Avian Diseases最新文献

Despite the essential role of innate immunity in defining the outcome of viral infections, the roles played by different components of the avian innate immune system are poorly delineated. Here, we investigated the potential implication of avian toll-like receptor (TLR) 3 (TLR3) and melanoma differentiation-associated (MDA) gene 5 (MDA5) receptors of double-stranded RNA (dsRNA) in induction of the interferon pathway and avian orthoavulavirus 1 (AOAV-1) replication in chicken-origin DF-1 fibroblast cells. TLR3 and MDA5 knockout (KO) DF-1 cells were generated using our avian-specific CRISPR/Cas9 system and stimulated with a synthetic dsRNA ligand polyinosinic:polycytidylic acid [poly(I:C)] or infected with AOAV-1 (previously known as Newcastle disease virus). Poly(I:C) treatment in cell culture media resulted in significant upregulation of interferon (IFN)α, IFNβ, and Mx1 gene expression in wild type (WT) DF-1 cells but not in TLR3-MDA5 double KO cells. Interestingly, poly(I:C) treatment induced rapid cell degeneration in WT and MDA5 KO cells, but not in TLR3 knockout or TRL3-MDA5 double knockout (DKO) cells, directly linking poly(I:C)-induced cell degeneration to TLR3-mediated host response. The double knockout cells supported significantly higher replication of AOAV-1 virus than did the WT cells. However, no correlation between the level of virus replication and type I IFN response was observed. Our study suggests that innate immune response is host- and pathogen specific, and further investigation is needed to understand the relevance of dsRNA receptor-mediated immune responses in viral replication and pathogenesis in avian species.

Clostridial dermatitis (CD), caused by Clostridium septicum and Clostridium perfringens, is an economically important emerging disease of turkeys characterized by sudden deaths and necrotic dermatitis. Immune responses in CD-affected commercial turkeys are poorly understood. In the present study, C. septicum was isolated from CD-affected commercial turkeys during a recent outbreak, and the tissues (skin, muscle, and spleen) were collected and analyzed for immune gene expression, along with samples from clinically healthy birds. The results showed that CD-affected turkeys had significantly higher levels of IL-1β, IL-6, IFNγ, and iNOS transcripts in the skin, muscle, and spleen tissues compared to healthy birds. Affected turkeys also had a significantly elevated transcription of toll-like receptor (TLR21) gene in the skin and spleen tissues, suggesting a role for this receptor in the immune recognition. The expression of IL-4 and IL-13 genes in the spleen and muscle was also significantly higher in the affected birds. Additional birds from the same affected and healthy farms examined for serology revealed that the CD-affected turkeys had significantly higher levels of serum IgM and IgY antibodies. Furthermore, in vitro stimulation of MQ-NCSU macrophages with C. septicum led to a significant transcriptional upregulation of IL-1β and IFNγ genes, while the IL-10 gene expression was downregulated. The surface expression of MHC-II protein and cellular production of nitric oxide were also significantly increased in the C. septicum-stimulated macrophages, indicating cellular activation. Collectively, our findings suggest that the host responses in CD-affected turkeys involve a robust inflammatory response as well as a response mediated by IL4/IL-13 cytokines that may aid in antibody-mediated immunity.

A flock of 50,000 28-day-old broiler breeder chickens experienced an elevated mortality event. Chickens from that flock, five pullets and six cockerels, were submitted for diagnostic investigation. Necropsy revealed bacterial septicemia with fibrinous polyserositis in the majority of the birds while two cockerels had coccidial typhlitis. Because sulfadimethoxine was not available at the time, sulfaquinoxaline (SQ) was prescribed at label dosage with water treatment for 2 days, followed by 3 days of no medication, followed by 2 days of medication. The mortality rose dramatically 9 days after the last treatment. Lesions at that time consisted of skin discoloration, subcutaneous petechiation, and enlarged pale kidneys. Mortality remained elevated for 14 days. Analysis of blood, kidney, and liver revealed elevated levels of SQ. Recalculation of dosage, water consumption, amount of drug administered, remaining drug stock, and concentration of supplied SQ were analyzed and determined to be as predicted.

The U.S. Department of Agriculture Avian Disease and Oncology Laboratory currently relies on live birds of specific genetic backgrounds for producing chicken-embryo fibroblasts that are used for the diagnosis and subtyping of field isolates associated with avian leukosis virus (ALV) outbreaks. As an alternative to maintaining live animals for this purpose, we are currently developing cell lines capable of achieving the same result by ablation of the entry receptors utilized by ALV strains. We used CRISPR-Cas9 on the cell fibroblast-derived cell line DF-1 to disrupt the tva gene, which encodes the receptor required for binding and entry of ALV-A into cells. We ultimately identified seven DF-1 clones that had biallelic and homozygous indels at the Cas9 target site, exon 2 of tva. When tested in vitro for their ability to host ALV-A, the five clones that had frameshift mutations that disrupted the Tva protein were unable to support ALV-A replication. This result clearly demonstrates that modified cell lines can be used as part of a battery of tests to determine ALV subtype for isolate characterization, thus eliminating the need for live birds.

Wild-caught Eurasian tree sparrows (Passer montanus) were experimentally inoculated with genotype VII velogenic Newcastle disease virus (NDV) APMV1/chicken/Japan/Fukuoka-1/2004 to investigate the susceptibility and pathogenesis of infected sparrows. Intranasal inoculation of two groups with high or low doses of the virus resulted in the mortality of some birds in both groups on days 7-15 postinoculation. Neurologic signs, ruffled feathers, labored breathing, emaciation, diarrhea, depression, and ataxia were observed in a few birds that eventually succumbed to death. The inoculation of the higher viral load resulted in higher mortality and hemagglutination inhibition antibody detection rates. Tree sparrows that survived the 18-day observation period after inoculation exhibited no apparent clinical signs. Histologic lesions in dead birds were observed in the nasal mucosa, orbital ganglion, and central nervous system, accompanied by NDV antigens detected by immunohistochemistry. Viral inclusion bodies were rarely observed in the cytoplasm of neurons. NDV was isolated from the oral swab and brain of dead birds but not from other organs, including the lung, heart, muscle, colon, and liver. In another experimental group, tree sparrows were intranasally inoculated with the virus and then examined 1-3 days later to examine the early pathogenesis of the disease. Inoculated birds exhibited inflammation of the nasal mucosa with viral antigens, and virus was isolated from some oral swab samples on days 2 and 3 postinoculation. The results of the present study suggest that tree sparrows are susceptible to velogenic NDV, and the infection could be fatal, although some birds can exhibit asymptomatic or mild infection. The unique pathogenesis regarding the neurologic signs and viral neurotropism of velogenic NDV was characteristic in infected tree sparrows.

A sudden drop in egg production in commercial poultry flocks can be economically devastating, and rapid identification of the cause often requires a combined effort between the producer, veterinarian, and pathologist. In September 2019, a 35-wk-old commercial Pekin breeder duck flock in Indiana suffered a drop in egg production from 1700 to 1000 eggs daily (41.2% drop). Again, in September 2021, three Pekin breeder duck flocks aged 32, 58, and 62 wk from the same company suffered a similar drop in egg production, with a mild increase in weekly mortality of 1.0% to 2.5%. In 2019 and in 2021, birds from affected flocks were submitted to the Veterinary Diagnostic Laboratory at Michigan State University for postmortem examination. Common gross examination findings included flaccid, shrunken, or atrophied ova (all hens), pododermatitis, airsacculitis, hepatomegaly, splenomegaly, ascites, and pallor of the left ventricle. Histopathologic examination of cerebrum, cerebellum, and brainstem revealed mild lymphocytic perivascular cuffing, vasculitis, and gliosis, suggesting viral encephalitis. In the heart, there was mild multifocal cardiomyocyte necrosis, mineralization, and infiltration by lymphocytes and macrophages. PCR for Newcastle disease virus, avian influenza virus, eastern equine encephalitis virus, and West Nile virus (WNV) was performed. Brain and heart samples were positive for WNV by PCR, and WNV antigen was detected in the cerebellum by immunohistochemistry. This is the first report to associate WNV infection with a drop in egg production in waterfowl, which are known to be important reservoir species for WNV and, as such, are generally asymptomatic.

Duck Tembusu virus (DTMUV) is a pathogenic flavivirus that causes a substantial drop in egg production and severe neurological disorders in domestic waterfowl. Self-assembled ferritin nanoparticles with E protein domains I and II (EDI-II) of DTMUV (EDI-II-RFNp) were prepared, and its morphology was observed. Two independent experiments were conducted. First, Cherry Valley ducks aged 14 days were vaccinated with EDI-II-RFNp, EDI-II, and phosphate buffered solution (PBS, pH 7.4), and special and virus neutralization (VN) antibodies, interleukin 4 (IL-4) and interferon gamma (IFN-γ) in serum, and lymphocyte proliferation were detected. Second, the vaccinated ducks with EDI-II-RFNp, EDI-II, and PBS were injected with virulent DTMUV, clinical signs at 7 days postinfection (dpi) were observed, and mRNA levels of DTMUV in the lungs, liver, and brain at 7 and 14 dpi were detected. The results showed near-spherical nanoparticles EDI-II-RFNp with a 16.46 ± 4.70 nm diameters. The levels of specific and VN antibodies, IL-4 and IFN-γ, and lymphocyte proliferation in the EDI-II-RFNp group were significantly higher than those in the EDI-II and PBS groups. In the DTMUV challenge test, clinical signs and mRNA levels in tissue were used to evaluate protection of EDI-II-RFNp. EDI-II-RFNp-vaccinated ducks showed milder clinical signs and lower levels of DTMUV RNA in the lungs, liver, and brain. These results indicate that EDI-II-RFNp effectively protects ducks against the DTMUV challenge and could be a vaccine candidate to provide an effective and safe method for preventing and controlling DTMUV infection.

Ever since 1994, when the bacterial pathogen Mycoplasma gallisepticum jumped from poultry to wild birds, it has been assumed that the primary host species of this pathogen in wild North American birds was the house finch (Haemorhous mexicanus), in which disease prevalence was higher than in any other bird species. Here we tested two hypotheses to explain a recent increase in disease prevalence in purple finches (Haemorhous purpureus) around Ithaca, New York. Hypothesis 1 is that, as M. gallisepticum evolved and became more virulent, it has also become better adapted to other finches. If this is correct, early isolates of M. gallisepticum should cause less-severe eye lesions in purple finches than in house finches, while more-recent isolates should cause eye lesions of similar severity in the two species. Hypothesis 2 is that, as house finch abundance declined following the M. gallisepticum epidemic, purple finches around Ithaca increased in abundance relative to house finches and purple finches are thus more frequently exposed to M. gallisepticum-infected house finches. This would then lead to an increase in M. gallisepticum prevalence in purple finches. Following an experimental infection with an early and a more-recent M. gallisepticum isolate, eye lesions in purple finches were more severe than in house finches. This did not a support Hypothesis 1; similarly, an analysis of Project Feeder Watch data collected around Ithaca did not show differences in changes in purple and house finches' abundance since 2006, a result which does not support Hypothesis 2. We conclude that purple finch populations will, unlike those of house finches, not suffer a severe decline because of a M. gallisepticum epidemic.

An outbreak of food poisoning in New South Wales (NSW) Australia in 2018, caused by Salmonella enterica serovar Enteritidis phage type 12 (PT12), was traced to eggs consumed from a NSW layer flock. This was the first report of Salmonella Enteritidis infection in NSW layer flocks, despite ongoing environmental monitoring. Clinical signs and mortalities were minimal in most flocks, although seroconversion and infection were demonstrated in some flocks. An oral dose-response challenge study with Salmonella Enteritidis PT12 was undertaken in commercial point-of-lay hens. Cloacal swabs collected at 3, 7, 10, and 14 days postinoculation and caeca, liver, spleen, ovary, magnum, and isthmus tissues collected at necropsy at either 7 or 14 days were processed for Salmonella isolation (AS 5013.10-2009 from ISO6579:2002). Histopathology was performed on the above tissues, as well as lung, pancreas, kidney, heart, and additional intestinal and reproductive tract tissues. Salmonella Enteritidis was consistently detected in cloacal swabs between 7 and 14 days postchallenge. The Salmonella Enteritidis PT12 isolate successfully colonized the gastrointestinal tract, liver, and spleen of all hens orally challenged with 10⁷, 10⁸, and 10⁹ Salmonella Enteritidis, and less consistently colonized their reproductive tracts. On histopathology, mild lymphoid hyperplasia in the liver and spleen, along with hepatitis, typhlitis, serositis, and salpingitis, was observed at 7 and 14 days postchallenge, with a greater proportion of affected birds in the two higher dose groups. Diarrhea and culture of Salmonella Enteritidis from heart blood were not detected in challenged layers. The NSW isolate of Salmonella Enteritidis PT12 was able to invade and colonize the birds' reproductive tracts as well as a wide range of other tissues, indicating the potential for these naive commercial hens to contaminate their eggs.