Effect of Polychlorinated Biphenyls (PCB) on the Infection of Chickens with Turkey Herpesvirus THV-BIO-I

Abstract

The effects of polychlorinated biphenyls (Delor 103) on Brown Hisex chickens infected with vaccination turkey herpesvirus THV-BIO-I were studied in a 5-week experiment. One group of l-day-old chicks were infected in doses of approximately 10· PFU per bird and fed a commercial feed mixture K. Another group of chicks were infected in the same way and fed feed mixture K contaminated with PCB (Delor 103) at 50 mg. kg_ 1 feed mixture. Non-infected chickens fed non-contaminated feed mixture K were used as controls. At weekly intervals the chickens were subiected to serological examination and weighed, and their lymphoid organs, skin, nerves and gonads were examined histopathologically.PCB (Delor 103) produced a reduction in body mass and a disturbance in feather growth. The incidence of lymphoid cellulisates in the organs was not affected. The lymphoid organs of chickens merely infected with THV-BIO-I exhibited only moderate cytolytic changes; atrophy of the spleen and of the bursa of Fabricius were found at the end of the experiment. The lymphoid organs of chickens both infected and fed PCB (Delor 103) showed more conspicuous regressive changes from the 3rd week p. i. These may be a cause of vaccination failure. Post-infection antibody was not found in any of the birds. Brown Hisex chickens were apparently more resistant to the effects of PCB (Delor 103) than Brown Leghorn chickens used in a previous experiment. Brown Hisex chicken, PCB, Turkey herpesvirus THV-BIO-I, lymphoid organs, immunosuppressionThe causes of inadequate protection of poultry after vaccination are related in general to potency of the vaccine and to host and ecological factors. Included among these factors can be the presence of maternal antibody, genetic make-up, incidence of infectious agents of various pathogenicity and immunosuppression of all sorts of origin. In our previous experiments on chickens polychlorinated biphenyls (Delor 103) were found to exert a strong immunosuppressive effect Halouzka et al. 1990) and, combined with simultaneous infection with non-oncogenic Makek's disease viruses (MDV), resulted in a synergic suppressive effect on the lymphoid organs (Halouzka and Jurajda 1991c).Non-pathogenic turkey herpesvirus THV-BIO-I, which is used in our country for vaccination against Marek's disease (MD) (Salaj et al. 1976) induces moderate transient cytolytic changes in the bursa of Fabricius and thymus of susceptible chickens when administered in high doses (Halouzka and Jurajda 1992a). In the organs and tissues it causes the development oflymphoid cellulisates (Benda and Hlozanek 1975;Witter et al. 1976).The present study was designed to characterize the effects of PCB (Delor 103) on the pathogenesis of morphological changes in the organs of experimental chickens infected with THV--BIO-I contained in a commercial vaccine, MARVAK.

Experimental Chronic Intoxication of Chickens with Polychlorinated Biphenyls (Delor 103)

“…The alterations in clinical status, body growth and relative mass of the bursa of Fabricius and spleen correlated with the dose of Delor 103, which is in keeping with the results reported in our previous studies (Halouzka et al 1990;Halouzka and Jurajda 1992).…”