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The Complaint

A veterinary visit was requested to a broiler parent egg-production farm to investigate the cause of continuing and serious mortality in birds which were 25 week-old at the time of the visit. Birds with "swollen heads" had been noticed from about 19 weeks of age. Both the lesions and level of mortality were much more serious in the males than in the females. The problem was initially believed to be "Swollen Head Syndrome"