One-day-old White Leghorn and broiler chicks with maternal antibody to turkey herpesvirus (HVT) were vaccinated with 300 or 1,000 plaque-forming units (PFU) of cell-free or cell-associated HVT vaccine and challenged with virulent Marek's disease virus (MDV) by contact exposure. Broiler chicks receiving 300 PFU of cell-associated HVT had a 3.3% incidence of MD lesions, whereas only 2.0% of those receiving 1,000 PFU had macroscopic lesions. Broiler chicks vaccinated with 300 PFU of cell-free vaccine had 6.8% gross lesions, and 0.67% of the birds receiving 1,000 PFU had MD lesions. Unvaccinated broiler chickens had a 28.3% incidence of MD lesions. Unvaccinated White Leghorn chickens had a 48.9% incidence of macroscopic lesions, whereas 5.4% of the birds receiving 300 PFU of cell-associated HVT had gross lesions, and 8.3% of the birds vaccinated with 1,000 PFU had lesions. In contrast, 6.7% of the chicks vaccinated with 300 PFU of cell-free HVT had MD lesions, and only 4.0% of those receiving 1,000 PFU of cell-free HVT had macroscopic lesions.

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Effect of infectious bursal agent on the response of chickens to Newcastle disease and Marek's disease vaccination.

White Leghorn chickens raised from one day old in an environment contaminated by the infectious bursal agent (IBA) had lower geometric mean titers (GMT) as measured by the hemagglutination-inhibition (HI) test to the Newcastle disease virus (NDV), than control Leghorns reared in an uncontaminated environment. Immunosuppression, defined as a reduction in GMT, was most pronounced at 35-56 days old for Leghorns vaccinated with NDV at 1 and 28 days or at 28 days. In a separate trial with broilers, immunosuppression was similar at 42-56 days old. This study also demonstrated that IBA infection in chickens increased susceptibility to Marek's disease (MD). The unvaccinated control chickens infected with IBA averaged 56.3% MD lesions, whereas unvaccinated controls not exposed to IBA averaged only 18.1% macroscopic lesions. It was also found that 20.7% of the HVT-vaccinated chickens exposed to IBA had gross MD lesions, whereas those HVT-vaccinated chickens reared in an environment free of IBA had 2.99% gross MD lesions.

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Demonstration of Eimeria tenella in bursa of Fabricius of chickens.

Coccidial life-cytle stages were detected in the bursa of Fabricius of broiler chickens inoculated with Eimeria tenella, whether or not the chickens had previously been infected with infectious bursal disease virus (IBDV). Chickens infected only with E. tenella had developing parasites in the lining epithelium, whereas chickens with both infections had gametocytes also in the epithelial cells surrounding numerous degenerating bursal cysts.

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PubMedDate not supplied

Interaction of aflatoxin with infectious bursal disease virus infection in young chickens.

Young White Leghorn chickens fed 2.5 microgram of aflatoxin (Afl) per g of diet from hatching until 4 weeks old and infected with infectious bursal disease virus (IBDV) at 3 weeks old had significantly higher mortality and more severely depressed body weights than chicks with aflatoxicosis or IBD alone. Afl-IBDV chicks also had more extensive gross and microscopic changes characteristic of IBD than did IBDV-chicks. None of the treatments significantly reduced antibody responses to Newcastle disease(ND) and infectious bronchitis vaccines or increased susceptibility to challenge with virulent NDV. In a similar experiment chickens fed Afl from hatching to 7 weeks of age had no marked depression in immune response to ND vaccination.

Aflatoxins↗

PubMedDate not supplied

Effectiveness of cell-free or cell-associated turkey herpesvirus vaccine against Marek's disease in chickens as influenced by maternal antibody, vaccine dose, and time of exposure to Marek's disease virus.

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