Pros and Cons on Use of Live Viral Vaccines in Commercial Chicken Flocks.

The poultry industry is the largest source of meat and eggs for the growing human population worldwide. Key concerns in poultry farming are nutrition, management, flock health, and biosecurity measures. As part of the flock health, use of live viral vaccines plays a vital role in the prevention of economically important and common viral diseases. This includes diseases and production losses caused by Newcastle disease virus, infectious bronchitis virus, infectious laryngotracheitis virus, infectious bursal disease virus, Marek's disease virus, chicken infectious anemia virus, avian encephalomyelitis virus, fowlpox virus, and avian metapneumovirus. These viruses cause direct and indirect harms, such as financial losses worth millions of dollars, loss of protein sources, and threats to animal welfare. Flock losses vary by type of poultry, age of affected animals, co-infections, immune status, and environmental factors. Losses in broiler birds can consist of high mortality, poor body weight gain, high feed conversion ratio, and increased carcass condemnation. In commercial layers and breeder flocks, losses include higher than normal mortality rate, poor flock uniformity, drops in egg production and quality, poor hatchability, and poor day-old-chick quality. Despite the emergence of technology-based vaccines, such as inactivated, subunit, vector-based, DNA or RNA, and others, the attenuated live vaccines remain as important as before. Live vaccines are preferred in the global veterinary vaccine market, accounting for 24.3% of the global market share in 2022. The remaining 75% includes inactivated, DNA, subunit, conjugate, recombinant, and toxoid vaccines. The main reason for this is that live vaccines can induce innate, mucosal, cellular, and humoral immunities by single or multiple applications. Some live vaccine combinations provide higher and broader protection against several diseases or strains of viruses. This review aimed to explore insights on the pros and cons of attenuated live vaccines commonly used against major viral infections of the global chicken industry, and the future road map for improvement.

Estudio recapitulativo- Pros y contras del uso de vacunas virales vivas en parvadas de pollos comerciales. La industria avícola es la mayor fuente de carne y huevos para la creciente población humana en todo el mundo. Las principales preocupaciones en la avicultura son la nutrición, el manejo, la salud de las parvadas y las medidas de bioseguridad. Como parte de la salud de las parvadas avícolas, el uso de vacunas virales vivas juega un papel vital en la prevención de enfermedades virales comunes y de importancia económica. Esto incluye enfermedades y pérdidas en la producción causadas por el virus de la enfermedad de Newcastle, el virus de la bronquitis infecciosa, el virus de la laringotraqueítis infecciosa, el virus de la enfermedad infecciosa de la bolsa, el virus de la enfermedad de Marek, el virus de la anemia infecciosa del pollo, el virus de la encefalomielitis aviar, el virus de la viruela aviar y el metapneumovirus aviar. Estos virus causan daños directos e indirectos, como pérdidas financieras valoradas en millones de dólares, pérdida de fuentes de proteínas y amenazas al bienestar animal. Las pérdidas en las parvadas avícolas varían según el tipo de aves, la edad de los animales afectados, las coinfecciones, el estado inmunológico y los factores ambientales. Las pérdidas en aves de engorde pueden consistir en una alta mortalidad, un pobre aumento de peso corporal, un alto índice de conversión alimenticia y un mayor decomiso de las canales. En las gallinas de postura comerciales y en las parvadas de reproductoras, las pérdidas incluyen una tasa de mortalidad superior a la normal, una escasa uniformidad de la parvada, caídas en la producción y calidad de los huevos, una pobre incubabilidad y una mala calidad de los pollitos de un día. A pesar de la aparición de vacunas de base tecnológica, como las inactivadas, subunitarias, vectoriales, de ADN o ARN, entre otras, las vacunas vivas atenuadas siguen siendo tan importantes como antes. Las vacunas vivas son las preferidas en el mercado mundial de vacunas para uso veterinario y representaron el 24.3% de la cuota de mercado mundial en el año 2022. El 75% restante incluye vacunas inactivadas, de ADN, de subunidades, conjugadas, recombinantes y toxoides. La razón principal de esto es que las vacunas vivas pueden inducir inmunidad innata, de mucosas, celular y humoral mediante aplicaciones únicas o múltiples. Algunas combinaciones de vacunas vivas brindan una protección mayor y más amplia contra varias enfermedades o cepas de virus. Esta revisión tuvo como objetivo explorar ideas sobre los pros y los contras de las vacunas vivas atenuadas comúnmente utilizadas contra las principales infecciones virales de la industria avícola mundial, y las rutas futuras para mejorar.

Evaluation of Natural Antimicrobial Substances Blend as a Replacement for Antibiotic Growth Promoters in Broiler Chickens: Enhancing Growth and Managing Intestinal Bacterial Diseases.

In recent years, commercial use of antibiotic growth promoter (AGP) has restrictions due to drug resistance against intestinal pathogenic bacteria: Escherichia coli, Salmonella, and Clostridium perfringens. Currently there is no single non-antibiotic treatment approach that is effective against intestinal illnesses in broiler chicken. Hence, present study aimed to analyze efficacy of blend of natural antimicrobial substances (probiotics, prebiotics, organic acids, and essential oils blend named as AGPR) as replacers of AGPs (BMD and CTC) for promoting growth and controlling bacterial diseases in aforementioned three microbes challenged broiler chickens. Effects of treatments (5) and microbes (3) on growth and health performances in experimental birds were analyzed using two factorial ANOVA. Health performance like pathogen loads, morbidity and mortality was considerably reduced by AGPR. Similarly small intestine villi morphometry, nutrition utilization, serum immune response, and carcass yield, was improved significantly by AGPR equivalent to AGPs. Further, growth performance like body weight gain, feed efficiency was also improved by AGPR compared to control but, non-significantly. Among three microbes, E. coli infections had higher morbidity and mortality rates. It was concluded that AGPR blend could be used to improve growth and control the intestinal bacterial infections in broiler chickens as an alternative for AGPs.

Evaluation of protection and immunity induced by infectious bronchitis vaccines administered by oculonasal, spray or gel routes in commercial broiler chicks.

Broiler chicks' responses following combined IBV live attenuated Massachusetts and 793B strains through gel, spray or oculonasal (ON) vaccination routes were cross-compared. Subsequently, the responses following IBV M41 challenge of the unvaccinated and vaccinated groups were also assessed. Post-vaccination humoral and mucosal immune responses, alongside viral load kinetics in swabs and tissues, were determined using commercial ELISA assays, monoclonal antibody-based IgG and IgA ELISA assays and qRT-PCR respectively. After challenged with IBV-M41 strain, humoral and mucosal immune responses, ciliary protection, viral load kinetics, and immune gene mRNA transcriptions between the three vaccination methods were examined and compared. Findings showed that post-vaccinal humoral and mucosal immune responses were similar in all three vaccination methods. Post vaccinal viral load kinetics is influenced by method of administration. The viral load peaked in the ON group within the tissues and the OP/CL swabs in the first and third weeks respectively. Following M41 challenge, ciliary protection and mucosal immune responses were not influenced by vaccination methods as all three methods offered equal ciliary protection. Immune gene mRNA transcriptions varied by vaccination methods. Significant up-regulation of MDA5, TLR3, IL-6, IFN-α and IFN-ß genes were recorded for ON method. For both spray and gel methods, significant up-regulation of only MDA5 and IL-6 genes were noted. The spray and gel-based vaccination methods gave equivalent levels of ciliary protection and mucosal immunity to M41 virulent challenge comparable to those provided by the ON vaccination. Analysis of viral load and patterns of immune gene transcription of the vaccinated-challenged groups revealed high similarity between turbinate and choanal cleft tissues compared to HG and trachea. With regards to immune gene mRNA transcription, for all the vaccinated-challenged groups, similar results were found except for IFN-α, IFN-ß and TLR3, which were up-regulated only in ON compared to gel and spray vaccination methods.