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Infectious bovine abortions: observations from an organized dairy herd.

ABSTRACT: Abortions in dairy animals can be caused by several infectious agents. Identification of the actual causal agent(s) is important for formulating suitable control strategies. A 3-year (2016-2018) longitudinal study was conducted in a dairy farm following an abortion storm in the mid- to late gestations. The investigation focused on the seven major infectious abortifacient in cattle, viz. bovine alphaherpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV), Neospora caninum, Brucella abortus, Coxiella burnetii, Leptospira Hardjo, and Listeria monocytogenes. High seroprevalence was observed for BVDV (79.4%), Leptospira (70.5%), BoHV-1 (53.5%), and Brucella (45.0%) at the beginning of the investigation (August 2016). The incidence proportion increased for BVDV, Leptospira, and Brucella in the following years of the investigation. A strong association of Brucella seropositivity with history of abortion (OR = 3.27) was recorded. Incidence of BoHV-1 reduced during the period of study coincident with systematic IBR inactivated marker vaccination of the herd. Sixty-four abortion cases were investigated for the identification of causative agent(s) by microbial culture, serological (ELISA), and molecular detection (PCR/ real-time PCR). Antibodies to BVDV, Brucella, BoHV-1, Leptospira, Neospora, and Coxiella were detected in 63, 61, 56, 35, 5, and 6 aborting cattle, respectively. Real-time PCR/PCR of clinical specimens detected DNA of Brucella, BoHV-1, Coxiella, Leptospira, and Listeria in 34, 13, 12, 9, and 4 abortion cases, respectively. BVDV and Neospora were not detected in any specimen samples. Brucella abortus isolated from the farm was determined as ST1 by multi-locus sequence typing (MLST). DNA of multiple agents were detected in 21 of the 64 cases (43.75%). Overall, the data suggests, Brucella was the major causative agent, although multiple causative agents circulated in the farm.

SUBMITTER: Sarangi LN

PROVIDER: S-EPMC7966683 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The present study was undertaken over a three year period (2012-2014) in an organized dairy farm located in North India to ascertain Brucella abortus as the putative cause of abortion. The dairy farm maintained cattle of Frieswal, Crossbred and Sahiwal breeds and followed calf-hood vaccination with Brucella abortus Strain 19 live vaccine in all the heifers. Even with the recommended vaccination schedule and good managemental practices in place, 88 cases of abortions clinically suspected of bovine brucellosis (40 from Frieswal breed, 17 from Crossbred cattle and 31 from Sahiwal breed) were reported from this farm. From these abortion cases, bacteriological isolation was possible in only four dams while 16 dams were found to be serologically positive in Serum Tube Agglutination Test (STAT). Molecular screening by PCR assay (specific for the bcsp31 gene of B. abortus) revealed that 24 dams were positive, out of which 20 were from Frieswal breed and rest four were from Crossbred herd. Prominently, all Sahiwal dams were found to be negative in bacteriological isolation and also in PCR assay. These results thus indicate towards the possibility of breed predisposition to abortions due to B. abortus infection. Statistical analysis by Fischer exact test (p < 0.01) too substantiated that breed susceptibility exists among these PCR positive cases. This study is novel as breed variation in abortions due to B. abortus in cattle is being documented for the first time. Seven representative PCR amplicons generated during the study were also sequenced and submitted to NCBI GenBank. Moreover, this study also accentuates the importance of PCR screening especially in vaccinated herd and raises concerns on over-dependence of serological assays when intensive vaccination is practised without any concomitant DIVA strategy. Thus, besides assisting in planning pragmatic control strategies against bovine brucellosis these findings are also imperative from 'One Health' context, also.

Project description:Mastitis imposes considerable and recurring economic losses on the dairy industry worldwide. The main objective of this study was to estimate herd-level costs incurred by expenditures and production losses associated with mastitis on Canadian dairy farms in 2015, based on producer reports. Previously, published mastitis economic frameworks were used to develop an economic model with the most important cost components. Components investigated were divided between clinical mastitis (CM), subclinical mastitis (SCM), and other costs components (i.e., preventive measures and product quality). A questionnaire was mailed to 374 dairy producers randomly selected from the (Canadian National Dairy Study 2015) to collect data on these costs components, and 145 dairy producers returned a completed questionnaire. For each herd, costs due to the different mastitis-related components were computed by applying the values reported by the dairy producer to the developed economic model. Then, for each herd, a proportion of the costs attributable to a specific component was computed by dividing absolute costs for this component by total herd mastitis-related costs. Median self-reported CM incidence was 19 cases/100 cow-year and mean self-reported bulk milk somatic cell count was 184,000 cells/mL. Most producers reported using post-milking teat disinfection (97%) and dry cow therapy (93%), and a substantial proportion of producers reported using pre-milking teat disinfection (79%) and wearing gloves during milking (77%). Mastitis costs were substantial (662 CAD per milking cow per year for a typical Canadian dairy farm), with a large portion of the costs (48%) being attributed to SCM, and 34 and 15% due to CM and implementation of preventive measures, respectively. For SCM, the two most important cost components were the subsequent milk yield reduction and culling (72 and 25% of SCM costs, respectively). For CM, first, second, and third most important cost components were culling (48% of CM costs), milk yield reduction following the CM events (34%), and discarded milk (11%), respectively. This study is the first since 1990 to investigate costs of mastitis in Canada. The model developed in the current study can be used to compute mastitis costs at the herd and national level in Canada.

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Infectious bovine abortions: observations from an organized dairy herd.

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