Analysis of Emerging Variants of Turkey Reovirus using Machine Learning.

Avian reoviruses continue to cause disease in turkeys with varied pathogenicity and tissue tropism. Turkey enteric reovirus has been identified as a causative agent of enteritis or inapparent infections in turkeys. The new emerging variants of turkey reovirus, tentatively named turkey arthritis reovirus (TARV) and turkey hepatitis reovirus (THRV), are linked to tenosynovitis/arthritis and hepatitis, respectively. Turkey arthritis and hepatitis reoviruses are causing significant economic losses to the turkey industry. These infections can lead to poor weight gain, uneven growth, poor feed conversion, increased morbidity and mortality and reduced marketability of commercial turkeys. To combat these issues, detecting and classifying the types of reoviruses in turkey populations is essential. This research aims to employ clustering methods, specifically K-means and Hierarchical clustering, to differentiate three types of turkey reoviruses and identify novel emerging variants. Additionally, it focuses on classifying variants of turkey reoviruses by leveraging various machine learning algorithms such as Support Vector Machines, Naive Bayes, Random Forest, Decision Tree, and deep learning algorithms, including convolutional neural networks (CNNs). The experiments use real turkey reovirus sequence data, allowing for robust analysis and evaluation of the proposed methods. The results indicate that machine learning methods achieve an average accuracy of 92%, F1-Macro of 93% and F1-Weighted of 92% scores in classifying reovirus types. In contrast, the CNN model demonstrates an average accuracy of 85%, F1-Macro of 71% and F1-Weighted of 84% scores in the same classification task. The superior performance of the machine learning classifiers provides valuable insights into reovirus evolution and mutation, aiding in detecting emerging variants of pathogenic TARVs and THRVs.

Embolic necrosuppurative pneumonia in domestic cats induced by a novel Neisseria species.

Three cats, aged 2 to 11 years, presented to the University of Minnesota Veterinary Diagnostic Laboratory over a 3-year period following euthanasia or death due to respiratory distress. Thoracic radiographs revealed nodular, soft tissue opacities throughout the lung fields in all cases. On postmortem examination, approximately 60% to 80% of the lung parenchyma were expanded by multifocal to coalescing, well-demarcated, beige, semi-firm nodules. Histologically, large numbers of neutrophils, fewer macrophages, fibrin, and cellular and karyorrhectic debris effaced the pulmonary parenchyma. The inflammatory foci contained aggregates of gram-negative cocci. 16s rRNA Sanger sequencing and whole-genome sequencing identified the bacteria isolated from the lung of all cats under aerobic conditions as a novel Neisseria spp. Based on whole-genome sequence analysis, all 3 sequences shared 92.71% and 92.67% average nucleotide identity with closely related Neisseria animaloris NZ LR134440T and Neisseria animaloris GCA 002108605T, respectively. The in silico DNA-DNA hybridization identity compared to our isolates was 46.6% and 33.8% with strain DSM Neisseria zoodegmatis 21642 and strain DSM 21643, respectively. All 3 sequences have less than 95% average nucleotide identity and less than 70% DNA-DNA hybridization identity, suggesting that the 3 isolates are a novel species of the genus Neisseria. Infection with Neisseria spp. induces an embolic pneumonia in cats that radiographically and pathologically resembles a metastatic neoplastic process and should be considered among the etiologic differential diagnoses in cases of infectious pulmonary disease with a disseminated, nodular lung pattern.

Disease ecology and host range of Cyprinid herpesvirus 3 (CyHV-3) in CyHV-3 endemic lakes of North America.

Cyprinid herpesvirus-3 (CyHV-3) is an important pathogen of common carp (Cyprinus carpio, carp) causing significant economic and ecological impacts worldwide. The recent emergence of CyHV-3 in the Upper Midwest region of the United States has raised questions related to the disease ecology and host specificity of CyHV-3 in wild carp populations. To determine the prevalence of CyHV-3 in wild populations of fishes in Minnesota, we surveyed five lakes in 2019 in which the virus was known to have caused mass mortality events in carp from 2017 to 2018. A total of 28 species (n = 756 total fish) of native fishes and 730 carp were screened for the presence of CyHV-3 DNA using specific qPCR. None of the native fish tissues tested positive for CyHV-3 although the prevalence of CyHV-3 in carp was 10%-50% in the five lakes. A single lake (Lake Elysian) with a 50% DNA detection rate and evidence of ongoing transmission and CyHV-3-associated mortality was surveyed again in 2020 from April to September. During this period, none of the tissues from 24 species (n = 607 total fish) tested positive for CyHV-3 though CyHV-3 DNA and mRNA (indicating viral replication) was detected in carp tissues during the sampling period. CyHV-3 DNA was detected most often in brain samples without evidence of replication, potentially indicating that brain tissue is a site for CyHV-3 latency. Paired qPCR and ELISA testing for Lake Elysian in 2019-2020 identified young carp (especially males) to be the primary group impacted by CyHV-3-associated mortality and acute infections, but with no positive detections in juvenile carp. Seroprevalence of carp from Lake Elysian was 57% in 2019, 92% in April of 2020 and 97% in September 2020. These results further corroborate the host specificity of CyHV-3 to carp in mixed wild populations of fishes in Minnesota and provide additional insights into the ecological niche of CyHV-3 in shallow lake populations of carp in North America.

Infection and transmission dynamics of Turkey arthritis reovirus in different age Turkeys.

Turkey arthritis reovirus (TARV) has been established as a cause of lameness in meat type turkeys in the past decade. However, no information is available on the age susceptibility of TARV or its transmission dynamics. We conducted this study to determine the age at which turkey poults are susceptible to TARV infection and whether infected birds can horizontally transmit the virus to their non-infected pen mates (sentinels). Five groups of turkeys were orally inoculated with TARV (∼106 TCID50/ml) at 2, 7, 14, 21 and 28 days of age (DOA). Two days after each challenge, four uninfected sentinel turkeys of equal age were added to the virus-inoculated groups. At one- and two-weeks post infection, turkeys from each group, including two sentinels, were euthanized followed by necropsy. Inoculated birds in all age groups had TARV replication in the intestine and gastrocnemius tendon with no statistically significant variation at p < 0.5. Furthermore, the inoculated birds at different age groups showed consistently high gastrocnemius tendon histologic lesion scores while birds in the 28-days-old age group had numerically lower lesion scores at 14 days post inoculation (dpi). The sentinels, in turn, also showed virus replication in their intestines and tendons and histologic lesions in gastrocnemius tendons. The findings indicate that turkeys at the age of 28 days or less are susceptible to infection with TARV following oral challenge. It was also found that TARV-infected birds could transmit the infection to naïve sentinel turkeys of the same age.

Comparative pathogenesis of turkey reoviruses.

Turkey reoviruses have been implicated in multiple disease syndromes resulting in significant economic losses to the turkey industry. It has been known for decades that turkey enteric reovirus (TERV) is involved in poult enteritis complex, but turkey arthritis reovirus (TARV), the causative agent of tenosynovitis in turkeys, emerged in 2011. In 2019, we isolated reovirus from several cases of hepatitis in turkeys and tentatively named it turkey hepatitis reovirus (THRV). The comparative pathogenesis of these viruses, and correlation with their genetic make-up (if any), is not known. In this study, we inoculated nine groups of 1-week-old turkey poults with two THRV, five TARV and two TERV via oral route. A tenth group served as a negative control. A subset of birds from each group was euthanised at 3, 5, 7, 14, 21, and 28 days post-inoculation (dpi). Tissues were collected for histology and real-time RT-PCR. All nine viruses were found to be enterotropic; the virus gene copy number in the intestine reached a peak at 5 dpi followed by a sharp decline at 7 dpi. All viruses caused a significant decline in body weight gain of birds as compared to the negative control group. Both TARV and THRV strains replicated in tendons and produced histologic lesions consistent with tenosynovitis. Hepatic lesions were produced by THRV only and the virus was re-isolated from liver and spleen of inoculated birds fulfilling Koch's postulates. The results of this study should be helpful in facilitating diagnosis and designing future mitigation plans.

Characterization and Whole Genome Sequencing of Chromobacterium violaceum OUAT_2017: A Zoonotic Pathogen Found Fatal to a Wild Asiatic Elephant.

This study reports a rare fatal case of Chromobacterium violeceum OUAT_2017 strain infection in an Asiatic elephant calf in India. Necropsy revealed pus-filled nodules in liver, spleen, and lungs. Nutrient broth cultures of nodule content showed sediment of violet pigment whereas smooth, non-diffusible, violet-pigmented, homogeneous colonies appeared on nutrient agar. The organism was found to be non-haemolytic and resistant to 8 of the 24 antibiotics tested in vitro. Partial 16S rRNA gene sequence measuring 1410 bp revealed 97% homology with C. violeceum. The bacterial genome composed of 64.87% of G + C content with total size of 4,681,202 bp. The genome annotation has 42 genes responsible for multidrug antibiotic resistance with the presence of Aminoglycoside-modifying enzymes (AAC (6')) that targets streptomycin and spectinomycin. Our findings corroborated the lethal effect of C. violeceum in a new host (elephant) that enriched scientific information on epidemiological picture and whole genome sequencing as well. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-022-01047-4.

Influence of Environmental Stressors on the Microbiota of Zebra Mussels (Dreissena polymorpha).

Host-associated microbiota play a critical role in host fitness by providing nutrition, enhancing digestion capabilities, and by providing protection from pathogens. Here, we investigated the effects of two environmental stressors, temperature, and salinity, on the microbiota associated with zebra mussels (ZMs), a highly invasive bivalve in North America. To examine this in detail, lake-collected ZMs were acclimated to laboratory conditions, and subjected to temperature and salinity stress conditions. The impact of these stressors on the diversity, composition, and dynamics of ZM-associated microbiota were assessed by using amplicon- and shotgun-based sequencing, and qPCR-based approaches. Elevated temperature was found to be the primary driver of ZM mortality, although salinity alone also increased its likelihood. Stressor-induced ZM mortality, which ranged between 53 and 100%, was concomitant with significant increases in the relative abundance of several genera of putative opportunistic pathogens including Aeromonas. These genera were only present in low relative abundance in ZMs obtained from the control tank with 0% mortality. Shotgun sequencing and qPCR analyses indicated that the relative and absolute abundances of pathogenic Aeromonas species (particularly A. veronii) were significantly greater in temperature-induced dead ZMs. Taken together, our results show that environmental stress, especially elevated temperature (> 25 °C), is associated with the rapid mortality of ZMs as well as the proliferation of putative opportunistic bacterial pathogens.

Molecular and Biological Characterization of a Cervidpoxvirus Isolated From Moose with Necrotizing Dermatitis.

Cervidpoxvirus is one of the more recently designated genera within the subfamily Chordopoxvirinae, with Deerpox virus (DPV) as the only recognized species to date. In this study, the authors describe spontaneous disease and infection in the North American moose (Alces americanus) by a novel Cervidpoxvirus, here named Moosepox virus (MPV). Three 4-month-old moose calves developed a multifocal subacute-to-chronic, necrotizing, suppurative-to-granulomatous dermatitis that affected the face and the extremities. Ultrastructurally, all stages of MPV morphogenesis-that is, crescents, spherical immature particles, mature particles, and enveloped mature virus-were observed in skin tissue. In vitro infection with MPV confirmed that its morphogenesis was similar to that of the prototype vaccinia virus. The entire coding region, including 170 putative genes of this MPV, was sequenced and annotated. The sequence length was 164,258 bp with 98.5% nucleotide identity with DPV (strain W-1170-84) based on the whole genome. The genome of the study virus was distinct from that of the reference strain (W-1170-84) in certain genes, including the CD30-like protein (83.9% nucleotide, 81.6% amino acid), the endothelin precursor (73.2% nucleotide including some indels, 51.4% amino acid), and major histocompatibility class (MHC) class I-like protein (81.0% nucleotide, 68.2% amino acid). This study provides biological characterization of a new Cervidpoxvirus attained through in vivo and in vitro ultrastructural analyses. It also demonstrates the importance of whole-genome sequencing in the molecular characterization of poxviruses identified in taxonomically related hosts.

Koi herpesvirus and carp oedema virus: Infections and coinfections during mortality events of wild common carp in the United States.

Koi herpesvirus (KHV; cyprinid herpesvirus-3) and carp oedema virus (CEV) are important viruses of common and koi carp (Cyprinus carpio); however, the distribution of these viruses in wild common carp in North America is largely unknown. During the summers of 2017 and 2018, 27 mass mortalities of common carp were reported from four states in the USA (Minnesota, Iowa, Pennsylvania and Wisconsin), the majority of which were distributed across eight major watersheds in southern Minnesota. Samples from 22 of these mortality events and from five clinically healthy nearby carp populations were screened for KHV, CEV and SVCV using real-time polymerase chain reaction (qPCR). KHV was confirmed in 13 mortality events, CEV in two mortality events and coinfections of KHV/CEV in four mortality events. Nucleotide sequence analysis revealed that the KHV and CEV detected here are closely related to European lineages of these viruses. While molecular detection alone cannot conclusively link either virus with disease, the cases described here expand the known range of two important viruses. This is also the first reported detection of KHV and CEV coinfections in wild carp populations.

Detection and genetic characterization of bovine kobuvirus from calves in Egypt.

Kobuviruses are small non-enveloped RNA viruses that probably cause diarrhea in cattle and swine. Since its discovery in 2003, few studies have addressed bovine kobuvirus (BKoV; a species of Aichivirus B) infections. BKoV has been reported in Europe, Asia, and South America, suggesting a worldwide distribution. To investigate the presence of BKoV in Egypt, 36 fecal specimens from diarrheic calves in two different Egyptian provinces (Cairo and Sharkia) were screened by RT-PCR and 24 (66.7%) were found positive for BKoV. RNA from one of the positive samples (BKoV/Egy-1/KY407744) was subjected to next-generation sequencing to determine the complete BKoV genome sequence. When compared to the only recorded BKoV genome sequence (BKoV/U-1/AB084788), the studied strain showed 94 amino acid (aa) substitutions through its entire polyprotein (2463 aa), one nucleotide (nt) insertion and one nt deletion in the 2B gene and 4-nt deletions in the UTRs (2 each). Additionally, five VP1 and seven 3D sequences were obtained from other samples by using RT-PCR and Sanger sequencing. A discrepancy in the phylogenetic topography of VP1 and 3D was observed, where the Egyptian VP1 sequences were classified as a distinct cluster within the proposed lineage 1 (genotype A), which also contained strains from the UK, Brazil, and Japan. While, the 3D sequences from Cairo were related to those of Chinese strains unlike Sharkia ones that were more closer to Korean  strains. To the best of our knowledge, this is the first detection and genomic characterization of BKoV in Egypt or indeed Africa.

Taxonomy of the order Mononegavirales: update 2018.

In 2018, the order Mononegavirales was expanded by inclusion of 1 new genus and 12 novel species. This article presents the updated taxonomy of the order Mononegavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV) and summarizes additional taxonomic proposals that may affect the order in the near future.

Novel Avulaviruses in Penguins, Antarctica.

We identified 3 novel and distinct avulaviruses from Gentoo penguins sampled in Antarctica. We isolated these viruses and sequenced their complete genomes; serologic assays demonstrated that the viruses do not have cross-reactivity between them. Our findings suggest that these 3 new viruses represent members of 3 novel avulavirus species.

Genome characterization of Turkey Rotavirus G strains from the United States identifies potential recombination events with human Rotavirus B strains.

Rotavirus G (RVG) strains have been detected in a variety of avian species, but RVG genomes have been published from only a single pigeon and two chicken strains. Two turkey RVG strains were identified and characterized, one in a hatchery with no reported health issues and the other in a hatchery with high embryo/poult mortality. The two turkey RVG strains shared only an 85.3 % nucleotide sequence identity in the VP7 gene while the other genes possessed high nucleotide identity among them (96.3-99.9 %). Low nucleotide percentage identities (31.6-87.3 %) occurred among the pigeon and chicken RVG strains. Interestingly, potential recombination events were detected between our RVG strains and a human RVB strain, in the VP6 and NSP3 segments. The epidemiology of RVG in avian flocks and the pathogenicity of the two different RVG strains should be further investigated to understand the ecology and impact of RVG in commercial poultry flocks.

Molecular detection of enteric viruses from diarrheic calves in Egypt.

Neonatal calf diarrhea (NCD) is a major cause of morbidity, mortality and economic losses in the beef and dairy industries. This study was conducted to investigate the existence of enteric viruses in two Egyptian farms with a history of recurrent diarrhea. Fecal samples were collected from 25 diarrheic calves. RNA was extracted and tested by reverse transcription polymerase chain reaction (RT-PCR) for the presence of rotavirus, norovirus, astrovirus, torovirus, coronavirus and bovine viral diarrhea virus. Overall, 76 % (19/25) of samples tested positive for one or more viruses. Rota-, noro- and astroviruses were detected in 48 %, 24 % and 32 % of tested samples, respectively. About 37 % (7/19) of positive samples had two different viruses. One-month-old calves were the group most vulnerable to infections. Based on phylogenetic analysis, bovine rotaviruses were of genotypes G6 and G10, bovine noroviruses were in GIII.2, and bovine astroviruses were in the BAstV lineage 1. Astrovirus sequences showed a high level nucleotide sequence similarity with the Brazilian BAstV sequences available in GenBank. We believe this is the first report of bovine norovirus and bovine astrovirus circulating among calves in Egypt. Further epidemiological studies are recommended to investigate their presence on a wider scale, to predict their association with NCD, and to design appropriate diagnostic and control methods.

Genomic characterization of a novel calicivirus, FHMCV-2012, from baitfish in the USA.

During regulatory sampling of fathead minnows (Pimephales promelas), a novel calicivirus was isolated from homogenates of kidney and spleen inoculated into bluegill fry (BF-2) cells. Infected cell cultures exhibiting cytopathic effects were screened by PCR-based methods for selected fish viral pathogens. Illumina HiSeq next generation sequencing of the total RNA revealed a novel calicivirus genome that showed limited protein sequence similarity to known homologs in a BLASTp search. The complete genome of this fathead minnow calicivirus (FHMCV) is 6564 nt long, encoding a polyprotein of 2114 aa in length. The complete polyprotein shared only 21% identity with Atlantic salmon calicivirus,followed by 11% to 14% identity with mammalian caliciviruses. A molecular detection assay (RT-PCR) was designed from this sequence for screening of field samples for FHMCV in the future. This virus likely represents a prototype species of a novel genus in the family Caliciviridae, tentatively named "Minovirus".

Co-circulation of paramyxo- and influenza viruses in pigeons in Egypt.

In recent years, avian influenza virus (AIV) and Newcastle disease virus (NDV) have caused large-scale outbreaks in many countries, including Egypt. The culling and vaccination strategies have failed to control both viruses in Egypt. In this study, we investigated the outbreaks of nervous manifestations and deaths in pigeons between 2013 and 2015. The H5N1 subtype of the highly pathogenic avian influenza virus and pigeon paramyxovirus-1, an antigenic variant of NDV, were found to be the cause; AIV and pigeon paramyxovirus-1 were isolated from 61.3% (19/31) and 67.8% (21/31) of tested pigeons, respectively. Co-infection with both viruses was detected in 51.6% of pigeons (16/31). The AIV sequences showed PQGEKRRKKR/GLF motif at the haemagglutinin gene cleavage site, which is typical of the highly pathogenic H5N1 subtype. The phylogenetic tree showed that the highly pathogenic avian influenza belonged to clade 2.2.1.2. The NDV sequences carried one of the three motifs, 112GKQGRL117, 112KRQKRF117 or 112RRQKRF117, at the fusion protein cleavage site and were classified as genotypes I, VI and II in NDV-class II, respectively. This indicated that different genotypes of NDV can circulate simultaneously among pigeons. Further analysis revealed the clustering of some sequences in sub-genotypes Ia and VIb.2. To the best of our knowledge, these sub-genotypes have not been previously reported from pigeons in Egypt. Our results should serve as a base for future studies on both viruses in Egypt.

Detection and molecular characterization of a novel piscine-myocarditis-like virus from baitfish in the USA.

During a survey of apparently healthy baitfish from the state of Minnesota, a novel piscine-myocarditis-like virus (PMCLV) was detected in golden shiners (Notemigonus crysoleucas). The nearly complete genome sequence is 5819 nt long, including a partial 5' untranslated region (UTR) of 100 nt. The sequence is divided into three ORFs: the complete ORF1 and ORF2, encoding proteins of 818 and 831 amino acids, respectively, and a partial ORF3 encoding 248 amino acids of the corresponding protein. This novel virus sequence was most closely related to piscine myocarditis virus (PMCV), with a 49.0 % and 58.2 % amino acid identity in the ORF1 (YP005481249)- and ORF2 (YP004581250)-encoded proteins, respectively. Six of 56 retail outlets (e.g., bait shops) were positive during the 2014-2015 survey, indicating a 10.7 % prevalence of the novel virus in this population of golden shiners. Currently, there is no disease that is known to be associated with this virus.

Molecular detection of a novel totivirus from golden shiner (Notemigonus crysoleucas) baitfish in the USA.

During regulatory and routine surveillance sampling of apparently healthy baitfish from the state of Minnesota, a novel totivirus (tentatively named "golden shiner totivirus", GSTV) was detected in a homogenate of kidney and spleen of golden shiner (Notemigonus crysoleucas). The nearly complete genome is 7788 nt long with a complete 5' untranslated region (UTR) of 135 nt (1-135 nt position), complete open reading frames (ORFs) and a partial 3' UTR of 54 nt (7734-7788). The sequence is comprised of two ORFs (ORF1 and ORF2). The larger ORF1 encodes a 1659-aa polypeptide in frame +1 from nt position 136 to 5115 (4980 nt) with a start codon at position 136-138 and a stop codon at position 5113-5115. The ORF1 is 54 aa longer than the 1605-aa ORF1-encoded protein of a reference strain of infectious myonecrosis virus (IMNV), ID-EJ-12-1(AIC34743.1). The predicted ORF1 and ORF2 fusion protein sequence was NFQDGG. Hence, an overlapping region of 99 nt was observed, which is shorter than the 172-nt and 199-nt overlapping regions in Armigeres subalbatus totivirus (AsTV) and IMNV, respectively. GSTV formed a separate lineage based on phylogenetic analysis of ORF1-encoded major capsid protein (MCP) and ORF2-encoded RNA-dependent RNA polymerase (RdRp) sequences. Based on ORF1 MCP sequence analysis, GSTV was most closely related to IMNV, with maximum aa sequence identity of 26.42-27.86 %, followed by 26.59, 22.94 and 21.75 % for Drosophila totivirus (DTV), AsTV and Omono River virus (OMRV), respectively. Similar to ORF1, the ORF2 (RdRp) of GSTV formed a separate clade with maximum identity of 38.10 % and 38.50 % to IMNV and DTV, respectively. The virus identified here differs enough from its closest relative that it may represent a new genus in the family Totiviridae. The disease-causing potential and management impact of this novel virus is unknown at this time.

Detection and molecular characterization of astroviruses in turkeys.

This study was conducted to determine the prevalence and molecular characteristics of turkey astrovirus 1 (TAstV-1) and avian nephritis virus (ANV) in turkeys with light turkey syndrome (LTS), which is characterized by lower body weight in market-age turkeys than their standard breed character. We collected pools of fecal samples from four LTS and two non-LTS turkey flocks in Minnesota at 2, 3, 5 and 8 weeks of age. Of the 80 LTS pools tested, 16 (20.0 %) and 11 (13.8 %) were positive for TAstV-1 and ANV, respectively. For non-LTS flocks, these numbers were 8 (20.0 %) and 5 (12.5 %), respectively. The maximum number of birds was positive at five weeks of age. We also tested 130 fecal samples of poult enteritis syndrome (PES) cases submitted to the Minnesota Veterinary Diagnostic Laboratory and found 19 and 11 positive for TAstV-1 and ANV, respectively. RdRp gene sequences were determined for a total of 29 TAstV-1 and 22 ANV samples. Phylogenetic analysis of the RdRp gene revealed 92-100 % and 88-100 % nucleotide sequence identity among TAstV-1 and ANV sequences, respectively. A large number of nucleotide and amino acid substitutions were observed in LTS and PES flocks than in non-LTS flocks. One of the PES sequences grouped with ANV-like sequences detected in chickens, indicating that regular screening of birds should be continued. Further, complete genome analysis should be conducted to determine whether this virus is a novel divergent strain or a recombinant of chicken and turkey ANV-like viruses. The detection of TAstV-1 and ANV in a considerable number of non-LTS cases emphasizes the need for further studies on the transmission pattern and pathogenesis of these viruses to determine their role as pathogens of turkeys.

Experimentally induced lameness in turkeys inoculated with a newly emergent turkey reovirus.

Newly emergent turkey arthritis reoviruses (TARVs) have been isolated from cases of lameness in male turkeys over 10 weeks of age. In a previous study, experimental inoculation of TARV in one-week-old turkey poults produced lymphocytic tenosynovitis at four weeks post inoculation but without causing clinical lameness. This study was undertaken to determine if TARV infection at an early age can lead to clinical lameness in birds as they age. One-week-old male turkeys were inoculated orally with a TARV (strain TARV-O'Neil) and monitored for the development of gait defects until 16 weeks of age. At 4, 8, 12 and 16 weeks of age, a subset of birds was euthanized followed by the collection of gastrocnemius tendon, digital flexor tendon, and intestines for virus detection by rRT-PCR and for histologic inflammation scoring. Clinical lameness was first displayed in TARV-infected turkeys at 8 weeks of age and ruptured gastrocnemius tendons with progressive lameness were also seen at 12-16 weeks of age. The virus was detected in gastrocnemius tendon of 4- 8- and 12-week-old turkeys but not in 16-week-old turkeys. Histologic inflammation scores of tendons at each of the four time points were significantly higher in the virus-inoculated group than in the control group (p < 0.01). Lesions began as lymphocytic tenosynovitis with mild synoviocyte hyperplasia at four weeks of age and progressed to fibrosis as the birds aged. These results demonstrate the potential of TARV to infect young turkeys and to produce subclinical tenosynovitis that becomes clinically demonstrable as the turkeys age.