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ARS Home » Southeast Area » Mississippi State, Mississippi » Poultry Research » Research » Research Project #432042

Research Project: Transmission, Pathogenesis, and Control of Avian Mycoplasmosis

Location: Poultry Research

2018 Annual Report

1. Compare and characterize the transmissibility of Mycoplasma gallisepticum (MG) (virulent and attenuated vaccine strains) between birds in different commercial types of housing systems. 2. Identify the genetic and phenotypic differences between virulent and attenuated vaccine strains which may aid in developing an assay that will allow the differentiation of infection from vaccination. 3. Investigate the efficacy of in ovo vaccination strategies to protect against disease caused by MG.

To determine the transmissibility of Mycoplasma gallisepticum (MG) under varying conditions relevant to commercial poultry industries, layer chickens will be challenged with virulent and attenuated MG strains and then will be placed among naïve poultry. Transmissibility will be assessed by detection the MG among non-challenged poultry. To determine the impact of housing system on the transmission rates both conventional cage and non-cage systems will be investigated. Further, among conventional cage systems, the ventilation systems will include both still air and tunnel ventilation. Among the non-cage systems, experiments will be designed to compare poultry housed over open pit, deep pit, and flush tank systems to determine any effects on MG transmissibility. To compare genetic and phenotypic differences between virulent and attenuated strains of MG, MG strains will be sequenced and their genome assembled. Further, comparative proteomics will be performed, and all associated findings will be analyzed to elucidate differences which may be applied to future means of MG control. To develop an MG in ovo vaccination protocol and test its’ potential for application towards protection of commercial flocks from MG challenge, experiments will be initially be performed to determine appropriate dosage levels. The effects of the various doses of the MG vaccine on the 18 d embryo will be determined and findings will be applied to the development of a commercially applicable high throughput automated protocol. In addition, chicks derived from the vaccinated eggs will be hatched and assessed for afforded protection.

Progress Report
Research has been completed towards determining the impact of housing systems and air flow on the transmission rates of 2 strains of Mycoplasma gallisepticum (MG). In particular, trials have been initiated and completed that assess the transmission of MG strains F (low virulence) and Rlow (high virulence) at low air flow. Investigations on the impact of litter system on the transmission of MG have been initiated and completed also. The first of two trials to assess the impact of a flush-type vs. high-rise system has been completed and a second trial is underway. Research pertaining to proteomic analysis has resulted in a number of genes of interest that have been identified, although no single or small subset of genes responsible for virulence is obvious from the data. Further evaluation of the proteomic data may provide a means of identifying the genes that impact virulence or a protective host immune response. The proteomic analysis is ingoing, and will be completed next year, as stipulated in the 36 month milestone. A peer reviewed publication on genomic assemblies is in the process of being drafted for submission. Finally, in ovo injection of 18-day-of-incubation chicken eggs with F strain MG has been successful to the extent that while there was a small numerical decrease in hatchability in the vaccinated eggs, that difference was not significantly different from hatchability of control eggs.


Review Publications
Nuthalapati, N., Olanrewaju, H.A., Branton, S.L., Pharr, G.T. 2017. Evaluation of the growth of the bursa of fabricius in broilers reared under different light photoperiods. International Journal of Poultry Science. 16:481-485.