Acute Mareks disease is an epidemic in a previously uninfected or unvaccinated flock, causing depression, paralysis, and death in a large number of birds (up to 80%). The age of onset is much earlier than the classic form; birds are four to eight weeks old when affected. Infiltration into multiple organs/tissue is observed. Ocular lymphomatosis causes lymphocyte infiltration of the iris (making the iris turn grey), unequal size of the pupils, and blindness. Cutaneous Mareks disease causes round, firm lesions at the feather follicles. Atherosclerosis is induced in experimentally infected chickens. Immunosuppression is impairment of the T-lymphocytes resulting from Mareks disease, preventing a competent immunological response against pathogenic challenge, with the affected birds become more susceptible to disease conditions such as coccidiosis and Escherichia coli infection. Furthermore, without stimulation by cell-mediated immunity, the humoral immunity conferred by the B-cell lines from the Bursa of Fabricius also shuts down, thus resulting in birds that are totally immunocompromised. Diagnosis
Diagnosis of lymphoid tumors in poultry is complicated due to multiple etiological agents capable of causing very similar tumors. It is not uncommon that more than one avian tumor virus can be present in a chicken, thus one must consider both the diagnosis of the disease/tumors (pathological diagnosis) and of the virus (etiological diagnosis).
Median raphe cysts are a cutaneous condition of the penis due to developmental defects near the glans. : 682

See also
Cutaneous columnar cyst
List of cutaneous conditions


== References ==