Zoonotic Helminths of Urban B rown Rats ( R attus norvegicus ) in the UK : Neglected Public Health Considerations?

Summary Urban brown rats ( R attus norvegicus ) carry microbial human pathogens but their role as reservoir hosts for helminths of public health importance is less well known. In this study, 42 brown rats trapped on M erseyside were subject to thorough combined helminthological and pathohistological post‐mortem examination. Eggs of the rodent‐borne zoonotic nematode C alodium hepaticum were initially detected in histological sections of the livers of 9.5% of rats, but overall diagnostic sensitivity increased to 16.6% when entire liver tissue was disrupted and the resulting filtrates were examined for released eggs. In their rat host, mainly trapped inside the dockland, infections with C . hepaticum were associated with a chronic multifocal pyogranulomatous hepatitis with intralesional eggs and peripheral fibrosis. Mean intensity of hepatic C . hepaticum egg infections was 1041 eggs. This is the first report of C . hepaticum in an urban brown rat population in the UK and provides original data for liver egg burdens in this abundant commensal rodent. The zoonotic cestode R odentolepis nana had a prevalence of infection of 14.3%. Rodent‐specific, non‐zoonotic helminths found were the spiruroid M astophorus muris (16.0%) in the stomach, the trichuroid T richosomoides crassicauda in the urinary bladder (31.0%); the ascarid H eterakis spumosa was the commonest helminth of the large intestine (76.2%). Many millions of brown rats inhabit cities and rural areas of the UK , and the infective stages of the zoonotic worm species, particularly C . hepaticum, are likely to be widely distributed in the environment presenting a threat to public health.