We report the isolation and characterization of 16 Leptospira spp. strains isolated from small rodents captured in 11 different regions of inland Croatia. Large NotI and SgrAI restriction fragment allowed us to assign 10 isolates to the serovar istrica, 5 isolates to the serovar tsaratsovo and 1 isolate to the serovar lora. The phylogenetic analysis conducted from the sequences of the first 330 bp from the 16S rDNA gene revealed that the strains belonged to three different species, L. borgpetersenii, L. kirschneri and L. interrogans. Carrier rates in eight rodent species varied from 0 to 71.4%. Mus musculus showed the highest infection level and confirmed its role as a major reservoir of the serogroup Sejroë. For the first time we reported the occurrence of serovars tsaratsovo and lora in Croatia.

Babesia divergens and B. divergens-like organisms are the main causative agents of human babesiosis in Europe. Recently, the first case of human infection with Babesia microti was confirmed in Germany, implicating the presence of zoonotic isolates. To estimate the presence of zoonotic B. microti in Croatia we analyzed 120 small wild mammals that serve as its reservoir by polymerase chain reaction. Yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) were both found to be infected with prevalence of 16.2%. Sequence analysis of the portion of 18S rDNA gene demonstrated that six polymerase chain reaction-positive samples, detected in both rodent species, were identical to that of the human Jena/Germany strain (EF413181). The other two isolates were identical to the nonzoonotic Munich strain (AB071177). The results of this study indicate the presence of zoonotic B. microti in A. flavicollis and M. glareolus in Croatia and a potential risk for human health.

Hantaviruses, Leptospira spp., and Babesia spp. are rodent-borne pathogens present worldwide. We studied multiple co-infections of small rodents in Croatia with all three pathogens. Twenty-eight Apodemus flavicollis and 16 Myodes glareolus were tested for the presence of hantavirus RNA by real-time RT-PCR, Leptospira strains by renoculture method and Babesia DNA by PCR. Anti-hantavirus antibodies and anti-Leptospira antibodies were detected by serological methods. Very high infection rates with each pathogen were found in A. flavicollis: 20 of 28 rodents (71%) were infected with Dobrava virus, 13 rodents (46%) were infected with Leptospira, and 5 rodents (18%) were infected with Babesia. Multiple co-infections with all three pathogens were found in 3 of 28 (11%) A. flavicollis animals, suggesting that the same rodent host can be infected with several pathogens at the same time. Dual infections with both hantaviruses and Leptospira were found in 7 of 44 rodents (16%), with hantaviruses and Babesia in 2 rodents (5%), and double infection with both Leptospira and Babesia were found in 1 rodent (2%). Since hantaviruses, Leptospira, and Babesia have similar geographical distributions, it is to be expected that in other parts of the world multiple co-infections, representing a serious threat to public health, can be found.

Abstract. Croatia is a focus for many rodent-borne zoonosis. Here, we report a survey of 242 rodents and small mammals, including 43 Myodes glareolus, 131 Apodemus flavicollis, 53 Apodemus agrarius, three Apodemus sylvaticus, six Sorex araneus, four Microtus arvalis, one Microtus agrestis, and one Muscardinus avellanarius, collected at eight sites in Croatia over an 8-year period. Multiplex MassTag polymerase chain reaction (PCR) was used for detection of Borrelia, Rickettsia, Bartonella, Babesia, Ehrlichia, Anaplasma, Francisella tularensis, and Coxiella burnetii. Individual PCR assays were used for detection of Leptospira, lymphocytic choriomeningitis virus, orthopoxviruses, flaviviruses, hantaviruses, and Toxoplasma gondii. Of the rodents, 52 (21.5%) were infected with Leptospira, 9 (3.7%) with Borrelia miyamotoi, 5 (2%) with Borrelia afzelii, 29 (12.0%) with Bartonella, 8 (3.3%) with Babesia microti, 2 (0.8%) with Ehrlichia, 4 (1.7%) with Anaplasma, 2 (0.8%) with F. tularensis, 43 (17.8%) with hantaviruses, and 1 (0.4%) with an orthopoxvirus. Other agents were not detected. Multiple infections were found in 32 rodents (13.2%): dual infections in 26 rodents (10.7%), triple infections in four rodents (2.9%), and quadruple infections in two rodents (0.8%). Our findings indicate that rodents in Croatia harbor a wide range of bacteria and viruses that are pathogenic to humans.

HFRS is an endemic disease throughout Croatia. The incidence of HFRS varies in a cyclic fashion, with peaks occurring every couple of years, coinciding with peaks in vole populations. PUUV was shown to be dominant pathogen during the last HFRS outbreak in Croatia in 2002. We focused our research on two newly discovered localities (Okucani and Nova Gradiska) with a high number of reported HFRS cases and a significant increase in rodent population. PUUV infection was verified in 84.2% of patients at this region during the 2002 outbreak. Genetic analysis of wild-type (wt) PUUV strains was performed. Fifty seven bank voles Clethrionomys glareolus originating from PUUV-associated HFRS areas were screened for the presence of PUUV N antigen and 15 (26%) were found positive. Total RNA isolated from rodent lung tissues was reverse transcribed followed by PCR amplification with primers specific for PUUV medium (M) or small (S) genome segments. Partial PUUV M segment sequences (approximately 450 bp long) were recovered from five bank voles and partial S segment sequences (app. 250 nt long)-from two bank voles. Genetic analysis of Croatian wt-PUUV strains revealed their close relatedness suggesting that the two localities belong to the same natural focus of infection. On phylogenetic trees Croatian PUUV strains clustered together with the strains from Slovenia and Austria forming distinct Alpe-Adrian genetic lineage.