Seropositivity to Campylobacter and association with abortion and lamb mortality in maiden ewes from Western Australia, South Australia and Victoria.

This case-control study investigated associations between Campylobacter fetus or Campylobacter jejuni titre and reproductive outcomes in 22 flocks of Merino and non-Merino maiden ewes aged 1-2 years old. Campylobacter titres were also determined for multiparous ewes aged 3 years or older on the same farms. C. fetus 'positivity' (titre ≥1:80) was detected for 12% (57/462; 95% confidence interval [95% CI] 9.6 to 15.6) of maiden ewes and 31% (65/210; 95% CI 25.0 to 37.4) of mature ewes. The odds for failing to rear a lamb in C. fetus-'exposed' maiden ewes (titre ≥1:10) was 2.01 times that of seronegative ewes (95% CI 1.09 to 3.77; P = 0.027), but there was no association between C. fetus-'positivity' (titre ≥1:80) and failure to rise (OR 1.69; 95% CI 0.77 to 3.76; P = 0.191). C. fetus abortions were confirmed with microbial culture in one maiden ewe flock. In this flock, C. fetus titres fluctuated and often waned by lamb marking, highlighting the value of necropsies during abortion investigations. C. jejuni-'positivity' (titre ≥1:80) was detected for 44% (204/462; 95% CI 39.7 to 48.7) maiden ewes, but odds of failing to rear were decreased for C. jejuni-'positive' ewes (OR 0.52; 95% CI 0.32 to 0.83; P = 0.007). The association between Campylobacter serology and the reproductive outcome was inconsistent in these flocks. Serology should be considered in the context of other risk factors and used in conjunction with other strategies to investigate the impact of Campylobacter exposure on ewe reproductive performance such as monitoring for abortions and lamb necropsies to determine aetiological diagnosis, and vaccination trials.

Factors associated with small lungworm infections in heavily infected sheep in southeast South Australia.

This field observational study describes the seasonal pattern of small lungworm infections under different grazing managements from August 2018 to March 2019. Live weight, lungworm and gastrointestinal nematode infection, as well as pasture type grazed and snail density, were measured at 5 farm visits. Across all visits and mobs, about one quarter to one half of sheep were positive for small lungworm, although prevalence was as low as 0% and as high as 78%. The density of the intermediate host molluscs was greater than 1600 snails/m2 in irrigated perennial lucerne pasture when it was grazed ('Pasture A'), but was low (<300) in non-irrigated perennial pasture ('Pasture B') and non-irrigated forage crop ('Pasture C'). Overall, non-infected lambs had a similar live weight compared with the small lungworm infected lambs (mean difference -0.6 kg; 95% CI -1.6 to 0.2; P = 0.1). The odds ratio of small lungworm infection associated with a twofold increase in worm egg count was 1.7 (95% CI 1.1 to 2.7; P = 0.02). Rather than a distinct seasonal pattern of infection, we found that small lungworm can occur throughout the year, with prevalence most influenced by pasture type (irrigated vs dryland), grazing management and the population density of the intermediate hosts. Importantly, this study suggested that small lungworm infection did not reduce lamb live weights. It reinforced that to improve sheep productivity, well-established determinants of production, such as correct grazing management to optimise pasture quality and strategies to reduce infections with gastrointestinal nematodes, should be the priority of farm managers.

Prevalence, faecal shedding and genetic characterisation of Yersinia spp. in sheep across four states of Australia.

OBJECTIVES: To develop molecular tools for the investigation of the prevalence, species and faecal shedding of Yersinia in sheep. METHODS: A quantitative PCR (qPCR) targeting the ß subunit of the Yersinia spp. RNA polymerase gene was developed and validated. The prevalence of pathogenic Y. enterocolitica was determined by screening for the virulent yst gene. These qPCR assays were used to determine Yersinia spp. prevalence and faecal shedding concentration from 3412 faecal samples collected from approximately 1189 lambs (100-180 lambs/flock) on eight farms across Australia. This was a longitudinal study, with sheep sampled on three occasions (weaning, post-weaning and pre-slaughter). A subset of up to five positive samples from each sampling on each farm (n = 111) was sequenced. RESULTS: Yersinia spp. (including both pathogenic and non-pathogenic species) were identified in all flocks, with 60.7% of lambs shedding Yersinia spp. on at least one sampling occasion. Point prevalence ranged from 4% to 91% across farms and sampling occasions. Median Yersinia spp. bacterial concentration was 1.1 × 10(6) , 2.8 × 10(6) and 5.6 × 10(5) organisms/g faeces at weaning, post-weaning and pre-slaughter, respectively, across all farms. Pathogenic Y. enterocolitica was identified in all eight flocks sampled, with 14.8% of lambs shedding pathogenic Y. enterocolitica on at least one sampling occasion. CONCLUSION: Yersinia spp. and pathogenic Y. enterocolitica in particular were commonly identified in a sample of Australian sheep flocks using molecular techniques. Further studies into associations between faecal shedding of pathogenic Yersinia spp. and sheep productivity or clinical disease may utilise qPCR in conjunction with other diagnostic tools.