Sarah M. Hazel

Cowpox: reservoir hosts and geographic range.

It is generally accepted that the reservoir hosts of cowpox virus are wild rodents, although direct evidence for this is lacking for much of the viruss geographic range. Here, through a combination of serology and PCR, we demonstrate conclusively that the main hosts in Great Britain are bank voles, wood mice and short-tailed field voles. However, we also suggest that wood mice may not be able to maintain infection alone, explaining the absence of cowpox from Ireland where voles are generally not found. Infection in wild rodents varies seasonally, and this variation probably underlies the marked seasonal incidence of infection in accidental hosts such as humans and domestic cats.

Transmission dynamics of a zoonotic pathogen within and between wildlife host species

The transmission dynamics of the cowpox virus infection have been quantified in two mixed populations of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus), through analyses of detailed time-series of the numbers of susceptible, infectious and newly infected individuals. The cowpox virus is a zoonosis which circulates in these rodent hosts and has been shown to have an adverse effect on reproductive output. The transmission dynamics within species is best described as frequency dependent rather than density dependent, contrary to the ‘mass action’ assumption of most previous studies, both theoretical and empirical. Estimation of a transmission coefficient for each species in each population also allows annual and seasonal variations in transmission dynamics to be investigated through an analysis of regression residuals. Transmission between host species is found to be negligible despite their close co–habitation. The consequences of this for the combining ability of hosts as zoonotic reservoirs, and for apparent competition between hosts, are discussed.

Antibiotic resistance found in wild rodents

Resistance to antibiotics is an increasingly common problem in both veterinary and human medicine, and its management is the subject of urgent debate. Efforts to reduce this resistance are based on the assumption that it is maintained in bacterial populations as a result of exposure to antibiotics, and that restricting the use of antibiotics should therefore restrain the spread of resistance. But we have found that antibiotic resistance is prevalent in populations of wild rodents that have not been exposed to antibiotics, indicating that approaches to control it based on this assumption may be overoptimistic.

Enterobacteria - Antibiotic resistance found in wild rodents

Resistance to antibiotics is an increasingly common problem in both veterinary and human medicine, and its management is the subject of urgent debate. Efforts to reduce this resistance are based on the assumption that it is maintained in bacterial populations as a result of exposure to antibiotics, and that restricting the use of antibiotics should therefore restrain the spread of resistance. But we have found that antibiotic resistance is prevalent in populations of wild rodents that have not been exposed to antibiotics, indicating that approaches to control it based on this assumption may be overoptimistic.

Longitudinal monitoring of the dynamics of infections due to Bartonella species in UK woodland rodents.

Blood samples were repeatedly collected from 12 sympatric woodland rodents over a 12-month period and DNA extracts from each were incorporated into a bartonella-specific PCR targeting a fragment of the 16S/23S rRNA intergenic spacer region (ISR). The composition of each amplicon was analysed using restriction enzyme analysis (REA) and base sequence comparison. Bartonella DNA was detected in 70 of 109 samples. Eleven samples contained DNA derived from more than one strain. Sequence analysis of 62 samples found 12 sequence variants (ISR genotypes) that were provisionally assigned to 5 different species, 2 of which were newly recognized. Up to five different species were detected in each animal. On about two-thirds of occasions, a species detected I month was not there the next, but never was a genotype superseded by another of the same species. However, a genotype could be re-encountered months later in the same animal, even if interim samples contained other genotypes. Our results suggest that although most animals are bacteraemic most of the time, specific infections are often superseded and that a complex and dynamic epidemiology of bartonella bacteraemias exists in woodland rodents.

A longitudinal study of an endemic disease in its wildlife reservoir: cowpox and wild rodents.

Cowpox is an orthopoxvirus infection endemic in European wild rodents, but with a wide host range including human beings. In this longitudinal study we examined cowpox in two wild rodent species, bank voles Clethrionomys glareolus and wood mice Apodemus sylvaticus, to investigate the dynamics of a virus in its wild reservoir host. Trapping was carried out at 4-weekly intervals over 3 years and each animal caught was uniquely identified, blood sampled and tested for antibodies to cowpox. Antibody prevalence was higher in bank voles than in wood mice and seroconversion varied seasonally, with peaks in autumn. Infection was most common in males of both species but no clear association with age was demonstrated. This study provides a model for studying other zoonotic infections that derive from wild mammals since other approaches, such as one-off samples, will fail to detect the variation in infection and thus, risk to human health, demonstrated here.

Excretion of vancomycin-resistant enterococci by wild mammals.

A survey of fecal samples found enterococcal excretion in 82% of 388 bank voles (Clethrionomys glareolus), 92% of 131 woodmice (Apodemus sylvaticus), and 75% of 165 badgers (Meles meles). Vancomycin-resistant enterococci, all Enterococcus faecium of vanA genotype, were excreted by 4.6% of the woodmice and 1.2% of the badgers, but by none of the bank voles.

Nontyphoidal Salmonellae in United Kingdom Badgers: Prevalence and Spatial Distribution

ABSTRACT Eighteen (72%) of 25 badger social groups were found to excrete Salmonella enterica serovar Ried, S. enterica serovar Binza, S. enterica serovar Agama, or S. enterica serovar Lomita. Each serovar was susceptible to a panel of antimicrobials. Based on results of pulsed-field gel electrophoresis, the S. enterica serovar Agama and S. enterica serovar Binza isolates were very similar, but two clones each of S. enterica serovar Lomita and S. enterica serovar Ried were found. Badgers excreting S. enterica serovar Agama were spatially clustered.

Inference of cowpox virus transmission rates between wild rodent host classes using space–time interaction

There have been virtually no studies of ‘who acquires infection from whom’ in wildlife populations, but patterns of transmission within and between different classes of host are likely to be reflected in the spatiotemporal distribution of infection among those host classes. Here, we use a modified form of K-function analysis to test for space–time interaction among bank voles and wood mice infectious with cowpox virus. There was no evidence for transmission between the two host species, supporting previous evidence that they act as separate reservoirs for cowpox. Among wood mice, results suggested that transmission took place primarily between individuals of the opposite sex, raising the possibility that cowpox is sexually transmitted in this species. Results for bank voles indicated that infected females might be a more important source of infection to either sex than are males. The suggestion of different modes of transmission in the two species is itself consistent with the apparent absence of transmission between species.

Antibiotic resistance found in wild rodents: Enterobacteria

Resistance to antibiotics is an increasingly common problem in both veterinary and human medicine, and its management is the subject of urgent debate. Efforts to reduce this resistance are based on the assumption that it is maintained in bacterial populations as a result of exposure to antibiotics, and that restricting the use of antibiotics should therefore restrain the spread of resistance. But we have found that antibiotic resistance is prevalent in populations of wild rodents that have not been exposed to antibiotics, indicating that approaches to control it based on this assumption may be overoptimistic.