Prevalence and diversity of gastro-intestinal nematode infections in British cattle and implications for biosecurity

Gastrointestinal nematodes (GIN) can impact on cattle health and welfare as well as cause economic losses associated with lower productivity but are often overlooked by farmers as a sub-clinical issue. Infections are routinely controlled with prophylactic use of anthelmintics but resistance to the available products has been reported. The prevalence of anthelmintic resistance (AR) in cattle GIN is advancing in certain species, making control more challenging. This study shows the current prevalence and diversity of GIN populations in British commercial cattle herds and the extent of infection in traded animals. Faecal samples were collected from 455 cattle herds; 395 from groups being sold through livestock auctions and a further 60 from samples submitted to the Animal and Plant Health Agency (APHA) for monitoring purposes. Faecal egg counts (FEC) were conducted on all samples and nematode eggs recovered for molecular species identification using Illumina MiSeq. Of the traded cattle, 67% had a positive faecal egg count, with a mean FEC of 20 eggs per gram (epg) (95% CI: 11 - 34). Samples from APHA had a mean FEC of 72 epg (95% CI: 56-93). Ostertagia ostertagi and Cooperia oncophora were the most common species identified, with co-infections of these two species found in 87% of samples. A diverse range of additional species were also identified, and these were found to vary with the pedigree status of cattle sampled and geographic location. Our results highlight that most cattle sold at auction were carrying GIN, which included a high prevalence of the pathogenic species O. ostertagi. These findings stress the need for effective biosecurity measures for new and returning cattle to minimise the movement of GIN between farms.