Comparative efficacy of commercial inactivated Newcastle disease virus vaccines against Newcastle disease virus genotype VII in broiler chickens.

Newcastle disease is still causing huge economic losses and devastating outbreaks in poultry flocks despite implementation of extensive vaccination programs. Five commercial broiler chicken groups were established as G1 (non-vaccinated, non-challenged group) and G2 (non-vaccinated, challenged group), and 3 vaccinated challenged groups as G3 (vaccinated with heterologous inactivated Newcastle disease virus (NDV) genotype II (NDV II) vaccine), G4 (vaccinated with homologous inactivated NDV genotype VII (NDV VII) vaccine), and G5 (vaccinated with bivalent (heterologous inactivated NDV II plus H5) vaccine) were used. Challenge test was done using a velogenic NDV genotype VII (vNDV VII) at 28-d olds. Respiratory signs, greenish diarrhea, and obvious post-mortem lesions of vNDV VII appeared in all the challenged birds whether vaccinated or not. In addition, the mortality rate decreased from 93.3% in G2 to 46.7%, 53.3%, and 66.7% in G4, G5, and G3, respectively. Overall, 2 wk postchallenge; body weight loss (%) had increased mainly in G2, with some improvement in chickens in G4 followed by G5 and chickens of G3 showed the least improvement. At 28 d (day of challenge), the highest hemagglutination inhibition values were 4.3 and 5.4 log2 in chickens in G4 and G5, respectively, which increased in all groups after the challenge. Cytokine (IL-6 and IFN-γ) levels were significantly higher (P < 0.05) in the vaccinated groups than that in the non-vaccinated group, especially in G5. Viral shedding in the trachea was higher than that in the cloacal swabs in all vaccinated and non-vaccinated challenged groups with peak shedding on the 6th day post challenge for both swabs, and the lowest viral shedding titers were observed in chickens in G5. Therefore, the use of homologous genotype NDV with inactivated vaccine conferred a higher clinical protection in terms of body weight loss and mortality against vNDV VII challenge in broiler chickens; however, the heterologous vaccine used in G5 induced the highest cell-mediated immune response and hemagglutination inhibition titers with the lowest viral shedding titer.

Effect of experimental Ornithobacterium rhinotracheale infection along with live infectious bronchitis vaccination in broiler chickens.

Ornithobacterium rhinotracheale (ORT), a bacterium causing respiratory tract infection, has led to a significant problem in the intensive poultry production in Egypt. Polymerase chain reaction-amplified 784-bp specific ORT DNA fragments were found in 7 ORT isolates from lungs, air sacs, and tracheas of commercial broilers or layers in Egypt in 2015. The objective of this study was to investigate the role of the live variant IBV 4/91 with ORT infection. A total of 120 14-d-old broiler chickens (Cobb 500) were equally divided into 4 groups for experimental infection in a complete randomized design. Group 1 was infected with ORT strain and live infectious bronchitis vaccine (IBV 4/91) simultaneously; group 2 was infected with the bacterial strain alone; group 3 was vaccinated only with IBV 4/91, and group 4 was the non-vaccinated and non-infected control group. The respiratory signs, post-mortem lesions (tracheitis and pneumonia) and histopathological findings of lungs, trachea, and air sacs in the experimentally infected broiler chickens appeared to be more prominent in the chickens of group 1 than group 2. With respect to body weight, weight gain, feed conversion rate, and Ornithobacterium re-isolation, there was a difference (P ≤ 0.05) among the chickens of group 1 and the other groups. This reveals that the use of live infectious bronchitic vaccines, which is a common practice in the local Egyptian field of production, may concomitantly increase the pathogenicity of ORT in broiler chickens.