granuloma disease in a flock of free range layers.

Granuloma disease in a flock of free range productive layers in the Netherlands in 2017 is described. The disease resembled granuloma outbreaks in layers caused by in 2013 and occurred in the same area in which the rearing farm considered as the source of the 2013 outbreaks was located. Between 55 and 84 weeks of age mortality was 20.3% (breeder's norm 3.9%). All dead hens examined ( = 20) showed granulomas especially in liver and ceca. Nine hens with or without liver and/or ceca granulomas were examined for trichomonads in mentioned organs by hybridization (ISH), nested PCR, and cloning and sequencing. Ceca were also examined by culture. ISH was positive in all livers and ceca with granulomas and negative in case granulomas were absent. strain 13/16632, which caused the 2013 outbreaks was found in 4/8 hens with granulomas. Moreover, other trichomonads were detected: a strain GPO-like and a sp. strain GABC1-like. Mixed infections also occurred. Infectious causes of granuloma disease other than the afore-mentioned trichomonads could be excluded. Trichomonad DNA was not detected in environmental samples and wild ducks originating from the farm of concern, except for one duck in which the same sp. as in hens was detected, leaving the source of the infection in hens unknown. It is concluded that the herein described granuloma disease likely was caused by strain 13/16632. However, the pathogenicity of the other trichomonads found remains to be clarified.