ABSTRACT
Newcastle disease virus (NDV) remains a constant threat to the poultry industry. There is scarce information concerning the pathogenicity and genetic characteristics of the circulating velogenic Newcastle disease virus (NDV) in Egypt. In the present work, NDV was screened from tracheal swabs collected from several broiler chicken farms (N = 12) in Dakahlia Governorate, Egypt. Real-time reverse transcriptase polymerase chain reaction (RRT-PCR) was used for screening of velogenic and mesogenic NDV strains through targeting F gene fragment amplification, followed by sequencing of the resulting PCR products. The identified strain, namely, NDV-CH-EGYPT-F42-DAKAHLIA-2019, was isolated and titrated in the allantoic cavity of 10 day old specific pathogen-free (SPF) embryonated chicken eggs (ECEs), and then their virulence was determined by mean death time (MDT) and intracerebral pathogenicity index (ICPI). The pathogenicity of the identified velogenic NDV strain was also assessed in 28 day old chickens using different inoculation routes as follows: intraocular, choanal slit, intranasal routes, and a combination of both intranasal and intraocular routes. In addition, sera were collected 5 and 10 days post inoculation (pi) for the detection of NDV antibodies by hemagglutination inhibition test (HI), and tissue samples from different organs were collected for histopathological and immunohistochemical examination. A series of different clinical signs and postmortem lesions were recorded with the various routes. Interestingly, histopathology and immunohistochemistry for NDV nucleoprotein displayed widespread systemic distribution. The intensity of viral nucleoprotein immunolabeling was detected within different cells including the epithelial and endothelium lining, as well as macrophages. The onset, distribution, and severity of the observed lesions were remarkably different between various inoculation routes. Collectively, a time-course comparative pathogenesis study of NDV infection demonstrated the role of different routes in the pathogenicity of NDV. The intranasal challenge was associated with a prominent increase in NDV lesions, whereas the choanal slit route was the route least accompanied by severe NDV pathological findings. Clearly, the present findings might be helpful for implementation of proper vaccination strategies against NDV.
ABSTRACT
We aimed to investigate the combined effect of organochlorine pesticides heptachlor (HEP) and hexachlorobenzene (HCB) by using a medium-term rat liver bioassay. Male F344 rats were initially administered diethylnitrosamine (DEN, 200mg/kgi.p.); after a 2-week non-dosing period, they were given diets containing HEP (5 or 25ppm), HCB (70 or 350ppm), or their mixtures (5 and 70ppm or 25 and 350ppm) for 6weeks. All rats were subjected to partial hepatectomy at week 3 and killed at week 8. We observed additive or synergistic effects of HEP and HCB in groups treated with mixtures of these pesticides. Number and area of preneoplastic foci positive for glutathione S-transferase placental form (GST-P) were consistently higher in these groups than the sum of individual values in the groups treated with HEP or HCB alone. Consistent with these findings, HEP and HCB had additive or synergistic effects on cell proliferation induction within the preneoplastic foci and cytochrome P450 (CYP) 2B1 and 3A1 induction, which may lead to more efficient metabolic activation of HEP and HCB. On the basis of these findings, we conclude that HEP and HCB have additive and synergistic effects on the development of GST-P-positive foci and that higher risks are associated with a combination of residual organochlorine pesticides in foods than with individual residual organochlorine pesticides.
