:therapeutic use*; D002417:Cattle / Q000469:parasitology*; D002418:Cattle Diseases / Q000188:drug therapy / Q000469:parasitology / Q000635:transmission*; D003670:Deer / Q000469:parasitology*; D004199:Disease Vectors; D004351:Drug Resistance; D005838:Genotype; D006790:Host-Parasite Interactions; D009348:Nematoda / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D009349:Nematode Infections / Q000635:transmission / Q000662:veterinary*; D012756:Sheep / Q000469:parasitology*; D012757:Sheep Diseases / Q000188:drug therapy / Q000469:parasitology / Q000635:transmission*
chemical_list: D000871:Anthelmintics
keywords: Haemonchus contortus; anthelmintic resistance; anthelmintics; deer; livestock; nematodes