NUTRIA (Myocastor coypus) HEALTH STATUS IN THE NATURAL PARK “LA MANDRIA”. ANATOMOPATHOLOGICAL AND MICROBIOLOGICAL INVESTIGATIONS

Nutria (Myocastor coypus) is a medium-sized rodent native of South America introduced in North America and Europe, where it has been managed to establish naturalized populations. In Italy the first specimens of Nutria were imported for commercial breeding (fur production). After World War II, faced with a crisis of this business, small entrepreneurs, to avoid the costs of abatement, intentionally released animals, causing their rapid distribution in the area and modifying the original zoogeographic profile, with a considerable impact on environmental components [1]. Aim of this work was to evaluate by means of necropsy, histopathological and microbiological investigations the sanitary status in nutrias included in an eradication programme in the Regional Park "La Mandria" (Northwestern Italy), with special interest for viral, bacterial and parasitic diseases. Following the post-mortem examination of 44 carcasses of Nutria (25 males and 19 females), samples of organs were collected and frozen at -20°C and/or fixed in buffered formalin; laboratory investigations have been performed according to standard methods. Histologically, the organs showing the highest number of lesions were the liver (activation of periportal lymphoid tissue: 44.4%), kidney (non-purulent lymphocytic interstitial nephritis: 87%) and lung, in which alterations were detected in all the analysed samples (parenchymal: 81.8% and perivascular: 72.7% lymphocytic inflammatory infiltrate). Bacteriological tests provided negative results in all the samples for Francisella spp., as previously reported [2]. Bacteriological examination performed on lung yielded in 25/44 cases (64.1%) the isolation of different bacteria. In detail: polymicrobism (15.4% of samples), Enterococcus (17.9%) and Pseudomonas (10.3%), whereas in the remaining 20.5% of samples bacteria of the genus Achromobacter, Nocardia, Streptococcus, Brevibacillus, Ochrobactrum and Corynebacterium were detected. Although, previous investigations reported seropositivities in nutrias for viral encephalomyocarditis (EMCV) [2, 3], no subject was tested positive in this study. No Nutria was tested positive for Hepatitis E Virus (HEV), as previously reported [4]. Two samples out of 35 (5.7%) resulted positive for Toxoplasma gondii, while no Neospora caninum infection was detected. Toxoplasmosis is a common infection in nutria [2, 3]. Besides being potential source of T. gondii for scavengers, they constitute relevant species to monitor the burden of oocysts in the wild environment. A continuous health monitoring of the populations of nutria is necessary in order to assess and prevent any health risk for wildlife and humans. [1] Global invasive species database (ISSG). 2010. [2] Martino et al. Seroprevalence for selected pathogens of zoonotic importance in wild nutria (Myocastor coypus), European Journal of Wildlife Research, 60:551–4, 2014. [3] Bollo et al. Health status of a population of nutria (Myocastor coypus) living in a protected area in Italy, Research in Veterinary Science, 75:21–5, 2003. [4] Serracca et al. Molecular investigation on the presence of Hepatitis E Virus (HEV) in wild game in North-Western Italy, Food and Environmental Virology, 7:206–12, 2015.