A reassessment of the epidemiology, pathogenesis and prevention strategies of bovine keratoconjunctivitis in Western Cape dairy cattle

Bovine keratoconjunctivitis (BK) is an inflammatory eye condition of cattle that poses significant challenges to animal welfare, dairy and beef productivity, and antimicrobial stewardship in food-producing systems. The principal bacterial agents associated with BK, Moraxella bovis and M. bovoculi, are part of the core ocular surface microbiota in cattle. Rather than behaving as classical infectious agents, these symbionts demonstrate pathogenic potential under permissive conditions, while a range of animal- and herd-level factors modulate disease expression. This research aimed to address the scarcity of epidemiological data on BK in dairy systems and to facilitate evidence-based recommendations for its prevention and control in the Mediterranean climatic zone of South Africa’s Western Cape. A multifaceted investigative framework was employed, integrating a narrative literature review with causal mapping via directed acyclic graphs, analytical validations, and observational studies conducted on commercial dairy herds. Both cross-sectional and prospective cohort designs were used, supported by statistical modelling to define disease patterns and identify associated risk factors. A substantial BK prevalence of 19.4% (95% CI: 15.0–24.8%) was found among dairy cattle exposed to the region’s hot, dry summer conditions. Among heifers, the incidence density rate was 25.1 cases per 100 eye-years (95% CI: 20.7–30.4) over a twelve-month period, peaking at 55.9 cases per 100 eye-years during summer. Neither M. bovis nor M. bovoculi was consistently associated with clinical BK occurrence. Animal-level risk factors included breed, younger age, poor nutritional status, and concurrent facial or palpebral skin conditions such as ringworm. At herd level, intense solar radiation and elevated fly densities were associated with increased BK incidence. Management practices, including open herd strategies, inadequate shade provisioning, increased pyrethroid use in fly control programmes, and infrequent manure removal, were also associated with higher disease levels. No protective effect could be shown for the available vaccine under natural exposure conditions. These findings support a reframing of BK prevention strategies, shifting away from pathogen exclusion and minimalistic, vaccine-centric approaches towards ecologically informed, management-driven interventions. Priority should be given to nutritional resilience, welfare-oriented heifer management, integrated pest control, and judicious pesticide use. Biosecurity policies must acknowledge the microbial connectivity facilitated by tear-feeding insects and the limited efficacy of conventional exclusion measures in controlling commensal organisms with pathogenic potential. Collectively, this work advances a more holistic and context-sensitive framework for safeguarding bovine ocular health within dairy production systems.

Grantor dc:publisher

University of Pretoria

Year dc:date.issued

2025

Advisors dc:contributor.advisor

• Thompson, P.N. (Peter N.)
• Gummow, Bruce

• UCTD
• Sustainable Development Goals (SDGs)
• Bovine keratoconjunctivitis
• Moraxella
• Epidemiology
• Microbiota
• Dairy cattle

Statement dc:rights

• © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Language dc:language.iso

en

DOI

10.25403/UPresearchdata.31205107

Dc Identifier Other

A2026

OAI identifier oai:identifier

oai:repository.up.ac.za:2263/107747