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 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 municipalities of Boyacá and Cundinamarca (Colombia). Methods: A simple descriptive cross-sectional study with random sampling was conducted. A total of 1140 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 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 risk factors, contaminated blood in needle is considered one of the main routes of transmission. On the other hand, manual milking was identified as risk factors 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.