LISTERIA MONOCYTOGENES INFECTION IN FREE-RANGING RED FOXES (VULPES VULPES) AND EURASIAN LYNX (LYNX LYNX) IN SWITZERLAND.

Listeria monocytogenes is an ubiquitous environmental saprophytic bacterium causing listeriosis in domestic animals, humans, and occasionally wildlife. In animals, this foodborne zoonotic disease mainly occurs in ruminants and it is rare in carnivores. Seven red foxes (Vulpes vulpes) and one Eurasian lynx (Lynx lynx) were diagnosed with listeriosis between 2010 and 2021 at the Institute for Fish and Wildlife Health, Bern, Switzerland. Necropsy and histopathology revealed meningitis (six of seven red foxes), hepatitis (six of seven red foxes), pneumonia (five of seven red foxes), splenitis (two of seven red foxes) and splenomegaly (the Eurasian lynx, two of seven red foxes). Listeria monocytogenes was isolated from either lung, spleen, liver, or kidney of all animals. Serotyping detected L. monocytogenes serotype 1/2a in five red foxes and the Eurasian lynx and serotype 4b in two red foxes. Six red foxes were positive for canine distemper virus (CDV) by polymerase chain reaction, whereas the Eurasian lynx and one red fox were negative. One red fox that was positive for CDV and listeriosis was also diagnosed with salmonellosis. The identified L. monocytogenes serotypes are among the three most frequently isolated serotypes (1/2a, 1/2b, and 4b) from food or the food production environment and those that cause most listeriosis cases in humans and animals. Coinfection with CDV in six red foxes questions the role of CDV as potential predisposing factor for septicemic listeriosis. The detection of listeriosis in the regionally endangered Eurasian lynx and in carnivores highly abundant in urban settings, such as red foxes, reinforces the importance of wildlife health surveillance in a One Health context and adds the Eurasian lynx to the list of carnivores susceptible to the disease. Further investigations are required to assess the prevalence and epidemiology of L. monocytogenes in free-ranging carnivores and its interaction with CDV.

Exploring the epidemiological role of the Eurasian lynx (Lynx lynx) in the life cycle of Toxoplasma gondii.

Toxoplasma gondii is a successful coccidian parasite able to infect all warm-blooded animals and humans, causing one of the most common zoonoses worldwide. The Eurasian lynx (Lynx lynx) is one of the feline potential hosts of T. gondii in Switzerland, but little is known about its epidemiological role as a definitive or intermediate host. Serum samples from 183 Eurasian lynx collected from 2002 to 2021 were tested for antibodies to T. gondii by ELISA, IFAT and in case of inconclusive results, immunoblot. Antibodies to T. gondii were found in 150 of 183 (82%) Eurasian lynx. Older age, good health status and a low-altitude habitat were found to be significant predictors for seropositivity. T. gondii oocysts were detected in 3 of 176 (1.7%) faecal samples, indicating the Eurasian lynx as a definitive host. In addition, T. gondii DNA was detected in skeletal muscle (7/88), heart muscle (2/26) and/or brain tissue (2/36) from 10 different lynx by real-time PCR. In one animal, a T. gondii-like tissue cyst was observed in heart muscle and confirmed as T. gondii by immunohistochemistry (1/20) and real-time PCR. With an adapted nested-PCR-multilocus-sequence typing (MLST) and in silico restriction-fragment-length-polymorphism analysis (RFLP) approach two different T. gondii genotypes were detected: a lineage II variant (ToxoDB #3) in three animals (two oocyst samples and one heart muscle sample) and a novel genotype exhibiting both type II and III alleles in a further animal (skeletal muscle). The present results indicate that T. gondii infection is widespread in the Swiss lynx population. The Eurasian lynx may contribute to environmental contamination with oocysts and is able to harbour the parasite in different tissues. Genotyping revealed the presence of both a common T. gondii lineage in Europe and a previously unknown genotype and thus shedding more light on the complex molecular epidemiology of T. gondii.