Isolation and Study of Biological Characteristics of Nononcogenic Chicken Herpesviruses of Mareks-Disease .2. Invivo Characterization

Veterinarni Medicina 37, 1992, 535-542

In a previous paper [J u r a j d a and H a l o u z k a, 1992] the in vitro isolation of two chicken herpesviruses of Marek's disease [M and K strains] was described and results of their characterization were presented. The present paper deals with the in vivo characterization of bath isolates: pathogenicity and immunosuppressive characteristics of isolates were observed in a five-week test period, along with the development and production dynamics of antibodies and viral antigen in the feathers of experimentally infected chickens of the Brown Leghorn breed. A technique of double immunodiffusion in agar gel according to Ouchterlony, modified by W o e r n l f [1966], was used to determine the presence of antibodies to Marek's disease virus [MDV] in blood serum and of precipitating MDV-antigen in feather quills of tested chickens. Isolate multiplication and titration were performed in a system of chicken embryonal fibroblasts [CEF] [J u r a j d a et al., 1984]. Chickens were infected i. m. with three virus doses - 10(2) to 10(4) PFU per chicken while the dose 10(4) corresponded to the titre of 10,800 PFU/0.2 ml for M isolate and to the titre of 8,600 PFU/0.2 ml for K isolate. The nature and rate of regressive changes in lymphatic organs were determined according to criteria described by H a l o u z k a and J u r a j d a [1991]. The results are summarized in Tabs. I and II. Neither of the isolates evoked clinical or pathomorphological macroscopic symptoms of the disease. M isolate induced microscopic MD-specific changes in the peripheral nerves [of C type] and only moderate and transient signs of immunosuppression in 11 % of infected chickens. On the other hand, K isolate did not affect peripheral nerves, but it reduced chicken weight and also the relative weight of bursa Fabricii, including stronger effects on the lymphatic organs of chickens. Both isolates were characterized as nononcogenic and only weakly pathogenic chicken herpesviruses of Marek's disease for sensitive chickens in experimental conditions

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