Bjarne Bergsjø

In 2019, an outbreak of acute haemorrhagic diarrhoea (AHD) in dogs in Norway was linked to Providencia alcalifaciens . A marked increase in diarrhoeal cases in dogs during the autumn, along with the frequent identification of P. alcalifaciens in affected dogs, supports its role as a causative agent in seasonal diarrhoea in dogs in Norway. Previous phylogenetic studies have revealed two major genetic lineages of P. alcalifaciens , one of which is associated with diarrhoeal disease and carries a plasmid-borne type 3 transport system (T3SS _1a ). The aim of this study was to place Norwegian P. alcalifaciens isolates in a global phylogenetic context and to characterize the distribution of putative virulence-associated genes (VAGs) in isolates from dogs with AHD. Whole-genome sequencing was performed on 273 isolates, and 48 publicly available genomes were included for comparative analyses. Bioinformatic processing and phylogenetic analyses were conducted on the complete dataset of 321 P . alcalifaciens genomes. VAGs were identified using ABRicate and two virulence gene databases. Phylogenetic analyses revealed two main clusters, A and B. Most isolates from sick dogs belonged to cluster A, particularly to subcluster A-1 – the largest of five subclusters – which primarily contained isolates from sick dogs. All isolates in subclusters A-1 and A-4 harboured genes encoding T3SS _1a , a type II secretion system and the effector genes stcE , yopJ and cdtA-C . blast searches using closed reference genomes showed high sequence identity (>90%) to plasmid elements in 196 of 197 isolates from subclusters A-1 and A-4, suggesting plasmid-mediated acquisition of virulence factors. These findings support that specific genetic variants of P. alcalifaciens , particularly those in subclusters A-1 and A-4, exhibit increased virulence potential and are associated with AHD in dogs. The high proportion of isolates from clinically affected dogs, including many from the 2019 outbreak, further underscores the link between subcluster A-1 and disease.

An outbreak investigation was initiated in September 2019, following a notification to the Norwegian Food Safety Authority (NFSA) of an unusually high number of dogs with acute haemorrhagic diarrhoea (AHD) in Oslo. Diagnostic testing by reporting veterinarians had not detected a cause. The official investigation sought to identify a possible common cause, the extent of the outbreak and prevent spread. Epidemiological data were collected through a survey to veterinarians and interviews with dog owners. Diagnostic investigations included necropsies and microbiological, parasitological and toxicological analysis of faecal samples and food. In total, 511 dogs with acute haemorrhagic diarrhoea were registered between 1 August and 1 October. Results indicated a common point source for affected dogs, but were inconclusive with regard to common exposures. A notable finding was that 134 of 325 faecal samples (41%) cultured positive for Providencia alcalifaciens. Whole genome sequencing (WGS) of 75 P. alcalifaciens isolates from 73 dogs revealed that strains from 51 dogs belonged to the same WGS clone. Findings point to P. alcalifaciens as implicated in the outbreak, but investigations are needed to reveal the pathogenic potential of P. alcalifaciens in dogs and its epidemiology.

In spite of yearly vaccination, outbreaks of canine infectious respiratory disease are periodically seen amongst domestic dogs. These infections compromise host defense mechanisms, and, when combined with other stressful events, allow opportunistic pathogens like Streptococcus equi subsp. zooepidemicus to create serious disease. Early recognition and treatment are tremendously important for a successful outcome in these cases. A polyvalent vaccine was given to 22 racing dogs three days after a competition, followed by two days of rest, and then the dogs were returned to regular training. Coughing was noticed among the dogs four days after immunisation. Three days after this outbreak one of the dogs was unusually silent and was found dead the next morning. Simultaneously two other dogs developed haemorrhagic expectorate, depression and dyspnea and were brought in to the veterinary hospital. Streptococcus equi subsp. zooepidemicus was isolated in pure culture from all three cases. They were treated and rehabilitated successfully, and won a sledge race three months later. This paper discusses the necropsy results, treatment regime, rehabilitation and the chronology of vaccination, stressful events and disease.