Antimicrobial stewardship
Evidence of the effectiveness of interventions designed to enhance antimicrobial stewardship (AMS) is essential. A review by Gozdzielewska et al (2020) (Preventive Veterinary Medicinedoi.org/10.1016/j.prevetmed.2020.105025) summarises for the first time the extent, range, and nature of global research activity on approaches for improving AMS in farmers and veterinarians involved in livestock farm animal management, health and wellbeing.
In November 2017 AGRICOLA, CAB Abstracts, EMBASE, MEDLINE, VetsRev and the Web of Science were searched. Studies were selected by two reviewers with 30% of excluded and all included studies being independently reviewed by another reviewer. Inclusion criteria were primary studies or literature reviews focusing on antimicrobial use (AMU) in farming or veterinary practices for food-producing animals. Outcomes were changes in, or factors influencing farmers' or veterinarians' AMS. Study characteristics and relevant outcomes were extracted, identified facilitators and barriers grouped into categories, and a narrative synthesis was conducted. Fifty-two studies were included in the review; seven were intervention studies and 45 were studies of facilitators and barriers of AMU or antimicrobial prescribing (AMP). Studies were predominantly from high-income countries with only seven studies from lowor middle-income countries. Evidence for effective interventions was limited in terms of number of studies and robustness of evidence. There was some effect for an educational intervention in European cattle farmers and the Yellow Card scheme for Danish pig farmers. Significant facilitators to veterinarians' prudent AMP, in the cattle and pig livestock sector, included education, veterinarians' positive attitudes towards AMU reduction, and diagnostics. For farmers, significant facilitators to reduction of AMU were most frequently related to farming management practices. This review summarises the evidence on the effectiveness of interventions and significant facilitators to farmers' and veterinarians' AMS, which can provide best currently available evidence to guide improvements in different livestock sectors.
Bovine viral diarrhoea virus in Ireland
A compulsory national bovine viral diarrhoea virus (BVDV) eradication programme commenced in Ireland in 2013. Since then considerable progress has been made, with the animal-level prevalence of calves born persistently infected (PI) falling from 0.67% in 2013 to 0.06% in 2018. The herd-level prevalence fell from 11.3% in 2013 to 1.1% in 2018. In the Irish programme, herds in which all animals have a known negative status and which have not contained any PI animals for 12 months or more are assigned a negative herd status (NHS). While considerable progress towards eradication has been made, PI calves have been identified in a small proportion of herds that had previously been assigned NHS. Given this context, a case-control study was conducted by Barrett et al (2020) (Preventive Veterinary Medicinehttps://doi.org/10.1016/j.prevetmed.2020.104990) to investigate potential risk factors associated with loss of NHS in 2017. 546 herds which had NHS on 1 January 2017 and lost that status during 2017 (case herds) were matched with 2191 herds (control herds) that retained their NHS status throughout 2017. Previous history of BVD infection, herd size, herd expansion, the purchase of cattle including potential Trojan cattle and the density of BVD infection within 10 km of the herd emerged as significant factors in a multivariable logistic regression model. This work adds to the evidence base in support of the BVD eradication programme, particularly establishing why BVD re-emerged in herds which had been free of BVD for at least the previous 12 months prior to the identification of a BVD positive calf. This information will be especially important in the context of identifying herds which may be more likely to contain BVD positive animals once the programme moves to herd-based serology status for trading purposes in a post-eradication phase.
Parasite coinfection
Polyparasitism occurs when animals harbour multiple parasites concomitantly. It is a common occurrence but is generally understudied. Fasciola hepatica and Echinococcus granulosus frequently coinfect cattle. The effects of this particular type of polyparasitism are not well documented. The metacestode of E. granulosus is surrounded by the adventitial layer, which constitutes the host immune response to the parasite. This layer in cattle is produced by a granulomatous reaction and is involved in echinococcal cyst (EC) fertility. Due to the systemic immune-modulating abilities of F. hepatica, coinfection possibly generates a favourable environment for EC growth. In a study by Hidalgo et al (2020) (Veterinary Researchdoi.org/10.1186/s13567-020-00799-5) a total of 203 E. granulosus cysts were found in 82 cattle, of which 42 ECs were found in 31 animals coinfected with F. hepatica. The overall infection intensity was three cysts per animal. Coinfection with F. hepatica decreased the mean infection intensity to 1.4 cysts per animal. Regarding EC size, coinfection resulted in smaller ECs (15.91 vs 22.09 mm), especially for infertile lung cysts. Although coinfection was not statistically associated with EC fertility, the study did not find fertile cysts in the livers of coinfected animals. The authors concluded that coinfection with F. hepatica and E. granulosus has a detrimental effect on ECs, particularly infertile cysts.