Ranging behaviour and pattern of infection with the tick I. ricinus of the yellow necked mouse (Apodemus flavicollis) in northern Italy

The rodent Apodemus flavicollis plays a central role in the ecology of Tick Borne Encephalitis (TBE) as amplifying host for the virus through non-viraemic transmission between co-feeding ticks, especially I. ricinus. To assess the factors affecting the abundance and pattern of tick infestation on this species, we carried out a longitudinal study in an endemic tick-borne diseases site in the province of Trento, northern Italy (grid reference: 1652050E 5093750N). The field trial was based on capture-mark-recapture technique: between April and November 2000, a total of 297 A. flavicollis were trapped and individually marked in four grids of 64 traps (1 grid = 1.41 ha). Ticks showed an aggregated distribution among hosts: about 20% of the rodents, mostly adult males, carried most of the larvae and the co-feeding groups recorded. To analyse the effect of host spatial behaviour on tick burden, we measured the home range size and overlap of 45 individuals (26 males and 19 females) which were recaptured at least 10 times. The mean tick abundance recorded on these individuals was higher in males (mean larvae burden= 12.53 ± 0.93; mean nymphs burden = 0.13 ± 0.03) than in females (mean larvae burden = 9.48 ± 0.65; mean nymphs burden = 0.04 ± 0.02) (p<0.05). The relation between host characteristics, individual habitat use and tick infection patterns are discussed.