Infectious Bronchitis Outbreaks Research Articles

Protection Against Infectious Bronchitis Virus Vaccine Recombinants and Chicken-Selected Vaccine Subpopulations.

Outbreaks of infectious bronchitis (IB) continue to occur from novel variants of IB virus (IBV) emerging from selection of vaccine subpopulations and/or naturally occurring recombination events. S1 sequencing of Arkansas (Ark) -type viruses obtained from clinical cases in Alabama broilers and backyard chickens shows both Ark Delmarva Poultry Industry (ArkDPI) vaccine subpopulations as well as Ark vaccine viruses showing recombination with other IB vaccine viruses. IB Ark-type isolates AL5, most similar to an ArkDPI vaccine subpopulation selected in chickens, AL4, showing a cluster of three nonsynonymous changes from ArkDPI subpopulations selected in chickens, and AL9, showing recombination with Massachusetts (Mass) -type IBV, were examined for pathogenicity and ability to break through immunity elicited by vaccination with a commercial ArkDPI vaccine. Analysis of predicted S1 protein structures indicated the changes were in regions previously shown to comprise neutralizing epitopes. Thus, they were expected to contribute to immune escape and possibly virulence. Based on clinical signs, viral load, and histopathology, all three isolates caused disease in naïve chickens, although AL9 and AL5 viral loads in trachea were statistically significantly higher (30- and 40-fold) than AL4. S1 gene sequencing confirmed the stability of the relevant changes in the inoculated viruses in the chickens, although virus in some individual chickens exhibited additional S1 changes. A single amino acid deletion in the S1 NTD was identified in some individual chickens. The location of this deletion in the predicted structure of S1 suggested the possibility that it was a compensatory change for the reduced ability of AL4 to replicate in the trachea of naïve chickens. Chickens vaccinated with a commercial ArkDPI vaccine at day of hatch and challenged at 21 days of age showed that vaccination provided incomplete protection against challenge with these viruses. Moreover, based on viral RNA copy numbers in trachea, differences were detected in the ability of the vaccine to protect against these IBV isolates, with the vaccine protecting the most poorly against AL4. These results provide additional evidence supporting that IBV attenuated vaccines, especially ArkDPI vaccines, contribute to perpetuating the problem of IB in commercial chickens.

Immunogenicity and protective efficacy of an inactivated infectious bronchitis virus vaccine candidate from a local isolate of Bangladesh

Objective: Infectious bronchitis (IB), a highly infectious acute viral disease, is a major burden to the chicken industry worldwide. The research aimed to develop an inactivated IB vaccine using local isolates and assess its immunogenicity compared to other commercial live IB vaccines. Materials and Methods: An inactivated vaccine using a candidate IB virus (PP067159.1: Alim_IB_1001) of the QX genotype was developed according to WOAH guidelines. Chickens were vaccinated with three doses (0.25, 0.5, and 1.0 ml) at 7 days old, with a booster at 37 days old via subcutaneous (SC) and intramuscular (IM) routes. Blood samples were collected on days 7, 37, and 67 to measure immune response by indirect ELISA. On day 67, chickens were challenged with a virulent IBV strain to assess vaccine protection. The experimental IB vaccine’s immunogenicity, protective efficacy, and antibody duration were compared to a live IB vaccine (Live CEVAC® IBird) using three vaccination schedules: killed-followed-killed, live-followed-killed, and live-followed-live. Results: Chickens vaccinated with SC with 1.0 ml showed higher antibody titers compared to other SC and IM routes of vaccination. SC vaccination with 0.5 and 1 ml provided the highest protection (93%). The killed-followed-killed vaccination method produced a more consistent and protective level of antibody titers in chickens compared to the other vaccination schedules. The experimental inactivated IB vaccine led to a higher survival rate (93%) compared to live-followed-killed (87%) and live-followed-live (73%), with statistical significance (p < 0.01). All three chicken groups maintained protective antibody titers (>396) at 307 days, but titers declined faster in the live-followed-live and live-followed-killed groups compared to the killed-followed-killed group. Conclusion: The study found that the experimental inactivated IB vaccination can protect com¬mercial-layer chickens from natural IB outbreaks of the QX genotype.

Genetic and pathogenic characterization of new infectious bronchitis virus strains in the GVI-1 and GI-19 lineages isolated in central China

Avian infectious bronchitis (IB) is a highly contagious infectious disease caused by infectious bronchitis virus (IBV), which is prevalent in many countries worldwide and causes serious harm to the poultry industry. At present, many commercial IBV vaccines have been used for the prevention and control of IB; however, IB outbreaks occur frequently. In this study, two new strains of IBV, SX/2106 and SX/2204, were isolated from two flocks which were immunized with IBV H120 vaccine in central China. Phylogenetic and recombination analysis indicated that SX/2106, which was clustered into the GI-19 lineage, may be derived from recombination events of the GI-19 and GI-7 strains and the LDT3-A vaccine. Genetic analysis showed that SX/2204 belongs to the GVI-1 lineage, which may have originated from the recombination of the GI-13 and GVI-1 strains and the H120 vaccine. The virus cross-neutralization test showed that the antigenicity of SX/2106 and SX/2204 was different from H120. Animal experiments found that both SX/2106 and SX/2204 could replicate effectively in the lungs and kidneys of chickens and cause disease and death, and H120 immunization could not provide effective protection against the two IBV isolates. It is noteworthy that the pathogenicity of SX/2204 has significantly increased compared to the GVI-1 strains isolated previously, with a mortality rate up to 60%. Considering the continuous mutation and recombination of the IBV genome to produce new variant strains, it is important to continuously monitor epidemic strains and develop new vaccines for the prevention and control of IBV epidemics.

Efficacy of Two Vaccination Strategies against Infectious Bronchitis in Laying Hens.

Vaccination remains the leading control method against infectious bronchitis (IB) in poultry despite the frequently observed IB outbreaks in vaccinated flocks. Here, two vaccination regimes were evaluated against challenge with the Massachusetts (Mass) infectious bronchitis virus (IBV) strain that was linked to egg production defects in Western Canada. One vaccination strategy included live attenuated IB vaccines only, and the other used both inactivated and live attenuated IB vaccines. The two immunization programs involved priming with a monovalent live attenuated IB vaccine (Mass serotype) at day-old, followed by intervals of bivalent live attenuated IB vaccines containing the Mass and Connecticut (Conn) serotypes given to the pullets at 2-, 5-, 9-, and 14-week-old. Inactivated IB vaccine (Mass serotype) was administrated to only one group of the vaccinated birds at 14-week-old. At the peak of lay, the hens were challenged with the Mass IBV isolate (15AB-01) via the oculo-nasal route. The efficacy of the vaccines was assessed following the challenge by observing clinical signs, egg production, egg quality parameters, seroconversion, and systemic T-cell subsets (CD4+ and CD8+ cells). Moreover, the viral genome loads in the oropharyngeal (OP) and cloacal (CL) swabs were quantified at predetermined time points. At 14 days post-infection (dpi), all the hens were euthanized, and different tissues were collected for genome load quantification and histopathological examination. Post-challenge, both vaccination regimes showed protection against clinical signs and exhibited significantly higher albumen parameters, higher anti-IBV serum antibodies, and significantly lower levels of IBV genome loads in OP swabs (at 3 and 7 dpi) and trachea and cecal tonsils compared to the mock-vaccinated challenged group. However, only the birds that received live attenuated plus inactivated IB vaccines had significantly lower IBV genome loads in CL swabs at 7 dpi, as well as decreased histopathological lesion scores and IBV genome loads in magnum compared to the mock-vaccinated challenged group, suggesting a slightly better performance for using live attenuated and inactivated IB vaccines in combination. Overall, the present findings show no significant difference in protection between the two vaccination regimes against the Mass IBV challenge in laying hens.

Protection against avian coronavirus conferred by oral vaccination with live bacteria secreting LTB-fused viral proteins

The devastating impact of infectious bronchitis (IB) triggered by the IB virus (IBV), on poultry farms is generally curbed by livestock vaccination with live attenuated or inactivated vaccines. Yet, this approach is challenged by continuously emerging variants and by time limitations of vaccine preparation techniques. This work describes the design and evaluation of an anti-IBV vaccine comprised of E. coli expressing and secreting viral spike 1 subunit (S1) and nucleocapsid N-terminus and C-terminus polypeptides fused to heat-labile enterotoxin B (LTB) (LS1, LNN, LNC, respectively). Following chicken oral vaccination, anti-IBV IgY levels and cellular-mediated immunity as well as protection against virulent IBV challenge, were evaluated 14 days following the booster dose. Oral vaccination induced IgY levels that exceeded those measured following vaccination with each component separately. Following exposure to inactivated IBV, splenocytes isolated from chicks orally vaccinated with LNN or LNC -expressing bacteria, showed a higher percentage of CD8+ cells as compared to splenocytes isolated from chicks vaccinated with wild type or LTB-secreting E. coli and to chicks subcutaneously vaccinated. Significant reduction in viral load and percent of shedders in the vaccinated chicks was evident starting 3 days following challenge with 107.5 EID50/ml virulent IBV. Taken together, orally delivered LTB-fused IBV polypeptide-expressing bacteria induced virus-specific IgY antibody production and was associated with significantly shorter viral shedding on challenge with a live IBV. The proposed vaccine design and delivery route promise an effective and rapidly adaptable means of protecting poultry farms from devastating IB outbreaks.

Phylogenetic analysis of infectious bronchitis virus circulating in southern China in 2016-2017 and evaluation of an attenuated strain as a vaccine candidate.

Avian infectious bronchitis (IB) is a highly contagious viral respiratory disease, caused by infectious bronchitis virus (IBV), that poses an important economic threat to the poultry industry. In recent years, genotypes GI-7, GI-13, and GI-19 have been the most prevalent IBV strains in China. However, in this study, we found that most IBV strains from southern China in 2016–2017 belonged to genotype GVI-1. This genotype, for which there is no vaccine, has been reported sporadically in the region. The GDTS13 strain, which caused severe IB outbreaks on the farms where it was isolated, was evaluated as a candidate vaccine strain. GDTS13 was serially passaged in specific-pathogen-free embryonated chicken eggs for 100 generations to produce GDTS13-F100. Safety testing indicated that GDTS13-F100 had no pathogenic effect on chickens. Additionally, GDTS13-F100 showed an excellent protective effect against GDTS13, with no clinical signs or virus shedding observed in immunized chickens challenged with the parent strain. These findings indicate that GVI-1 has become the most prevalent IBV genotype in southern China and that GDTS13-F100 may serve as an attenuated vaccine to protect against infection with this genotype.Electronic supplementary materialThe online version of this article (10.1007/s00705-020-04851-9) contains supplementary material, which is available to authorized users.

Infectious Bronchitis Virus Immune Responses in the Harderian Gland upon Initial Vaccination.

In recent years, Arkansas Delmarva Poultry Industry (ArkDPI)-derived infectious bronchitis (IB) virus (IBV) vaccines have been used to characterize the immune responses of chickens subsequent to vaccination on day of hatch or beyond. Perhaps because ArkDPI vaccines display increased heterogeneity, the results on cell immune responses have shown ambiguity. In the current study, we investigated the effects of vaccination with a highly stable and homogeneous Massachusetts (Mass)-type vaccine on days 1 or 7 of age on Harderian gland (HG) responses. Confirming previous studies, both IBV serum antibodies and lachrymal IgA levels were greater upon vaccination on day 7 compared with vaccination on day 1 of age. Unlike results with ArkDPI viruses, a clear trend was detected for both B and T cells in the HG after Mass-type vaccination. Consistent with antibody responses, B- and T-helper (CD3+CD4+) cell frequencies were higher in birds vaccinated on day 7 of age. Cytotoxic T cells (CD3+CD8+) were also increased compared with chickens vaccinated on day 1 of age. Depending on the most likely age of IB outbreaks to occur in a particular region, postponing the first IBV vaccination may optimize immune responses.

Nucleotide Sequence Analysis of S1 Gene among Iranian Avian Infectious Bronchitis Viruses Isolated during 2001-2002.

Infectious bronchitis (IB) virus genome codes for four structural proteins, among which the S1 subunit of spike glycoprotein comprises the major epitopes to induce neutralizing antibodies. This study involved the comparison of the full S1 sequences of five IB viruses, namely two Massachusetts and three 793/B serotypes, isolated from IB outbreaks during 2001-2002, with all other Iranian and foreign 793/B isolates and 10 known serotypes. Analysis of S1 subunit showed three unique amino acid changes at positions 349 (V to L), 392 (T to N), and 393 (Q or R to T or K or S) for the Iranian 793/B isolates, compared to those of the foreign 793/B isolates reported before 2006 (onset of vaccination with 793/B vaccine in Iran). They were used as amino acid markers for the differentiation of Iranian 793/B isolates for years. Sequence alignment of the Iranian isolates with those of the foreign ones reported after 2006 demonstrated that amino acids 392 and 393 were no longer considered as amino acid markers, and only the change in amino acid 349 still remained specific to the Iranian 793/B isolates. Phylogenetic tree sequence analysis revealed that the Iranian 793/B isolates were closely related indicating that they came from a single source, more probably from France. There was a very close correlation between the first detection of 793/B serotype and the time of French chicken meat importation. Moreover, it was shown that one of the Massachusetts isolates was completely identical with the H120 vaccine strain. Furthermore, the other Massachusetts isolate with two amino acid changes at positions 64 (G to E) and 95 (S to R) was very similar to this vaccine strain. It seems that the latter isolate is a passaged chicken H120 vaccine strain.

Genetic characterization of S1 gene of infectious bronchitis virus isolated from commercial poultry flocks in West Java, Indonesia.

Background and Aim:Infectious bronchitis (IB) is still a major problem among poultry industry in Indonesia, IB outbreaks continue to happen even in vaccinated flocks. The emergence of new IB virus (IBV) variants might lead to mismatching between vaccine virus strain and circulating virus strain, this may be a reason of vaccination failure. Information about circulating IBV in a region is important to decide which IB vaccine should be used. However, information about recent IBV strains which circulated in Indonesia and their genetic characters were limited; therefore, the aim of our research was to determine the genetic characterization of S1 gene of IBV isolated from commercial poultry flocks in West Java, Indonesia.Materials and Methods:A total of 47 viral isolate samples collected from chickens with clinical sign and reduced in egg production. Six IB live vaccines were used as control, the reference vaccines represent IBV strains including H120, H52, 4/91, CR88, 233A, and 1-96. Primers XCe2+ and XCe2- were used to amplify S1 gene partially.Results:Twenty-six of 47 samples showed positive result to S1 gene of IBV by reverse transcription-polymerase chain reaction. Three IBV isolates, Indonesia/K233A31/18, Indonesia/K4A9/17, and Indonesia/P3/17, were selected for nucleotide sequencing. Phylogenetic analysis of 352 nucleotides of the partial S1 gene shows that isolates Indonesia/K4A9/17 and Indonesia/K233A31/18 have 100% homology with IBV vaccine strain 4/91, while isolate Indonesia/P3/17 has 100% homology with IBV vaccine strain 233A.Conclusion:Our result indicates that at least two IBV strains were circulating among poultry in West Java, Indonesia, which is IBV close to vaccine strain 4/91 and 233A. The present study provides updates on the circulating IBV in commercial poultry flocks in West Java, Indonesia, and might use as guidance on selecting a proper IB vaccine strain to improve IB vaccination efficacy in certain region.

Protection against Infectious Bronchitis Virus, a Corona Virus Infection, Using Ostrich Antibodies

In chickens, infectious bronchitis (IB) is a major respiratory disease. The respiratory system is the primary multiplication site of IB virus (IBV), a coronavirus, after which the virus is distributed to other organs. Poultry farms sustain considerable economic damage due to IB outbreaks in flocks, since IB causes a severe reduction in weight gain in chicks. In the present study, we produced the ostrich IgY against IBV by immunizing female ostriches with the IB viral antigens. The resultant purified IgY showed a strong neutralizing activity against IBV infection of cultured primary chick kidney cells. The infectivity of IBV was markedly inhibited in the trachea of chicks when ostrich IgY was injected intra-muscularly into newly hatched chicks prior to viral inhalation challenge at two weeks of age. Furthermore, the infection was strongly blocked in the tracheae when IgY was injected into chicks at one day and one week of age, with viral inhalation performed at three weeks of age. These findings suggest that the injection of ostrich IgY can help protect young chicks from IBV infections. In south Asian and African countries, broiler chicks are sent to poultry market around 30 days of age, so it is important to prevent IB outbreaks in very young flocks. We strongly believe that ostrich IgY will be a powerful weapon against IB infection in poultry farms on a wide scale and also hope that these findings will aid in the development of antibody vaccines for new type corona viruses, SARS-CoV and MERS-CoV.

Phylogenetic distribution and predominant genotype of the avian infectious bronchitis virus in China during 2008-2009.

BackgroundThe nephropathogenic avian infectious bronchitis (IB) caused unprecedented economic losses to the commercial chicken industry of China in 2008-2009. To investigate the prevalence of nephropathogenic IB in China, eighty IBV isolates from different provinces during 2008-2009 were identified by dwarf embryo test and RT-PCR.ResultsThe strains were mostly isolated in winter and spring with a wide age range of IB outbreaks, from 4 to 69 days. By the virus recovery trials, 70/80 of the strains resulted in the deaths or distresses of birds from nephritis. To learn more about the molecular evolutionary characteristics of the circulating field strains, the coding region of major spike 1 (S1) protein gene of these strains was RT-PCR amplified and sequenced. Compared to the published representative strains, nucleotides and amino acids sequence analysis indicated that the S1 genes of these strains and the reference strains displayed homologies ranging from 75.1% to 99.8% and from 73.1% to 99.8% respectively. S1 protein of the major pandemic strains contained 540 or 542 amino acids with the cleavage site of HRRRR or RRFRR. Phylogenetic analysis revealed that recent field isolates of IBV in China were mostly belonged to A2-branch (QXIBV-branch) and HN08-branch, only one isolate was belonged to Gray-branch and M41-branch respectively. Most of the 80 strains showed evolutionarily distant from vaccine strains.ConclusionsThe results of this study suggested that nephropathogenic IBVs were mainly A2-like strains in China during 2008-2009.

Infectious Bronchitis Virus Surveillance in Ontario Commercial Layer Flocks

Infectious bronchitis (IB) is one of the most important viral diseases of poultry and causes major economic losses to the industry. IB status in commercial layers in southern Ontario was assessed through a questionnaire. According to the data gathered from egg producers of Ontario, repeated outbreaks of IB occurred even though flocks had been routinely vaccinated. Based on this information, 13 farms throughout the region were selected for IB virus (IBV) surveillance. IBV vaccinated and unvaccinated sentinel birds were placed in barns with different IB histories, and after a 1-wk exposure tissues and pharyngeal swabs were collected and tested for the presence of IBV. An initial study indicated that tracheal tissues were more often positive than samples from cecal tonsils, kidneys, lungs, and pharyngeal swabs. Therefore, all subsequent IBV detection was directly on tracheal tissues with nucleocapsid (N) gene specific reverse transcription (RT) polymerase chain reaction (PCR). From the sentinel bird placements and N-gene RT-PCR analysis, IBV was detected on 11 farms with differing IB histories. The study indicated that farms with previous IB outbreaks could harbor the virus without clinical signs in the flocks. In addition, some farms, although they did not report having IB associated problems, were IBV positive by N-gene RT-PCR.

Serotype variation among infectious bronchitis viral isolates taken from several areas of Java

Infectious bronchitis (IB) is an acute highly contagious viral respiratory disease of poultry caused by virus belongs to the family of Coronaviridae. The virus consist of many serotypes with low level of cross-protectivity among serotypes. Field data showed that the outbreaks of IB were frequently reported in chicken flocks, although vaccinations against the disease have been practiced. Hence, the study on serotype relationship among isolates of the viruses is essentially required. The aim of this study was to isolate and characterize IB viruses from chicken flocks in some areas of Java. Isolation of the virus was carried out in nine-day old embrionated chicken eggs and identified by means of agar gel precipitation (AGP) tests against standard antisera to IB virus. The serotypes of the IB viral isolates were determined by cross-neutralization tests in nine day old embryonated chicken eggs using r value derived from homologous and heterologous serum titres as criteria. This study obtained 12 IB viral isolates which were identified on the basis of the ability to cause lesions in chicken embryos and positive to agar gel presipitation test against standard positive antiserum to the virus. Based on the cross-neutralization tests in embryonated chicken eggs, isolate I.9 was formed to have relationship closed to Mass-41 serotype, while I.2, I. 3, and I.7 isolates were closely to the serotype of Con-46. Virus isolates (I.5, I.14, I.24, and I.25) were decided to have no serotype relationships to either Mass-41 or Con-46 serotype. Since the I.5, I.14, I.24 and I.25 isolates were not neutralized by antisera against the previous identified local infectious bronchitis viral isolates, and that were considered to be distinct serotype to the previously identified local IB viral isolates. Key words: Infectious bronchitis, virus, embryonated egg, cross neutralization test.

The Early History of Infectious Bronchitis

Two years later, Bushnell and Brandly (3) reported on an essentially identical disease. They established that the causative agent was a filterable virus because the disease could be transmitted by Berkefeld-filtered material. Because the symptoms of respiratory distress were caused by a filterable virus, Bushnell and Brandly regarded the disease as a form of infectious laryngotracheitis (LT). Further critical tests were not made to confirm this identity. Bushnell and Brandly's report (3) was considered by most later research workers in avian respiratory diseases to actually describe further outbreaks of infectious bronchitis (IB). It was not until much later that the possibility could be considered that some or all of their cases could really have been cases of the mild or lowvirulence type of LT described by Cover and Benton (4). A further source of confusion was that, in the 1930s, the name infectious bronchitis was used in some papers actually describing LT. This confusion was cleared up a few years later by Beach and Schalm (1), who proved by cross-immunity studies in chickens that IB virus was distinct from infectious LT virus and

Antigenic and S-1 Genomic Characterization of the Delaware Variant Serotype of Infectious Bronchitis Virus

A previously unrecognized infectious bronchitis virus (IBV) serotype, referred to hereafter as the Delaware variant (DE var), was isolated from commercial broiler chickens during a severe, widespread respiratory disease epornitic in the Delmarva peninsula region of the United States in January-March 1992. The DE var serotype was found to be antigenically unrelated by virus-neutralization (VN) test to nine reference IBV serotypes from North America. Additional VN tests indicated that the DE var isolates (DE/072/92, DE/121/ 92, DE/152/92, and DE/174/92) from broilers were fully or partially neutralized by monospecific antisera prepared against themselves and against two IBV field isolates (DE/492/90 and DE/903/90) recovered from a Delmarva commercial layer flock experiencing egg production losses in 1990. Antigenic relatedness values determined by VN indicated layer isolate DE/492/90 was more closely related to the broiler DE var isolates than was layer isolate DE/903/90. Cross-challenge tests performed in specific-pathogen-free chickens also demonstrated the antigenic similarity of the broiler (DE/072/92 and DE/174/92) and the layer isolates (DE/492/90 and DE/903/90), with heterologous strain protection values ranging from 55% to 100%. Protection values of DE var isolates vs. Massachusetts 41 and Arkansas DPI were considerably lower (0-60%). The S-1 gene of the US/DE/072/92 isolate of the DE var serotype was amplified by reverse transcription polymerase chain reaction, cloned, and sequenced. The DE var S-1 gene sequence was compared with the S-1 gene sequences of IBV serotypes from North America, Europe, and Australia. A dendrogram based on this analysis supported the conclusion that the DE var serotype is highly novel among IBV. A high degree of similarity (> 88%) was observed between the S-1 genes of the DE var broiler isolates (DE/072/92 and DE/174/92) and layer isolates (DE/492/90 and DE/903/90). These data, taken with the VN and cross-challenge results, establish a genetic as well as an antigenic link between the isolates from layers and broilers and indicate the DE var serotype was responsible for both infectious bronchitis outbreaks.

Diagnosis of Infectious Bronchitis (IB) by Examination of Tracheal Mucus for IB-Precipitating Antigens

The use of tracheal exudates for detecting precipitating infectious bronchitis (IB) antigen by the agar-gel precipitin (AGP) technique is described. Of 47 experimentally infected tracheas, 24 gave positive precipitin lines between the second and 12th day postinfection; 9 out of 18 tracheas from birds from natural outbreaks of IB were also positive. Tests can be read within 18-24 hr. For best results, several antisera or an antiserum at various concentrations should be used.

Infectious Bronchitis Outbreaks in Vaccinated Poultry in Connecticut

Infectious bronchitis (IB) virus was isolated from a large number of cases of respiratory disease in Connecticut chickens. Eight isolates were all characterized as the JMK strain of IB. Most cases occurred in flocks that were well vaccinated with Massachusetts strain IB vaccine and, where tested, exhibited good virus-neutralizing serum titers. Histopathologic lesions in the trachea in acute cases consisted mainly of epithelial hyperplasia with little or no edema or mononuclear infiltration, a lesion pattern that is described as typical of Newcastle disease (ND). However, no ND infections were found in these cases of IB.

Outbreaks of Infectious Bronchitis in Vaccinated Broilers on the Delmarva Peninsula

Twenty-six virus isolations were made from broiler flocks in the Delmarva area experiencing respiratory disease between 3 and 5 weeks following vaccination for infectious bronchitis. The tracheal organ culture technique was used for serotyping by the constant-serum variable-virus serum neutralization test. Twenty-four of the isolates were the JMK type of infectious bronchitis virus. Serological relationships between the JMK, Gray, and Florida strains are reported.