SEASONAL-VARIATION OF THERMOPHILIC CAMPYLOBACTERS IN LAMBS AT SLAUGHTER

A survey of the isolation rate and population size of thermophilic cam pylobacters in lambs at slaughter was carried out to determine the sea sonal variation of thermophilic campylobacters in ovine hosts. Isolati on rates determined by enrichment methods were always higher than thos e using direct plating onto selective agar and showed that Campylobact er could be isolated from 91.7% (n = 360) of samples from the small in testine of the lambs. Enumerations (MPN), done monthly over a 2-year p eriod, averaged 4.00 log 10 (n = 1080, S.D. 0.16)campylobacters g(-1) fresh weight (fw) intestinal contents with some samples giving values higher than 7 log MPN gfw(-1). These results show that the prevalence of thermophilic campylobacters in sheep intended for slaughter is much higher than previously reported. Statistical analyses showed that the re was a significant seasonal periodicity in the Campylobacter populat ions in the small intestines of lambs at slaughter (P = 0.004) but tha t there was no statistical relationship with environmental parameters such as minimum and maximum temperature, rainfall or hours of sunshine . In an analysis along the length of the intestinal tract of lambs, ca mpylobacters were isolated from 80% of small intestine and 30% of rume n samples, but not from the true stomach, large intestine or caecal sa mples. A survey of sheep grazing on salt marsh, fell (upland) and farm pasture showed that the isolation rate of thermophilic campylobacters in fresh faeces was substantially lower (29.3% (n = 420)) than that f rom the small intestine of lambs at slaughter. No significant differen ce (> 0.05) was found between the isolation rate of campylobacters fro m faeces sampled in late spring/early summer and autumn, nor between t he different types of grazing.