The impact of intensity of invasion of Ixodes ricinus and Dermacentor reticulatus on the course of the parasitic phase.

Investigations into the effect of the intensity of invasion on tick-questing behaviour were conducted on 3 groups of rabbits: 1) 10 females and 5 males, 2) 20 females and 10 males, 3) 40 females and 20 males in the case of I. ricinus, whereas in the case of D. reticulatus, another three groups were used: 1) 10 females and 15 males, 2) 20 females and 15 males, 3) 40 females and 15 males. Given the different invasion intensities, no significant difference was found in the time of attachment to the host (p=0.3773) or in the feeding period (p=0.1051) for Ixodes ricinus females. In turn, body weight of engorged females exhibited highly significant differences (p=0.0021) between the groups, particularly in the least (0.3551±0.0739 mg) (p=0.0027) and most numerous groups (0.2752±0.0964 g) (p=0.0017). In the case of D. reticulatus, the length of the skin attachment period did not show statistically significant differences (p=0.4036) between the groups consisting of different numbers of ticks. However, invasion intensity had a statistically significant effect of the length of the feeding period (p=0.0037). In the least numerous female group, the length of the feeding period was significantly lower than in the groups composed of 20 (p=0.0091) and 40 (p=0.0042) specimens. No significant differences in the length of the feeding period (p=1.0000) were found between the most numerous groups of 20 and 40 females. The body weight in engorged females of this species exhibited highly significant differences (p=0.0006) in the most numerous group (0.2511±0.1135), and in the other groups (0.3559±0.0654 and 0.3554±0.0380 mg, respectively, in the invasion of 20 and 10 females). Both the investigated species showed highly significant differences in the attachment period in the groups with 20 (p=0.0017) and 40 (p<0.0001) females, and in the feeding period in all the experimental groups: (p=0.0001), (p<0.0001) and (p=0.0088), respectively. Furthermore, decreased feeding success and 12.5% female death were reported from the most numerous group of I. ricinus females. The differences between the feeding course in I. ricinus and D. reticulatus may be explained by the presence of various interactions in the parasite-host system at the different intensities of invasion by the 2 tick species.