Urgent need of rapid tests for SARS CoV-2 antigen detection: Evaluation of the SD-Biosensor antigen test for SARS-CoV-2.

At the time of writing, FIND has listed four CE-marked SARSCoV-2 antigen tests. We evaluated the recently CE-approved rapid POCT SD-Biosensor for SARS-CoV-2 nucleoprotein detection in nasopharyngeal secretions from 330 patients admitted to the Emergency Room for a suspect of COVID-19 and travelers returning home from high risk countries. Sensitivity, specificity, accuracy, negative and predictive values were consistent with the use of the test to mass-screening for SARS-CoV-2 surveillance.

A Nucleus-Targeting DNA Aptamer for Dead Cell Indication.

Dead cells always accompany with live cells in vivo and in cell culture. It is important to distinguish dead cells from live cells in various biological studies. Currently, the probes for dead cells are mainly nucleic acid-intercalators, most of which have low affinity and potential toxicity to live cells. In this work, we report a novel aptameric probe (Ch4-1) for the first time, which binds cell nuclei with high affinity (apparent Kd = 6.65 ± 3.40 nM). Ch4-1 was generated by Cell-SELEX process, it was identified to target nucleoproteins in cell nuclei. As an oligonucleotide, Ch4-1 cannot penetrate the integrated cell membrane; therefore, it only binds to dead cells rather than live cells. Compared with traditional DNA-targeting nuclear dyes, Ch4-1 possesses a high affinity to the nucleus, no toxicity to live cells, and can be easily labeled with different fluorescent dyes. It was demonstrated to serve as a probe for distinguishing dead cells from live cells in apoptosis assay, as well as for the nuclear staining of tissue sections.

Histopathological and Immunohistochemical Characteristics of Measles Exanthema: A Study of a Series of 13 Adult Cases and Review of the Literature.

Despite available vaccination, measles is one of the leading causes of death among young children in developing countries. In clinical practice, the spectrum of differential diagnoses of morbilliform exanthemas associated with fever is wide, and it can be hard to differentiate from other infectious eruptions, especially in adults or in atypical courses in immunocompromised patients. The goal of our study was to identify characteristic histomorphological and immunohistochemical patterns of measles exanthema through the study of 13 skin biopsy specimens obtained from 13 patients with this disease and a review of cases in the literature. Histopathological features of measles exanthema are quite distinctive and characterized by a combination of multinucleated keratinocytes, and individual and clustered necrotic keratinocytes in the epidermis with pronounced folliculosebaceous as well as acrosyringeal involvement. Immunohistochemical staining of skin biopsies with anti-measles virus (MeV) nucleoprotein and anti-MeV phosphoprotein can be of great value in confirming the diagnosis of measles. Both methods can serve as quick additional diagnostic tools for prompt implementation of quarantine measures and for providing medical assistance, even in patients in whom the clinician did not consider measles as a differential diagnosis of the rash due to the rarity of the disease in a putatively vaccinated community.

Simultaneous quantification of nucleoproteins and comparison of methyl green-pyronin Y and Feulgen staining in sections of oral squamous cell carcinoma, dysplastic lesions and normal mucosa.

A fundamental difference between normal cells and tumor cells is the proliferative activity of the nucleus and nucleolus, which increases progressively from normal to oral dysplastic mucosa to oral squamous cell carcinoma (OSCC). This activity is evaluated routinely using hematoxylin and eosin (H & E) staining, but in some cases, inter-observer variability occurs among pathologists. We evaluated cellular proliferation by staining sections with the methyl green-pyronin Y procedure and the Feulgen reaction. We also compared the efficacy of methyl green-pyronin Y and Feulgen staining for studying nuclear and nucleolar features in oral dysplastic mucosa and in different grades of OSCC. Sections cut from formalin fixed, paraffin embedded blocks of five normal mucosa, 15 dysplastic mucosa, 10 well-differentiated OSCC, 10 moderately differentiated OSCC and five poorly differentiated OSCC cases were stained with Hematoxylin and Eosin, methyl green-pyronin Y and the Feulgen reaction. The mean diameters of the nuclei and number of nucleoli showed significant differences. A progressive increase in diameter of the nucleus and number of nucleoli was observed from normal mucosa through poorly differentiated OSCC. We observed that methyl green-pyronin Y stain is more useful than Feulgen and hematoxylin and eosin for simultaneous quantitative assessment of both RNA and DNA. The simplicity of this technique makes it a valuable tool even for daily routine examination.

Molecular epidemiology of rabies virus isolated of herbivores from Brazilian Amazon / Epidemiologia molecular de vírus da raiva isolados de herbívoros procedentes da Amazônia brasileira

Rabies virus samples (n = 17) A1 to A3 exhibit a similar composition and geographic distribution. Diverse composition of remaining groups of N and G gene is attributable to different sequences used in the alignments for each genomic region. Glycoprotein amino acid sequence showed molecular markers in sub-lineages A2, A3, A4 and A7. This information provides a better comprehension of molecular epidemiology of rabies, starting with the knowledge of viral lineages circulating in the Brazilian Amazon.

Amostras do vírus da raiva (n = 17) isoladas de bovinos (n = 11), equinos (n = 4) e bubalinos (n = 2) procedentes do Pará (n = 7), Tocantins (n = 6) e Rondônia (n = 4) foram submetidas à técnica de RT-PCR para amplificação parcial dos genes da Nucleoproteína (N) e Glicoproteína (G). As sequências nucleotídicas obtidas foram analisadas pelo método de reconstrução filogenética Neighbor-Joining com o modelo evolutivo Kimura 2-parâmetros. Todas as 17 amostras pertenceram ao cluster A, que se encontrou na linhagem associado com morcego hematófago Desmodus rotundus. A análise filogenética baseada nos genes N e G, sugere a presença de cinco sublinhagens (A1-A5) e sete sublinhagens (A1-A7), respectivamente. Quando se compara ambas as filogenias, as sublinhagens A1 até A3 mostram composição e distribuição geográfica concordante, já a diversidade observada na composição das sublinhagens restantes é atribuída ao uso de sequências de diferentes alinhamentos. A glicoproteína mostrou marcadores moleculares nas sublinhagens A2, A3, A4 e A7, o que fornece elementos para melhor compreensão da epidemiologia molecular da raiva das linhagens circulantes na Amazônia Brasileira.

Microsphere suspension array assays for detection and differentiation of Hendra and Nipah viruses.

Microsphere suspension array systems enable the simultaneous fluorescent identification of multiple separate nucleotide targets in a single reaction. We have utilized commercially available oligo-tagged microspheres (Luminex MagPlex-TAG) to construct and evaluate multiplexed assays for the detection and differentiation of Hendra virus (HeV) and Nipah virus (NiV). Both these agents are bat-borne zoonotic paramyxoviruses of increasing concern for veterinary and human health. Assays were developed targeting multiple sites within the nucleoprotein (N) and phosphoprotein (P) encoding genes. The relative specificities and sensitivities of the assays were determined using reference isolates of each virus type, samples from experimentally infected horses, and archival veterinary diagnostic submissions. Results were assessed in direct comparison with an established qPCR. The microsphere array assays achieved unequivocal differentiation of HeV and NiV and the sensitivity of HeV detection was comparable to qPCR, indicating high analytical and diagnostic specificity and sensitivity.

Raman spectroscopy of proteins and nucleoproteins.

A protein Raman spectrum comprises discrete bands representing vibrational modes of the peptide backbone and its side chains. The spectral positions, intensities, and polarizations of the Raman bands are sensitive to protein secondary, tertiary, and quaternary structures and to side-chain orientations and local environments. In favorable cases, the Raman spectrum serves as an empirical signature of protein three-dimensional structure, intramolecular dynamics, and intermolecular interactions. Quantitative analysis of Raman spectral series can be further boosted by advanced statistical approaches of factor analysis that allow fitting of specific theoretical models while reducing the amount of analyzed data. Here, the strengths of Raman spectroscopy are illustrated by considering recent applications from the authors' work that address (1) subunit folding and recognition in assembly of the icosahedral bacteriophages, (2) orientations of subunit main chains and side chains in native filamentous viruses, (3) roles of cysteine hydrogen bonding in the folding, assembly, and function of virus structural proteins, and (4) structural determinants of protein/DNA recognition in gene regulatory complexes. Conventional Raman and polarized Raman techniques are surveyed.

Influenza A viruses grow in human pancreatic cells and cause pancreatitis and diabetes in an animal model.

Influenza A viruses commonly cause pancreatitis in naturally and experimentally infected animals. In this study, we report the results of in vivo investigations carried out to establish whether influenza virus infection could cause metabolic disorders linked to pancreatic infection. In addition, in vitro tests in human pancreatic islets and in human pancreatic cell lines were performed to evaluate viral growth and cell damage. Infection of an avian model with two low-pathogenicity avian influenza isolates caused pancreatic damage resulting in hyperlipasemia in over 50% of subjects, which evolved into hyperglycemia and subsequently diabetes. Histopathology of the pancreas showed signs of an acute infection resulting in severe fibrosis and disruption of the structure of the organ. Influenza virus nucleoprotein was detected by immunohistochemistry (IHC) in the acinar tissue. Human seasonal H1N1 and H3N2 viruses and avian H7N1 and H7N3 influenza virus isolates were able to infect a selection of human pancreatic cell lines. Human viruses were also shown to be able to infect human pancreatic islets. In situ hybridization assays indicated that viral nucleoprotein could be detected in beta cells. The cytokine activation profile indicated a significant increase of MIG/CXCL9, IP-10/CXCL10, RANTES/CCL5, MIP1b/CCL4, Groa/CXCL1, interleukin 8 (IL-8)/CXCL8, tumor necrosis factor alpha (TNF-α), and IL-6. Our findings indicate that influenza virus infection may play a role as a causative agent of pancreatitis and diabetes in humans and other mammals.

Serological assays based on recombinant viral proteins for the diagnosis of arenavirus hemorrhagic fevers.

The family Arenaviridae, genus Arenavirus, consists of two phylogenetically independent groups: Old World (OW) and New World (NW) complexes. The Lassa and Lujo viruses in the OW complex and the Guanarito, Junin, Machupo, Sabia, and Chapare viruses in the NW complex cause viral hemorrhagic fever (VHF) in humans, leading to serious public health concerns. These viruses are also considered potential bioterrorism agents. Therefore, it is of great importance to detect these pathogens rapidly and specifically in order to minimize the risk and scale of arenavirus outbreaks. However, these arenaviruses are classified as BSL-4 pathogens, thus making it difficult to develop diagnostic techniques for these virus infections in institutes without BSL-4 facilities. To overcome these difficulties, antibody detection systems in the form of an enzyme-linked immunosorbent assay (ELISA) and an indirect immunofluorescence assay were developed using recombinant nucleoproteins (rNPs) derived from these viruses. Furthermore, several antigen-detection assays were developed. For example, novel monoclonal antibodies (mAbs) to the rNPs of Lassa and Junin viruses were generated. Sandwich antigen-capture (Ag-capture) ELISAs using these mAbs as capture antibodies were developed and confirmed to be sensitive and specific for detecting the respective arenavirus NPs. These rNP-based assays were proposed to be useful not only for an etiological diagnosis of VHFs, but also for seroepidemiological studies on VHFs. We recently developed arenavirus neutralization assays using vesicular stomatitis virus (VSV)-based pseudotypes bearing arenavirus recombinant glycoproteins. The goal of this article is to review the recent advances in developing laboratory diagnostic assays based on recombinant viral proteins for the diagnosis of VHFs and epidemiological studies on the VHFs caused by arenaviruses.

The characterization of monoclonal antibodies to human metapneumovirus and the detection of multiple forms of the virus nucleoprotein and phosphoprotein.

Little is known of the proteome of human metapneumovirus (HMPV). In this study a panel of monoclonal antibodies to the virus have been characterized and used to identify viral proteins present in infected cell lysates. Of thirteen anti-HMPV monoclonal antibodies four reacted with recombinant fusion glycoprotein and one with recombinant G glycoprotein by immunofuorescence but not in western blots suggesting that they recognize conformation dependent epitopes. The specificity of the remaining antibodies were determined by MALDI/TOF analysis of the proteins they immunoprecipitated from HMPV infected cell lysates and by western blotting. Five MAbs bound to the nucleoprotein and three to the phosphoprotein. In western blots of lysates of cells infected with low passage HMPV, the anti-nucleoprotein MAbs stained a single polypeptide corresponding in size to the full length nucleocapsid protein. On repeated passage of the virus in cell culture, however, a second, smaller band appeared which may result from internal initiation of translation within the nucleocapsid gene as described for avian metapneumovirus. Antibodies to the phosphoprotein, besides the full length form, also recognized multiple polypeptides in infected cell lysates, with patterns differing for the two subtypes A and B. The possibility that these too may derive by internal initiation of translation is discussed.

Detecção de núcleoproteína-RNA do vírus rábico em diversos órgãos fora do sistema nervoso central de morcegos hematófagos infectados naturalmente / Detection of rabies virus nucleoprotein-RNA in several organs outside the Central Nervous System in naturally-infected vampire bats

Rabies is a neurological disease, but the rabies virus spread to several organs outside the central nervous system (CNS). The rabies virus antigen or RNA has been identified from the salivary glands, the lungs, the kidneys, the heart and the liver. This work aimed to identify the presence of the rabies virus in non-neuronal organs from naturally-infected vampire bats and to study the rabies virus in the salivary glands of healthy vampire bats. Out of the five bats that were positive for rabies in the CNS, by fluorescent antibody test (FAT), viral isolation in N2A cells and reverse transcription - polymerase chain reaction (RT-PCR), 100 percent (5/5) were positive for rabies in samples of the tongue and the heart, 80 percent (4/5) in the kidneys, 40 percent (2/5) in samples of the salivary glands and the lungs, and 20 percent (1/5) in the liver by RT-PCR test. All the nine bats that were negative for rabies in the CNS, by FAT, viral isolation and RT-PCR were negative for rabies in the salivary glands by RT-PCR test. Possible consequences for rabies epidemiology and pathogenesis are discussed in this work.

A raiva é uma doença neurológica, mas o vírus da raiva se dispersa para diversos órgãos fora do sistema nervoso central (SNC). Antígeno ou RNA do vírus da raiva já foram detectados em vários órgãos, tais como glândula salivar, pulmão, rim, coração e fígado. O presente trabalho teve como objetivo identificar a presença do vírus da raiva em órgãos não neuronais de morcegos hematófagos infectados naturalmente, e pesquisar a presença do vírus na glândula salivar de morcegos hematófagos sadios. Dos cinco morcegos positivos para a raiva no SNC pelas técnicas de imunofluorescência direta e isolamento viral em células N2A, 100 por cento (5/5) foram positivos para a raiva nas amostras de língua e coração, 80 por cento (4/5) no rim, 40 por cento (2/5) nas amostras de glândula salivar e pulmão, e 20 por cento (4/5) no fígado pe la técnica de RT-PCR. Todos os nove morcegos negativos no SNC, pela imunofluorescência e isolamento viral, foram negativos na glândula salivar pela RT-PCR. Possíveis consequências para a epidemiologia e patogênese da raiva são discutidas.

Detection of nucleoproteins in squamous cell carcinoma, and dysplastic and normal mucosa in the oral cavity by methyl green-pyronin staining.

Squamous cell carcinoma (SCC) is the most malignant neoplasm of the oral cavity. The mortality rate associated with head and neck cancers remains high, and thus detection techniques are important. In the present study, methyl green-pyronin staining was applied to 5 normal mucosa specimens, 10 cases of dysplastic mucosa, 12 cases of SCC (grade I), 10 cases of SCC (grade II) and 5 cases of SCC (grade III) in the oral cavity. This is the first study in which nuclear and nucleolar cytomorphometric parameters (diameter, area and number) in such oral lesions were evaluated using this method. As methyl green-pyronin selectively stains nucleic acids, it can differentiate between DNA (green) and RNA (red). The results reveal that the proposed method can be used to evaluate changes in the nucleus and nucleolus in premalignant lesions in the oral cavity.

Viral protein determinants of Lassa virus entry and release from polarized epithelial cells.

The epithelium plays a key role in the spread of Lassa virus. Transmission from rodents to humans occurs mainly via inhalation or ingestion of droplets, dust, or food contaminated with rodent urine. Here, we investigated Lassa virus infection in cultured epithelial cells and subsequent release of progeny viruses. We show that Lassa virus enters polarized Madin-Darby canine kidney (MDCK) cells mainly via the basolateral route, consistent with the basolateral localization of the cellular Lassa virus receptor alpha-dystroglycan. In contrast, progeny virus was efficiently released from the apical cell surface. Further, we determined the roles of the glycoprotein, matrix protein, and nucleoprotein in directed release of nascent virus. To do this, a virus-like-particle assay was developed in polarized MDCK cells based on the finding that, when expressed individually, both the glycoprotein GP and matrix protein Z form virus-like particles. We show that GP determines the apical release of Lassa virus from epithelial cells, presumably by recruiting the matrix protein Z to the site of virus assembly, which is in turn essential for nucleocapsid incorporation into virions.

Systemic infection of avian influenza A virus H5N1 subtype in humans.

The viral dissemination in a patient with avian influenza A subtype H5N1 infection was retrospectively studied by the immunohistochemical localization of viral nucleoprotein antigen. The pathology was marked by diffuse alveolar damage, lymphoid depletion, and reactive hemophagocytic syndrome. Besides the lung and the upper respiratory tract, viral antigen was detected in the small and large intestinal epithelial cells, hematopoietic cells in the bone marrow, glial cells and neurons of the brain, and lymphocytes. The results confirmed that H5N1 virus disseminated to multiple organs beyond the respiratory system. However, specific pathological changes were noted in the respiratory system only, and productive viral replication confirmed by culture was noted only in the lung. More postmortem studies are needed to elucidate the pathogenesis of this highly fatal zoonotic disease.

Evaluation of a virus derived from MDCK cells infected persistently with influenza A virus as a potential live-attenuated vaccine candidate in the mouse model.

A temperature-sensitive mutant virus unable to replicate at 38 degrees C was recovered from passage 189 (IVpi-189) of Madin-Darby canine kidney cells infected persistently with influenza A. Immunofluorescent staining of the IVpi-189 virus-infected cells revealed disrupted transport of the matrix (M) 1 protein into the nucleus at non-permissive temperatures, resulting in retention of the nucleoprotein (NP) in the nucleus. Upon comparison with the parental influenza A E61-24-P15 strain used to establish persistent infection, amino acid exchanges were found in the M1 protein of IVpi-189 virus; arginine to glutamine at position 72 and threonine to alanine at position 139. When mice were inoculated intranasally with IVpi-189 virus, virus growth in the lungs was restrained and terminated rapidly. Prior intranasal inoculation with only a small dose of IVpi-189 virus induced humoral and cellular immune responses and protected mice against subsequent virulent virus challenge. These results indicate that IVpi-189 virus, an avirulent temperature-sensitive mutant, is a promising candidate for use as a live-attenuated vaccine.

Development and application of monoclonal antibodies against avian influenza virus nucleoprotein.

Rapid and accurate diagnosis of avian influenza (AI) infection is important for an understanding epidemiology. In order to develop rapid tests for AI antigen and antibody detection, two monoclonal antibodies (mAbs) against influenza nucleoprotein (NP) were produced. These mAbs are designated as F26-9 and F28-73 and able to recognize whole AI virus particles as well as the recombinant NP. Both of the mAbs were tested in a slot blot for their reactivity against 15 subtypes of influenza virus; F28-73 reacted with all tested 15 subtypes, while F26-9 failed to react with H13N6 and H15N8. The mAb binding epitopes were identified using truncated NP recombinant proteins and peptide array techniques. The mAb F26-9 reacted with NP-full, NP-1 (638bp), NP-2 (315bp), NP-4 (488bp), and NP-5 (400bp) in the Western blot. The peptide array results demonstrated that the mAb F26-9 reacted with NP peptides 15-17 corresponding to amino acids 71-96. The mAb F28-73 recognized the NP-full, -1 and -4 fragments, but failed bind to NP-2, -3, -5, and any peptides. This antibody-binding site is expected to be contained within 1-162 amino acids of AI NP, although the exact binding epitope could not be determined. The two mAbs showed reactivity with AI antigen in immunofluorescence, immunohistochemistry and immune plaque assays. Immune response of AI infected animals was determined using the mAb F28-73 in a cELISA. All tested chickens were positive at 11 days post-infection and remained positive until the end of the experiment on day 28 (>50% inhibition). The two mAbs with different specificities are appropriate for developing various tests for diagnosis of AI infection.

Mutant influenza A virus nucleoprotein is preferentially localized in the cytoplasm and its immunization in mice shows higher immunogenicity and cross-reactivity.

Many influenza vaccines targeted to hemagglutinin (HA) show efficient immunogenicity for protecting subjects against influenza virus infection. Major antigenic changes to HA molecules can help influenza virus to develop resistance against HA-targeted vaccines. DNA vaccines encoding conserved antigens protect animals against diverse subtypes, but their potency requires further improvement. We generated a DNA-based nucleoprotein (NP)-targeted vaccine using an N-terminal mutant of NP (NPm) that efficiently localized in the cytoplasm, and examined the immune responses in mice immunized with NPm or wild-type (WT) NP DNA vaccine. Importantly, the NPm vaccine showed 1.5-2-fold higher immunogenicity than the WT NP vaccine in mice. Furthermore, NPm vaccination efficiently protected the mice against lethal challenge with influenza viruses and showed cross-reactivity toward heterologous viruses. Therefore, DNA-based vaccination with NPm may contribute to the development of protective immunity against diverse influenza virus through its ability to stimulate cellular immunity.

Alveolar epithelial cells direct monocyte transepithelial migration upon influenza virus infection: impact of chemokines and adhesion molecules.

Influenza A virus pneumonia is characterized by severe lung injury and high mortality. Early infection elicits a strong recruitment of monocytes from the peripheral blood across the endo-/epithelial barrier into the alveolar air space. However, it is currently unclear which of the infected resident lung cell populations, alveolar epithelial cells or alveolar macrophages, elicit monocyte recruitment during influenza A virus infection. In the current study, we investigated whether influenza A virus infection of primary alveolar epithelial cells and resident alveolar macrophages would elicit a basal-to-apical monocyte transepithelial migration in vitro. We found that infection of alveolar epithelial cells with the mouse-adapted influenza A virus strain PR/8 strongly induced the release of monocyte chemoattractants CCL2 and CCL5 followed by a strong monocyte transepithelial migration, and this monocytic response was strictly dependent on monocyte CCR2 but not CCR5 chemokine receptor expression. Analysis of the adhesion molecule pathways demonstrated a role of ICAM-1, VCAM-1, integrin-associated protein (CD47), and junctional adhesion molecule-c on the epithelial cell surface interacting with monocyte beta(1) and beta(2) integrins and integrin-associated protein in the monocyte transmigration process. Importantly, addition of influenza A virus-infected alveolar macrophages further enhanced monocyte transmigration across virus-infected epithelium in a TNF-alpha-dependent manner. Collectively, the data show an active role for virus-infected alveolar epithelium in the regulation of CCL2/CCR2-dependent monocyte transepithelial migration during influenza infection that is essentially dependent on both classical beta(1) and beta(2) integrins but also junctional adhesion molecule pathways.

Histologic otosclerosis is associated with the presence of measles virus in the stapes footplate.

HYPOTHESIS: Persistent measles virus infection of the otic capsule is presumed to be one of the etiologic factors in otosclerosis. The viral pathogenesis of otosclerosis could be established only by correlative analysis: histologic examination of the stapes footplates and reverse-transcriptase polymerase chain reaction amplification of the viral RNA. At present, histologic analysis of the removed stapes footplates is the only appropriate method of distinguishing otosclerotic and nonotosclerotic stapes fixations. BACKGROUND: The presence of measles virus was shown in otosclerotic patients by reverse-transcriptase polymerase chain reaction amplification of the viral RNA and detecting the viral proteins by immunohistochemistry. METHODS: Nucleic acids (mRNA, vRNA, and DNA) were extracted from ankylotic stapes footplates of stapes fixation patients (n = 44). Measles virus genomic nucleoprotein RNA was amplified by seminested reverse-transcriptase polymerase chain reaction. Amplification results were correlated to postoperative histologic findings. RESULTS: Measles virus RNA was detectable only in histologically otosclerotic stapes footplates (n = 32). Histology for virus-negative footplates (n = 12) excluded otosclerosis. Virus-negative stapes footplates showed annular calcification (n = 8), bone resorption with increased numbers of hemosiderophages (n = 2), and mononuclear cell infiltration with osteolysis (n = 2). CONCLUSION: Stapes ankylosis is a heterogenous disease causing conductive hearing loss with different causes. Nonotosclerotic stapes fixations may belong to degenerative disorders with variable histopathology. Otosclerosis is an inflammatory disease resulting from persisting measles virus infection of the otic capsule.

Pulmonary ultrasonographic abnormalities associated with naturally occurring equine influenza virus infection in standardbred racehorses.

The purpose of this investigation was to determine if naturally occurring acute infectious upper respiratory disease (IRD) caused by equine influenza virus is associated with ultrasonographically detectable pleural and pulmonary abnormalities in horses. Standardbred racehorses were evaluated for signs of IRD, defined as acute coughing or mucopurulent nasal discharge. For every horse with IRD (n = 16), 1 or 2 horses with no signs of IRD and the same owner or trainer (n = 30) were included. Thoracic ultrasonography was performed within 5-10 days of the onset of clinical disease in horses with IRD. Horses without IRD were examined at the same time as the horses with IRD with which they were enrolled. The rank of the ultrasound scores of horses with IRD was compared to that of horses without IRD. Equine influenza virus was identified as the primary etiologic agent associated with IRD in this study. Mild lung consolidation and peripheral pulmonary irregularities were found in 11 (69%) of 16 of the horses with IRD and 11 (37%) of 30 of control horses. Lung consolidation (median score = 1) and peripheral irregularities scores (median score = 1) were greater in horses with IRD compared to horses without IRD (median score = 0; P < .05). Pleural effusion was not observed. Equine influenza virus infection can result in abnormalities of the equine lower respiratory tract. Despite the mild nature of IRD observed in this study, lung consolidation and peripheral pulmonary irregularities were more commonly observed in horses with clinical signs of IRD. Further work is needed to determine the clinical significance of these ultrasonographic abnormalities.