Characterization of nephropathogenic infectious bronchitis virus DMV/1639/11 recovered from Delmarva broiler chickens in 2011.

A limited outbreak of nephropathogenic infectious bronchitis (NIB) occurred in three Delmarva (DMV) commercial broiler chicken flocks in 2011. Isolates of NIB virus (NIBV)--DMV/1639/11, DMV/3432/11, and DMV/3902/11--were characterized by sequence analysis of the N-terminal subunit (S1) of the spike (S) gene. Findings indicated that the isolates were identical to each other and to PA/9579A/10, a 2010 isolate from poultry in Pennsylvania. The 2010 and 2011 isolates appear to have originated from a 1997-2000 NIB outbreak in Pennsylvania. DMV/1639/11 and PA/9579A/10 were determined to be nephropathogenic in susceptible chickens, yielding virus reisolations from kidney and inducing characteristic interstitial nephritis microscopic lesions. In a controlled laboratory study, 40% of chickens vaccinated with a combination live vaccine containing infectious bronchitis virus (IBV) strains Massachusetts (Mass) + Connecticut (Conn) were positive on virus isolation attempts after challenge with DMV/1639/11, compared with only 13% of Mass + Arkansas (Ark) vaccinates. Both combination vaccines gave partial protection against the development of DMV/1639/11-induced renal lesions. Although numerically fewer chickens vaccinated with Mass + Conn had interstitial nephritis compared with those vaccinated with Mass + Ark, neither vaccine combination offered greater protection (P < 0.05) than observed in unvaccinated chickens challenged with DMV/1639/11. Mass + Ark vaccinations, applied under commercial conditions in the hatchery (spray) and on-farm (spray), did not protect the trachea or kidney from DMV/1639/11 challenge. Serologic testing of broiler flocks found < 3% (2 of 69) tested to possess specific antibodies to DMV/1639/11, indicating the virus had not become established in the region.

Effects of in ovo vaccination and anticoccidials on the distribution of Eimeria spp. in poultry litter and serum antibody titers against coccidia in broiler chickens raised on the used litters.

The present study reports the effects of various field anticoccidial programs on the distribution of Eimeria spp. in poultry litter and serum antibody titers against coccidia in broiler chickens raised on the used litters. The programs included in ovo vaccination and various medications with either chemicals, ionophores, or both. In general, serum samples from these chickens showed anticoccidial antibody titers when tested at days 7 and 14 post hatch with the peak response at day 43. Serum anticoccidial titers were highest in birds fed a non-medicated diet compared with those vaccinated or fed medicated diets. Total number of Eimeria oocysts and the composition of Eimeria spp. present in the litter samples from different treatment groups varied depending on the type of anticoccidial program. Oocyst counts in general ranged from 3.7×10(3) to 7.0×10(4) per g of litter. Importantly, both morphological and molecular typing studies revealed four major predominant Eimeria spp., E. acervulina, E. maxima, E. praecox, and E. tenella in the litter samples. Collectively, these results indicate that the field anticoccidial programs influenced the type and abundance of Eimeria spp. present in the litter samples and also modulated host immune response to Eimeria.

The pathogenesis of low pathogenicity H7 avian influenza viruses in chickens, ducks and turkeys.

BACKGROUND: Avian influenza (AI) viruses infect numerous avian species, and low pathogenicity (LP) AI viruses of the H7 subtype are typically reported to produce mild or subclinical infections in both wild aquatic birds and domestic poultry. However relatively little work has been done to compare LPAI viruses from different avian species for their ability to cause disease in domestic poultry under the same conditions. In this study twelve H7 LPAI virus isolates from North America were each evaluated for their comparative pathogenesis in chickens, ducks, and turkeys. RESULTS: All 12 isolates were able to infect all three species at a dose of 106 50% egg infectious doses based on seroconversion, although not all animals seroconverted with each isolate-species combination. The severity of disease varied among isolate and species combinations, but there was a consistent trend for clinical disease to be most severe in turkeys where all 12 isolates induced disease, and mortality was observed in turkeys exposed to 9 of the 12 viruses. Turkeys also shed virus by the oral and cloacal routes at significantly higher titers than either ducks or chickens at numerous time points. Only 3 isolates induced observable clinical disease in ducks and only 6 isolates induced disease in chickens, which was generally very mild and did not result in mortality. Full genome sequence was completed for all 12 isolates and some isolates did have features consistent with adaptation to poultry (e.g. NA stalk deletions), however none of these features correlated with disease severity. CONCLUSIONS: The data suggests that turkeys may be more susceptible to clinical disease from the H7 LPAI viruses included in this study than either chickens or ducks. However the severity of disease and degree of virus shed was not clearly correlated with any isolate or group of isolates, but relied on specific species and isolate combinations.

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). III. Pathogenicity.

Differences in the relative pathogenicity of variant (1084 E and GLS) and standard (Edgar and STC) infectious bursal disease virus (IBDV) strains were observed after propagation in the bursa of Fabricius, embryos, or cell cultures. Bursa-derived IBDV induced the most severe lesions in the bursa of Fabricius when compared with strains propagated in embryos or cell cultures. Embryo-derived IBDV induced moderate gross bursal lesions, whereas cell culture-derived IBDV did not damage the bursa grossly. A high frequency of virus re-isolations was obtained from bursal, spleen, and thymic samples collected from birds inoculated with bursa-derived or embryo-derived IBDV. Virus re-isolation occurred much less frequently from birds inoculated with cell culture-adapted IBDV. Serological evaluations demonstrated that bursa-derived IBDV strains induced a higher neutralizing antibody response than did embryo-derived or cell culture-derived strains. These results document that the relative pathogenicity and immunogenicity of IBDV is reduced following propagation in embryos or cell cultures.