Infectious Bronchitis Virus Types Affecting European Countries-A Review.

Since its first detection in Europe in the 1940s, infectious bronchitis virus has continued to be one of the major respiratory pathogens affecting the European poultry industry. The development of effective and widely used vaccines for both broilers (live attenuated) and breeders and layers (live attenuated and inactivated) helped improve the health and welfare of poultry but never eliminated the problem. The main reason is the continual emergence of new infectious bronchitis variants (serotypes or genotypes). This review discusses the most prevalent genotypes of the last few decades in Europe. Some of these genotypes seem to be local European types; others have an origin outside Europe.

Estudio recapitulativo- Tipos del virus de la bronquitis infecciosa que afectan a los países europeos: Una revisión. Desde su primera detección en Europa en la década de los 1940s, el virus de la bronquitis infecciosa ha seguido siendo uno de los principales patógenos respiratorios que afectan a la industria avícola europea. El desarrollo de vacunas eficaces y ampliamente utilizadas tanto para pollos de engorde (vivos atenuados) como para reproductoras y ponedoras (vivos atenuados e inactivados) ayudó a mejorar la salud y el bienestar de las aves comerciales, pero nunca eliminó el problema. El problema principal es la aparición continua de nuevas variantes de bronquitis infecciosa (serotipos o genotipos). Esta revisión analiza los genotipos más prevalentes en las últimas décadas en Europa. Algunos de estos genotipos parecen ser tipos europeos locales; otros tienen un origen fuera de Europa.

The use of an enzyme-linked immunosorbent assay to detect IgG antibodies to serotype-specific and group-specific antigens of fowl adenovirus serotypes 2, 3 and 4.

A sensitive enzyme-linked immunosorbent assay (ELISA) has been developed which can detect serotype and group-specific antibodies (IgG) to fowl adenovirus serotypes 2, 3 and 4. The chickens produced principally type-specific antibodies after a single oral inoculation of virus which enabled that strain to be identified by the ELISA. However, inoculation of an heterologous serotype, although inducing strain-specific antibodies to itself, also induced high levels of antibody to the group-specific antigens. This masked the serotype-specific antibodies in the ELISA to the first serotype. The ELISA, which has similar sensitivity to the serum neutralisation test, could be used as a rapid, easily performed test to identify fowl adenovirus-specific antibodies.

A method for the rapid purification of serum IgM for the diagnosis of recent viral infections of chickens.

The rapid purification of chicken IgM from serum was achieved by affinity chromatography. IgM immunoadsorbent gels were prepared using monoclonal antibodies specific to chicken IgM. Five different eluting agents were compared for the dissociation of the adsorbed IgM; the most convenient for routine purposes was 2 M NaCl, Tris-HCl, EDTA (NTE), as this enabled direct assay of eluents by ELISA without requiring the intermediate step of dialysis, which the other eluting agents did. Eluents prepared from sera obtained from infectious bronchitis virus (IBV) and infectious laryngotracheitis (ILTV)-infected chickens, together with samples of the same serum fractionated by gel chromatography, were tested by ELISA for virus-specific antibodies and to confirm the identity of the antibody class. In the case of both IBV and ILTV, similar results were obtained using immunoaffinity and gel chromatography. IBV-specific IgM, as determined by both methods in the ELISA, reached its highest concentration at the 8th day after inoculation and was virtually absent by the 24th day, whilst the highest concentration of ILT-specific IgM was detected at 6 days and no or little IgM was present at 16 days after inoculation. Purification of serum IgM by affinity chromatography followed by ELISA was considered suitable for routine serological diagnosis of IB and ILT, since the time required to complete the assay (3 hours) was considerably less than that for gel chromatography and many samples could be assayed simultaneously.

Infectious bronchitis virus vaccine interferes with the replication of avian pneumovirus vaccine in domestic fowl.

Experiments were performed in chickens to ascertain whether application of infectious bronchitis (IB) H120 vaccine had an effect on the replication of an attenuated avian pneumovirus (APV) strain, using as indicators virus detection, humoral antibody responses and clinical protection against in vivo APV challenge. A preliminary experiment demonstrated that pharyngeal swabs were as efficient for recovery of APV as were buccal cavity swabs, and that either site was superior to swabbing the nasal cavity. APV was detected to a similar extent by both a reverse transcriptase-polymerase chain reaction (RT-PCR) and virus isolation; therefore, RT-PCR was used in subsequent experiments. In chickens vaccinated with APV alone, APV was detected by RT-PCR in most birds for 1 week after vaccination. When IB vaccine had been applied 1 week earlier, APV detection was delayed and much reduced. This interference by IBV resulted in a lower APV antibody response to vaccination. Following challenge with virulent APV, birds that had been vaccinated with APV alone were fully protected both clinically and virologically. Chickens that had received both vaccines were still protected clinically, but challenge virus could be detected in some pharyngeal swabs 4 days after challenge. In contrast, the APV vaccine had no effect on either the antibody response to the IB vaccine or the level of protection against IB challenge. It is concluded that IB vaccination interferes with the replication of APV, resulting in a reduction in the antibody response but with no adverse effect on the induction of protective immunity.

Protection of chickens against renal damage caused by a nephropathogenic infectious bronchitis virus.

The ability of the infectious bronchitis (IB) Ma5 and 4/91 live-attenuated vaccines to protect against kidney damage caused by a nephropathogenic strain of IB virus (B1648) was investigated. Protection parameters considered were gross and microscopic renal pathology, and the use of a polymerase chain reaction to detect IB RNA in kidney tissue. By each parameter, Ma5 vaccine alone provided poor protection, but 4/91 alone or the combined program both protected well.

Cloning, expression and immunogenicity of the avian pneumovirus (Colorado isolate) F protein.

The F protein of the Colorado isolate of avian pneumovirus (APV), expressed from a DNA plasmid, was recognized by antiserum to both A and B subgroup APVs. After two intramuscular injections of turkeys with this plasmid, a homologous antibody response was detected by enzyme-linked immunosorbent assay. This antibody also recognized subgroup A APV. However, there was no neutralization of the Colorado isolate or of subgroup A or B viruses. Although no significant clinical protection was detected following homologous challenge of poults, an anamnestic serological response was seen, suggesting that a systemic antibody response but no local mucosal immunity was induced.

Avian pneumovirus infection of laying hens: experimental studies.

Administration of a virulent strain of avian pneumovirus (APV) to specific pathogen free laying hens by the oculonasal route failed to induce a drop in egg production or any adverse effects on eggshell quality. However, intravenous (i.v.) inoculation of the same strain caused a substantial drop in egg production and a high incidence of soft and thin-shelled eggs. Some respiratory signs were also observed and the hens appeared sick, with diarrhoea being observed in approximately one-half of the hens between 4 and 11 days post-inoculation (p.i.). APV antigen was detected in the oviduct epithelium up to 9 days p.i. This challenge model was then used to investigate the efficacy of live attenuated turkey rhinotracheitis (TRT) vaccine administered alone at 1 day old, or an inactivated TRT vaccine (at 16 weeks), or a combined programme using both vaccines, in protecting against this challenge. Neither the live nor the inactivated vaccine alone protected against clinical signs (respiratory infection or diarrhoea). However, the inactivated, but not the live, vaccine did protect against the effect of the i.v. challenge on laying performance. In contrast, the combined vaccination programme protected completely against both clinical signs and poor egg-laying performance. This protection lasted until at least 60 weeks of age. On the basis of the results with this experimental model, it is concluded that the use of live priming followed by administration of inactivated TRT vaccine is necessary to provide complete protection of laying chickens against APV challenge.

Antibiotic resistance of Escherichia coli strains isolated from chickens with colisepticaemia in Morocco.

Sixty-two strains of Escherichia coli were isolated in 58 farms from broiler chickens showing respiratory signs and lesions characteristic of avian colibacillosis. Serological examination of these strains showed that the types 078, 01 and 02 (for the somatic antigen) and K1 (for the capsular antigen) were the most frequently found. Newcastle disease virus was also isolated in two cases. All the strains of E. coli isolated were sensitive to colistin, flumequine and gentamicin. A few strains were resistant to neomycin, nalidixic acid and trimethoprim. The frequency of strains resistant to nitrofurans, sulfonamides, chloramphenicol, spectinomycin and ampicillin was intermediate. Most strains were resistant to tetracycline. Multiple resistance was common.

Escherichia coli multiplication and lesions in the respiratory tract of chickens inoculated with infectious bronchitis virus and/or E. coli.

Escherichia coli numbers and histopathological changes were studied in the respiratory tract of line 151 chickens intranasally inoculated with infectious bronchitis virus (IBV) and/or virulent E. coli; this line is highly susceptible to IBV. Chickens inoculated with IBV alone showed increased numbers of E. coli in the trachea and had tracheitis, airsacculitis, and bronchiolitis. One of 17 chickens inoculated with IBV alone died with fibrinopurulent serositis. Chickens inoculated with IBV and E. coli had more severe and persistent respiratory lesions than those inoculated with IBV alone. E. coli was isolated from tracheas of chickens inoculated with IBV and E. coli more frequently than from chickens inoculated with IBV alone. In this group, 14 of 27 chickens died with tracheal plugs or with fibrinopurulent serositis. There was neither increased numbers of E. coli nor significant lesions in the respiratory tract of the group inoculated with E. coli alone. These results suggest that IBV may facilitate E. coli invasion into the lower respiratory tract of the chicken.

IgM responses in chicken serum to live and inactivated infectious bronchitis virus vaccines.

Intramuscular (i.m.) administration of infectious bronchitis virus (IBV) oil-emulsion vaccine (OEV) to IBV-primed or unprimed chickens resulted in the production of zero or minimal concentrations of IBV-specific IgM in the serum, as measured by enzyme-linked immunosorbent assay of gel chromatography fractions. Live-attenuated infectious bronchitis (IB) vaccine given i.m. or by eyedrop stimulated the production of IBV-specific IgM in similar amounts following inoculation by both routes. These levels were comparable to those found in earlier studies following intranasal inoculation with a virulent strain of IBV and confirm that the detection of IBV-specific IgM is a valuable aid to the diagnosis of recent infection. As expected, administration of live-attenuated IB vaccines i.m. or by eyedrop protected the respiratory tract against challenge with virulent virus 24 days later; however, OEV given i.m. did not.

Characterization of infectious bronchitis viruses isolated from outbreaks of disease in commercial flocks in Brazil.

Fifteen isolations of infectious bronchitis (IB) virus were made from a total of 126 Brazilian poultry flocks of all ages that were examined. These flocks (14 chicken and 1 quail) were experiencing a variety of IB-like conditions including respiratory disease, digestive and kidney problems, and drops in egg production. One of the isolates was of the Massachusetts serotype. The remainder were examined by means of cross-neutralization tests in tracheal organ cultures and were shown to belong to at least four antigenic groups, all different from ones described previously in other countries. Some, but not all, of the flocks from which they were isolated had been vaccinated against IB with vaccines of the Massachusetts serotype. In vivo protection studies showed that the MA5 vaccine (of the Massachusetts serotype) protected well against challenge with four of these isolates, representing the different serotypes reported in this study.

The susceptibility of chicken kidney and oviduct organ cultures to a vaccine strain of avian infectious bronchitis virus.

The minimal infectious dose of the H52 strain of infectious bronchitis virus for organ cultures of oviduct and kidney was compared in chickens of different ages. Organ cultures of oviduct were found to be highly susceptible to infection regardless of the age of chicken and no difference in susceptibility could be demonstrated between cultures of the magnum and uterus regions of the mature oviduct. Kidney organ cultures were less susceptible and resistance to infection increased significantly (P less than 0.001) with the age of the chicken from which cultures were prepared.

Growth kinetic studies of avian infectious bronchitis virus in tracheal organ cultures.

An egg-adapted vaccine strain (H120) and an organ culture-passaged field strain (HV-10) of avian infectious bronchitis (AIB) virus were propagated in tracheal organ cultures and their growth kinetics examined using nine-day-old embryonated fowl eggs and chick tracheal explants for virus assay. When the H120 strain was assayed in embryonated eggs, titres were approximately log10 2-0 ID50 (50 per cent infectious dose) per ml higher than when assays were performed in tracheal explants. The HV-10 strain, assayed in tracheal explants, yielded higher titres than did the H120 strain, but when assayed in embryonated eggs, yielded only minimal and variable virus titres.

Avian pneumovirus infections of turkeys and chickens.

Avian pneumoviruses (APVs) cause major disease and welfare problems in many areas of the world. In turkeys the respiratory disease and the effect on egg laying performance are clearly defined. However, in chickens, the role of APV as a primary pathogen is less clear, although it is widely believed to be one of the factors involved in Swollen Head Syndrome. The mechanisms of virus transmission over large distances are not understood, but wild birds have been implicated. APV has recently been reported in the USA for the first time and the virus isolated was a different type or possibly a different serotype from the APVs found elsewhere. Good biosecurity is crucial for controlling infection and highly effective vaccines are available for prophylaxis. Although different subtypes and possibly different serotypes exist, there is good cross protection between them. Diagnosis is usually based on serology using ELISAs, but the available kits give variable results, interpretation is difficult and improved diagnostic tests are required.

Avian rhinotracheitis.

Turkey rhinotracheitis, now commonly termed avian pneumovirus (APV) infection, is associated with serious welfare and economic problems in susceptible populations of turkeys and probably also of chickens. The infection principally affects the upper respiratory tract, although egg-laying performance may also be affected in breeding turkeys. Secondary infections exacerbate the effects of the primary virus infection. The virus persists for only a short time both in the host and in the environment and is not known to be transmitted via the egg. Highly effective vaccines are available to control APV infections, and hence good biosecurity and careful use of these vaccines should enable infection to be controlled and spread restricted. Diagnosis and surveillance are normally performed serologically using enzyme-linked immunosorbent assays (ELISAs). Several different ELISA kits are available commercially, but these give variable results and are not wholly satisfactory since interpretation of results is difficult.

Comparison of the susceptibility of chicks of different ages to infection with nephrosis/nephritis-causing strain of infectious bronchitis virus.

Two- and 6-week-old chicks were inoculated with the Kagoshima-34 strain of avian infectious bronchitis virus. Serum, bile, Harderian gland, lachrymal fluid, saliva and tracheal washings were collected and their antibody content determined using neutralisation tests. The neutralising antibody (NA) in the serum and bile was detected earlier and in slightly higher concentration in the 6-week-old chicks. Although there was no marked difference in the levels of NA in other body fluids, it was detected earlier in the 6-week-old chicks. In both experiments, the clinical signs were more severe in the 2-week-old chicks. Recovery of virus from the trachea of both ages was not different but virus was recovered for longer in the lungs, kidneys and colon of the 2-week-old chicks. This is the first report wherein IBV-neutralising antibody in the bile is described.

Demonstration of serum-neutralising antibody to turkey rhinotracheitis virus in serum from chicken flocks in Japan.

Since between 1989 and 1991, broiler, broiler breeder and layer chickens reared in three different prefectures of Japan, Hyogo, Ibaraki, and Miyazaki, were diagnosed clinically as having swollen head syndrome (SHS) these flocks were survey for antibody to turkey rhinotracheitis (TRT) virus using a serum neutralisation (SN) test. TRT-specific SN antibody was found in flocks of chickens in 2 out of the 3 prefectures. Thereafter, particular in the summers of both 1993 and 1994 outbreaks of SHS occurred in almost all areas of major chicken production in Japan. Almost chicken flocks affected by SHS possessed TRT SN antibody. No chicken sera collected between 1972 and 1988 possessed any SN antibody to TRT virus. It is suggested that in Japan, TRT virus is widely prevalent in areas of major poultry production.

Whatever happened to the General Surgery graduating class of 2001?

PURPOSE: Nationally approximately 20% of all categorical General Surgery (GS) residents do not complete their GS training. We ranked 57 applicants in the National Residency Match Program (NRMP) in 1996 and matched our final eighth candidate with slot 22. Although clinically stellar, 4 of these 8 residents (50%) opted to switch to different medical specialties. We pondered if other programs had difficulties with the 1996 applicant pool and hypothesized that perhaps higher ranked applicants have greater attrition rates. METHODS: Programs in which our ranked applicants matched were contacted and asked for feedback on trainee performance, research time, attrition, and future plans. RESULTS: Four applicants did not match in GS. Fifty-three surgical interns (46 men, 7 women) in 1996 are now 23 chief residents, 18 senior residents (16 did research time, 1 did an intensive care unit fellowship, and 1 required a year of remediation), and 12 non-GS trainees (orthopedic surgery = 3, anesthesiology = 3, ENT = 1, family medicine = 1, internal medicine = 1, radiology = 1, pathology = 1, and Ph.D. researcher = 1). Clinical performance was similar for both GS trainees and those who dropped out. Residents dropped out after the PG-1 year (n = 7), PGY-2 (n = 3), and 1 each after PGY-3 and PGY-4. Higher ranked applicants were no more likely to drop out than were lower ranked applicants. CONCLUSIONS: Of Mayo Clinic-Rochester-ranked GS categorical applicants in 1996, 23% dropped out of GS. Eleven of 12 dropouts selected a different field of medicine to finish their training. Attrition remains common and problematic both nationally and in individual programs.

Genetic differences in susceptibility of chicken lines to infection with infectious bursal disease virus.

Mortality rates in 11 inbred and partially inbred chicken lines inoculated with a very virulent strain (CS89) of infectious bursal disease virus (IBDV) varied considerably, being highest (almost 80%) in a Brown Leghorn line (BrL). Bursa of Fabricius to body weight ratios were depressed in the survivors in each line, but no differences were observed between lines. However, histological examination of bursae from survivors showed that, although bursal damage occurred in every line, it was most severe in the two lines (BrL and White Leghorn W1) in which the highest mortality was recorded. Experiments with F1 matings between highly susceptible and highly resistant lines showed that resistance was partially dominant and that there were no maternal effects. Experiments using F2 and backcross chicks suggested the involvement of a single gene and indicated no involvement of the MHC. There was considerable variation between lines in IBDV-specific antibody, measured by ELISA, both in the vaccinated parent hens and in the amounts of inherited maternal antibody and its rate of decay in the progeny.

Characterisation of an infectious bronchitis virus isolated from vaccinated broiler breeder flocks.

Four apparently serologically closely related isolates of infectious bronchitis virus were obtained from two flocks of vaccinated broiler breeders, one mile apart, which were experiencing increased mortality and decreases in egg production. The isolates were serologically distinct from isolates previously described and capable of causing characteristic infectious bronchitis-like respiratory infection in young chicks. In one experiment, the H120 vaccine strain of the virus did not protect the trachea against challenge with the new isolates 21 days later.