Introduction
Opossums (Didelphis spp.) are neotropical marsupials of the order Didelphimorphia, family Didelphidae. Among the species that occur in Brazil, two can be easily found in the great Brazilian biomes, D. aurita (black-eared opossum) and D. albiventris (white-eared opossum) (Aléssio et al., 2005; Moura et al., 2009; Paglia et al., 2012). These mammals have opportunistic habits, and can live in wild, rural and urban environments, maintaining contact with other animals and human beings (Lucheis et al., 2009; Tarragona et al., 2011). Notably, white-eared opossum is widely distributed in Brazilian biomes and is strongly adapted to highly degraded areas, as well as urban forest fragments (Aléssio et al., 2005).
This type of behavior, called synanthropic, places opossums as a key group in the connection between wild and domestic epidemiological cycle of emerging parasites and microorganisms (Forzanari et al., 2011; Tarragona et al., 2011). For example, opossums and its most common ectoparasite, Ctenocephalis felis flea, have been epidemiologically linked to flea-borne pathogens transmission and human-wild life conflicts in residential environments (Krueger et al., 2016).
Studies support that cat flea (C. felis ) is the major competent vector for Bartonella henselae , B. clarridgeae , B. koehlerae , and potentially B. quintana (Pennisi et al., 2013; Zangwill, 2013). Those species among others belong to the α-proteobacteria, are hemotropic, short and pleomorphic Gram-negative bacteria that cause intra-erythrocytic infections in animals and humans (Jacomo et al., 2002; Deng et al., 2012). Bartonella species appear to be highly adapted to one or few reservoir hosts, within which these bacteria have coevolved and thence remain for long periods in bloodstream (Kaiser et al., 2011; Harms and Dehio, 2012).
Until 1990, only two diseases were linked to Bartonella species, Carrión disease (B. bacilliformis ) and Trench fever (B. quintana ) (Karem et al., 2000). Since then, many other Bartonellae have been identified as causative agents of diseases in animals and humans (Iannino et al., 2018). Importantly, the list of mammalian-adaptedBartonella species continues to grow, as well as the number of human disease associated with genus Bartonella (Kaiser et al., 2011; Harms and Dehio, 2012; Buffet et al., 2013).
Currently, Cat-scratch disease (CSD) is the most common human disease caused by Bartonella species, including B. henselae , andB. clarridgeiae (Iannino et al., 2018). Clinical manifestation of CSD depends on patient immune status, and pet cats and dogs often develop similar manifestations as humans (Chomel et al., 2009; Breitschwerdt et al., 2010; Beerlage et al., 2012). Typical CSD denotes a self-limiting illness characterized by fever and lymphadenopathy; however, atypical manifestations can occur (Jacomo et al., 2002; Breitschwerdt et al., 2010; Zangwill, 2013).
Bartonella genus has already been isolated or detected in domestic and wild animals worldwide, including bats, birds, canids, cattle, deer, felids, horses, marine mammals, rodents, sheep and reptiles (Deng et al., 2012). Little is known about wild reservoirs of these bacteria in Brazil, but recently, a study reported B. henselae and B. clarridgeiae in domestic cats from an Atlantic Forest area of Rio de Janeiro state (RJ), where humans, domestic, synanthropic and wild animals can easily interact (Silva et al., 2019). Opossums are often identified as likely maintainers of infectious agents with zoonotic potential (Abel et al., 2000; Ruiz-Piñaand Cruz-Reyes, 2002; Fornazari et al., 2011; Pena et al., 2011).
Considering the growing spectrum of animal reservoir hosts forBartonella species, and given the presence of Bartonellaspp. in RJ state, this study aimed to evaluate natural infections by those bacteria in free-ranging opossums that lived in peri-urban areas of the Atlantic Forest of RJ, Brazil.