Table 1.

Seroprevalence of bovine leukemia virus (BLV) infection in yaks in Gansu province, northwestern China, by enzyme-linked immunosorbent assay (ELISA).

Factor	Category	No. tested	No. positive	Prevalence (%)
Gender	Male	471	112	23.78
	Female	1113	222	19.95
Age (years)	0 < years ≤ 1	286	57	19.93
	1 < years ≤ 3	594	123	20.71
	3 < years ≤ 5	355	89	25.07
	5 < years	349	65	18.63
Pregnancy	≤2	854	171	20.02
	3–5	189	38	20.11
	≥6	70	13	18.57
Season	Spring	428	99	23.13
	Summer	354	70	19.77
	Autumn	467	105	22.48
	Winter	335	60	17.91
Species	White yaks	974	186	19.10
	Black yaks	610	148	24.26
Region	Tianzhu	974	186	19.10
	Luqu	146	33	22.60
	Maqu	464	115	24.78
Total		1584	334	21.09