Epidemiologic investigations into pinkeye disease of cattle in Australia

Abstract

Pinkeye (infectious bovine keratoconjunctivitis, IBK) is the most important ocular disease of cattle worldwide and occurs in all regions of Australia. Pinkeye appears in veterinary literature for over 130 years, but knowledge gaps remain, especially about on-farm experiences with the disease. There are discrepancies between theoretical knowledge and clinical experience, exemplified by inability to predict pinkeye outbreaks. This thesis supplies necessary data about pinkeye. Chapter 1 explains why our understanding of pinkeye needs updating and outlines thesis objectives. A literature review informed several peer-reviewed publications, including the Chapter 2 manuscript that examines the diagnosis of pinkeye and offers a world-first disease case definition. Chapter 3 uses a novel method to estimate the incidence and treatment costs of pinkeye. Chapters 4 to 6 describe epidemiologic modelling of data gathered by the second-ever national survey of Australian farmers on pinkeye, and the first online. Chapter 4 models risk factors for pinkeye, Chapter 5 attitudes of farmers to treating pinkeye, and Chapter 6 perceived farm-level impacts of pinkeye. Thesis Chapter 7 reports on a randomised control trial that explored the protectiveness of the only commercial pinkeye vaccine in Australia on extensive beef farms. Chapter 8 reports a pilot pharmacokinetic study on drug levels in calf tears after either cloxacillin ointment or subconjunctival penicillin treatment. Finally, Chapter 9 summarises thesis findings and offers some conclusions and directions for future studies. This dissertation utilises the clinical skills of a veterinarian and epidemiologic methods of a researcher to scrutinize the on-farm experience with naturally-occurring pinkeye in Australia. It offers evidence-based data on disease occurrence, risk factors, attitudes to treatment, farm-level impact, treatment and prevention options. Knowledge supplied in this thesis aims to improve pinkeye outcomes.