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The direct and indirect economic impacts of bovine leukemia virus infection on dairy cattle
... In addition, BLV infection can decrease milk production (Erskine et al., 2012a;Ott et al., 2003;Sargeant et al., 1997) and cow longevity (Brenner et al., 1989;Bartlett et al., 2013). These deleterious effects of BLV infection on the main economic determinants of a dairy farm highlight the importance of this virus infection, not only for dairy farms but also for the dairy industry as a whole (Pelzer, 1997;Trainin and Brenner, 2005). A high BLV prevalence, combined with its negative effects, make implementation of on-farm control programs desirable (Bartlett et al., 2014). ...
... The present model resulted in similar findings as other economic analysis in that BLV-infected cattle yielded lower partial net revenue than uninfected cattle (Chi et al., 2002;Ott et al., 2003;Rhodes et al., 2003). All of these reports and others (Pelzer, 1997;Trainin and Brenner, 2005) concluded that BLV caused economic losses. However, we found wide variation in factors that were taken into account and, consequently, in monetary loss attributed to BLV. ...
Bovine leukemia virus (BLV) is a production-limiting disease common in North American dairy herds. To make evidence-based recommendations to Canadian dairy producers and their consultants regarding cost and financial benefits of BLV on-farm control, an economic model that takes the supply-managed milk quota system into account is necessary. Alberta-specific input variables were used for the presented analysis. A decision tree model program was used to evaluate economic aspects of decreasing a 40% BLV within-herd prevalence on dairy farms by implementing various control strategies over 10 yr. Investigated strategies were (1) all management strategies, including 3 options for colostrum management; (2) some management strategies; (3) test and cull; and (4) test and segregate. Each of these strategies was compared with a no control on-farm approach. The prevalence for this no-control approach was assumed to stay constant over time. Each control strategy incurred specific yearly cost and yielded yearly decreases in prevalence, thereby affecting yearly partial net revenue. Infection with BLV was assumed to decrease milk production, decrease cow longevity, and increase condemnation of carcasses at slaughter from cattle with enzootic bovine leukosis, thereby decreasing net revenue. Cows infected with BLV generated a yearly mean partial net revenue of Can8,276. Mean cost for the control strategies ranged from Can1,315 for all management strategies (freezer); Can785 for all management strategies (powdered colostrum); Can1,592 for test and cull; and Can$1,594 for test and segregate. Consequently, on-farm BLV control was financially beneficial. Even though negative net benefits were possible and expected for some iterations, our sensitivity analysis highlighted the overall robustness of our model. In summary, this model provided evidence that Canadian dairy farmers should be encouraged to control BLV on their farm.
... The milk yield is an important economic and health factor closely connected with the health status of dairy cows that is expressed by higher susceptibility to infectious diseases (i.e. mastitis, dermatophytosis), their reproductive performance, longevity and milk composition and properties (Trainin and Brenner 2005;Janu et al. 2007;Hanuš et al. 2007). ...
... Effects of BLV infection with persistent lymphocytosis (PL) on milk yields were also studied. Summary of the published reports concerning BLV infection in association to infectious disease, productivity, reproductivity and culling rate is widely described by Trainin and Brenner (2005). In a study conducted by Motton and Buehring (2003), the effect of BLV was examined at a cellular rather than herd level. ...
Economic losses due to the bovine leukaemia virus infection can come from reduced milk production. The aim of this study was to evaluate molecular multiplex Polymerase Chain Reaction (multiplex PCR) test as an alternative for serologic Enzyme-linked Immunosorbent Assay (ELISA) method in diagnosing bovine leukaemia virus infections and found possible differences in milk yield in seronegative and seropositive cows. The study involved two groups of Polish Holstein-Friesian var. black and white cows (a total of 147 individuals). Animals were grouped according to their serological response to the bovine leukaemia virus antigen: control group of 71 healthy cows and second group of 76 naturally infected animals. Both multiplex PCR and ELISA proved to be very sensitive methods with sensitivity up to 100% and 97.4%, respectively. Negative effect of bovine leukaemia virus on milk yield was observed. Leucosis-free cows achieved higher milk yield (+ 322.9 kg; P <= 0.01), protein yield (+ 5.2 kg, P <= 0.05), and better milk yield after calculation into daily milk yield corrected for fat (+ 106.6 kg, P <= 0.05) in comparison to seropositive cows. In infected cows a significantly higher (P <= 0.01) fat content (4.1%) was recorded. Because ELISA test does not provide information of the infection at an early stage and is not sensitive enough to detect every infected animal, a two-step protocol allows for elimination of seropositive animals and restriction of their introduction into herds in Europe.
... CDCA2 gene acts as an immune related gene for various diseases in cattle through its implication in the DNA damage regulation that triggers cell cycle arrest under certain circumstances [86]. In Holstein cattle, a variant in the CDCA2 gene sequence was associated to host response to bovine leukemia virus [87], which weaken the animal immune system, creating favourable conditions for other infectious diseases, and leads to severe economic loss, due to reduced productivity, reproduction and high culling rate [88]. Another SNP associated with more than one trait is the SNP BovineHD1700013218 on BTA17, which was found related to all the traits except the SH. ...
Background: The genetics of Central African cattle have not been well-explored in terms of their potential for improved productivity. We therefore performed a genome wide association analysis (GWAS) on a total of 856 animals genotyped with the GGP Bovine 100K array, to identify genes or genomic regions of importance in body measurements in a local zebu (Gudali) and its crossbreed with the European Simmental (Simgud), using mixed linear model (MLM).
Results: SNP-based heritability of the four body traits under study varied between 0.23 ± 0.12 for the height at wither (HAW) to 0.44 ± 0.11 for the sacrum height (SH). The genetic correlation ranged from 0.19 ± 0.14 between HAW and ear length (EL), to 0.81 ± 0.06 between HAW and SH. For the phenotypic correlation, the ranges were 0.58 ± 0.00 between body length (BL) and EL to 0.90 ± 0.06 between HAW and BL. The maximum LD was 0.465 for Gudali and decreased by half (0.23) at a distance of 50,708 bp, while for the Simgud population the maximum LD was 0.47 and decreased to half (0.23) at 99,201 bp. Interestingly, we observed long ranges of LD throughout the Gudali and Simgud genome up to more than 1 mbp distant. These features are of great potential interest in association analysis and genetic improvement initiatives. We identified 59 SNPs associated to body traits. These SNPs were mapped within or near some 189 genes throughout the genome, with the CDCA2, EBF2, ADGRD1, NDUFAF1, DPPA4 and DPPA2 genes showing a pleiotropic effect since they were found associated with 2 or more traits.
Conclusions: This study identified a number of novel genes/loci associated with pathways influencing growth and body traits, disease resistance and immunity, reproduction and milk production. Overall, the identified genes could be considered as candidate genes in any attempt to improve growth, disease resistance and production in tropical cattle managed under extensive conditions. These genes or genomic regions should be targeted for any future cattle breeding in Cameroon.
... Moreover, the frequency of BLV-positive bulls disclosed by species agrees with reports by Trainin and Brenner (2005) and Beita (2008), who found a greater prevalence of seropositivity in Holstein (Bos taurus) and crossbreds. These authors also reported in Holsteins a higher predisposition to develop persistent lymphocytosis, which may favor the virus spread up into the herd. ...
... Moreover, the frequency of BLV-positive bulls disclosed by species agrees with reports by Trainin and Brenner (2005) and Beita (2008), who found a greater prevalence of seropositivity in Holstein (Bos taurus) and crossbreds. These authors also reported in Holsteins a higher predisposition to develop persistent lymphocytosis, which may favor the virus spread up into the herd. ...
Bovine leukemia virus (BLV) causes enzootic bovine leukosis, a persistent infection and the most important neoplastic disease in cattle. It is spread primarily by transferring infected lymphocytes through blood from carriers to healthy animals. The present study is aimed at determining the seropositivity of BLV in breeding bulls from Costa Rica and at detecting for the first time in the country BLV DNA in bull semen. Between May 2011 and August 2018, 379 blood and 133 semen samples were collected from bulls distributed in 118 farms. The serum was analyzed by an enzymatic immunoassay and the semen by polymerase chain reaction and sequencing. BLV seropositivity was 43.5% (165/379), while 64.4% (76/118) of the farms had positive reactors. Holstein (75.7%) and Jersey (73.0%) breeds showed the highest seropositivity. In addition, Bos taurus bulls (68.1%), older than seven years (50.0%), and those belonging to dairy farms (75.5%) had higher seropositivity compared to Bos indicus (17.7%), younger than seven years (42.2%), and those from beef farms (15.5%), respectively. Moreover, Bos taurus bulls had a higher risk of being seropositive than Bos indicus (OR = 3.4; 95% CI: 1.7–6.8). BLV DNA was found in one semen sample (2.5%; 1/40) from a seropositive bull. The importance of serum and molecular BLV screening in semen samples and the potential role of some risk factors associated with the disease, such as the bull’s age, genotype, and type of livestock productive system, is argued in the present report.
... Andorra 1994 [85] Cyprus 1995 [85] Czech Republic 2010 [85] Finland 2008 [85] Ireland 1999 [85] Norway 2002 [85] Spain 1994 [85] UK 1996 [85] The Netherlands 2009 [86] Sweden 2007 [85] Denmark 1990 [85] Estonia 2013 [85] [109] Israel (5% at individual) [110] Iraq (7% of dairy) 2015 [111] Egypt (17.7% of dairy) 2020 [112] Viruses 2021, 13 ...
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.
... Additionally, BLV infection affects the immune system of the animals, which can have a more significant impact on the general health of the herd than the direct losses associated with the development of lymphomas (Trainin & Brenner, 2005). According to Della Libera et al. (2015), although BLV has tropism by B lymphocytes, the virus may affect the innate and adaptive immune response, because these systems display many common effector mechanisms. ...
There are several factors affecting global milk production leading to severe economic losses. Mastitis and leukosis are highly prevalent diseases especially in Brazilian cattle herds. The present study aimed to evaluate the correlation between mastitis and the bovine leukemia virus (BLV) infection in naturally infected cows belonging to dairy herds in Minas Gerais State. Additionally, the prevalence of both diseases, pathogens causing mastitis, and their association with BLV infection and persistent lymphocytosis were evaluated. The prevalence of BLV was determined using the agar gel immunodiffusion test (AGID) in 1,392 lactating cows from ten dairy herds. From the AGID results, 240 cows were selected and divided into two experimental groups: A case group composed of 160 BLV-positive cows (BLV-P) and the control group of 80 BLV-negative cows (BLV-N). Based on serological and leucocytic evaluations, the animals were classified into three subgroups: BLV-N, BLV-P without persistent lymphocytosis (BLV-PWPL), and BLV-positive with persistent lymphocytosis (BLV-PPL). The California Mastitis Test (CMT) was performed on days 0 (D0) and 60 (D60) in the subgroups and the milk from CMT-positive glands were analyzed. BLV infection was present in 100% of herds, with an overall prevalence of 80.9% in cows older than 24 months. Among BLV-P animals, 74% were classified as BLV-PWPL and 26% as BLV-PPL. Coagulase-negative Staphylococcus (73.30%),Corynebacterium spp. (12.04%), Streptococcus agalactiae (8.90%), and Staphylococcus aureus (5.76%) were predominant (61.41%). There were no statistical differences among the scores of clinical or subclinical mastitis with the pathogen type (contagious or environmental) in the BLV-PWPL or BLV-PPL subgroups. However, BLV-P animals showed higher CMT scores than BLV-N animals, suggesting a higher redisposition to subclinical mastitis in cows affected by leukosis.
... In addition, less than 6% of cattle got BLV infection such as in Mongolia, 3.8% [19], Taiwan 5.8%, and Cambodia 5.3%. On comparing with other Middle East findings, the reported rate was higher than other rates reported in Israel 5% [37] and Saudi Arabia 20.2% [38]. ...
Simple Summary
Bovine leukemia virus (BLV) is distributed worldwide and affects dairy cattle causing significant economic losses. This study’s objective was to assess the risk factors associated with BLV infection and identify the Egyptian BLV strain’s genetic diversity. The overall seroprevalence of BLV infection in Egyptian dairy cattle was 18.2%, and the grazing cattle in the losing house system had a higher probability of getting BLV infection. The sequencing and phylogenetic analysis for one Egyptian BLV strain was performed, and the obtained results confirmed the clustering of Egyptian BLV strain into genotype-1.
Abstract
Bovine leukemia virus (BLV) is distributed worldwide and affects dairy cattle causing severe economic losses. The BLV has been serologically reported in Egypt, but few studies have evaluated its associated risk factors and genetic classification. Therefore, this study assessed risk factors associated with BLV infection and identified the genetic diversity of the Egyptian strain. The study was conducted on 500 dairy cattle distributed in four Governorates located in Northern Egypt. Overall, the seroprevalence of BLV infection among Egyptian dairy cattle was 18.2%. The grazing cattle in the losing house system had higher odds for BLV seropositivity, and bad practice such as the use of a single needle or one plastic glove for more than one animal was considered a significant risk factor for BLV infection. Besides, the sequencing and phylogenetic analysis for one Egyptian BLV strain was performed, and the obtained results confirmed the clustering of Egyptian BLV strain into genotype-1. The assessment of associated risk factors for BLV infection and determination of its genetic classification are essential to implement an effective control program.
... Bovine lymphoma is the most common neoplasm in milk-producing regions and is an important cause of economic loss in this industry in several parts of the world (Jacobs et al. 2002, Trainin & Brenner 2005. This neoplasm was appointed as one of the main causes of death in dairy cows in southern Brazil, in addition to being the most frequent neoplastic disease (Mello et al. 2017). ...
Clinical and pathological features of bovine lymphoma involving the spinal cord were evaluated through a retrospective study of the necropsy database from 2005 to 2017. Thirty-four cases of bovine lymphoma were found, 24 of which had central nervous system involvement restricted to the spinal cord. All cattle were Holstein cows 2.5-12 years-old (median age, six years-old). The clinical course was 7-21 days, and the main neurological sign was pelvic limb paresis (81.8%). The lymphoma often affected the spinal cord in a multifocal manner. Lumbar segments were the mostly affected sites (23/24), followed by the sacral segments and cauda equina (20/24), cervical (5/24) and thoracic (5/24) segments. Tumors were in the epidural space, peripheral to the pachymeninges (extradural) and between layers of adipose tissue. In addition, two cases had progressive hemorrhagic myelomalacia. Further organs affected included the lymph nodes (100%), abomasum (79.2%), heart (75%) and kidneys (45.8%). Microscopically, all lymphomas had a diffuse pattern, with no meningeal or medullar infiltration. According to the REAL/WHO classification, all these neoplasms were mature B-cell lymphomas. Diffuse large B-cell lymphoma (DLBCL) was observed in 95.8% (23/24) of the cases. The following subtypes were observed in the DLBCL group in descending order: immunoblastic (60.9%, 14/23), centroblastic (26.1%, 6/23), anaplastic (8.7%, 2/23) and T-cell rich (4.3%, 1/23).
... It therefore appears that BLV may be eroding the profitability and long-term sustainability of US dairy farms in ways that were unappreciated in previous decades when the US and many other nations opted not to control BLV [7,22,[37][38][39][40]. It has been over a decade since the last national estimate of US BLV prevalence was made [8,12]. ...
Objective
To estimate current US herd-level and animal-level prevalence of bovine leukemia virus (BLV) in dairy cows and characterize epidemiologic features.
Design
Cross-sectional observational study design and survey.
Animals
4120 dairy cows from 103 commercial dairy herds in 11 states across the US.
Procedures
Milk samples were collected from dairy cows through routine commercial sampling and tested for anti-BLV antibodies by antibody capture ELISA. Based on the ELISA results of a sample of an average of 40 cows per herd, within-herd apparent prevalence (AP) was estimated by a directly standardized method and by a lactation-weighted method for each herd. Within-herd AP estimates were summarized to give estimates of US herd-level and animal-level AP. Differences in AP by lactation, region, state, breed, and herd size were examined to characterize basic epidemiologic features of BLV infection.
Results
94.2% of herds had at least one BLV antibody positive cow detected. The average within-herd standardized AP was 46.5%. Lactation-specific AP increased with increasing lactation number, from 29.7% in first lactation cows to 58.9% in 4th and greater lactation cows. Significant differences were not observed based on region, state, breed, or herd size.
Conclusions and Clinical Relevance
These results are consistent with a historical trend of increasing prevalence of BLV among US dairy cattle. Given the findings of other studies on the negative impacts of BLV infection on milk production and cow longevity, these findings are clinically relevant for veterinarians counseling dairy clients on the risks of BLV to their herds.
... BLV infections in Middle Eastern countries are relatively low. The prevalence of BLV infection is approximately 5% in Israel [140], while in Saudi Arabia, 20.2% of dairy cattle tested as BLV-positive [141]. Compared to these countries, BLV infection rates in Turkey are higher, with 48.3% of dairy herds including seropositive animals [142]. ...
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.
... This intense immune response should be regarded with some caution, because a high level of anti-BLV antibodies not necessarily means an optimal humoral immune response to the virus (Z. Trainin & J. Brenner [41], H. Ungar-Waron et al. [42]). The phenomenon is explained by some "defects" in the structure of immunoglobulins M and G synthesized in BLV presence, which prevents them from reacting effectively with viral structures (Z. ...
The aim of the present paper was the comparative assessment of two ELISA tests on serum and milk samples and agar gel immunodiffusion test (AGID) regarding ability to detect enzootic bovine leukosis (EBL) in Timis County, according to farm type, age, breed and stage of lactation, and how these parameters affect the humoral immune response of positive cattle. Serum samples were analyzed using blocking ELISA and AGID, and the milk samples by indirect ELISA, calculating quality parameters of applied tests. The obtained results showed that AGID detected 43 positive cattle and the two ELISAs 51 positive animals. Performances of AGID were influenced by farm type, age and serum antibody level. It was established that cattle aged 3-6 years were most prone to develop EBL. The level of serum antibodies has been influenced by farm type, age and lactation phase, and milk antibodies level strictly by the phase of lactation; the lowest values of milk antibodies were registered between 2nd and 8th month of lactation. Consumption of insufficiently heat-treated milk from BLV positive cattle in 2-8 months of lactation is associated with increased risk of infection in humans.
... In some regions (Razgrad, Targovishte, Vidin, Plovdiv) the number of infected animals increased several times as compared to 2009, while in others (Rousse, Haskovo, Burgas, Kyustendil, Pleven) there was a tendency towards decrease. The most numerous EBL foci were in the region of Burgas (162), followed by Stara Zagora (152) and Shoumen (149), and the fewest -in the region of Sofia (10), Pazardzhik (22) and Kyustendil (31). With regard to the geographical prevalence of the infection, it was more frequently seen in North Bulgaria than in South Bulgaria. ...
The Enzootic bovine leukosis (EBL) is broadly spread on all continents. Due to the lack of specific means
for prevention and treatment, it turns to be a serious health and economic issue for a number of countries with
developed cattle farming. The aim of the present study was to establish the prevalence of EBL in Bulgaria in 2012
and the effect of the application of the State Programme for Infection Prevention and Control. Official data from the
annual report of the Bulgarian Food Safety Agency (BFSA) and serological analyses for enzootic bovine leukosis
conducted with commercial ELISA kits was employed. The results were statistically analysed using the method
for comparison of independent proportions. The analysis of results from serological EBL survey performed in
2012 showed a high prevalence of the infection in Bulgaria (33.38% on the average) and more than 2000 foci.
In the different regions of the country, the proportion of infected animals varied from 13.05% to 63.85%. After
implementation of the mandatory measures for enzootic bovine leukosis prevention and control, one region
was completely freed from enzootic bovine leukosis and 78 infection foci were eradicated. The results from the
serological analyses for enzootic bovine leukosis performed in 2012 showed a wide prevalence of the infection in
Bulgaria. The successful eradication of cattle farms is possible with strict implementation of the State Programme
for EBL Prevention and Control and co-funding by the European Community.
... The immune response in BLV-infected cows could be either depressed or being triggered by an antigenic stimulus leading to the expression of incomplete or aberrant antibodies. These studies showed that the susceptibility of BLV-infected cows to other infectious diseases was increased [21]. ...
In the present study, serum samples of 1984 milking cows stemming from 6 dairy herds located in various regions of Turkey were screened for neutralizing antibodies against BHV1 and BVDV using serum neutralization technique and for antibodies against BLV using agar gel immunodiffusion technique. The seropositivity rates of BLV, BHV1 and BVDV infections were 37.15%, 72.18% and 47.93% respectively. The BLV and BHV1 seroprevalences significantly differed according to the age, the 2 year old animals being more resistant. Furthermore, significant interactions between the BLV and the 2 other viruses were evidenced by the chi-square method in the overall cow population and specifically in 4 dairy herds for the association of BLV with BHV1.
... Although most infected animals are asymptomatic, the disease may cause considerable economic losses. Import restrictions placed on cattle, semen, and embryos generate losses not only to artificial insemination centers and exporters, but also to dairy and meat industry (TRAININ; BRENNER, 2005). Economic losses result from slaughterhouse condemnation of carcasses with lymphoid tumors, treatment of sick and replacement of dead animals (CHI et al., 2002;PELZER, 1997). ...
The aim of this study was to evaluate the effects of bovine leukemia virus (BLV) infection on productive performance of dairy cattle in Brazil. A total of 158 blood samples from lactating adult cows, purebred Holstein and crossbred Holstein X Zebu, were analyzed by Agar Gel Immunodifusion Test (AGID) and leukogram. According to AGID and leukogram results, animals were grouped into three categories: seronegative, seropositive without persistent lymphocytosis, and seropositive with persistent lymphocytosis. Milk production data were compared between groups, according to breed. BLV infected females showed lower milk yield than uninfected ones, both purebred and crossbred ones. There was no difference between milk yield of seropositive cows with or without persistent lymphocytosis. These results indicate an association between BLV infection and reduction of milk production, and this study is the first one to show these effects in crossbred Holstein X Zebu cows.
... The prevalence rates that were determined in this study are considerably lower than those reported in different regions of the world. Our result is consistent with other reports which indicate that the prevalence of BLV infection in Middle East countries is lower than that in other regions of the world (Hafez et al. 1990;Meas et al. 2000;Pourjafar et al. 2004;Trainin and Brenner 2005;Tan et al. 2006). A possible explanation for the lower prevalence detected in Turkey is the effect of herd size. ...
Enzootic bovine leukosis (EBL) which is caused by bovine leukaemia virus (BLV) has an important economic impact on dairy herds due to reduced milk production and restrictions on livestock exports. This study was conducted to determine the BLV infection status in Central Anatolia Region of Turkey, an important milk production centre, and to examine the risk factors such as purchasing cattle, increasing cattle age, cattle breed and herd size associated with transmission of BLV infection. To estimate the rate of BLV infection, a survey for specific antibodies in 28,982 serum samples from animals belonging to 1116 different herds situated in Central Anatolia Region of Turkey were tested from January 2006 to December 2013. A generalized mixed linear model was used to evaluate the risk factors that influenced BLV seroprevalence. Antibodies against BLV were detected in 431 (2.28 %) of 18,822 Holstein and 29 (0.28 %) of 10,160 Brown Swiss cows. Among 1116 herds, 132 herds (11.82 %) had one or more positive animals. Also results of our study show that the prevalence of BLV infection increased from 2006 to 2011, and it tends to reduce with BLV control programme. Furthermore, we found positive associations between percentage of seropositive animal and increasing cattle age, herd size, cattle breed and purchased cattle. Age-specific prevalence showed that BLV prevalence increased with age. These factors should be taken into consideration for control of BLV infection.
... However, PL is a benign side effect of BLV infection, it is not a disease per-se, but can cause hypogammoglobinemia and increased bacterial infections. The economic impact of PL is controversial, and may depend on the milking and culling practices of a particular dairy farm (Trainin & Brenner, 2005). The remaining 1/3 of lymphoma/leukemia cases come form the 60% of BLV-infected cattle that have a normal blood profile (Ferrer et al., 1978). ...
Ninety three years after Siedamgrotzky first reported cases of bovine lymphocytic malignancies in Germany in 1876, bovine leukemia virus (BLV) was identified in cultured neoplastic cells from affected cattle. Epidemiological studies carried out in herds with a high frequency of mature B-cell lymphoma/leukemia proved that BLV was the causative agent of these diseases and also of persistent lymphocytosis (PL). This latter condition results in the benign expansion of BLV-infected peripheral blood B-cell lymphocytes. BLV is identified in almost every case of bovine B-cell lymphoma/leukemia; however, less than 10% of BLV-infected cattle develop these diseases, while about 30% of BLV-infected animals develop PL. Early observations of the increased incidence of Bcell lymphocytic neoplasias or PL in certain bovine pedigrees, but not in others, suggested that host-genetic factors were involved in the development of these conditions after BLV-infection. There were also indications that host-genetic factors influenced the susceptibility to one condition or the other independently. Epidemiological data also indicate that 2/3 of all cases of B-cell neoplasia occur in cattle with pre-existing PL, while 1/3 of cases come from animals with a normal blood profile. The major histocompatibility complex of cattle, termed Bovine Lymphocyte Antigens (BoLA) was discovered in 1978. The BoLA complex is a multiallelic or polymorphic genetic region located on chromosome 23 at band 22, and is organized into class I, II, and III genes, which encode proteins with different tissue distributions and functions. B-lymphocytic leukemia/lymphoma, PL and even the number of BLV-infected peripheral blood lymphocytes were subsequently found to be associated with certain BoLA-genotypes. Due to the wide dissemination of BLV among dairy cattle in Argentina and other countries, control and eradication programs based on the serological detection of BLVinfected cattle and the subsequent culling of infected animals has several drawbacks. A new approach to classify BLV-infected Holstein cattle belonging to high prevalence BLV-infected herds was recently reported. Two BLV-infection profiles: low and high proviral load (LPL and HPL, respectively) showed a strong association with certain BoLA-DRB3.2 polymorphisms. LPL was more frequently associated with BoLADRB3.2* 0902, and HPL with BoLA-DRB3.2*1501 or 03. Further experimentation has indicated that these alleles are good candidates for genetic markers of resistance or susceptibility to BLV transmission, and would serve as powerful tools toward controlling BLV dissemination by marker assisted breeding of genetically-selected cattle. The dynamic between BLV and the BoLA complex should serve as a model for studying the interaction between host and virus. Such understanding should prove important to, not only veterinary medicine, but also to human oncology, wherein human T-cell lymphoma/leukemia virus, a member of the same genus of retroviruses as BLV, causes T-lymphocytic malignancies.
... These signs include tumours in lymphoid tissues, decreased milk production, enlarged lymph nodes, loss of appetite, weight loss, fever, rear limb weakness or paralysis, gastrointestinal obstructions *Corresponding author: Faham Khamesipour; Under Graduated Student of Veterinary Medicine, College of Veterinary Medicine, Islamic Azad University, Shahrekord Branch, Shahrekord, Iran; Tel.: 00989134132858 protruding eyeballs and increased blood lymphocytes counts (Motton and Buehring, 2003;Ott et al., 2003). Because BLV infection affects directly the immune system, its power on herd health and economy could be more extensive than direct loss from death of a single individual following lymphomas (Trainin and Brenner, 2005;Hanuš et al., 2007;Janu et al., 2007). Cellular damages could force cells to shed free DNA into body fluids. ...
Bovine Leukemia Virus (BLV) is a causative agent of bovine leukosis responsible for lymphoproliferative
disorders in cattle. The aim of this study was to detect the BLV in the frozen semen samples of Iranian bulls used for artificial insemination using PCR. A total of 45 frozen Semen samples were obtained from 45 bulls used for artificial insemination centres. DNA was extracted and 385 bp fragment of the gag gene of the virus was visualized in a 1% agarose gel electrophoresis. Viral DNA was detected in nine of 45 (20%) frozen semen samples of bull’s that were used for artificial insemination. The results of this study demonstrated the high prevalence of BLV DNA in frozen semen samples of bulls. According to this finding it is clear that testing, segregation and culling programs can be effective in the control and prevent the bovine leukosis disease caused by BLV. Furthermore, examination of cattle semen samples that are used for artificial insemination is necessary to prevent the spread of BLV in this region.
... Generally, European countries used options 3 and 4 to achieve national BLV eradication; however, the prevalence of BLV in those countries was typically much lower than that in the United States. 41,82 Further study is necessary to determine the effectiveness of specific management practices (Table 2) for preventing BLV transmission and reducing BLV prevalence. ...
The subclinical impact of bovine leukemia virus (BLV) on the sustainability of the US dairy industry is only now being fully recognized. Findings of recent longitudinal studies conducted in Michigan dairy herds were consistent with the results of previous studies in showing that within-herd prevalence of BLV-infected cattle was negatively associated with milk production and cow longevity. Risk factors relating to routes of hematogenous transmission such as the use of shared hypodermic needles, shared reproductive examination sleeves, and natural breeding were associated with BLV within-herd prevalence. Few US dairy producers know the prevalence of BLV-infected cattle in their herds or are aware of the insidious economic impact of BLV or the options for BLV control. As an increasing number of countries eradicate BLV from their cattle populations, restrictions on the movement of US cattle and cattle products will likely increase. Veterinarians should be aware of recent developments for screening serum and milk samples for antibodies against BLV and the results of research regarding the economic impact of BLV so they can advise their dairy clients of available alternatives for monitoring and controlling BLV infection.
... Although infection with BLV of the udder reduces productivity 3 , it is more logical that deterioration of the well-being of the BLV infected cow results from the detrimental effect on the immune system of the animal, and more so in PL + cows. This immune impairment causes increased susceptibility to infectious diseases mostly in subclinical terms, which leads to decreased milk production and slight decreased reproductivity 24 . ...
Some production parameters of seropositive cows (age, first calving age, 305 day mature equivalent last milk yield production, lifetime mature equivalent milk yield production, lifetime total milk production, lifetime total milking period, lifetime monthly milk production, lifetime daily milk production, lifetime total days of milking, number of inseminations per pregnancy (for last pregnancy), number of calves and calving interval (for last pregnancy)) were analysed in the current study. The study population was clinically healthy Holstein cows from a commercial dairy herd in southern Turkey. Of 109 animals, 65 cows were seropositive by ELISA and the prevalence of bovine leukemia virus (BLV) infection was 59.6%. The prevalence of seropositive cows in 2nd (62.8%), 3rd (64.7%), 4th (61.5%), and 5th (66.6 %) lactations was slightly higher than that of cows in 1st (52.6%) lactations. No statistical differences were observed between BLV seronegative and seropositive cows for production and reproduction parameters analysed in this study (P > 0.05).
Simple Summary
Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis (EBL), which is the most significant neoplastic disease in cattle. EBL is often overlooked in daily breeding processes due to the absence of obvious clinical symptoms. However, studies have revealed that EBL can severely impact the production performance of dairy cows, leading to a substantial economic burden on the cattle industry. In recent years, the global prevalence of EBL has been on the rise, and fragments of BLV nucleic acid have been detected in human breast cancer patients, raising public concerns. Due to the absence of an effective vaccine, controlling the disease is challenging. This review aims to provide a comprehensive overview of BLV, including its role in causing EBL, the genome of BLV, its current prevalence, transmission routes, clinical symptoms, detection methods, hazards, control strategies, and the current state of BLV research. The primary objective of this review is to offer breeders and researchers reliable veterinary knowledge on BLV and identify future research directions in this field.
Abstract
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.
Enzootic bovine leukosis (EBL) is an infectious disease caused by bovine leukemia virus (BLV) that affects cattle worldwide. Agar gel immunodiffusion (AGID) was the reference test for EBL diagnosis for many years, but enzyme-linked immunosorbent assay (ELISA) showed higher sensitivity, was faster to perform, and resulted in an objective reading. However, the importation of ELISA kits is lengthy and expensive, and currently, no AGID kits are available in Brazil. The aim of this work was to standardize an indirect ELISA (iELISA) for EBL diagnosis using BLV antigens produced in Tadarida brasiliensis lung (Tb1Lu) cells, which are Bovine viral diarrhea virus (BVDV) free, unlike fetal lamb kidney (FLK) cells, currently used for this purpose. Following standardization, iELISA results were compared with those obtained by AGID and the commercial Chekit Leucose-Serum ELISA. Compared to AGID, iELISA had 94,44% sensitivity, 75.68% specificity, 79.10% positive predictive value (PPV) and 93.30% negative predictive value (NPV), with 84% concordance and a Kappa index of 0.699. Compared to the Chekit Leucose-Serum ELISA, iELISA showed 92.60% sensitivity, 87.09% specificity, 90.27% PPV and 90,00% NPV, with 90.27% concordance and a Kappa index of 0.801. Taking into account the high agreement with the traditional tests and the absence of non-specific reactions with BVDV, the developed assay could be used as diagnostic method to control EBL in Brazil.
The mechanisms of leukemogenesis induced by bovine leukemia virus (BLV) and the processes underlying the phenomenon of differential host response to BLV infection still remain poorly understood. The aim of the study was to screen the entire cattle genome to identify markers and candidate genes that might be involved in host response to bovine leukemia virus infection. A genome-wide association study was performed using Holstein cows naturally infected by BLV. A data set included 43 cows (BLV positive) and 30 cows (BLV negative) genotyped for 54,609 SNP markers (Illumina Bovine SNP50 BeadChip). The BLV status of cows was determined by serum ELISA, nested-PCR and hematological counts. Linear Regression Analysis with a False Discovery Rate and kinship matrix (computed on the autosomal SNPs) was calculated to find out which SNP markers significantly differentiate BLV-positive and BLV-negative cows. Nine markers reached genome-wide significance. The most significant SNPs were located on chromosomes 23 (rs41583098), 3 (rs109405425, rs110785500) and 8 (rs43564499) in close vicinity of a patatin-like phospholipase domain containing 1 (PNPLA1); adaptor-related protein complex 4, beta 1 subunit (AP4B1); tripartite motif-containing 45 (TRIM45) and cell division cycle associated 2 (CDCA2) genes, respectively. Furthermore, a list of 41 candidate genes was composed based on their proximity to significant markers (within a distance of ca. 1 Mb) and functional involvement in processes potentially underlying BLV-induced pathogenesis. In conclusion, it was demonstrated that host response to BLV infection involves nine sub-regions of the cattle genome (represented by 9 SNP markers), containing many genes which, based on the literature, could be involved to enzootic bovine leukemia progression. New group of promising candidate genes associated with the host response to BLV infection were identified and could therefore be a target for future studies. The functions of candidate genes surrounding significant SNP markers imply that there is no single regulatory process that is solely targeted by BLV infection, but rather the network of interrelated pathways is deregulated, leading to the disruption of the control of B-cell proliferation and programmed cell death.
The HIV-1 matrix (MA) domain mediates proper Gag localization and membrane binding by interacting with phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2], a plasma membrane(PM)-specific phospholipid. HIV-1 MA also interacts with RNA, which prevents Gag from binding to membranes containing phosphatidylserine (PS), a prevalent negatively charged phospholipid. These results suggest that the MA-bound RNA promotes PM-specific localization of HIV-1 Gag by blocking non-specific interactions with membranes that do not contain PI(4,5)P2.
In this thesis, I examined whether PI(4,5)P2 dependence and RNA-mediated inhibition collectively determine MA phenotypes across a broad range of retroviruses. By comparing a panel of Gag-leucine-zipper constructs (GagLZ) containing MA of different retroviruses, I found that membrane binding mediated by retroviral MA can be broadly divided into two categories: those that are PI(4,5)P2-dependent and RNase responsive, and those that are neither. I also found that the PM-localization and virus-like particles (VLP) release of the former group is sensitive to the overexpression of a PI(4,5)P2-
depleting enzyme, polyphosphoinositide 5-phosphatase IV (5ptaseIV), while the latter group is much less sensitive to 5ptaseIV overexpression. Structural analyses further suggest that the basic patch size of the retroviral MA confer susceptibility to RNA-mediated membrane binding inhibition.
In my thesis, I also provided in vitro and cell-based evidence supporting that RNA-mediated suppression occurs in cells and that RNA can inhibit membrane binding of HIV-1 Gag at a concentration that is much lower than the estimated RNA concentration in the cell. Hence, RNA-mediated suppression is a physiologically relevant mechanism that prevents Gag from binding promiscuously to prevalent PS-containing membranes.
Finally, I examined the roles of PI(4,5)P2 and RNA in regulating the targeting of HIV-1 Gag to the site of assembly, the virus-containing compartments (VCC), in primary macrophages. I found that the VCC localization and virus release of HIV-1 are severely impaired upon 5ptaseIV overexpression. However, HIV-1 MA contributes only to membrane binding but not in Gag targeting to the VCC. I also determined that HIV-1 nucleocapsid (NC) is important for VCC-specific localization of HIV-1 Gag. This suggests that targeting of HIV-1 Gag to the VCC adopts a different mechanism than Gag targeting to the PM in HeLa and T cells.
Bovine leukemia virus (BLV) is a retrovirus closely related to the human T-lymphotropic virus type 1 (HTLV-1). BLV is a major animal health problem worldwide causing important economic losses. A series of attempts were developed to reduce prevalence, chiefly by eradication of infected cattle, segregation of BLV-free animals and vaccination. Although having been instrumental in regions such as the EU, these strategies were unsuccessful elsewhere mainly due to economic costs, management restrictions and lack of an efficient vaccine. This review, which summarizes the different attempts previously developed to decrease seroprevalence of BLV, may be informative for management of HTLV-1 infection. We also propose a new approach based on competitive infection with virus deletants aiming at reducing proviral loads.
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