|Pharr, G -|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2010
Publication Date: September 15, 2010
Citation: Branton, S.L., Leigh, S.A., Purswell, J.L., Evans, J.D., Collier, S.D., Olanrewaju, H.A., Pharr, G.T. 2010. A chronicle of serologic response in commercial layer chickens to vaccination with commercial F strain Mycoplasma gallisepticum vaccine. Avian Diseases. 54(3):1108-1111. Interpretive Summary: Vaccination of multi-age layer operations wherein 1 million “+” commercial layer chickens are housed has been spurious until development of the CPJ Vaccinator in recent years. Still, even with its use, vaccinations were spurious in terms of seroconversion (actual response by the chickens’s immune system). Over the past five years, factors have been shown to impact seroconversion to one vaccine in particular, the respiratory pathogen Mycoplasma gallisepticum (MG). These factors include type of nozzle used to spray the vaccine, temperature of the water used to rehydrate and administer the vaccine, pH and osmolarity of the fluid used to apply the vaccine. In the present study, one farm was monitored over four and half years for its seroconversion rates during which time the vaccination protocol was amended as factors were identified that enhanced seroconversion rates. The results of that study showed that implementation and inclusion of the optimized factors into the vaccination protocol for MG enhanced serconversionas rates as they went from an initial 50-55% positive seroconversion rate to a consistent 100% positive seroconversion rate.
Technical Abstract: Initial efforts by the poultry industry at controlling and containing Mycoplasma gallisepticum (MG) included testing and slaughter of reactor flocks. Ultimately, using the aforementioned measures coupled with heat treatment of hatching eggs together with biosecurity and biosurveillance procedures, the entirety of the poultry breeder industry was cleared of MG. Owing to management in both the commercial broiler and turkey sectors wherein “all-in, all-out” rearing practices were utilized, these two sectors have been able to maintain MG-free commercial flocks save for the sporadic mycoplasmal outbreak. While all three sectors of the industry have experienced tremendous growth since control efforts directed at MG were initiated, it is the table egg sector which has, arguably, experienced the most change in terms of management practices that have impeded maintenance of MG-free status. Specifically, it is the advent and use of multi-age production complexes wherein 14 or more houses not only share a common environment but also the houses are interconnected via walkways and egg belts which transport the eggs to the complex-associated egg processing plant. In each of the houses 75,000 or more hens are maintained from 20 – 100 weeks of age (WOA), Once chickens are placed in these layer complexes, individual houses will not be depopulated until the birds reach 100 WOA and the complex itself will constantly have chickens present during its approximate 20 to 30 year production service life. Thus, the presence of 1.5 million MG-free hens in a modern layer complex represents a population at risk. Because of the inherent egg production and mortality losses together with the cost of therapeutics associated with MG infection of hens in production and the likely probability of MG gaining access to a layer complex at some point during the facilities service life, complex managers have opted to make live MG vaccines an integral management practice in modern layer complexes. This report describes the SPA serologic response obtained from blood taken six weeks post-vaccination from successive pullet flocks over a 56 month period on a commercial layer complex wherein the chronological and cumulative inclusion of identified optimal parameters were included in the live MG vaccination protocol.