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Table 1 Results of two questionnaire studies, carried out in 1994 [14] and 2009 (this study), referring to changes in tick presence/absence and changes in tick abundance in different geographical regions of Sweden.

From: Changes in the geographical distribution and abundance of the tick Ixodes ricinus during the past 30 years in Sweden

 

Survey of 1994

Data from questions asked during 1994 and published in [14].

Survey of 2009

Data from questions asked during 2009.

Region (and provinces abbreviated)

Ticks present

early 1980s

n/N

Ticks present

1993

n/N

Change, %

No. respondents

(N)

Ticks present early 1990s

n/N

Ticks present 2008

n/N

Change,

%

"Ticks have become more numerous since early 1990s"

% yes

No.

respondents

(N)

Northern North Sweden

(NB, LP)

4.9%

2/41

26.8%

11/41

+22a

(0.168)

41

9.5%

6/63

73.0%

46/63

+63b

(0.021)

71.4a

(< 0.001)

63

Central North Sweden

(HR, ME,ÅN, JÄ, VB)

10.9%

17/156

42.3%

66/156

+31b

(0.004)

156

14.8%

9/61

90.2%

55/61

+75b

(0.004)

86.9b

(< 0.001)

61

Southern North Sweden

(DR, GÄ, HS)

33.8%

93/275

72.4%

199/275

+39b

(0.058)

275

33.3%

26/78

97.4%

76/78

+64b

(0.005)

93.6b

(< 0.001)

78

Central Sweden

(DS, VR, VS, NÄ, SÖ, UP)

77.4%

564/729

98.1%

715/729

+21a

(0.010)

729

68.6%

253/369

99.7%

368/369

+31a

(0.003)

91.3b

(< 0.001)

369

South Sweden: West Coast

(HA, VG, BO)

N.D.

N.D.

N.D.

N.D.

64.5%

122/189

98.9%

187/189

+34a

(0.009)

88.8b

(< 0.001)

189

South Sweden: Baltic islands (ÖL, GO)

N.D.

N.D.

N.D.

N.D.

80.0%

20/25

100.0%

25/25

+20a

(0.052))

68.0a

(< 0.079)

25

Southern South Sweden

(SK, BL, SM,ÖG)

N.D.

N.D.

N.D.

N.D.

67.6%

167/247

99.2%

245/247

+32a

(0.024)

86.2b

(< 0.001)

247

All regions

*1201: only the 4 northernmost regions, i.e. Central, S. North, C. North and N. North

__

__

+29

(0.001)

1201*

58.4%

603/1032

97.1%

1002/103

+39

(0.001)

87.7

1,032

  1. n = number respondents who answered "yes, ticks are/were present within 1 km from where I live" at that particular time (year), e.g. early 1980s or 1993 (= study of 1994), or early 1990s or 2008 = this study of 2009). N = total number of respondents in the region who answered the questionnaire. Values for % change appear in one column for each time period (early 1980s-1993 and early 1990s-2008); % change values in a column and denoted with the same letter (a or b) are not significantly different at the 5% level according to generalized linear model (binomial distribution). The value in parentheses under each value of % change shows the level of significance of the % change according to paired t-test. N.D. = not done. The next to last column shows the percentage of respondents, for each region in the study of 2009, who stated that "ticks had increased in numbers" (i.e. tick abundance had increased) during the last 16 years, in the respondents' residential areas. Thus, the percentages, in the next to last column, refer to % of respondents that replied "more numerous" to the question "Have ticks become more numerous, less numerous or have they not changed their abundance since the early 1990s in the area where you live?" *Not "All regions" The data on "% yes" were analyzed by the same statistical methods as the "% change" data
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Parasites & Vectors

ISSN: 1756-3305

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