Cellulitis in broiler chickens : studies of the pathogenesis, a diagnostic tool and risk factors

Abstract

Cellulitis in broiler chickens is a subcutaneous inflammation that is caused by the bacterium Escherichia coli. It is one of the main causes of condemnation of broiler carcasses at slaughter in Sweden and elsewhere. The aim of this thesis was to gain more knowledge of the pathogenesis and risk factors of this disease. Samples from cellulitis lesions and organs (n=327) were collected from carcasses at slaughter. By using whole genome sequencing, clonal spread of E. coli strains within some flocks and systemic spread in individual chickens with cellulitis were demonstrated. In two experimental studies, in which E. coli was inoculated subcutaneously to induce cellulitis, clinical signs, immune parameters in blood and the use of infrared imaging as a diagnostic tool were evaluated. Chickens showed clinical signs of varying severity depending on E. coli isolate. Analyses of blood showed that some chickens were bacteraemic post-inoculation. Signs of activated monocytes and increased in vitro adherence to E. coli by heterophils, monocytes and thrombocytes were observed. Infrared thermography did not reliably identify cellulitis. Mixed effect modelling of production data was used to identify risk factors for condemnation due to dermatitis/cellulitis. Identified risk factors were e.g. old parent flocks, late slaughter and slaughterhouse identity. Post-mortem examinations of 491 chickens culled or found dead near slaughter on 10 farms, showed that cellulitis occurred in approximately 9% of the chickens.

In conclusion, E. coli associated with cellulitis can spread systemically at time of slaughter and inoculation of E. coli can cause clinical signs and changes to immune parameters in blood. The occurrence of cellulitis may be underestimated, and a multifactorial approach is probably needed to reduce it.

Keywords

broiler chickens; cellulitis; Escherichia coli; cgMLST; systemic spread; experimental infection model; infrared thermography; immune response; risk factors

Published in

Acta Universitatis Agriculturae Sueciae
2024, number: 2024:57ISBN: 978-91-8046-348-5, eISBN: 978-91-8046-384-3
Publisher: Swedish University of Agricultural Sciences

SLU Authors

• Jonare, Liv

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Clinical Science


Publication identifier

DOI: https://doi.org/10.54612/a.3djgisfr0v

Permanent link to this page (URI)

https://res.slu.se/id/publ/130452