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| 2. |
- Aspán, Anna, et al.
(författare)
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Environmental sampling for evaluating verotoxogenic Escherichia coli O157:H7 status in dairy cattle herds
- 2013
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Ingår i: Journal of Veterinary Diagnostic Investigation. - : SAGE Publications. - 1040-6387 .- 1943-4936. ; 25, s. 189-198
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Tidskriftsartikel (refereegranskat)abstract
- Verotoxigenic Escherichia coli O157:H7 is a zoonotic bacterial pathogen capable of causing severe disease in human beings. Cattle are considered to be the main reservoir of the bacterium. The objective of the current study was to compare environmental sampling (consisting of dust, overshoe, and pooled pat samples) with pooled, individual fecal sampling for determining the cattle herd status under field conditions in naturally infected dairy herds. Thirty-one dairy cattle farms in Sweden, where verotoxigenic E. coli O157:H7 had been previously detected, were visited. On each farm, dust, overshoe, and pooled pat sampling were performed in each of 3 different age categories: calves, young stock, and adults. In addition, up to 140 individual fecal samples were collected and analyzed as pooled samples. In total, 3,763 individual fecal and 270 environmental samples were collected and analyzed for the presence of verotoxigenic E. coli O157:H7. Overshoe sampling, alone or in combination with dust and pooled pat sampling, correctly classified 20 of the 24 (0.83, 95% CI: 0.63-0.95) herds detected with at least 1 positive pool. On 1 farm, a dust sample was positive although all other samples were negative. In 6 of the 31 farms, the bacteria could not be detected in any of the individual fecal samples or in the environmental samples. The results establish that environmental sampling is a reliable method for identifying cattle herds with animals shedding verotoxigenic E. coli O157:H7.
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| 3. |
- Aspán, Anna, et al.
(författare)
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Longitudinal observational study over 38 months of verotoxigenic Escherichia coli O157: H7 status in 126 cattle herds
- 2015
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Ingår i: Preventive Veterinary Medicine. - : Elsevier BV. - 0167-5877 .- 1873-1716. ; 121, s. 343-352
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Tidskriftsartikel (refereegranskat)abstract
- Verotoxigenic Escherichia coli O157:H7 (VTEC O157:H7) is an important zoonotic pathogen capable of causing infections in humans, sometimes with severe symptoms such as hemorrhagic colitis and hemolytic uremic syndrome (HUS). It has been reported that a subgroup of VTEC O157:H7, referred to as clade 8, is overrepresented among HUS cases. Cattle are considered to be the main reservoir of VTEC O157:H7 and infected animals shed the bacteria in feces without showing clinical signs of disease. The aims of the present study were: (1) to better understand how the presence of VTEC O157:H7 in the farm environment changes over an extended period of time, (2) to investigate potential risk factors for the presence of the bacteria, and (3) describe the distribution of MLVA types and specifically the occurrence of the hypervirulent strains (clade 8 strains) of VTEC O157:H7. The farm environment of 126 cattle herds in Sweden were sampled from October 2009 to December 2012 (38 months) using pooled pat and overshoe sampling. Each herd was sampled, on average, on 17 occasions (range = 1-20; median = 19), at intervals of 64 days (range = 7-205; median = 58). Verotoxigenic E. coli O157:H7 were detected on one or more occasions in 53% of the herds (n= 67). In these herds, the percentage of positive sampling occasions ranged from 6% to 72% (mean = 19%; median = 17%). Multi-locus variable number tandem repeat analysis (MLVA) typing was performed on isolates from infected herds to identify hypervirulent strains (clade 8). Clustering of MLVA profiles yielded 35 clusters and hypervirulent strains were found in 18 herds; the same cluster was often identified on consecutive samplings and in nearby farms. Using generalized estimating equations, an association was found between the probability of detecting VTEC O157:H7 and status at the preceding sampling, season, herd size, infected neighboring farms and recent introduction of animals. This study showed that the bacteria VTEC O157:H7 were spontaneously cleared from the farm environment in most infected herds over time, and key factors were identified to prevent the spread of VTEC O157:H7 between cattle herds.
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- Bidokhti, Mehdi, et al.
(författare)
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Evolutionary dynamics of bovine coronaviruses: natural selection pattern of the spike gene implies adaptive evolution of the strains
- 2013
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Ingår i: Journal of General Virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 94, s. 2036-2049
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Tidskriftsartikel (refereegranskat)abstract
- Coronaviruses demonstrate great potential for interspecies transmission, including zoonotic outbreaks. Although bovine coronavirus (BCoV) strains are frequently circulating in cattle farms worldwide, causing both enteric and respiratory disease, little is known about their genomic evolution. We sequenced and analysed the full-length spike (S) protein gene of 33 BCoV strains from dairy and feedlot farms collected during outbreaks that occurred from 2002 to 2010 in Sweden and Denmark. Amino acid identities were >97% for the BCoV strains analysed in this work. These strains formed a clade together with Italian BCoV strains and were highly similar to human enteric coronavirus HECV-4408/US/94. A high similarity was observed between BCoV, canine respiratory coronavirus (CRCoV) and human coronavirus OC43 (HCoV-OC43). Molecular clock analysis of the S gene sequences estimated BCoV and CRCoV diverged from a common ancestor in 1951, while the time of divergence from a common ancestor of BCoV and HCoV-OC43 was estimated to be 1899. BCoV strains showed the lowest similarity to equine coronavirus, placing the date of divergence at the end of the eighteenth century. Two strongly positive selection sites were detected along the receptor-binding subunit of the S protein gene: spanning amino acid residues 109-131 and 495-527. By contrast, the fusion subunit was observed to be under negative selection. The selection pattern along the S glycoprotein implies adaptive evolution of BCoVs, suggesting a successful mechanism for BCoV to continuously circulate among cattle and other ruminants without disappearance.
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| 7. |
- Bidokhti, Mehdi, et al.
(författare)
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Tracing the transmission of bovine coronavirus infections in cattle herds based on S gene diversity
- 2012
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Ingår i: Veterinary Journal. - : Elsevier BV. - 1090-0233 .- 1532-2971. ; 193, s. 386-390
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Tidskriftsartikel (refereegranskat)abstract
- The analysed BCoV strains showed a high sequence identity, regardless of whether they were obtained from outbreaks of respiratory disease or diarrhoea or from calves or adult cattle. Circulation of an identical BCoV strain during a 4-month period was demonstrated in calves in one dairy herd. In a regional epizootic of winter dysentery in Northern Sweden, highly similar BCoV strains were detected. In the Southern and Central regions, several genotypes of BCoV circulated contemporaneously, indicating that in these regions, which had a higher density of cattle than the Northern regions, more extensive transmission of the virus was occurring. Identical BCoV sequences supported the epidemiological data that inter-herd contact through purchased calves was important. Swedish BCoV strains unexpectedly showed a high homology with recently detected Italian strains. This study shows that molecular analysis of the spike (S) glycoprotein gene of BCoV can be a useful tool to support or rule out suspected transmission routes. (C) 2012 Elsevier Ltd. All rights reserved.
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| 8. |
- Björkman, Camilla, et al.
(författare)
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Spatial patterns of Bovine Corona Virus and Bovine Respiratory Syncytial Virus in the Swedish beef cattle population
- 2010
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Ingår i: Acta Veterinaria Scandinavica. - : Springer Science and Business Media LLC. - 0044-605X .- 1751-0147. ; 52
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Tidskriftsartikel (refereegranskat)abstract
- Background: Both bovine coronavirus (BCV) and bovine respiratory syncytial virus (BRSV) infections are currently wide-spread in the Swedish dairy cattle population. Surveys of antibody levels in bulk tank milk have shown very high nationwide prevalences of both BCV and BRSV, with large variations between regions. In the Swedish beef cattle population however, no investigations have yet been performed regarding the prevalence and geographical distribution of BCV and BRSV. A cross-sectional serological survey for BCV and BRSV was carried out in Swedish beef cattle to explore any geographical patterns of these infections.Methods: Blood samples were collected from 2,763 animals located in 2,137 herds and analyzed for presence of antibodies to BCV and BRSV. Moran's I was calculated to assess spatial autocorrelation, and identification of geographical cluster was performed using spatial scan statistics.Results: Animals detected positive to BCV or BRSV were predominately located in the central-western and some southern parts of Sweden. Moran's I indicated global spatial autocorrelation. BCV and BRSV appeared to be spatially related: two areas in southern Sweden (Skaraborg and Skane) had a significantly higher prevalence of BCV (72.5 and 65.5% respectively); almost the same two areas were identified as being high-prevalence clusters for BRSV (69.2 and 66.8% respectively). An area in south-east Sweden (Kronoberg-Blekinge) had lower prevalences for both infections than expected (23.8 and 20.7% for BCV and BRSV respectively). Another area in middle-west Sweden (Varmland-Dalarna) had also a lower prevalence for BRSV (7.9%). Areas with beef herd density > 10 per 100 km(2) were found to be at significantly higher risk of being part of high-prevalence clusters.Conclusion: These results form a basis for further investigations of between-herds dynamics and risk factors for these infections in order to design effective control strategies.
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| 9. |
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| 10. |
- Hernandez, Carlos, et al.
(författare)
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Colostrum feeding routines - Passive immunity and welfare in dairy calves
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Calves are born with insufficient immunity to fight disease and rely on the passive transfer of immunity via ingestion of maternal immunoglobulins (IG) present in the colostrum. To ensure adequate transfer of immunity, dairy farmers utilize different methods to feed colostrum to their calves. Feeding methods include bottle or bucket feeding, oesophageal tube (OT) feeding, or suckling the dam. However, inherent differences between the feeding methods are known to result in different levels of transfer of passive immunity to the calves. These differences are related to the ability to control 1) the timing of first colostrum feeding, 2) the quality of the colostrum (mainly IgG content) and 3) the volume of colostrum consumed by the calves. With OT feeding it is easy to control the timing, quality and volume. With bottle or bucket feeding it is easy to control the timing and quality but more difficult to control the volume of colostrum consumed by the calves. In suckled calves, it is more difficult to control all, the timing, quality and volume of the colostrum consumed. Because OT feeding makes it possible to control the three main factors affecting transfer of passive immunity, farms that feed colostrum via OT have less failure of passive transfer (FPT) of immunity (often defined as serum IgG1 concentrations of <10 mg/ml at 24 h of age) than farms that bottle feed or allow the calves to suckle their dams. While the presence of the dam and suckling has been shown to increase absorption of immunoglobulins in dairy calves, several studies have found that dairy farms that allow the calves to obtain their first colostrum by suckling their mothers are at increased risk of FPT of immunity. Similarly, a study of Swedish dairy farms found an increased risk of severe diarrhoea in farms where calves were allowed to suckle compared to farms where the farmer fed their calves their first meal. The discrepancy between increased rate of absorption in suckled calves and increased FPT of immunity is likely due to the low volume of colostrum that the calves voluntarily consume during the first 24 h and a delayed ingestion of their first colostrum that outweighs any improvement in the rate of absorption. For these reasons, some dairy farms in North America feed first colostrum via OT as a way to ensure a good transfer of passive immunity in dairy calves, and now this practice is also being promoted in Sweden. While the OT feeding method seems ideal from the transfer of passive immunity point of view, it is not without risks and could compromise the welfare of the new born calf. Oesophageal tube feeding is an invasive procedure that requires trained personnel in order to prevent injury and prevent colostrum entering the respiratory tract, which could lead to pneumonia and in extreme cases death. In addition, force feeding strong and healthy calves with an OT, as opposed to intubating only weak, anorexic/dehydrated calves, could result in calves that resist and struggle excessively in response to the intubation procedure increasing the risk of injury, discomfort and distress. Furthermore, due to the large variation in colostrum quality (IgG content), it is often recommended to feed 3-4 L of colostrum or 10 % of the calf's body weight in the first meal to ensure adequate passive transfer of immunity. These large amounts of colostrum far exceed the abomasum capacity of the average new born calf (approx. 2 L for a 35 kg calf) and exceeds the amount of colostrum that calves voluntarily consume in the first 24 h after birth (2.4 ± 1.5 L). In addition, oesophageal tube feeding does not stimulate the oesophageal groove reflex, which directs the colostrum from the oesophagus to the abomasum where the necessary enzymes for digestion are found. Force feeding large volumes of colostrum in a short period of time to new born calves, such as during OT feeding, could lead to unnecessary discomfort and stress, but this has not been studied yet. While most studies have focused on the effects of OT feeding on transfer of passive immunity, health outcomes and mortality rates, there is no scientific evidence about the consequences of OT colostrum feeding for the behaviour and welfare of dairy calves. For this reason, a large multidisciplinary project is currently being carried out at the Department of Animal Nutrition and Management at SLU. ) aimed at addressing some of the issues concerning the routine use of OT feeding. The project aims to investigate the effects of OT vs suckling vs bottle colostrum feeding at birth, on the transfer of passive immunity, physiological, endocrine and behavioural response to the three feeding methods, growth, health, development of gut microbiota and welfare in dairy calves. In addition, the public's perception of oesophageal tube feeding as a routine management for colostrum feeding in dairy calves will be investigated. Further research on calves and colostrum management at our department include a study by PhD student Lisa Andree O´Hara comparing the use of refractometer (% Brix) and colostrometer as estimators of IgG content in milk (supervisor: Kjell Holtenius) and the PhD project of Bui Phan Thu Hang aimed at improving calf performance in small-scale dairy production in Southern Vietnam (supervisors: Kerstin Svennersten, Ewa Wredle, Johan Dicksved and Duong Nguyen Khang).
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