The serological responses of chickens to mass vaccination with a live V4 Newcastle disease virus vaccine in the field and in the laboratory 2. Layer pullets

Layer chickens on a commercial started pullet farm were vaccinated once at 31 to 52 days of age by drinking water or aerosol with live V4 Newcastle disease virus (NDV) vaccine. Flockmates which had been rehoused in laboratory isolation pens shortly beforehand were similarly vaccinated. Samples of birds were bled at intervals and the serums tested for haemagglutination inhibiting antibody to NDV. Log2 mean titres of up to 4.88 and assumed protection levels (based on the percentage of birds with log2 titres of 4 or greater) of up to 81%, were obtained in the field trials within 4 weeks of vaccination. A subsequent laboratory trial further compared the response of different breeds of chicken to different routes of vaccination. Differences were observed between breeds, routes of vaccination, and parallel field and laboratory trials. The results show that this V4 vaccine can produce an adequate serological response following mass vaccination of Australian layer pullets housed under commercial conditions, and that care should be exercised in extrapolating results obtained under laboratory conditions.     

The resistance of meat chickens vaccinated by aerosol with a live V4 Newcastle disease virus vaccine in the field to challenge with a velogenic Newcastle disease virus

Meat chickens housed on a commercial broiler farm in Australia were vaccinated once at 10 to 11 days-of-age by aerosol with live V4 Newcastle disease virus (NDV) vaccine. Groups of vaccinated and unvaccinated birds were flown to Malaysia, where they were challenged with a virulent strain of NDV. Survival rates in vaccinated chickens challenged 7, 14, 21 or 31 d after vaccination were 0.47, 0.77, 0.97 and 0.92, respectively. All unvaccinated chickens died due to Newcastle disease (ND) following challenge. Chickens in Australia and Malaysia were bled and the serums tested for haemagglutination-inhibiting (HI) antibody to NDV. Many vaccinated birds with no detectable antibody, and all birds with a log2 titre of 2 or greater, survived challenge. The results showed that this V4 vaccine induced protective immunity in a significant proportion of chickens within 7 d of mass aerosol vaccination. This early immunity occurred in the absence of detectable circulating HI antibody. Non-HI antibody mediated immunity continued to provide protection up to 31 d after vaccination. Almost all vaccinated birds were protected within 3 w of vaccination. It is concluded that the V4 vaccine is efficacious and could be useful during an outbreak of virulent ND in Australia.     

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.     

Natural infection of broiler breeder chickens with endemic apathogenic Newcastle disease virus and their subsequent response to vaccination with a live V4 Newcastle disease virus vaccine

Flocks of broiler breeder chickens housed on a commercial farm were monitored from 13 w of age for natural infection with endemic lentogenic Newcastle disease virus (NDV). Seroconversion was first detected at 17 w. By 24 w, all 8 flocks had achieved peak log2 mean haemagglutination inhibiting antibody titres of up to 4.8. Antibody titres then declined and rose again over several months, suggesting cyclic reinfection with NDV. A lentogenic NDV indistinguishable from V4 was isolated from the cloaca of one bird at 18 weeks of age. At 54 weeks of age, 6 of 8 flocks were vaccinated en masse with live V4 NDV vaccine, 3 flocks by drinking water and 3 flocks by aerosol. All flocks were serologically monitored for a further 8 w. Drinking water vaccination induced an anamnestic response in 3 flocks, showing that flocks with pre-existing active immunity to NDV may be successfully vaccinated with V4. However, in all aerosol vaccinated flocks, the procedures failed to induce a response different to that observed in unvaccinated flocks. The serological response to vaccination was greater in sires than in dams.     

Protective antibody response produced by the chickens vaccinated with green coloured thermostable Newcastle disease virus

The efficacy of green-coloured (GC) I-2 Newcastle disease vaccine was determined in the present study. I-2 vaccine was mixed with a green coloured dye and stored at 4°C for 6 months while assayed for the virus infectivity at a monthly interval. Chickens were vaccinated with the GC vaccine by eye drop. Serum samples were collected from all birds before and after vaccination at weekly interval for 4 weeks and tested for haemagglutination-inhibition (HI) antibody against Newcastle disease virus (NDV). These chickens were challenged with NDV virulent strain four weeks after vaccination. The results showed that there was no difference between the infectivity titres of GC and uncoloured vaccines. However, chickens vaccinated with GC vaccine produced higher HI antibody titres than chickens vaccinated with uncoloured vaccine. Results from the challenge trial showed that all vaccinated chickens survived whereas all unvaccinated chickens died. The findings from this study have shown that the GC vaccine is safe and produced protective antibodies against NDV in vaccinated chickens. Wambura, P. N., 2008. Protective antibody response produced by the chickens vaccinated with green coloured thermostable Newcastle disease virus. Tropical Animal Health and Production.     

Serological response of chickens to oral vaccination with Newcastle disease virus

Conventional Newcastle disease vaccines are not suitable for application to village chickens in tropical countries of Asia. Trials with food-based vaccines are being initiated and the following experiments were performed to evaluate oral vaccination with Newcastle disease virus. Experimental chickens were vaccinated orally with the avirulent V4 strain of Newcastle disease virus and haemagglutination-inhibition antibody responses were measured. V4 virus was introduced into the crop by tube and total faecal output was collected daily and assayed for Newcastle disease virus. Virus was recovered on Days 5 and 6 after vaccination from most chickens that had received 10(7.4) and 10(6.4) 50% egg-infectious doses (EID50) of virus. There was no recovery of virus from birds receiving a lower dose of vaccine. Groups of chickens kept in cages with wire floors were given various doses of vaccine into the crop. Higher antibody titres were achieved with higher doses of virus. This dose responsiveness was not observed when various doses of vaccine were presented on food pellets and the groups of chickens were kept on concrete floors. Similar antibody responses were then seen with nominal doses of 10(5.2) and 10(8.2) EID50 per bird, possibly as a result of excretion and re-ingestion of the vaccine virus. Spread of the vaccine virus was demonstrated when control chickens and chickens receiving 10(7.7) EID50 of V4 virus on food pellets were housed together on a concrete floor. Similar antibody titres were achieved in both vaccinated and in-contact chickens.     

Bilateral effects of vaccination against infectious bursal disease and Newcastle disease in specific-pathogen-free layers and commercial broiler chickens

Different infectious bursal disease virus (IBDV) live vaccines (intermediate, intermediate plus) were compared for their immunosuppressive abilities in specific-pathogen-free (SPF) layer-type chickens or commercial broilers. The Newcastle disease virus (NDV) vaccination model was applied to determine not only IBDV-induced immunosuppression but also bilateral effects between IBDV and NDV. None of the IBDV vaccines abrogated NDV vaccine-induced protection. All NDV-vaccinated SPF layers and broilers were protected against NDV challenge independent of circulating NDV antibody levels. Sustained suppression of NDV antibody development was observed in SPF layers, which had received the intermediate plus IBDV vaccine. We observed a temporary suppression of NDV antibody development in broilers vaccinated with one of the intermediate, as well as the intermediate plus, IBDV vaccines. Different genetic backgrounds, ages, and residual maternal antibodies might have influenced the pathogenesis of IBDV in the different types of chickens. Temporary suppression of NDV antibody response in broilers was only seen if the NDV vaccine was administered before and not, as it was speculated previously, at the time the peak of IBDV-induced bursa lesions was detected. For the first time, we have demonstrated that the NDV vaccine had an interfering effect with the pathogenesis of the intermediate as well as the intermediate plus IBDV vaccine. NDV vaccination enhanced the incidence of IBDV bursa lesions and IBDV antibody development. This observation indicates that this bilateral effect of an IBDV and NDV vaccination should be considered in the field and could have consequences for the performance of broiler flocks.     

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.     

基于新城疫病毒V蛋白鉴别鸡群感染与免疫的间接ELISA方法的建立

本研究以新城疫病毒(NDV)V蛋白羧基端结构域(Vc)的重组蛋白为包被抗原,建立了用于检测NDV V蛋白抗体的间接ELISA方法,并采用该方法检测了鸡群免疫或接毒后血清中的V蛋白抗体水平。结果显示:两组不同NDV灭活疫苗组在免疫后的3周内检测结果均为阴性;两组灭活疫苗免疫3周后再人工感染NDV强毒的鸡群,攻毒后第7、14和21 d,NDV阳性率分别为60%、80%、70%和50%、80%、70%;两组不同的NDV弱毒疫苗免疫组鸡群,仅在免疫后第21 d阳性率分别为20%和10%。以上结果表明,NDV疫苗免疫组与强毒感染组的V蛋白抗体阳性率存在明显差异,本方法可在群体水平上区分新城疫疫苗免疫与强毒感染鸡群,为NDV血清学诊断和流行病学调查提供了一种新的检测手段。     

Development of a virosome vaccine for Newcastle disease virus

In an effort to protect chickens against Newcastle disease (ND), a nonreplicating virosome vaccine was produced by solubilization of Newcastle disease virus (NDV) with Triton X-100 followed by detergent removal with SM2 Bio-Beads. Biochemical analysis indicated that the NDV virosomes had similar characteristics as the parent virus and contained both the fusion and hemagglutinin-neuraminidase proteins. To target the respiratory tract, specific-pathogen-free chickens were immunized intranasally and intratracheally with the NDV virosome vaccine. This vaccine was compared with a standard NDV (LaSota) live-virus vaccine for commercial poultry. Seroconversion (> or = four fold increase in hemagglutination inhibition [HI] antibody titers) was achieved in all birds vaccinated with the virosome vaccine. Upon lethal challenge with a velogenic NDV strain (Texas GB), all birds receiving either vaccination method were protected against death. Antibody levels against NDV, as determined by enzyme-linked immunosorbent assay and HI titer, were comparable with either vaccine and increased after virus challenge. These results demonstrate the potential of virosomes as an effective tool for ND vaccination.     

Advancement in vaccination against Newcastle disease: recombinant HVT NDV provides high clinical protection and reduces challenge virus shedding with the absence of vaccine reactions

Newcastle disease (ND) is a highly contagious disease of chickens causing significant economic losses worldwide. Due to the limitation in their efficacy, current vaccination strategies against ND need improvements. This study aimed to evaluate a new-generation ND vaccine for its efficacy in providing clinical protection and reducing virus shedding after challenge. Broiler chickens were vaccinated in ovo or subcutaneously at hatch with a turkey herpesvirus-based recombinant vaccine (rHVT) expressing a key protective antigen (F glycoprotein) of Newcastle disease virus (NDV). Groups of birds were challenged at 20, 27, and 40 days of age with a genotype V viscerotropic velogenic NDV strain. Protection was 57% and 81%, 100% and 95%, and 100% and 100% after the subsequent challenges in the in ovo and subcutaneously vaccinated chickens, respectively. Humoral immune response to vaccination could be detected from 3-4 wk of age. Challenge virus shedding was lower and gradually decreased over time in the vaccinated birds compared to the unvaccinated control chickens. In spite of the phylogenetic distance between the NDV F gene inserted into the vector vaccine and the challenge virus (genotype I and V, respectively), the rHVT NDV vaccine provided good clinical protection and significantly reduced challenge virus shedding.     

Protective immune response of chickens to oral vaccination with thermostable live Fowlpox virus vaccine (strain TPV-1) coated on oiled rice

The objective of the present study was to develop and evaluate a local vaccine (strain TPV-1) against Fowl pox (FP) in chickens. Two separate groups of chickens were vaccinated with FP vaccine through oral (coated on oiled rice) and wing web stab routes, respectively. The results showed that the haemagglutination-inhibition (HI) antibody titres in both vaccinated groups were comparable and significantly higher (P < 0.05) than the control chickens. It was further revealed that 14 days after vaccination HI GMT of ≥2 log₂ was recorded in chickens vaccinated by oral and wing web stab routes whereas 35 days after vaccination the HI antibody titres reached 5.6 log₂ and 6.3 log₂, respectively. Moreover, in both groups the birds showed 100% protection against challenge virus at 35 days after vaccination. The findings from the present study have shown that oral route is equally effective as wing web stab route for vaccination of chickens against FP. However, the oral route can be used in mass vaccination of birds thus avoid catching individual birds for vaccination. It was noteworthy that strain TPV-1 virus could be propagated by a simple allantoic cavity inoculation and harvesting of allantoic fluid where it survived exposure at 57°C for 2 hours. If the oral vaccination technique is optimized it may be used in controlling FP in scavenging and feral chickens. In conclusion, the present study has shown that FP vaccine (strain TPV-1) was safe, thermostable, immunogenic and efficacious in vaccinated chickens.     

THE SEROLOGICAL RESPONSE OF CHICKENS TO AUSTRALIAN LENTOGENIC STRAINS OF NEWCASTLE DISEASE VIRUS

SUMMARY: Australian lentogenic Newcastle disease viruses were evaluated as uninactivated vaccines in Australian chickens, the response being evaluated by the production of haemagglutination-inhibition (HI) antibodies. Two viruses, V4 and PM9, induced high levels of antibody and were readily transmissible between chickens by contact exposure. Three other viruses were poorly immunogenic and poorly transmissible. Chickens vaccinated intramuscularly with the V4 strain produced higher HI antibody titres than chickens vaccinated by the orotracheal, intranasal and intraocular routes. HI antibody titres in chickens vaccinated with the V4 strain reached peak levels 3 to 5 weeks after vaccination and waned considerably during the next 2 to 4 weeks. However, low levels of HI antibody persisted for at least 36 weeks after vaccination. Intramuscular vaccination with the V4 strain of one-day-old chicks lacking maternal antibody to Newcastle disease virus resulted in 42–70% mortality and the survivors developed very high titres of HI antibody. Similar chickens inoculated orotracheally showed signs of depression and developed high titres of HI antibody, but there were no mortalities. Chickens 1-, 2-, 3- and 4-weeks-old and lacking maternally derived HI antibody to Newcastle disease virus suffered no adverse reaction to intramuscular or orotracheal vaccination. The antibody response of the 1-week-old chickens was considerably poorer than that of the older chickens. Following orotracheal vaccination with the V4 strain, chickens with low levels of maternally derived antibody responded with low levels of HI antibody. On the other hand, in the progeny of hens hyperimmunised with the V4 strain the production of active antibody following orotracheal vaccination was delayed until the level of passive antibody had declined considerably. There was no response to intramuscular vaccination in congenitally hyperimmune chickens. The minimum HI antibody inducing dose of V4 vaccine, when measured 3 weeks after vaccination of 6-weeks-old chickens, was 10^5.6 50% egg infectious doses.     

Simulation of maternal immunity by inoculation of immune yolk preparations into the yolk sac of 1-day-old chickens.

Yolk harvested from eggs laid by hens hyperimmunized with killed Newcastle disease virus (NDV) was inoculated into the yolk sac of 1-day-old specific-pathogen-free (SPF) chickens. Serum hemagglutination-inhibition antibody titers reached maximum levels 1 to 4 days after yolk inoculation and declined at a rate similar to that reported for naturally acquired maternal antibody. Expected levels of immune interference were observed when yolk-inoculated chickens were vaccinated with a conventional oil-emulsion NDV vaccine. These results show that yolk-sac inoculation with yolk antibody is a suitable approach for producing maternally immune chickens for laboratory studies.     

Reduced serologic response to Newcastle disease virus in broiler chickens exposed to a Chinese field strain of subgroup J avian leukosis virus

In this study, a Chinese field strain of subgroup J avian leukosis virus (ALV-J), NX0101, was studied for its immunosuppressive effects in both commercial broilers and SPF white Leghorn chickens infected at 1 day of age. Our data demonstrated that NX0101 induced much more significant body and immune organ weight loss in the infected commercial broiler chickens in an earlier age than that in the SPF white Leghorn chickens. At the same time antibody responses to vaccinations of Newcastle disease virus (NDV) and infectious bursa disease virus (IBDV) in the NX0101-infected chickens were also evaluated and compared between the commercial broiler chickens and the SPF white Leghorn chickens. Compared with the control group of chickens, the hemagglutination inhibition (HI) antibody response to NDV vaccines was significantly reduced in the NX0101-infected commercial broiler chickens from as early as 20 days after vaccination. However, no significant difference in HI antibody response was seen when HI titers reached their peaks in the NX0101-inoculated and control SPF white Leghorn chickens, except it declined significantly faster in infected birds. Neither of these two types of chickens showed significant decrease of antibody response to IBDV vaccination. Herein, we conclude that this NX0101 strain of ALV-J could selectively suppress humoral immune reactions to NDV, especially in broilers. But challenge experiments were not conducted and, therefore, it cannot be known if decreased antibody levels correlated with decreased protection against NDV in this case.     

Immunosuppression and histopathological changes in the bursa of fabricius associated with infectious bursal disease vaccination in chicken

The effect of the infectious bursal disease (IBD) live virus vaccine on the immune response of chicken was evaluated by the assessment of antibody response following vaccination as well as resistance to challenge with virulent virus. Birds were vaccinated at various ages and later challenged with a heterologous vaccine (NDV) or wild-type IBD virus. The BF was examined for histological changes at regular intervals. Antibody levels to NDV were monitored.

Significantly higher mortality rates were observed in birds vaccinated with IBD vaccine than unvaccinated birds (P < 0.01) following challenge, BF from vaccinated birds showed marked lymphocyte depletion and cellular infiltration with mononuclear cells.

Intraocular NDV (NDV-i/o) vaccine given at day old largely prevented the immunodepressive effect of IBD vaccination on NDV vaccine. Groups that received IBD vaccine on day 14 but no NDV i/o suffered higher mortality (41.2%) and showed lower antibody response than those vaccinated on day 1 (0%) or controls which did not receive IBDV (11.8%).     

Protective antibody response following oral vaccination of feral pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>) with Newcastle disease vaccine (strain I-2) coated on oiled rice

The novel vaccination technique for feral pigeons was developed in the present study. Multi-age feral pigeons were vaccinated orally with Newcastle disease (ND) strain I-2 vaccine coated on oiled rice. The results showed that 14 days after vaccination 40% of pigeons seroconverted with HI GMT of ≥3 log₂ whereas 28 days after vaccination the seroconversion rate of these birds reached 100%. Moreover, all vaccinated pigeons survived the challenge of virulent Newcastle disease virus (NDV). The findings from the present study indicated that the use of ND (strain I-2) vaccine in feral pigeons is feasible and resulted into the production of protective antibody response. Thus ND I-2 vaccine may prevent the spread of NDV to other birds particularly chickens. Furthermore the use of oral vaccine in feral multi-age pigeons overcomes the difficulty of catching these birds for individual vaccination.     

Protection of the Reproductive Tract of Young Chicks by Newcastle Disease Virus-induced Haemagglutinationinhibition Antibodies

The present study was conducted to assess the haemagglutination-inhibition (HI) titres required to protect the chicken reproductive tract against direct damage caused by Newcastle disease virus (NDV). Precociously induced oviduct and uterus by oestrogen treatment of young chicks were used to assess the damage or protection against the damage by analysis of ciliostasis or histopathological lesions. Unvaccinated day-old female white leghorn chickens were used as the maternally derived antibody (MDA) group. Chickens were vaccinated with either a live lentogenic vaccine on day 14 of age or, along with it, an inactivated vaccine at day 36 of age, to generate birds with a range of primary or secondary response induced HI antibodies. Birds with different HI antibody levels were challenged with virulent NDV. It was found that a HI antibody titre of 128 and above was protective against direct damage of the reproductive tract, while the 32–64 titre range was protective when derived through secondary vaccination only.     

Cell mediated and humoral immune response of chickens to inactivated oil-emulsion infectious bronchitis vaccine

A lymphocyte transformation microassay was used to study cell mediated immunity (CMI) in chickens following primary and secondary vaccination with inactivated oil emulsion infectious bronchitis (IB) vaccine and subsequent challenge with Massachusetts-41 (M-41). Humoral immunity was monitored for comparison, using the haemagglutination inhibition (HI) microassay. Positive stimulation indices (2 to 2.7 after primary and 2 to 4.8 after secondary vaccination) were lower and HI titres were higher than those previously reported following primary and secondary vaccination with live IB vaccines. The highest HI titres appeared in birds which had received the inactivated vaccine as a secondary vaccination. Challenge of vaccinated and revaccinated birds resulted in strong HI and weak CMI secondary responses. There was no correlation between CMI and HI antibody production. Monitoring egg production and clinical signs showed that a high level of protection against challenge resulted from revaccination with an inactivated oil adjuvant vaccine.     

Attenutated live fowl cholera vaccine. III. Laboratory and field vaccination trials in turkeys and chickens

Administered via the drinking water, M-3-G, an attenuated strain of Pasteurella multocida of serotype 1, was found to immunize turkeys and chickens against fowl cholera. Immunity was tested by challenging birds intramuscularly, by palatine cleft swab, or orally after 3 vaccinations. No reactions to vaccination were noted in 390 turkeys in 12 laboratory trials, nor in 20,245 vaccinated in field trials. Chickens showed no vaccination reactions, and immunity was elicited by challenge in a laboratory trial and in face of natural outbreaks in the field, where 11,600 chickens were vaccinated. No vaccination reactions were noted, although most birds involved in the trials were carrying Mycoplasma spp. Immunity was found to last about 10 weeks after the last vaccination. The immunizing properties of M-3-G are compared with the CU strain.