TABLE 1.

Farms involved in the study

Farm	Region	Country	Mo-yr of sampling
A	Blekinge	Sweden	3-95
B	Blekinge	Sweden	3-95
C	Blekinge	Sweden	3-95
D	Blekinge	Sweden	3-95
E	Blekinge	Sweden	3-95
F	Blekinge	Sweden	3-95
G	Blekinge	Sweden	3-95
H	Blekinge	Sweden	3-95
I	Blekinge	Sweden	3-95
J	Halland	Sweden	6-96
K	Skaraborg	Sweden	3-95
L	Skaraborg	Sweden	3-95
M	Skaraborg	Sweden	3-95
N	Skåne	Sweden	2-97
O	Älvsborg	Sweden	3-97
P	Vasa	Finland	2-97
Q	Vasa	Finland	10-96
R	Vasa	Finland	2-97