The abilities of Massachusetts-type vaccine virus and virulent infectious bronchitis (IB) field virus to increase colibacillosis susceptibility were compared. In four experiments, 29-day-old female commercial broilers housed in isolators, were infected intratracheally and oculonasally with IB vaccine strains (H120 and H52) or virulent IB field strains (D387 and M41) (4.8 or 6.8 log(10) median embryo infective dose, per broiler). Five days later, Escherichia coli 506 strain was given intratracheally (5.6 to 8.8 log(10) colony forming units/broiler). The incidence of nasal discharge at 3 and 5 days after IB virus infection was used to assess the clinical effect of the IB infection, while mortality, body weight uniformity and E. coli lesions at 7 days following E. coli inoculation were used as parameters for colibacillosis. Nasal discharge was observed in 6/117 (5%), 26/119 (22%), 35/119 (29%) and 115/120 (96%) of broilers infected with H120, H52, D387 and M41 virus, respectively. Apart from H52 and D387, differences between IBV strains were significant. IB vaccine and virulent IB viruses did not generally differ significantly in their ability to induce colibacillosis susceptibility. Mean colibacillosis lesion scores of H52-infected birds even significantly exceeded those of birds infected with the other IB viruses. The ability of H120 virus to induce colibacillosis susceptibility tended to be the weakest. The practical consequences of these findings are discussed.

Vaccinal reaction and seroresponse induced by an Ulster 2C strain derived Newcastle disease (ND) vaccine (ND) (PoulvacR NDW Broiler) were compared with those due to three other lentogenic ND vaccines (NDP, LZ58 and Clone 30) used in broilers in the Netherlands. Comparisons were made in SPF-WL hens and commercial broilers with maternally derived antibodies, using a fully standardized model. The criteria used were body weight gain and mortality rate following vaccine aerosol exposure and susceptibility to experimentally induced Colibacillosis. The NDW vaccine was the mildest, followed by Clone 30-, LZ58- and NDP vaccine. Although the seroresponse of SPF-WL hens exposed to NDW vaccine was significantly less than that induced by the other vaccines, the response was still substantial. Seroresponse to NDP-, LZ58- and Clone 30 vaccine did not differ significantly mutually. In broilers, serores-ponses to NDW- and Clone 30-vaccine were similar.

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

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A syndrome characterized by runting, bad feathering end moderate to serious leg weakness occurring in broiler flocks could be reproduced experimentally in birds kept in isolators. The disease could be transmitted to one day old broiler chicks by inoculation of homogenized intestines from birds suffering from this syndrome. Moreover, the disease could be reproduced in a second bird passage with homogenized intestines collected 4 weeks after the primary inoculation. After inoculation of day old broilers with a bacterium and mycoplasma free filtrate of the original inoculum the disease occurred as well, but to a lesser extent. It is concluded that an infectious agent plays an important role in the etiology of this disease.