Multi-centric histiocytosis: experimental induction in broiler and specific pathogen-free leghorn chickens

Seventy-five 3-day-old broiler chicks and twenty specific pathogen-free leg horn chicks were injected with 0.5 mi of a homogenate, prepared from organs from broilers diagnosed with naturally-occurring multicentric histiocytosi s (MH), Equal numbers of uninjected broiler and leghorn chicks (controls) w ere maintained in adjacent pens. Ten weeks later, nine broilers had well-de veloped gross and microscopic MH lesions. The distribution and histological appearance of lesions in these experimental chicks was similar to lesions described in naturally occurring field cases. Six leghorns had gross lesion s similar to those found in their broiler counterparts; however, in the leg horns, the cellular masses contained more lymphocytes and, additionally, ma sses were found in the gizzard musculature, One gizzard contained a sarcoma , Broiler chickens with MH weighed less than their control counterparts and were more likely to be anaemic, Sequences specific for reticuloendotheliosis viruses (REV) were found in th e MH homogenate, in organs from most affected experimental leghorns and bro ilers, and in organs from a control broiler, However, REV were not isolated from these tissues, nor were specific antibodies for REV or avian leukosis /sarcoma viruses (ALV) found in chick serum, Leukosis/sarcoma viruses were isolated from some MH-affected experimental leghorns and broilers. Sequence s specific for Marek's disease herpesvirus were not identified by polymeras e chain reaction. The aetiology of MH remains unknown.