Evidence of bovine leukemia virus circulating in sheep and buffaloes in Colombia: insights into multispecies infection

Exploring viral diversity and metagenomics in livestock: insights into disease emergence and spillover risks in cattle

Cattle have a significant impact on human societies in terms of both economics and health. Viral infections pose a relevant problem as they directly or indirectly disrupt the balance within cattle populations. This has negative consequences at the economic level for producers and territories, and also jeopardizes human health through the transmission of zoonotic diseases that can escalate into outbreaks or pandemics. To establish prevention strategies and control measures at various levels (animal, farm, region, or global), it is crucial to identify the viral agents present in animals. Various techniques, including virus isolation, serological tests, and molecular techniques like PCR, are typically employed for this purpose. However, these techniques have two major drawbacks: they are ineffective for non-culturable viruses, and they only detect a small fraction of the viruses present. In contrast, metagenomics offers a promising approach by providing a comprehensive and unbiased analysis for detecting all viruses in a given sample. It has the potential to identify rare or novel infectious agents promptly and establish a baseline of healthy animals. Nevertheless, the routine application of viral metagenomics for epidemiological surveillance and diagnostics faces challenges related to socioeconomic variables, such as resource availability and space dedicated to metagenomics, as well as the lack of standardized protocols and resulting heterogeneity in presenting results. This review aims to provide an overview of the current knowledge and prospects for using viral metagenomics to detect and identify viruses in cattle raised for livestock, while discussing the epidemiological and clinical implications.

High prevalence of Enterovirus E, Bovine Kobuvirus, and Astrovirus revealed by viral metagenomics in fecal samples from cattle in Central Colombia

Livestock plays a crucial role in ensuring food security and driving the global economy. However, viral infections can have far-reaching consequences beyond economic productivity, affecting the health of cattle, as well as posing risks to human health and other animals. Identifying viruses present in fecal samples, a primary route of pathogen transmission, is essential for developing effective prevention, control, and surveillance strategies. Viral metagenomic approaches offer a broader perspective and hold great potential for detecting previously unknown viruses or uncovering previously undescribed agents. Ubaté Province is Colombia's dairy capital and a key center for livestock production in the country. Therefore, the purpose of this study was to characterize viral communities in fecal samples from cattle in this region. A total of 42 samples were collected from three municipalities in Ubaté Province, located in central Colombia, using a convenient non-probabilistic sampling method. We utilized metagenomic sequencing with Oxford Nanopore Technologies (ONT), combined with diversity and phylogenetic analysis. The findings revealed a consistent and stable viral composition across the municipalities, primarily comprising members of the Picornaviridae family. At the species level, the most frequent viruses were Enterovirus E (EVE) and Bovine Astrovirus (BoAstV). Significantly, this study reported, for the first time in Colombia, the presence of viruses with veterinary importance occurring at notable frequencies: EVE (59%), Bovine Kobuvirus (BKV) (52%), and BoAstV (19%). Additionally, the study confirmed the existence of Circular replicase-encoding single-stranded (CRESS) Virus in animal feces. These sequences were phylogenetically grouped with samples obtained from Asia and Latin America, underscoring the importance of having adequate representation across the continent. The virome of bovine feces in Ubaté Province is characterized by the predominance of potentially pathogenic viruses such as BoAstV and EVE that have been reported with substantial frequency and quantities. Several of these viruses were identified in Colombia for the first time. This study showcases the utility of using metagenomic sequencing techniques in epidemiological surveillance. It also paves the way for further research on the influence of these agents on bovine health and their frecuency across the country.

Seroprevalence and risk factors associated with bovine Leukemia virus infection in argentine beef cattle

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, an endemic disease in dairy cattle of Argentina. However, little is known about the seroprevalence of BLV in beef cattle. In this study, we conducted a cross-sectional study including farms from thirteen provinces of Argentina. A total of 5827 bovine serum samples were collected from 76 farms and analyzed using an in-house developed enzyme-linked immunosorbent assay. Information about herd management was collected through a questionnaire, and univariate and multivariate analyses were performed to detect risk factors associated with BLV infection. Herd-level seroprevalence was 71.05%, while the mean animal-level seroprevalence was 7.23% (median = 2.69%; min = 0, max = 75). Only two provinces had no positive BLV samples. The other eleven provinces showed more than 50% of their farms infected with BLV. The multivariate model revealed that BLV prevalence was significantly associated with the use of animals raised in the same farm for cattle replacement (P = 0.005), breeding cows by natural mating with a bull (P < 0.001), and weaning calves after 6 months of age (P = 0.011). This extensive study revealed that BLV seroprevalence in Argentine beef farms has increased during the last years and allowed identifying some management practices associated with BLV prevalence. These data deserve special attention because BLV infection in beef cattle seems to lead to a dissemination pattern similar to that observed during the last decades in dairy cattle, especially considering that Argentina is the sixth beef producer in the world, with about 5% of global beef production.

Diagnosis of Ruminant Viral Diseases with Loop-Mediated Isothermal Amplification

Infectious diseases in livestock industry are major problems for animal health, food safety, and the economy. Zoonotic diseases from farm animals are significant threat to human population as well. These are notifiable diseases listed by the World Organization for Animal Health (OIE). Rapid diagnostic methods can help keep infectious diseases under control in herds. Loop-mediated isothermal amplification (LAMP) is a simple and rapid nucleic acid amplification method that is studied widely for detection of many infectious diseases in the field. LAMP allows biosensing of target DNA or RNA under isothermal conditions with high specificity in a short period of time. An untrained user can analyze results based on color change or turbidity. Here we review LAMP assays to diagnose OIE notifiable ruminant viral diseases in literature highlighting properties of LAMP method considering what is expected from an efficient, field usable diagnostic test.

Usefulness of Next-Generation Sequencing in Excluding Bovine Leukemia Virus as a Cause of Adult Camel Leukosis in Dromedaries

Adult camel leukosis is an emerging hematological and neoplastic disease in dromedaries. It has been hypothesized that bovine leukemia virus (BLV) or its genetic variants may be associated with adult camel leukosis. In this study, we used next-generation sequencing (NGS) to detect all possible viruses in five lung samples from five dromedaries with histopathological evidence of adult camel leukosis and four tissue samples from two control dromedaries. A total throughput of 114.7 Gb was achieved, with an average of 12.7 Gb/sample. For each sample, all the pair-end 151-bp reads were filtered to remove rRNA sequences, bacterial genomes and redundant sequences, resulting in 1-7 Gb clean reads, of which <3% matched to viruses. The largest portion of these viral sequences was composed of bacterial phages. About 100-300 reads in each sample matched "multiple sclerosis-associated retrovirus", but manual analysis showed that they were only repetitive sequences commonly present in mammalian genomes. All viral reads were also extracted for analysis, confirming that no BLV or its genetic variants or any other virus was detected in the nine tissue samples. NGS is not only useful for detecting microorganisms associated with infectious diseases, but also important for excluding an infective cause in scenarios where such a possibility is suspected.

Bovine leukemia virus: a perspective insight into the infection and immunity

Bovine leukemia virus (BLV) is a member of the Retroviridae family and belongs to the Deltaretrovirus genus. It has a close relationship with human T-cell leukemia virus type I. BLV is responsible for causing enzootic bovine leukosis (EBL), a contagious disease that affects the bovine lymphatic system. This virus poses challenges for the global cattle industry, as it impacts cattle populations all over the world. Despite being widespread and impactful, BLV often goes unnoticed, with many researchers unaware of its presence and the potential consequences it carries. BLV demonstrates varying levels of pathogenicity. The majority of cattle (around 70%) become seropositive asymptomatic carriers, displaying no noticeable clinical symptoms. However, a smaller proportion of infected animals experience persistent lymphocytosis, characterized by an elevated number of lymphocytes in the bloodstream. If not monitored and managed, a subset of these persistently infected cattle may advance to lymphosarcoma. This condition typically presents as tumors in different lymphoid tissues, impacting various organs and overall health and productivity. Furthermore, recent research has highlighted the potential association between the occurrence of breast and lung cancer in humans and the presence of BLV. This review will delve into the recent discoveries concerning BLV, specifically exploring its epidemiology, the economic impact it has on the global cattle industry, its implications for human medicine, and the association between different alleles of the major histocompatibility complex (MHC) and susceptibility or resistance to BLV. Bovine leukemia virus, Enzootic bovine leukosis, Major histocompatibility complex, Retroviridae.

In vitro Susceptibility of Human Cell Lines Infection by Bovine Leukemia Virus

Evidence of the presence of bovine leukemia virus (BLV) in human beings and its association with breast cancer has been published in the literature, proposing it as a zoonotic infection. However, not enough evidence exists about transmission pathways nor biological mechanisms in human beings. This study was aimed at gathering experimental evidence about susceptibility of human cell lines to BLV infection. Malignant and non-malignant human cell lines were co-cultured with BLV-infected FLK cells using a cell-to-cell model of infection. Infected human cell lines were harvested and cultured for 3 to 6 months to determine stability of infection. BLV detection was performed through liquid-phase PCR and visualized through in situ PCR. Seven out of nine cell lines were susceptible to BLV infection as determined by at least one positive liquid-phase PCR result in the 3-month culture period. iSLK and MCF7 cell lines were able to produce a stable infection throughout the 3-month period, with both cytoplasmic and/or nuclear BLV-DNA visualized by IS-PCR. Our results support experimental evidence of BLV infection in humans by demonstrating the susceptibility of human cells to BLV infection, supporting the hypothesis of a natural transmission from cattle to humans.