International audienceAs a part of the development of an efficient dry powder aerosol vaccine for poultry, the objective of this study was to accurately determine the deposition pattern of nebulized microspheres in the airways of unanaesthetized chickens of different ages (day-, 2-week- and 4-week-old). In a first part of the study, the aerosol administration method was characterized: the influence of different nebulizers and nebulizing protocols on the relative humidity in the exposure chamber, the particle size distributions, the microsphere output and single microsphere percentage were determined. In the second part, birds were exposed to nebulized fluorescently labelled polystyrene microspheres (1 to 20 µm). Respiratory and gastro-intestinal tract tissue samples were collected and the number of fluorescent microspheres per sample was determined. In 2- and 4-week-old chickens, microspheres of 5 and 10 µm, respectively, were too large for deposition in the lungs and air sacs as less than 5% of these microspheres penetrated into the lower airways. The larger size of microspheres reaching the lower airways of 4-week-old birds was explained by increasing airway dimensions with age. For day-old chickens, deposition in the lungs decreased from 17 to 3% with increasing particle size (1-20 µm), but increased in the air sacs from 6 to 20%. Consequently, the total deposition percentage in the lower airways was independent of microsphere size and even 20 µm particles were able to penetrate into the lower airways, which was attributed to mouth breathing of the day-old chickens

In order to study the airborne transmission of an arthropathic strain of Mycoplasma synoviae, preliminary aerosol experiments were performed. They were conducted in duplicate in an empty isolator (1.3 m3) to assess the yield and viability of M. synoviae with time compared with Mycoplasma gallisepticum and Enterococcus faecalis. After aerosol generation air samples were taken with two different devices using gelatine or cellulose nitrate filters. There was no difference between the devices, but cellulose nitrate filters yielded very low bacterial counts. The aerosolized dose per isolator for M. synoviae was 3.4 x 10(10) colony-forming units (cfu), for M. gallisepticum was 2.6 x 10(10) cfu and for E. faecalis was 3 x 10(10) cfu. Immediately after aerosolization, concentrations of about 10(6) to 10(7) cfu/m3, 10(7) to 10(8) cfu/m3 and 10(8) to 10(9) cfu/m3 air of M. synoviae, M. gallisepticum and E. faecalis were found, respectively. At 25 min M. synoviae concentrations dropped below the detection level (<4 x 10(4) cfu), while 10(5) to 10(6) and 10(8) to 10(9) cfu were found for M. gallisepticum and E. faecalis, respectively. The average M. synoviae concentration during the experiment was estimated at 10(2) to 10(3) cfu/l. The M. gallisepticum and E. faecalis aerosol generated an average of approximately 10(3) to 10(4) cfu/l air and 10(5) to 10(6) cfu/l air, respectively. Thus mycoplasma and E. faecalis aerosols were successfully generated despite considerable initial loss as measured by culture. The loss was greater in the mycoplasma aerosols, especially those of M. synoviae.

No abstract

A powder vaccine intended for aerosol vaccination of poultry was formulated by spray drying a live attenuated Newcastle disease virus with potential stabilizers (mannitol, trehalose, polyvinylpyrrollidone (PVP), bovine serum albumin (BSA)). Thermodynamic properties, water sorption, particle size distribution, nebulization properties, density and morphology of the powders were evaluated and the virus survival during spray drying and storage was determined by incubation in embryonated eggs and subsequent haemagglutination assay. All powders had a narrow size distribution with a median volume diameter of ±30 m (suitable for primary respiratory vaccination of chickens) and good aerosolization characteristics. Four amorphous, hygroscopic formulations were produced (trehalose, trehalose-PVP, trehalose-BSA, trehalose-PVP-BSA), where addition of BSA was beneficial for virus survival during production and storage at 6 and 25 • C. A crystalline, non-hygroscopic powder (mannitol) had a lower stabilizing capacity during production but maintained the remaining virus titre during storage. In conclusion, the study demonstrates that it is possible to produce a dry powder formulation of an attenuated live vaccine for mass vaccination of poultry in a one-step spray drying process.