Table 2.

Detection of B. microti group-specific rRNA gene by PCR in the field-collected ticks

Tick species	Survey area	Tick stage	No. of ticks examined	No. of ticks pooled	No. of ticks tested	No. of PCR-positive samples	Minimum infection rate (%)a
I. ovatus	Hokkaido Island
	Nemuro	Adult	48	2 to 3	19	4	8.3b
	Kiyosato	Adult	65	5	13	8	12.3
	Shimokawa	Adult	100	5	20	2	2.0
	Aibetsu	Adult	85	5	17	0	0
	Furano	Adult	115	5	23	3	2.6
	Hobetsu	Adult	140	5	28	10	7.1
	Ebetsu	Adult	36	3	12	0	0
	Chitose	Adult	68	4 to 5	15	0	0
	Awaji Island
	Sumoto	Adult	180	5	36	11	6.1
	Subtotal		789		183	38
I. persulcatus	Hokkaido Island
	Nemuro	Adult	139	3 to 5	33	2	1.4
		Nymph	196	1	196	0	0
	Horonobe	Adult	42	3	14	0	0
	Kiyosato	Adult	105	5	21	0	0
	Shimokawa	Adult	15	5	3	0	0
	Aibetsu	Adult	85	5	17	0	0
	Furano	Adult	44	5	15	0	0
	Hobetsu	Adult	36	33	13	0	0
	Ebetsu	Adult	15	5	3	0	0
	Subtotal		677		315	2	0.3
Other tick species	Six areasc	Adult	162		162	0	0
Total			1,656		542	40	2.4

^aValues (%) were calculated by comparing the number of pools that were PCR positive for the B. microti group to the total number of ticks examined. The calculation was based on the assumption that each PCR-positive pool contains at least one tick with a detectable B. microti group parasite(s).

^bConsidering the impact of the comparison of MIRs, the possible MIR would be between 2 and 8.3% when 5 ticks were pooled.

^cNemuro, Horonobe, Kiyosato, Hobetsu, Ebetsu, and Sumoto were included.