First detection of Glaesserella australis in swine herds in Ontario

Ðurđa Slavić, Sarah Lippert and Madison McGrogan

Animal Health Laboratory, University of Guelph, Guelph, ON

AHL Newsletter 2023;27(2):15.

For the first time, Glaesserella australis was confirmed in two different swine herds in Ontario.  Samples from multiple pigs were submitted to the AHL from both herds, and G. australis was isolated from pericardium and lung of one pig in each herd.  In both cases, a variety of other pathogens were also detected including Streptococcus suis, Pasteurella multocida, Actinobacillus porcitonsillarum, influenza A, and PRRSV.   

A novel Glaesserella sp. causing disease in Australian pigs was first time reported in 2018, followed by a new species description of Glaesserella australis in 2020.  This novel bacterial species closely resembles Glaesserella parasuis, and it has been isolated from clinically affected pigs with signs of bronchopneumonia and from lung lesions and abscesses detected in abattoirs from clinically healthy pigs.  Distribution of the lung lesions did not have any specific pattern, with abscesses scattered throughout dorsal as well as cranioventral lobes.  However, clinical and histopathological findings highly resemble the ones caused by Actinobacillus pleuropneumoniae which may be explained by the fact that some G. australis isolates carry genes with 84% similarity to ApxIII cytotoxin of A. pleuropneumoniae.  While the full virulence potential of these isolates remains to be established, their prevalence in Australian pigs appears to be low, with only 5.6% (3/54) farms being positive for this bacterium. 

Given the very recent isolation of G. australis in Ontario, information about its prevalence and clinical significance also needs to be established.  At AHL, all swine submissions are routinely checked for the presence of G. australis since November of 2022, and based on preliminary findings (i.e., 2 positive farms) the prevalence in clinical cases appears to be low.  AHL will continue to monitor the prevalence of G. australis, and will provide updates as they become available.   AHL                    


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2. Turni C, et al. Glaesserella australis sp. nov. isolated from the lungs of pigs. Int J Syst  Evol Microbiol 2020;70:3686-3692.

3. Watt AE, et al.  A novel Glaesserella sp. isolated from pigs with severe respiratory infections has a mosaic genome with virulence factors putatively acquired by horizontal transfer.  Appl Environ Microbiol 2012;84:e00092-18.