Risk factors associated with enzootic bovine leukosis in Boyacá and Cundinamarca municipalities, Colombia

Abstract

Background: Enzootic bovine leukosis (EBL) is a lymphoproliferative disorder caused by the bovine leukemia virus (BLV),  a virus of the Retroviridae family. The infection is distributed worldwide, and a high percentage of animals infected by the BLV are asymptomatic and act as carriers of the virus in many cattle populations.

Aim: To identify the risk  factors associated with EBL in the municipalities of Boyacá and Cundinamarca (Colombia).

Methods: A simple  descriptive cross-sectional study with random sampling was conducted. A total of 1,140 blood samples were taken from  cattle (females and males) from the municipalities of Chiquinquirá, Ubaté, and San Miguel de Sema of different breeds  and age groups. The samples were processed using the commercial ELISA SERELISA® BLV Ab Mono Blocking kit  (sensitivity 97%, specificity 98%). The data were processed with the statistical programs WinEpi and Epi Info® version  7.2.4.0, estimating the prevalence ratio, implementing the chi-square test (p ≤ 0.05) and logistic regression.

Results: A  true prevalence (TP) and apparent prevalence (AP) of 23.61% and 22.7% in Ubaté, 19.22% and 18.1% in Chiquinquirá, and  15.61% and 14.3% in San Miguel de Sema, respectively, were established. Bovines 2–4 years old were the most  prevalent in Ubaté and Chiquinquirá (37.5% and 21.21%, respectively), while in San Miguel de Sema individuals >4 years  had the highest percentage of antibodies (18.3%). The Holstein breed had a higher prevalence in Ubaté and San Miguel  de Sema (26.02% and 19.67%), and crossbreeds were more BLV-seroprevalence in Chiquinquirá (20.20%). In Ubaté, re- use of needles was identified as a risk factor, contaminated blood in needles is considered one of the main routes of  transmission. On the other hand, manual milking was identified as a risk factor in San Miguel de Sema.

Conclusion: The  non-implementation of an individual needle per animal in Ubaté; the Holstein breed and manual milking in San Miguel  de Sema were identified as risk factors for the presence of antibodies against the disease. EBL prevention and control  plans should be established that focus on the implementation of management and sanitary practices based on herd  biosecurity.