Evaluation of Newcastle Disease antibody titers in backyard poultry in Germany with a vaccination interval of twelve weeks

Effectiveness of a community-centered Newcastle disease vaccine delivery model under paid and free vaccination frameworks in southeastern Kenya

In the absence of effective drugs, vaccines constitute the cornerstone for the prevention of Newcastle disease (ND). Different strategies have been implemented to increase vaccination, but uptake remains low, underscoring the need for novel vaccine delivery methods. We designed and assessed the effectiveness of a community-centered ND vaccine delivery model in southeastern Kenya. Under the model, we sensitized smallholder chicken farmers (SCFs) through structured training on chicken husbandry, biosecurity, ND, and its vaccination, among other aspects. We subsequently engaged trained community vaccinators (CVs) to deliver vaccines and/or provide vaccination services to SCFs at a cost on one hand and, at no cost on the other, in selected sites to address challenges of inadequate service providers, vaccine unavailability, and inaccessibility. We tested this model under paid and free vaccination frameworks over one year and assessed the model's effect on vaccine uptake, ND-related deaths, and vaccine accessibility, among other aspects. Overall, we vaccinated more chickens at free sites compared to paid sites. However, we vaccinated a significantly higher mean number of chickens per household at paid (49.4±38.5) compared to free (28.4±25.9) sites (t = 8.4, p<0.0001). We recorded a significant increase in the proportion of SCFs who vaccinated their chickens from 31.3% to 68.4% (χ2(1, N = 399) = 58.3, p<0.0001) in paid and from 19.9% to 74.9% (χ2(1, N = 403) = 115.7, p<0.0001) in free sites pre- and post-intervention, respectively. The mean number of ND-related deaths reported per household decreased from 18.1±31.6 pre-intervention to 7.5±22.3 post-intervention (t = 5.4, p = 0.000), with higher reductions recorded in paid sites (20.9±37.7 to 4.5±11.2) compared to free sites (15.0±22.6 to 10.7±29.7) pre- and post-intervention, respectively. Farmers with access to vaccines increased significantly from 61.1% to 85.4% (χ2(1, N = 399) = 31.7, p<0.0001) in paid and 43.6% to 74.9% (χ2(1, N = 403) = 38.4, p = 0.0001) in free sites pre- and post-intervention, respectively. We established that type of intervention framework, gender of household head, if the household head attended training on chicken production in the last 12 months, access to information on ND vaccination, and the number of chickens lost to the previous ND outbreak were significant predictors of ND vaccine uptake. Our findings indicate the model has a broader reach and benefits for SCFs. However, policies should be enacted to regulate the integration of CVs into the formal animal health sector.

Newcastle viral disease causation web correlations with laying hen productivity

Environmental conditions profoundly impact the health, welfare, and productivity of laying hens in commercial poultry farming. We investigated the association between microclimate variations, production indices, and histopathological responses to accidental Newcastle disease virus (NDV) infection within a controlled closed-house system. The study was conducted over seven months in a laying hen facility in Cairo, Egypt. Microclimate measurements included temperature, relative humidity (RH%), air velocity (AV), and the temperature humidity index (THI) that were obtained from specific locations on the front and back sides of the facility. Productivity indices, including the egg production percentage (EPP), egg weight (EW), average daily feed intake, and feed conversion ratio, were assessed monthly. During an NDV outbreak, humoral immune responses, gross pathology, and histopathological changes were evaluated. The results demonstrated significant (p < 0.05) variations in EPP and EW between the front and back sides except in April and May. AV had a significant (p = 0.006) positive effect (Beta = 0.346) on EW on the front side. On the back side, AV had a significant (p = 0.001) positive effect (Beta = 0.474) on EW, while it negatively influenced (p = 0.027) EPP (Beta = - 0.281). However, temperature, RH%, and THI had no impact and could not serve as predictors for EPP or EW on either farm side. The humoral immune response to NDV was consistent across microclimates, highlighting the resilience of hens. Histopathological examination revealed characteristic NDV-associated lesions, with no significant differences between the microclimates. This study underscores the significance of optimizing microclimate conditions to enhance laying performance by providing tailored environmental management strategies based on seasonal variations, ensuring consistent airflow, particularly near cooling pads and exhaust fans, and reinforcing the importance of biosecurity measures under field challenges with continuous monitoring and adjustment.

Evaluation of the immune response of layer chickens to Newcastle disease virus vaccines using the new vaccination regimens

BACKGROUND

The study aimed to evaluate the immunological response of layer chickens to live Newcastle disease virus vaccine using a newly developed vaccine schedule administered via the ocular route, as well as assess the persistence of passive antibodies in layer chickens and the effectiveness of protection against strains of the virus.

METHODS

A total of 140-day-old Lohmann Brown chicks were randomly divided into seven groups, 20 chicks each. Groups 1-3 received a single eye instillation of the vaccine at ages 5, 26 and 54 days, respectively, whereas groups 4-6 received a double eye instillation. Group 7 served as non-vaccinated control group. Ten days after immunization, samples were taken from hens that had received the vaccine at ages 15, 36 and 64, as well as from control chickens that had not received the vaccine at ages 5, 15, 21 and 31.

RESULTS

A total of 10 serum samples from all chickens exhibited protective antibodies, and booster doses resulted in the highest haemagglutination inhibition titre. No significant change in antibody production was observed among layer hens (p > 0.05). The study found that the La Sota (GMT ± SD: 6.71 ± 4.96), La Sota (GMT ± SD: 8.00 ± 0.00) and thermostable I2 (GMT ± SD: 7.60 ± 6.02), vaccination schedules provided the maximum immune response in single eye instillation, whereas the HB1 (GMT ± SD: 7.11 ± 4.77), La Sota (GMT ± SD: 7.83 ± 5.76) and La Sota (GMT ± SD: 7.60 ± 6.02), combination was the second-best vaccination schedule in double eye instillation. Furthermore, maternally-derived antibodies were maintained up to 31 days of age, indicating the level of passive immunity prior to vaccination. Characteristic lesions, such as edematous and diphtheria mucosal membranes of the trachea, along with petechial and necrotic haemorrhages of the proventriculus, were observed during the necropsy of the birds that died from the challenged virus.

CONCLUSION

This study suggests that subsequent live virus vaccine by ocular route immunization is required to effectively protect against velogenic viscerotropic Newcastle disease infection. The results also highlight the importance of developing effective vaccination schedules and routes to enhance immunity against ND in layer chickens.

Response of broiler breeder pullets when fed hydrolyzed whole yeast from placement to 22 wk of age

The study examined the effects of feeding broiler breeder pullets hydrolyzed whole yeast (HY) from hatch to 22 wk of age (WOA). A total of 524-day-old Ross 708 pullets were placed in floor pens (∼24 birds/pen) for the starter (0-4 WOA) and grower (5-18 WOA) phases, then transferred to the egg production facility and redistributed to ∼20 birds/pen for the prelay phase (19-22 WOA). Two diets were allocated to pens (0-18 WOA; n = 11) and (19-22 WOA; n-12). The diets were a control corn and soybean meal diet formulated to meet specifications and control plus 0.05% HY (HY). Birds had ad libitum access to feed in the first week and daily feed allocation based on pen BW from 2 WOA. Birds had free access to water throughout the trial. Body weight (BW) and uniformity (BW CV) were monitored. Boosters for infectious bronchitis and New Castle disease vaccines were administered at 18 WOA, and samples of pullets bled for antibody titer 5-day later. One pullet/pen was randomly selected, weighed, bled for plasma biochemistry, and necropsied for organ weights, ceca digesta for short-chain fatty acids (SCFA), and leg bones morphometry. In the starter and grower phases, birds fed HY were lighter and gained less (P < 0.05) than control birds. However, there were no diet effects (P > 0.05) on growth, the BW prelay phase, or BW uniformity throughout the trial. There were no (P > 0.05) diet effects on breast, gastrointestinal, liver and bursa weights, serum antibody titers, plasma biochemistry, SCFA and bone attributes. However, pullets fed HY had heavier (P = 0.047) spleen and tended to have lower (P = 0.080) plasma concentrations of aspartate aminotransferase (AST) relative to control pullets. In conclusion, the parameters assessed showed no negative consequences of feeding HY to broiler breeder pullets. However, effects on the spleen and plasma AST may indicate modest modulation of immunity and metabolism. The impact of the provision of HY during broiler breeder pullet phase on reproductive performance and chick quality should be investigated.

Prophylactic influences of prebiotics on gut microbiome and immune response of heat-stressed broiler chickens

Climatic changes and elevated ambient temperature are significant environmental stressors with a negative impact on birds' physiological, immunological, and behavioral status, increasing their susceptibility to stressors and immunosuppression and consequently increasing intestinal permeability (leaky gut). Prebiotics have been utilized to stop or diminish the harmful effects of stress in chickens. We aimed to evaluate the role of mannan-oligosaccharides, and beta-D-glucan prebiotics supplements in drinking water against experimentally induced heat stress (HS) on broiler chickens and study their impact on birds' performance, gut microbiome, and immune response. A total of 120 1-day-old Ross broiler chicks were allocated into four groups (30 birds/group), and each group was subdivided into triplicates (10 birds each). The experimental groups were classified as follows; the 1st (G1) control birds, the 2nd (G2) birds exposed experimentally to HS, the 3rd (G3) birds administered prebiotics in drinking water without exposure to HS, and the 4th (G4) birds exposed to HS and administered prebiotics in drinking water. After each vaccination, blood samples and serum samples were collected to evaluate the birds' immune status. Fecal samples were also collected for the molecular evaluation of the gut microbiome based on the genetic analyses and sequencing of 16S rRNA gene. The results showed that HS has reduced the birds' performance and badly affected the birds' immune response and gut microbiome. However, the addition of prebiotics to drinking water, with or without stress, enhanced the growth rate, maintained a normal gut microbiome, and improved immune parameters. Moreover, the usage of prebiotics improved the chicken gut microbiome and alleviated the negative effect of heat stress. Administering prebiotics significantly (p < 0.05) increased the relative abundance of beneficial bacteria and eradicated pathogenic ones in the birds' gut microbiome. Prebiotics showed a positive effect on the gut microbiome and the immune status of chickens under HS in addition to their efficacy as a growth promoter.

Study on Seroprevalence and Associated Risk Factors of Newcastle Disease in Smallholder Poultry Farms in Sodo Zuria District, Wolaita Zone, Southern Ethiopia

Newcastle disease (NCD) is a highly contagious viral disease of poultry and remains a constant threat in poultry farms that causes huge economic losses. The objective of this study was to estimate and assess the seroprevalence and associated risk factors of Newcastle disease in the Sodo Zuria district, southern Ethiopia. A cross-sectional survey followed by a simple random sampling technique was conducted from May to July 2021 on 384 apparently healthy nonvaccinated chickens on 30 smallholder poultry farms using commercial indirect ELISA kits and a questionnaire survey. The data were analyzed by using STATA for windows version 20 and a logistic regression reporting odds ratiowas applied to describe the seroprevalence of Newcastle disease with associated risk factors. The result of the study demonstrates that there was a high seroprevalence 48.7% (n= 187/384) of Newcastle disease in the study district. Information on associated risk factors were assessed using a semistructured questionnaire. The sex of the chicken showed a statistically significant difference (x² = 4.842; p = 0.028) with the seroprevalence of the disease. The difference in seroprevalence among intensive, semi-intensive, and extensive management system was statistically significant (x² = 3.84; p = 0.0001). There was also a statistical significant difference (x² = 2.3854; p = 0.496) in the absence and presence of safe disposal of a dead chicken with the occurence of Newcastle disease. However, no statistically significant difference was observed among age groups (x² = 4.335; p = 0.114), disinfection of poultry house (x² = 0.0; p = 0.998), presence and absence of footbath (x² = 2.969; p = 0.085), the breeds (x² = 4.490; p = 0.106), type of chicken (x² = 0.302; p = 0.583), and housing system (x² = 1.926; p = 0.588). A high seroprevalence without vaccination history showed that the virus was circulating within the poultry. Therefore, further molecular study has to be conducted to identify circulating strains and develop an evidence-based control program.

Immunogenicity of Newcastle disease virus strain ZG1999HDS applied oculonasally or by means of nebulization to day-old chicks

Newcastle disease (ND) is one of the classic viral infections of poultry which resists all the efforts of eradication. Newcastle disease virus (NDV) strain ZG1999HDS was isolated during the outbreak in 1,999 at a broiler farm in Croatia. Previous trials in chickens confirmed it to be a lentogenic pathotype and immunogenic by stimulating humoral and cell mediated immunity. Further characterization by deduced amino acid sequence at the cleavage site of fusion protein confirmed its lentogenic nature, and in vitro tests its oncolytic capacity. Owing to its immunogenicity, strain ZG1999HDS is considered for vaccine development. In this study, 1-day-old chicks were vaccinated using strain ZG1999HDS oculonasally or by nebulization. Strain ZG1999HDS induced humoral immune response in both immunized groups The cell-mediated immune response occurred earlier in the group immunized by nebulization, as shown by a higher frequency rate of T and B lymphocytes, and significantly higher expression of IFN-α in respiratory organs and IFN-γ expression in the spleen. Viral genomic RNA was not detected in investigated organs. Thus, NDV strain ZG1999HDS is immunogenic when administered by means of nebulization or oculonasally without any adverse effects and is therefore suitable for further research and vaccine development. Further research is needed regarding its tropism.