Biomedical subjects

K Frankena

Publications and source records attributed to K Frankena.

At least 19 recordsLinked to original sources

PubMed2006

Factors related to the incidence of clinical encephalomyocarditis virus (EMCV) infection on Belgian pig farms.

We set up a matched case-control study of potential risk factors for clinical encephalomyocarditis virus (EMCV) in 58 pig farms in West Flanders (Belgium). In total, 29 farms experienced a clinical outbreak of EMCV confirmed by EMC virus isolation. Mortality was seen only among suckling piglets (18 case farms), in piglets and other age-groups (4 case farms), or only among fattening pigs (7 case farms). Five farms had reproductive problems among the sows. Control farms were matched geographically on farm size and farm type and were selected on the absence of clinical signs. A questionnaire on potential risk factors for EMCV was developed to collect data at both case and control farms. The exploration of the data used clusters of factors associated with clinical EMCV infection: (a) rodents, (b) general farm set up and (c) general hygiene. The multivariable relationships between clinical appearance of EMCV and potential risk factors were tested with conditional logistic regression. The final model on all farms contained presence of mice (OR=8.3) as a risk factor for clinical EMCV infection while the flow of manure up through the slatted floor (OR=0.11) and movement of manure between manure pits in the pig stable (OR=0.14) were protective.

Animal Husbandry↗

PubMed2006

Transmission of bovine leukaemia virus within dairy herds by simulation modelling.

In Argentina, bovine leukaemia virus (BLV) infection is common in dairy herds. The country currently has a National Voluntary Control Programme but relatively few farms have enrolled. However, there is increased interest from authorities and farmers to implement regional compulsory programmes but there is scarce quantitative information of the transmission of BLV in cattle herds. This information is a prerequisite to develop effective BLV control strategies. Mathematical modelling offers ways of integrating population-level knowledge and epidemiological data to predict the outcomes of intervention scenarios. The purpose of the current paper is to gain understanding about the dynamics of the transmission of BLV in dairy herds from Argentina by simulation and to compare various BLV transmission models and select the one that is most appropriate. The hypothetical herd is conceptually described in terms of BLV status as a population of individuals that are protected by maternal antibodies (M), that are susceptible (S), that are in the latent period (E) or that are infectious (I). BLV is spread by horizontal and vertical transmission. We used an age-structured population model and within-herd transmission was simulated by Monte Carlo techniques. The next-generation approach has been used for the systematic computation of the basic reproduction ratio (R0). Parameter values for disease transmission were derived from previously published data; rates of entry, exit or transition between age groups were calculated based on our previous study, observational data, expert opinions and literature. With these parameter values the probability of a minor outbreak was estimated to be 10%, the probability of extinction was estimated as <0.001% and the expected time to extinction as more than 80 years. The probability of a minor outbreak and changes in prevalence were different when the index case was an adult cow compared to introduction by a heifer. Prediction of prevalences from MSI models fit the data satisfactorily. R0 was estimated as 9.5. The sensitivity analysis on R0 showed that all measures directed to reduce the transmission rate are potentially effective given operational control measures. An important prediction of these models is that, even in a relatively small, closed dairy herd, the time-scale for a BLV outbreak may be as long as several years and within-herd control of BLV requires intensive efforts.

Animals↗

PubMed2006

Evaluation of natural transmission of bovine leukaemia virus within dairy herds of Argentina.

The purpose of this study was to describe patterns of seroconversion to bovine leukaemia virus and to estimate the main parameters needed for future model building. A longitudinal study was carried out between February 1999 and November 2001 in seven commercial dairy farms in Argentina using 1535 lactating cows. Time-interval parameters were analysed using a parametric survival model with shared frailty, time until infection was analysed using a Bayesian interval-censoring survival model and the infection transmission parameter (beta) was estimated by a generalized linear model. The reproduction ratio (R0) was calculated. In total, 1000 cows tested positive and 494 tested negative. The predicted median age at infection was 4.6 years for seroconverted cows. For infected herds, the proportion of positive calves was as high as for infected cows and showed a large proportion of infected breeding heifers. Peaks in the overall average incidence per season-year were observed during autumn and spring. Results reveal that the period around parturition is a high-risk period. Moreover, heavily infected herds seem to have an increased proportion of young stock infected. The overall beta was estimated as 2.9/year (95% CI 1.9-3.7) and combined with a relatively long infectious period it resulted in a high reproductive ratio (R0=8.9). Therefore, a high effectiveness of control measures needs to be achieved to eradicate the disease.

Animal Husbandry↗

PubMed2006

Herd- and cow-level prevalence of digital dermatitis in the Netherlands and associated risk factors.

The objective of this cross-sectional study was to reevaluate the prevalence of digital dermatitis (DD) and associated risk factors in The Netherlands. Between May 2002 and December 2003, information about the presence or absence of DD lesions and other claw disorders on the hind claws of dairy cows in The Netherlands was collected by 20 hoof trimmers during trimming of all dairy cows in 383 herds. A questionnaire was used to acquire information regarding management and housing. Additional information, such as parity, breed, and stage of lactation of the cows, was provided by the Dutch Herd Book Organization. Digital dermatitis was present in 21.2% (SE = 0.3) of the study population (n = 22,454 cows). The herd prevalence varied from 0% (9.1% of the herds) to 83.0%. Most common was herd prevalence between 5 and 10%. The Holstein-Friesian breed was at higher risk for DD [odds ratio (OR) = 1.7] than was the Meuse Rhine IJssel breed (dual purpose breed). The risk for DD decreased with increasing parity. Cows at the peak of their lactation (30 to 60 d in milk) and in the third parity had higher odds for DD in comparison with cows that were later than 60 DIM. The presence of other claw disorders, such as interdigital dermatitis/heel horn erosion (IDHE), interdigital hyperplasia (HYP), and interdigital phlegmon, appeared to be predisposing for DD. Based on estimation of the population-attributable fraction, it was concluded that if IDHE, HYP, and interdigital phlegmon were not present among the study population, respectively, 32.2, 9.0, and 1.1% of the DD cases could have been prevented. The risk for DD slightly decreased when cows affected by IDHE had access to pasture. Because of the interrelation between infectious claw disorders, an effective intervention strategy against DD should focus on an integrated approach to the control of all infectious claw diseases. Cows trimmed >12 mo before the study (during regular trimming of the entire herd) were at lower risk for DD than were cows that were trimmed at shorter intervals. Animals that had >8 h of access to pasture were at higher risk for DD (OR = 1.6) compared with no access to pasture. Finally, cows in small-sized herds (<45 cows) affected with HYP were at lower risk (OR = 0.6) for DD than were cows affected with HYP in medium- and large-sized herds (60 to 85 cows per herd).

Animal Husbandry↗

PubMed2005

Risk factors for interdigital dermatitis and heel erosion in dairy cows kept in cubicle houses in The Netherlands.

Risk factors concerning both the pasture and housing seasons for interdigital dermatitis and heel-horn erosion (IDHE) were studied in dairy cows in a cross-sectional study in The Netherlands. The study population included 2,326 cows (41 herds) and 2,751 cows (46 herds) for the pasture and housing seasons, respectively. Of these animals, 545 (23%) showed serious lesions of IDHE (stages 2 and 3) at the end of the pasture season and 1,269 (46%) during housing. Logistic regression of the pasture study indicated that increased parity, solid concrete floor, restricted grazing time, and herd trimming at long intervals were associated with an increased odds of IDHE, while dry cows and lactating cows within 30 days after calving as well as cows on a slatted floor with manure scraper, and grassland with mixed type of soil were associated with lower odds. In the housing study, odds of IDHE increased with parity, administering low- or medium-energy roughage, and introduction of dry cows into the lactating herd at >2 weeks before calving. The presence of long cubicles, knee-bumpers installed in cubicles as well as rearing calves and heifers within the dairy cows' accommodation decreased the odds of IDHE.

Animals↗

PubMed2005

Risk factors for digital dermatitis in dairy cows kept in cubicle houses in The Netherlands.

The presence of digital dermatitis (DD) in dairy cows has increased considerably over the last 10 years in The Netherlands, resulting in a current prevalence of approximately 30% in cows kept in cubicle houses. Our objective was to evaluate a diversified sample of cow- and herd-related risk factors for DD in dairy cows housed in cubicle houses with different flooring systems. Associations were analysed in random-effects logistic-regression models using 2,134 cows (37 herds) and 2,892 cows (47 herds) in the pasture and housing studies, respectively. At cow-level, the odds of having DD were increased in the case of lower parity and lactation. Important risk factors at herd-level were: restricted grazing time, fast rise in concentrate amount after calving, feeding by-products, herd trimming only at long intervals, and introduction of dry cows into the lactating herd before calving. The odds for DD were lower if cows were housed on a slatted floor with manure scraper and provided long and wide cubicles, and if calves were reared in the dairy cows' accommodation.

Animals↗

PubMed2005

Escherichia coli O157 prevalence in Dutch poultry, pig finishing and veal herds and risk factors in Dutch veal herds.

In the period October 1996 through December 2000, a total of 7163 pooled faecal samples of laying hen and broiler flocks, finishing-pig herds and veal herds were examined for the presence of Salmonella spp., Campylobacter spp. and verocytotoxin-producing Escherichia coli O157 as part of a national monitoring programme in The Netherlands. Isolates were tested for eae and VT genes. Risk factors for Dutch veal herds were quantified. For all herd/flock types, faecal samples were cultured for E. coli O157. Of broiler flocks, laying flocks and finishing pig herds, respectively, 1.7%, 0.5% and 0.4% were E. coli O157 positive. In total, 42 of the 454 veal herds (9.3%) showed at least one positive pooled sample. E. coli O157-positive herds were compared (with logistic regression) to negative herds, regarding variables obtained from the questionnaire taken from the farm manager. To account for season, a sine function was included in the logistic regression as offset variable. In the final model, 'pink-veal production' (compared to white-veal production), 'group housing of the sampled herd' (compared to individual housing), 'more than one stable present' (compared to one stable present), 'hygienic measures regarding visitors' (compared to no hygienic measures), 'interval arrival-sampling of a herd of >20 weeks' (compared to < or =10 weeks), and 'presence of other farms within 1 km' (compared to no presence of farms <1 km) showed associations (P<0.05) with the presence of E. coli O157. These results need careful interpretation; they should be considered as indications for further (experimental or cohort-based) research rather then causal associations.

Animals↗

PubMed2005

Effect of neosporosis on productive and reproductive performance of dairy cattle in Costa Rica.

A cross-sectional study was conducted to assess the effect of neosporosis on productive and reproductive parameters in dairy cows. Cows (n=2743) from 94 farms located in the most important dairy areas in Costa Rica were used in the study. The size of the herds ranged from 32 to 379 females (mean=110, median=125). An indirect ELISA was used to determine the serostatus of the cows towards Neospora caninum. The effect of neosporosis on milk production was analysed by a mixed linear model. In addition, the effects on calving interval (days) and calving to conception interval (days) were analysed by survival analysis. The risk of abortion in relation to N. caninum serostatus was assessed by logistic regression, with herd as a random effect. Overall, 1185 of 2743 cows (43.3%) were seropositive for Neospora. Eighty-nine of 94 (94.7%) farms were classified as Neospora-seropositive. It was estimated that cows seronegative to Neospora produced an additional 84.7L of milk (P=0.6). Serostatus did not have a significant effect on the length of the calving interval in the Cox proportional hazard survival analysis (Hazard ratio=1.2, 95% CI: 0.9, 1.4). The logistic regression model had a weak positive association between serostatus and abortion (OR 1.7, 95% CI: 0.8, 3.9), but did not show a strong association between serostatus and the number of services per conception (OR=0.95, 95% CI: 0.7, 1.3). In conclusion, there were no significant effects of Neospora serostatus on production and reproductive performance in this study.

Animals↗

PubMed2005

Survival analysis on aggregate data to assess time to sero-conversion after experimental infection with Bovine Leukemia virus.

Bovine Leukemia virus (BLV) is a ubiquitous retrovirus that affects mainly cattle. Knowledge of the precise moment of infection is fundamental for identification and evaluation of factors related to BLV transmission. Systematic reviews and meta-analyses provide good evidence on the effects of medical interventions. The objectives were to estimate time to sero-conversion after experimental infection using data from retrieved literature and to detect factors that may influence the length of that interval using survival analysis on pooled data. An analysis using aggregate data from 36 studies totalling 438 observations was performed. From this, four sets were created and analysed by interval-censored accelerated failure time models (AFT) with different distributions (exponential, Weibull, log-logistic, lognormal and generalized gamma), and some variants of the Cox model (Andersen-Gill, smoothing splines) with and without a frailty effect. The AFT gamma model fit best and the estimated median time to sero-conversion in the null model was 57 days (95% confidence interval (CI): 49; 75) using all data and 47 days (95% CI: 39; 55) when only studies using experimental inoculation were considered. Some factors were consistently associated with time to sero-conversion. These included exposure by animal-to-animal contact (resulting in a seven-fold increase in time to sero-conversion compared to direct inoculation), diagnostic method to detect sero-conversion (time to sero-conversion was 1.4 times shorter when AGID was used compared to ELISA), and transmission by insect bites (biological media) delayed sero-conversion 2.3 times compared transmission via needles or other inanimate media. After fitting a frailty Cox model, results showed that sero-conversion in susceptible animals after infection using donors, in which presence of virus before the experiment started was confirmed, increased the hazard of sero-conversion two times in comparison with donors in which virus presence was not confirmed before start of the experiment. Inoculation with blood decreased the hazard 2.5 times in comparison with lymphocyte suspensions. Heterogeneity due to different research groups was also present. Finally, a Cox model with smoothing splines contained three variables: research group, route of inoculation and a non-linear spline for infective dose. In conclusion, it can be stated some factors that influence the time to sero-conversion were identified and quantified and that a moderate influence of research centre existed. These results may contribute to the estimation of the most probable times of infection in field conditions and in a better evaluation of control measures.

Animals↗

PubMed2005

A longitudinal study of Escherichia coli O157 in cattle of a Dutch dairy farm and in the farm environment.

From July 1999 till November 2000, a longitudinal study was conducted on a dairy farm in The Netherlands to study within herd prevalence and types of verocytotoxin producing Escherichia coli (VTEC) of serogroup O157 over time, and determine environmental reservoirs and possible transmission routes. Faeces, blood, milk and environmental samples were collected 14 times with intervals varying from 4 to 10 weeks during the study period. Faecal samples were selectively cultured for Escherichia coli O157. Isolates were tested by PCR for the most common virulence genes, VTI, VTII and eae, and typed by pulsed field gel electrophoresis. In total, 71 isolates were obtained, of which 49 from dairy cows, 8 from young stock, 5 from other animals and 9 from the environment. Positive samples were all detected in summer and early fall. VT- and eae-genes were found in all tested isolates, except in one. DNA typing showed that three clusters of O157 isolates could be identified. One of these clusters contained samples of two shedding seasons, indicating persistence on the farm during winter and spring. Repeated measures analysis of variance showed that cows with O157 VTEC infection had higher daily milk production in the period preceding sampling (p = 0.0055). There was no significant association between the results of the LPS-ELISA on serum samples from dairy cows and their O157 status.

Adhesins, Bacterial↗

PubMed2005

Influence of negative energy balance on the reproductive performance after treatment of cystic ovarian disease with gonadotrophin-releasing hormone in dairy cows.

The aim of this study was to investigate whether a significant relation exists between the presence of a negative energy balance (NEB) in cows early in lactation and the reproductive performance after treatment with gonadotrophin-releasing hormone of cows with clinical cystic ovarian disease. Reproductive performance after treatment was assessed from the interval between treatment and first insemination (ITFI) and the interval between treatment and conception (ITC). Based on the outcome of the daily change of milk fat yield (Deltafatg) between the first and second milk recordings post-partum, cows were considered to have passed the NEB nadir (positive Deltafatg) or not (negative Deltafatg). Lactations (n = 430) were divided into four groups according to the interval between calving and first milk recording (ICMR): (i) 0-9 days; (ii) 10-19 days; (iii) 20-29 days; (iv) 30-49 days. The relation between a NEB-proxy parameter (Deltafatg) and reproductive performance was determined. A significant interaction existed for groups 1 and 3 (ICMR on 0-9 and 20-29 days post-partum respectively) with an increased and a decreased probability of being inseminated the first day after treatment (ITFI) respectively. However, no significant interaction was found between Deltafatg and the groups with regard to ITC.

Animals↗

PubMed2005

Development of claw traits and claw lesions in dairy cows kept on different floor systems.

Several claw shape measurements, horn hardness, and horn growth and wear were recorded monthly at 12 dairy farms to investigate the effect of floor type and changes in these traits over time. Herds were either housed on a slatted floor (SL), solid concrete floor (SC), grooved floor (GR), or on a straw yard (SY). Twenty cows per farm were selected and stratified by parity. Information on claw traits was recorded on right lateral hind claws between October 2002 and May 2003. In addition, lesion development of interdigital dermatitis and heel erosion (IDHE) and digital dermatitis (DD) was studied in both rear feet. No differences in claw traits were detected among groups on different floor types, with the exception of claw angle. Claw angles were smallest in cows on SY. Claws of cows on SC were steeper than those on SL and GR. The study provided no evidence that floor-related differences in claw lesions were related to differences in horn growth, wear, and resulting claw shape. Lesions of IDHE developed gradually over time and did not differ among flooring types. Cows in SY had the smallest lesion scores for DD, whereas cows on SL had significantly less DD than cows on SC and GR. Incidence of DD fluctuated over time. Development of different stages of DD was monitored in-depth. Both early and healed stages were rather changeable and often turned into other disease stages. Classical ulcerative lesions (stage M2) persisted for a long time, with 20% of the initially unaffected claws having active lesions of DD within 5 mo. The M2 lesions generally did not cure effectively after claw trimming, and frequent use of footbaths resulted in a poor prognosis for recovery.

Animals↗

PubMed2004

Effect of a killed whole Neospora caninum tachyzoite vaccine on the crude abortion rate of Costa Rican dairy cows under field conditions.

A standard field trial was carried out to assess the effect of a commercial Neospora-vaccine based on whole killed tachyzoites (Bovilis-Neoguard, Intervet) on the abortion rate. Eight hundred and seventy-six cows, over 2.5 months pregnant, belonging to 25 Costa Rican dairy herds, were used in the analysis. For each cow vaccinated, a cow of the same herd, breed and age category, was selected as control. The period of administration of treatments extended from June to November of 2000. The treatments were administered in two, 5-ml doses 1 month apart, the first dose given between day 75 and 90 of gestation. The incidence of abortion among all treated cows was of 16.0% (140/876). The treatment specific incidence was 11.2% (49/438) and 20.8% (91/438) for the vaccinated and the placebo group, respectively. The prevented fraction by vaccination amounted to 0.46 (95% CI: 0.26, 0.61), and the cumulative incidence ratio for the vaccinated group was 0.54. The Cox hazard ratio was 0.51(95% CI: 0.37, 0.72), meaning that the force of abortion is reduced twice in the vaccinated group. The results of this study, the first one following this type of design, shows that the killed whole Neospora caninum tachyzoite preparation had a reasonable effect on the abortion rate in Costa Rican dairy cattle.

Abortion, Veterinary↗

PubMed2004

Prevalence estimation and risk factors for Escherichia coli O157 on Dutch dairy farms.

To estimate the prevalence of Escherichia coli O157 on Dutch dairy herds, faecal samples were collected once from 678 randomly selected dairy farms in the period October 1996-December 2000. Samples were cultured for E. coli O157. Thirty-eight isolates were tested for virulence genes (eae, VT1 and VT2). A questionnaire about farm characteristics was taken from the farm manager, resulting in variables that could be analysed to identify and quantify factors associated with presence of E. coli O157. In total, 49 of the 678 herds (7.2%) showed at least one positive pooled sample. E. coli O157 was not isolated from herds sampled in December-April in consecutive years (except for one isolate found in March, 2000). VT- and eae-genes were found in 37 and 38 isolates, respectively. Logistic regression was performed on variables obtained from the questionnaire, comparing E. coli O157-positive herds to negative herds. To account for season, a sine function was included in the logistic regression as an offset variable. In the final model, the presence of at least one pig at the farm (OR = 3.4), purchase of animals within the last 2 years before sampling (OR = 1.9), supply of maize (OR = 0.29) to the cows, and sampling a herd in the year 1999 or 2000 (compared to sampling in 1998; OR = 2.1 and 2.9, respectively) had associations with the presence of E. coli O157.

Animals↗

PubMed2004

Simulated hazards of loosing infection-free status in a Dutch BHV1 model.

A compulsory eradication programme for bovine herpesvirus 1 (BHV1) was implemented in the Netherlands in 1998. At the start of the programme, about 25% of the dairy herds were certified BHV1-free. Simulation models have played an important role in the decision-making process associated with BHV1 eradication. Our objective in this study was to improve understanding of model behaviour (as part of internal validation) regarding loss by herds of the BHV1-free certificate. Using a Cox proportional hazards model, the association between farm characteristics and the risk of certificate loss during simulation was quantified. The overall fraction of herds experiencing certificate loss amongst initially certified during simulation was 3.0% in 6.5 years. Factors that increased risk for earlier certificate loss in the final multivariable Cox model were higher 'yearly number of cattle purchased', 'farm density within a 1 km radius' and 'cattle density within a 1 km radius'. Qualitative behaviour of risk factors we found agreed with observations in field studies.

Animal Husbandry↗

PubMed2003

The effect of the dam-calf relationship on serostatus to Neospora caninum on 20 Costa Rican dairy farms.

An epidemiological study was conducted on 20 dairy herds previously diagnosed as seropositive for Neospora caninum. The number of females per farm varies from 41 to 296. All females present on the farms were bled once in the period of July and August 2000. A total of 3002 females were bled. An indirect ELISA was used to determine the serostatus of the animals. The analysis of the data was performed in four steps: (1) descriptive statistics about the serological status and general characteristics of the cattle; (2) calculation of vertical and horizontal transmission; (3) an univariate analysis and, (4) a multivariate logistic regression analysis with herd as random effect. The within-herd seroprevalence varied between 25.0% (34/136) and 70.5% (203/288). Seven hundred and forty-seven dam-daughter pairs were available, involving daughters of any age. Daughters in the specific age-class of 2- and 3-years old had a higher seroprevalence (P<0.01) compared with younger and older age-classes. The risk of being seropositive when being born to a mother that tested seropositive (prevalence ratio (PR)) was 2.8-fold increased which coincides with a 5.3-fold increased odds. The probability of horizontal infection amounts to 0.22. The probability of a seropositive offspring due to vertical transmission was 0.64 (attributable fraction among exposed (AFexp)). The multivariate logistic regression showed a significant 6.0-fold increased odds for being seropositive when born from a seropositive mother. Also the within-herd seroprevalence level was significantly associated with the serostatus of the daughters. In the specific conditions of the dairy herds involved in this study, the serostatus of the cows should be not used as a predictor of the serostatus of daughters due to the increased probability of horizontal transmission.

Age Distribution↗

PubMed2003

Prevalence of claw disorders in Dutch dairy cows exposed to several floor systems.

Claw health was examined in an observational study on Dutch dairy farms with either a slatted floor (SL), slatted floor with manure scraper (SL-SCR), solid concrete floor (SCF), a straw yard (SY), or a zero-grazing feeding system (ZG). Hooves of cows' hind legs were examined for the presence and severity of claw disorders during hoof trimming events at the end of the pasture (P-study) and housing period (H-study). The number of cows in each study was 3078 (49 herds) and 3190 (47 herds), respectively. Due to a different hoof trimming strategy, data collected during both observation periods in SY herds (638 cows; 16 herds) were combined. Cows in straw yards (SY) had by far the lowest numbers of claw disorders. Over 80% of cows exposed to concrete flooring had at least one claw disorder at the time of observation, whereas on SY surfaces, this percentage was between 55 and 60. Cows on SL-SCR were less frequently affected by interdigital dermatitis/heel erosion (IDHE) and digital dermatitis (DD) than cows on SL (reference floor system). Little difference in claw health was found between SF and SL. The ZG cows were at higher risk (OR > 2) for most claw disorders in the P-study, whereas in the H-study, ZG cows showed less IDHE, sole hemorrhage, and sole ulcer. All herds on concrete flooring (SL, SL-SCR, SCF, ZG) were infected by DD, resulting in an average cow level prevalence of 30%. This indicates that the level of DD infection has increased considerably over the last 10 yr in The Netherlands.

Animals↗

PubMed2002

Risk factors for clinical Salmonella enterica subsp. enterica serovar Typhimurium infection on Dutch dairy farms.

Risk factors for outbreaks in 1999 of clinical Salmonella enterica subsp. enterica serovar Typhimurium infection on dairy farms were studied in a matched case-control study with 47 case farms and 47 control farms. All 47 case farms experienced a clinical outbreak of salmonellosis which was confirmed with a positive bacteriologic culture for serovar Typhimurium in one or more samples. Serovar Typhimurium phage type 401 and 506 (definitive type 104, DT104) were the most frequently isolated phage types (13 isolates). On most farms (66%), clinical signs were seen only among adult cows. The most frequently reported clinical signs were diarrhoea (in 92% of the farms) and depression (in 79% of the farms). Control farms were matched on region and had no history of salmonellosis. A questionnaire was used to collect data on case and control farms. The relationship between serovar Typhimurium status of the farm and possible risk factors was tested using conditional logistic regression. Significant factors in the final model were presence of cats on the farm (OR=0.06), purchase of manure (OR=21.5), feeding colostrum only from own dam (OR=0.08), a non-seasonal calving pattern (OR=25), unrestricted grazing of lactating cows (OR=0.07), and a high mean mowing percentage of pasture (OR=1.02).

Animals↗