Unvaccinated Chickens Research Articles

Host response to successive challenges with lentogenic and velogenic Newcastle disease virus in local chickens of Ghana

Newcastle disease (ND) is a highly contagious viral disease that constantly threatens poultry production. The velogenic (highly virulent) form of ND inflicts the most damage and can lead to 100% mortality in unvaccinated village chicken flocks. This study sought to characterize responses of local chickens in Ghana after challenging them with lentogenic and velogenic Newcastle disease virus (NDV) strains. At 4 wk of age, chicks were challenged with lentogenic NDV. Traits measured were pre- and post-lentogenic infection growth rates (GR), viral load at 2 and 6 d post-lentogenic infection (DPI), viral clearance rate and antibody levels at 10 DPI. Subsequently, the chickens were naturally exposed to velogenic NDV (vNDV) after anti-NDV antibody titers had waned to levels ≤1:1,700. Body weights and blood samples were again collected for analysis. Finally, chickens were euthanized and lesion scores (LS) across tissues were recorded. Post-velogenic exposure GR; antibody levels at 21 and 34 days post-velogenic exposure (DPE); LS for trachea, proventriculus, intestines, and cecal tonsils; and average LS across tissues were measured. Variance components and heritabilities were estimated for all traits using univariate animal models. Mean pre- and post-lentogenic NDV infection GRs were 6.26 g/day and 7.93 g/day, respectively, but mean post-velogenic NDV exposure GR was −1.96 g/day. Mean lesion scores ranged from 0.52 (trachea) to 1.33 (intestine), with males having significantly higher (P < 0.05) lesion scores compared to females. Heritability estimates for the lentogenic NDV trial traits ranged from moderate (0.23) to high (0.55) whereas those for the vNDV natural exposure trial were very low (≤ 0.08). Therefore, in contrast to the vNDV exposure trial, differences in the traits measured in the lentogenic challenge were more affected by genetics and thus selection for these traits may be more feasible compared to those following vNDV exposure. Our results can form the basis for identifying local chickens with improved resilience in the face of NDV infection for selective breeding to improve productivity.

Prevalence of Marek’s disease virus in unvaccinated healthy backyard chickens in Cantho city, Vietnam and genetic characterization of meq gene

An investigation was carried out to survey the prevalence of Marek’s disease virus serotype 1 (MDV-1) on unvaccinated healthy backyard chicken flocks from four districts in Cantho city and to analyze the genetic characterization of the meq gene. A total of 353 feather follicle samples were collected from 50 unvaccinated chicken flocks for Marek’s disease to investigate prevalent MDV-1 by polymerase chain reaction (PCR). The four represent strains were chosen for meq gene sequencing. The results revealed that 26 out of 353 samples were positive for MDV-1 accounting for 7.37%. There were significant differences in the prevalence of MDV-1 on chickens among districts (P&lt;0.05). The Meq protein of the four strains (VT, CD, PD, and TL) contained 20.14% proline and three regions of proline repeats. Besides, all four strains occurred with amino acid point mutations. These strains had only a substitution of proline at position 217 as well as interruption of consecutive proline at site 2. Phylogenetic analysis indicated that these strains were within a group relating to virulent Italian isolates.

Targeted sequencing analysis of Mycoplasma gallisepticum isolates in chicken layer and breeder flocks in Thailand

Mycoplasma gallisepticum (MG) is one of the most economically important pathogens worldwide. MG affects the respiratory system and impairs growth performance in poultry. In developing countries, the most widely used technique to identify MG is the conventional PCR assay. In this study, 24 MG isolates collected from Thailand farms with unvaccinated chickens during 2002–2020 were characterized by gene-targeted sequencing (GTS), followed by phylogenetic analysis using unweighted pair group method with arithmetic mean. These 24 Thai MG isolates differed from vaccine strains, including the F, ts-11 and 6/85 strains. One isolate showed 99.5–100% genetic similarity to the F strain with 4 partial gene analyses. This result may have been due to contamination from vaccinated flocks because the F strain is the most commonly used vaccine strain in Thailand. However, the GTS analysis using the partial MG genes in this study showed that the isolates could be grouped into different patterns based on individual gene sequences. The phylogenetic analysis of partial mgc2, gapA, pvpA and lp gene sequences classified the Thai MG isolates into 7, 11, 7 and 2 groups, respectively. In conclusion, at least 2 partial MG genes, especially partial gapA and mgc2 genes, are needed to differentiate MG isolates.

Genetic characterization and distribution of the virus in chicken embryo tissues infected with Newcastle disease virus isolated from commercial and native chickens in Indonesia.

Background and Aim:Newcastle disease (ND) is a viral infectious disease that affects commercial and native chickens, resulting in economic losses to the poultry industry. This study aimed to examine the viral strains circulating in commercial and native chickens by genetic characterization and observe the distribution of Newcastle disease virus (NDV) in chicken embryonic tissue.Materials and Methods:ND was detected using a quantitative reverse transcription-polymerase chain reaction. Genetic characterization of the fusion (F) and hemagglutinin-neuraminidase (HN) genes from the eight NDVs was performed using specific primers. The sequence was compared with that of other NDVs from GenBank and analyzed using the MEGA-X software. The distribution of NDV in chicken embryos was analyzed based on lesions and the immunopositivity in immunohistochemistry staining.Results:Based on F gene characterization, velogenic NDV strains circulating in commercial and native chickens that showed varying clinical symptoms belonged to genotype VII.2. Lentogenic strains found in chickens without clinical symptoms were grouped into genotype II (unvaccinated native chickens) and genotype I (vaccinated commercial chickens). Amino acid variations in the HN gene, namely, the neutralization epitope and antigenic sites at positions 263 and 494, respectively, occurred in lentogenic strains. The NDV reaches the digestive and respiratory organs, but in lentogenic NDV does not cause significant damage, and hence embryo death does not occur.Conclusion:This study showed that velogenic and lentogenic NDV strains circulated in both commercial and native chickens with varying genotypes. The virus was distributed in almost all organs, especially digestive and respiratory. Organ damage in lentogenic infection is not as severe as in velogenic NDV. Further research is needed to observe the distribution of NDV with varying pathogenicity in chickens.

Characterization of vaccine-induced immune responses against coccidiosis in broiler chickens

Coccidiosis, caused by Eimeria protozoan species, is an economically important enteric disease of poultry. Although commercial live vaccines are widely used for disease control, the vaccine-induced protective immune mechanisms are poorly characterized. The present study used a commercial broiler vaccine containing a mixture of E. acervulina, E. maxima, and E. tenella. One-day-old chicks were vaccinated by spray followed by a challenge at 21 days of age with a mixture of wild type Eimeria species via oral gavage. Oocyst shedding, immune gene expression and cellular responses in the spleen and cecal tonsils were measured at pre- (days 14 and 21) and post-challenge (days 24, 28 and 35) time points. Results showed that the oocyst counts were significantly reduced in the vaccinated chickens at post-challenge compared to unvaccinated control group. While the vaccinated birds had a significantly increased toll-like receptor (TLR) 21 gene expression at pre-challenge, the transcription of interferon (IFN)γ, Interleukin (IL)-12 and CD40 genes in spleen and cecal tonsils of these birds was significantly higher at post-challenge compared to unvaccinated chickens. Cellular immunophenotyping analysis found that vaccination led to increased frequency of macrophages and activated T cells (CD8+CD44+ and CD4+CD44+) in the spleen and cecal tonsils at post-challenge. Furthermore, in vitro stimulation of chicken macrophages (MQ-NCSU cells) with purified individual species of E. acervulina, E. maxima, and E. tenella showed a significantly increased expression of TLR21, TLR2 and IFNγ genes as well as nitric oxide production. Collectively, these findings suggest that TLR21 and TLR2 may be involved in the immune cell recognition of Eimeria parasites and that the vaccine can induce a robust macrophage activation leading to a T helper-1 dominated protective response at both local and systemic lymphoid tissues.

Maternal-derived antibodies hinder the antibody response to H9N2 AIV inactivated vaccine in the field

AbstractThe H9N2 subtype avian influenza virus (AIV) inactivated vaccine has been used extensively in poultry farms, but it often fails to stimulate a sufficiently high immune response in poultry in the field, although it works well in laboratory experiments; hence, the virus still causes economic damage every year and poses a potential threat to public health. Based on surveillance data collected in the field, we found that broilers with high levels of maternal-derived antibodies (MDAs) against H9N2 virus did not produce high levels of antibodies after vaccination with a commercial H9N2 inactivated vaccine. In contrast, specific pathogen-free (SPF) chickens without MDAs responded efficiently to that vaccination. When MDAs were mimicked by administering passively transferred antibodies (PTAs) into SPF chickens in the laboratory, similar results were observed: H9N2-specific PTAs inhibited humoral immunity against the H9N2 inactivated vaccine, suggesting that H9N2-specific MDAs might hinder the generation of antibodies when H9N2 inactivated vaccine was used. After challenge with homologous H9N2 virus, the virus was detected in oropharyngeal swabs of the vaccinated and unvaccinated chickens with PTAs but not in the vaccinated chickens without PTAs, indicating that H9N2-specific MDAs were indeed one of the reasons for H9N2 inactivated vaccine failure in the field. When different titers of PTAs were used to mimic MDAs in SPF chickens, high (HI = 12 log2) and medium (HI = log 9 log2) titers of PTAs reduced the generation of H9N2-specific antibodies after the first vaccination, but a booster dose would induce a high and faster humoral immune response even of PTA interference. This study strongly suggested that high or medium titers of MDAs might explain H9N2 inactivated vaccine failure in the field.

Avian metapneumovirus subtype B vaccination in commercial broiler chicks: heterologous protection and selected host transcription responses to subtype A or B challenge

ABSTRACT Avian metapneumovirus (aMPV) causes respiratory disease and drops in egg production in chickens, and is routinely controlled by vaccination. However, the host’s immune response to virulent challenge in vaccinated or unvaccinated broiler chickens is poorly characterized. We show that subtype B vaccination offers heterologous (subtype A challenge) and homologous (subtype B challenge) protection. Subtype B challenge caused significantly greater humoral antibody titres in vaccinated and unvaccinated chickens. In turbinate and lung tissues of unvaccinated-challenged chickens, IgA and IgY mRNA transcription was significantly up-regulated after subtype B challenge compared to subtype A. Cellular immunity (CD8-α and CD8-β) gene transcripts were significantly up-regulated during early and later stages of infection from subtype B or subtype A, respectively. Immune gene transcriptional responses (IL-1β, IL-6 and IL-18) were significantly up-regulated after challenge. Gene transcription results showed that mRNA expression levels of CD8-α, CD8-β, TLR3 and IL-6, particularly in turbinate and trachea tissues, are useful parameters to include in future aMPV vaccination-challenge studies.

Hemagglutinin-neuraminidase gene of genotype VII Newcastle disease virus strains isolated in Japan.

Recently, genotype VII of Newcastle disease virus (NDV) has become the most prevalent NDV genotype in Asia. Here the hemagglutinin-neuraminidase (HN) gene of genotype VII NDV strains isolated in Japan was analyzed. Notably, point amino acid substitutions in the HN protein at position 347, which is located on the major linear epitope of the HN protein, were found in two strains. However, by a hemagglutination inhibition assay, major antigenic differences did not exist between the studied strains. Additionally, chickens vaccinated with the B1 strain did not exhibit clinical effects after challenge with variants possessing the substitution at position 347 (E to K), whereas all unvaccinated chickens subjected to this challenge died within 5 days.

Salmonella Pullorum lacking srfA is attenuated, immunogenic and protective in chickens

Sallmonella Pullorum is a host-restricted pathogen for poultry and causes severe economic importance in many developing countries. The development of novel vaccines for Salmonella Pullorum is necessary to eradicate the prevalence of the pathogen. In our study, a srfA deletion mutant (C79-13ΔsrfA) of Salmonella Pullorum was constructed, and then the biological characteristics and protective efficacy of the mutant were evaluated. The mutant C79-13ΔsrfA was much less virulent than its parental strain C79-13 in one-day-old HY-line white chickens, immunization with C79-13ΔsrfA (4 × 107 CFU) through oral pathway induced highly specific humoral and cellular immune responses, the growth performance of vaccinated chickens was consistent with that of unvaccinated chickens. The survival percentages of vaccinated chickens reached 90% and 80%, after challenge with Salmonella Pullorum strain C79-13 and Salmonella Gallinarum strain SG9 at 10 days post-immunization (dpi), respectively. Collectively, our results indicate that C79-13ΔsrfA is a live attenuated vaccine candidate.

Mucosal immune responses in the trachea after chronic infection with Mycoplasma gallisepticum in unvaccinated and vaccinated mature chickens.

Tracheitis associated with the chronic respiratory disease in chickens caused by Mycoplasma gallisepticum is marked by infiltration of leukocytes into the mucosa. Although cytokines/chemokines are known to play a key role in the recruitment, differentiation, and proliferation of leukocytes, those that are produced and secreted into the trachea during the chronic stages of infection with M. gallisepticum have not been described previously. In this study, the levels of transcription in the trachea of genes encoding a panel of 13 cytokines/chemokines were quantified after experimental infection with the M. gallisepticum wild-type strain Ap3AS in unvaccinated chickens and chickens vaccinated 40-, 48- or 57-weeks previously with the novel attenuated strain ts-304. These transcriptional levels in unvaccinated/infected and vaccinated/infected chickens were compared with those of unvaccinated/uninfected and vaccinated/uninfected chickens. Pathological changes and subsets of leukocytes infiltrating the tracheal mucosa were concurrently assessed by histopathological examination and indirect immunofluorescent staining. After infection, unvaccinated birds had a significant increase in tracheal mucosal thickness and in transcription of genes for cytokines/chemokines, including those for IFN-γ, IL-17, RANTES (CCLi4), and CXCL-14, and significant downregulation of IL-2 gene transcription. B cells, CD3+ or CD4+ cells and macrophages (KUL01+ ) accumulated in the mucosa but CD8+ cells were not detected. In vaccinated birds, the levels of transcription of the genes for IL-6, IL-2, RANTES and CXCL-14 were significantly lower after infection than in the unvaccinated/infected and/or unvaccinated/uninfected birds, while the transcription of the IFN-γ gene was significantly upregulated, and there were aggregations of B cells in the tracheal mucosa. These observations indicated that M. gallisepticum may have suppressed Th2 responses by upregulating secretion of IFN-γ and IL-17 by CD4+ cells and induced immune dysregulation characterized by depletion of CD8+ cells and downregulation of IL-2 in the tracheas of unvaccinated birds. The ts-304 vaccine appeared to induce long-term protection against this immune dysregulation. TAKE AWAY: The ts-304 vaccine-induced long-term protection against immune dysregulation caused by M. gallisepticum Detection of B cells and plasma cells in the tracheal mucosa suggested that long-term protection is mediated by mucosal B cell memory Infection of unvaccinated birds with M. gallisepticum resulted in CD8+ cell depletion and downregulation of IL-2 in the tracheal mucosa, suggestive of immune dysregulation Infection of unvaccinated birds with M. gallisepticum resulted in upregulation of IFN-γ and infiltration of CD4+ cells and antigen presenting cells (B and KUL01+ cells) into the tracheal mucosa, suggesting enhanced antigen processing and presentation during chronic infection Th2 responses to infection with M. gallisepticum may be dampened by CD4+ cells through upregulation of IFN-γ and IL-17 during chronic infection.

Pharmacological effect of synobiotic and phytobiotic in kidney function and some blood parameters of chicken

The aim of this research was to study the effects of dietary supplementation of ‎synbiotic, phytobiotics and their mixture on kidney functions, some blood parameters and histological criteria of broilers. A total of 200 ‎broiler chicks were randomly chosen and divided into eight groups (25 birds in each). The first four groups were unvaccinated chicken which received a basal diet (group 1) or ‎the same diet supplemented with 1g synobiotic /kg body weight (group 2), 1g phytobiotic /kg body weight (group 3) and 1g ‎synobiotic plus 1g phytobiotic/kg body weight (group 4). The second four groups were vaccinated chicken and fed the same previous treatments with groups 5, 6, 7 and 8, respectively. Therapeutic dose of synobiotic and phytobiotic or their mixture (1ml/ kg. body weight) orally for 3 ‎successive days ‎tended to decrease uric acid and creatinine in unvaccinated and vaccinated chicken at 7, 14 and 21 day. In this study uric acid and ‎creatinine levels resulted in decrease, showing a significant improvement of kidney functions‎ ‎. Some different parameters of blood and histological criteria showed normal measurements with no adverse effect of treatments.  Â

The immunibiochemical effect of synobiotic and phytobiotic in vaccinated and unvaccinated chicken

The current study was conducted to evaluate the effects of dietary supplementation of synbiotics, phytobiotics and their mixture on some blood parameters with respct to kidney and liver functions and some histological criteria of broilers. A total of 200 broiler chicks were randomly chosen and divided into eight groups (25 bird in each). The first four groups were unvaccinated chicken and allotted to four dietary treatments, either fed a basal diet (group 1) or the same diet supplemented with 1g synbiotic /kg body weight ( group 2) , 1g phytobiotic /kg body weight (group 3) and 1g synbiotic plus 1g phytobiotic/kg body weight (group 4) .The same previous treatments were received by four vaccinated chicken groups 5, 6,7 and 8 , respectively. Synobotic and phytobiotic tended to increase AST and ALT levels in vaccinated chicken during different periods. The mixture synbiotic and phytobiotic led to no significant increase in AST with unvac-cinated and increase of ALT level in vaccinated groups. Also, previous feed additive increased total protein in both vaccinated and unvac-cinated chickens. Supplementation mixture of both synbiotic and phytobiotic to diet increased total protein in unvaccinated and vaccinated chicken. Rations supplemented with synobiotic and phytobiotic increased albumin level in unvaccinated chicken and decreased with vac-cinated chicken during different periods. Consequently, mixtures of synobiotic and phytobiotic appeared the same trend. On the other, using synobiotic and phytobiotic showed increase globulin level with unvaccinated chicken and decrease with vaccinated chicken, while the mixture of them gave higher level of globulin with unvaccinated or vaccinated chicken during different periods, except at 21 day, the globulin level had slight decrease with unvaccinated chicken. At the same time supplementation synobiotic and phytobiotic or their mixture with unvaccinated or vaccinated chicken revealed normal histological criteria. In conclusion, dietary supplementation of syonbiotic and phytobiotic improved the gut health by decreasing the caecal total coliform count with no adverse effect.The aim of this experiment is to study the effect of dietary supplementation of synobiotic, phytobiotic and their mixture on kidney and liver functions and some histological criteria of broiler chicken.

ВЫЯВЛЕНИЕ УСТОЙЧИВОСТИ К АНТИБИОТИКАМ У ВОЗБУДИТЕЛЯ ГИСТОФИЛЕЗА КРУПНОГО РОГАТОГО СКОТА Histophilus somni

ВЫЯВЛЕНИЕ УСТОЙЧИВОСТИ К АНТИБИОТИКАМ У ВОЗБУДИТЕЛЯ ГИСТОФИЛЕЗА КРУПНОГО РОГАТОГО СКОТА Histophilus somni

PROPERTIES OF EXPERIMENTAL SAMPLES OF VACCINE AGAINST AVIAN INFECTIOUS CORYZA

PROPERTIES OF EXPERIMENTAL SAMPLES OF VACCINE AGAINST AVIAN INFECTIOUS CORYZA

Seroprevalence of Newcastle disease in backyard chickens in selected districts of Banadir region, Somalia.

A cross-sectional study was carried out in the period between January and April 2019 with the aim of establishing prevalence of Newcastle disease (ND) in backyard chickens in Banadir region of Somalia using indirect enzyme-linked immunosorbent assay (iELISA). A total of 373 unvaccinated free scavenging backyard chickens were sampled from five districts in Banadir region, namely Dharkenley, Hodan, Wadajir, Hawlwadag, and Daynile. The overall prevalence was found to be 39.4% (95% confidence interval: 34.6-44.4%) with a mean antibody titre of 3844.10 ± 263.3 (standard error). The seroprevalence of ND virus (NDV) antibody in Wadajir district was the highest (66.6%) followed by Hawlwadag, Daynile, Dharkenley, and Hodan with prevalence of 56%, 42.1%, 42.35%, and 10.6%, respectively, with statistically significant differences (P < 0.05). Adult chickens had significantly higher prevalence (43.8%) than growers (19.4%) (P < 0.05). The present study, which is the first of its kind in Somalia to the best of our knowledge, concluded that the disease is highly prevalent in the study area; therefore, molecular studies on the characteristics of circulating strains are to be carried out in order to develop an evidence-based control programme and minimize the economic and social impacts of ND on smallholders.

Transcriptomic Analysis of Long-Term Protective Immunity Induced by Vaccination With Mycoplasma gallisepticum Strain ts-304.

Live attenuated vaccines are commonly used to control Mycoplasma gallisepticum infections in chickens. M. gallisepticum ts-304 is a novel live attenuated vaccine strain that has been shown to be safe and effective. In this study, the transcriptional profiles of genes in the tracheal mucosa in chickens challenged with the M. gallisepticum wild-type strain Ap3AS at 57 weeks after vaccination with ts-304 were explored and compared with the profiles of unvaccinated chickens that had been challenged with strain Ap3AS, unvaccinated and unchallenged chickens, and vaccinated but unchallenged chickens. At two weeks after challenge, pair-wise comparisons of transcription in vaccinated-only, vaccinated-and-challenged and unvaccinated and unchallenged birds detected no differences. However, the challenged-only birds had significant up-regulation in the transcription of genes and enrichment of gene ontologies, pathways and protein classes involved in infiltration and proliferation of inflammatory cells and immune responses mediated through enhanced cytokine and chemokine production and signaling, while those predicted to be involved in formation and motor movement of cilia and formation of the cellular cytoskeleton were significantly down-regulated. The transcriptional changes associated with the inflammatory response were less severe in these mature birds than in the relatively young birds examined in a previous study. The findings of this study demonstrated that vaccination with the attenuated M. gallisepticum strain ts-304 protects against the transcriptional changes associated with the inflammatory response and pathological changes in the tracheal mucosa caused by infection with M. gallisepticum in chickens for at least 57 weeks after vaccination.

A Comparative Study of Pathology and Host Immune Response Induced by Very Virulent Infectious Bursal Disease Virus in Experimentally Infected Chickens of Aseel and White Leghorn Breeds.

Indigenous breeds of young chickens in India are believed to be resistant to the classical strain of infectious bursal disease virus (IBDV). However, the mechanism underlying this resistance is obscure. Innate immunity is a key factor in defining the clinical course and pathology of microbial infections. The present study is aimed to compare the pathology of very virulent IBDV (vvIBDV) and immunological host response in experimentally infected - vaccinated and unvaccinated indigenous Aseel and commercial White Leghorn chickens. The viral loads and innate immune gene expression profiles of MDA-5, Mx, IFN-α, and IFN-β in different lymphoid organs were analyzed by quantitative PCR. The histopathological scores in Aseel birds were lower than in White Leghorns despite comparable viral loads. The degrees of histopathological lesions were fewer in vaccinated birds than in unvaccinated birds of both breeds. Analysis of innate immune response genes revealed that the cytoplasmic pattern recognition receptor MDA-5 gene was overexpressed mainly in the cecal tonsils of both vaccinated and nonvaccinated White Leghorn chickens. An increase in the expression of the IFN-α gene was seen in the cecal tonsils of Aseels, and an increase in IFN-β gene expression was seen in the thymuses of White Leghorns following vvIBDV challenge both in vaccinated and nonvaccinated birds. In addition, we observed that the Mx gene plays a minimal role, if any, in vvIBDV infection of the breeds under study. It remains interesting and important that although vvIBDV causes disease in indigenous Aseel birds, the faster clearance and reduced pathology of the virus in Aseel birds compared to White Leghorn chicken indicate some unidentified innate immune factors that are limiting IBDV in this breed. Further studies will be required to correlate kinetics of humoral and cellular immune response in relation to the virus load in different organs to illuminate the mechanism of genetic resistance in native breeds of chicken.

Evaluation of the Razi Ornithobacterium rhinotracheale Vaccine by Experimental Challenge System Using LaSota Strain

BACKGROUND Ornithobacterium rhinotracheale (ORT) is a remarkable pathogen in the world poultry industry. The vaccine against this agent is used in poultry farms to prevent infection and reduce the incidence of disease. OBJECTIVES: In the present study, the efficacy of the first Iranian inactivated ORT vaccine produced by the Razi Vac-cine and Serum Research Institute was evaluated using the experimental challenge system . METHODS: Ninety day-old specific-pathogen-free White leghorn chickens were divided randomly into five groups of 18 chickens. The birds were housed in separate specific cages in isolation rooms. At the age of 14 days, the birds of two groups were vaccinated. Afterwards, at the age of 42 days, two groups of unvaccinated chickens and all of the vaccinated subjects were challenged with the LaSota strain of Newcastle Disease Virus (NDV) and ORT. One group of unvaccinated birds was maintained as the negative control. Blood samples were taken from chickens on days 14 (before vaccination) and 42 (before challenge) of the experiment. In addition, blood samples were collected on days 2, 4, 6, 8, 10, and 12 after the challenge (AC). On days 2, 4, 6, 8, 10, and 12 after challenging with ORT, the isolation and molecular detection of the bacteria were performed on samples from the trachea, lungs, air sacs, liver, and spleen. RESULTS: Following vaccination with the Razi ORT vaccine, the titers of antibody in vaccinated chickens were shown to be significantly higher than those of unvaccinated birds. In vaccinated groups, the ORT was not recovered in cultures from lungs, trachea, and air sacs. In the unvaccinated birds challenged with ORT, bacteria were isolated from lungs, tra-chea, and air sacs. Using the polymerase chain reaction method, ORT was only detected from samples of lungs, trachea, and air sacs 2 days after challenge (DAC) in vaccinated groups. Meanwhile, ORT was detected in lungs, trachea, and air sacs until 4 days after challenge in unvaccinated birds. CONCLUSIONS: We concluded that the Razi ORT vaccine was effective in protecting layer chickens against infection with serotype A of the ORT.

Molecular and pathological investigation of a natural outbreak of Newcastle disease caused by genotype XVII in White Leghorn chickens

ABSTRACT Newcastle disease (ND) is an infectious viral poultry disease with great economic consequences. In developing countries, outbreaks of ND caused by virulent Newcastle disease virus (NDV) have been identified as a limiting factor to the growth of the poultry industry. Limited reports exist on the pathology of natural field infection caused by NDV genotype XVII in chickens. Here, we present clinical, pathological and molecular investigation of confirmed ND in a 24-week-old layer-type, semi-intensive poultry flock with recorded mortality of over 50%. During PM examination, tissues were harvested for virus isolation, histopathology and immunohistochemistry. Virus isolation was performed in 10-day-old embryonated chicken eggs, and a haemagglutinating agent thereof identified by one-step reverse transcription-polymerase chain reaction (RT–PCR). For the genotyping of the isolate, the full fusion gene was sequenced. Clinical signs observed included general body lethargy, inappetence and greenish diarrhoeic faeces from the cloaca before death with daily mortality exceeding 100 chickens. The pathology was characteristic of a viral haemorrhagic infection, with serosal haemorrhages, mucosal surface erosion and ulceration. In most of the carcasses, the main lesions seen included airsacculitis, meningeal congestion, haemorrhagic oophoritis, pancreatic necrosis, enteritis and faecal matting of the vent. Virus isolation and RT–PCR made a confirmatory diagnosis of ND. Based on the cleavage site motif sequence (112RRQKR/F117), the isolate was identified as a virulent strain with phylogenetic analysis showing clustering in genotype XVII viruses. To the best of the authors’ knowledge, this is the first report describing the pathological findings of a natural outbreak caused by NDV involving viruses of genotype XVII. RESEARCH HIGHLIGHTS First report of a natural outbreak of Newcastle disease in White Yarkon Leghorns. The outbreak was caused by virulent NDV belonging to genotype XVII. Pathology differed slightly from those in experimental studies using SPF and other unvaccinated chickens.

Evolutionary Analysis of Infectious Bronchitis Virus Reveals Marked Genetic Diversity and Recombination Events.

In the last 5 years, frequent outbreaks of infectious bronchitis virus (IBV) are observed in both broiler and layer chicken flocks in the Kingdom of Saudi Arabia (KSA) in spite of extensive usage of vaccines. The IBV is a widespread avian coronavirus affecting both vaccinated and unvaccinated chicken flocks and is attributed to significant economic losses, around the globe. In the present study, 58 (n = 58) samples were collected from four different commercial poultry flocks from 8 KSA districts during 2019. A total of nine positive isolates (9/58; 15.5%), based on real-time reverse transcriptase PCR targeting nucleocapsid (N) gene, were used for further genetic characterization and evolutionary analysis. Genetic characterization of the partial spike (S1) gene revealed the clustering of the reported isolates into three different genotypes, whereas four additional isolates were grouped within 4/91 genotype, two isolates within IS/885 genotype, one isolate was closely related to IS/1494/06, and two isolates were grouped within classic serotype (vaccine-like strains). Phylodynamic revealed clustering of four isolated viruses within GI-13 lineage, three isolates within GI-23 lineage, and two isolates within GI-1 lineage. Results indicate that there are high evolutionary distances between the newly identified IBV strains in this study and the commercially used vaccines (GI-1), suggesting that IBV strains circulating in the KSA are under constant evolutionary pressures. Selective pressure biostatistics analyses consistently demonstrate the presence of a higher positive score which highlights the role of natural selection, a mechanism of virus evolution on sites located on the protein surface, within or nearby domains involved in viral attachment or related functions. Recombination analysis revealed emergence of two isolates through recombination events resulting in new recombinant viruses. Taken together, these finding demonstrate the genetic and evolutionary insights into the currently circulating IBV genotypes in KSA, which could help to better understand the origin, spread, and evolution of infectious bronchitis viruses, and to ascertain the importance of disease monitoring as well as re-evaluation for the currently used vaccines and vaccination programs.