SEROLOGICAL EVIDENCE OF LEPTOSPIRA SPP . IN THE LAMI TUCO-TUCO RODENTS ( CTENOMYS LAMI )

Although rodents are reportedly the major reservoirs of Leptospira spp. in the wildlife of Brazil, the role of the widely distributed native tuco-tuco rodent (Ctenomys lami) has yet to be determined. Accordingly, a total of 40 serum and eight urine samples from wild C. lami were collected from June to September 2008 in the city of Porto Alegre, Southern Brazil. The serum samples were screened using the Microscopic Agglutination Test against 13 Leptospira spp. pathogenic serovars. A polymerase chain reaction (PCR) was performed to detect the presence of leptospiral DNA in the urine samples. Five (12.5%) of the serum samples had >100 antibody titer levels against one or more of the serovars. None of the urine samples yielded positive PCR amplification. In addition, all animals which had urine samples tested had also negative antibody serum titers. In conclusion, although C. lami may be exposed to Leptospira spp., infection may be occasional because no detectable leptospiruria was found.


INTRODUCTION
Leptospirosis is a zoonotic bacterial disease that may infect humans and domestic and wild animal species.Rodents have been considered important reservoirs of pathogenic Leptospira serovars (LEVETT, 2001).Although the control of rodents may decrease the risk of transmission to incidental hosts and environmental contamination, environmental maintenance of pathogenic Leptospira spp.causes the spread of leptospirosis in wild animals (GUERRA, 2009).
The tuco-tucos are fossorial rodents belonging to the genus Ctenomys in the family Ctenomyidae, which includes nearly 60 species.They are distributed throughout the southern half of South America (REIG et al., 1990).Lami tuco-tuco (Ctenomys lami) is distributed along a sandy area (Coxilha das Lombas) of Southern Brazil, spreading from the northern coast of Lake Guaíba to an area northwest of the Lagoa dos Barros (FREITAS, 2001).Even though some of these areas are environmentally protected, they are under anthropic impact due to the surrounding livestock production.To the authors' knowledge, there are no published data regarding the occurrence of leptospirosis in C. lami.Accordingly, the aim of this study was to detect evidence of exposure of wild Lami tucotucos to Leptospira spp.The Lami tuco-tucos were weighed and anesthetized with intramuscular ketamine (20 mg/kg of body weight).All animals were evaluated and considered to be clinically healthy.Blood was collected from the cranial vena cava, kept in tubes without anticoagulant at room temperature and subsequently centrifuged to obtain serum.Urine samples were successfully collected from eight animals using gentle abdominal hand pressure.After anesthetic recuperation, all animals were released in their respective native tunnels.
DNA from the urine samples was extracted in duplicate (LUCCHESI et al., 2004) and a conventional polymerase chain reaction (PCR) was performed to detect pathogenic leptospires using the primer sets G1/G2 and B64-I/B64-II (GRAVEKAMP et al., 1993).Positives urines from dogs for both primer sets and DNA extracted from leptospire's cultures were used as positive controls and included in each run.
serovar wolffi and one sample had equal titers for the serovars wolffi, hardjo and icterohaemorrhagiae.One sample from area B was seropositive for the serovars copenhageni, grippotyphosa, pomona and pyrogenes.From area C, one sample was positive for the serovar pomona.
All urine samples tested negative on the PCR amplification.All eight rodents were seronegative as well.

DISCUSSION
To the authors' knowledge, this is the first report of an investigation of leptospirosis in C. lami using serology and PCR.The positive serological results indicated that the C. lami had contact with pathogenic leptospires.The source of contamination was unclear, but possible contact with cattle, small mammals or contaminated water should be considered.
Although all of the PCR analyses in urine were negative, the possibility of leptospirosis transmission by C. lami cannot be discounted.Moreover, other members of the infraorder Hystricognathi (WILSON & REEDER, 2005) have been reported to have had positive culture/isolation of leptospires in their kidneys and/or urine: the coypu (Myocastor coypus) in France (MICHEL et al., 2001) and in Great Britain (WAITKINS et al., 1985) and the capybara (Hydrochaeris hydrochaeris) in Brazil (Marvulo et al., 2002, MARVULO et al., 2009, JORGE et al., 2010).

CONCLUSION
Although C. lami may be exposed to Leptospira spp., infection may be occasional because no detectable leptospiruria was found.Whether the tuco-tuco rodents act as reservoirs of the disease remains to be conclusively established.