Comparison of vaccination protocols of broiler breeder hens for Pasteurella multocida utilizing enzyme-linked immunosorbent assay and virulent challenge

A commercial enzyme-linked immunosorbent assay (ELISA) to detect serological response to vaccination and virulent challenge with type 1 (X-73) Pasteurella multocida was used to determine the best vaccination protocol for broiler breeders against fowl cholera. Birds vaccinated twice, at 10 and 19 weeks of age, with the avirulent Clemson University (CU) strain both times, with a commercial bacterin first and the CU strain second, or with the CU strain first and bacterin second had the highest survival rates (98-100%) following challenge at 25 weeks. The two groups that received the CU strain and bacterin also produced the highest mean ELISA antibody titers (greater than 10,000). Birds vaccinated once, at 10 weeks, with the CU strain had the same survival rate as birds vaccinated twice with bacterin (90 and 91%). Under the conditions of this experiment, an ELISA titer greater than or equal to 1000 resulted in at least a 92% survival rate after virulent challenge (23% survival in nonvaccinates).     

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.     

Experimental infections with fowl pox in chickens

Seven groups of chickens were challenged with a field isolate of fowl pox virus at 18 weeks old. The birds in the groups that had been vaccinated 3 weeks previously with fowl pox vaccinates showed no signs of disease. Birds which had not been vaccinated against fowl pox developed upper respiratory disease after challenge, and some birds had diphtheritic tracheitis and laryngitis which appeared identical to that commonly seen under field conditions. Seven days after challenge, fowl pox virus was recovered from the tracheas of unvaccinated birds, but not from the vaccinated ones.

Intercurrent Mycoplasma gallisepticum infection appeared to extend slightly the period of respiratory disease but was not essential for development of the diphtheritic lesion.     

Fowl cholera: influence of Bordetella avium on vaccinal immunity of turkeys to Pasteurella multocida

Turkeys exposed to Bordetella avium were vaccinated against fowl cholera with live Pasteurella multocida vaccine. Previous exposure to B. avium resulted in impairment of systemic immunity conferred by the vaccine: 86% of the vaccinated turkeys exposed to B. avium at 1 day old developed lesions or died of fowl cholera after challenge at 15 weeks old with virulent P. multocida. Of vaccinated turkeys not previously exposed to B. avium, only 26% had lesions or died of fowl cholera.     

Immunogenicity and Efficacy of a Commercial Feline Leukemia Virus Vaccine

Twenty young adult specific pathogen-free cats were randomly divided into two groups of 10 animals each. One group was vaccinated with two doses of feline leukemia virus vaccine according to the manufacturer's recommendations. All 20 cats were challenge exposed oronasally (4 times over a 1-week period), beginning 3 weeks after immunization, with a virulent subgroup A strain of FeLV (CT600-FeLV). The severity of the FeLV infection was enhanced by treating the cats with methylprednisolone acetate at the time of the last FeLV exposure. Ten of 10nonvaccinated cats became persistently viremic compared with 0/10 of the vaccinates. ELISA antibodies to whole FeLV were present at high concentrations after immunization in all of the vaccinated cats, and there was no observable anamnestic antibody response after challenge exposure. ELISA antibodies to whole FeLV appeared at low concentrations in the serum of nonvaccinated cats after infection but disappeared as the viremia became permanently established. Virus neutralizing antibodies were detected in 3/10 vaccinates and 0/10 nonvaccinates immediately before FeLV challenge exposure, and in 8/10 vaccinates and 1/10 nonvaccinates 5 weeks later. Although vaccination did not consistently evoke virus neutralizing antibodies, it appeared to immunologically prime cats for a virus-neutralizing antibody response after infection. Active FeLV infection was detected in bone marrow cells taken 14 weeks after infection from 10/10 nonvaccinates and 0/10 vaccinates. Latent FeLV infection was not detected in bone marrow cells from any of the vaccinated cats 14 weeks after challenge exposure.     

Comparison of various antigens and their ability to detect protective antibodies against Pasteurella multocida using enzyme-linked immunosorbent assay

Various antigenic extracts of the CU strain of Pasteurella multocida were prepared to determine their suitability as plate antigens for use in the enzyme-linked immunosorbent assay (ELISA) for the detection of fowl cholera antibodies. Antisera from two separate broiler breeder flocks with known fowl-cholera-vaccination histories were collected just before the birds were challenged with virulent strain X-73 P. multocida. A potassium thiocyanate (KSCN)-extracted antigen, a capsular (CAP) antigen, a lipopolysaccharide-protein antigen, and heat-stable, salt-soluble antigen were all suitable as ELISA plate-coating antigens. Filtered and unfiltered sonicates of the CU strain of P. multocida were also suitable ELISA plate antigens. The results suggested that different plate antigens were detecting different populations of antibodies formed in response to fowl cholera vaccinations. When antibody titers were correlated with survival after challenge, the KSCN and the CAP plate antigens placed more nonsurvivors into low-antibody-titer ranges and more survivors (protected birds) into the high-antibody-titer ranges than the other plate antigens.     

Protection of chickens against highly pathogenic avian influenza virus (H5N2) by recombinant fowlpox viruses.

Two recombinant fowlpox viruses containing the avian influenza H5 hemaglutinin (HA) gene were evaluated for their ability to protect chickens against challenge with a highly pathogenic isolate of avian influenza virus (H5N2). Susceptible chickens were vaccinated with the parent fowlpox vaccine virus or recombinant viruses either by wing-web puncture or comb scarification. Following challenge 4 weeks later with highly pathogenic avian influenza virus, all birds vaccinated by the wing-web method were protected by both recombinants, while 50% and 70% mortality occurred in the two groups of birds vaccinated by comb scarification. Birds vaccinated with the unaltered parent fowlpox vaccine virus or unvaccinated controls experienced 90% and 100% mortality, respectively, following challenge. Hemagglutination-inhibition (HI) antibody levels were low, and agar-gel precipitin results were negative before challenge. Very high HI titers and positive precipitating antibody responses were observed in all survivors following challenge.     

禽Ⅰ型副粘病毒各种禽源分离株的免疫原性

分别制备了源于鸡、鹅、鸽、鹌鹑、孔雀、画眉鸟、珍珠鸡的禽型副粘病毒(APMV-1)7个强毒分离毒株和商品弱毒疫苗株克隆30(C30)的灭活油乳剂苗,并用这8种灭活油乳剂苗和C30株的活疫苗分别在鸡、鹌鹑、鹅和鸽进行了免疫及交叉攻毒保护试验。免疫后(PI)分别测定试验禽血清的新城疫病毒(NDV)血凝抑制(HI)抗体的滴度,并于PI 5周用强毒株进行攻毒。结果表明,鸽的HI抗体几何平均滴度(MAT)为9.00~10.0 log2,鸡的为7.13~7.63 log2,鹌鹑的为5.00~5.13 log2,鹅对灭活油乳剂苗的为5.63~6.38 log2、而对C30株活疫苗的仅为3.38log2;除了C30株活疫苗免疫鹅提供的保护率比较低(20%)外,8种油乳剂苗都能对同源或者异源强毒株的攻毒提供比较高的保护率(66.75%~100%)。研究结果表明,经典疫苗株C30与近年来从各种不同禽类分离的致病性APMV-1野毒株之间、不同禽源分离株之间的抗原性,以及各种不同禽源分离株的之间的免疫原性差异均不大。     

Comparison of enzyme-linked immunosorbent assay and indirect hemagglutination test for quantitating antibody responses in chickens against Pasteurella multocida

An indirect enzyme-linked immunosorbent assay (ELISA) was developed to measure humoral antibody responses of chickens against Pasteurella multocida. A standard indirect hemagglutination (IHA) test was used to compare serologic results with those of ELISA. The ELISA was also used following challenge with P. multocida to compare the efficacy of three commercial fowl cholera vaccination regimens. Although antibody titers measured by ELISA and IHA were highly correlated, ELISA was at least twice as sensitive as IHA. Antibody measured by ELISA and IHA also correlated significantly with protection against P. multocida challenge. No mortality occurred in any of the three vaccinated challenged groups. However, control unvaccinated chickens experimentally infected with P. multocida developed signs of acute pasteurellosis and died by the 10th day post-challenge. Impression smears made of hepatic tissue from all chickens were stained (Wright's stain), and typical bipolar rods characteristic of Pasteurella were identified in smears from unvaccinated challenged controls only.     

Avian influenza mucosal vaccination in chickens with replication-defective recombinant adenovirus vaccine

We evaluated protection conferred by mucosal vaccination with replication-competent adenovirus-free recombinant adenovirus expressing a codon-optimized avian influenza (AI) H5 gene from A/turkey/WI/68 (AdTW68.H5ck). Commercial, layer-type chicken groups were either singly vaccinated ocularly at 5 days of age, singly vaccinated via spray at 5 days of age, or ocularly primed at 5 days and ocularly boosted at 15 days of age. Only chickens primed and boosted via the ocular route developed AI systemic antibodies with maximum hemagglutination inhibition mean titers of 3.9 log2 at 32 days of age. In contrast, single vaccination via the ocular or spray routes maintained an antibody status similar to unvaccinated controls. All chickens (16/16) subjected to ocular priming and boosting with AdTW68.H5ck survived challenge with highly pathogenic AI virus A/chicken/Queretaro/14588-19/95 (H5N2). Single ocular vaccination resulted in 63% (10/16) of birds surviving the challenge followed by a 44% (7/16) survival of single-sprayed vaccinated birds. Birds vaccinated twice via the ocular route also showed significantly lower (P < 0.05) AI virus RNA concentrations in oropharyngeal swabs compared to unvaccinated-challenged controls.     

Comparative evaluation of cell culture-adapted and chicken embryo-adapted fowl pox vaccine strains

Two types of vaccines, chicken embryo adapted (VacCE) and cell culture adapted (VacCC), were tested for their efficacy to elicite the immune response in birds vaccinated at 2 and 8 wk of age. The cell-mediated immune response studied by blastogenesis assay showed that birds vaccinated at the second week of age by both VacCE and VacCC vaccines had significant increase in T-lymphocyte count at 21 days postvaccination (PV) and 7 days postchallenge (PC), whereas in birds vaccinated at 8 wk of age, a significant increase was seen at 21 days PV and 7 days PC with the VacCC vaccine. The rise in passive hemagglutination titers was observed up to 21 days PV and 7 days PC in birds vaccinated at 2 wk of age. However, only the birds vaccinated with VacCC at 8 wk of age showed rise in titers at days 21 PV and 7 PC. Birds were challenged 90 days PV by scarification on the thigh region, and the birds vaccinated with VacCC showed 90% and 70% protection when vaccinated at 2 and 8 wk, respectively. The birds vaccinated with VacCE showed only 60% and 20% protection at the corresponding levels, respectively.     

In vitro and in vivo characterization of avian Escherichia coli. III. Immunization

Broiler breeder hens were vaccinated once at 20 weeks or twice at 20 and 25 weeks of age with a formalin-inactivated oil-emulsion Escherichia coli bacterin composed of serogroups O2, O78, and O35. Serological responses as assessed by microagglutination documented an increase in serotype-specific antibody in vaccinated birds. Challenge of progeny from vaccinates and nonvaccinates with homologous E. coli demonstrated that maternally derived antibody could protect against mortality and/or lesions for as long as 2 weeks post-hatching.     

Coronavirus infection in the laboratory rat: immunization trials using attenuated virus replicated in L-2 cells.

Sixty-nine specific pathogen-free male Wistar rats approximately eight weeks of age were used to evaluate the efficacy of an attentuated strain of sialodacryoadenitis (SDA) virus in providing protection against infection on subsequent challenge with virulent SDA virus. Fifty-four animals were inoculated intranasally with approximately 10(3.5) median cell culture infectious doses of the 25th passage of SDA virus in L-2 cells. Randomly-selected vaccinated animals were killed in order to evaluate the safety and efficacy of attenuated virus by histopathological examination of the salivary glands, lacrimal glands, and lower respiratory tract, and titration of sera for antibody to SDA virus. At three months and six months postvaccination (pv), animals were selected at random and challenged with virulent SDA virus. Seronegative, age-matched animals were also challenged, and served as controls. In animals examined at six to ten days pv, lesions were absent in submandibular and parotid salivary glands and lacrimal glands, but transient lesions were present in major airways of the lower respiratory tract. In a comparison of the incidence and extent of lesions, and antibody titers in challenged vaccinates and seronegative controls, lesions were minimal or absent in vaccinates compared to challenged naive rats, particularly in animals inoculated at three months pv. In addition, antibody titers in challenged vaccinates were much higher than were postinoculation titers in inoculated controls. In a comparison of lesions in salivary and lacrimal glands in vaccinated and control animals challenged at six months pv, there was a significant reduction in the number of animals without lesions in the vaccinated group (p = less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Brucella abortus-specific immunoglobulin isotypes in serum and vaginal mucus from heifers vaccinated with Brucella abortus salt-extractable proteins and challenge exposed with virulent Brucella organisms

Serum and vaginal Brucella-specific immunoglobulin isotypes (IgG1, IgG2, IgM, and IgA), obtained from 62 crossbred beef heifers vaccinated with Brucella abortus salt-extractable proteins and subsequently challenge exposed with B abortus S2308, were studied. Brucella-specific IgG antibodies and Brucella-specific immunoglobulin isotypes were quantitated by a fluorometric immunoassay. Serum and vaginal immunoglobulin responses were evaluated as a method of distinguishing infected from noninfected heifers. Rivanol precipitation, complement-fixation, buffered-antigen brucellosis tests and an ELISA were performed on sera. For immunoglobulin isotypes, vaccinated heifers had mean antibody responses higher than baseline mean antibody responses for at least 31 weeks after vaccination. After challenge exposure, significant differences (P greater than 0.05) were not detected between mean antibody responses of vaccinated and nonvaccinated heifers. Vaginal Brucella-specific antibody responses did not correlate with protection from disease. Vaginal Brucella-specific IgM was detected only at the time of abortion. Vaginal IgA appeared specific for identification of virulent B abortus infection. All serotests appeared adequate in distinguishing baseline titers from titers of heifers that had aborted and were considered bacteriologic culture-positive. Results of serotests neither consistently distinguished vaccinates from challenge-exposed cattle nor distinguished heifers that were challenge exposed, had aborted, and were considered bacteriologic culture-positive adequately from heifers that were challenge-exposed, had not aborted, and were considered bacteriologic culture-negative. Brucella-specific IgA appeared to be the most effective in distinguishing vaccinated heifers from challenge- exposed heifers and heifers that were challenge exposed and had aborted, from heifers that were challenge exposed and had not aborted. Brucella-specific serum IgA was detected up to 13 weeks after abortion.     

Vaccination of calves with Haemonchus placei intestinal homogenate

The ability of adult Haemonchus placei intestinal homogenate to confer protection against homologous challenge infection was evaluated. Calves were immunized twice with 100 microg H. placei intestinal protein in 5% dextran-sulfate/PBS (vaccinates) or PBS alone (controls) and were challenged with approximately 3300 infective H. placei larvae. There was no significant difference between groups in the total number of nematodes recovered but significantly fewer (p < 0.001) adult females were recovered from vaccinates. The proportion of fourth-stage larvae in vaccinates was significantly greater (p < or = 0.05) than in controls. Lengths of adult male and female nematodes were significantly shorter (p < 0.001) in vaccinated calves, and the numbers of eggs present in the uteri of female nematodes from vaccinates were significantly decreased (p < 0.001). Counts of nematode eggs per gram of feces (EPG) of vaccinates were significantly less than that for controls on Days 29-49 post-challenge (p < or = 0.05). Vaccinates had significant increases in serum IgG1 and IgG2 log(10) titers (p < or = 0.05) but not in serum IgM. EPG, numbers of females, and size of males and females were negatively correlated with increased mean post-challenge IgG1 and IgG2 titers. Reduction in binding of periodate-treated gut homogenate by immune serum indicated a carbohydrate specific component in the immune response.     

Studies of infectious laryngotracheitis vaccines: immunity in broilers

Broiler chickens were vaccinated at 18 days of age against infectious laryngotracheitis (ILT) using chicken-embryo-origin (CEO) and tissue-culture-origin (TCO) vaccines, each vaccine given either by drinking water, spray, or eyedrop. Controls were not vaccinated. The broilers were challenged 3 weeks later with virulent ILT virus (USDA challenge strain). Serum samples taken before challenge were analyzed by a virus neutralization (VN) test to determine titers due to vaccination. Both vaccines, regardless of route of administration, produced low VN titers, geometric mean titer (GMT) being less than 4.0 in all vaccinated groups. When administered by the same route, the CEO vaccine produced higher titers than the TCO vaccine. Titers following drinking-water or eyedrop administration of vaccines were higher than titers following spray vaccination. There was an inverse relationship between pre-challenge VN titers of groups of birds and the percentage of birds in the groups dying from ILT virus challenge. The drinking-water route of vaccination provided the most protection, while the spray provided the least.     

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.     

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.     

Evaluation of pathogenicity of avian poxvirus isolates from endangered Hawaiian wild birds in chickens

Pathogenicity of two avian poxviruses isolated from endangered Hawaiian wild birds, the Hawaiian Goose and the Palila, was compared with fowl poxvirus in chickens. Immune responses were measured by ELISA pre- and postimmunization with Hawaiian poxviruses and after challenge with fowl poxvirus. Both isolates from Hawaiian birds developed only a localized lesion of short duration at the site of inoculation in specific-pathogen-free chickens and did not provide protection against subsequent challenge with virulent fowl poxvirus. On the other hand, birds inoculated with virulent fowl poxvirus developed severe lesions. In contrast to high antibody response in chickens immunized with fowl poxvirus, birds immunized with either of the two Hawaiian isolates developed low to moderate antibody responses against viral antigens. The level of immune responses, however, increased in birds of all groups following subsequent challenge.     

Response of broiler chickens to fowl cholera vaccination at 1 to 6 weeks of age.

Broiler chickens, in groups of 10, received a single vaccination by the stick-wing route at 1, 2, 3, 4, 5, 6, or 11 weeks of age with live Clemson University strain of Pasteurella multocida. Twenty non-vaccinates kept in isolation served as controls. Cholera serum antibody titers in all chickens were determined by enzyme-linked immunosorbent assay at weekly intervals. Chickens vaccinated once at 1, 2, 3, 4, 5, and 6 weeks, respectively, attained 25.2%, 28.7%, 34.7%, 46.2%, 51.8%, and 64.6% of the titers of those vaccinated once at 11 weeks of age. Variation in antibody response was greatest in chickens vaccinated at 1 or 2 weeks of age. Additionally, chickens vaccinated at 1 or 2 weeks of age showed the longest response time (5 weeks) to reach maximum antibody titers after a single vaccination. When the original vaccinates were revaccinated at 11 weeks of age, all showed a secondary response equal to or greater than that seen in chickens vaccinated once at 11 weeks of age. Age of the chickens at the time of vaccination and antibody titer were positively correlated (r = 0.997). Overall antibody responses to vaccination were higher and much more uniform as birds increased in age.