Haemorrhagic pneumonia in sled dogs caused by Streptococcus equi subsp. zooepidemicus - one fatality and two full recoveries: a case report

Streptococcus zooepidemicus in dogs: Exploring a canine pathogen through multilocus sequence typing

Streptococcus equi. subsp. zooepidemicus (S. zooepidemicus) associated diseases in dogs have emerged as a significant concern over recent decades. S. zooepidemicus occurs sporadically in dog populations globally, with increased prevalence in shelters/kennels. This study used multilocus sequence typing (MLST) of 149 independent canine S. zooepidemicus isolates to assess associations between sequence type and breed, country of origin, disease severity, sampling type, year, and behaviour within an outbreak. No clear associations for breed, country, sampling type and year were determined in this study. ST-10 and 123 strains were present within all disease categories, from no clinical signs to severe disease. Assessment of S. zooepidemicus infection in 3 UK outbreaks at the same location found ST-10, 18, 123 strains, and a ST-173 strain in a US outbreak, were associated with haemorrhagic pneumonia and persisted in kennelled populations over time. The ST-173 clonal complex has been noted to have severe virulence capabilities in dogs and other species. S. zooepidemicus seems to thrive in environments with a high risk of transmissibility, overcrowding, stress and naïve populations, particularly for those in shelters/kennels. MLST alone cannot determine the virulence phenotype of S. zooepidemicus in dogs. However, a level of conservancy and diversity within ST allelic loci aids the opportunity to cause severe disease in dogs. Thus, further research into whole genome sequencing and characterising the virulence factors of S. zooepidemicus is warranted in dogs.

Cases of high mortality in cull sows and feeder pigs associated with Streptococcus equi subsp. zooepidemicus septicemia

Investigations of 2 cases of high mortality in cull sows and feeder pigs from a buying station in Ohio and cull sows at an abattoir in Tennessee were conducted at the Iowa State University Veterinary Diagnostic Laboratory. The animals were presented as weak, lethargic, and some with high fever. Rapidly escalating mortality was reported to be as high as 30-50% within groups at the buying station over 8-10 d, and 30-40% over 5-7 d at the abattoir. Splenomegaly and red lymph nodes were the most consistent macroscopic findings, with scant fibrinous polyserositis observed in one sow. The microscopic lesions of vasculitis, fibrin thrombi, fibrinosuppurative polyserositis, and intralesional bacteria were consistent with acute bacterial septicemia. Bacterial culture isolated Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) from multiple organs, including spleen, lung, and kidney. PCR tests were negative for African swine fever virus, classical swine fever virus, Erysipelothrix rhusiopathiae, porcine reproductive and respiratory syndrome virus, porcine circovirus 2, and Salmonella spp. Porcine circovirus 3 was inconsistently detected at low levels by PCR, with a lack of associated lesions. Next-generation sequencing identified S. zooepidemicus and porcine partetravirus in the serum sample of the feeder pig from the buying station. Phylogenetic analysis of the szP gene indicated that the S. zooepidemicus isolates from Ohio and Tennessee are in genotype VI. We conclude that the cause of these high mortality events in swine was S. zooepidemicus septicemia.

Possible canine source of Streptococcus equi subspecies zooepidemicus causing meningitis in an infant

Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) is a pathogen that colonizes and causes disease in horses, and less commonly, in other mammals. This zoonotic disease in humans is rare. In the reported human cases, it has caused bacteremia, endocarditis, arthritis and meningitis, and it has been linked to contact with horses or ingestion of unpasteurized dairy products.

We report a case of a six-month-old female patient who presented with a one-day history of fevers and neurological symptoms. Blood and cerebrospinal fluid cultures revealed S. zooepidemicus, and brain imaging showed a subdural fluid collection and diffuse brain infarcts. Exposure history suggested a canine source as patient had close contact with two dogs that had respiratory infections but no contact with other pets including horses. She had clinical and radiographic improvement after a four-week course of penicillin G and drainage of a subdural fluid collection but she had residual severe to profound hearing loss and mild neurocognitive deficits. This case report provides the third reported case of possible S. zooepidemicus transmission from dogs to humans, and the second such case that has led to meningitis. Clinicians and public health practitioners should recognize that S. zooepidemicus may be transmitted from dogs and can lead to severe disease in humans.

Interstitial lung diseases in dogs and cats part II: Known cause and other discrete forms

In addition to idiopathic interstitial pneumonias, interstitial lung diseases (ILDs) can occur secondary to known causes or be classified as discrete syndromes. Also known as diffuse parenchymal lung diseases, the ILDs represent a heterogenous group of non-infectious, non-neoplastic disorders characterized by varied patterns of inflammation and fibrosis. Characteristically associated with the true interstitium (i.e. the anatomic space lined by alveolar epithelial cells and capillary endothelial cells and the loose-binding connective tissue), it is important to understand ILDs are associated with pathology of the distal lung parenchyma and thus lesions can be bronchiolocentric or resemble alveolar filling disorders. Injury to the distal lung can occur via inhalation or hematogenous routes. This review will build on a proposed classification scheme adapted from human medicine to describe known cause and discrete forms of ILDs in dogs and cats.

Establishment and characterization of a telomerase-immortalized canine bronchiolar epithelial cell line

Dogs are susceptible to infectious diseases that occur primarily in the respiratory tract. The airway epithelium acts as a first line of defense and is constantly exposed to microorganisms present in the environment. Respiratory epithelial cells have recently gained wide use as a cell model for studying the pathogenesis of human, murine or swine respiratory pathogen infections. However, studies of the pathogenic mechanisms of canine pathogens have been hindered by the lack of reliable respiratory cell lines. Here, we cultured primary canine bronchiolar epithelial cells (CBECs), whose characteristics were confirmed by their expression of the epithelial cell-specific marker cytokeratin 18, and have provided protocols for their isolation and ex vivo expansion. Further, we established immortalized CBECs containing the human telomerase reverse transcriptase (hTERT) gene via transfection of primary CBECs with the recombinant plasmid pEGFP-hTERT. Immortalized bronchiolar epithelial cells (hTERT-CBECs) retain the morphological and functional features of primary CBECs, as indicated by reverse transcriptase polymerase chain reaction, proliferation assays, karyotype analysis, telomerase activity assay, and Western blotting, which demonstrate that hTERT-CBECs have higher telomerase activity, an extended proliferative lifespan, and a diploid complement of chromosomes, even after Passage 50. Moreover, this cell line is not transformed, as evaluated using soft agar assays and tumorigenicity analysis in nude mice, and can therefore be safely used in future studies. The isolation and establishment of stable hTERT-CBECs is of great importance for use as an in vitro model for mechanistic studies of canine pathogenic infections.