Epidemiology, Infection Dynamics and Effective Control of Bovine Leukemia Virus Within Dairy Herds of Argentina PDF Download
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Author: Gustavo Enrique Monti
Publisher:
ISBN: 9789085042341
Category :
Languages : en
Pages : 164
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Author: Gustavo Enrique Monti
Publisher:
ISBN: 9789085042341
Category :
Languages : en
Pages : 164
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Author: Vickie J. Ruggiero
Publisher:
ISBN: 9781392118214
Category : Electronic dissertations
Languages : en
Pages : 154
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Book Description
Bovine leukemia virus (BLV) is an oncogenic deltaretrovirus of cattle that is estimated to infect more than 40% of U.S. dairy cows and cost the dairy industry hundreds of millions of dollars per year. BLV inserts a DNA copy (provirus) into the host genome and can cause leukemia and lymphoma in 1-5% of infected animals, while around 30% develop a non-malignant lymphocytosis, often coupled with high proviral load. BLV infection in dairy cows has also been associated with a number of economically important effects, such as decreased milk production, longevity, and immune function. The primary goal of this dissertation was to develop management protocols that can be implemented on U.S. dairy operations. We also aimed to further characterize in vivo immunologic effects of BLV infection, especially at mucosal junctions, hypothesizing that BLV+ cows would have lower concentrations of IgA antibody. To test the effect of BLV infection on total IgA concentrations, we analyzed the milk, saliva, and serum of BLV+ cows with varying lymphocyte count and proviral load profiles for comparison with BLV- herd mates. We found that BLV+ cows exhibited numerically lower concentrations of IgA in both milk and saliva, but not serum, in comparison to BLV- cows. Although the observed decreases were not statistically significant, the biological effects remain unknown. We also observed that the lowest concentrations of IgA were seen in the milk and saliva of BLV+ cows without lymphocytosis or high PVL, and these differences were trending toward significance. Our data, if confirmed, suggests that BLV may be disruptive to the immunology of mucosal junctions. We developed and implemented three field trials to evaluate management protocols for control of BLV in dairy herds. The first trial investigated the frequently suggested management intervention of improved medical hygiene by changing from shared needles and reproductive sleeves to single-use items. In this field trial, BLV- herd mates were assigned to control (re-use) or intervention (single-use) groups and the incidence risk was calculated semi-annually. Although we saw no difference in the risk of new infections in our study, medical hygiene may still play a role in the transmission of BLV as well as other diseases. This study also identified an increase in incidence risk in the summer exposure period. Meanwhile, our second field trial was a novel intervention which used milk ELISA screening to identify BLV+ cows for further characterization of their lymphocyte count (LC) and proviral load (PVL). In this manner, we identified cows thought to be the most infectious to their susceptible herd mates, and worked with herd managers to create a priority removal plan to consider when culling cows or implementing segregation measures. Overall, the three enrolled herds significantly reduced both BLV prevalence and incidence risk over a 2 to 2.5 year period. In this study, no significant associations with season were observed. Our final field trial aimed to demonstrate that milk ELISA testing could be used in herds with low BLV prevalence in order to identify and remove the few remaining BLV+ animals and achieve eradication of the virus. Two herds that were able to remove all BLV+ adult cows were generally successful, though the young stock (first lactation heifers) were a reservoir for reintroduction. In addition, we observed 5 first lactation heifers in one herd which had previously tested negative on serum ELISA but later tested positive on milk ELISA after entering the milking herd. This agrees with reports of latent BLV infections, and provides further evidence that long-term surveillance and further research on the infection dynamics of BLV are needed.
Author: Marie-Liesse Lassauzet
Publisher:
ISBN:
Category :
Languages : en
Pages : 386
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Author: Omid A. Nekouei
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The overall goal of the research described in this thesis was to lay a proper foundation for designing and conducting efficient control and eradication programs for infection with bovine leukemia virus (BLV) in the Canadian dairy industry. The objective in Chapter 2 was to identify potentially important risk factors for BLV infection in Canadian dairy herds. Of 272 study herds, from 8 provinces of Canada and tested during 1998-2003, 78% were BLV-positive. Over 15 management determinants for the infection were evaluated. Herds with clinical cases of leukosis during the 12 months prior to sampling, as well as herds which purchased animals with unknown BLV infection status in the last five years, had a significantly increased proportion of BLV-positive cows. Herds from eastern provinces and those not purchasing cows in the last five years were more likely to be free from BLV compared to western provinces and farms purchasing cows in the last five years. The objective in Chapter 3 was to determine the lifetime effects of BLV infection on milk production and longevity of dairy cows in Canada. Overall, 4052 cows from 348 herds were enrolled in a historical cohort study, based on test results from 1998-2003 and lactation and culling records post-testing until 2013. Positive cows to BLV had consistently greater probability of being culled (or dying) than the negative cows (over lifetime lactations 2-7). Only BLV-positive cows with short longevity (2 and 3 lifetime lactations) had a significantly lower lifetime milk production compared with their negative counterparts. As the cows lived longer (> 3 lactations), the difference in milk production between the two cohorts was no longer significant. The objectives of Chapter 4 were: 1) to assess the potential for carryover of antibodies against BLV in milk samples obtained from shared meters; and 2) to determine if adjustment of the diagnostic test cut-off value would improve the test characteristics for meter-collected milk ELISA results. The study included 236 paired milk samples from 8 dairy farms in Prince Edward Island collected in 2013. Two simultaneous milk samples, one hand-collected at the beginning of milking, and the other from the corresponding milk meter, were taken from all lactating cows that were milked at the selected meters. The sequence of cows using each meter was recorded. Carryover of BLV antibodies at shared milk meters was significant. For low-titer cows, the carryover effect was positively associated with the titer of the preceding cows. This could result in generating false-positive results in the BLV antibody-ELISA test on meter-collected samples from dairy herd improvement (DHI) procedures. Based on a new optimal cut-point, a suspicious category on the ELISA titers was defined, and a retest on the samples falling within this range was recommended to reduce the false positive rate. The objectives for Chapter 5 were: 1) to determine the prevalence of BLV infection at the herd level using a bulk-tank milk (BTM) antibody ELISA in the Maritime region of Canada ; and 2) to develop applied statistical models for predicting within-herd prevalence of BLV infection using the BTM antibody levels. To detect BLV infection and the antibody levels, a census was implemented on BTM samples from all dairy farms in the Maritime region in 2013 (3 monthly rounds of sampling on 623 farms). Another round of BTM sampling was coincided with individual cow sampling (all cows that contributed milk to the fourth BTM) in 90 selected herds. Herd-level prevalence of BLV in the Maritime region was 90.8%. In the individual testing, 30.4% of cows were positive. The statistical models developed in this study were able to predict true within-herd prevalence of BLV reasonably well based only on the BTM results. The model including all BTM tests (4 rounds of sampling) as the predictor had the best fit, although the models using 2 and 3 BTM tests provided similar results to 4 repeated tests. The focus for Chapter 6 was to assess the diagnostic performance of a commercially available ELISA for detecting BLV antibodies in BTM samples collected from dairy herds in Eastern Canada in 2013. Of 133 tested herds, 108 herds were found to be truly infected. At the resulting optimal cut-point, sensitivity and specificity of the BTM ELISA were estimated at 0.972 (0.921 - 0.994) and 1 (0.863 - 1), respectively. With the high prevalence of BLV infection across Canada and its detrimental economic impacts, pursuing broad-based control programs is necessary. All of the findings in the present research could contribute to designing and conducting efficient BLV control programs.
Author:
Publisher:
ISBN:
Category : Veterinary medicine
Languages : en
Pages : 1304
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Author: John A. Herrmann
Publisher: John Wiley & Sons
ISBN: 1119194490
Category : Medical
Languages : en
Pages : 363
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Book Description
Tackling One Health from a multi-disciplinary perspective, this book offers in-depth insight into how our health and the health of every living creature and our ecosystem are all inextricably connected. Presents critical population health topics, written by an international group of experts Addresses the technical aspects of the subject Offers potential policy solutions to help mitigate current threats and prevent additional threats from occurring
Author: Bianca Castiglioni
Publisher: MDPI
ISBN: 3036508961
Category : Science
Languages : en
Pages : 188
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Book Description
Wood surface attributes can be established by examining its several different physical or chemical properties. Differences in the wood surfaces occur between the manufacturing and post-treatment processes as well. Understanding how their unique anisotropic molecular organization, chemical linkages, branching, and other molecular features govern micro- and macroscale accessibility is essential for coating and complex modification processes. It is therefore important for scientific as well as practical reasons to qualify and quantify the effects of wood surface treatments and modifications. Challenges still exist to fully understanding the effect of the numerous applied chemicals and the wide range of treatment processes on wood surfaces.
Author: Mario Cleves
Publisher: Stata Press
ISBN: 1597180416
Category : Computers
Languages : en
Pages : 398
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"[This book] provides new researchers with the foundation for understanding the various approaches for analyzing time-to-event data. This book serves not only as a tutorial for those wishing to learn survival analysis but as a ... reference for experienced researchers ..."--Book jacket.
Author: Hans L. Rieder
Publisher:
ISBN:
Category : Tuberculosis
Languages : en
Pages : 180
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Author: H. H. Van Horn
Publisher: American Dairy Science Association
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 848
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