Association between milk yield and milk anti-Fasciola hepatica antibody levels, and the utility of bulk tank milk samples for assessing within-herd prevalence on organic dairy farms.

Fasciola hepatica is an important disease of livestock that is responsible for substantial economic losses worldwide. Estimates of the impact of infection on milk yield vary, likely reflecting different geographical locations, farm-level management, and diagnostic methods. Measuring anti-Fasciola antibodies on bulk tank milk (BTM) by ELISA provides a convenient herd-level diagnosis, but the utility of this test remains unclear. Therefore, we evaluated the utility of BTM ELISA test results in Danish organic dairy farms, including estimating the association between 305 day energy corrected milk yield (305d ECM) and F. hepatica infection both at individual and herd level. BTM samples from 218 organic farms were analysed using IDEXX ELISA and subsequently the farmers were interviewed during spring 2016 with the aim of characterising their management practices. The corresponding farm-level production data covering the period 2014-2017 were collected from the Danish national cattle registry. In the following year, 284 individual milk samples (4-7 per herd) along with BTM samples were collected from a subset of the same herds (n = 55). Linear mixed models were used to estimate the association between milk production and ELISA value at both individual and farm levels, and a generalised additive model was used to assess the relationship between within-herd prevalence and BTM ELISA. A dichotomised BTM result with positive outcome was associated with a reduction of 580.5 kg in average 305d ECM, and a positive outcome on individual-level ELISA was associated with a 919.5 kg reduction in milk yield for cows in their third or later lactations. A strong relationship between quantitative BTM ELISA sample to positive percentage (S/P%) and apparent within-herd prevalence based on dichotomised individual-level milk ELISA was also observed, although this relationship was non-linear in nature. We conclude that a useful indication of the within-herd prevalence of infection can be obtained from BTM ELISA following categorisation as negative, low, medium or high according to S/P% cut-offs of approximately 30, 80, and 150. This approach represents a cheap and useful diagnostic tool for monitoring the long-term success of control strategies for F. hepatica infections on a dairy farm.

The distribution of clones of Streptococcus agalactiae (group B streptococci) among herdspersons and dairy cows demonstrates lack of host specificity for some lineages.

Streptococcus agalactiae (Group B streptococcus, GBS) is a commensal of the human intestinal tract and vagina and is also an opportunistic pathogen causing serious, potentially lethal, infections preferentially in newborns and in the elderly. In cattle, it is considered an udder-specific pathogen and a common cause of mastitis. Here we investigated the host specificity of GBS by examining their colonization at various anatomical sites in both cattle and humans, as well as the possible cross-species transmission in closed barn environments. We collected more than 800 swab samples from dairy cows and herdspersons at eight dairy farms in Denmark. GBS was isolated from 12% of the samples. The GBS strains (N = 105) were characterized by biochemical test, serology, and Pulsed-Field Gel Electrophoresis (PFGE). Based on the PFGE patterns, 25 strains were selected for whole genome sequencing followed by phylogenetic analyses. The genomes were compared to each other and to a collection of publicly available GBS genomes. The study revealed that GBS clones were shared by cows and herdspersons. In phylogenetic analyses, these shared clones clustered with GBS strains from persons with no relation to farming. Horizontal cross-species transmission of the contagion in both directions was found to be highly likely within the same environment; thus, some cases of bovine mastitis are probably antrophonotic.

Farm-level risk factors for Fasciola hepatica infection in Danish dairy cattle as evaluated by two diagnostic methods.

BACKGROUND: The prevalence of bovine fasciolosis in Denmark is increasing but appropriate guidelines for control are currently lacking. In order to help develop a control strategy for liver fluke, a risk factor study of farm management factors was conducted and the utility of bulk tank milk (BTM ELISA) as a tool for diagnosis in Danish dairy cattle farms was assessed. METHODS: This case-control study aimed to identify farm-level risk factors for fasciolosis in Danish dairy farms (> 50 animals slaughtered in 2013) using two diagnostic methods: recordings of liver condemnation at slaughter, and farm-level Fasciola hepatica antibody levels in BTM. A case farm was defined as having a minimum of 3 incidents of liver condemnation due to liver fluke at slaughter (in any age group) during 2013, and control farms were located within 10 km of at least one case farm and had no history of liver condemnation due to liver fluke during 2011-2013. The selected farmers were interviewed over telephone about grazing and control practices, and BTM from these farms was collected and analysed by ELISA in 2014. The final complete dataset consisting of 131 case and 63 control farms was analysed using logistic regression. RESULTS: Heifers grazing on wet pastures, dry cows grazing on wet pastures, herd size, breed and concurrent beef cattle production were identified as risk factors associated with being classified as a case farm. With the categorised BTM ELISA result as the response variable, heifers grazing on wet pastures, dry cows grazing on wet pastures, and purchase of cows were identified as risk factors. Within the case and control groups, 74.8 and 12.7% of farms were positive for fasciolosis on BTM ELISA, respectively. The differences are likely to be related to the detection limit of the farm-level prevalence by the BTM ELISA test, time span between slaughter data and BTM, and the relatively low sensitivity of liver inspection at slaughter. CONCLUSIONS: Control of bovine fasciolosis in Denmark should target heifers and dry cows through grazing management and appropriate anthelmintic treatment, and BTM ELISA can be a useful diagnostic tool for fasciolosis in Danish dairy farms.

Towards a risk-based surveillance for Trichinella spp. in Danish pig production.

Increasing demands for cost-effectiveness in surveillance for human health hazards from animal origins can be met by introducing risk-based principles. This e.g. implies targeting subpopulations with higher risk of infection compared to the whole population. Furthermore, historical data from surveillance can be collated and used to assess future risk of infection. To demonstrate the effectiveness of combining these two approaches, we used a model called "Discounting historical evidence". It depends mainly on the annual risk of introduction (PIntro) and the surveillance system sensitivity (SSe) (ability to detect infection if present). The model implies simulations that reiterate for a number of years. For each year the output is updated with the confidence on absence in infection. Trichinella spiralis infection in pigs is used as an example. In Denmark, more than 20 million pigs are tested annually. Despite more than 70 years of testing no pigs have been found positive for Trichinella. Hence, PIntro is low. SSe can be estimated from the maximum number of infected carcasses expected under the specified design prevalence, and the sensitivity of the test applied. According to our assessment, the current prevalence of Trichinella in Danish pigs is less than one case per million, which we interpret as negligible risk. Based on this, a risk-based surveillance programme for Trichinella is designed that targets all out-door reared pigs as well as all sows and boars (current total 610,000 slaughtered annually). These subpopulations are judged to have higher risk of getting Trichinella. Again, SSe and PIntro are estimated and the model results show that risk-based surveillance can be applied without jeopardizing human health. Finally, we incorporate wildlife surveys and test quality assurance in the programme. The results of the simulation model were included in an application to the European Commission concerning Denmark's status as a region with negligible risk of Trichinella. In July 2007, the European Commission granted status as "negligible risk" to Danish pigs and pork.

Ascariasis is a zoonosis in denmark.

A preliminary epidemiological survey indicated an association between Ascaris infections in Danish patients and contact with pigs or pig manure. In the present study, we compared Ascaris worms collected from humans and Ascaris worms collected from pigs by amplified fragment length polymorphism (AFLP) analysis, a technique for whole-genome fingerprinting, and by PCR-linked restricted fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer region of nuclear rDNA. The AFLP data were analyzed by distance- and model-based clustering methods. These results assigned Ascaris worms from Danish patients to a cluster different from that for worms from humans in other geographic areas. In contrast, worms from humans and pigs in Denmark were assigned to the same cluster. These results were supported by the PCR-RFLP results. Thus, all of the examined Danish patients had acquired Ascaris infections from domestic pigs; ascariasis may therefore be considered a zoonotic disease in Denmark.

Longitudinal study of Salmonella enterica aerotype Typhimurium infection in three Danish farrow-to-finish swine herds.

A longitudinal study of the infection dynamics of Salmonella enterica was carried out with three Danish farrow-to-finish swine herds. To account for variations in Salmonella shedding over time, litters from each herd were divided into two cohorts. Each cohort consisted of 30 pigs, for a total of 180 pigs. Pigs were individually monitored by monthly bacteriologic and serologic examinations from weaning to slaughter. At weaning, individual sows were examined bacteriologically and serologically. At slaughter, cecal contents, ileocecal lymph nodes, and carcass swab samples were obtained from 131 pigs. A total of 88 pigs were found to be shedding Salmonella on one or more occasions. Only the Salmonella serotype Typhimurium was detected during the study period. At weaning, no sows or piglets were found to be shedding, but a serological reaction was detected in 11 sows. The prevalence in culture peaked in the nursery and subsequently declined to undetectable levels before slaughter. The seroprevalence peaked approximately 60 days after the peak prevalence in culture. Salmonella was detected in individual fecal samples at least once in 53% of the pigs, and 62% of the pigs were seropositive more than once. Only 3.7% of all pigs were found to be culture positive on more than one occasion. Piglets from seroreacting sows had a significantly (P = 0.0339) lower probability of shedding in the nursery. Under the assumption that shedding lasted at least 1 or 2 weeks, the average shedding time was estimated to have been 18 or 26 days. An association between serology, on-farm bacteriology, and Salmonella prevalence in culture at slaughter was shown. Marked differences in prevalence in sera and prevalence in culture between cohorts and within herds were observed. These differences emphasize the need for caution when using point estimates in on-farm interventions and surveillance in subclinically infected swine herds.