The history, current situation and control measures for infectious bronchitis virus (IBV) variants are reviewed. A large number of IBV variants exist worldwide; some being unique to a particular area, others having a more general distribution. The possible reasons why some strains spread readily over major parts of the world, whereas other strains stay more localized are discussed. The advantages and disadvantages of strain classification by protectotyping, serotyping and genotyping are discussed in relation to in vivo protection. The different vaccination strategies are also considered.

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Infectious bronchitis virus variants: a review of the history, current situation and control measures

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S1 gene-based phylogeny of infectious bronchitis virus: An attempt to harmonize virus classification.

Newcastle disease vaccines-A solved problem or a continuous challenge?

Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis were used to differentiate between serotypes of several infectious bronchitis virus (IBV) strains. A sequence of 1720 base pairs (bp) that contains the S1 glycoprotein gene of IBV was amplified by PCR, purified, and digested with restriction enzymes. Eleven reference IBV strains were grouped according to the RFLP patterns. The IBV Holte, Arkansas DPI, SE 17, Md 27, and Iowa 97 strains could be differentiated from the other IBV strains using the restriction enzyme HaeIII. The Beaudette, Massachusetts 41, Connecticut, and Florida 88 strains had the same HaeIII RFLP pattern but could be differentiated using XcmI and BstYI restriction enzymes. The Gray and JMK strains could not be differentiated by their RFLP patterns following digestion with 23 different restriction enzymes. Twenty-six samples (field isolates and reference strains) of IBV, previously serotypes by the virus-neutralization (VN) test in embryonating eggs, were analyzed in a blind fashion. The results using the PCR and RFLP analysis agreed with the serotype for traditional and variant IBV viruses as determined by the VN test.

Differentiation of infectious bronchitis virus serotypes using polymerase chain reaction and restriction fragment length polymorphism analysis.

Newcastle disease virus (NDV) is classified as a member of the superfamily Mononegavirales in the family Paramyxoviridae. This virus family is divided into two subfamilies, the Paramyxovirinae and the Pneumovirinae. In 1993 the International Committee on the Taxonomy of Viruses rearranged the order of the Paramyxovirus genus and placed NDV within the Rubulavirus genus among the Paramyxovirinae. The enveloped virus has a negative sense single-stranded RNA genome of 15,186 kb which codes for an RNA directed RNA polymerase, hemagglutinin-neuraminidase protein, fusion protein, matrix protein, phosphoprotein and nucleoprotein in the 5' to 3' direction. The virus has a wide host range with most orders of birds reported to have been infected by NDV. Isolates are characterized by virulence in chickens and are categorized into three main pathotypes depending on severity of disease. Lentogenic isolates are of low virulence while viruses of intermediate virulence are termed mesogenic. Highly virulent viruses that cause high mortality in birds are termed neurotropic or viscerotropic velogenic. Velogenic NDV are List A pathogens that require reporting to the Office of International Epizootics and outbreaks result in strict trade embargoes. The primary molecular determinant for NDV pathogenicity is the fusion protein cleavage site amino acid sequence. Vaccination for NDV is primarily by mass application of live-virus vaccines among commercial poultry. Although protection is measured by presence of antibodies to NDV, vaccinated B-cell depleted chickens are resistant to disease. Consequently, immune protection involves responses that are presently incompletely defined.

The avian response to Newcastle disease virus.

Recombinant strains of herpesvirus of turkeys (HVT) were constructed that contain either the fusion protein gene or the hemagglutinin-neuraminidase gene of Newcastle disease virus (NDV) inserted into a nonessential gene of HVT. Expression of the NDV antigens was regulated from a strong promoter element derived from the Rous sarcoma virus long terminal repeat. Recombinant HVT strains were stable and fully infectious in cell culture and in chickens. Chickens receiving a single intra-abdominal inoculation at 1 day of age with recombinant HVT expressing the NDV fusion protein had an immunological response and were protected (> 90%) against lethal intramuscular challenge at 28 days of age with the neurotropic velogenic NDV strain Texas GB. Recombinant HVT expressing the NDV hemagglutinin-neuraminidase provided partial protection (47%) against the same challenge. Chickens vaccinated with recombinant HVT vaccines had low levels of protection against NDV replication in the trachea when challenged ocularly. Recombinant HVT vaccines and the parent HVT strain provided similar levels of protection to chickens challenged with the very virulent RB1B strain of Marek's disease virus, indicating that insertion of foreign sequences into the HVT genome did not compromise the ability of HVT to protect against Marek's disease.

https://www.jstor.org/stable/pdfplus/1591544.pdf

Protection of Chickens From Newcastle and Marek's Diseases With a Recombinant Herpesvirus of Turkeys Vaccine Expressing the Newcastle Disease Virus Fusion Protein

Five isolates, from broiler-type chickens, capable of causing acute respiratory disease were identified as infectious bronchitis virus (IBV). The agar-gel precipitin (AGP) test was effective in identifying the isolates as IBV. Virus-neutralization (VN) and cross-challenge tests indicated two of the isolates to be Massachusetts types and one to be a JMK type. The remaining isolates were different from strains normally encountered in chickens reared on the Delmarva Peninsula. One isolate, although serologically similar to the Connecticut strain, was able to infect Connecticut-virus-immune chickens. Another isolate was similar to Arkansas 99, a strain not previously reported in Delmarva.

Serologic and cross-protection studies with several infectious bronchitis virus isolates from Delmarva-reared broiler chickens.

SUMMARY. Restriction endonuclease (RE) digestion patterns of six Delmarva field isolates of infectious laryngotracheitis virus (ILTV) were compared with three standard reference strains. With one exception, all of the field isolates generated RE digestion patterns identical to an embryo-propagated vaccine strain of ILTV when the six-base-recognizing REs EcoRI, HindIII, PstI, and BamHI were used. In order to increase the sensitivity of the RE analysis technique, a more sensitive DNA fingerprinting approach using four-base-recognizing enzymes was developed. One field isolate could be differentiated from the embryo-propagated vaccine strain using all three enzymes, Sau3AI, MspI, and Hinfl. A second isolate could be differentiated only by comparing HinfI digestion patterns. This work provides additional evidence that differentiable strains of ILTV exist in the United States. Furthermore, currently used RE analysis methods may not be sensitive enough to discriminate between field isolates and vaccine strains of ILTV, thus challenging the theory that vaccine strains of ILTV are responsible for field outbreaks of infectious laryngotracheitis. RESUMEN. Anilisis con endonucleasas de restricci6n de cepas del virus de laringotraqueitis infecciosa de Delmarva. Se compararon los patrones del virus de laringotraqueitis infecciosa obtenidos mediante el anilisis con endonucleasas de restricci6n, de seis cepas de campo aisladas en Delmarva con tres cepas de referencia. Con una excepci6n, todas las cepas de campo generaron patrones que fueron identicos a los de una cepa vacunal de laringotraqueitis propagada en embriones, cuando se usaron las endonucleasas de restricci6n EcoRI, HindIII, PstI y BamHI que reconocen seis bases.

Restriction endonuclease analysis of Delmarva field isolates of infectious laryngotracheitis virus.

Twenty-seven cases of type C botulism were studied in integrated broiler operations on the Delmarva Peninsula. Single and repeated outbreaks in broiler flocks were observed. No botulinum toxin was found in litter and feed samples despite repeated testing. Clostridium botulinum type C was cultured from litter, feed, and tissues of morbid and clinically normal chickens sampled from farms in which flocks experienced botulism. Clostridium botulinum type C could not be cultured from tissues of clinically normal chickens taken from a farm without a flock history of botulism or from caged broilers reared in semi-isolation.

https://www.jstor.org/stable/pdfplus/1590044.pdf

Cases of type C botulism in broiler chickens.

SUMMARY. A group of avian reoviruses comprising serially passaged S 1133 strains and their vaccine derivatives was examined biochemically to study the temporal evolution of the viruses and biologically to assess their relative pathogenicities. The strains fell into three groups of differing virulence, the viruses becoming less pathogenic the longer they were passaged. Protein and RNA profiles of the strains showed no distinct patterns of evolution nor any trend that could be correlated with pathogenicity. Nucleic acid hybridization studies of the strains indicated that all the genes were altered to some extent during passage. The Si and M3 genes appeared to change the most during the first half of passage history, but later, as the virus was cold-adapted or passaged extensively, the M2, S2, and S3 genes also appeared to vary. When viruses were grouped according to virulence, the greatest changes were seen in the Si, M2, and M3 genes, suggesting that these may be associated with the virulence of a given avian reovirus strain.

John K. Rosenberger

Papers

Protection of Chickens From Newcastle and Marek's Diseases With a Recombinant Herpesvirus of Turkeys Vaccine Expressing the Newcastle Disease Virus Fusion Protein

Serologic and cross-protection studies with several infectious bronchitis virus isolates from Delmarva-reared broiler chickens.

Restriction endonuclease analysis of Delmarva field isolates of infectious laryngotracheitis virus.

Cases of type C botulism in broiler chickens.

Association of avian reovirus M and S genes with viral behavior in vivo. II. Viral pathogenicity.