Epsilon Archive for Student Projects

Abstract

On a global scale, zoonotic vector-borne diseases pose an increasing threat towards human
health. In Europe, the haemotophagous ectoparasite sheep tick (Ixodes ricinus) acts as a
pathogen vector for diseases like tick-borne encephalitis and Lyme disease with increasing
annual incidences during the last decades. In 2015, Lyme borreliosis was ranked in the top
ten priority group of pathogens to guide resource allocation within the Public Health
Agency of Sweden. Borrelia burgdorferi sensu lato (s.l) is the pathogen that causes Lyme
disease in humans and animals and is maintained in the wild by a complex multi-species
transmission process involving tick vectors and many different vertebrate hosts, including
humans as dead-end hosts. In Sweden, the relation between B. burgdorferi s.l. prevalence in
rodents and ungulate abundance is unknown. In this study, the prevalence of B. burgdorferi
s.l. in rodents (Yellow-necked mouse (Apodemus flavicollis), wood mouse (Apodemus
sylvaticus) and bank vole (Myodes glareolus), was evaluated in Gnesta/Nyköping (G/N) and
Växjö/Vetlanda (V/V), with varying abundances of wild ungulates as moose (Alces alces),
roe deer (Capreolus capreolus), red deer (Cervus elaphus) and fallow deer (Dama dama).
Rodent data and ungulate population density data were based on data collected by the
National Environmental and Wildlife Monitoring and Assessment program at SLU.
Prevalence of B. burgdorferi in rodents were analysed with real-time quantitative
polymerase chain reaction. The results show equal B. burgdorferi s.l. prevalence in the two
study regions (22%), but between species, M. glareolus showed a significantly higher
prevalence (26%) compared to Apodemus spp. (15%). B. burgdorferi s.l.. Overall, the
infection probability analysis revealed a higher risk for M. glareolus of getting infected than
Apodemus spp. However, when comparing infection probability between species in each
region, these same results were found for the V/V area, but were contradictory within the
G/N reg. The probability of infection also increased with body mass in rodents. Most
importantly, the infection probability analysis revealed that deer species such as roe deer
and fallow deer did not significantly influence infection probability in rodents. In
conclusion, the dataset for prevalence and infection probability analysis, should have been
larger to obtain greater statistical power. Also, the method using external oligonucleotides
as standard curve reference, are in need of a scientific evaluation.