Variant serotypes of infectious bronchitis virus isolated from commercial layer and broiler chickens.

Twenty infectious bronchitis virus (IBV) field isolates obtained from commercial layer and broiler chickens in 1987 and 1988 were serotyped using the virus-neutralization (VN) test. Six different previously unrecognized variant serotypes were identified from a total of seven isolates from layer chickens. Only two isolates, both from Maine, were the same variant serotype. Variant serotypes also were recovered from layer flocks in Illinois and Washington and the province of Ontario, Canada. Two different variants were isolated from the same multi-age layer complex in Connecticut. Only one of 13 broiler chicken isolates was found to be a new variant serotype, that being from birds reared in Delaware. Cross-protection studies in specific-pathogen-free chickens indicated that vaccines containing the Holland, L-1, or Connaught strains of Massachusetts (Mass) combined with Arkansas produced a broader spectrum of immunity against challenge with the layer variants than Mass (Holland) alone or Mass (L-1) + Connecticut. All vaccines tested produced solid immunity (greater than or equal to 80% protection) against the broiler variant virus.     

Nephropathogenic infectious bronchitis in Pennsylvania chickens 1997-2000

Nephropathogenic infectious bronchitis (NIB) was diagnosed in 28 infectious bronchitis virus (IBV)-vaccinated commercial chicken flocks in Pennsylvania from December 1997 to July 2000. Early dinical signs were increased flock mortality and urinary water loss (polyuria and pollakiuria) leading to wet litter. Daily mortality ranged from 0.01% in layers to 2.45% in broilers, with total broiler mortality as high as 23%. Severe renal swelling and accumulation of urates in the tubules were commonly seen. Visceral gout and urolithiasis were less frequently observed. Histopathologic changes included characteristic tubular epithelial degeneration and sloughing with lymphoplasmacytic interstitial nephritis. Minimal respiratory disease signs were noted in broilers. Egg production and shell quality declined in layers. Confirmatory diagnosis of NIB was made by IBV antigen-specific immunohistochemical staining of the renal tubular epithelium and virus isolation. Sequencing of the S1 subunit gene of 21 IBV isolates showed the NIB outbreak to be associated with two unique genotypes, PA/Wolgemuth/98 and PA/171/99. The cases from which the genotypes were isolated were clinically indistinguishable. The NIB viruses were unrelated to previously recognized endemic strains in Pennsylvania and were also dissimilar to each other. Genotype PA/Wolgemuth/98 was isolated almost exclusively during the first 14 mo of the outbreak, whereas PA/171/99 was recovered during the final 18 mo. The reason for the apparent replacement of PA/Wolgemuth/98 by PA/171/99 is not known.     

Protection of chickens against infectious bronchitis virus with a multivalent DNA vaccine and boosting with an inactivated vaccine

The protective efficacy of DNA plasmids encoding avian infectious bronchitis virus (IBV) S1, N, or M protein was investigated in chickens. Chickens were inoculated monovalently (with plasmid pVAX1-16S1, pVAX1-16M, or pVAX1-16N alone) or multivalently (combination of the three different plasmids, pVAX1-16S1/M/N). A prime-boost immunization protocol against IBV was developed. Chickens were immunized with the multivalent DNA vaccine twice and then boosted with an inactivated vaccine once. Antibody titers of the chickens immunized with pVAX1-16S1/M/N were much higher than those of the monovalent groups (p < 0.01). A protective rate up to 90% was observed in the pVAX1-16S1/M/N group. The serum antibody titers in the prime-boost birds were significantly higher than those of the multivalent DNA vaccine group (p < 0.01) but not significantly different compared to the inactivated vaccine group at 49 days of age. Additionally, the prime-boost group also showed the highest level of IBV-specific cellular proliferation compared to the monovalent groups (p < 0.01) but no significant difference was found compared to the multivalent DNA vaccine group, and the prime-boost group completely protected from followed viral challenge.     

不同治疗方法对肾型传染性支气管炎的影响

肾型传染性支气管炎是受到广泛重视和研究的一种由IBV引起的禽的急性、高度接触性传染病，它以肾肿大，尿酸盐沉积为主要症状，造成雏鸡大量死亡，蛋鸡产蛋量下降。IB在我国的大部分地区都有流行，经免疫接种的鸡群也时有暴发，给养鸡业造成严重的损失，所以在发病后能及时有效的进行治疗，是发病后减少损失的一个重要手段。本试验主要对     

Prevalence of Arkansas-type infectious bronchitis virus in Delmarva peninsula chickens

The prevalence of Arkansas (Ark)-type infectious bronchitis virus (IBV) in Delmarva peninsula broiler-type chickens was determined. The immunity of 5-to-11-week-old commercial broilers was evaluated by intraocular inoculation with Ark-type DPI strain (Ark DPI) challenge virus and collection of tracheal swabbings 5 days later. Serum Ark-type antibody titers were obtained using the virus-neutralization test. Eighty-five flocks were tested from January to August 1981. Nearly 60% of the flocks had substantial (greater than or equal to 70%) local immunity of the upper respiratory tract. Twenty-two percent had intermediate (50-69%) and 19% of the flocks had low (less than or equal to 40%) levels of local immunity. Serum antibody titers generally agreed with challenge results. In addition, high Ark-type IBV neutralizing-antibody titers were found in 16 Delmarva broiler breeder flocks. Seven current IBV field isolates were characterized for antigenic similarity to Ark DPI. Four isolates contained Ark antigen(s) based on significant neutralization in virus-neutralization tests and on substantial immunity to challenge afforded by Ark DPI virus immunization. Three isolates did not appear to contain Ark antigen(s). Immunization of chickens with Ark DPI virus afforded substantial protection against Connecticut- and homologous-type virus challenge, partial immunity (63%) against JMK, and no protection against the Massachusetts 41 strain of IBV.     

Pathogenicity of infectious bronchitis virus isolates from Ontario chickens

Infectious bronchitis (IB) is one of the important viral diseases of chickens, and in spite of regular vaccination, IB is a continuous problem in Canadian poultry operations. In an earlier study using sentinel chickens we determined the incidence of infectious bronchitis virus (IBV) in Ontario commercial layer flocks. The objective of this study was to determine the pathogenicity of 5 nonvaccine-related IBV isolates recovered from the sentinel birds. The clinical signs, gross, and histological lesions in specific pathogen-free chickens indicated that all 5 isolates caused mild lesions in the respiratory tract. An important finding of this study was the significantly lower average daily weight gain among virus-inoculated groups of chickens during the acute phase of infection. Based on sequences of part of the S1 gene IBV-ON2, IBV-ON3, and IBV-ON5 formed a cluster and they were closely related to strain CU-82792. IBV-ON4 had 98.7% identity with the strain PA/1220/9, a nephropathogenic variant.     

Comparative nephropathogenicity of infectious bronchitis virus in bursectomized and nonbursectomized chickens

A study was conducted to compare the responses of bursectomized (Bx) and nonbursectomized (non-Bx) specific-pathogen-free male chickens to Australian T strain of infectious bronchitis virus. Four chickens from each group were killed at 3, 5, 7, 14, 21, and 28 days after conjunctival inoculation of the virus. Clinical signs and gross and microscopic lesions were more severe in Bx than in non-Bx chickens. The non-Bx chickens had linear IgG deposits along the renal tubules. Virus-neutralizing titers were log10 2.74 to 4.33 for non-Bx chickens and less than log10 1.25 for the inoculated Bx and for broth-inoculated Bx and non-Bx chickens (controls). Early in the disease, renal lesions were of the same type in all infected chickens, but were more severe in Bx chickens. Later, nephritis was chronic and active in Bx chickens and was chronic in non-Bx chickens.