Infectious Diseases in Poultry

A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Poultry".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 24917

Special Issue Editors


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Guest Editor
Department of Veterinary Medicine, University of Bari Aldo Moro, 70010 Valenzano, Italy
Interests: avian diseases; rabbit diseases; wildlife diseases; bacteriology; antibiotic resistance; natural substances
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Animal Medicine, Production and Health, University of Padova, 35020 Legnaro, Italy
Interests: infectious diseases; epidemiology; vaccine kinetics; viruses of companion animals
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

It is well-known that poultry is one of the most widespread food industries on a global scale. In recent years, significant improvements in poultry welfare have been introduced in poultry rearing systems, particularly in the egg production sector. These improvements have intensified some management problems, but have also created more difficulties in infection control, allowing traditional and emerging diseases to occur with economic losses to the poultry industry. Several different viral and bacterial diseases may affect poultry. Moreover, some infections, such as those due to Campylobacter spp., usually occur in poultry without symptoms, representing a problem for human health. The European Union recommends the prudent use of antibiotics in poultry production systems considering the possible implications for the development of antimicrobial resistance. Therefore, the implementation of biosecurity measures and strategies for infectious diseases control has been encouraged, exploring alternatives to the use of antibiotics such as acidifying components, natural substances, immunostimulants, and vaccines. Researchers unceasingly work on gaining knowledge, new results, and innovation in poultry diseases control. The aim of this Special Issue is to disseminate new data on epidemiology, pathogenic mechanisms, diagnostic tools, and vaccine development for infectious diseases prevention and control.

Dr. Elena Circella

Dr. Claudia Maria Tucciarone

Guest Editors

 

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Keywords

  • poultry
  • infectious diseases
  • epidemiology
  • transmission pathways
  • diagnostic tools
  • vaccines
  • infectious diseases control and management

Published Papers (11 papers)

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Research

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15 pages, 862 KiB  
Article
In Vitro Characterization of Probiotic Potential of Limosilactobacillus fermentum against Salmonella Gallinarum Causing Fowl Typhoid
by Adnan Mehmood, Muhammad Nawaz, Masood Rabbani and Muhammad Hassan Mushtaq
Animals 2023, 13(8), 1284; https://doi.org/10.3390/ani13081284 - 8 Apr 2023
Cited by 3 | Viewed by 1872
Abstract
Fowl typhoid, a septicaemic disease of poultry, is caused by Salmonella Gallinarum and leads to severe economic losses. The aim of the present study was to isolate, select and characterize indigenous probiotic lactobacilli with anti-Salmonella Gallinarum activity. A total 55 lactobacilli were [...] Read more.
Fowl typhoid, a septicaemic disease of poultry, is caused by Salmonella Gallinarum and leads to severe economic losses. The aim of the present study was to isolate, select and characterize indigenous probiotic lactobacilli with anti-Salmonella Gallinarum activity. A total 55 lactobacilli were isolated from the caeca and ileum parts of healthy chickens and identified to species level by 16S rDNA sequencing. All the isolates were initially screened for antimicrobial activity and selected isolates were further subjected to in vitro evaluation of probiotic properties. Lactobacilli isolates (n = 21) showed varying levels of activity (08–18 mm) against Salmonella Gallinarum. These selected isolates also showed tolerance to acidic conditions (pH 3 and 4). Out of these 21 isolates, 13 showed growth (>0.5 OD at 600 nm) 0.3% bile salts. Moreover, these isolates also had the ability of auto-aggregation (20.05 ± 0.62%–50.70 ± 1.40%), and co-aggregation with Salmonella Gallinarum (5.22 ± 0.21%–42.07 ± 0.70%). Results revealed that lactobacilli had a higher level of resistance to vancomycin (100%), streptomycin (100%), ciprofloxacin (95%), gentamicin (90%), doxycycline (90%), oxytetracycline (85%), and bacitracin (80%), and a lower level of resistance to penicillin (33%), erythromycin (28%), chloramphenicol (23%), fusidic acid (23%) and amoxicillin (4%). The Limosilactobacillus fermentum PC-10 and PC-76 were sensitive to most of the antibiotics. The overall results revealed that two Limosilactobacillus fermentum strains (PC-10 and PC-76) fulfill the in vitro selection criteria of probiotics, i.e, tolerance to low pH, resistance to bile salts, auto-aggregation, co-aggregation with Salmonella Gallinarum, and absence of acquired antibiotic resistance. The Limosilactobacillus fermentum PC-10 and PC-76 also inhibited the (>5 log10) growth of Salmonella Gallinarum in co-culture assay. It is concluded that Limosilactobacillus fermentum PC-10 and PC-76 may be further investigated and developed as anti-Salmonella Gallinarum probiotics for poultry. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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12 pages, 2610 KiB  
Article
Genetic Heterogeneity and Mutated PreS Analysis of Duck Hepatitis B Virus Recently Isolated from Ducks and Geese in China
by Shuqi Xu, Xinhao Mu, Xin Xu, Congying Bi, Jun Ji, Yunchao Kan, Lunguang Yao, Yingzuo Bi and Qingmei Xie
Animals 2023, 13(8), 1282; https://doi.org/10.3390/ani13081282 - 8 Apr 2023
Cited by 1 | Viewed by 1567
Abstract
In this study, we detected 12 duck and 11 goose flocks that were positive for duck hepatitis B virus (DHBV) using polymerase chain reaction and isolated 23 strains between 2020 and 2022 in China. The complete genomes of goose strains E200801 and E210501 [...] Read more.
In this study, we detected 12 duck and 11 goose flocks that were positive for duck hepatitis B virus (DHBV) using polymerase chain reaction and isolated 23 strains between 2020 and 2022 in China. The complete genomes of goose strains E200801 and E210501 shared the highest identity (99.9%), whereas those of strains Y220217 and E210526 shared the lowest identity (91.39%). The phylogenetic tree constructed based on the genome sequences of these strains and reference strains was classified into three major clusters: the Chinese branch DHBV-I, the Chinese branch DHBV-II, and the Western branch DHBV-III. Furthermore, the duck-origin strain Y200122 was clustered into a separate branch and was predicted to be a recombinant strain derived from DHBV-M32990 (belonging to the Chinese branch DHBV-I) and Y220201 (belonging to the Chinese branch DHBV-II). Additionally, preS protein analysis of the 23 DHBV strains revealed extensive mutation sites, almost half of which were of duck origin. All goose-origin DHBV contained the mutation site G133E, which is related to increased viral pathogenicity. These data are expected to promote further research on the epidemiology and evolution of DHBV. Continuing DHBV surveillance in poultry will enhance the understanding of the evolution of HBV. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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17 pages, 2858 KiB  
Article
Tissue Tropism of H9N2 Low-Pathogenic Avian Influenza Virus in Broiler Chickens by Immunohistochemistry
by Márta Bóna, István Kiss, Lilla Dénes, Anna Szilasi and Míra Mándoki
Animals 2023, 13(6), 1052; https://doi.org/10.3390/ani13061052 - 14 Mar 2023
Cited by 3 | Viewed by 2305
Abstract
The H9N2 subtype of low-pathogenic avian influenza viruses (LPAIV) is a widespread pathogen of poultry that can also infect humans. The characterization of viral infections is a complex process, involving clinical, pathological, and virological investigations. The aim of this study was to adapt [...] Read more.
The H9N2 subtype of low-pathogenic avian influenza viruses (LPAIV) is a widespread pathogen of poultry that can also infect humans. The characterization of viral infections is a complex process, involving clinical, pathological, and virological investigations. The aim of this study was to adapt and optimize an immunohistochemical (IHC) technique developed for LPAIVs specifically for the detection of H9N2 virus antigens in infected tissues. Twenty-one-day-old broiler chickens were inoculated with three different strains of H9N2 virus by different infection routes (i.e., intranasal-intratracheal and intravenous) or co-infected with infectious bronchitis virus (IBV) and observed for 11 days post infection. The suggested IHC protocol was modified: (i) DAB (diamino-benzidine) was substituted with AEC (3-amino-9-ethyl carbazole) as chromogen; and (ii) indirect two-step immune reactions of monoclonal primary and peroxidase-labeled anti-mouse secondary antibodies were used instead of avidin–biotin complexes. Avian influenza virus antigen appears as a red precipitate in the nuclei of affected cells but can also be identified in the cytoplasm. Mild hyperemia and congestion were observed in the trachea, air sac, and lungs of the challenged birds, and fibrinous exudate was found at the bifurcation in a few cases. Neither gross pathological nor IHC lesions were found in the control group. Using the optimized protocol and an associated scoring scheme, it was demonstrated that the H9N2 strains tested exhibited respiratory and urinary tract tropism irrespective of the route of inoculation. On day 5, viral antigen was detected in the respiratory tract and kidney in 30–50% of the samples. On day 11, no IHC signal was observed, indicating the lack of viral replication. Slight differences in viral antigen expression were found between the different H9N2 virus strains, but, in contrast to highly pathogenic avian influenza (HPAI), no viral antigen was detected in the brain and pancreas. Thus, IHC can be considered as an informative, visual addition to the toolkit for the characterization of H9N2 LPAIV infections. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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16 pages, 2677 KiB  
Article
Diagnosis of Infectious Laryngotracheitis Outbreaks on Layer Hen and Broiler Breeder Farms in Vojvodina, Serbia
by Marko Pajić, Slobodan Knežević, Biljana Djurdjević, Vladimir Polaček, Dalibor Todorović, Tamaš Petrović and Sava Lazić
Animals 2022, 12(24), 3551; https://doi.org/10.3390/ani12243551 - 15 Dec 2022
Cited by 6 | Viewed by 2245
Abstract
Infectious laryngotracheitis (ILT) is a respiratory disease of poultry characterized by high morbidity and variable mortality. ILT is caused by Gallid alpha herpesvirus-1 (GaHV-1), which is transmitted horizontally and most susceptible are chickens older than 4 weeks. After almost two decades since last [...] Read more.
Infectious laryngotracheitis (ILT) is a respiratory disease of poultry characterized by high morbidity and variable mortality. ILT is caused by Gallid alpha herpesvirus-1 (GaHV-1), which is transmitted horizontally and most susceptible are chickens older than 4 weeks. After almost two decades since last appearance of this disease in Vojvodina, an outbreak occurred from April 2020 to August 2021 on five laying hen farms and one broiler breeder flock farm. Clinical signs were mild to severe respiratory symptoms, unilateral or bilateral head swelling, serous nasal discharge, conjunctivitis and increased tearing. There was a decrease in feed consumption (2.1–40.0%) and egg production (2.7–42.0%), weight loss and mortality increased (0.8–31.5%). Pathomorphological changes were localized in the upper respiratory tract. Total of 200 carcasses were examined; 40 pooled samples were analyzed by PCR, and 40 by bacteriological analysis. ILT virus was confirmed in tracheal tissue samples. Infected flocks were not vaccinated against this disease. Five flocks had coinfection with Avibacterium paragallinarum. Three-to-four weeks after the first reported case in the flock, clinical symptoms had ceased. Future control and prevention strategies will involve the procurement of flocks vaccinated by recombinant vaccine or the registration of live attenuated vaccines and their use during the rearing period. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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13 pages, 7258 KiB  
Article
Pathological and Molecular Characterization of a Duck Plague Outbreak in Southern China in 2021
by Zhipeng Liang, Jinyue Guo, Sheng Yuan, Qing Cheng, Xinyu Zhang, Zhun Liu, Congying Wang, Zhili Li, Bo Hou, Shujian Huang and Feng Wen
Animals 2022, 12(24), 3523; https://doi.org/10.3390/ani12243523 - 13 Dec 2022
Cited by 3 | Viewed by 1697
Abstract
Duck plague (DP) is a highly contagious viral disease in ducks caused by the duck plague virus (DPV). The DPV, a member of Herpesviridae, poses a severe threat to the waterfowl farming industry worldwide. In this study, we reported a recent outbreak [...] Read more.
Duck plague (DP) is a highly contagious viral disease in ducks caused by the duck plague virus (DPV). The DPV, a member of Herpesviridae, poses a severe threat to the waterfowl farming industry worldwide. In this study, we reported a recent outbreak of DPV in domestic laying ducks at 310 days of age from southern China in December 2021. The gross lesion, histopathologic examination, molecular detection, and genetic characterization studies of DPV are described here. As a result, gross lesions such as an enlarged congestive spleen and liver were observed. Liver with vacuolar degeneration and small vacuoles and spleen with hemosiderosis were remarkable microscopic findings. Our results suggested that the liver had the highest viral load, followed by the trachea, pancreas, kidney, brain, spleen, and heart. In addition, DPV was successfully isolated in chicken embryo fibroblast cell culture and designated as DP-GD-305-21. The UL2, UL12, UL41, UL47, and LORF11 genes of DP-GD-305-21 shared a high nucleotide homology with the Chinese virulent (CHv) strain and the Chinese variant (CV) strain. In conclusion, this study reports the isolation and molecular characterization of DPV from a recent outbreak in southern China. Our results contributed to the understanding of the pathological and molecular characterization of currently circulating DPV in China. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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16 pages, 1216 KiB  
Article
Prevalence and Antimicrobial Resistance of Campylobacter jejuni and Campylobacter coli from Laying Hens Housed in Different Rearing Systems
by Gaia Casalino, Giancarlo Bozzo, Francesca Rita Dinardo, Francesco D’Amico, Michela Maria Dimuccio, Antonio Camarda, Edmondo Ceci, Diana Romito and Elena Circella
Animals 2022, 12(21), 2978; https://doi.org/10.3390/ani12212978 - 29 Oct 2022
Cited by 1 | Viewed by 1296
Abstract
Campylobacter (C.) jejuni and C. coli are responsible for food poisoning in humans. Laying hens may host the bacteria usually without developing symptoms. The aims of this paper were to evaluate the incidence of C. jejuni and C. coli infection in laying hen [...] Read more.
Campylobacter (C.) jejuni and C. coli are responsible for food poisoning in humans. Laying hens may host the bacteria usually without developing symptoms. The aims of this paper were to evaluate the incidence of C. jejuni and C. coli infection in laying hen flocks housed in different rearing systems, the plasma levels of two welfare indicators (corticosterone and interleukin 6, IL-6) and the antimicrobial resistance of the detected Campylobacter strains. Two different flocks (1 and 2) from cage (A), barn (B) and aviary (C) farms were investigated. The highest (p < 0.05) levels of IL-6 were detected in laying hens housed in aviaries. A similar trend emerged in corticosterone level, although differences were found between C1 and C2. C. jejuni and C. coli were identified in 43.5% and 38.9% of birds, respectively. In total, 14 out of 177 (7.9%) hens simultaneously hosted C. jejuni and C. coli.C. jejuni was prevalently detected in hens housed in barns (B1: 53.3%; B2: 46.7%) and aviaries (C1: 34.6%; C2: 86.7%). Conversely, laying hens housed in cages were significantly exposed to infection of C. coli (A1: 41.9%; A2: 80%) while, regarding barns and aviaries, a significant prevalence emerged only in flocks B2 (40%) and C1 (54.8%). Simultaneous infection was statistically significant in barn B1 (36.7%). Antibiotic resistance was mainly detected among C. coli strains, and it was most frequent for fluoroquinolones and tetracycline. Multidrug resistance was also found in C. jejuni (19.7%) and C. coli (17.5%) strains. Based on the results of this study, we recommend increasing biosecurity and hygienic measures to manage hen flocks. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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11 pages, 568 KiB  
Article
Virulence Factors and Antimicrobial Resistance Profile of Escherichia Coli Isolated from Laying Hens in Italy
by Lorenzo Gambi, Rachele Rossini, Maria Luisa Menandro, Giovanni Franzo, Francesco Valentini, Giovanni Tosi, Mario D’Incau and Laura Fiorentini
Animals 2022, 12(14), 1812; https://doi.org/10.3390/ani12141812 - 15 Jul 2022
Cited by 5 | Viewed by 1684
Abstract
Colibacillosis is the most common bacterial disease in the poultry industry. The isolation of Escherichia coli (E. coli) strains with multiple resistance to various classes of antimicrobials has been increasing in recent years. In this study, antimicrobial resistance features, serotyping and [...] Read more.
Colibacillosis is the most common bacterial disease in the poultry industry. The isolation of Escherichia coli (E. coli) strains with multiple resistance to various classes of antimicrobials has been increasing in recent years. In this study, antimicrobial resistance features, serotyping and the presence of avian pathogenic Escherichia coli (APEC) virulence genes were investigated on a total of 71 E. coli strains isolated during outbreaks of colibacillosis in laying hens. The correlation between these features was evaluated. The most frequently isolated serogroups were O2 and O88. Resistance was often detected with nalidixic acid (49%) and ampicillin (38%), while all strains were sensitive to ceftiofur and florfenicol. Overall, 25% of the isolates showed resistance to at least three or more antimicrobial classes (multidrug-resistant strains), and 56% of the isolates were defined as APEC strains (due to the presence of at least five virulence genes). Correlation between the different parameters (virulence genes, serogroup and antimicrobial resistance) did not reveal relevant associations. The comparison of the obtained results with those of similar studies highlighted the importance of continuous monitoring in order to have a better understanding of colibacillosis. An evaluation of the national epidemiological situation would allow, especially with regard to antimicrobial resistance, to focus on the right measures in order to prioritize the available resources for effective disease control. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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10 pages, 900 KiB  
Article
Release of DNA from Dermanyssus gallinae during the Biting Process
by Nicola Pugliese, Donato Antonio Raele, Antonella Schiavone, Maria Assunta Cafiero, Lucia Potenza, Rossella Samarelli, Elena Circella, Ilaria Vasco, Germana Pennuzzi and Antonio Camarda
Animals 2022, 12(9), 1084; https://doi.org/10.3390/ani12091084 - 22 Apr 2022
Cited by 1 | Viewed by 1458
Abstract
Dermanyssus gallinae is a hematophagous ectoparasitic mite that usually infests poultry, but is also known for occasionally attacking other animals and humans. It represents a major problem for poultry systems all over the world, with detrimental effects for both production and animal welfare. [...] Read more.
Dermanyssus gallinae is a hematophagous ectoparasitic mite that usually infests poultry, but is also known for occasionally attacking other animals and humans. It represents a major problem for poultry systems all over the world, with detrimental effects for both production and animal welfare. Despite the significance of D. gallinae, very little is known about the biting process to date. Therefore, this study has aimed to verify if mite DNA is injected into the host skin during the blood meal. Mite DNA has been detected by seminested PCR from infested chicken skin and quantified by real-time PCR. Furthermore, its localization within the host tissue has been checked by fluorescent in situ hybridization. Results showed that a very little amount of D. gallinae DNA can be released by mites, suggesting that the latter do not introduce whole or partially destroyed cells into the host, but rather it injects traces of nucleic acids, possibly together with merocrine secretions. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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9 pages, 985 KiB  
Communication
First Molecular Survey to Detect Mycoplasma gallisepticum and Mycoplasma synoviae in Poultry Farms in a Strategic Production District of Sicily (South-Italy)
by Paola Galluzzo, Sergio Migliore, Lucia Galuppo, Lucia Condorelli, Hany A. Hussein, Francesca Licitra, Miriana Coltraro, Sabrina Sallemi, Francesco Antoci, Giuseppe Cascone, Roberto Puleio and Guido Ruggero Loria
Animals 2022, 12(8), 962; https://doi.org/10.3390/ani12080962 - 8 Apr 2022
Cited by 7 | Viewed by 2442
Abstract
Mycoplasmas are recognized as avian pathogens, which may cause both respiratory disease and synovial infections in poultry, resulting in severe economic losses. Our study aims to determine the occurrence of Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) among commercial and rural laying hens [...] Read more.
Mycoplasmas are recognized as avian pathogens, which may cause both respiratory disease and synovial infections in poultry, resulting in severe economic losses. Our study aims to determine the occurrence of Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) among commercial and rural laying hens located in Ragusa province (South Italy), using a duplex real time PCR. Four hundred tracheal swabs were collected from seven commercial (200 swabs) and 25 rural (200 swabs) farms without any clinical disease history. Out of 400 swabs collected, 50 (12.5%) and 93 (23.25%) were positive for MG and MS, respectively. In particular, 9 (18%) and 22 (23.65%) positive swabs for MG and MS, respectively, originated from commercial farms, compared to 41 (82%) and 71 (76.34%) obtained from rural farms. Data obtained show a lower prevalence of MG than MS in the studied farms. Moreover, both pathogens were spread in rural and commercial farms. PCR could be concluded as a rapid and sensitive method for the identification of MG and MS in areas where commercial farms that are declared Mycoplasma-free and rural flocks coexist. These data highlight the importance of surveillance also in rural poultry to monitoring the occurrence of mycoplasmas strains in strategic productive districts. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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10 pages, 1988 KiB  
Article
Molecular Survey of Viral Poultry Diseases with an Indirect Public Health Significance in Central Ethiopia
by Behailu Assefa Wayou, Gezahegne Mamo Kassa, Daniela Pasotto, Teshale Sori, Claudia Maria Tucciarone and Mattia Cecchinato
Animals 2021, 11(12), 3564; https://doi.org/10.3390/ani11123564 - 15 Dec 2021
Viewed by 2515
Abstract
The importance of poultry production is globally increasing, in Ethiopia as well, where high-quality protein and contained costs make poultry a valuable food resource. However, this entails some problems linked to rural, backyard and intensively reared flock proximity and pathogen circulation. This study [...] Read more.
The importance of poultry production is globally increasing, in Ethiopia as well, where high-quality protein and contained costs make poultry a valuable food resource. However, this entails some problems linked to rural, backyard and intensively reared flock proximity and pathogen circulation. This study is aimed at monitoring the presence of important viral pathogens in poultry (infectious bronchitis virus (IBV), avian metapneumovirus (aMPV), infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV)) in Ethiopia. Respiratory and cloacal swabs and bursa of Fabricius and kidney imprints on FTA cards were collected in 2021 from 16 farms and tested for IBV, aMPV, NDV and IBDV. One farm was positive for IBDV, resulting in strains similar to those present in vaccines, belonging to genogroup A1a; two farms were positive for IBV but, due to sensitivity limits, only one sample was sequenced, resulting in a 4/91-like strain (GI-13); a layer farm tested positive for NDV with a Lasota-like vaccine strain. These findings suggest a low presence of these pathogens, probably due to the implementation of vaccination strategies, which is also testified by the detection of vaccine strains. A close diagnostic activity should be implemented on a routine basis in order to monitor pathogen circulation, ameliorate biosecurity measures and protect animal health and production levels. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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Review

Jump to: Research

14 pages, 1643 KiB  
Review
A Review on the Marek’s Disease Outbreak and Its Virulence-Related meq Genovariation in Asia between 2011 and 2021
by Baolin Song, Jehan Zeb, Sabir Hussain, Muhammad Umair Aziz, Elena Circella, Gaia Casalino, Antonio Camarda, Guan Yang, Nicolas Buchon and Olivier Sparagano
Animals 2022, 12(5), 540; https://doi.org/10.3390/ani12050540 - 22 Feb 2022
Cited by 16 | Viewed by 3595
Abstract
Marek’s disease is an infectious disease in poultry that usually appears in neural and visceral tumors. This disease is caused by Gallid alphaherpesvirus 2 infection in lymphocytes, and its meq gene is commonly used in virulent studies for coding the key protein functional [...] Read more.
Marek’s disease is an infectious disease in poultry that usually appears in neural and visceral tumors. This disease is caused by Gallid alphaherpesvirus 2 infection in lymphocytes, and its meq gene is commonly used in virulent studies for coding the key protein functional in oncogenic transformation of the lymphocytes. Although vaccines have been introduced in many countries to control its spread and are proven to be efficient, recent records show a decline of such efficiency due to viral evolution. In this study, we reviewed the outbreak of Marek’s disease in Asia for the last 10 years, together with associated meq sequences, finding a total of 36 studies recording outbreaks with 132 viral strains in 12 countries. The visceral type is the most common (13 in 16 studies) form of Marek’s disease, but additional unobserved neural changes may exist. MD induces liver lymphoma most frequently (11 in 14 studies), and tumors were also found in spleen, kidney, heart, gizzard, skin, intestine, lung, and sciatic nerve. Twelve viral strains distributed in China have been reported to escape the CVI988 vaccine, reaching a mortality rate of more than 30%. Phylogenetic analyses show the internal connection between the Middle East (Turkey, Iraq, Iran, Saudi Arabia), South Asia (India, Indonesia), and East Asia (China and Japan), while external viral communications might occasionally occur. In 18 strains with both sequential and mortality data, amino acid alignment showed several point substitutions that may be related to its virulence. We suggest more behavioral monitoring in Marek’s disease-endemic regions and further studies on strain virulence, together with its Meq protein structural changes. Full article
(This article belongs to the Special Issue Infectious Diseases in Poultry)
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