Molecular Detection of Persistent Francisella tularensis Subspecies holarctica in Natural Waters

Table 1

Reported human tularemia cases (County Medical Officer, Gävle-Sandviken, personal communication, and Swedish Institute for Infectious Disease Control, SMI, Örebro County) and F. tularensis subsp. holarctica culture-positive rodents in the Ljusdal and Örebro areas during the study period. The total numbers of trapped rodents are shown in parentheses. Results of the molecular analysis of water samples from the four sampling points selected for detailed examination. Positive lpnA assay results indicate the presence of F. tularensis. The length of resulting FtM19InDel sequences indicates the presence of F. tularensis subsp. holarctica or other F. tularensis subspecies (other ssp.). n.d., not detected; n.s., not sampled.

			Ljusdal		Örebro
			I	II	A	B
2003	Human cases		1		150
	Rodents		0 (60)		2 (37)
	Water
		No. of samples tested	(4)	(4)	(2)	(2)
		lpnA	2	2	n.d.	1
		FtM19InDel	1	1		1
			holarctica	holarctica	n.d.	holarctica
2004	Human cases		0		54
	Rodents		n.s.		0 (7)
	Water
		No. of samples tested	(7)	(7)	(8)	(8)
		lpnA	2	1	2	4
		FtM19InDel	2	1	2	3
			holarctica	holarctica	holarctica	holarctica
2005	Human cases		18		25
	Rodents		n.s.		n.s.
	Water
		No. of samples tested	(3)	(3)	(3)	(3)
		lpnA	3	3	3	1
		FtM19InDel	1+1	2	1+1	1
			holarctica+ other ssp.	holarctica	holarctica+ other ssp.	holarctica