Vaccination of one-day-old broiler chicks against infectious coryza

Avibacterium paragallinarum, the Causative Agent of Infectious Coryza: A Comprehensive Review

Infectious coryza (IC) caused by Avibacterium paragallinarum (AP) has risen in importance as a poultry disease over the past several years because of its increased incidence in commercial poultry in both Europe and the United States. Because of this rise in importance, more attention has been focused on diagnosis, isolation, and surveillance of this bacterial pathogen. As a result, new knowledge has been produced and published. This review was compiled with the main purpose of summarizing and presenting the updated knowledge available about AP. However, the new knowledge can only be understood in the context of previously known facts about the disease. Therefore, this review has been organized in two major parts. The first part is a review of the established knowledge about AP, followed by recent updates. In the first part, we summarize the established well-known as well as some of the less-known facts and literature about AP. The second section focuses on specifics of the latest IC outbreaks in commercial poultry in northern latitudes, particularly in Europe and in North America. Additionally, we reviewed the current geographical distribution of the disease in Asia, South America, and Africa. The crises created by emerging or re-emerging disease outbreaks ignite interest in understanding the disease and pathogen in order to combat it properly. This results in new knowledge that improves the understanding of the disease features, leading to improved disease prevention, control, and eradication. Although knowledge about AP has advanced, knowledge gaps about the disease still persist. Therefore, this review concludes with summarizing the current knowledge gaps as well as potential areas for future research.

Development and Validation of PCR Diagnostic Assays for Detection of Avibacterium paragallinarum and Ornithobacterium rhinotracheale

PCR is the most effective method for detecting difficult-to-cultivate pathogens and pathogens that are part of mixed infections in animals, such as Ornithobacterium rhinotracheale, which causes bird ornithobacteriosis, or Avibacterium paragallinarum, which causes infectious coryza. In this work, we developed and validated two efficient and sensitive diagnostic assays for the rapid and accurate detection of A. paragallinarum and O. rhinotracheale DNA in bacterial isolates and clinical samples using real-time PCR with TaqMan-like probes. When designing the PCR assays, we performed in silico analysis, optimized DNA isolation methods and PCR conditions, and assessed the analytical and diagnostic performance of PCR. We designed primers and probes that have no mismatches with published whole-genome sequences of bacteria. The optimization of conditions showed that the PCR assays are sufficiently robust to changes in temperature and oligonucleotide concentration. The validation showed that the developed assays have high analytical and diagnostic sensitivity and specificity. These assays are expected to improve the differential diagnosis of respiratory diseases in chickens and turkeys.

Pathogenicity of Avibacterium paragallinarum Strains from Peru and the Selection of Candidate Strains for an Inactivated Vaccine

Worldwide, Avibacterium paragallinarum is the aetiological agent of infectious coryza in poultry. Vaccines are the best means of control, helping reduce clinical signs and colonization of this bacterium. Most vaccines are based on international reference strains, or, lately, regional strains, but, generally, without any information regarding their virulence. The characterization of the pathogenicity of 24 Av. paragallinarum strains of the three Page serogroups, including four variant strains of serogroup B, all isolated from infectious coryza outbreaks in Peru, was performed. After experimental inoculation into the infraorbital sinuses, information regarding their capacity to induce infectious coryza typical clinical signs, spreading, and colonization was recorded. Furthermore, after intraperitoneal inoculation, septicaemia and death were registered. Differences among strains in these parameters were observed, even within strains from the same serogroup. Finally, the four most pathogenic strains, one from each serogroup, were chosen to formulate an experimental vaccine that was tested successfully against homologous challenges in reducing clinical signs and colonization in vaccinated birds compared to unvaccinated ones. This is the first time that Av. paragallinarum strains from Peru were studied thoroughly for their virulence in a search for improving vaccine formulation.