Fowl cholera immunity in broiler breeder chickens determined by the enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies in broiler breeders vaccinated (wing web) with the CU fowl cholera vaccine. Birds were bled weekly from 9 to 26 weeks, every other week from 26 to 40 weeks, and every 4 weeks from 40 to 56 weeks of age. Overall mean ELISA antibody titers (9 to 56 weeks) reported as log10 values and survivability of the vaccinates after virulent challenge were as follows: unvaccinated--5.75, 48%; birds vaccinated once at 8 weeks--5.91, 78%; birds vaccinated twice at 8 and 14 weeks--6.11, 100%; birds vaccinated thrice at 8, 14, and 20 weeks--6.23, 100%; birds vaccinated twice at 8 and 20 weeks--6.12, 100%; and birds vaccinated twice at 8 and 20 weeks (plus fowl pox at 8 weeks)--6.08, 95%. Survivability in the vaccinates after virulent challenge with strain X-73 Pasteurella multocida was 100% in birds with ELISA antibody titers (log10) greater than 6.02. Under the conditions of this experiment, birds vaccinated two or three times between 8 and 20 weeks proved to be sufficiently immune at 56 weeks of age to withstand a virulent fowl cholera challenge. Birds not vaccinated or vaccinated only once at 8 weeks were not sufficiently immunized to withstand virulent challenge.     

An epornitic of avian pox in a research aviary

An outbreak of avian pox in a bird research colony was reported. Although 10 species of passerine birds were housed within the facility, clinical signs and mortality were restricted to canaries and house sparrows. Post-mortem lesions initially occurred in the upper and lower respiratory tracts and were characterized by proliferative rhinitis, proliferative bronchopneumonia, and proliferative airsacculitis, and diphtheritic lesions occurring in the esophagus were characterized by proliferative granulomatous esophagitis. Cutaneous lesions occurred subsequently in some birds, and a diagnosis was made by histopathology, electron microscopy, and virus isolation. The occurrence of diphtheritic lesions in pox infections of wild birds has been rare, and a sparrow showed an unusual combination of both diphtheritic and acute systemic lesions previously undescribed.     

Failure of a recombinant fowl poxvirus vaccine containing an avian influenza hemagglutinin gene to provide consistent protection against influenza in chickens preimmunized with a fowl pox vaccine

Vaccines against mildly pathogenic avian influenza (AI) have been used in turkeys within the United States as part of a comprehensive control strategy. Recently, AI vaccines have been used in control programs against highly pathogenic (HP) AI of chickens in Pakistan and Mexico. A recombinant fowl pox-AI hemagglutinin subtype (H) 5 gene insert vaccine has been shown to protect specific-pathogen-free chickens from HP H5 AI virus (AIV) challenge and has been licensed by the USDA for emergency use. The ability of the recombinant fowl pox vaccine to protect chickens preimmunized against fowl pox is unknown. In the current study, broiler breeders (BB) and white leghorn (WL) pullets vaccinated with a control fowl poxvirus vaccine (FP-C) and/or a recombinant fowl poxvirus vaccine containing an H5 hemagglutinin gene insert (FP-HA) were challenged with a HP H5N2 AIV isolated from chickens in Mexico. When used alone, the FP-HA vaccine protected BB and WL chickens from lethal challenge, but when given as a secondary vaccine after a primary FP-C immunization, protection against a HP AIV challenge was inconsistent. Both vaccines protected against virulent fowl pox challenge. This lack of consistent protection against HPAI may limit use to chickens without previous fowl pox vaccinations. In addition, prior exposure to field fowl poxvirus could be expected to limit protection induced by this vaccine.     

Construction and immunogenicity studies of recombinant fowl poxvirus containing the S1 gene of Massachusetts 41 strain of infectious bronchitis virus

The spike 1 (S1) surface glycoprotein of infectious bronchitis virus (IBV) is the major inducer of the generation of virus neutralizing antibodies, and the administration of purified S1 has been shown to elicit a protective immune response against virulent virus challenge. On the basis of these observations, recombinant fowl poxvirus (rFPV) containing a cDNA copy of the S1 gene of IBV Mass 41 (rFPV-S1) was constructed and its immunogenicity and vaccine potential were evaluated. Initially, rFPV-S1 was shown to express the S1 in vito by indirect immunofluorescence staining and western blot analyses. Later, in vivo expression was demonstrated by the detection of IBV-specific serum immunoglobulin G and neutralization antibodies in the sera of chickens immunized with rFPV-S1. That the recombinant virus elicited anti-IBV protective immunity was indicated by the manifested, relatively mild clinical signs of disease, decreased titers of recovered challenge virus, and less severe histologic changes of the tracheas in virulent IBV Mass 41-challenged chickens previously receiving rFPV-S1 as compared with parental fowl poxvirus (FPV)-vaccinated control birds. In contrast, chickens immunized with either recombinant or parental FPV were resistant to a subsequent virulent FPV challenge. As to a preferred method of immunization, wing web administration appeared to be superior to the subcutaneous route because a greater percentage of birds vaccinated by the former protocol exhibited an anti-IBV humoral immune response. Thus, rFPV-S1 has potential as a poultry vaccine against both fowl pox and infectious bronchitis.     

Immune response of chicks to oral vaccination against Newcastle disease and fowl pox

The humoral immune response and immunity conferred in chicks were compared following separate and combined oral vaccination with F strain of Newcastle disease virus (NDV) and HP1 strain of fowl pox virus. The haemagglutination inhibition (HI) antibody titre against NDV and passive haemagglutination (PHA) antibody titre against fowl pox virus were comparable in two respective groups. The serum IgG concentration increased significantly after the second vaccination in all the groups. The NDV vaccine induced significantly higher IgG production as compared to fowl pox virus vaccine. There was no significant difference in serum IgG concentration produced by combined vaccine and separate F strain vaccine. The protection afforded by combined and separate vaccinations did not vary significantly against challenge with virulent strains of NDV and fowl pox virus at different stages.     

Prevention of bovine respiratory syncytial virus infection and clinical disease by vaccination

A double blind field trial was carried out with a live attenuated bovine respiratory syncytial virus vaccine. The trial involved 530 calves, two to 10 months old, on 27 dairy farms, where respiratory problems due to bovine respiratory syncytial virus infections had been observed during the preceding year. In 17 herds either all calves were vaccinated (nine groups) or all calves received a placebo (eight groups). In 10 herds half the number of calves were vaccinated and the other half kept as non-vaccinated controls. Calves were vaccinated intramuscularly twice with an interval of four to five weeks. These groups were under regular clinical observation and animals were tested periodically for antibodies to bovine respiratory syncytial virus and parainfluenza type 3 virus. Serological examination indicated that no bovine respiratory syncytial virus infection had occurred prior to the first vaccination in August. Vaccination did not cause adverse reactions. Low concentrations of neutralising and complement fixing antibodies were induced by vaccination and a sharp increase of antibody titres was observed after natural infection of vaccinated animals. Infections with bovine respiratory syncytial virus occurred in six out of eight non-vaccinated groups, in nine out of 10 partly vaccinated groups and in only two out of nine completely vaccinated groups. Virus infection in completely vaccinated groups was significantly reduced compared with partly vaccinated and non-vaccinated groups. The incidence of bovine respiratory syncytial virus lower respiratory disease was significantly reduced in completely vaccinated groups compared to non-vaccinated groups. Generally only mild signs of upper respiratory disease were present in completely vaccinated groups after bovine respiratory syncytial virus infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Investigations on the Influence of Helminth Parasites on Vaccination of Chickens against Newcastle Disease Virus under Village Conditions

Prevalence studies have shown that almost 100% of free-range chickens are infected with a wide range of parasites. The infections are mostly subclinical in nature, resulting in production losses and occasionally mortality. Newcastle disease (ND), on the other hand, results in high mortality rates during epidemics. ND is a limiting factor for increasing poultry production in many tropical countries, where frequent reports indicate vaccination failures. The aim of our study was to investigate the influence of helminths on the antibody response after vaccination against Newcastle disease of free-range chickens naturally infected with parasites. Sixty chickens were divided into six groups, of which three were vaccinated against ND with a live De Soto vaccine, while the other three remained non-vaccinated. One group within the vaccinated groups and the one within the non-vaccinated group was kept naturally infected with helminth parasites, while the other two groups in each set were dewormed with fenbendazole and niclosamide, and one of each of these groups was subsequently infected with Ascaridia galli. After vaccination, all the groups were followed for 5 weeks and their antibody titres were determined weekly using a HI test. All the birds were finally challenged 4 weeks after vaccination with a virulent velogenic ND virus obtained from a field outbreak. All the vaccinated chickens seroconverted and had high antibody levels after 3 weeks, but these dropped to low levels at 4 weeks after vaccination. After challenge, the antibody titres rose in the dewormed groups but not in the parasite-infected groups. After 5 weeks, all the parasite-infected animals had significantly lower antibody titres than the dewormed animals. All the vaccinated chickens survived the challenge infection, emphasizing the importance of the cellular immune response. Further studies are needed to examine the effects of the parasitic infection on protection against ND over a longer period.     

Effect of cyclophosphamide immunosuppression on the immunity of turkeys to viral rhinotracheitis.

Turkey poults, free of antibodies to turkey rhinotracheitis (TRT) virus were treated with cyclophosphamide on days 1, 2 and 3 after hatching and vaccinated by eyedrop when 10 days old with a Vero cell-attenuated preparation of TRT virus. No ELISA antibodies to TRT virus developed in the sera of these poults but they were as resistant to virulent virus challenge 21 days later as vaccinated groups which were not cyclophosphamide-treated but produced humoral antibodies. Following challenge with virulent virus at 31 days old cyclophosphamide-treated unvaccinated poults developed a more severe clinical response than untreated birds and had higher virus titres in tracheal swabs. The findings show that the respiratory tract of turkeys may be resistant to TRT despite the absence of ELISA antibodies in the serum.     

A case control study of fowl pox in southeastern Ontario

An outbreak of fowl pox, which occurred in south-eastern Ontario between July 1988 and April 1989, was investigated in the spring of 1989 to determine factors associated with the spread of the disease. Clinical fowl pox was confirmed on five farms (cases). Twenty-seven farms, out of 35 egg producers with quota from Durham region to Northumberland county, provided information as controls. Bivariate analyses were performed on mail survey data using Fisher's exact test and odds ratios. Although the tests of hypotheses lacked statistical power because of the small number of case farms, and barns, a number of significant associations were found. At the farm level, fowl pox infection was associated with pullets purchased from a particular pullet grower. At the barn level, fowl pox infection was associated with pullets from a particular grower, mixing different groups of pullets, and a trend towards having birds early in the laying period, and higher numbers of birds placed. Fowl pox-infected barns had higher mortality and lower egg production postoutbreak. The results may indicate that the virus enters the laying barn at, or near, the time new birds are placed. Better communication among producers, catch-and-fill crews, and others associated with the egg industry, as well as more complete records of dates, sources, and persons involved with pullet placements, are recommended.     

Immunization against psittacine pox

Pox virus isolated from psittacine birds was used as a vaccine in trials with love birds (Agapornis roseicollis). The vaccine was applied by wing-web puncture using single- and double-needle applicators. Immunity was effective against challenge with virulent psittacine pox virus administered via the feather follicle/thigh. When unvaccinated contact control birds were placed with the vaccinated individuals immediately post-vaccination, virus spread was evident. However, susceptible birds placed with vaccinated ones at 27 days postvaccination remained uninfected for 11 weeks. The importance of a high vaccine virus titer was observed.     

In vivo evaluation of vaccine efficacy against challenge with a contemporary field isolate from the α cluster of H1N1 swine influenza virus

Influenza A virus vaccines currently contain a mixture of isolates that reflect the genetic and antigenic characteristics of the currently circulating strains. This study was conducted to evaluate the efficacy of a trivalent inactivated swine influenza virus vaccine (Flusure XP) in pigs challenged with a contemporary α-cluster H1N1 field isolate of Canadian swine origin. Pigs were allocated to vaccinated, placebo, and negative-control groups and monitored for respiratory disease for 5 d after challenge. On the challenge day and 5 d after challenge the serum of the vaccinated pigs had reciprocal hemagglutination inhibition antibody titers 40 for all the vaccine viruses but ≤ 20 for the challenge virus. Gross lesions were present in the lungs of all pigs that had been inoculated with the challenge virus, but the proportion of lung tissue consolidated did not differ significantly between the placebo and vaccinated pigs. However, the amount of virus was significantly reduced in the nasal secretions, lungs, and bronchoalveolar lavage fluid in the vaccinated pigs compared with the placebo pigs. These results indicate that swine vaccinated with Flusure XP were partially protected against experimental challenge with a swine α-cluster H1N1 virus that is genetically similar to viruses currently circulating in Canadian swine.     

Fowl cholera immunity induced by various vaccines in broiler minibreeder chickens determined by enzyme-linked immunosorbent assay

Broiler minibreeder hens were vaccinated for protection against fowl cholera at 12 and 21 weeks of age using several vaccination schemes, which included a live Pasteurella multocida (CU strain) vaccine, two commercial polyvalent fowl cholera oil-based bacterins, and two experimentally prepared polyvalent oil-based bacterins. Some treatment groups received only live or killed vaccines, whereas others received a live vaccine at 12 weeks followed by a killed product at 21 weeks. At 42 weeks of age, all birds that received the live CU vaccine twice or once followed by a bacterin survived challenge. Birds that received killed vaccines only were significantly less protected but still showed a respectable survival rate of 86%. All unvaccinated controls died within 72 hr after challenge. At 72 weeks of age, overall protection was lower than that at 42 weeks, regardless of vaccination treatment. Antibody titers were usually higher in birds that received bacterins than in those receiving live vaccines, yet overall protection was still greater in those birds that received the live cholera vaccine twice.     

Immunogenicity of Mycoplasma gallisepticum

The serological response and protective immunity elicited in the chicken by the pathogenic Ap3AS strain and the moderately pathogenic 80083 strain of Mycoplasma gallisepticum and variants of strain 80083 attenuated by repeated passage in mycoplasma broth were investigated. Strain 80083 elicited a substantial serum antibody response after administration either in drinking water or by conjunctival sac instillation to 7-week-old SPF chickens. No vaccinated chickens developed air sac lesions when challenged by intra-abdominal (IA) injection with the virulent Ap3AS strain. Chickens vaccinated with strain 80083M (50 broth passages) showed only a weak serological response but were substantially protected when challenged 4 weeks after vaccination. Chickens vaccinated with 80083H (100 broth passages) were serologically negative 4 weeks after vaccination and developed severe air sac lesions after challenge. Thirty-seven-week-old hens vaccinated 6 months previously with strain 80083 had high serum antibody levels and were completely protected against IA challenge with the homologous strain. However, 4/6 showed mild air sac lesions when challenged intra-abdominally with strain Ap3AS. Another group showed high M. gallisepticum serum antibody levels 6 months after vaccination with strain Ap3AS but 4/6 and 2/6 showed mild lesions after IA challenge with strains Ap3AS or 80083, respectively. Strains 80083 or 80083M were administered by conjunctival sac instillation to susceptible 11-week-old commercial pullets at the time of fowl pox vaccination. The concurrent use of both vaccines had no apparent adverse effect on the health of the chickens. Similar protection against IA challenge with strain Ap3AS was produced with the M. gallisepticum vaccines whether used alone or in combination with fowl pox.     

Protective efficacy of commercial inactivated Newcastle disease virus vaccines in chickens against a recent Korean epizootic strain

Despite the intensive vaccination policy that has been put in place to control Newcastle disease virus (NDV), the recent emergence of NDV genotype VII strains in Korea has led to significant economic losses in the poultry industry. We assessed the ability of inactivated, oil-emulsion vaccines derived from La Sota or Ulster 2C NDV strains to protect chickens from challenge with Kr-005/00, which is a recently isolated Korean epizootic genotype VII strain. Six-week-old SPF chickens were vaccinated once and challenged three weeks later via the eye drop/intranasal route. All vaccinated birds were fully protected from disease, regardless of the vaccine strains used. All vaccinated and challenged groups showed significant sero-conversion 14 days after challenge. However, some vaccinated birds, despite being protected from disease, shed the challenge virus from their oro-pharynx and cloaca, albeit at significantly lower titers than the unvaccinated challenged control birds. The virological, serological, and epidemiological significance of our observations with regard to NDV disease eradication is discussed.     

Serological examination and egg production of progeny of fowl experimentally infected with egg drop syndrome 1976 virus

Following EDS'76 virus (BC14 virus) infection of breeder chickens by the conjunctival route, vertical transmission occurred in the first week after infection. In the progeny which had been infected with EDS'76 virus by the vertical route, increasing haemagglutination inhibiting (HI) titres to BC14 virus and increasing numbers of birds with HI titres were observed from 3 weeks to 15 weeks of age. Sixty-one per cent of the hens and 77 per cent of the cocks had 2 log HI BC14 virus titres exceeding 4 at an age of 15 weeks. Some birds which han been serologically negative throughout the rearing period, seroconverted between 25 and 28 weeks of age. This phenomenon occurred in hens as well as in cocks. Simulation of stress twice during the laying period by injection of corticosteroid hormone did not increase the number of birds serologically positive to EDS'76 virus. EDS'76 was observed in the group of hens that was vertically infected, since egg production was significantly depressed between 28 and 34 weeks of age. Probably this was mainly the results of a production drop in the hens showing serconversion at 27 or 28 weeks of age. In this group of fowl vertically infected with EDs'76 virus, serologically positive birds appeared to be protected for the greater part to BC14 virus challenge at 50 weeks of age, while negative birds seemed to be fully susceptible. Chicks hatched from eggs collected in the third and fourth week after infection of the dams had maternal antibodies. Fertility and hatchability of apparently normally shelled eggs seemed not to be affected after BC14 virus infection of the dams. Intensive contact with contaminated faeces is probably an indispensable condition for lateral transmission of the virus.     

Transmission studies involving a wet fowl pox isolate

An isolate of fowl pox (FP) virus from a case of "wet" pox in commercial white leghorn (WL) pullets was used to expose WL cockerels via the comb-scratch (CS), eye-drop (ED), or laryngeal-swab (LS) route. Seven days postinoculation (PI), the groups challenged via CS had scabby proliferative pox lesions at the challenge site, the groups challenged via LS had slight dyspnea and rales, and 20% of the cockerels challenged via ED had mild conjunctivitis and lacrimation. By termination of the trial on day 21 PI, the CS-challenged groups had developed pronounced pox lesions. The LS-challenged groups showed severe dyspnea and rales with pronounced raised plaque-like lesions at the opening to the trachea and extending into the upper quarter of the trachea with heavy yellowish caseous exudate partly occluding the glottis. The ED-challenged groups had severe lacrimation and conjunctivitis and small pox lesions on the face, comb, and wattles; 12 of 18 had proliferative lesions on the oral mucosa in the area of the larynx. Forty-five percent of the LS-challenged groups died of suffocation. Pox virus was re-isolated from tissues in all treatment groups. Wet pox transmission appears to be possible via the LS and ED routes.     

A canine parainfluenza viral vaccine: immunogenicity and safety.

A canine parainfluenza viral vaccine was developed and shown to be safe by absence of clinical disease in vaccinated dogs and by inability to isolate vaccine virus from blood or nasopharyngeal swabs. Backpassage in susceptible dogs, using blood of vaccinated dogs, could not be demonstrated. The vaccine produced neutralizing antibody when administered either intramuscularly or subcutaneously; however, a significantly higher immune response was obtained by intramuscular inoculation. Differences in the antibody response were not produced by tenfold dilutions of vaccine virus ranging from 10(2.9) to 10(5.9) median tissue culture infective doses. The presence of neutralizing antibody was associated significantly with decreased respiratory shedding period of challenge virus by vaccinated dogs compared to seronegative control dogs. Six days after aerosol exposure to virulent challenge virus, 100% of the controls (n = 5) but only 15% of the vaccinated dogs (n = 3) shed virus. Seven days after challenge exposure, virus could not be recovered from the vaccinated dogs, but 80% of the control dogs shed virus. An anamnestic response occurred in vaccinated dogs but not in the seronegative control dogs following challenge exposure. A mild clinical disease was produced in 3 of the 5 seronegative control dogs but not in the 20 vaccinated dogs.     

Serological examination and egg production of progeny of fowl experimentally infected with Egg Drop Syndrome 1976 virus

Summary

Following EDS'76 virus (BC14 virus) infection of breeder chickens by the conjunctival route, vertical transmission occurred in the first week after infection. In the progeny which had been infected with EDS'76 virus by the vertical route, increasing haemagglutination inhibiting (HI) litres to BC14 virus and increasing numbers of birds with HI litres were observed from 3 weeks to 15 weeks of age. Sixty‐one per cent of the hens and 77 per cent of the cocks had ²log HI BC14 virus litres exceeding 4 at an age of 15 weeks.

Some birds which had been serologically negative throughout the rearing period, seroconverted between 25 and 28 weeks of age. This phenomenon occurred in hens as well as in cocks. Simulation of stress twice during the laying period by injection of corticosteroid hormone did not increase the number of birds serologically positive to EDS'76 virus.

EDS'76 was observed in the group of hens that was vertically infected, since egg production was significantly depressed between 28 and 34 weeks of age. Probably this was mainly the result of a production drop in the hens showing seroconversion at 27 or 28 weeks of age.

In the group of fowl vertically infected with EDS'76 virus, serologically positive birds appeared to be protected for the greater part to BC14 virus challenge at 50 weeks of age, while negative birds seemed to be fully susceptible. Chicks hatched from eggs collected in the third and fourth week after infection of the dams had maternal antibodies. Fertility and hatchability of apparently normally shelled eggs seemed not to be affected after BC14 virus infection of the dams. Intensive contact with contaminated faeces is probably an indispensable condition for lateral transmission of the virus.     

Comparison of duration of immunity in chickens infected with a live infectious bronchitis vaccine by three different routes.

Three groups of chicks were vaccinated by aerosol, intra-ocular and drinking water routes with a live infectious bronchitis (IB) vaccine. At one, two, six, 15 and 32 weeks after vaccination five birds from each group were sampled for testing for IB haemagglutination-inhibiting (HI) antibodies and challenged. Assessment of susceptibility to infection was measured by recovery of virus from individual tracheas and from kidney and gonad pools four days after challenge. Virus was isolated from all kidney and gonad pools of birds challenged one week after vaccination, the kidney and gonad pools of the drinking water vaccinates at two weeks, the kidney pool of the intra-ocular group at 15 weeks and all organ pools except the gonads of the intra-ocular group at 32 weeks. Tracheal resistance was found in most of the birds challenged one week after vaccination and in all the birds tested at two weeks but had begun to wane by six weeks after vaccination. No correlation was found between low HI antibody titres of individual birds and their susceptibility to challenge measured by reisolation of virus from the traches, but birds with titres over log2 6 were always resistant.     

Protection of laying hens against infectious bronchitis with inactivated emulsion vaccines

Commercially-reared laying chickens were challenged at 31 weeks of age with a virulent infectious bronchitis (IB) virus. They showed a sharp drop in egg production, despite having been vaccinated at four and eight weeks old with live attenuated IB vaccines to a recommended schedule. In contrast, similar birds that had been further immunised at point-of-lay with inactivated oil emulsion IB vaccine, or with a combined IB/Newcastle disease (ND) emulsion vaccine, showed no detectable fall in egg production after the same challenge. Unvaccinated susceptible specific pathogen-free birds challenged at the same time stopped laying almost completely. In the birds revaccinated with emulsion vaccine, measurement of haemagglutination inhibition antibody levels to IB showed their geometric mean titres to be raised from less than 5 log2 at the time of vaccination to over 10 log2 four weeks later. Their antibody levels did not rise further followining the IB challenge whereas in the birds that had not been revaccinated antibody rises to nearly 10 log2 were detected after the same challenge. For pullets vaccinated earlier with live IB vaccine, revaccination with inactivated IB or IB/ND oil emulsion vaccine at point-of-lay provides a safe and effective way of protecting their egg production against IB infection.