Vaccination against Moroccan strains of Newcastle disease virus

Summary Different vaccination programmes commonly used in Moroccan poultry farms were tested for their capacity to protect chickens against two representative Moroccan strains of velogenic viscerotropic Newcastle disease virus under controlled conditions. All vaccination programmes protected the chickens against mortality and the inactivated vaccine gave the highest antibody titres and the best protection against respiratory symptoms.

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Vacunacion Contra Cepas Marroquies Del Virus De La Enfermedad De Newcastle

Resumen Se ensayaron bajo condiciones controladas, diferentes programas de vacunación para detectar la capacidad de estos de proteger pollos contra dos cepas marroquíes representativas del virus velogénico viscerotrópico de la enfermedad de Newcastle. Todos los programas de vacunación fueron efectivos, protegiendo las aves contra mortalidad. La vacuna inactivada fue la mejor, produciendo los títulos más altos de anticuerpos y protegiendo las aves contra síntomas respiratorios.

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Vaccination Contre Les Souches Marocaines Du Virus De La Maladie De Newcastle

Résumé On a testé différents programmes de vaccination communément mis en oeuvre dans les élevages avicoles du Maroc quant à leur capacité de protéger les poulets vis-à-vis de deux souches marocaines représentatives du virus de Newcastle vélogène-viscérotrope. Les poulets ont été protégés dans tous les programmes de vaccination à l'encontre de la mortalité; le vaccin inactivé confère les plus hauts titres en anticorps et la meilleure protection vis-à-vis des symptômes respiratoires.

     

鸡新城疫不同毒株间的交叉保护性研究

将NDV－La Sota疫苗株、NDV山东地方强毒株CY和DY以及NDV F48E8标准强毒株分别制成油乳剂灭活疫苗，免疫6周龄SPF鸡，然后分别用分离强毒株和F48E8强毒株进行攻击。结果发现，两个分离毒株之间、分离毒株与标准毒株之间、IV系疫苗株与分离毒株之间都可以得到完全交叉保护。     

Protection against infectious bursal disease virulent challenge conferred by a recombinant avian adeno-associated virus vaccine

The development and use of recombinant vaccine vectors for the expression of poultry pathogens proteins is an active research field. The adeno-associated virus (AAV) is a replication-defective virus member of the family Parvoviridae that has been successfully used for gene delivery in humans and other species. In this experiment, an avian adeno-associated virus (AAAV) expressing the infectious bursal disease virus (IBDV) VP2 protein (rAAAV-VP2) was evaluated for protection against IBDV-virulent challenge. Specific pathogen free (SPF) birds were inoculated with rAAAV-VP2 or with a commercial intermediate IBDV vaccine and then challenged with the Edgar strain. IBDV-specific antibody levels were observed in all vaccinated groups; titers were higher for the commercial vaccine group. The live, commercial vaccine induced adequate protection against morbidity and mortality; nevertheless, initial lymphoid depletion and follicular atrophy related to active viral replication was observed as early as day 14 and persisted up to day 28, when birds were challenged. No bursal tissue damage due to rAAAV-VP2 vaccination was observed. Eight-out-of-ten rAAAV-VP2-vaccinated birds survived the challenge and showed no clinical signs. The bursa:body weight ratio and bursa lesion scores in the rAAAV-VP2 group indicated protection against challenge. Therefore, transgenic expression of the VP2 protein after rAAAV-VP2 vaccination induced protective immunity against IBDV challenge in 80% of the birds, without compromising the bursa of Fabricius. The use of rAAAV virions for gene delivery represents a novel approach to poultry vaccination.     

Velogenic viscerotropic Newcastle disease virus strains in Morocco

Isolates of Newcastle disease virus (NDV) in Morocco were characterized as velogenic. Two isolates were from tracheal swabs taken at a Moroccan live poultry market, and four isolates were from field cases. Infection of 8-week-old chickens showed that these isolates and previously characterized Moroccan isolates were of the viscerotropic pathotype. Based on hemagglutinin thermostability and the capacity to agglutinate equine erythrocytes, the Moroccan velogenic viscerotropic NDV isolates were classified as belonging to at least three distinct strains.     

Nonspecific innate immunity against Escherichia coli infection in chickens induced by vaccine strains of Newcastle disease virus

The objective was to test the hypothesis that vaccine strains of Newcastle disease virus (NDV) induce nonspecific immunity against subsequent infection with Escherichia coli. White leghorn chickens at 5 wk of age were vaccinated with a NDV vaccine at various days before challenge exposure with O1:K1 strain of E. coli via an intra-air sac route. Immunity was determined on the basis of the viable number of E. coli in the spleen 24 hr after the infection. Roakin strain induced significant (P < 0.05) immunity against E. coli at 4, 6, and 8 days, and La Sota strain at 2, 4, and 8 days, postvaccination. Secondary NDV vaccination administered 14 days later failed to induce immunity against E. coli when chickens were infected 1 or 5 days after the vaccination. Significant (P < 0.05) suppression of this nonspecific immunity was observed in birds treated with corticosterone, 40 mg/kg in feed, given for three consecutive days immediately prior to the bacterial exposure but not in those treated prior to the period. The results indicate that innate immunity induced by the primary NDV vaccination may significantly suppress the multiplication of E. coli in chickens for a period of 2-8 days postvaccination. The NDV-induced immunity was inhibited by corticosterone, which is known to mediate physiological responses to stress.     

Evaluation of a fusion gene-based DNA prime-protein boost vaccination strategy against Newcastle disease virus

Tropical Animal Health and Production - The low potency of genetic immunization has to date impeded development of commercial vaccines against major infectious diseases. The aim of this study was...     

Characterization of Nigerian strains of Newcastle disease virus

Newcastle disease virus was isolated from outbreaks of the disease in vaccinated and unvaccinated poultry flocks representing commercial and backyard farms in different parts of Nigeria. On characterization, all 12 isolates were found to be velogenic.     

Serological response of chickens to oral vaccination with Newcastle disease virus

Conventional Newcastle disease vaccines are not suitable for application to village chickens in tropical countries of Asia. Trials with food-based vaccines are being initiated and the following experiments were performed to evaluate oral vaccination with Newcastle disease virus. Experimental chickens were vaccinated orally with the avirulent V4 strain of Newcastle disease virus and haemagglutination-inhibition antibody responses were measured. V4 virus was introduced into the crop by tube and total faecal output was collected daily and assayed for Newcastle disease virus. Virus was recovered on Days 5 and 6 after vaccination from most chickens that had received 10(7.4) and 10(6.4) 50% egg-infectious doses (EID50) of virus. There was no recovery of virus from birds receiving a lower dose of vaccine. Groups of chickens kept in cages with wire floors were given various doses of vaccine into the crop. Higher antibody titres were achieved with higher doses of virus. This dose responsiveness was not observed when various doses of vaccine were presented on food pellets and the groups of chickens were kept on concrete floors. Similar antibody responses were then seen with nominal doses of 10(5.2) and 10(8.2) EID50 per bird, possibly as a result of excretion and re-ingestion of the vaccine virus. Spread of the vaccine virus was demonstrated when control chickens and chickens receiving 10(7.7) EID50 of V4 virus on food pellets were housed together on a concrete floor. Similar antibody titres were achieved in both vaccinated and in-contact chickens.     

Effect of tuftsin on embryo vaccination with Newcastle disease virus vaccine

The effect of tuftsin of embryo and post-hatch vaccination with NDV-F was studied. The embryo vaccination with NDV-F resulted in more number of dead-in-shell embryos. To overcome this problem, the vaccine was treated separately with ethyl methane sulfate (EMS) and 5-fluorouracil (5-FU) and administered. Treating the vaccine with 5-FU resulted in better hatchability as compared to EMS treatment. In embryo, NDV antibody titres increased upto 2 weeks of age and declined thereafter, whereas in post-hatch vaccination, the antibody titre increased from second to fourth week of age and declined thereafter. The seroconversion was better when the vaccine was given along with tuftsin either to embryos or chicks (post-hatch vaccination) as compared to those vaccinated without tuftsin. Moreover, the percentage of hatchability was more in tuftsin administered groups. It was found that embryo vaccination can ensure definite protection during the early life of the chicks despite the presence of maternal antibodies. In cases where breeder vaccinations do not result in concomitant transfer of antibody to progeny chicks, embryo vaccination would give only neonatal resistance. During the later stages, embryo vaccination did not confer any advantage over post-hatch vaccination.     

Transmissibility of Australian strains of Newcastle disease virus

The transmission of Newcastle disease virus strains from infected to direct-, indirect-, and aerosol-contact groups of chickens was studied. Chickens 7, 21, and 63 days old were used in separate trials. Chicken age and virus strain were found to be important in spread of the virus. Strain V4 spread quickly to all contact groups and was classed as highly transmissible, whereas strain JA failed to infect all contact chickens of each age group, thus spreading less efficiently than strain V4. The viruses spread more readily among the 2 older groups. The significance of the transmissibility of Newcastle disease virus vaccine is briefly discussed.     

Comparison of protection and viral shedding following vaccination with Newcastle disease virus strains of different genotypes used in vaccine formulation

Tropical Animal Health and Production - Newcastle disease (ND) is a devastating disease and cause high t mortality and morbidity in poultry and nonpoultry avian species worldwide. An intensive...