Virulence of raptor-origin Pasteurella multocida in domestic chickens.

Pasteurella multocida belonging to somatic serotype 1 and capsular type A has been known to cause avian cholera in domestic poultry. Pasteurella multocida serotype 1 has also been isolated from raptorial birds. However, the capsular type for these raptorial isolates remains unknown. Moreover, the virulence of these raptorial isolates for domestic poultry has not been determined. The objectives of this study were to determine the capsular type of raptorial P. multocida serotype 1 isolates and to determine if these isolates were virulent for domestic chickens. Study chickens were inoculated with one of three P. multocida isolates. Isolate WESO-1 was obtained from a western screech owl (Otus kennicottii) and isolates RTHA-2 and RTHA-4 were isolated from two red-tailed hawks (Buteo jamaicensis). These isolates were given by either the oral, intravenous, or intraocular route. Control birds were given brain-heart infusion broth. The capsular serotypes of three isolates were also determined. The RTHA-2 and RTHA-4 isolates belonged to P. multocida capsular type A. The WESO-1 isolate belonged to capsular type F. Results also demonstrated that, for the isolates examined, the intraocular route did not cause mortality in chickens. There was mortality in all groups for the intravenous route. However, various mortality patterns were observed when P. multocida was given orally for the three different isolates. The RTHA-4 isolate (serotype 1:A) was the most virulent for domestic chickens. The WESO-1 isolate (serotype 1:F) was the least virulent for chickens among the raptorial isolates examined.     

Safety and efficacy of the avirulent Mycoplasma gallisepticum strain K5054 as a live vaccine in poultry

A Mycoplasma gallisepticum (MG) isolate from an atypically mild outbreak in turkey breeders was found to be similar to house finch isolates by DNA analyses. A preliminary study in turkeys showed that this isolate (K5054) caused very mild lesions and protected turkeys against subsequent challenge with a virulent MG strain. In this study, K5054 was further evaluated as a potential vaccine strain in commercial layer-type chickens and turkeys. The safety of K5054 was evaluated by aerosol challenge followed by evaluation of gross and histopathologic lesions as well as serologic reactions and isolation of MG from the trachea and air sacs. Infection of chickens (trial 1) and turkeys (trial 2) with K5054 resulted in little evidence of MG lesions. There was weak seroconversion, and K5054 was consistently reisolated from the tracheas of chickens and turkeys. The efficacy of K5054 as a vaccine was evaluated by aerosol challenge of vaccinated chickens (trial 3) and turkeys (trial 4) with virulent R strain. There was evidence of protection from lesions associated with MG.     

Pathogenicity of recent isolates of infectious bursal disease virus in specific-pathogen-free chickens: protection conferred by an intermediate vaccine strain

The pathogenicity of recent isolates of infectious bursal disease virus and the protection conferred against them by a commercial vaccine strain of intermediate virulence were examined in specific-pathogen-free chickens. Based on clinical signs, mortality, and macroscopic lesions in susceptible chickens, the isolates designated as A-Delmarva and U-28 were distinct from a previously known serotype I virulent isolate (Edgar). Histopathological analysis of the bursa of Fabricius did not establish differences between the field isolates. Although the vaccine strain produced some degree of bursal damage in antibody-free chickens, it was significantly less severe than the damage caused by the field isolates. The active immune response induced by vaccination was cross-protective against the pathological effects produced by the different isolates used in this study.     

Protection of chickens by ribosomal vaccines from Pasteurella multocida: dependence on homologous lipopolysaccharide

Chickens were protected against fowl cholera by ribosomal vaccines prepared from noncapsulated Pasteurella multocida. Passive hemagglutination (PHA) titers to lipopolysaccharide (LPS) and the degree of protection conferred by ribosomal vaccines were diminished or abolished when ribosomes were chromatographed on an immunoadsorbent column. Addition of subimmunogenic amounts of serotype 1 (homologous) LPS to highly purified ribosomes resulted in vaccines that protected against challenge exposure and produced PHA titers to homologous LPS. Addition of serotype 5 LPS to highly purified ribosomes did not protect chickens against challenge exposure with serotype 1 P multocida, but produced PHA titers to serotype 5 LPS. Combinations of serotype 1 ribosomal RNA and serotype 1 (homologous) LPS did not protect chickens or produce PHA titers to LPS. Purified ribosomes from Brucella abortus, Aspergillus fumigatus, and chicken liver were combined with LPS from P multocida and were evaluated as vaccines. Brucella abortus and A fumigatus ribosomes combined with LPS protected chickens as well as did bacterin made from whole cells of P multocida. Chicken liver ribosomes combined with LPS did not provide protection. To determine whether a protein carrier would substitute for ribosomes, methylated bovine albumin (MBA) was combined with LPS and evaluated as a vaccine. A serologic response to LPS was induced by MBA-LPS vaccine, but the vaccine offered no better protection than when LPS was used alone as vaccine. Ribosome-LPS vaccines produced serologic responses to LPS that were at least 5-fold greater than those produced by MBA-LPS vaccine.     

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.     

Isolation of very virulent Marek''s disease viruses from vaccinated chickens in Australia

Very virulent Marek's disease viruses (vvMDV), defined as isolates against which the herpesvirus of turkey (HVT) vaccine provide poor protection, have been isolated from poultry flocks in both the United States and Europe. Twenty-one samples from vaccinated Australian flocks, experiencing problems with excessive Marek's disease (MD), were tested for the presence of transmissible MD viruses (MDV). Of the 16 samples which contained a transmissible agent, 14 were pathogenic in chickens, based on the development of MD lesions or depression of the bursa/body weight ratio. Of the pathogenic isolates which have been successfully typed 10 were serotype 1, and one was serotype 2 MDV. Pathogenicity of isolates varied. Several isolates caused tumours in 20-30% of both vaccinated and unvaccinated chickens. Two isolates, MPF6 and MPF23, caused tumours in more than 50% of chickens. When MPF6 and MPF23 were tested in vaccine trials bivalent vaccine gave no better protection against development of MD lesions than a monovalent vaccine. Isolate MPF23 was so pathogenic that lesions were produced in all chickens, regardless of the vaccine protocol used. Therefore vvMDV have been isolated in Australia, and unlike the vaccines tested overseas, bivalent Australian vaccines do not appear to provide greater protection against these vvMDV.     

禽大肠杆菌病免疫保护机理的研究

以禽病原性大肠杆菌O18、O78分离株制成超声波裂解铝佐剂灭活苗免疫14日龄鸡，以相同或不同外膜蛋白型（Outer membrane protein pattern,OMP型）的O18、O78分离株攻毒。结果表明：O78血清相同和不同OMP型分离株间能获得最大保护；O18血清型相同OMP型分离株间获得最大保护，而不同OMP型分离株间不能保护；上述两个血清型的分离株间不论OMP型是否相同，均缺乏保护。以间接ELISA试验、间接血凝试验分别测定了试验鸡临攻毒前针对大肠杆菌OMPs和脂多糖(Lipopolysaccharide,LPS）的抗体。结果表明：免疫组鸡血清上述两种抗体明显高于攻毒对照组；在免疫组，存活鸡临攻毒前血清中上述两种抗体滴度恒高于死亡鸡，但除3个组外，多数组差异不显著。攻毒对照组这一关系不稳定。结果说明：禽大肠杆菌疫苗的免疫保护，主要与O血清型有关，部分与OMP型有关，如O18分离株，免疫保护性抗原含OMPs,LPS等多个抗原表位。     

鸡马立克氏病三价疫苗的安全性及免疫效力研究

将MD三价疫苗以25000PFU／只的剂量颈部皮下接种1日龄SPF雏鸡，结果表明，疫苗的接种不影响鸡体重的增加；不引起鸡法氏囊、脾脏等组织器官发生MD组织病理学变化，对鸡安全无毒性。用SPF鸡评价MD三价疫苗的免疫效力，三批疫苗对RB1B超强毒株攻击的平均保护效力为95．99％，而且无论是用RB1B超强毒株还是用BJMDV-1血毒攻击，MD三价疫苗的保护效力明显高于HVT＋SB1二价疫苗及HVT冻干苗，好于CV1988疫苗；接种MD三价疫苗的4个品系的商品鸡群，抗RB1B超强毒株攻毒的平均保护效力为94．60％；在模拟MD强毒自然传染的试验中，MD三价疫苗的保护效力达到95．65％。上述效力试验的结果说明：MD三价疫苗的免疫接种可使鸡形成抗MD强毒攻击的坚强免疫力。     

Experimental trials with a thermostable Newcastle disease virus (strain I2) in commercial and village chickens in Tanzania

Antibody responses in indigenous village and commercial chickens vaccinated with 12 thermostable Newcastle disease (ND) vaccine and protection levels against challenge with a virulent field isolate were determined. The antibody response of village chickens vaccinated by eye drop revealed that 30, 60 and 90 days after primary vaccination, the mean log2 HI titres were 6.1, 5.4 and 3.6, respectively, whereas for commercial chickens, the antibody response after 14, 30 and 90 days were 8.2, 5.1 and 4.2, respectively. Village chickens vaccinated orally via drinking water had mean log2 HI titres of 3.4 after 30 days. After booster vaccination, the mean HI titre was 5.4 and 3.3 after 30 and 60 days post-secondary vaccination (i.e. 60 and 90 days after primary vaccination). Antibody response of mean log2 HI titres of 2.6 was recorded 30 days after primary vaccination orally through food; 30 and 60 days after secondary vaccination (i.e. 60 and 90 days after primary vaccination), mean log2 HI titres were 5.3 and 3.2, respectively. All commercial and village chickens vaccinated by eye drop survived the challenge trial whereas village chickens vaccinated through drinking water and food had protection levels of 80% and 60% 30 days after primary vaccination, respectively. However, 30 days after booster vaccination, the protection level was 100%. At 60 days after secondary vaccination, the protection level dropped again to 80% for chickens vaccinated orally. All control chickens used in the challenge trials developed clinical ND and died 3-5 days after inoculation with the virulent virus. Supported by laboratory findings, I2 strain of NDV seemed to be avirulent, immunogenic and highly protective against virulent isolates of NDV. It may be a suitable vaccine to use in village chickens to vaccinate them against ND in rural areas.     

新城疫La Sota疫苗对山东分离株的免疫保护试验

用标准疫苗株La Sota活疫苗在隔离器中接种SPF鸡,进行免疫保护试验.免疫后,每7 d采血监测NDV抗体,免疫后2周,利用经过鉴定的新城疫病毒(NDV)潍坊毒SGM01、昌乐毒SCL03、东营毒HY、日照毒SRZ03、莘县毒SSX03和标准强度F48E9分别进行攻毒试验,同时设SPF鸡对照.每天观察,及时剖检发病鸡,检查鸡群病变,确定疫苗的保护性.结果表明,La Sota疫苗能对除SGM01和HY以外的病毒攻击的SPF鸡提供较好的保护.     

Comparison of live avirulent M-9, Minnesota, and CU fowl cholera vaccines

The M-9 and Minnesota (MN) avirulent Pasteurella multocida vaccines were evaluated and compared with the Clemson University (CU) vaccine, which had been shown to be highly effective in preventing fowl cholera in turkeys. Neither the M-9 nor the MN vaccine given in the drinking water was as effective as the CU vaccine in protecting turkeys against challenge with virulent P. multocida. When grown in brain-heart infusion (BHI) agar as recommended, the M-9 was not as efficacious as when it was grown in BHI broth. The M-9 was as effective as the CU vaccine only when grown in BHI broth and given at 10 times the standard dosage. Injection of the M-9 vaccine into the air spaces of the head at a site near the caudal rim of the ear after one vaccination in the drinking water was not as effective for hyperimmunizing potential breeders as was the CU vaccine injected at the same site. A microtiter agglutination test demonstrated a significant (P less than 0.05) correlation between the level of anti-P. multocida antibody found 1 week after vaccination and survival after challenge with virulent P. multocida.     

Embryo vaccination with infectious bursal disease virus alone or in combination with Marek's disease vaccine

Studies with specific-pathogen-free chickens revealed that chicks hatching from eggs inoculated at the 18th day of embryonation with infectious bursal disease (IBD) vaccine viruses of low virulence (isolates TC-IBDV and BVM-IBDV) developed antibody against IBD virus (IBDV) and resisted challenge with virulent IBDV at 3 weeks of age or older. Embryo vaccination did not adversely affect hatchability of chicks or survival of hatched chicks. Chicks embryonally vaccinated with TC-IBDV had transient histologic lesions in the bursa of Fabricius at hatch. Similar but milder lesions were also noted in chickens that received TC-IBDV at hatch. The level of protection following embryo vaccination with TC-IBDV and BVM-IBDV was similar to that following vaccination with the same vaccines at hatch. Vaccine viruses of moderate virulence (isolates BV-IBDV and 2512-IBDV) were not suitable as vaccines in embryos lacking maternal antibody to IBDV, because the vaccinated chicks developed acute IBD after hatch. Isolate 2512-IBDV was not pathogenic for embryos bearing maternal antibody to IBDV. Maternal antibody against IBDV interfered with efficacy of embryo vaccination with BVM-IBDV but not with 2512-IBDV. Embryo vaccination with a mixture of vaccines against IBD and Marek's disease resulted in protection of hatched chicks against challenge with virulent IBDV and Marek's disease virus.     

Efficacy of a trivalent Haemophilus paragallinarum vaccine compared to bivalent vaccines.

The efficacy of a trivalent oil-adjuvant Coryza vaccine containing serotypes A, B and C of Haemophilus paragallinarum has been compared with that of a bivalent oil-adjuvant Coryza vaccine containing serotypes A and C and that of a commercially available, bivalent A1(OH)3-potentiated vaccine, containing types A and C. The trivalent vaccine, given at 10 and 17 weeks of age, provided the best protection. Even at 55 weeks after booster vaccination, chickens were still significantly protected, following severe challenge with either of the three serotypes of Haemophilus paragallinarum. Both bivalent vaccines did not protect against type B challenge. Furthermore the oil-adjuvant vaccines induced higher HI-A titers, which correlate with protection, compared to the A1(OH)3-potentiated vaccine. The results show that type B strains are pathogenic and constitute a distinct immunotype and thus a Coryza vaccine should contain three serotypes to obtain a broader protection against all serotypes.     

Attenuated live fowl cholera vaccine. I. Development of vaccine strain M3G of Pasteurella multocida

A live cholera vaccine was developed from a virulent avian septicemia strain of Pasteurella multocida serotype 1. The virulent parental strain was mutagenized with N-methyl-N'-nitro-N-nitroso guanidine. Mutants were selected that had either smaller colonies at 37 C or temperature sensitivity for growth at 41 C. Four small-colony mutants and 2 temperature-sensitive mutants were studied. All the mutants were avirulent for turkeys. Sixteen days after turkeys were vaccinated with each mutant, both the vaccinates and unvaccinated controls were challenge-exposed to virulent P. multocida of the homologous serotype and the heterologous serotype 3. Two of the small-colony mutant strains protected against both homologous and heterologous challenge. Suggested for a live cholera vaccine is P. multocida M3G, a small-colony-forming mutant, innocuous for both mice and turkeys and stable against reversion.     

Fowl cholera: protection against Pasteurella multocida by ribosome-lipopolysaccharide vaccine

Ribosomal protein from Aspergillus fumigatus substituted for intact ribosomes in potentiating the immunogenicity of Pasteurella multocida lipopolysaccharide. Ribosomal protein behaved as a carrier for the lipopolysaccharide. The basic protein methylated albumin, but not protamine sulfate, substituted for ribosomal protein as a carrier for lipopolysaccharide. Synthetic single- and double-stranded polynucleotides did not function as an adjuvant to potentiate the immunogenicity of lipopolysaccharide or methylated albumin-lipopolysaccharide complexes. Double-stranded polynucleotide (poly A:poly U), added as an adjuvant for methylated albumin-lipopolysaccharide vaccine, produced sera with lowered passive hemagglutination antibodies to lipopolysaccharide, but it did not influence protection against challenge with P. multocida. No differences in protection were observed between different lines of specific-pathogen-free white leghorn chickens given ribosome-lipopolysaccharide vaccine. Humoral protection, demonstrated by passive-protection tests, was induced by ribosome-lipopolysaccharide vaccine. Cell-mediated immunity was not detected by delayed-type hypersensitivity skin test reactions.     

Reduction in mortality from heartwater in cattle, sheep and goats exposed to field challenge using an inactivated vaccine

Inactivated vaccines for heartwater prepared with the commercially acceptable Montanide ISA 50 (ISA 50) adjuvant were field tested in Boer goats in Botswana, Angora goats in South Africa, and Merino sheep in Zambia and Zimbabwe. Two vaccines, one made using the Zimbabwean Mbizi isolate and the other using the respective local field isolate (Sunnyside in Botswana; Bathurst in South Africa; Lutale in Zambia), were tested at each site, except in Zimbabwe where only the Mbizi vaccine was tested. Compared with unvaccinated animals, the Mbizi vaccine significantly protected goats and sheep against field Amblyomma tick challenge in Botswana, Zambia and Zimbabwe (P = 0.018, 0.002 and 0.017, respectively), but failed to protect Angora goats in South Africa. However, in South Africa the vaccine prepared using the local field isolate Bathurst, induced significant protection (P=0.008). The vaccines containing the local isolates at all other sites were less protective than the Mbizi vaccine. The Mbizi inactivated vaccine also significantly protected 17 of 21 cattle (P = 0.05) against heartwater challenge from field ticks in Zimbabwe. Against the same challenge only 7 of 21 unvaccinated control cattle survived.This study demonstrates that heartwater is a major constraint to upgrading livestock in endemic areas, and caused an overall mortality of 77.6% in naive sheep and goats (97 of 125 died) and 67% in cattle (14 of 21 died). In contrast, the vaccine had a protective effect by reducing the overall mortality in sheep and goats to 54.3% (113 of 208 died) and to 19% in cattle (4 of 21 died).     

Oral vaccination of chickens against Newcastle disease with V4 vaccine delivered on processed rice grains

An international effort (sponsored by the Australian Centre for International Agricultural Research) is being made to develop oral vaccines that will protect village chickens against Newcastle disease. The vaccines being used are derivatives of the avirulent Australian V4 strain that have been selected for enhanced heat resistance. The present study, undertaken in Sri Lanka, used local processed (parboiled) rice as a vehicle for the vaccine. Chickens receiving two doses of vaccine on cooked, parboiled rice were completely protected against contact challenge with the virulent SL 88/1 Sri Lankan strain of Newcastle disease virus Chickens kept in contact with these vaccinated chickens were similarly protected. Lower levels of protection were achieved with vaccine given on uncooked parboiled rice. V4 vaccine administered intranasally also gave complete protection. Serums from vaccinated chickens that survived challenge were tested for haemagglutination-inhibition antibodies, using both vaccine virus and challenge virus as antigens. Titres were higher against vaccine virus.     

鸡马立克氏病三价活疫苗剂量配比和免疫剂量的研究

用马立克氏病病毒BJMDV-1株分别攻击由CVI988/B5、HCV2/B5和FC126/B5毒株组成的,剂量配比不相同的马立克氏病(MD)三价活疫苗免疫的鸡群,结果表明MD三价活疫苗中CVI988/B5、HCV2/B5及FC126/B5毒株的合适配比为2:1:2。按照此剂量配比制备的MD三价活疫苗,用RB1B超强毒株进行攻毒,当RB1B攻毒对照组MD阳性率为85.71%时,MD三价活疫苗的半数保护剂量(PD50)均数为111PFU/只,95%置信区间为585～53PFU/只的范围内,并确定MD三价活疫苗的免疫剂量为2500PFU/只。用该剂量对鸡进行MD三价活疫苗免疫,可使鸡体产生抗RB1B超强毒株攻击的坚强免疫力。     

Relationship between anti-Pasteurella multocida antibody titers after CU vaccination and survival after challenge

The relationship between serum anti-Pasteurella multocida antibodies and survival rates after challenge was determined in turkeys vaccinated one or more times with the live avirulent Clemson University (CU) vaccine and then challenged with a virulent isolate (9481) of P. multocida in the drinking water. A microtiter agglutination test for assaying anti-P. multocida serum antibodies demonstrated a highly significant (P less than 0.001) correlation between the serum antibody titer 1 week after the initial or single vaccination and the survival rate after challenge, and a significant (P less than 0.01) correlation between the antibody titer immediately before challenge and the survival rate after challenge. A highly significant (P less than 0.0001) correlation was also observed between the antibody titer before vaccination and the survival rate after challenge. This relationship was considered the result of an anamnestic response by the CU vaccine to a previous sensitization by antigens of other microbial organisms, probably in the intestine and similar antigenically to P. multocida. In contrast, a significant (P less than 0.05) but negative correlation was seen between the antibody titer 1 week after challenge and the survival rate. This relationship was thought to be the result of a marked stimulation of the antibody titer by the systemic infection of P. multocida that subsequently killed the turkeys.