Grahamella in small woodland mammals in the U.K.: isolation, prevalence and host specificity.

Bacteria isolated from the blood of small woodland mammals were identified as members of the genus Grahamella. The prevalence of Grahamella infection among the 37 small mammals examined, detected by cultivation of blood samples, was 62%. This figure is somewhat higher than previous reports. Further characterization of the isolates, based on restriction enzyme analysis of the 16S rRNA gene, serological reactivity and DNA hybridization studies, revealed three distinct Grahamella species. One of the species was found in five different species of small mammal (Apodemus sylvaticus, A. flavicollis, Clethrionomys glareolus, Microtus agrestis and Neomys fodiens). All three species were found in M. agrestis, although there was no evidence of concurrent infection of an animal by more than one species of Grahamella. These observations demonstrate that Grahamella spp. are not host-specific, as previously thought, and that it is therefore invalid to name Grahamella spp. solely on the basis of the host in which they are observed.

Infections with blood parasites in the small British rodents Apodemus sylvaticus, Clethrionomys glareolus and Microtus agrestis.

Three populations of small wild British rodents were studied by capture-recapture methods over a period of 3 years, a fourth group was studied for 1 year and a fifth was sampled annually for 4 years. Blood smears were taken from 3 species of rodents: the woodmouse Apodemus sylvaticus, the bank vole Clethrionomys glareolus (and an island sub-species C.g. skomerensis) and the short-tailed vole Microtus agrestis. The smears were examined microscopically. Four genera of haemoparasites Babesia, Hepatozoon, Trypanosoma and Grahamella were detected. Babesia was absent from C.g. skomerensis, Hepatozoon was rarely found in A. sylvaticus and M. agrestis and Trypanosoma was rare in A. sylvaticus. More males were infected than females but the difference was only statistically significant for the infection with Hepatozoon in adult C.g. skomerensis. Infections with Babesia and Hepatozoon were more prevalent in adult animals and infections with Trypanosoma were more prevalent in younger individuals. Only in C.g. skomerensis was there a significant difference between age classes in the prevalence of infection with Grahamella--there being more adults infected. Concurrent infections were detected, Hepatozoon being the parasite most commonly involved. The prevalence of infections was found to be approximately proportional to the number of animals known to be alive, regardless of the season.