In broiler breeder flocks an increase in mortality due to septicaemic infections may be observed over time, with sepsis, endocarditis and arthritis as
the major manifestations. Additionally footpad integrity is seen to decline throughout the production period with suboptimal litter quality and heavy
breeds as predisposing factors. Although the pathogenesis of these infections is not fully elucidated, the aetiology is often Gram positive cocci, such
as Staphylococcus aureus and Enterococcus spp. It is hypothesized that footpad lesions serve as port of entry for systemic or localised bacterial
infections.
In the present study experimental infections with S. aureus and Enterococcus faecalis was made using footpads as port of entry in old broiler
breeders. Two different clinical S. aureus isolates and one E. faecalis isolate where used as inoculum at different doses, by intradermal application
in the central foot pad. Birds underwent full post mortem and bacteriological investigation 3, 7 and 14 days after infection.
Inoculation of the S. aureus resulted in systemic lesions (sepsis, endocarditis and arthritis) as well as injection site abscesses. The lesions and
bacterial re-isolation in the birds receiving the S. aureus originating from bumble foot were restricted to the footpad only. Similar to the S.
aureus the E. faecalis infected birds contracted both systemic and local lesions. Bacterial re-isolation was demonstrated in a pattern similar to the
pathological findings.
Both systemic and local experimental infections were successfully established. Inoculation resulted in systemic lesions (sepsis, endocarditis and
arthritis), corresponding to natural cases under field conditions, as well as injection site abscesses. Apparently, both strain, dose and time
dependent bacteriological and pathological responses in relation to the experimental infection occur.