A survey for selected avian viral pathogens in backyard chicken farms in Finland

A New Variant of Avian Encephalomyelitis Virus Associated with Neurologic Signs in Turkey Poults

Avian encephalomyelitis (AE) is a disease caused by the avian encephalomyelitis virus (AEV) of the genus Tremovirus in the family Picornaviridae. Recently, cases of turkey poults showing neurological signs were submitted to the veterinary diagnostic laboratories at South Dakota State University and the University of Minnesota. The affected birds were showing nervous neurological signs such as tremors, inability to stand, torticollis, and wing drop. Clinical signs were observed by 3 weeks of age. Necropsy of birds revealed no significant gross lesions in the internal organs, including the brain. There was no significant bacterial growth in the brains. Microscopic examination of various sections of the brain revealed multifocal lymphocplasmacytic perivascular cuffs in the cerebellum and cerebral cortex. The brain samples were processed for detection and whole genome sequencing by next-generation sequencing. Three full-length polyprotein sequences (6405 nt) of AEV were assembled. All three sequences shared 99.9-100% nucleotide and 100% amino acid identities with each other. Only 77.7-78.5% of nucleotide and 90.3-92.5% of amino acid identities with AEV field strains and vaccine sequences were available in GenBank. This indicates that a new divergent variant of AEV is circulating in the field and causing AE outbreaks in the Midwest region.

Research Note: Pathogenetic characteristics of avian encephalomyelitis virus in Guangdong and Jiangxi Provinces, China

In recent years, the infection rate of avian encephalomyelitis virus (AEV) infection in chickens has risen significantly, seriously endangering the development of the chicken industry. In order to study the current epidemiological status of AEV in China as well as the genetic and evolutionary patterns of the virus, we conducted a survey and genomic analysis of chicken AEV. The results showed that 46.26% (136/294) of the tissue samples tested (n = 294) were positive for AEV, with the highest positivity rate of 62.24% (61/98) among tissue samples from chickens aged 13 to 18 wk. The complete genomes of 2 representative AEV strains were determined, and the VP1 evolutionary tree results revealed that the 2 representative strains belonged to a novel AEV strain. Multiple alignment analysis showed that the ORF1 genes of the 2 representative strains differed by 82.3 to 99.9% at the amino acid level compared with the reference AEV strain, and the mutations at the key amino acid loci of VP2 and VP3 were the same as those in the chick embryo-adapted strain. The analysis makes up for the molecular epidemiological data and genetic variation of the 2 representative strains. The analysis makes up for the molecular epidemiological data and genetic variation of AEV and provides a basis for further understanding the spread of AEV in China.

Backyard poultry: exploring non-intensive production systems

The concept of backyard poultry historically encompassed "food-producing animals." Nevertheless, a recent shift in livestock production paradigms within developed countries is evident, as backyard poultry owners now raise their birds for purposes beyond self-consumption, raising animals in a familiar way, and fostering emotional bonds with them. Because backyard animals are frequently privately owned, and the resulting products are typically not marketed, very little information is available about the demographic profile of backyard owners and information on flocks' characteristics, husbandry, and welfare. Thus, this review aims to clarify the characteristics of backyard poultry, highlighting the prevalent infectious diseases and the zoonotic risk to which farmers are exposed. According to the FAO, there are different types of poultry production systems: intensive, sub-intensive, and extensive. The system conditions, requirements, and the resulting performance differ extensively due to the type of breed, feeding practices, prevalence of disease, prevention and control of diseases, flock management, and the interactions among all these factors. The presence and transmission of infectious diseases in avian species is a problem that affects both the animals themselves and public health. Bacterial (Escherichia coli, Salmonella, Campylobacter, and Mycoplasma), parasitic (helminths, louses, and mites), and viral (Avian influenza, Newcastle, Marek, Infectious Bronchitis, Gumboro, Infectious Laringotracheitis, and Fowlpox) are the most important pathogens involved in backyard poultry health. In addition, Avian influenza, Salmonella, Campylobacter, and E. coli, could be a risk for backyard farmers and/or backyard-derived products consumers. Thus, proper biosecurity implementation measures are mandatory to control them. While the principles and practices of on-farm biosecurity may be well-versed among commercial farmers, hobbyists, and backyard farmers might not be familiar with the necessary steps to protect their flocks from infectious diseases and curb their transmission. This sector represents the fourth category of poultry farming, characterized by the lowest biosecurity standards. Consequently, it is imperative to address the legal status of backyard poultry, educate owners about biosecurity measures, and promote proper veterinary care and disease control.

Questionnaire study suggests grave consequences of infectious laryngotracheitis, infectious coryza and mycoplasmosis in small chicken flocks

BACKGROUND

A growing number of people in western countries keep small chicken flocks. In Sweden, respiratory disease is a common necropsy finding in chickens from such flocks. A respiratory real-time polymerase chain reaction (PCR) panel was applied to detect infectious laryngotracheitis virus (ILTV), Avibacterium paragallinarum (A. paragallinarum) and Mycoplasma gallisepticum (M. gallisepticum) in chickens from small flocks which underwent necropsy in 2017-2019 and had respiratory lesions. Owners (N = 100) of PCR-positive flocks were invited to reply to a web-based questionnaire about husbandry, outbreak characteristics and management.

RESULTS

Response rate was 61.0%. The flocks were from 18 out of Sweden's 21 counties indicating that respiratory infections in small chicken flocks are geographically widespread in Sweden. Among participating flocks, 77.0% were coinfected by 2-3 pathogens; 91.8% tested positive for A. paragallinarum, 57.4% for M. gallisepticum and 50.8% for ILTV. Larger flock size and mixed-species flock structure were associated with PCR detection of M. gallisepticum (P = 0.00 and P = 0.02, respectively). Up to 50% mortality was reported by 63.9% of respondents. Euthanasia of some chickens was carried out in 86.9% of the flocks as a result of the outbreaks. Full clinical recovery was reported by 39.3% of owners suggesting chronic infection is a major challenge in infected flocks. Live birds had been introduced in many flocks prior to outbreaks, which suggested these as an important source of infection. Following the outbreaks, 36.1% replaced their flocks with new birds and 9.8% ceased keeping chickens.

CONCLUSIONS

This study highlights the severity of respiratory outbreaks in small non-commercial chicken flocks and points to the need for more research and veterinary assistance to prevent and manage respiratory infections in small chicken flocks.

Progress in research on the molecular biological detection techniques of avian encephalomyelitis

Avian encephalomyelitis (AE) is a highly infectious disease caused by the avian encephalomyelitis virus (AEV), which primarily affects the central nervous system of 1- to 4-week-old chicks and causes significant economic losses in the worldwide poultry industry. Despite heavy dependency on vaccine immunization, AEV has persisted on farms for extended periods, which increases its virulence and makes quick and accurate detection crucial to preventing and controlling the disease. Classical diagnostic methods have been unable to meet the current requirements for rapid diagnosis of AE cases. To address this issue, this paper reviews the etiological and molecular biological detection techniques of AE, and it seeks to provide a reference for future research and to establish differential diagnostic techniques for AE epidemiological investigation, identification of epidemic strains, and early diagnosis of clinical cases. Through improving our understanding of AE, we can better combat the disease and protect the global poultry industry.

Serological Evidence of Infectious Laryngotracheitis Infection and Associated Risk Factors in Chickens in Northwestern Ethiopia

Infectious laryngotracheitis (ILT) is a disease of high economic consequence to the poultry sector. Gallid herpesvirus 1 (GaHV-1), a.k.a infectious laryngotracheitis virus (ILTV), under the genus Iltovirus, and the family Herpesviridae, is the agent responsible for the disease. Despite the clinical signs on the field suggestive of ILT, it has long been considered nonexistent and a disease of no concern in Ethiopia. A cross-sectional study was conducted from November 2020 to June 2021 in three selected zones of the Amhara region (Central Gondar, South Gondar, and West Gojjam zones), Ethiopia, with the objective of estimating the seroprevalence of ILTV in chickens and identifying and quantifying associated risk factors. A total of 768 serum samples were collected using multistage cluster sampling and assayed for anti-ILTV antibodies using indirect ELISA. A questionnaire survey was used to identify the potential risk factors. Of the 768 samples, 454 (59.1%, 95% CI: 0.56–0.63) tested positive for anti-ILTV antibodies. Mixed-effect logistic regression analysis of potential risk factors showed that local breeds of chicken were less likely to be seropositive than exotic breeds (OR: 0.38, 95% CI: 0.24–0.61). In addition, factors such as using local feed source (OR: 6.53, 95% CI: 1.77–24.04), rearing chickens extensively (OR: 1.97, 95% CI: 0.78–5.02), mixing of different batches of chicken (OR: 14.51, 95% CI: 3.35–62.77), careless disposal of litter (OR: 1.62, 95% CI: 0.49–4.37), lack of house disinfection (OR: 11.05, 95% CI: 4.09–47.95), lack of farm protective footwear and clothing (OR: 20.85, 95% CI: 5.40–80.45), and careless disposal of dead chicken bodies had all been associated with increased seropositivity to ILTV. Therefore, implementation of biosecurity measures is highly recommended to control and prevent the spread of ILTV. Furthermore, molecular confirmation and characterization of the virus from ILT suggestive cases should be considered to justify the use of ILT vaccines.

A Cross-Sectional Seroepidemiological Study on Infectious Bursal Disease in Backyard Chickens in the Mymensingh District of Bangladesh

Infectious bursal disease (IBD) is a highly contagious disease that causes significant economic loss in chickens. A cross-sectional study was conducted in the Mymensingh district of Bangladesh to determine the seroprevalence of IBD virus (IBDV) antibodies in backyard chickens and their association with different epidemiological risk factors. A total of 460 serum samples were randomly collected from backyard chickens that had not been previously vaccinated against IBDV. The collected sera were examined using an enzyme-linked immunosorbent assay (ELISA). Data on epidemiological risk factors were collected through face-to-face interviews with owners and subjected to both uni- and multivariable risk analyses to determine their association with IBDV infection. Using ELISA, the overall seroprevalence of IBDV antibodies in backyard chickens was 83.4% (95% confidence interval: 79.8%-86.6%), among which, a significantly higher seroprevalence was recorded in females (83.4%, 345/350), 4-6 weeks age group (95.3%, 244/256), and unhealthy (95.0%, 57/60) backyard chickens than those of males, other age groups, and healthy chickens, respectively. Furthermore, chickens reared in free-ranging housing systems (93.3%, 280/300) and poor-conditioned houses (98.0%, 147/150) showed a significantly higher seropositivity of IBDV antibodies than those reared in separated housing systems and other hygienic-conditioned houses, respectively. Moreover, compared with their counterparts, a higher but nonsignificant seroprevalence of IBDV antibodies was observed in backyard chickens that were selected from Fulbaria Upazila (88.8%; 80/90) and which were brought from the marketplace (85.7%, 60/70). A higher seropositivity of IBDV antibodies was shown to be statistically associated with various critical epidemiological risk factors, indicating that field strains of IBDV were exposed in backyard chickens and could be readily transferred horizontally. Proper prevention and control methods, villagers' awareness of IBD, and the rapid and widespread use of seroepidemiological investigations could help to reduce the spread of IBDV infection in backyard chickens.

Occurrence and Role of Selected RNA-Viruses as Potential Causative Agents of Watery Droppings in Pigeons

The diseases with watery droppings (diarrhea and/or polyuria) can be considered some of the most severe health problems in domestic pigeons of various ages. Although they do not always lead to bird death, they can contribute to poor weight gains and hindered development of young pigeons and, potentially, to poor racing results in sports birds. The gastrointestinal tract disorders of pigeons may be of various etiology, but some of the causative agents are viral infections. This review article provides information collected from scientific reports on RNA-viruses belonging to the Astroviridae, Picornaviridae, and Coronaviridae families; the Avulavirinae subfamily; and the Rotavirus genus that might be implicated in such health problems. It presents a brief characterization, and possible interspecies transmission of these viruses. We believe that this review article will help clinical signs of infection, isolation methods, occurrence in pigeons and poultry, systemize and summarize knowledge on pigeon enteropathogenic viruses and raise awareness of the importance of disease control in pigeons.

Molecular Epidemiology and Genotyping of Infectious Bronchitis Virus and Avian Metapneumovirus in Backyard and Commercial Chickens in Jimma Zone, Southwestern Ethiopia

Poultry production plays a relevant role in the Ethiopian economy and represents a source of poverty alleviation for several social classes. Infectious diseases can therefore significantly impact the economy and welfare. Despite infectious bronchitis virus (IBV) and avian metapneumovirus (aMPV) being present, the knowledge of their epidemiology and impact is extremely limited. In the present work, a cross-sectional study based on 500 tracheal swabs collected from 50 intensive and backyard unvaccinated flocks of the Jimma Zone was performed to investigate the circulation of these viruses and molecularly characterize them. IBV and aMPV presence was tested by molecular assays, and genotyping was carried out on positive samples. Accordingly, 6% (95% CI 2.06% to 16.22%) and 8% (95% CI 3.15% to 18.84%) of flocks tested IBV and aMPV positive, respectively. Particularly, IBV 793B (GI-13) strains were detected in backyard flocks only, and identical or closely related sequences (p-distance <2%) were detected in distantly spaced flocks, suggesting relevant viral circulation. On the contrary, both backyard and intensive flocks were affected by aMPV subtype B. Potential epidemiological links associated to the importation of parental birds from foreign countries could be established. These results highlight non-negligible circulation of these viruses, warranting further epidemiological studies and the evaluation of control measure implementation.

Phylogeny and evolution of infectious bursal disease virus circulating in Turkish broiler flocks

The emergence of new infectious bursal disease virus (IBDV) variants can threaten poultry health and production all over the world causing significant economic losses. Therefore, this study was performed to determine IBDV molecular epidemilogy, VP2 gene variation, and corresponding pathological lesions in IBDV infected chickens in Turkey. For this, 1855 bursa of Fabricius samples were collected from 371 vaccinated broiler flocks. Atrophia and haemorrhages were seen in the bursa Fabricius of very virulent IBDV (vvIBDV) infected chickens. Partial VP2 gene was sequenced and phylogenetic, recombination, and evolutionary analyses were performed. 1548 (83.5%) out of 1855 of bursa of Fabricius samples were IBDV positive and 1525 of those could be sequenced. The recombination analysis did not detect occurrence of any recombination event among the Turkish strains. Among 1525 sequenced samples, 1380 of them were found to be classical strains. Among 1380 classical strains, 1317 were similar to IBDV 2512, 11 to Faragher 52/70, 40 to 228 E, and 12 to Lukert strain. Out of 1525 reverse transcriptase ploymerase chain reaction positive samples, 144 of them were found to be similar to vvIBDV-VP2 gene reported to GenBank previously. The phylogenetic tree performed on a broad sequence dataset demonstrated grouping of vvIBDV Turkish strains in three different clusters, including sequences collected also from Iraq and Kuwait (Cluster 1), Indian (Cluster 2), and a distinct Turkish-only cluster (Cluster 3). The evolutionary rate estimation on branches/clades including Turkish strain mirrored the expected one for RNA viruses and no significant differences were found among different considered branches. In conclusion, results of this study indicate that vvIBDV strains similar to those circulating in various countries in the Middle East are present and undergoing evolution in chickens from Turkish broiler flocks. This point needs to be taken into account in planning adequate control strategies.

A two-year prospective study of small poultry flocks in Ontario, Canada, part 2: causes of morbidity and mortality

Non-commercial poultry flocks (referred to as "small flocks") have become increasingly popular in Canada. Despite this popularity, little is known about the main causes of morbidity and mortality (health status) in these flocks. We assessed the baseline prevalence of infectious and non-infectious diseases among Ontario's small poultry flocks by conducting a prospective surveillance study over a 2-y period. With the owner's consent, for each bird ( n = 245) submitted to the Animal Health Laboratory, we performed a postmortem examination, including ancillary tests to reach a diagnosis. Infectious diseases were the most common primary cause of clinical signs or death (62%), with multifactorial respiratory diseases (21%) and Marek's disease (11%) being most frequent. Multifactorial respiratory diseases were commonly caused by coinfection with bacteria (e.g., Mycoplasma gallisepticum and M. synoviae, Escherichia coli, Avibacterium spp.) and viruses, such as infectious bronchitis and infectious laryngotracheitis viruses. No federally reportable diseases were diagnosed. The health status of small flocks in Ontario has not been reported previously, to our knowledge, and the data presented herein will produce helpful baseline information for the development of technology transfer material directed to owners and veterinarians, which will ultimately aid in the control of diseases among these flocks.

A two-year prospective study of small poultry flocks in Ontario, Canada, part 1: prevalence of viral and bacterial pathogens

In Ontario, within the past few years, there has been a marked increase in the number of non-commercial poultry flocks (referred to as "small flocks"). Small poultry flocks may act as a reservoir of avian and zoonotic pathogens, given the flocks' limited access to veterinary services, inadequate biosecurity practices, and increased risk of contact with wild birds. Despite these potential risks, there is a scarcity of data concerning the prevalence of poultry and zoonotic pathogens among these flocks. To assess the baseline prevalence of bacterial and viral infectious pathogens, prospective surveillance of small flock postmortem submissions to the Animal Health Laboratory was conducted over a 2-y period. With the owner's consent, a postmortem examination and pre-set tests for infectious agents were conducted. A total of 160 submissions, mainly chickens (84%), were received. Among bacterial pathogens, Brachyspira spp., Mycoplasma synoviae, Campylobacter spp., Mycoplasma gallisepticum, and Salmonella spp. were detected in 37%, 36%, 35%, 23%, and 3% of tested submissions, respectively. Among viral pathogens, infectious bronchitis virus, fowl adenovirus, infectious laryngotracheitis virus, avian reovirus, and infectious bursal disease virus were detected in 39%, 35%, 15%, 4%, and 1% of submissions, respectively. We detected non-virulent avian avulavirus 1 from two chickens in a single submission, and low-pathogenic H10N8 influenza A virus from a single turkey submission. Our study provides baseline prevalence of viral and bacterial pathogens circulating in Ontario small flocks and may help animal and human health professionals to educate small flock owners about disease prevention.

Role of Backyard Flocks in Transmission Dynamics of Highly Pathogenic Avian Influenza A(H5N8) Clade 2.3.4.4, France, 2016-2017

Highly pathogenic avian influenza A(H5N8) clade 2.3.4.4 spread in France during 2016–2017. We assessed the biosecurity and avian influenza virus infection status of 70 backyard flocks near H5N8-infected commercial farms. One flock was seropositive for clade 2.3.4.4. Backyard flocks linked to commercial farms had elevated risk for H5 infection.

Chicken anaemia virus enhances and prolongs subsequent avian influenza (H9N2) and infectious bronchitis viral infections

Immunosuppressive viral diseases have a great economic importance in the poultry industry due to the increased susceptibility to secondary infections. Chicken anaemia virus (CAV) is one of the major immunosuppressive diseases in chickens. In addition, low pathogenic avian influenza (LPAI) of subtype H9N2 and infectious bronchitis (IB) viruses are among the most frequently reported respiratory viral diseases in poultry worldwide. In the present study, specific pathogen free chickens were used to understand the impact of CAV on secondary infection with LPAI-H9N2 or IB viruses. Clinical outcomes, viral shedding dynamics, and cytokine levels wereassessed. The results exhibit that chickens previously infected with CAV produceconsiderablyhigher titresof LPAI-H9N2 or IB viruses in the oropharyngeal swabs (P < 0.05), tracheas and kidneys. In addition, the immunologic effect of CAV provokedthe development of clinical signs of LPAI-H9N2 and IB virus infections. Moreover, results suggested that pre-infection with CAV directly correlated with elevated levels of IL-6 and IFNγ. These findings underline the importance of CAV pre-infection on LPAI-H9N2 or IB infection in chickens, and indicate that co-circulation of CAV can contribute to the spread and evolution of LPAI H9N2 and IB viruses.

Circulation of very virulent avian infectious bursal disease virus in Finland

In the spring of 2014 infectious bursal disease (IBD) was confirmed in a Finnish layer flock exhibiting clinical signs and increased mortality. Organ and blood samples were sent for diagnosis to the Finnish Food Safety Authority Evira. IBD virus (IBDV) was detected in RT-PCR studies. Altogether hens from six layer farms associated with increased mortality (7-10%, worst case 30%) were diagnosed with IBD during 2014. Antibodies were also detected with IBD-ELISA tests in hens on two farms. Phylogenetic analysis showed that the causative agent of the 2014 IBD outbreak was a non-reassortant very virulent type IBDV. The representative virus strains from previous IBD outbreaks in 1978, 1987 and 1993 were also included in the analysis. The strains isolated in 2014 and 1993 were very similar indicating circulation of a very virulent IBDV for over 20 years in the country. In spite of the comprehensive phylogenetic analysis, the definitive origin of the viruses from 2014 and previous outbreaks remains unclear.

Detection of Antibodies to Seven Priority Pathogens in Backyard Poultry in Trinidad, West Indies

Backyard poultry farms in Trinidad and Tobago (T&amp;T) play a vital role in providing food and income for rural communities. There is currently no information on the presence and circulation of pathogens in backyard poultry farms in T&amp;T, and little is known in relation to the potential risks of spread of these pathogens to the commercial poultry sector. In order to address this, serum samples were collected from 41 chickens on five backyard farms taken from selected locations in Trinidad. Samples were tested for antibodies to seven priority pathogens of poultry by enzyme-linked immunosorbent assay (ELISA). Antibodies were detected in 65% (CI 95%: 50-78%) of the sampled birds for Infectious bronchitis virus (IBV), 67.5% (CI 95%: 52-80%) for Infectious bursal disease virus (IBDV), 10% (CI 95%: 4-23%) for Newcastle disease virus (NDV), 0% (CI 95%: 0-0%) for Avian influenza virus (AIV), 0% (CI 95%: 0-0%) for West Nile virus (WNV), 31.7% (CI 95%: 20-47%) for Mycoplasm gallisepticum/synoviae and 0% (CI 95%: 0-0%) for Salmonella enterica serotype Enteritidis. These results reveal the presence and circulation of important pathogens of poultry in selected backyard farms in Trinidad. The results provide important information which should be taken into consideration when assessing the risks of pathogen transmission between commercial and backyard poultry farms, as well as between poultry and wild birds.