Key clinical signs as well as gross and microscopic features that are most useful for differentiating Mareks disease from lymphoid leukosis and reticuloendotheliosis include:

Age: Mareks disease can affect birds at any age, including <16 weeks of age;
Clinical signs: Frequent wing and leg paralysis;
Incidence: >5% in unvaccinated flocks;
Potential nerve enlargement;
Interfollicular tumors in the bursa of Fabricius;
CNS involvement;
Lymphoid proliferation in skin and feather follicles;
Pleomorphic lymphoid cells in nerves and tumors; and
T-cell lymphomas.In addition to gross pathology and histology, other advanced procedures used for a definitive diagnosis of Mareks disease include immunohistochemistry to identify cell type and virus-specific antigens, standard and quantitative PCR for identification of the virus, virus isolation to confirm infections, and serology to confirm/exclude infections. The World Organisation for Animal Health (OIE) reference laboratory for Mareks disease is Avian Viral Oncogenesis group (led by Professor Venugopal Nair OBE) at The Pirbright Institute, UK.PCR blood testing can also detect Mareks disease, and proper testing can differentiate between a vaccinated bird with antibodies and a true positive for Mareks disease. Mareks disease is not treatable, however, supportive care can help. It is recommended that all flocks positive for Mareks disease remain closed, with no bird being introduced or leaving the flock. Strict biosecurity and proper cleaning is essential, using products like Activated Oxine or Virkon S and reducing dander buildup in the environment. Proper diet, regular deworming and vitamin supplements can also help keep infected flocks healthier. Reducing stress is also a key component, as stress will often bring about illness in birds infected with Mareks disease.
Pimavanserin (ACP-103; BVF-036), sold under the brand name Nuplazid, is an atypical antipsychotic which is approved for the treatment of Parkinsons disease psychosis and is also being studied for the treatment of Alzheimer’s disease psychosis, schizophrenia, agitation, and major depressive disorder. Unlike other antipsychotics, pimavanserin is not a dopamine receptor antagonist. Pharmacology
Pharmacodynamics
Pimavanserin acts as an inverse agonist and antagonist at serotonin 5-HT2A  receptors with high binding affinity (Ki 0.087 nM) and at serotonin 5-HT2C receptors with lower binding affinity (Ki 0.44 nM). Pimavanserin shows low binding to σ1 receptors (Ki 120 nM) and has no appreciable affinity (Ki >300 nM) to serotonin 5-HT2B, dopamine (including D2), muscarinic acetylcholine, histamine, or adrenergic receptors, or to calcium channels.Pimavanserin has a unique mechanism of action relative to other antipsychotics, behaving as a selective inverse agonist of the serotonin 5-HT2A receptor, with 40-fold selectivity for this site over the 5-HT2C receptor and no significant affinity or activity at the 5-HT2B receptor or dopamine receptors. History
Development
Pimavanserin was developed by Acadia Pharmaceuticals. Pimavanserin is expected to improve the effectiveness and side effect profile of antipsychotics.