Control of Bovine Leukemia Virus in Three US Dairy Herds by Culling ELISA-Positive Cows

Table 2

Bovine leukemia virus (BLV) antibody testing schedule and results for Herd R.

Test Date	Test Type	Description	Results^1
July 2015	Herd (milk)	All cows in the milking herd	27/849 (3.2%)
September 2015	Interim (milk)	Cows dry at July test and 1st lactation heifers^2,3,4	5/136
February 2016	Herd (milk)	All cows in the milking herd^2,5	31/844 (3.7%)
May 2016	Interim (milk)	Test of 1st lactation heifers^2,6	22/218
August 2016	Herd (milk)	All cows in the milking herd^2,7	46/849 (5.4%)

BLV-antibody positive (“positive”) over total tested, with point prevalence (%) for herd tests.
Heifers had comingled with animals from other herds at the out-of-state calf-raising facility.
All five (5) positive animals were 1st lactation heifers.
Excludes one (1) cow tested in July 2015 that was inadvertently re-tested in September.
Five (5) positive cows were new infections in previously negative animals, fourteen (14) were 1st lactation heifers, and twelve (12) were previously positive animals.
Includes ninety-four (94) 1st lactation heifers previously tested in February, eleven (11) of which were positive at that time.
Seven (7) positive cows were new infections in previously negative animals, nine (9) were 1st lactation heifers, and thirty (30) were previously positive animals.