Infectious Bronchitis Virus Research Articles

Avian Infectious Bronchitis Virus: Molecular Detection in Southwestern Ethiopia Chickens.

Infectious bronchitis virus (IBV) is a significant threat to poultry worldwide, but its status in Ethiopia remains understudied. Thus, this study aimed to detect the virus and associated risk factors in South West Ethiopia. Ninety oropharyngeal swab samples were purposively collected from symptomatic chickens located in Jimma town, Seqa Chekorsa, and Tiro Afeta woredas of the Jimma zone between November 2021 and April 2022 to detect IBV virus by using RT-PCR. A side-by-side questionnaire was administered to assess risk factors. Total RNA was extracted, reverse transcription polymerase chain reaction (RT-PCR) was conducted, and products were visualized under UV light. The overall proportion of IBV was 16.6% (15/90). No statistical association was observed between any of the animal risk factors and the detection of the virus (P=0.57, 0.586, and 1). However, the proportion of birds infected by the virus was higher in males, exotic breeds, and adults compared to females, local breeds, and young birds. Similarly, none of the management risk factors had a significantly different effect on virus detection (P=0.25, 0.09, 0.088, and 0.726). However, improper carcass disposal (OR = 0.43, 95% CI: 0.13-1.4), lack of veterinary services (OR = 2.7, 95% CI: 0.8-8.3), and the presence of wild birds/rodents (OR = 4.4, 95% CI: 0.88-22.3) were associated with increased IBV risk but not cleaning of feeders/drinkers (OR = 1.1, 95% CI: 0.2-4.8). These findings underscore the need for enhanced biosecurity practices and further research to implement informed IBV control strategies in Ethiopia.

The efficacy of simultaneous successive classic and variant infectious bronchitis virus vaccines versus circulating variant II Egyptian field virus.

Being a ubiquitous, highly contagious virus with a continuous mutation and a large number of evolutions worldwide, the infectious bronchitis virus (IBV) continues to wreak problems among Egyptian chickens and generate economic losses. The commonly applied IBV vaccination protocols in broilers include alternatives to classic and/or variant attenuated live virus vaccines. The current study targeted to assess the protective efficacy of concurrent and successive Ma5 and 4/91 vaccine strain regimens against the field variant II IBV strain (IBV-EGY-ZU/Ck-127/2021) in chickens. Commercial broiler chickens were vaccinated with Ma5 and 4/91 strains simultaneously at 1 and 14 days of age. The evaluation parameters included clinical protection and humoral and early innate immunity aspects in the renal tissues of vaccinated and infected birds. The vaccine regimen ameliorated the clinical and histopathological lesions against variant II IBV and enhanced body gain as well as succeeded in preventing tracheal shedding and minimizing cloacal shedding of the field virus. The IL-1β mRNA gene expression was evident as early as 24 hours, with highly significant upregulation at 48 hours post vaccination and 24 hours post challenge (PC) in vaccinated birds. Remarkable upregulation was observed in oligoadenylate synthetases (OAS) expression 48 hours PC in vaccinated and unvaccinated infected birds. The vaccinated birds developed a significant antibody titer of 704.0 ± 111.98 at 28 days of age, with a consistent antibody titer increase after the challenge. Overall, a combination of heterologous protectotype commercial vaccines achieved good protection against the Egyptian variant II IBV strain. This vaccine program could be an effective protocol against the threat posed by IBV viruses circulating in the Egyptian field.

One-pot Golden Gate Assembly of an avian infectious bronchitis virus reverse genetics system.

Avian infectious bronchitis is an acute respiratory disease of poultry of particular concern for global food security. Investigation of infectious bronchitis virus (IBV), the causative agent of avian infectious bronchitis, via reverse genetics enables deeper understanding of virus biology and a rapid response to emerging variants. Classic methods of reverse genetics for IBV can be time consuming, rely on recombination for the introduction of mutations, and, depending on the system, can be subject to genome instability and unreliable success rates. In this study, we have applied data-optimized Golden Gate Assembly design to create a rapidly executable, flexible, and faithful reverse genetics system for IBV. The IBV genome was divided into 12 fragments at high-fidelity fusion site breakpoints. All fragments were synthetically produced and propagated in E. coli plasmids, amenable to standard molecular biology techniques for DNA manipulation. The assembly can be carried out in a single reaction, with the products used directly in subsequent viral rescue steps. We demonstrate the use of this system for generation of point mutants and gene replacements. This Golden Gate Assembly-based reverse genetics system will enable rapid response to emerging variants of IBV, particularly important to vaccine development for controlling spread within poultry populations.

Mannan oligosaccharides as a prebiotic for laying hens: effects on fertility, hatchability, productive performance, and immunity.

This experiment examined how adding mannan-oligosaccharides (MOS) to the diet affected fertility, hatching rates, egg production, carcass characteristics, cost-effectiveness, and immune function in laying hens. One hundred and twenty Mandarah chickens (30 hens and 3 roosters per group) were randomly chosen between 34 and 50wk old and divided into four groups. The first group was the control group, which was given just the basal diet. The basal diet was given to the second, third, and fourth experimental groups along with three different levels of MOS (0.1, 0.2, and 0.5g/kg diet, respectively). Results found that hens fed MOS at various levels laid eggs at a significantly higher rate, enhanced egg number, egg mass and feed conversion ratio than the control group (P < 0.05). MOS seemed to improve carcass quality. The best results for egg quality (Haugh unit) and testosterone levels were seen with a dose of 0.5g/kg of MOS compared to the control birds (P < 0.05). All MOS levels led to higher estradiol-17β (E2) levels and better economic efficiency (EE). MOS also improved the hens' immune systems as compared to the control group. Hens-fed MOS had significantly greater levels of antibodies against Influenza viruses (H9N2) and Infectious Bronchitis Virus (P < 0.05). Also, the spleen and thymus gland, both crucial immune system components, were slightly larger (P < 0.05). It's important to note that fertility rates, hatchability, and embryo mortality rates remained similar across all groups. So, our findings suggest that incorporating MOS into the birds' diet enhances their productivity, strengthens their immune system, improves EE, and contributes to the overall health of the hens.

Rapid detection of avian leukemia virus using CRISPR/Cas13a based lateral flow dipstick.

Avian leukemia virus (ALV) is one of the main pathogens of poultry tumor diseases, and has caused significant economic losses to the poultry industry since its discovery. Therefore, establishing a rapid detection method is essential to effectively prevent and control the spread of ALV. In this study, specific CRISPR RNA (crRNA) and recombinase-aided amplification (RAA) primers with T7 promoter were designed based on the relatively conserved sequence of avian leukemia virus. When crRNA recognized the target sequence, Cas13a protein was activated to cut the reporting probes, and then the detection results were read by using lateral flow dipstick (LFD). The RAA-CRISPR/Cas13a-LFD reaction system was constructed. The RAA amplification time, Cas13a protein concentration, crRNA concentration and CRISPR reaction time were optimized to evaluate the specificity, sensitivity and reproducibility of the system. Finally, RAA-CRISPR/Cas13a-LFD method was compared with Polymerase chain reaction (PCR)-Agarose electrophoresis method and qPCR method in the detection of clinical samples, and the reliability of RAA-CRISPR/Cas13a-LFD method was evaluated. The results showed that the RAA-CRISPR/Cas13a-LFD method could effectively amplify the target gene at 37°C for 40 min, and the test results could be determined by LFD visual observation. The method had good specificity and no cross-reaction with Marek's disease virus (MDV), Fowl adenovirus (FAdV), Infectious bursal disease virus (IBDV), Newcastle disease virus (NDV), Infectious laryngotracheitis virus (ILTV), and Infectious bronchitis virus (IBV). The minimum detection limit of the method was 100 copies/μL, and it had good repeatability and stability. The coincidence rate of clinical detection reached 97.69% and 99.23%. In summary, this study established a simple, efficient, accurate and visualized ALV detection method, which can be used for the prevention and rapid clinical diagnosis of avian leukosis (AL).

Identification of a Nephropathogenic Strain of Infectious Bronchitis Virus (IBV) in Some Northern Provinces in Vietnam

Identification of a Nephropathogenic Strain of Infectious Bronchitis Virus (IBV) in Some Northern Provinces in Vietnam

Pathology and molecular detection of influenza Asubtype H9N2 virus in commercial poultry in Nigeria, 2024

Background: After the first Avian Influenza H5N1 outbreak in Nigerian poultry in 2006, subsequent waves of outbreaks occurred, causing substantial losses. Despite effective control measures by 2008, a resurgence in 2015 led to further losses and required depopulation efforts. Aim: The aim of this study was to do Pathology and molecular detection of influenza A subtype H9N2 virus in commercial poultry in Nigeria during 2024. Methods: In February 2024, a poultry farmer reported high mortality in his mixed commercial poultry flock in Ibadan, Nigeria, submitting carcasses to the University of Ibadan's V.T.H. and the FAO Regional Laboratory at NVRI, Vom. Results: Necropsy of nine Isa Brown layers and three Abor Acre broilers revealed cyanosis of comb and wattles, generalized petechial and ecchymotic haemorrhages including shank haemorrhages with sinusitis, pneumonia, and severe greenish faecal pasting also observed. At histopathology, denudation of the tracheal epithelia and parabronchial epithelial necrosis, obliteration, with airsac oedema and emphysema were observed. At NVRI, qPCR detected an Influenza A H9N2 virus in several pooled organ samples of layers, and broilers and eliminating the avian infectious bronchitis and Newcastle disease viruses. Conclusion: This is the first report of H9N2 outbreak in commercial poultry in Southern Nigeria. The high pathogenicity shown in commercial poultry in this outbreak and the risk of dispersal of infected live poultry in Nigeria as previously seen in H5N1 require stakeholders’ intervention.

Molecular Genotyping and Pathogenicity Study for Avian Infectious Bronchitis Virus Currently Epidemic in Chicken Flocks in Egypt during 2021

Molecular Genotyping and Pathogenicity Study for Avian Infectious Bronchitis Virus Currently Epidemic in Chicken Flocks in Egypt during 2021

An Overview of Future Development Methods of Infectious Bronchitis Vaccines

Vaccines are major disease-controlling tools in human and animal practices. Vaccination controlled or even eradicated a long list of diseases worldwide. Classic viral vaccines are usually composed of live or inactivated whole viruses and have been produced for many years. However, they are unsuccessful, especially in persistent infections, fast-evolving viruses, complex and compound antigens, and emerging agents. Novel vaccine development technologies such as DNA, protein, or viral vector vaccines have revolutionized vaccine development and opened a new horizon for study and research in vaccine research and production vision. Newly-developed vaccines, or even most traditional ones, are based on new technologies, especially in human diseases where cost and complications in production can be ignored. However, in animal health, especially for commercial poultry production, the cost of development, simplicity, and mass application of large-scale production cannot be overlooked. In recent years, the significance of producing novel vaccines has been highlighted in parallel with technological advancement, especially with emerging novel variants of infectious bronchitis viruses—serious poultry pathogens for years. In this review, we will introduce some studies on novel vaccine development techniques and investigate the results of those vaccines in the protection of chickens and their clinical outcomes.

Immunogenicity and protective efficacy of an inactivated infectious bronchitis virus vaccine candidate from a local isolate of Bangladesh

Objective: Infectious bronchitis (IB), a highly infectious acute viral disease, is a major burden to the chicken industry worldwide. The research aimed to develop an inactivated IB vaccine using local isolates and assess its immunogenicity compared to other commercial live IB vaccines. Materials and Methods: An inactivated vaccine using a candidate IB virus (PP067159.1: Alim_IB_1001) of the QX genotype was developed according to WOAH guidelines. Chickens were vaccinated with three doses (0.25, 0.5, and 1.0 ml) at 7 days old, with a booster at 37 days old via subcutaneous (SC) and intramuscular (IM) routes. Blood samples were collected on days 7, 37, and 67 to measure immune response by indirect ELISA. On day 67, chickens were challenged with a virulent IBV strain to assess vaccine protection. The experimental IB vaccine’s immunogenicity, protective efficacy, and antibody duration were compared to a live IB vaccine (Live CEVAC® IBird) using three vaccination schedules: killed-followed-killed, live-followed-killed, and live-followed-live. Results: Chickens vaccinated with SC with 1.0 ml showed higher antibody titers compared to other SC and IM routes of vaccination. SC vaccination with 0.5 and 1 ml provided the highest protection (93%). The killed-followed-killed vaccination method produced a more consistent and protective level of antibody titers in chickens compared to the other vaccination schedules. The experimental inactivated IB vaccine led to a higher survival rate (93%) compared to live-followed-killed (87%) and live-followed-live (73%), with statistical significance (p &lt; 0.01). All three chicken groups maintained protective antibody titers (&gt;396) at 307 days, but titers declined faster in the live-followed-live and live-followed-killed groups compared to the killed-followed-killed group. Conclusion: The study found that the experimental inactivated IB vaccination can protect com¬mercial-layer chickens from natural IB outbreaks of the QX genotype.

Incidence and Genetic Investigation of Avian Coronaviruses in Migratory Ducks From South Korea

Coronaviruses (CoVs) belonging to the Gamma-CoV and Delta-CoV genera are widespread in poultry and wildfowl. Migratory birds, particularly duck species, serve as hosts for CoVs and play a pivotal role in transmitting the viruses to other species, including mammals. Despite the potential risks to animals and humans, there remains a narrow knowledge of the genetic and epidemiological properties of CoVs in wild birds. The current research aimed to detect and characterize CoVs present in migratory duck species (Anas acuta, Anas platyrhynchos, and Anas poecilorhyncha) from South Korea. Employing two rounds of pan‐CoV real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) and nested PCR (nPCR) assays amplifying the conserved RNA‐dependent RNA polymerase (RdRp) portion common to all known CoVs, we screened 2120 duck fecal samples collected during 2022–2023. The results indicated the presence of CoVs in 4.2% (91/2120) of samples from migratory ducks. Nucleotide sequencing of the RdRp gene revealed that all identified CoVs were clustered within the Gamma-CoV genus. Further phylogenetic analysis suggested that South Korean gamma‐CoVs belong to the Igacovirus subgenus and share similarities with those found worldwide, highlighting the critical role of migratory ducks in introducing and exporting avian CoVs. We discovered two clade VII igacovirus strains in wild ducks closely related to those in pigeons, implying potential cross infection between these avian species. Overall, our study underscores the importance of active surveillance and monitoring of avian CoVs in wild birds as a preemptive response against the forthcoming emergence of new CoV species that can threaten both animal and human health.

Molecular Characterization and Pathotyping of Avian Infectious Bronchitis Virus in some Egyptian provinces

Molecular Characterization and Pathotyping of Avian Infectious Bronchitis Virus in some Egyptian provinces

Whole genome sequencing analysis of avian infectious bronchitis virus isolated in Hung Yen province in 2021

Infectious bronchitis is an acute disease in chickens caused by the Infectious Bronchitis Virus (IBV). The disease causes serious economic losses in many countries in the world that have chicken farming industries. Even though vaccines have been used, the disease is still very complicated in many provinces and cities in Vietnam. The reason is that the virus strains causing the disease in the field have many changes compared to the vaccine virus strains. Research showed that there are numerous strains and genotypes of IBV in Vietnam. However, only the S1 gene has been studied, and no research has been done on the full genome. In this study, the IBV strain causing disease in 2021 in Hung Yen Province (North Vietnam) was sequenced and analyzed for molecular characteristics. The analysis results showed that strain IBHYM belongs to genotype QX-like (GI-19) and has a close relationship with Chinese IBV strains. The IBHYM strain has higher nucleotide and amino acid similarities with strains of genotype QX-like (87.5% to 95% for nucleotide and 80.2% to 91.3% for amino acid) and the lowest similarity to strains of genotype TC07-like (70.4% to 70.5% for nucleotide and 53.8% to 56.2% for amino acid). The field pathogenic virus strains also have low nucleotide and amino acid similarity with the Massachusetts vaccine strain currently in use (86% for nucleotide and 77.1% for amino acid). Research results show the importance of molecular epidemiological surveillance and the selection of appropriate vaccine strains in Vietnam. This is the first report of sequencing the whole IBV genome in Vietnam.

Molecular identification of the common viral respiratory viruses in backyard chickens in Basrah, Southern Iraq

Many viruses can infect different types of birds, with poultry being the most susceptible. These viral diseases have a direct negative impact on the poultry industry, with significant economic losses. This study examined a group of the most important viruses that infect backyard chickens in 2 specific areas of Basrah Governorate, south of Iraq. The study analyzed avian influenza viruses (AIVs), Newcastle disease virus (NDV), and infectious bronchitis virus (IBV). Two hundred and ninety oropharyngeal swabs, 150 from Abu Al-Khasib and 140 from Shatt Al-Arab regions in the Basrah governorate, were obtained from backyard chickens with clear respiratory signs. The samples were subjected to viral RNA extraction, and the viral nucleic acids were detected using an RT-PCR technique. The overall rate of viral infections was 74.8%, which varied depending on the type of virus: 15.8%, 31.3%, and 27.5% for AIV, NDV, and IBV, respectively. The NDV and IBV had much higher infection rates than that of AIV. In addition, the prevalence of AIV in the Shatt Al Arab district was significantly higher than in the Abul Khasib district. Moreover, there were no significant differences between the NDV and the IBV distributions in either of the targeted regions in this study.

Epidemiological and Molecular identification study of infectious bronchitis virus isolations from broiler chickens in Nineveh governorate

One of the most dreadful infectious viral disease that cause great economic losses for the poultry industry is the infectious bronchitis IB. The present study conducted to epidemiology and the molecular sequences of infectious bronchitis virus from broiler chickens’ fields in Nineveh governorate. The study covered seven regions around the Mosul city included (Al Msayed, Badoosh, Al?Qayara, Wanna, Basheeka, Al-shalalat , Al-hamdanya, and Bartalla) for the period extends from September 2022 to May 2023. The result recorded 16 suspected cases of IB. 14 of them have been diagnosed as IB virus by means of Polymerase Chain Reaction (Nested PCR). Most of the infections were in October and March, five cases of them were recorded in October, four cases in March, two conditions in September, and one case in other months of the study. (PCR), showed that the causative agent of IB in Al?Msayed, Badoosh, Al-Qayara, Wanna, Basheeka, Al shalalat , Al-hamdanya, and Bartalla) was from strain(AAS-IB01M Result showed a new strain which was submitted to the GenBank of the (NCBI) to be registered

Seroprevalence and molecular characterisation of infectious bronchitis virus (IBV) in broiler farms in Sabah, Malaysia.

Infectious bronchitis virus (IBV) is classified as a highly contagious viral agent that causes acute respiratory, reproductive and renal system pathology in affected poultry farms. Molecular and serological investigations are crucial for the accurate diagnosis and management of IBV. The purpose of this study was to determine the seroprevalence of IBV and to characterise the circulating IBV in poultry farms in Sabah Province, Malaysia. To determine IBV antibodies, a total of 138 blood samples and 50 organ samples were collected from 10 commercial broiler flocks in 3 different farms by using the enzyme-linked immunosorbent assay (ELISA) (IDEXX Kit) and reverse transcription-polymerase chain reaction (RT-PCR) followed by sequencing. A total of 94.2% (130/138) of the samples were seropositive for IBV in the vaccinated flock, and 38% (52/138) of the birds was the IBV titre for infection. The selected seropositive samples for IBV were confirmed by RT-PCR, with 22% (11/50) being IBV positive amplified and sequenced by targeted highly conserved partial nucleocapsid (N) genes. Subsequently, phylogenetic analysis constructed using amplified sequences again exposed the presence of Connecticut, Massachusetts, and Chinese QX variants circulating in poultry farms in Sabah, Malaysia. The unexpectedly increasing mean titres in serology indicated that post infection of IBV and highly prevalent IBV in selected farms in this study. The sequencing and phylogenetic analysis revealed the presence of multiple IBV variants circulating in Malaysian chicken farms in Sabah, which further monitoring of genetic variation are needed to better understand the genetic diversity.

Spike Glycoprotein 1 Partial Gene Analysis of GI-19 (QX-like) Infectious Bronchitis Virus Isolated and Propagated from Breeder, Broiler, and Layer Chickens in Java Region

This study aims to identify and characterize receptor binding sites (RBS) and antigenic sites (HVR-I and II) of the S1 gene fragment of the infectious bronchitis virus (IBV) isolated and propagated from commercial chickens in Java Region to monitor recent circulating virus. The samples in this study were the organs which indicated infectious bronchitis infection. The stages of this research consisted of making virus suspensions, isolation, and propagation, as well as molecular detection and characterization of viruses. Virus isolation and propagation were carried out on chicken embryonated eggs aged 11 days via the allantoic route. Culture confirmation was performed by RT-PCR of the S1 gene fragment, followed by sequencing and bioinformatics analysis. The 168-hour propagation was observed in both dwarfed and curled embryos of two isolates from 11 isolates detected as IBV-positive. Phylogenetic tree construction resulted in all isolates being grouped as GI-19 genotype (QX-like). Amino acid identity among QX-like strains was calculated at 87–100%. A total of 210 predicted amino acid residues were observed, including 31 substitutions and 2 deletions. Conclusions of this study were identified and characterized as GI-19 genotype (QX-like) IBV with amino acid changes on S1 fragment from breeder, broiler, and layer chickens in Java Region.

Metatranscriptomic data mining together with microfluidic card uncovered the potential pathogens and seasonal RNA viral ecology in a drinking water source.

Despite metatranscriptomics becoming an emerging tool for pathogen surveillance, very little is known about the feasibility of this approach for understanding the fate of human-derived pathogens in drinking water sources. We conducted multiplexed microfluidic cards and metatranscriptomic sequencing of the drinking water source in a border city of North Korea in four seasons. Microfluidic card detected norovirus, hepatitis B virus (HBV), enterovirus, and Vibrio cholerae in the water. Phylogenetic analyses showed that environmental-derived sequences from norovirus GII.17, genotype C of HBV, and coxsackievirus A6 (CA6) were genetically related to the local clinical isolates. Meanwhile, metatranscriptomic assembly suggested that several bacterial pathogens, including Acinetobacter johnsonii and V. cholerae might be prevalent in the studied region. Metatranscriptomic analysis recovered 349 species-level groups with substantial viral diversity without detection of norovirus, HBV, and CA6. Seasonally distinct virus communities were also found. Specifically, 126, 73, 126, and 457 types of viruses were identified in spring, summer, autumn, and winter, respectively. The viromes were dominated by the Pisuviricota phylum, including members from Marnaviridae, Dicistroviridae, Luteoviridae, Potyviridae, Picornaviridae, Astroviridae, and Picobirnaviridae families. Further phylogenetic analyses of RNA (Ribonucleic Acid)-dependent RNA polymerase (RdRp) sequences showed a diverse set of picorna-like viruses associated with shellfish, of which several novel picorna-like viruses were also identified. Additionally, potential animal pathogens, including infectious bronchitis virus, Bat dicibavirus, Bat nodavirus, Bat picornavirus 2, infectious bursal disease virus, and Macrobrachium rosenbergii nodavirus were also identified. Our data illustrate the divergence between microfluidic cards and metatranscriptomics, highlighting that the combination of both methods facilitates the source tracking of human viruses in challenging settings without sufficient clinical surveillance.

Phylogenetic evolution and impact on the immunogenic response of the Avian Infectious Bronchitis virus

Avian Infectious Bronchitis (IAB) is a viral disease that generates great economic losses in the poultry industry. Due to its structural components and particular immunogenic characteristics, the IB virus, the chicken coronavirus (Gallus gallus), has generated a great challenge for its control, given the emergence of different genotypes with global distribution with changing clinical manifestations. This has generated interest in the study and analysis of the dynamics of the phylogenetic evolution of the virus, as well as the impact on immunological activity, requiring the development of new vaccine strains based on the high variability of the S1 gene portion 1. In the present review, updated information on the phylogenetic evolution of IAV was compiled and the impact on the immunogenic response in poultry production systems is analysed.

Low-temperature exposure in early embryogenesis as a way of increasing the resistance of chicks to infectious diseases

The article is devoted to the problem of increasing the resistance of chicks from hatching to the age of 3 weeks to infectious diseases by technological methods. Dosed low-temperature exposure to the embryo during the sensitive period of early embryogenesis was proposed as an impact factor; influenza vaccine virus was used as a test virus for experimental infection of embryos. It was found that in the embryos after cooling, the titer of the virus was significantly lower by 1.5-12.0 times (p&lt;0.001) compared with the control. This fact indicates a decrease in the replicative activity of viral strains in embryos of this group. In chicken embryos of Russian Snow-White breed after cooling, there was a decrease in the infectious activity of the influenza A virus by 11.5 %, as well as a decrease in the infectious activity of the infectious bronchitis virus by 3.6-6.9 %, depending on the breed of the embryos. The level of chick resistance in the experimental group to diseases of bacterial etiology was also higher, as evidenced by the higher safety of 3-week-old chicks (0.8-1.1 % higher than in the control) and a higher bursa index in 12-day-old chicks (8.5-9.0 % higher than in the control). The hatchability of eggs of the experimental group was also 4.5 % higher than in the control. The effects obtained as a result of hypothermic exposure during this sensitive period of embryogenesis can be explained by inducing the production of heat and cold shock proteins by the embryo, which, in turn, activate innate antiviral reactions caused by major histocompatibility complex. However, this issue requires additional study with the involvement of molecular genetics methods, since the supposed mechanisms that cause an increase in resistance in response to low-temperature exposure in early ontogenesis need to be confirmed.