An unusual presentation of enzootic bovine leukosis

A 6-year-old, Holstein x Simmental cow diagnosed with pyelonephritis had increasing difficulty rising and became recumbent, despite treatment with antibiotics. A serological test for the bovine leukemia virus was positive; at necropsy, the left kidney and ureter and the myocardium showed lesions of lymphosarcoma, confirmed by histology.     

Preliminary studies on enzootic bovine leukosis in Saudi dairy farms

The occurrence of sporadic cases of enzootic bovine leukosis in commercial dairy farms in Saudi Arabia was recently confirmed and found to be associated with importation of breeding heifers. Immunodiffusion test was applied to screen the prevalence of infection with bovine leukemia virus among local traditional and dairy cattle. All the 102 examined local cattle were negative, while out of the 1329 tested dairy animals (originating from 23 farms), 268 (from 16 farms) showed precipitating activity. As an epizootiological model, all animals of an infected dairy farm were serologically examined. Out of the 560 originally imported cows and the 1849 animals born locally in the farm, 217 (39%) and 468 (25%) animals, respectively, were found positive. The correlation between the age of locally born animals and the occurrence of antibodies against bovine leukemia virus was discussed.     

Sero-epidemiological and pathological studies on enzootic bovine leukosis in Turkey.

The prevalence of enzootic bovine leukosis (EBL) in Turkey was investigated by serological screenings using the agargel immunodiffusion test (AGID). A total of 4,047 blood samples obtained from 2,780 cattle between one and 14 years of age and taken in 6-8 month-intervals in three dairy farms were tested for the presence of EBL-specific antibodies. A high prevalence of EBL-sero-positive animals was found amongst cattle in two of the farms. Furthermore, recommendations based upon the regulation implemented by an expert group of the European Commission and considering the local dairy management conditions were presented.     

The diagnosis of enzootic bovine leukosis

This paper reviews the clinical and virological diagnostic procedures for enzootic bovine leukosis (EBL). The clinical diagnosis must be always confirmed by a specific laboratory test for Bovine Leukaemia Virus (BLV). Many virological tests were proposed. The sensitivity of all the diagnostic methods is sufficient to do an early detection of a BLV infection on an individual base. Advantages of the highly sensitive methods like RIA and ELISA appear when the samples to be tested have naturally very low antibody titers (individual milk, bulk milk, pooled sera).     

An enzyme-linked immunosorbent assay for enzootic bovine leukosis virus antibodies

An enzyme-linked immunosorbent assay (ELISA) for detecting antibodies to enzootic bovine leukosis (EBL) virus is described and its sensitivity compared with that of the agar gel immunodiffusion test (AGIDT) using 198 sera collected in Great Britain. There was 95 per cent agreement between the ELISA and AGIDT, when sera with positive/negative ratio (P/N) values of 1 . 5 or greater were considered positive. A total of 259 out of 264 sera (98 per cent) collected in Northern Ireland had P/N values of less than 1 . 5, the remaining sera having P/N values of 1 . 5 and 1 . 6. As Northern Ireland is clinically and serologically free of EBL infection it is proposed that sera with P/N values of 1 . 5 and 1 . 6, which account for approximately 3.5 per cent of the total sera tested, are considered doubtful and should be tested by another serological test.     

Eradication of enzootic bovine leukosis from Finland

Enzootic bovine leukosis (EBL) was recognized among Finnish cattle in 1966. Administrative decisions specifying and refining official control measures were given in 1966, 1976, 1980, and 1993. The measures' key principle always has been 'test and slaughter'. The EBL/bovine leukosis virus (BLV) infection situation was monitored at meat inspection, and hematologically between 1970 and 1977 and serologically between 1978 and 1989. Annual surveys including all dairy herds and samples from beef animals were conducted in 1990-2001. Bulk-tank milk samples represented the dairy herds in the surveys; the beef animals were sampled individually at slaughter. The maximum positive herd-level percentage in the surveys was 0.03%. EBL/BLV infection was evenly dispersed in the southern part of the country and nonexistent in the northern part. We conclude that herd-level prevalence of EBL/BLV infection never exceeded 5%. It nevertheless took 30 years to eradicate the disease and the infection. EBL was eradicated from mainland Finland in 1996 and from the island district of Ahvenanmaa in 1999. Annual monitoring of the EBL situation continues.     

Epidemiological study of enzootic bovine leukosis in Brazil

Tropical Animal Health and Production -     

The eradication experience of enzootic bovine leukosis from Lithuania

Before 1985 the situation regarding enzootic bovine leukosis (EBL) in Lithuanian cattle was described only haphazardly. In 1986 serological investigations were initiated together with an eradication programme. The EBL bovine leukosis virus (BLV) situation was monitored by the Institute of Immunology Vilnius University, national and regional veterinary laboratories. Starting in 1986 all EBL-positive cattle were separated from negative cattle into BLV-infected and BLV-free herds. To create the latter, calves were fed pasteurized milk. The seroprevalence in 1990 was 7.29%, but it steadily declined to 0.32% in 2006.