Effects of bovine leukemia virus infection on crossbred and purebred dairy cattle productive performance in Brazil

Rajão, Daniela S.; Heinemann, Marcos Bryan; Reis, Jenner Karlisson Pimenta dos; Braz, Gissandra Farias; Haddad, João Paulo Amaral; Ribeiro, A. C. C. L.; Leite, Rômulo Cerqueira

doi:10.5433/1679-0359.2014v35n2p891

Cited by 7 publications

(5 citation statements)

References 22 publications

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“…The ratios of BLV-PWPL and BLV-PPL observed among BLV infect animals were also similar to a previous study that reported persistent lymphocytosis affects 20% to 30% of BLV-P animals (Birgel et al, 2006). The high prevalence and infection rates for bovine leukosis in the studied properties, ranging from 21.43% to 64.28%, showed the high infectivity of the BLV, which can be afforded by intensive management practices and the absence of prophylactic measures to prevent the horizontal dissemination of BLV in dairy cattle as related in previous studies (Kobayashi et al, 2014;Rajão et al, 2014).…”

Section: Screening Of Animals and Prevalence Of Bovine Leukosissupporting

confidence: 58%

“…These animals generally present a higher probability of BLV infection because of the longer exposure time in infected herds and risks associated with lack of control procedures. (Birgel et al, 2006;Rajão et al, 2014). This also explains the result for the association between the number of parturitions and BLV infection, with a higher prevalence of BLV in animals with four or more lactations (Table 2).…”

Section: Screening Of Animals and Prevalence Of Bovine Leukosismentioning

confidence: 77%

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Intercurrence between bovine leukosis virus infection and mastitis in dairy cattle

Hirsch¹,

Rocha²,

Bruhn³

et al. 2021

Semina: Ciênc. Agrár.

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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.

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Section: Screening Of Animals and Prevalence Of Bovine Leukosissupporting

confidence: 58%

Section: Screening Of Animals and Prevalence Of Bovine Leukosismentioning

confidence: 77%

Intercurrence between bovine leukosis virus infection and mastitis in dairy cattle

Hirsch¹,

Rocha²,

Bruhn³

et al. 2021

Semina: Ciênc. Agrár.

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“…Seroreactive animals to EBL are more susceptible to developing infectious diseases such as mastitis due to the immunosuppression caused by the virus [17]. The positive correlation between EBL and the presence of mastitis (both clinical and subclinical) indicates that the higher the number of reactive animals in a herd, the greater will be the presence of mastitis [23].…”

Section: Introductionmentioning

confidence: 99%

Seroprevalence and Influence of Bovine Leukemia Virus on the Incidence of Mastitis in Dairy Herds

Almeida

Barioni

et al. 2021

Acta Scientiae. Vet.

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Background: The enzootic bovine leukosis (EBL) is a viral disease with a chronic aspect and its etiological agent is an oncogenic deltaretrovirus called bovine leukemia virus (VLB). It has a wide distribution in dairy cattle herds, and it may take several years before the first clinical manifestations occur. Animals seropositive for VLB are more susceptible to developing infectious diseases such as mastitis. The objective of this study was to evaluate the seroprevalence of EBL, the prevalence of mastitis, the possible association between leukosis and mastitis, and the risk factors related to leukosis in municipalities of the Caparaó region of Espírito Santo, Brazil.Materials, Methods & Results: The prevalence of enzootic bovine leukosis and its association with mastitis were evaluated in an 854 clinically healthy crossbred (Bos tauros tauros x Bos taurus indicus) dairy cows were used, in different lactation phases, from farms located in the 12 municipalities that compose the Caparaó Capixaba micro-region, in the southern part of Espírito Santo, Brazil, in the period from February to July 2015. The seroprevalence of EBL was determined by the agar gel immunodiffusion test, the presence of clinical mastitis was ascertained by the black background mug test and of subclinical mastitis by the CMT. The reuse of needles, type of milking, reproductive management, calf mortality, presence of reproductive problems and milk yield were the risk factors assessed. The association between the variables was estimated by the odds ratio (95% confidence interval). The significance of the associations was determined by the Chi-square test. The prevalence of EBL, clinical and subclinical mastitis was 56.79%, 5.50% and 43.55%, respectively. There was a positive association between the EBL virus and the presence of subclinical mastitis (P < 0.05, OR = 1.41, CI = 1.07-1.86). The reuse of disposable needles (OR = 1.92, CI = 1.46-2.53), mechanical milking (OR = 2.03, CI = 1.34-3.08), calf mortality (OR = 2.39; CI = 1.25-4.55) and the presence of reproductive problems (OR = 1.62; CI = 1.23-2.14) were considered risk factors associated with LEB (P < 0.05).Discussion: Enzootic bovine leukosis is disseminated in the dairy herds in the municipalities the study. The lack of knowledge about EBL among farmers and the failure to adopt measures for its control and elimination favor the appearance of new cases in the herd. Factors such as animal age, absence of exams when purchasing animals, reuse of gloves for rectal palpation and needles, contribute to dissemination of the infection. The economic losses associated with subclinical mastitis can even be greater than those caused by clinical mastitis. The differences for prevalence of clinical mastitis can be associated with the breeding system, type of management, intensification and level of production. In this context, we noted a much larger number of animals with subclinical infection, where the losses may not be perceptible to the farmers. It is concluded that EBL is widespread in dairy herds of the municipalities of Caparaó Espírito Santo's region. The prevalence of clinical and subclinical mastitis is high in some cities surveyed. The presence of EBL increases the chances of developing subclinical mastitis. The reuse of disposable needles and mechanical milking were considered risk factors associated with EBL. Seroreagent animals for EBL are more likely to present calf mortality and reproductive problems. It is necessary to discuss the best sanitary management system for the region, with a better economic and social response and then carry out the elaboration of educational and implementation measures, through technical assistance.

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“…This could be due to low infection rates, as only 7% of animals in that study were seropositive. It is important to mention that the high numbers of animals with lymphocytosis identi ed in our study cannot all be associated with BVL infection, as at least three continuous samplings are required to determine persistent lymphocytosis [44] and this was not done in our study. The use of real-time PCR allowed us to identify proviral loads across study groups (cattle with and without lymphocytosis, tissues with lymphoma) however we did not nd statistically signi cant differences between them.…”

Section: Discussionmentioning

confidence: 98%

Genetic Analysis of the pX Region in Bovine Leukemia Virus genotype 1 in Holstein Friesian Cattle with Different Stages of Infection

Machuca

Pérez

Méndez

et al. 2021

Preprint

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The pX genetic region of the Bovine Leukemia Virus (BLV) includes four genes with overlapping reading frames that code for the Tax, Rex, R3 and G4 proteins. These proteins are involved in the regulation of transcriptional and post-transcriptional viral expression, as well as having oncogenic potential. Our goal was to determine the pathogenic role associated with BLV genotype 1 pX region genetics in terms of lymphocytosis, lymphomas and proviral load. We screened 724 serological samples from mixed-age Holstein Friesian cattle from six states in Mexico. Once peripheral blood leukocytes were isolated from whole blood with anticoagulant, we extracted genomic DNA using a commercial kit. Then, we designed in silico primers that hybridize in conserved regions of the BLV pX region, which allowed for PCR standardization to detect proviral DNA in infected cells. Positive amplicons were sequenced using the Sanger method, obtaining 1156 nucleotide-long final sequences that included the four pX region genes. The 30 heads of cattle that formed the genetic study population included 12 with lymphocytosis, 12 without lymphocytosis and six with lymphoma. Lymphoma presence was determined in six bovine tumor tissues using histopathology, and we identified BLV presence with in situ hybridization.Phylogenetic analysis determined that the 30 sequences were associated with genotype 1, and genetic distance between the sequences ranged from 0.2% - 2.09%. We identified two sequences in the G4 gene, one with a three-nucleotide deletion (AGU_7488L, in a cow with lymphocytosis), and one with a nine nucleotide deletion (AGU_18A, in a cow without lymphocytosis). PX region analysis identified positive selection in the G4, rex and R3 genes, and we found no difference in proviral load between the studied groups. It was not possible to establish an association between pX region variability and the development of lymphocytosis, lymphoma, asymptomatic status and proviral load in BLV-infected cattle.

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Effects of bovine leukemia virus infection on crossbred and purebred dairy cattle productive performance in Brazil

Cited by 7 publications

References 22 publications

Intercurrence between bovine leukosis virus infection and mastitis in dairy cattle

Intercurrence between bovine leukosis virus infection and mastitis in dairy cattle

Seroprevalence and Influence of Bovine Leukemia Virus on the Incidence of Mastitis in Dairy Herds

Genetic Analysis of the pX Region in Bovine Leukemia Virus genotype 1 in Holstein Friesian Cattle with Different Stages of Infection

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