Longitudinal study for monitoring of gastrointestinal nematode (Trichostrongylidae) infection in naturally infected fenced sika deer (Cervus nippon), fallow deer (Dama dama), red deer (Cervus elaphus) and European bison (Bison bonasus) in Lithuania

Abstract

The European bison and deer are frequently infected with trichostrongylid nematodes. However, information on the seasonal changes of infection that could be used as the basis for sustainable preventive measures is scarce. The faecal egg output and subsequent contamination of pastures with infective trichostrongylid third stage (L3) larvae of Ostertagia spp., Cooperia spp., Oesophagostomum spp. in naturally infected animals was examined during the year. A herd of 290 sika deer, 300 red deer, 200 fallow deer and 15 European bison of different age, grazing for the full year on the enclosed pastures, naturally contaminated with trichostrongylid nematodes were examined. All animals were supplementary fed at different times. The calves grazed together with adults throughout the study. Every two-four weeks herbage and fresh faecal samples were randomly collected. L3 larvae from grass samples were isolated (Fernandez et al. 2001), differentiated and counted. Each of 5-10 deer samples of the mid–sized elongate (approx. 8 x 15 mm; hind) and small (approx. 6 x 11 mm; calf) fresh pellets were collected separately. Large rounded (approx. 12 x 15 mm; stag) pellets (Herczeg 1983) were avoided. The eggs per gram of faeces (EPG) were enumerated using a McMaster technique (Roepstorf and Nansen 2000). Faecal cultures were established and L3 larvae were obtained on few occasions (Henriksen and Korsholm 1983). Eleven harvested sika deer were necropsied and examined for the presence of gastrointestinal nematodes (Satrija and Nansen 1993). The EPG of sika deer hind faeces was elevated in the May during the peri–/post–parturient period resulting in the elevated contamination of pastures with L3 larvae of Ostertagia spp. in June until the middle of September. This was the source for infection of calves resulting in delayed EPG output during September to November. Hence the highest risk of infection was in early born calves graz [...].