Submitted to: Avian Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/1/2001
Publication Date: N/A
Citation: Interpretive Summary: Marek's disease (MD), a virus-induced cancer-like disease of chickens, is considered as a major disease problem in commercial poultry. Vaccination has dramatically reduced the incidence of the disease, but very little is known about transient paralysis (TP), a related manifestation of the disease. The objective of this research was to distinguish TP from other types of the disease. We have determined that TP can be distinguished from other types of MD by the use of virus strains modified by different numbers of culture passages. This important information about the development of MD will help scientists in academia and industry understand the different types of the disease and eventually lead to better control of the disease.
Technical Abstract: Inoculation of 15x7 chickens with strain 648A (vv+MDV) at different passage levels (between 10 and 100) showed that two neurological syndromes (transient paralysis and persistent neurological disease), were attenuated at different passage levels. While strain 648A lost the ability to induce transient paralysis (TP) between 30 and 40 passages in chicken embryo fibroblast (CEF) and appeared closely related with all parameters of MDV infection involving viral replication (early cytolytic infection in lymphoid organs and viral replication in the feather follicle epithelium), ability to induce persistent neurological disease was lost between 80 and 90 passages in CEF, coincident with the loss of neoplastic lesions in peripheral nerves and other visceral organs. These data strongly suggest that transient paralysis and persistent neurological disease are not related to each other and seem to be differently regulated. The use of viruses at different passage levels with varying degrees of attenuation is presented, thus, as a useful tool for studying pathogenesis of MDV infection.