Simultaneous occurrence of hyphaema and Streptococcus dysgalactiae-bacteraemia in free-ranging Swiss laying hens.

ABSTRACTHyphaema - bleeding in the anterior chamber of the eye - as well as Streptococcus dysgalactiae are rare findings in laying hens. In the herein described report, co-occurrence of hyphaema and S. dysgalactiae bacteraemia was found in free-ranging laying hens derived from two consecutive flocks on the same farm, submitted for necropsy in two batches within 7 months. Hyphaema was found bilaterally in seven laying hens and unilaterally in one of the 11 hens submitted to post-mortem examination. In addition, nine hens showed focal dermatitis. The hens had shown non-specific clinical signs such as apathy, disorientation and decreased laying performance. The farmer reported that all clinically affected birds had died. Bacteriological and histological analyses of the eye and liver supported bacteraemia with multiple vascular thrombi and intralesional Gram-positive coccoid bacteria identified as S. dysgalactiae. Complete genome-based clustering showed that the outbreak strains of S. dysgalactiae cluster most closely with two strains isolated from pigs and one strain from a rhinoceros, but no data were available for other avian strains. The source of the infection was not identified. It is thus unknown whether the herein described laying hens were infected by a strain originating from their skin flora or by strains arising from other animals such as free-ranging birds. Direct or indirect contact between the hens and pigs or cows on the pullet farm could not be excluded.