Occurrence and Monitoring of the Zoonotic Pathogen Yersinia pseudotuberculosis in Various Zoo Animal Species

Abstract

Infections with the zoonotic pathogen Yersinia (Y.) pseudotuberculosis are commonly causing clinical diseases and acute deaths in various mammal and bird species in zoos. These findings prompted us to conduct a targeted study that included animals of 18 German and 1 Swiss zoo that had been affected by the pathogen previously. This study provides a comprehensive overview of susceptible zoo animal species, clinical signs, therapies, antimicrobial resistance, pathogen monitoring, and prophylactic measures. In addition, fecal samples from species with documented infections and organ samples from deceased mammals and birds from two of the participating zoos, the urban zoo Wilhelma and the rural Opel Zoo, were examined for Y. pseudotuberculosis using both direct plating and enrichment. The overall prevalence of Y. pseudotuberculosis was 3.1% at the Opel Zoo and 1.3% at the Wilhelma. Fecal samples yielded positive results in 1.4% of the tested samples from the Opel Zoo but none from the Wilhelma. Among carcasses, 16.7% and 1.7% tested positive at the Opel Zoo and the Wilhelma, respectively (p = 0.006). Y. pseudotuberculosis was significantly more frequently isolated during the cold season (p = 0.002). Affected animals often died suddenly, displaying no or only non-specific clinical signs, but postmortem examinations revealed septicemia with multiple bacterial organ abscesses. Rodents, ruminants, primates, and Piciformes were the most commonly affected orders. Considering the zoonotic potential of Y. pseudotuberculosis, this research underscores the importance of investigations in zoos in accordance with the targets of the One Health approach.

Keywords: Yersinia pseudotuberculosis; antimicrobial testing; clinical and pathological signs; mammals and birds; prevalence; prevention; seasonal occurrence; zoonosis.

Figure 5

Maned wolf with icteric mucous membranes. Photo: Marco Roller, Zoo Karlsruhe.

Figure 1

Results of a total of 772 monitoring samples from the Opel Zoo and Wilhelma Zoo taken from June 2023 to May 2024.

Figure 2

Liver (A) and spleen (B) of a patas monkey (Erythrocebus patas) infected with Y. pseudotuberculosis with multifocal miliary lesions (two lesions of each organ are marked with white arrows). Y. pseudotuberculosis was isolated from both organs by bacteriological examination. Photos (A,B): Martin Peters, CVUA Westphalia.

Figure 3

Histo-pathological sections of the liver of a patas monkey (s. Figure 2) with mild periportal lymphocytic infiltrates (black arrow) (A) and acute irregular necrotic to pyogranulomatous lesions (black stars) (A,B) as depicted in the higher magnification (B). H&E staining; 100× magnification (A), 200× magnification (B). Photos (A,B): Martin Peters, CVUA Westphalia.

Figure 4

Histo-pathological sections of the spleen of a patas monkey (s. Figure 2). Severe congestion and multifocal acute coagulation necrosis (black star) (A) and pyogranulomatous foci depicted in the higher magnification (B). H&E staining at 100× magnification (A) and 200× magnification (B). Photos (A,B): Martin Peters, CVUA Westphalia.

Figure 6

Spleen and liver of the maned wolf with multiple abscesses. Photo: CVUA Stuttgart.

Figure 7

Severely swollen knee joint with skin ulcer (A) and its respective cut section (B) of a red kangaroo (Osphranter rufus) with purulent gonitis caused by Y. pseudotuberculosis. Photos: Martin Peters, CVUA Westphalia.