05.04.2022: In autumn 2019, an acute die-off was reported among European hares (Lepus europaeus) in northeastern Austria. A recently published study led by Vetmeduni shows that the most likely cause was an infection with the bacterial pathogen Cronobacter turicensis. This could be dangerous not only for the hares. According to the researchers, there is also a risk of transmission to humans.
The recent study aimed to investigate and characterise the cause of the hare deaths in 2019 phenotypically and genetically. The team of researchers proved that the death of the hares from typhlocolitis (inflammation of the large intestine) was caused by genetically different strains of the bacterium Cronobacter turicensis. According to the scientists, this is the first evidence of a clinical infection in wild animals worldwide. Previously, clinical infections had only been detected in humans.
Potential for transmission to humans
The study, which was recently published in Letters in Applied Microbiology, demonstrates that C. turicensis could be associated with epidemiologically related cases of typhlocolitis in European hares. “Due to the potential of this bacterium to inflict severe disease in humans, the risk of a spillover should be kept in mind, especially for those people in direct contact with hares, such as hunters, farmers or veterinarians,” says the study’s first author, Annika Posautz of the Research Institute of Wildlife Ecology at Vetmeduni.
Investigation of further wildlife populations recommended
As the pathogen C. turicensis is mainly known to cause disease in immunocompromised humans and newborns, this previously unrecognised potential for spillover from wildlife to humans deserves serious attention. The experts therefore recommend a more detailed investigation of wild animal populations: “The risk of a spillover of the bacterium Cronobacter turicensis highlights the importance of investigating the general role of wild animals as a reservoir of potentially pathogenic C. turicensis strains”, say Annika Posautz and Igor Loncaric, the study’s last author.
Cronobacter: a potentially life-threatening bacterial genus
Nine hares that died in autumn 2019 were examined in the study. All nine showed very similar lesions in necropsy and histopathology. Five of the animals were found to be infected with C. turicensis, while the other four were infected with unrelated bacteria. The bacterial genus Cronobacter, which currently comprises seven species, is primarily known as a ubiquitous, opportunistic pathogen that can contaminate several types of food products. Particularly dangerous are the two species C. sakazakii and C. malonaticus, which are involved in most clinical Cronobacter infections in humans, causing severe symptoms such as blood poisoning, necrotising enteritis (inflammation of the intestine) and meningitis (infection of meninges). In contrast to humans, clinical infections caused by members of the genus Cronobacter have, to the authors’ knowledge, never been reported in animals.
The article “Outbreak of Cronobacter turicensis in European brown hares (Lepus europaeus)” by Annika Posautz, Michael P. Szostak, Adriana Cabal Rosel, Franz Allerberger, Anna Stöger, Gerhard Rab, Andrea T. Feßler, Joachim Spergser, Anna Kübber-Heiss, Stefan Schwarz, Stephen J. Forsythe, Werner Ruppitsch and Igor Loncaric was published in Letters in Applied Microbiology.
To the sientific paper