Browsing by Author "Suomalainen, Nina"

The brown rat (Rattus norvegicus) is a common rodent species found worldwide, especially in urban areas where they cohabit very closely with humans. Known as reservoirs for several zoonotic pathogens and parasites, rats present a significant risk to public health. Despite the concern, studies on rat-borne pathogens in Finland have been limited. This thesis aims to address the gap by focusing on two major zoonotic pathogens in rats, Leptospira spp. and hepatitis E virus. Leptospirosis is a zoonotic disease caused by a spirochete bacterium of the genus Leptospira. Hepatitis E virus is a common cause of acute hepatitis in tropical and subtropical countries, and rat specific hepatitis E virus, Rocahepevirus ratti, is a potential emerging zoonotic pathogen. The aim of the study was to discover if the zoonotic pathogens Leptospira spp. and hepatitis E virus are present in urban rat populations in Helsinki. This was achieved by molecular detection of Leptospira and hepatitis E virus from rat tissue samples. The rat carcasses in this study were received from pest management operators and citizens of Helsinki between 2018 and 2023. Rat antibodies against hepatitis E virus were also attempted to study with commercial ELISA. The PCR positive samples were studied further with either Sanger sequencing or Next-generation sequencing (NGS). Both pathogens were observed in this study. Leptospira spp. was found in 1.23 % of the rat samples studied. Sequence analysis of the Sanger sequenced PCR product suggested that the species was Leptospira interrogans. Rat hepatitis E virus, Rocahepevirus ratti, was observed for the first time in Finland, in 1.79 % of the studied rats. NGS confirmed the virus and phylogenetic analysis showed high homology with sequences of Rocahepevirus ratti genotype C1 from around the world. Even though both pathogens were found in lower quantities than expected, further research and surveillance is needed to estimate the real prevalence and the potential risk for human and animal health.