Use of control antigen to improve the enzyme-linked immunosorbent assay for enzootic bovine leukosis antibodies

Bovine Leukemia Virus (BLV) is the etiologic agent of Enzootic Bovine Leukosis, a retrovirus exogenous to the bovine species. Once infected, there is no detectable viraemia but instead there is a strong and persistent immunological response to BLV structural proteins, essentially the gp51 envelope glycoprotein and the mayor core protein p24. We describe the test procedure of an indirect ELISA (I-ELISA) using polyclonal reagents for the detection of antibodies to BLV. For comparison, the sera were simultaneously tested by agar gel immunodiffussion (AGID) test, which is currently used as diagnostic standard for BLV infection. The antigen applied does not require a high degree of purification and the data from the analysis of the negative sera showed that the establishment of a cut-off level corresponding to 3 times the standard deviation (SD) above the mean for the negative control set of sera provided acceptable specificity, reducing the risk of false positives results. A comparison of the results obtained by AGID test and I-ELISA showed that considering a total of 465 serum samples, all of the 234 samples (50%) that were positive by AGID were positive to the I-ELISA. Of 225 serum samples which yielded negative results in the AGID test, 69 (15%) were found to be positive by the I-ELISA and 156 (33%) were negative by both techniques. Few sera (2%) that were non-specific by AGID were defined as negative or positive by I-ELISA.

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A case study of enzootic bovine leukosis in an Albanian dairy herd based on se-rological and hematological test results

Turkey Diseases, Production and Management - German Journal of Veterinary Research ◽

10.51585/gjvr.2021.0005 ◽

2021 ◽

Vol 1 (1) ◽

pp. 28-33

Author(s):

Majlind Sulçe ◽

◽

Anita Koni ◽

Gerald Muça ◽

Pëllumb Zalla ◽

...

Keyword(s):

Serological Test ◽

Dairy Herd ◽

Enzyme Linked Immunosorbent Assay ◽

Small Scale ◽

Test Results ◽

Enzootic Bovine Leukosis ◽

Cattle Herds ◽

Bovine Leukosis ◽

Disease Stages

Enzootic bovine leukosis (EBL) is a notifiable infectious disease with sporadic fre-quency in Albania. EBL is not a zoonotic disease, but it has an important impact on the cattle trade. Diagnosis of this disease can be performed by many diagnostic proce-dures, including agar gel immunodiffusion (AGID), enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) tests. In some cases, where persis-tent lymphocytosis is present, cell count can turn useful. This study aimed to evaluate serological and hematological tests' suitability for the diagnosis of EBL and assess the manual and automatic hematological count technique diagnostic parameters com-pared to the serological test. Results suggest that strategic use of hematological and AGID tests in parallel can increase the sensitivity of diagnosis and facilitate the detec-tion of infected animals in different disease stages. Moreover, our results indicate that this approach is feasible in small scale cattle herds size, which properly fits Albanian circumstances

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Performance assessment of imported ELISA in the serodiagnosis of the enzootic bovine leukosis in herds of Pernambuco state, Brazil

Arquivos do Instituto Biológico ◽

10.1590/1808-1657000662018 ◽

2019 ◽

Vol 86 ◽

Author(s):

Luiz Carlos Fontes Baptista Filho ◽

Artur Cesar de Carvalho Fernandes ◽

Tamyres Izarelly Barbosa da Silva ◽

Taciana Rabelo Ramalho Ramos ◽

Lúcio Esmeraldo Honório de Melo

Keyword(s):

Leukemia Virus ◽

High Sensitivity ◽

Serum Levels ◽

Diagnostic Methods ◽

Enzyme Linked Immunosorbent Assay ◽

Serum Samples ◽

Enzootic Bovine Leukosis ◽

Efficient Test ◽

Bovine Leukosis ◽

Low Prevalence

ABSTRACT: Enzootic bovine leukosis (EBL) is an infectious disease of cosmopolitan distribution and chronic character caused by a virus of the Retroviridae family, bovine leukemia virus (BLV). The epidemiological situation of EBL in Brazil has motivated studies to improve its diagnosis, based on the recommended serological techniques: agar gel immunodiffusion (AGID) and enzyme-linked immunosorbent assay (ELISA). This study was designed to evaluate the use of imported ELISA for the detection of BLV in dairy herds raised in Pernambuco, Brazil, comparing it to AGID. Blood serum samples from 327 dairy cattle from the state of Pernambuco were tested to AGID and the imported commercial ELISA CHEKIT-Leucose-serum, produced by the IDEXX® laboratory for the diagnosis of EBL. Discarding 25 inconclusive samples from one or both tests, 302 samples were analyzed, being 24.1% positive (73/302) in the AGID and 45% (136/302) in the ELISA, which compared to the AGID, a technique considered standard, presented sensitivity of 98.6%, specificity of 72% and Kappa coefficient of 0.55. The lack of agreement in the diagnostic methods was probably due to the high sensitivity of the ELISA, which makes it possible to detect antibodies even in situations with low serum levels. Although AGID has been shown to be an efficient test so far, in more advanced stages of an EBL control and eradication program, with low prevalence rates, ELISA will present better performance, due to its higher sensitivity, avoiding the permanence of animals that spread the disease in the herds.

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