Appraisal methods for controlling the infection by enzootic bovine leukosis

Ciência Rural

van der Laan, Carlos Willi²  Halfen, Daniza Coelho¹  Vidor, Teimo²  Braga, Fátima Machado¹ 

[1] Universidade Federal de Pelotas, Pelotas, Brasil;Universidade Federal de Pelotas

关键词: bovine leukemia virus;    enzootic bovine leukosis;    control;   

DOI  :  10.1590/S0103-84781997000400019

学科分类：农业科学（综合）

来源: Universidade Federal de Santa Maria * Centro de Ciencias Rurais

【 摘 要 】

Three procedures for the control of bovine leukemia vírus infection (BLV) were evaluated: a) elimination of seropositive animals: b) segregation of animals into seropositive and seronegative groups: c) combined management and use of strict procedures to minimize viral transmission. The first serological testing in eight dairy farms demonstrated a prevalence ranging of 2.5% (1/40) to 58.1% (18/31). Two farms with a low prevalence (<10%) decided to cull the seropositive animals. In one of these farms, the culting of positive animals resulted in eradication of the infection, demonstrated by the absence of seropositive reactors in the following tests. In the second farm, where the only seropositive animal was kept in the herd, the incidence reached 20% (3/15) in a six months period. The culling of the reactors in farms with low levels of infection seemed to be the most efficient procedure for eradication the infection. Segregation of reactors and negative animals into two groups was adopted in one farm, where only one animal seroconverted during the experiment, resulting in an incidence of 4.5% (1/22). The farms where a combined management was adopted presented a incidence ranging between 2.6% (1/38) and 50% (4/8). These resulls suggested that this procedure woutd require a longer period of observation in order to evaluate its efficacy. It has been possible to obtain seronegative offspring from positive dams when a substitutive or heat-inactivated milk was used. The reduction of the level of infection in a herd, without immediately culling the infected animals may be possible by replacing older animais with heifers bom in the samefarm.

【 授权许可】

CC BY-NC