Free-ranging red deer contribution to enviromental contamination of shiga toxin-producing Escherichia Coli Italian Alps

Wild ungulates are increasing their density and distribution across Europe. At the same time, habitat fragmentation caused by human activities and infrastructures favours proximity with humans, livestock and other animal species. This critical issue for public health and for conservation, highlights the need for ecological studies of multi-host infections within an eco-evolutionary framework. Red deer (Cervus elaphus) is among the most representative species of such patterns: in the Stelvio National Park (SNP, central Italian Alps), for example, very high population density is associated with intense browsing impacts and cross transmission of pathogens with domestic ruminants (Galiero et al., 2018). In turn, a culling plan has been initiated in the Lombardy sector of the Park, with the aim to reduce red deer density: this led to the introduction of some 37.3 tons of meat into the food chain over just 5 years, between 2011 and 2016 (Pedrotti et al., 2017), with potential consequences on human health. Among food-borne pathogens, herbivorous are the main reservoir of Shiga toxin-producing Escherichia coli (STEC). The microorganism is shed in feces and can persist in the environment, rising the risk of ingestion, intestinal colonization and fecal shedding in increased numbers of grass-feeding animals. This study aims to evaluate the prevalence, antimicrobiol susceptibility and spatial distribution of STEC in red deer in the Lombardy sector of the SNP in January and February 2017. The analysis was based on the collection of feces from 65 red deer from three culling areas with different anthropization levels (low, moderate, high), for which radio-tracking showed low or absence of deer movements among areas. Feces were enriched into modified Tryptone Soya Broth, and DNA was extracted for stx genes PCR. Positive samples were plated on Levine-eosin methylene blue agar and 20 single E. coli colonies were tested by PCR to confirm STEC identification and evaluate the presence of eaeA gene. The isolates were tested for their susceptibility to 12 antimicrobial agents by disc diffusion. Twelve of 65 feces were positive for STEC, showing a prevalence in red deer of 18.4% (95% CI:10.8-29.5), with strains harboring stx2 (n=7) or stx1 (n=5). No strain carried both stx genes and eae gene was never detected. STEC positive calves were only detected in high antropised area. The STEC isolates were resistant to at least one of the antimicrobial agents tested, mostly ampicillin. The present study showed that red deer shed STEC in environment during winter, with prevalence similar to cattle. Additional samples and characterization of STEC serotypes are needed to highlight the effects of environmental and human-mediated factors influencing the infection dynamics. References Galiero A, Leo S, Garbarino C, Arrigoni N, Russo S, Giacomelli S, Bianchi A, Trevisiol K, Idrizi I, Daka G, Fratini F, Turchi B, Cerri D, Ricchi M. Mycobacterium aviumsubsp. paratuberculosis isolated from wild red deer (Cervus elaphus) in Northern Italy. Vet Microbiol. 2018, 217:167-172.