Zoonoses surveillance in Italy (2000-2009): Investigation on animals with neurological symptoms

The objective of this study was to investigate the presence of neurological zoonoses or zoonotic agents in Italy, and to estimate the epidemiological impact of neurological diseases potentially transmissible to humans. From 01 January 2008 to 31 December 2009, 990 animals of different species presenting with neurological signs were investigated in the different participating study centres. All subjects underwent clinical examination and only cases with central nervous system (CNS) involvement were analyzed further. Serum or whole blood and cerebrospinal fluid (CSF) were collected and examined. When the animals died or were slaughtered, necropsy was performed and samples were collected from the various organs and the CNS. Depending on the symptoms reported, samples from the spinal cord, muscles and nerves were also taken. Moreover, a retrospective investigation of cases recorded in the database of the participating study centres from 01/01/2000 to 31/12/2007 was performed. The case history of 570 animals dead or slaughtered, presenting with neurological signs and inflammatory lesions was examined. Among these, all the cases had already been diagnosed as affected by a zoonotic disease and those with lesions related to inflammatory diseases potentially transmissible to humans were selected. In order to identify the pathogenic agent, suspected cases were submitted to cultural, biomolecular and IHC investigation using frozen or formalin-fixed tissue and/or previously stored CSF. A total of 1560 cases were studied in the period from 2000 to 2009. In 660 animals (42%), traumatic, vascular, congenital, muscular and articular diseases were diagnosed by clinical examination, and no involvement of the CNS was found. In 353 subjects (23%), probable zoonoses were identified. In 82 of these, 73 dogs and 9 cats, showed neuropathological lesions suggestive of viral infections, whose origin was unknown and were therefore considered as “potential zoonoses”. In 337 cases (22%) were observed lesions not transmissible to humans such as neoplasia, toxic-metabolic, neurodegenerative and bacterial diseases, Distemper, FIV, FeLV, FIP, IBR, CAEV, Visna, Border Disease, and others, and therefore were not included in this study. In 194 cases (12%), no diagnosis was established because the case history was incomplete and/or tissues were unsuitable for biomolecular investigations. Sixteen animals (1%) showed no lesions. Overall, 16 zoonoses were detected in 271 animals of different species. In our investigation, among the many neurological cases potentially attributable to infectious agents, about 27% were confirmed as a zoonosis, but there remain many cases of inflammation not classified and potentially constituting a health risk. The results of this research show that animals can be an important reservoir for agents of neurozoonoses; therefore, monitoring of neurological diseases of animals should be designed to reduce the number of infections in humans and may be a good model for the study of therapeutic strategies in cases of infection. Neurozoonosis monitoring in animals may also allow for the surveillance of possible emerging or re-emerging infectious agents.