ABSTRACT
As part of the Danish control program for enzootic bovine leukosis, three hematologic screenings of all cattle herds in Denmark were performed in the period 1969-1978. Herds with multiple cases of persistent lymphocytosis and/or leukotic tumors were classified as "leukosis herds." During nationwide blood testing, 369 leukosis herds were discovered, and an additional 77 herds were found due to follow-up of tumor cases or special testing in connection with movements of cattle in 1969-1978. In the present study, the prevalence of leukosis herds in the three screening rounds is related to geographic area and herd size. By means of a statistical log-linear model, the authors show that prevalence increased proportionally with herd size. The observed number of leukosis herds per 10,000 herds tested declined during the screening program from 105 to 38 in east Denmark and from 12 to 4 in west Denmark.
Subject(s)
Cattle Diseases/epidemiology , Disease Outbreaks/veterinary , Animals , Cattle , Cattle Diseases/microbiology , Denmark/epidemiology , Hematologic Tests/veterinary , Oncogenic Viruses/growth & development , Sensitivity and SpecificitySubject(s)
Cattle/blood , Erythrocytes/analysis , Animals , Europe , Reference Values , Species SpecificityABSTRACT
As a prelude to the introduction of serological methods in the Danish leukosis eradication programme, an examination for antibody to Bovine Leukemia Virus (BLV) was carried out in 215 randomly selected leukosis-free herds in three areas where 3 routine haematological screening tests had bee made over a period of 6 years. A gel diffusion test was applied to plasma samples. Of 3319 animals screened, none were found to have detectable levels of antibody to BLV in their plasma. This would seem to indicate that false positive reactions are not a serious problem in connection with this test, and also that herds classified as leukosis-free after a series of haematological herd tests carried out within a period of some years, are in fact free from infection with Bovine Leukemia Virus.
Subject(s)
Antibodies, Viral/analysis , Cattle Diseases/immunology , Leukemia Virus, Bovine/immunology , Leukemia/veterinary , Retroviridae/immunology , Animals , Antigens, Viral , Cattle , Denmark , Hematologic Tests , ImmunodiffusionABSTRACT
The Danish programme to control bovine enzootic leukosis was initiated in 1959 and intensified in 1969. The programme has resulted in a sharp decline in total and relative numbers of leukotic tumor cases in adult animals. However, total eradication of bovine leukosis has not yet been achieved, and the statistics from recent years seem to indicate that the present programme based on haematological and histological examinations will control but not eradicate the disease. An immunodiffusion test based on an internal protein (p 24) antigen has been used experimentally. This test is a valuable tool in herd diagnosis, but it is not sensitive enough for accurate single animal diagnosis.
