Newcastle Disease In Chickens Research Articles

Newcastle Disease in Chickens of Smallholder Farmers at Krang Yov Commune S’ang District, Kandal Province

Newcastle Disease in Chickens of Smallholder Farmers at Krang Yov Commune S’ang District, Kandal Province

Comparative Serological Evaluation of The Maternal and Acquired Immunity of Newcastle Disease In chickens

Comparative Serological Evaluation of The Maternal and Acquired Immunity of Newcastle Disease In chickens

Construction of recombinant Lactococcus expressing thymosin and interferon fusion protein and its application as an immune adjuvant

BackgroundIn recent years, biosafety and green food safety standards have increased the demand for immune enhancers and adjuvants. In the present study, recombinant food-grade Lactococcus lactis (r-L. lactis-Tα1-IFN) expressing thymosin Tα1 and chicken interferon fusion protein was constructed.ResultsThe in vitro interactions with macrophages revealed a mixture of recombinant r-L. lactis-Tα1-IFN could significantly activate both macrophage J774-Dual™ NF-κB and interferon regulator (IRF) signaling pathways. In vitro interactions with chicken peripheral blood mononuclear cells (PBMCs) demonstrated that a mixture of recombinant r-L. lactis-Tα1-IFN significantly enhanced the expression levels of interferon (IFN)-γ, interleukin (IL)-10, CD80, and CD86 proteins in chicken PBMCs. Animal experiments displayed that injecting a lysis mixture of recombinant r-L. lactis-Tα1-IFN could significantly activate the proliferation of T cells and antigen-presenting cells in chicken PBMCs. Moreover, 16S analysis of intestinal microbiota demonstrated that injection of the lysis mixture of recombinant r-L. lactis-Tα1-IFN could significantly improve the structure and composition of chicken intestinal microbiota, with a significant increase in probiotic genera, such as Lactobacillus spp. Results of animal experiments using the lysis mixture of recombinant r-L. lactis-Tα1-IFN as an immune adjuvant for inactivated chicken Newcastle disease vaccine showed that the serum antibody titers of the experimental group were significantly higher than those of the vaccine control group, and the expression levels of cytokines IFN-γ and IL-2 were significantly higher than those of the vaccine control group.ConclusionThese results indicate that food-safe recombinant r-L. lactis-Tα1-IFN has potential as a vaccine immune booster and immune adjuvant. This study lays the foundation for the development of natural green novel animal immune booster or immune adjuvant.

Sequential histopathological changes of the lower respiratory and gastrointestinal tracts in chickens infected with velogenic Newcastle disease virus

Velogenic Newcastle disease is a highly contagious and fatal disease that affects domestic poultry, and is clinically manifested by haemorrhagic gastroenteritis and respiratory distress. This study investigated the sequential histopathogic changes in the lungs, proventriculus, and intestines of broiler chickens infected with velogenic Newcastle disease virus (vNDV). Fifty broiler chickens (6-weeks-old) were randomly assigned into two groups of 25 each: UC – unvaccinated with Newcastle disease (ND) vaccines and intranasallly inoculated with vNDV, UU – unvaccinated uninfected. At 4, 5 and 6 days post-infection (d.p.i) tissue samples were collected from birds in each group for histopathology. The lungs showed hyperaemia, haemorrhages, inflammatory oedema and cellular infiltrations in the secondary bronchi, parabronchi (atria, infundibular, air and blood capillaries of the exchange tissue), depletion of bronchial-asociated lymphoid tissues, loss of cilia and hyperplasia of surface epithelium of bronchi and parabronchi at 4 d.p.i. The lesions progressed to collapsed air capillaries with fibroplasia and fibrosis of the area at 6 d.p.i. Similar inflammatory changes were observed in the proventriculus, but accompanied by degeneration and attenuation of surface epithelium of proventiculus and proventricular glands at 4 d.p.i., and severe necrosis and disintegration of the proventricular glands at 6 d.p.i. The intestine showed severe inflammatory changes in the mucosa, submucosa and serosa and depletion of gut-associated lymphoid tissues at 4 d.p.i., and ulcerative enteritis at 5 d.p.i. The lumen was filled with necrotic debris at 6 d.p.i. This study reinforces the concept making pathologic animal experiments important tools for a complete characterization of strains in susceptible animals, as this information will be helpful in the accurate diagnosis of velogenic Newcastle disease in chickens.

Farmers’ awareness and perceptions on Newcastle disease in chicken: Evidence from high and low rainfall regions of Kenya

Farmers’ awareness and perceptions on Newcastle disease in chicken: Evidence from high and low rainfall regions of Kenya

Genomic and biological characterization of Pigeon Paramyxovirus Type-1 isolated from Indian pigeons: First report on the six nucleotide insertion in the non-coding region of nucleoprotein gene

Genotypic analysis of Pigeon Paramyxovirus Type-1 (PPMV-1) virus, in corroboration with pathotyping, underpins the knowledge on the occurrence of PPMV-1 mediated Newcastle disease in poultry. In the present study, two PPMV-1 isolates, namely D167 and D168, obtained from feral pigeons of India in the year 2014 were analysed for their genotypic and pathotypic characteristics. Phylogenetic analysis of Fusion (F) gene grouped D167 and D168 under sub-genotypes VI.2.2.2. and VI.2.1.1.2.2. respectively. The separate positioning of these isolates within genotype VI is corroborated with the variation in restriction enzyme sites analysed through virtual restriction mapping. Analysis of FPCS region showed that both D167 and D168 possessed 112RRQKRF117 amino-acid pattern. Intra-cerebral pathogenicity index (ICPI) of D167 and D168 was 1.57 and 1.3, and mean death time (MDT) was 48 and 70 hrs respectively, designating D168 as a mesogenic pathotype, and D167 as a velogenic pathotype. Histopathological analysis of proventriculus, intestine, lungs and spleen of chickens infected with D167 and D168 isolates through intramuscular (I/M), subcutaneous (S/C) and oculo-nasal/oral (O/N) routes of inoculation showed similar severity of tissue damage. This study shows that PPMV-1 isolates belonging to two different sub-genotypes without a common ancestor, can occur together in a particular geographical region. It also shows that PPMV-1 gains virulence in chickens, which needs to be addressed in order to avoid emergence of PPMV-1 as new velogenic variant causing Newcastle disease in chickens.

Protection against Newcastle disease in chicken after vaccination in Dong Nai province

The aims of the study were to evaluate the efficiency of protection after vaccination and to find out the circulation of Newcastle disease virus (NDV) in chicken. The overall purpose was to establish the Newcastle disease’s safety areas for chicken production in Dong Nai province. At two sampling times in 2020, we collected total 1,260 blood samples at 21 days after vaccination, which were from 125 chicken smallholdings at the first sampling, and from 42 smallholdings for the second one. The swab samples included 420 pooled samples in 7 districts of the province. The serum samples were examined NDV antibody after vaccination by using HA and HI, and the swab samples were used to determine circulation of NDV based on PCR test. The results showed the average of protective rate was 54.7%, and was seen differently between two sampling times (60.2% and 49.2%, respectively) (P < 0.05). The protective rate was highest 90.0% in Cam My district, and lowest in Dinh Quan (37.8%) at the first sampling time. However, at the second time, the protective rate was highest in Long Khanh City (81.1%), while Long Thanh district was lowest (18.9%). The protective rates were obviously different among 7 districts of the province, husbandry areas (district groups named 1, 2, 3, 4), and farm sizes (<200, 200-1,000, >1,000 chicken) at the first sampling time (P < 0.01); however, at the second time the rates displayed the same among levels of factors (P > 0.05). The PCR results indicated no presence of NDV in all swab samples. That was one of the good bases to set up the Newcastle disease’s safety areas for chicken production in Dong Nai province.

Retrospective Analysis of Newcastle Disease in Chickens in Barishal District of Bangladesh

Retrospective Analysis of Newcastle Disease in Chickens in Barishal District of Bangladesh

Epidemiology of Newcastle disease in chickens of Ethiopia: a systematic review and meta-analysis.

The objective of this systematic review was to estimate the overall pooled prevalence of Newcastle disease in chickens in Ethiopia and identify the sources of heterogeneity among and within studies. The seroprevalence of Newcastle disease was estimated using a single-group meta-analysis. Attempts were also made to identify study-level variables that could explain the heterogeneity in the apparent seroprevalence of the Newcastle disease. The findings were based on 16 published articles and 33 district-level reports and were limited to studies performed during 2005-2017. Due to the presence of heterogeneity, pooled analysis from different districts was conducted using random-effects meta-analysis. The single-group summary of Newcastle disease seroprevalence in chickens was estimated to be 21.47% (19.54-23.4%) with a 95% confidence interval. Our results indicated high inter-study variability (Cochran's Q statistic = 196.2, true variance (τ2) = 0.36, inverse variance index (I2) = 90.0%, p < 0.001). Of all variables analysed, diagnostic techniques and regions were the most significant predictors (p ˂ 0.05) of heterogeneity. According to the diagnostic technique-based meta-analysis of random pooled prevalence, the haemagglutination inhibition test had the highest prevalence, followed by the enzyme-linked immunosorbent assay. In conclusion, the high-pooled prevalence estimates of the disease, combined with the scarcity of published data for the entire country of Ethiopia, indicate a significant data gap on the distribution of Newcastle disease in the country. While the high pooled prevalence tells the need for intervention to control the disease, there is also a need to assess the disease prevalence in all other parts of the country.

Vaccination indices and concomitant serological status of Newcastle disease in chickens in Aba and Umuahia of Abia State

The vaccination indices of Newcastle disease (ND) in chickens in Aba and Umuahia towns of Abia state were studied alongside their corresponding antibody status. A total of 296 sera samples were collected from 74 chicken farms. A Haemagglution inhibition (HI) test was conducted to determine the ND virus serum antibody levels. Open and closed-ended questionnaires were administered to staff on the farms selected randomly in the study areas. Information on vaccine types, origin, administering personnel, revaccination interval, and records of ND outbreaks was collected. Whereas 68.9% of the farm carried out vaccination on their own, 27.0% and 4.1% of the vaccination were done by veterinarians and animal health scientists Farms in Aba and Umuahia had average geometric mean titres (GMT) of 166.32 and 100.33, respectively. Approximately 87% of the farms had protective immunity (GMT &gt;8 or log23) against ND. Chickens aged 1-3, 4-8, 9-16, 17 weeks and above had average GMTs of 64.00, 76.99, 283.7 and 197, respectively. Post-vaccination antibody titres were 128.92, 110.63, 52.07 and 43.65, after 1 week, 2-3 weeks, 4 weeks, and above 4 weeks, respectively. Indigenous ND vaccines had an average GMT of 182.55, while foreign ND vaccines had a GMT of 120.82. The Result showed that 77% of farmers used foreign vaccines whereas 23% used indigenous vaccines. On vaccination interval, 40.5% revaccinated for ND every three weeks, 21.6% monthly, 8.1% bi-monthly and 29.7% revaccinated when necessary. About 54% of farmers reported previous ND occurrence. This study identified high seroprevalence of ND antibodies in the flock studied and indicated a high level of awareness and adherence to NDV vaccination among the farmers in the study area. The local vaccines elicited better immunogenic responses than their foreign counterparts. We, therefore, recommend that usage of the local vaccines be adopted, and revaccination is done before a month interval.

Using Outcome Mapping to Mobilize Critical Stakeholders for a Gender Responsive Rift Valley Fever and Newcastle Disease Vaccine Value Chain in Rwanda.

Approximately 752 million of the world's poor keep livestock to produce food, generate income, and build assets. Women represent two-thirds (~400 million people) of low-income livestock keepers. Infectious diseases are a major issue in preventing livestock keepers from optimizing production earnings and improving food security. In Rwanda, highly contagious yet preventable diseases that affect animals that women manage, such as Rift Valley fever in goats and Newcastle disease in chickens have a high-mortality rate and can devastate their herds. Women are disproportionately affected because they bear primary responsibility for goats and chickens. These diseases are preventable through vaccination, but smallholder women farmers rarely benefit from livestock vaccines. Social norms and entrenched cultural stereotypes limit women's confidence and decision-making and restrict their access to resources and information. Women smallholder farmers find that there is little support for the small livestock they manage, because of the official preference given to cattle. They are also challenged by limited availability of livestock vaccines due to lack of a cold chain, inadequate extension, and veterinary services, especially for goats and chickens, and unreliable structures for vaccine delivery. To identify opportunities for women's engagement in the livestock vaccine value chain (LVVC) and reduce their barriers to accessing and using livestock vaccines, we used Outcome Mapping, a stakeholder engagement tool, and the Gender Equality Continuum Tool to classify and engage critical partners in the LVVC. We analyzed each critical partner's capacities, incentives, and drivers for engagement with women, challenges and barriers that hinder their support for women farmers, opportunities at systemic and programmatic levels for women's participation and benefit in the LVVC, and the gender capacities and perceptions of different stakeholders. Enhanced positioning and visibility of women in the LVVC can occur through a systemic engagement of all stakeholders, and recognition of the roles that women play. Women smallholder farmer involvement when determining and shaping the potential entry-points is critical to ensure support for their existing responsibilities in family food security, and future opportunities for generating income. Strengthening gender capacities of LVVC stakeholders, addressing identified barriers, and building on existing opportunities can increase women's participation in the LVVC.

Construction and immune efficacy of a recombinant turkey herpesvirus vaccine strain expressing fusion protein of genotype VII Newcastle disease virus

Herpesvirus of turkeys (HVT), a commonly used live vaccine against Marek’s disease, has proven to be a highly effective viral vector for the generation of recombinant vaccines that deliver protective antigens of other avian pathogens. In this study, a vaccine designated rHVT-NDV-opti F was constructed by inserting a codon-optimized genotype Ⅶ Newcastle disease virus (NDV) fusion (F) gene into the US2 gene of HVT Fc126 vaccine strain using CRISPR/Cas9 gene-editing technology coupled with two single-guide RNAs (sgRNA). The F protein expression of rHVT-NDV-opti F was detectable by western blotting and an indirect immunofluorescence assay. Compared with wildtype HVT, rHVT-NDV-opti F has similar plaque morphology but lower in vitro replication capacity. The F protein of rHVT-NDV-opti F is genetically stable and predominantly expressed in the cell plasma. Immunization of one-day-old specific pathogen-free chickens with 4000 plaque-forming units of rHVT-NDV-opti F induced NDV-specific antibodies and provided 70% protection against a homologous NDV challenge, effectively reducing virus shedding, clinical signs, tissue viral load, and mortality. These results suggest that rHVT-NDV-opti F could be a potential vaccine candidate against Newcastle disease in chickens and that HDR-CRISPR/Cas9 combined with dual sgRNA can rapidly and efficiently construct HVT-vectored vaccine candidates.

Antiviral effect of herbal mixture (garlic, nilavembu, turmeric, coriander, and fenugreek) against Newcastle disease virus in ovo

An experimental trial was undertaken to explore the effect of herbal mixture consisiting of Curcuma longa, Coriander sativum, Allium sativum, Andrographis paniculata, and Trigonella foenum graceum by an in ovo assay and the results demonstrated that the ethanolic extracts significantly reduced the virus titres (P < 0.05) with no detectable level of virus being observed in the plant extract treated groups. Phytochemical analysis of the extract revealed the presence of alkaloids, flavonoids, saponins, tannins, terpenoids, hydrolysable tannin and glycosides which has been considered as novel antiviral agents and can be considered as a viable means to control the economically important Newcastle disease of poultry. These herbs can thus be recommended for its antiviral property and can very well be used as a substitute over the conventionally used antibiotics owing to its synergistic effect to control secondary bacterial infections. Thus the problems of drug resistance and drug residues in poultry meat arising out of usage of synthetic drugs can be minimized and thereby assuring safety and quality. However, in vivo trials are needed to validate the use of this herbal mixture in controlling New castle disease in chickens.

In situ cytokine gene expression in early stage of virulent Newcastle disease in chickens.

Selected lymphoid and reproductive tissues were examined from groups of 3-week-old chickens and 62-week-old hens that were inoculated choanally and conjunctivally with 106 EID50 of a virulent Newcastle disease virus (NDV) isolate from the California 2018-2020 outbreak, and euthanized at 1, 2, and 3 days postinfection. In the 3-week-old chickens, immunohistochemistry for NDV and for T and B cell lymphocytes, as well as in situ hybridization for IL-1β, IL-6, IFN-γ, and TNF-α revealed extensive expression of IL-1β and IL-6 in lymphoid tissues, often coinciding with NDV antigen. IFN-γ was only expressed infrequently in the same lymphoid tissues, and TNF-α was rarely expressed. T-cell populations initially expanded but by day 3 their numbers were below control levels. B cells underwent a similar expansion but remained elevated in some tissues, notably spleen, cecal tonsils, and cloacal bursa. Cytokine expression in the 62-week-old hens was overall lower than in the 3-week-old birds, and there was more prolonged infiltration of both T and B cells in the older birds. The strong pro-inflammatory cytokine response in young chickens is proposed as the reason for more severe disease.

Mulberry leaf polysaccharide supplementation contributes to enhancing the respiratory mucosal barrier immune response in Newcastle disease virus–vaccinated chicks

Despite high global vaccination coverage, Newcastle disease (ND) remains a constant threat to poultry producers owing to low antibody levels. Given the respiratory mucosa is the important site for Newcastle disease virus (NDV) vaccination, enhancing respiratory mucosal immunity may help control ND. Our previous study showed that mulberry leaf polysaccharide (MLP) is very promising in delivering a robust balanced immune response, but the effects of it on respiratory immunity in chicks are unknown. In this study, we evaluated the potential of MLP to activate respiratory mucosal immunity and revealed the possible mechanism of MLP as an immunopotentiator for ND vaccines. Chicks were randomly divided into 5 groups: blank control, vaccination control (VC), and low-, middle-, and high-dose MLP (MLP-L, MLP-M, and MLP-H) (n = 30). The serum results of humoral and cell-mediated immune responses showed significant increases in NDV hemagglutination inhibition antibody titer, IgG and IgA antibody levels, and the T-lymphocyte population in the MLP-M group compared with the VC group. Validation of results also indicated remarkable increases in tracheal antibody-mediated immunity and a mucosal immune response in the MLP-M group. Furthermore, the upregulation of TLR7 revealed a possible mechanism. Our findings provided evidence to consider MLP as a potential mucosal vaccine adjuvant candidate against ND in chickens.

Comparative Study of Protection against Newcastle Disease in Young Broilers Administered Natural Chicken Alpha Interferon via Oral and Intramuscular Routes

Despite extensive vaccination approaches, Newcastle disease (ND) remains a permanent threat to the poultry industry worldwide. Besides vaccination, there is a burgeoning demand for new antivirals for use in interventions to control ND. One strategy is to strengthen the host innate immunity via host-derived innate immune proteins. Type I interferons define one of the first lines of innate immune defense against viral infections. Chicken interferon alpha (chIFN-α) is one of the potent cytokines that trigger antiviral responses. In the current study, we investigated the therapeutic effect of natural chIFN-α administered via oral and intramuscular (i.m.) routes against ND in broiler chickens. Our results showed that the level of protection against ND in response to chIFN-α therapy was dependent on the route and dose of IFN administration. A better therapeutic effect was observed in chickens treated with chIFN-α via the oral route than in those treated via the i.m. route. Regardless of the administration route, double-dose chIFN-α (2,000-U) treatments provided better protection than single-dose (1,000-U) treatments. However, complete protection against ND was achieved in birds treated with repeated doses of chIFN-α via the oral route. Histopathology of trachea, proventriculus, spleen, and liver showed a significant improvement in ND-induced degenerative changes in double-dose IFN-treatment groups compared to single-dose groups. Results of the hemagglutination test demonstrated a decrease in ND virus (NDV) titer in IFN-treated groups. Also, double doses of chIFN-α via oral route resulted in early recovery in weight gain. We propose that chIFN-α therapy via oral route could be an important therapeutic tool to control NDV infection in chicken.IMPORTANCE Newcastle disease (ND) is an economically important contagious disease of wild and domestic birds worldwide. The disease causes severe economic losses in terms of production due to high mortality and morbidity in nonvaccinated chickens. Despite extensive vaccination approaches, Newcastle disease (ND) remains a permanent threat to the poultry industry worldwide. In the current study, we used natural chicken IFN-α as an innate immune modulator to counteract ND in chickens. We report that chIFN-α is effective in protecting the chickens against ND and also prevents shedding of the virus, which can then prevent further spread of the disease. We propose that in addition to vaccination, chIFN-α therapy could be an effective option for controlling ND in areas of endemicity.

Experimental pigeon paramyxovirus-1 infection in chicken: evaluation of infectivity, clinical and pathological manifestations and diagnostic methods.

Several pigeon paramyxovirus-1 (PPMV-1) outbreaks in feral pigeons were described recently in Switzerland. The potential of PPMV-1 to induce the notifiable Newcastle disease in chickens is discussed controversially. Therefore, in order to study epidemiologically relevant parameters such as the kinetics of PPMV-1 replication and shedding as well as seroconversion after infection, chickens were infected experimentally with a Swiss PPMV-1 isolate. This generated also defined sample material for the comparison of diagnostic tests. The infectivity of the Swiss PPMV-1 isolate for chickens was demonstrated successfully by virus shedding after experimental inoculation. Our data suggest that long-lasting shedding for up to 60 days can occur in chickens infected with PPMV-1. The isolate used here was of low pathogenicity for chickens. Different quantitative reverse transcription PCR assays were evaluated with a set of Swiss PPMV-1 isolates, and various samples from experimentally infected chickens were analysed with respect to their suitability for viral RNA detection. At 14 days post-infection, virus genome was detected mainly in spleen, caecal tonsils, heart, cloacal swabs, liver, proventriculus, duodenum and kidney tissue samples. Overall, the level of virus replication was low. Not all assays used routinely in diagnostics were capable of detecting viral genome from the isolates tested. Possible explanations are the genetic divergence of PPMV-1 and the low level of viral RNA in the samples. In contrast, two methods that are not used routinely proved more suitable for virus-genome detection. Importantly, the collection of material from various different organs is recommended, in addition to the kidney and brain analysed routinely. In conclusion, this study shows that there is a need to reconsider the type of samples and the protocols used for the detection of PPMV-1 RNA in chickens.

Ethnobotanical knowledge and threat factors for Aloe species in Tanzania

Background : The genus Aloe has long been known for its use in healthcare and cosmetics. In Tanzania, overexploitation is threatening some Aloe species with extinction and yet, little has been documented on the abundance and biocultural uses. Material and Methods: Semi-structured questionnaires were used to obtain ethnobotanical information from 236 respondents across 22 villages in four regions of Tanzania (Kilimanjaro, Tanga, Mara, Katavi-Rukwa). Results: A total of 23 Aloe species were identified, 20 of which were being used locally and were mostly being collected from the wild. We report the uses of A. mzimbana , A. volkensii subsp. volkensii, A. leptosiphon , A. parvidens and A. bicomitum for the first time in East Africa. The most preferred species were A. lateritia, A. duckeri and A. secundiflora which are three common, widely distributed species. Diseases frequently treated with Aloe species include malaria and general stomachache in humans, and Newcastle disease in chickens. Some Aloe species were found to have gone extinct locally due to over-harvesting. Rare Aloe species were perceived to be less preferred as they mostly occurred far away from settlements. Conclusions: We conclude that the genus Aloe is widely used across Tanzania and needs strong conservation measures to prevent individual species from becoming extinct in the wild. Keywords: Distribution; Ethnobotany; Folk taxonomy; Perception; Sustainable harvesting.

A Recombinant Turkey Herpesvirus Expressing F and HN Genes of Avian Avulavirus-1 (AAvV-1) Genotype VI Confers Cross-Protection against Challenge with Virulent AAvV-1 Genotypes IV and VII in Chickens.

Newcastle disease (ND) is responsible for significant economic losses in the poultry industry. The disease is caused by virulent strains of Avian avulavirus 1 (AAvV-1), a species within the family Paramyxoviridae. We developed a recombinant construct based on the herpesvirus of turkeys (HVT) as a vector expressing two genes: F and HN (HVT-NDV-F-HN) derived from the AAvV-1 genotype VI (“pigeon variant” of AAvV-1). This recombinant viral vaccine candidate was used to subcutaneously immunize one group of specific pathogen-free (SPF) chickens and two groups of broiler chickens (20 one-day-old birds/group). Humoral immune response was evaluated by hemagglutination-inhibition test and enzyme-linked immunosorbent assay (ELISA). The efficacy of the immunization was assessed in two separate challenge studies performed at 6 weeks of age with the use of virulent AAvV-1 strains representing heterologous genotypes IV and VII. The developed vaccine candidate elicited complete protection in SPF chickens since none of the birds became sick or died during the 2-week observation period. In the broiler groups, 90% and 100% clinical protection were achieved after challenges with AAvV-1 of IV and VII genotypes, respectively. We found no obvious relationship between antibody levels and protection assessed in broilers in the challenge study. The developed recombinant HVT-NDV-F-HN construct containing genes from a genotype VI AAvV-1 offers promising results as a potential vaccine candidate against ND in chickens.

Recombinant Newcastle disease virus (NDV) La Sota expressing the haemagglutinin–neuraminidase protein of genotype VII NDV shows improved protection efficacy against NDV challenge

ABSTRACTIntensive vaccination strategies against Newcastle disease (ND) have been implemented in many countries for a long time, but ND outbreaks still occur frequently, with most isolates belonging to genotype VII of Newcastle disease virus (NDV). Many researchers have revealed that vaccines closely matched to epidemic viruses provide better protection. Therefore, using a previously established reverse genetics system, we generated a recombinant NDV vaccine strain (rLa Sota-HN) based on the La Sota vaccine strain expressing the haemagglutinin–neuraminidase (HN) protein of genotype VII NDV. The pathogenicity of the recombinant virus was confirmed by the mean death time in 9-day-old specific-pathogen-free embryonated chicken eggs and the intracerebral pathogenicity index in 1-day-old specific-pathogen-free chickens. Subsequently, 1-day-old chickens were immunized with commercial vaccine La Sota and recombinant virus rLa Sota-HN and then challenged with virulent genotype VII NDV strain. The results indicated that recombinant virus rLa Sota-HN provided increased protection of vaccinated chickens from morbidity and mortality, and inhibited the shedding of virulent virus after challenging with genotype VII virus, compared with the conventional vaccine La Sota. Our findings indicated that rLa Sota-HN is a promising vaccine candidate to improve the protection efficiency against ND in chickens, thereby preventing frequent outbreaks of this disease.