Work

Exploration of the prevalence and production impact of Mycobacterium avium subsp. paratuberculosis (MAP) infection in the sheep populations of Great Britain and New Zealand

Year: 2026

Type: article

Abstract: Mycobacterium avium subspecies paratuberculosis (MAP) is a prevalent, obligate pathogen of many wild and domestic species with a global distribution. MAP prevalence, epidemiology and production impact has been extensively studied in cattle whilst comparatively little research has been conducted on sheep. The aim of this project was to assess the prevalence of MAP in Great Britain (GB) and New Zealand (NZ) using faecal PCR and describe the relationship between MAP faecal shedding, reproductive failure (as determined by ultrasound pregnancy diagnosis) and longevity. A total of 162 farms in GB and 76 in NZ were sampled using a combination of individual and pooled faecal sampling frames of which 70% of GB flocks and 88% of NZ flocks tested positive for MAP. MAP shedding was associated with a 3 times increased risk of reproductive failure and significantly higher flock replacement rates in infected flocks. Reproductive failure is an important cause of forced culling in commercial flocks, leading to higher replacement rates and reduced lifetime output per breeding ewe. Excess culling and replacement costs due to preventable infectious disease reduce flock productivity, profitability and negatively impact sustainable lamb production. Effective control measures are available for MAP infected flocks but adoption is hampered primarily, but not exclusively, by poor recognition and underdiagnosis of the disease coupled with a poor awareness of the production limiting nature of the pathogen at the flock level. • MAP is very prevalent in both countries, being present on >60% of farms and infecting high proportions of ewes (up to 80%) in infected flocks. • MAP is associated with reproductive failure in breeding ewes, with MAP prevalence higher and shedding of MAP significantly higher in ewes diagnosed as non-pregnant compared to pregnant by ultrasound scanning. • Accounting for other confounding factors MAP shedding increased the odds of a ewe being diagnosed non-pregnant by OR 3.346 • The longevity of ewes in infected flocks was significantly reduced with a corresponding increase in the replacement rate and associated costs thereof. • The combination of high prevalence and negative associations with reproductive performance and longevity support the authors hypothesis that MAP is an important and underestimated production limiting disease globally and warrants further study to understand its epidemiology and control.

Source: The Veterinary Journal

DOI: 10.1016/j.tvjl.2026.106600

Authors: Laura Worsley, Anne Ridler, Amy Wedley, Joanna Urbaniec, Peers Davies

Institutions: University of Liverpool, Massey University, University of Nottingham

Language: English

Topic: Mycobacterium research and diagnosis

Subfield: Epidemiology

Field: Medicine

Domain: Health Sciences

SDGs: Zero hunger, Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,310