Direct polymerase chain reaction from blood and tissue samples for rapid diagnosis of bovine leukemia virus infection

Seroprevalence of bovine leukemia virus in cattle and buffaloes in the border provinces of the Eastern Anatolia region, Türkiye: insights into the eradication of infection

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, an oncogenic deltaretrovirus that has emerged as a potential zoonotic infection. The BLV naturally infects cattle and causes economic losses through a slow persistent infection with various clinical symtoms following preleukosis. The main objective of this study was to determine the seroprevalence of BLV antibodies in cattle and buffaloes in the border provinces of the Eastern Anatolia region, Türkiye, using the agar gel immunodiffusion (AGID) assay and enzyme-linked immunosorbent assay (ELISA). For this purpose, a total of 1,033 serum samples were collected from 982 cattle and 51 buffaloes from the provinces of Ağrı (n = 178), Iğdır (n = 252), Kars (n = 317), Van (n = 221), and Hakkari (n = 65) during 2021 - 2022. In AGID and ELISA tests, seropositivity for BLV-specific antibodies was not detected in cattle and buffaloes from the mentioned provinces. This study revealed that BLV was not circulating in cattle and buffaloes in the easternmost border provinces of Türkiye during the sampling period and contributed to determine the status of BLV in the mentioned region. Due to the presence of virus in other regions of Türkiye and neighboring countries, Iran and Iraq, it is recommended to control animal movements, continue efforts to combat the transmission of the virus, and maintain control measures.

The Global Epidemiology of Bovine Leukemia Virus: Current Trends and Future Implications

Bovine leukemia virus (BLV) is a retrovirus that causes enzootic bovine leucosis (EBL), which is the most significant neoplastic disease in cattle. Although EBL has been successfully eradicated in most European countries, infections continue to rise in Argentina, Brazil, Canada, Japan, and the United States. BLV imposes a substantial economic burden on the cattle industry, particularly in dairy farming, as it leads to a decline in animal production performance and increases the risk of disease. Moreover, trade restrictions on diseased animals and products between countries and regions further exacerbate the problem. Recent studies have also identified fragments of BLV nucleic acid in human breast cancer tissues, raising concerns for public health. Due to the absence of an effective vaccine, controlling the disease is challenging. Therefore, it is crucial to accurately detect and diagnose BLV at an early stage to control its spread and minimize economic losses. This review provides a comprehensive examination of BLV, encompassing its genomic structure, epidemiology, modes of transmission, clinical symptoms, detection methods, hazards, and control strategies. The aim is to provide strategic information for future BLV research.

Bovine Leukaemia Virus: Current Epidemiological Circumstance and Future Prospective

Bovine leukaemia virus (BLV) is a deltaretrovirus that is closely related to human T-cell leukaemia virus types 1 and 2 (HTLV-1 and -2). It causes enzootic bovine leukosis (EBL), which is the most important neoplastic disease in cattle. Most BLV-infected cattle are asymptomatic, which potentiates extremely high shedding rates of the virus in many cattle populations. Approximately 30% of them show persistent lymphocytosis that has various clinical outcomes; only a small proportion of animals (less than 5%) exhibit signs of EBL. BLV causes major economic losses in the cattle industry, especially in dairy farms. Direct costs are due to a decrease in animal productivity and in cow longevity; indirect costs are caused by restrictions that are placed on the import of animals and animal products from infected areas. Most European regions have implemented an efficient eradication programme, yet BLV prevalence remains high worldwide. Control of the disease is not feasible because there is no effective vaccine against it. Therefore, detection and early diagnosis of the disease are essential in order to diminish its spreading and the economic losses it causes. This review comprises an overview of bovine leukosis, which highlights the epidemiology of the disease, diagnostic tests that are used and effective control strategies.

Seroprevalence of bovine leukemia virus in cattle, buffalo, and camel in Egypt

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis. It causes significant economic losses associated with losses due to slaughter and eradication of infected animal from infected area and other indirect economic losses such as restriction on importation of animals and semen from infected area. The main objective of this study was to determine the seroprevalence of BLV antibodies in cattle, buffaloes, and camels in Egypt using ELISA test. Serum samples were collected from 350 cattle, 100 buffaloes, and 100 camels during 2018. The seropositivity for BLV-specific antibody was 20.8%, 9%, and 0% in cattle, buffaloes, and camels, respectively. The result revealed significant association (p < 0.05) between age and seroprevalence of BLV infection in cattle > 4 years (24%) compared with those < 4 years (13%). We found no significant association between pregnancy and herd size and seroprevalence of BLV infection in this study (p > 0.05). Furthermore, the age, pregnancy state, and herd size had significant effect on seroprevalence of BLV infection in buffaloes. This study contributes that BLV is detected in cattle and buffaloes in Egypt and confirms that the camels has resistance against BLV infection. Hence, the control measures are very necessary to combat the transmission of the disease and reduce its economic impact.

Direct PCR-RFLP based detection and differentiation of Anaplasma species in naturally infected goats of eastern Haryana, India

The present investigation was designed to develop a novel, rapid and cost effective direct PCR-RFLP assay, as a specific diagnostic tool for detection and differentiation of two Anaplasma species (A. ovis and A. marginale). Blood samples were collected randomly from 83 goats. A direct blood polymerase chain reaction (DT-PCR) for amplifying a fragment of the major surface protein 5 (msp5) gene of A. ovis/A. marginale from whole blood was developed and standardized. Blood smear examination revealed 24 samples (28.91%) positive for Anaplasma inclusion bodies. While, 39 (47%) samples were positive by DT-PCR. The results revealed that DT- PCR was 100% sensitive and 74.57% specific compared to microscopy based detection (k =0.62). Additionally DT-PCR showed 94.44% sensitivity and 100% specificity compared to conventional PCR results with suspected blood samples (k=0.94). All DT-PCR positive samples were confirmed to be A. ovis by restriction fragments length polymorphism (RFLP) analysis. The phylogenetic tree and sequence analysis revealed msp5 gene of Anaplasma species Indian isolate had maximum distance from A. phagocytophilum followed by A. centrale and A. marginale and 100% sequence identity with A. ovis isolates of Chinese origin which further confirmed the sequence identified in native goats to be of A. ovis. The simplified DT-PCR assay as a viable alternative to conventional PCR could be helpful for fast and accurate diagnosis of Anaplasma species and suitable for screening a large number of samples. Furthermore, results revealed that DT-PCR-RFLP of the msp5 gene might be a useful method for simultaneous detection and differentiation of A. ovis and A. marginale in goats.

MicroRNAs Encoded by Bovine Leukemia Virus (BLV) Are Associated with Reduced Expression of B Cell Transcriptional Regulators in Dairy Cattle Naturally Infected with BLV

Bovine leukemia virus (BLV) is estimated to infect over 83% of dairy herds and over 40% of all dairy cows in the United States. While, BLV only causes leukemia in a small proportion of animals, research indicates that BLV+ cattle exhibit reduced milk production and longevity that is distinct from lymphoma development. It is hypothesized that BLV negatively affects production by interfering with cattle immunity and increasing the risk of secondary infections. In particular, BLV+ cows demonstrate reduced circulating levels of both antigen-specific and total IgM. This study investigated possible mechanisms by which BLV could interfere with the production of IgM in naturally infected cattle. Specifically, total plasma IgM and the expression of genes IGJ, BLIMP1, BCL6, and PAX5 in circulating IgM+ B cells were measured in 15 naturally infected BLV+ and 15 BLV− cows. In addition, BLV proviral load (PVL) (a relative measurement of BLV provirus integrated into host DNA) and the relative expression of BLV TAX and 5 BLV microRNAs (miRNAs) were characterized and correlated to the expression of selected endogenous genes. BLV+ cows exhibited lower total plasma IgM and lower expression of IGJ, BLIMP1, and BCL6. While, BLV TAX and BLV miRNAs failed to correlate with IGJ expression, both BLV TAX and BLV miRNAs exhibited negative associations with BLIMP1 and BCL6 gene expression. The results suggest a possible transcriptional pathway by which BLV interferes with IgM production in naturally infected cattle.

Epidemiology and genetic diversity of bovine leukemia virus

Bovine leukemia virus (BLV), an oncogenic member of the Deltaretrovirus genus, is closely related to human T-cell leukemia virus (HTLV-I and II). BLV infects cattle worldwide and causes important economic losses. In this review, we provide a summary of available information about commonly used diagnostic approaches for the detection of BLV infection, including both serological and viral genome-based methods. We also outline genotyping methods used for the phylogenetic analysis of BLV, including PCR restriction length polymorphism and modern DNA sequencing-based methods. In addition, detailed epidemiological information on the prevalence of BLV in cattle worldwide is presented. Finally, we summarize the various BLV genotypes identified by the phylogenetic analyses of the whole genome and env gp51 sequences of BLV strains in different countries and discuss the distribution of BLV genotypes worldwide.

Identification of an Atypical Enzootic Bovine Leukosis in Japan by Using a Novel Classification of Bovine Leukemia Based on Immunophenotypic Analysis

Bovine leukemia is classified into two types: enzootic bovine leukosis (EBL) and sporadic bovine leukosis (SBL). EBL is caused by infection with bovine leukemia virus (BLV), which induces persistent lymphocytosis and B-cell lymphoma in cattle after a long latent period. Although it has been demonstrated that BLV-associated lymphoma occurs predominantly in adult cattle of >3 to 5 years, suspicious cases of EBL onset in juvenile cattle were recently reported in Japan. To investigate the current status of bovine leukemia in Japan, we performed immunophenotypic analysis of samples from 50 cattle that were clinically diagnosed as having bovine leukemia. We classified the samples into five groups on the basis of the analysis and found two different types of EBL: classic EBL (cEBL), which has the familiar phenotype commonly known as EBL, and polyclonal EBL (pEBL), which exhibited neoplastic proliferation of polyclonal B cells. Moreover, there were several atypical EBL cases even in cEBL, including an early onset of EBL in juvenile cattle. A comparison of the cell marker expressions among cEBL, pEBL, and B-cell-type SBL (B-SBL) revealed characteristic patterns in B-cell leukemia, and these patterns could be clearly differentiated from those of healthy phenotypes, whereas it was difficult to discriminate between cEBL, pEBL, and B-SBL only by the expression patterns of cell markers. This study identified novel characteristics of bovine leukemia that should contribute to a better understanding of the mechanism underlying tumor development in BLV infection.