Chlamydia muridarum infection causes bronchointerstitial pneumonia in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice

The murine bacterial pathogen Chlamydia muridarum (Cm) has been used to study human Chlamydia infections in various mouse models. CD4+ T-cells, natural killer cells, and interferon-gamma (IFN-γ)-mediated immunity are important to control experimentally induced Cm infections. Despite its experimental use, natural infection by Cm has not been documented in laboratory mice since the 1940s. In 2022, the authors reported the discovery of natural Cm infections in numerous academic institutional laboratory mouse colonies around the globe. To evaluate the impact of Cm infection in severely immunocompromised mice, 19 NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice were cohoused with Cm shedding, naturally infected immunocompetent mice and/or their soiled bedding for 4 weeks and subsequently euthanized. Clinical disease, characterized by lethargy, dyspnea, and weight loss, was observed in 11/19 NSG mice, and 16/18 NSG mice had neutrophilia. All mice exhibited multifocal to coalescing histiocytic and neutrophilic bronchointerstitial pneumonia (17/19) or bronchiolitis (2/19) with intraepithelial chlamydial inclusions (CIs). Immunofluorescence showed CIs were often associated with bronchiolar epithelium. CIs were frequently detected by immunohistochemistry in tracheal and bronchiolar epithelium (19/19), as well as throughout the small and large intestinal epithelium without lesions (19/19). In a subset of cases, Cm colonized the surface epithelium in the nasopharynx (16/19), nasal cavity (7/19), and middle ear canal (5/19). Endometritis and salpingitis with intraepithelial CI were identified in a single mouse. These findings demonstrate that Cm infection acquired through direct contact or soiled bedding causes significant pulmonary pathology and widespread intestinal colonization in NSG mice.

Deer mastadenovirus B pneumonia in a white-tailed deer fawn

A 7-mo-old farmed white-tailed deer fawn (Odocoileus virginianus) died after several weeks of progressive deterioration associated with endoparasitism and respiratory signs. A field autopsy was performed, and lung tissue was submitted for histologic examination. The findings were consistent with necrosuppurative bronchointerstitial pneumonia with intranuclear viral inclusions. Immunofluorescence using fluorescently labeled polyclonal antibodies to bovine adenovirus 3 and 5 was positive. To rule out cross-reactivity with other adenoviruses, formalin-fixed, paraffin-embedded tissue sections were submitted for genome sequence analysis, which revealed a 99.6% match to Deer mastadenovirus B (formerly Odocoileus adenovirus 2, OdAdV2). To our knowledge, natural clinical disease associated with OdAdV2 has not been reported previously.

IN SITU HYBRIDIZATION AND VIRUS CHARACTERIZATION OF SKUNK ADENOVIRUS IN NORTH AMERICAN WILDLIFE REVEALS MULTISYSTEMIC INFECTIONS IN A BROAD RANGE OF HOSTS

Skunk adenovirus-1 (SkAdV-1) has been reported infecting several North American wildlife species; however, lesions associated with disease have not yet been completely characterized, particularly in porcupines. We describe and characterize the tissue distribution and lesions associated with SkAdV-1 infection in 24 wildlife diagnostic cases submitted between 2015 and 2020, including 16 North American porcupines (Erethizon dorsatum), three striped skunks (Mephitis mephitis), and five raccoons (Procyon lotor), which constitute a new host species. The most common lesion in all species was severe necrotizing bronchopneumonia with (n=12) or without (n=10) interstitial involvement. Intranuclear inclusion bodies were common in respiratory epithelium (n=21) and less often in renal tubular (n=6) and biliary epithelium (n=1). Several cases (n=4) had secondary bacterial infections, including Bordetella bronchiseptica, Pasteurella multocida, and Streptococcus zooepidemicus. In situ hybridization in porcupine (n=6), raccoon (n=1), and skunk (n=1) revealed SkAdV-1 DNA in multiple tissue types, including lung, trachea, turbinates, liver, kidney, lymph node, and brain, and multiple cell types including epithelial, endothelial, and mesothelial cells. These findings were consistent across species. Comparison of viral genomes from a porcupine and a raccoon with that originally isolated from a skunk demonstrated DNA point mutations affecting several viral genes, including the fiber protein gene. Our findings show the spectrum of disease associated with SkAdV-1 infection in a broad host range of wildlife species.

Acute interstitial pneumonia in foals: A severe, multifactorial syndrome with lung tissue recovery in surviving foals

BACKGROUND

Acute interstitial pneumonia in foals has been sparsely described in literature, and the individual authors disagree on the underlying aetiology. Histopathological follow-up from surviving foals is not available.

OBJECTIVES

Description of clinical and histopathological findings in the course of acute interstitial pneumonia and in recovery. Investigating the aetiology and possible triggering factors of acute interstitial pneumonia.

STUDY DESIGN

Case series.

METHODS

Post-mortem examination of nine affected foals; seven died during the acute phase, and two had recovered from acute interstitial pneumonia. Data from clinical examinations on the day of death were recorded for all foals. Complete necropsy, special histological staining, virological and microbiological examinations were performed.

RESULTS

Seven foals died during the acute phase with severe respiratory distress, fever and increased numbers of comet tail artefacts in lung ultrasound. In post-mortem examination, a wide variety of possible triggering factors was identified. Microbiology revealed Escherichia coli, Rhodococcus equi and Klebsiella pneumoniae as the most common bacterial pathogens. Equine herpesvirus 2 was detected in all foals by PCR. Those with high viral loads also displayed histopathological changes suggestive of viral infections. Pneumocystis carinii was detected in all acutely affected foals. Histopathological changes in lung parenchyma clearly differed between the foals that had recovered from acute interstitial pneumonia and those dying in the acute phase. While lungs in acute phase featured marked parenchymal collapse and necrosis, the recovered foals revealed nearly normal ventilated lung parenchyma and alveolar structure.

MAIN LIMITATIONS

Small number of cases. Because all foals are from the same breeding farm with endemic occurrence of pathogens, it is not certain whether the results of this study can be transferred to other foals without restrictions.

CONCLUSIONS

Acute interstitial pneumonia seems to be based on a multifactorial aetiology. Lungs from foals that have survived acute interstitial pneumonia appear to be able to regenerate completely, leaving no permanent changes.