The importance of study duration and spatial scale in pathogen detection—evidence from a tick-infested island

Figures & data

Annual prevalence of tick-borne pathogens in nymph and adult Ixodes ricinus from Seili Island

	Study year
	2012	2013	2014	2015	2016	2017	Total^a
Nymphs analyzed	437	227	400	275	535	495	1932
Adults analyzed	44	19	27	38	35	19	182
Pathogen species/groups:
Borrelia burgdorferi sensu lato
Nymphs (prevalence)	30 (6.7)^b	37 (16.3)	76 (19.0)	48 (17.5)	93 (17.4)	119 (24.0)	373 (19.3)
Adults (prevalence)	11 (25.0)	5 (26.3)	9 (33.3)	5 (13.2)	6 (17.1)	10 (52.6)	46 (25.3)
Borrelia miyamotoi
Nymphs	2 (0.5)^b	3 (1.3)	1 (0.3)	2 (0.7)	3 (0.6)	4 (0.8)	13 (0.7)
Adults	0	0	1 (3.7)	1 (2.6)	0	0	2 (1.1)
Anaplasma phagocytophilum
Nymphs	4 (0.9)^b	11 (4.9)	6 (1.5)	7 (2.5)	23 (4.3)	18 (3.6)	65 (3.4)
Adults	2 (4.5)	3 (15.8)	3 (11.1)	2 (6.3)	6 (17.1)	2 (10.5)	18 (9.9)
Rickettsia spp.
Nymphs	17 (3.9)^b	4 (1.8)	9 (2.3)	1 (0.4)	10 (1.9)	12 (2.4)	36 (1.9)
Adults	1 (2.3)	0	0	3 (7.9)	2 (5.7)	0	6 (3.3)
Babesia spp.
Nymphs	1 (0.2)^b	3 (1.3)	7 (1.8)	2 (0.7)	9 (1.7)	4 (0.8)	25 (1.3)
Adults	0	0	2 (7.4)	0	0	0	2 (1.1)
Candidatus Neoehrlichia mikurensis
Nymphs	0	0	0	5 (1.8)	23 (4.3)	9 (1.8)	37 (1.9)
Adults	0	0	0	0	0	0	0
Tick-borne encephalitis virus
Nymphs	0	0	0	0	3 (0.6)	4 (0.8)	7 (0.4)
Adults	0	0	0	0	0	0	0
Bartonella spp.
Nymphs	0	0	0	0	0	0	0
Adults	0	0	0	0	0	0	0

^a2012 nymph samples were excluded from calculations

^bMost nymph samples in 2012 were pooled; the number in brackets is the minimum infection rate

Annual minimum infection rates (MIR) for tick-borne pathogens detected in I. ricinus larvae from Seili Island

	Study year
	2012	2013	2014	2015	2016	2017	Total
Larvae analyzed^a	1281	374	635	342	575	1311	4518
Pathogen species^b:
Rickettsia spp.
Positive samples (MIR^c)	14 (1.1)	2 (0.5)	0 (0)	1 (0.3)	4 (0.7)	16 (1.2)	37 (0.8)
Babesia spp.
Positive samples (MIR^c)	0 (0)	2 (0.5)	2 (0.3)	1 (0.3)	4 (0.7)	5 (0.4)	14 (0.3)
Borrelia miyamotoi
Positive samples (MIR^c)	0 (0)	0 (0)	0 (0)	0 (0)	1 (0.2)	2 (0.2)	3 (0.1)

^aLarvae samples were pools of 1–111 (years 2012–2014) or 1–24 (years 2015–2017) larvae

^bAll larvae samples were negative for B. burgdorferi s.l., Bartonella spp., C. N. mikurensis, A. phagocytophilum, and TBEV

^cMinimum infection rate (estimated one positive individual per positive pool)

Co-infections and associated prevalence detected in individual I. ricinus nymphs and adults from Seili Island

Year	Life stage^a	Pathogen pairs
		Bbsl^b & CNe^b	Bbsl^b & Rickettsia	Bbsl^b & TBEV^b	Bbsl^b & Babesia	Bbsl^b & Anaplasma	Anaplasma & Rickettsia	Babesia & CNe^b
2012	N	0	1 (0.2)	0	0	0	0	0
	A	0	1 (2.3)	0	0	0	0	0
2013	N	0	1 (0.4)	0	0	1 (0.4)	1 (0.4)	0
	A	0	0	0	0	0	0	0
2014	N	0	1 (0.3)	0	1 (0.3)	0	0	0
	A	0	0	0	2 (7.4)	1 (3.7)	0	0
2015	N	4 (1.5)	1 (0.4)	0	0	0	0	0
	A	0	1 (2.6)	0	0	0	0	0
2016	N	9 (1.7)	1 (0.2)	1 (0.2)	3 (0.6)	0	2 (0.4)	1 (0.2)
	A	0	0	0	0	0	0	0
2017	N	3 (0.6)	0	3 (0.6)	1 (0.2)	1 (0.2)	0	0
	A	0	0	0	0	2 (10.5)	0	0
Total	N	16 (0.8)	5 (0.3)	4 (0.2)	5 (0.3)	2 (0.1)	3 (0.2)	1 (0.1)
	A	0	2 (1.1)	0	2 (1.1)	3 (1.6)	0	0

N nymphs, A  adults, BbslBorrelia burgdorferi sensu lato, CNeCandidatus Neoehrlichia mikurensis, TBEV tick-borne encephalitis virus

^aN, A

^bBbsl,CNe, TBEV

Fig. 1 Estimated probabilities (with 95% confidence limits) of nymph samples being positive for B. burgdorferi s.l. (a) and A. phagocytophilum (b) across biotopes, as predicted by the GLMM. Different biotope classes were assigned matching letters when no statistically significant differences between them could be identified (p > 0.05; multiple pairwise comparisons adjusted by Tukey test). Mismatching letters denote statistically significant differences between biotope classes with different letters (p < 0.05)

Fig. 2 Estimated probabilities (with 95% confidence limits) of nymph samples being positive for B. burgdorferi s.l. (a, c), A. phagocytophilum (b), Rickettsia (d), and Ca. N. mikurensis (e) within biotopes (across transects), as predicted by the GLMM. Different transects were assigned matching letters when no statistically significant differences between them could be identified (p > 0.05; multiple pairwise comparisons adjusted by Tukey test). Mismatching letters denote statistically significant differences between transects with different letters (p < 0.05). C_1-3, transects in coniferous forest; D_1-3, transects in deciduous forest

Fig. 3 Study location.

The location of the study area, Seili Island, in the Archipelago Sea, SW Finland

Fig. 4 Study transects on Seili Island. Three transects were assigned to each biotope type, denoted with letter and number combinations.

C coniferous forest, D deciduous forest, A alder thicket, M meadow, P pasture. The Archipelago Research Institute is located in the middle of the island