A survey of gastrointestinal nematode species in red deer (Cervus elaphus) farms in New Zealand using PCR.

Gastrointestinal nematodes are recognised as an animal health issue for farmed red deer. The aim of this study was to explore the range of species infecting farmed deer herds and their farm-level prevalence in New Zealand. Faecal samples were collected from 12-24-month-old deer (n = 6-26; mean 19) on 59 farms located in the North (n = 25) and South (n = 34) Islands. Sub-samples of faeces were pooled by farm and cultured to recover third stage larvae. Twenty four larvae were randomly selected and identified to species using a multiplex PCR (total = 1217 larvae). At farm-level the most prevalent nematodes were Oesophagostomum venulosum 83% (n = 49) and the deer-specific nematodes in the subfamily Ostertagiinae (=Ostertagia-type) including, Spiculoptera asymmetrica 73% (n = 43), Ostertagia leptospicularis 47% (n = 28), Spiculoptera spiculoptera 47% (n = 28). The recently identified Trichostrongylus askivali was present on 32% (n = 19) of the farms and Oesophagostomum sikae on 17% (n = 10). In the analysis of the total number of larvae identified, the proportion was in similar order, 45% (n = 548) were O. venulosum, 14% (n = 173) S. asymmetrica, 10% (n = 124) S. spiculoptera, 9% (n = 114) O. leptospicularis, T. askivali, 3% (n = 40) and only 2% were O. sikae (n = 20). This study is the first to show the farm-level prevalence of nematode species in deer in New Zealand and the first to use PCR as a diagnostic tool. It provides data consistent with cross-infection from sheep/cattle to deer, and provided tentative insights into the proportions of the main GIN species across the deer population including O. sikae and T. askivali which have only recently been identified in New Zealand.

Establishment rate of cattle gastrointestinal nematodes in farmed red deer (Cervus elaphus).

Red deer can be infected with some gastrointestinal nematodes (GIN) of cattle but it is unknown to what extent. An indoor study was conducted to determine the establishment rate of cattle GIN in young deer. Five young calves and 5 young red deer were used. They were effectively treated with anthelmintics when housed and then infected 2 weeks later. After four weeks they were killed for total worm counts. Establishment rates were assessed comparing worm counts to the infective dose which were identified morphologically, and to the relative establishment rate of different species. The establishment rates (%) in cattle and deer respectively were H. contortus (8.0, 18.7, p=0.18), Ostertagia ostertagi (30.8, 0.7, p<0.001), Cooperia spp. (72.3, 2.3, p<0.001) and Trichostrongylus spp. (19.0, 25.3, p=0.12). The majority (>98%) of Trichostrongylus spp. were Trichostrongylus axei in both hosts and there were no differences between hosts for this species (p=0.11). In cattle >98% of Cooperia were Cooperia oncophora and the mean burden was much higher than in deer (p<0.01) where there were similar proportions of Cooperia oncophora, Cooperia punctata and C. curticei. Small numbers of Oesophagostomum venulosum were also present with 3X as many found in deer as in cattle (p<0.05). This study has shown that some cattle-origin GIN can establish in red deer. In particular, the establishment of H. contortus and T. axei could allow sufficient burdens to build up to be clinically significant. Importantly, almost no cattle Ostertagia species or small intestinal species established in deer.

Establishment rate of sheep gastrointestinal nematodes in farmed red deer (Cervus elaphus).

To investigate the establishment of sheep gastrointestinal nematodes (GIN) in red deer, five red deer and five sheep aged 5-6 months were challenged with a mixed burden of sheep GIN at a rate of 327L3/kg bodyweight. The LSmean (SE) establishment rates (%) for Haemonchus contortus, Teladorsagia circumcincta, Cooperia curticei, Trichostrongylus spp. and Oesophagostomum+Chabertia spp. were 18.6 (0.03), 35.5 (0.04), 30.7 (0.04), 74.9 (0.05), 19.9 (0.06), respectively in sheep and 10.5 (0.03), 1.0 (0.04), 0.1 (0.04), 1.0 (0.05), 4.8 (0.06) respectively, in deer. Establishment rates were significantly different (p<0.05) between hosts for all genera. No Trichostrongylus colubriformis or Trichostrongylus vitrinus were seen in any deer but were present in all sheep. Trichostrongylus axei were seen in both hosts but there were relatively more which established in sheep than in deer (p<0.01). No Chabertia ovina were seen in any deer but were present in four of five sheep in low numbers. The only species of Oesophagostomum seen in either host was Oesophagostomum venulosum. These results suggest that the sheep GIN most likely to infect red deer grazing the same pastures are H. contortus, T. axei and O. venulosum.