Review of Poultry Recombinant Vector Vaccines.

The control of poultry diseases has relied heavily on the use of many live and inactivated vaccines. However, over the last 30 yr, recombinant DNA technology has been used to generate many novel poultry vaccines. Fowlpox virus and turkey herpesvirus are the two main vectors currently used to construct recombinant vaccines for poultry. With the use of these two vectors, more than 15 recombinant viral vector vaccines against Newcastle disease, infectious laryngotracheitis, infectious bursal disease, avian influenza, and Mycoplasma gallisepticum have been developed and are commercially available. This review focuses on current knowledge about the safety and efficacy of recombinant viral vectored vaccines and the mechanisms by which they facilitate the control of multiple diseases. Additionally, the development of new recombinant vaccines with novel vectors will be briefly discussed.

Estudio Recapitulativo- Revisión acerca de las vacunas con vectores recombinantes para la avicultura. El control de las enfermedades en la avicultura se ha basado en gran medida en el uso de varias vacunas vivas e inactivadas. Sin embargo, durante los últimos 30 años, la tecnología de ADN recombinante se ha utilizado para generar nuevas vacunas avícolas. El virus de la viruela aviar y el virus del herpes del pavo son los dos vectores principales que se utilizan actualmente para construir vacunas recombinantes para la avicultura. Con el uso de estos dos vectores, se han desarrollado y están disponibles comercialmente más de 15 vacunas con vectores virales recombinantes contra la enfermedad de Newcastle, la laringotraqueítis infecciosa, enfermedad infecciosa de la bolsa, influenza aviar y Mycoplasma gallisepticum. Esta revisión se enfoca en el conocimiento actual sobre la seguridad y eficacia de las vacunas con vectores virales recombinantes y los mecanismos por los cuales facilitan el control de múltiples enfermedades. Además, se discutirá brevemente el desarrollo de nuevas vacunas recombinantes con nuevos vectores.

Evaluation of vaccination against infectious laryngotracheitis (ILT) with recombinant herpesvirus of turkey (rHVT-LT) and chicken embryo origin (CEO) vaccines applied alone or in combination.

The chicken embryo origin (CEO) infectious laryngotracheitis (ILT) live attenuated vaccines, although capable of protecting against disease and reducing challenge virus replication, can regain virulence. Recombinant ILT vaccines do not regain virulence but are partially successful at blocking challenge virus replication. The objective of this study was to evaluate the effect of rHVT-LT vaccination on CEO replication and how this vaccination strategy enhances protection and limits challenge virus transmission to naïve contact chickens. The rHVT-LT vaccine was administered at 1 day of age subcutaneously and the CEO vaccine was administered at 6 weeks of age via eye-drop or drinking water. CEO vaccine replication post vaccination, challenge virus replication and transmission post challenge were evaluated. After vaccination, only the group that received the CEO via eye-drop developed transient conjunctivitis. A significant decrease in CEO replication was detected for the rHVT-LT + CEO groups as compared to groups that received CEO alone. After challenge, reduction in clinical signs and challenge virus replication were observed in all vaccinated groups. However, among the vaccinated groups, the rHVT-LT group presented higher clinical signs and challenge virus replication. Transmission of the challenge virus to naïve contact chickens was only observed in the rHVT-LT vaccinated group of chickens. Overall, this study found that priming with rHVT-LT reduced CEO virus replication and the addition of a CEO vaccination provided a more robust protection than rHVT alone. Therefore, rHVT-LT + CEO vaccination strategy constitutes an alternative approach to gain better control of the disease.

Production losses in laying hens during infestation with the poultry red mite Dermanyssus gallinae.

A research centre with 30,568 laying hens, kept in enriched cages and in aviaries, had become naturally infested with poultry red mites (PRM) in 32 of its 48 bird units. Therefore, at the age of 52 weeks all hens were treated with fluralaner through the drinking water. After this treatment, PRM were no longer observed. As all birds were of the same age, and since production figures were measured daily in all 48 units, this offered a unique opportunity to examine how PRM had affected performance. Statistical analyses were done to compare the evolution of production data from the pre-treatment to the post-treatment period in units that were visually free of PRM or infested with PRM to different levels. Production standards provided by the breeding organizations were used as a reference. The results demonstrated significant posttreatment increases of laying percentage, egg weight, egg mass, percentage first choice eggs, feed intake and body weight in heavily infested hens of one or both housing systems, as compared to the non-infested controls. These data confirm that PRM infestations can impact the main performance traits related to profitability of laying hen farms as well as the hens' general condition.

Effect of a Drinking Water Conditioner on Stability and Efficacy of Fluralaner in Laying Hens Infested with Poultry Red Mites.

Concurrent use of a colorant during drinking water treatment could contribute to the correct application of fluralaner to poultry. The present studies therefore examined whether the blue-colored drinking water conditioner Vac-Safe has an influence on the stability of fluralaner in water and/or on its efficacy for the control of poultry red mites (PRM). Laboratory trials showed that fluralaner dissolved at various concentrations in water conditioned with Vac-Safe retained full stability for at least 27 hr at temperatures up to 40 C. Further, a field trial demonstrated that the efficacy of fluralaner in eliminating PRM from two infested houses of laying hens was equal when administered through drinking water with or without Vac-Safe. Consistently in both flocks, after treatment PRM could not be detected and sharp increases in laying percentage and produced egg mass were observed. It was concluded that Vac-Safe does not reduce the stability and treatment efficacy of fluralaner when administered simultaneously through drinking water.

Efecto de un acondicionador de agua potable sobre la estabilidad y eficacia de fluralaner en gallinas de postura infestadas con ácaros rojos de aves de corral. El uso simultáneo de un colorante durante el tratamiento del agua potable podría contribuir a la correcta aplicación de fluralaner en la avicultura comercial. Por lo tanto, los estudios actuales examinaron si el acondicionador de agua potable de color azul Vac-Safe influye en la estabilidad del fluralaner en agua y en su eficacia para el control de ácaros rojos de las aves. Las pruebas de laboratorio demostraron que el fluralaner disuelto en diversas concentraciones en agua acondicionada con Vac-Safe retuvo su estabilidad total por lo menos durante 27 horas a temperaturas de hasta 40°C. Además, un ensayo de campo demostró que la eficacia del fluralaner para eliminar el ácaro rojo de dos casetas infestadas de gallinas de postura fue similar cuando se administraron a través del agua potable con o sin Vac-Safe. Consistentemente en ambas parvadas, después del tratamiento no se pudo detectar al ácaro rojo y se observaron aumentos significativos en el porcentaje de postura y de la masa de huevo producida. Se concluyó que Vac-Safe no reduce la estabilidad y la eficacia del tratamiento de fluralaner cuando se administra simultáneamente a través de agua potable.