Biomedical subjects

C Staubach

Publications and source records attributed to C Staubach.

At least 19 recordsLinked to original sources

PubMed2006

A simple statistical approach for assessing inter-laboratory comparison tests for classical swine fever diagnosis.

The aim of this study was to compare on an objective basis the results obtained during five classical swine fever (CSF) ring tests conducted in Germany between 1999 and 2003. A novel and simple statistical approach used in behavioural sciences was used. For each ring test, the regional laboratories received a panel of five lyophilized pig sera. The panel contained CSF virus positive and negative samples. The final task of the laboratory was to ascertain if a serum sample was positive for CSF or not. Some sera were very easy to diagnose as CSF positive while some sera had border line values and proved to be challenging. Depending on the degree of difficulty the sera were divided into five categories. The evaluation of the ring test results was performed using a scoring system based on a score from -3 to +3 which takes into consideration the degree of difficulty to produce a correct diagnosis. To compare the results between different laboratories and/or between different ring tests more easily the total score of one laboratory was expressed in percentage. The final analysis of the data showed that the CSF diagnostic quality improved continuously.

Animals↗

PubMed2006

Animal disease outbreak control: the use of crisis management tools.

In this era of globalisation the effective control of animal disease outbreaks requires powerful crisis management tools. In the 1990s software packages for different sectors of the government and agricultural industry began to be developed. In 2004, as a special application for tracking the movement of animals and animal products, the European Union developed the Trade Control and Expert System (TRACES) on the basis of its predecessor, the ANImal MOvement (ANIMO) project. The nationwide use of the ANIMO system by the veterinary authorities in Germany marked the beginning of the development in 1993 of a computerised national animal disease reporting system--the TierSeuchenNachrichten (TSN)--using the ANIMO hardware and software components. In addition to TRACES and TSN the third pillar for the management of animal disease outbreaks and crises in Germany is the national cattle and swine database--called Herkunftssicherungs- und Informationssystem für Tiere. A high degree of standardisation is necessary when integrating the different solutions at all levels of government and with the private sector. In this paper, the authors describe the use of these tools on the basis of their experience and in relation to what we can do now and what we should opt for in the future.

Animal Diseases↗

PubMed2005

Long-term studies on maternal immunity for Aujeszky's disease and classical swine fever in wild boar piglets.

The aim of the studies was to fathom the duration and the role of maternal immunity for Aujeszky's disease (AD) and classical swine fever (CSF) in wild boar offspring. In one experiment, two wild boar sows were infected with a low pathogenic pseudorabies virus (PRV) in 1999. A total of 51 offspring was born between 1999 and 2002 and was monitored for PRV maternal antibodies. In a second experiment, the maternal immunity for CSF was analysed. Therefore, a sow was orally vaccinated against CSF using vaccine baits containing the live-attenuated C-strain vaccine. The vaccination took place in January 1999. The sow gave birth to four piglets in 2001 and to two piglets in 2002. With respect to maternal immunity for AD, some piglets reacted positive in the ELISA up to 27-week post-partum while in the neutralization test antibodies were detected up to 15-week post-partum. The calculated half-life of neutralizing antibodies was 21 days. Regarding CSF, the neutralization titres of maternal antibodies dropped continuously reaching values of < or =10 ND50 20-week post-partum. After the 12th week post-partum, most of the sera reacted negative in the ELISA. However, after the third month, low levels of neutralization titres were still detectable. The results are discussed with respect to the epidemiology and control of both diseases in wild boar populations.

Animals↗

PubMed2004

Adaptation of a commercial ELISA for the detection of antibodies against Neospora caninum in bovine milk.

The aim of the present study was to determine whether a commercially available ELISA could be used to examine bovine milk for antibodies against Neospora caninum. In an initial titration experiment, a milk dilution of 1:2 was found optimal to obtain milk results that were linearly correlated to those obtained with corresponding sera. This dilution was then used to examine 791 milk samples from N. caninum infected herds in the commercial ELISA. Milk results of individual animals were compared with those obtained by the same ELISA for the corresponding serum samples. The linear correlation between milk and serum antibody results of individual animals was characterized by R2 = 0.702. Multiple linear regression indicated that the later the stage of lactation at which an animal was sampled, the higher the milk ELISA result was as compared to the serum ELISA result. The examination of the two-graph receiver operating characteristics revealed an optimal cut-off of 0.261 to obtain similar results in the examination of milk and serum. With this cut-off, the test had a sensitivity and specificity relative to the serum results of 90%. The milk-based commercial ELISA classified more aborting dams as positive than the serum-based ELISA with this cut-off. The milk ELISA may be a valuable tool to assess the herd status with regard to abortion caused by N. caninum.

Abortion, Veterinary↗

PubMed2004

Processes leading to a spatial aggregation of Echinococcus multilocularis in its natural intermediate host Microtus arvalis.

The small fox tapeworm (Echinococcus multilocularis) shows a heterogeneous spatial distribution in the intermediate host (Microtus arvalis). To identify the ecological processes responsible for this heterogeneity, we developed a spatially explicit simulation model. The model combines individual-based (foxes, Vulpes vulpes) and grid-based (voles) techniques to simulate the infections in both intermediate and definite host. If host populations are homogeneously mixed, the model reproduces field data for parasite prevalence only for a limited number of parameter combinations. As ecological parameters inevitably vary to a certain degree, we discarded the homogeneous mixing model as insufficient to gain insight into the ecology of the fox tapeworm cycle. We analysed five different model scenarios, each focussing on an ecological process that might be responsible for the heterogeneous spatial distribution of E. mulitlocularis in the intermediate host. Field studies revealed that the prevalence ratio between intermediate and definite host remains stable over a wide range of ecological conditions. Thus, by varying the parameters in simulation experiments, we used the robustness of the agreement between field data and model output as quality criterion for the five scenarios. Only one of the five scenarios was found to reproduce the prevalence ratio over a sufficient range of parameter combinations. In the accentuated scenario most tapeworm eggs die due to bad environmental conditions before they cause infections in the intermediate host. This scenario is supported by the known sensitivity of tapeworm eggs to high temperatures and dry conditions. The identified process is likely to lead to a heterogeneous availability of infective eggs and thus to a clumped distribution of infected intermediate hosts. In conclusion, areas with humid conditions and low temperatures must be pointed out as high risk areas for human exposure to E. multilocularis eggs as well.

Animals↗

PubMed2004

Potential risk factors for bovine Neospora caninum infection in Germany are not under the control of the farmers.

In the German state of Rhineland-Palatinate, herds were identified that were likely to have a Neospora caninum sero-prevalence > or = 10% by using a bulk milk ELISA. Individual herd data were obtained by a questionnaire. Univariate logistic regression showed that bulk milk positive farms had a significantly higher chance to report an increased abortion rate than negative farms (P(Wald)<0.1). The chance to have a bulk milk positive herd increased with the minimum number of years a farm had reported an increased abortion rate (P(Wald)<0.1). Questionnaire data, population and dog density as well as climatic data specific for the farm localization were used to identify potential risk factors for a herd to have acquired N. caninum infections. Within an optimized multiple logistic regression model 'Number of farm dogs', 'Herd size', and factors related to the municipality the farm was localized, i.e. 'Mean temperature in July', and 'Dog density' were significant risk factors (P(Wald)<0.1). The present study underlines the role farm dogs have in the epidemiology of neosporosis. In addition, it suggests that the risk a herd has to acquire N. caninum infections is also associated with factors related to the farm location, i.e. factors that are largely out of the control of farmers.

Abortion, Veterinary↗

PubMed2003

Regional distribution of bovine Neospora caninum infection in the German state of Rhineland-Palatinate modelled by Logistic regression.

To obtain a rapid overview over the distribution of bovine Neospora caninum-infections in the German state of Rhineland-Palatinate, an ELISA to determine specific bovine antibodies against a p38 surface antigen of N. caninum tachyzoites was modified to examine bulk milk samples from cattle herds. Experimental bulk milk samples were used to demonstrate that the seroprevalence in a group of animals can be estimated with this ELISA. A cut-off was selected for the specific detection of herds having a seroprevalence > or =10%. About 90% of the dairy herds located in Rhineland-Palatinate were examined. An overall prevalence of bulk milk-positive herds of 7.9% (95% confidence interval 7.0-8.9%), respectively, was determined. Major regional differences in the distribution of bulk milk-positive herds were observed. Prevalences were higher in regions with an increased degree of urbanisation. Logistic regression was applied to model the prevalence of bulk milk-positive herds on a district and city level. Variables describing the dog density, mean temperature in July, mean temperature in January and the total yearly precipitation in districts and cities were able to explain most of the observed variability in the regional prevalences. Our results provide evidence that in addition to risk factors related to individual farms also risk factors related to the farm location such as dog density in the surrounding and climate factors are important in the epidemiology of bovine neosporosis.

Animals↗

PubMed2002

A Bayesian model for spatial wildlife disease prevalence data.

The analysis of the geographical distribution of disease on the scale of geographic areas such as administrative boundaries plays an important role in veterinary epidemiology. Prevalence estimates of wildlife population surveys are often based on regional count data generated by sampling animals shot by hunters. The observed disease rate per spatial unit is not an useful estimate of the underlying disease prevalence due to different sample sizes and spatial dependencies between neighbouring areas. Therefore, it is necessary to account for extra-sample variation and spatial correlations in the data to produce more accurate maps of disease incidence. The detection of spatial patterns is complicated by missing data in many of the geographical areas as the complete coverage of all areas is nearly impossible in wildlife surveys. For this purpose a hierarchical Bayesian model in which structured and unstructured over dispersion is modelled explicitly in terms of spatial and non-spatial components was implemented by Markov chain Monte Carlo methods. The model was empirically compared with the results of a non-spatial beta-binomial model using surveillance data of pseudorabies virus infections of European wild boars (Sus scrofa scrofa L.) in the Federal State of Brandenburg, Germany.

Animal Diseases↗

PubMed2002

p38-avidity-ELISA: examination of herds experiencing epidemic or endemic Neospora caninum-associated bovine abortion.

An enzyme-linked immunosorbent assay (ELISA) was established to measure the avidity of bovine IgG directed against p38, a surface antigen (NCSRS2) of Neospora caninum tachyzoites. In the sera of dams intravenously infected with N. caninum NC-1, the p38-specific avidity increased from initially below 40% up to avidity indices between 50 and 80% after days 23 and 91 p.i. The p38-avidity-ELISA was used to examine various herds that had experienced endemic and epidemic N. caninum-associated bovine abortions. In herds with endemic abortion, generally high avidity indices of N. caninum-specific IgG were detected. This finding and the observation of an association between the seropositivity of dams and that of their offspring suggested a predominantly vertical transmission of the parasite among the animals of these herds, thus indicating chronic infection of these cattle. In contrast, for herds experiencing epidemic abortion: (i) an association regarding seropositivity of dams and their daughters could not be shown and (ii) a generally low avidity of p38-specific IgG in the sera from aborting dams was determined. This indicates recent postnatal transmission of N. caninum in these herds. A linear regression model explaining the avidity of p38-specific IgG was significantly influenced by the time span between sampling and the occurrence of the first abortion of the epidemic in herds with an N. caninum-associated abortion storm. Another factor significantly contributing to the model was the proportion of dams at risk that had aborted in the herds (i.e. the severity of the abortion epidemic). A possible explanation for this observation is that herds experiencing heavy abortion are sampled earlier after the onset of the epidemic than others that have a less severe abortion storm.

Abortion, Veterinary↗

PubMed2001

A field study to control Echinococcus multilocularis-infections of the red fox (Vulpes vulpes) in an endemic focus.

Foxes harbouring E. multilocularis represent an important source for human infection with this parasite which causes alveolar echinococcosis. To minimize the risk of human infection, a control study was conducted to reduce the prevalence of E. multilocularis-infection in foxes in an focal endemic area of 5000 km2. Foxes were given access to baits containing 50 mg praziquantel. Twenty baits per km2 were distributed by airplane during 14 campaigns. The effects of control measures were monitored by parasitological examination of 9387 foxes shot before and during the control trial. A distinct reduction of the prevalence of E. multilocularis was observed for both, the initially endemic area and the low-endemic periphery. The effect was more pronounced in adult than in juvenile foxes. Under control conditions, the risk area decreased in size. However, an eradication of the parasite was not reached with the chosen strategy.

Animals↗

PubMed2001

Geographic information system-aided analysis of factors associated with the spatial distribution of Echinococcus multilocularis infections of foxes.

To investigate the influence of environmental factors on the spatial epidemiology of infections with Echinococcus multilocularis, foxes were sampled in a focal endemic region in the Northwest of Brandenburg, Germany, and examined for infection by the parasite. The locations where foxes were obtained were recorded in a geographic information system database. Positions of infected and uninfected foxes were analyzed on the background of geographic vector data of water, settlements, streets, forests, crop, and pasture. Fox positions were allocated to different land-use classes by use of a Landsat Thematic Mapper (TM) satellite image. Infected foxes were more frequently shot near water, in areas of high soil humidity, and on pastures, suggesting that dryness may limit the tenacity of E. multilocularis oncospheres. Thus open landscapes with humid soil seem to be favorable for the life cycle of the parasite. In contrast, infected foxes were significantly underrepresented in forest areas.

Animals↗

PubMed2000

Epidemiology of classical swine fever in Germany in the 1990s.

In Germany, 424 outbreaks of CSF in domestic pigs and a great number of cases in wild boar were recorded between 1990 and 1998. Most of the federal states ('Bundesländer') were affected. Epidemiological data from field investigations combined with genetic typing allowed to distinguish seven unrelated epidemics and a number of sporadic outbreaks in domestic pigs. Detailed epidemiological data was available for 327 outbreaks. It was found that 28% of these were primary outbreaks. Most of them were due to indirect or direct contact to wild boar infected with CSF virus or swill feeding. Infected wild boar remain the main risk for domestic pigs. The most frequent sources of infection in secondary or follow up outbreaks were the trade with infected pigs, neighbourhood contacts to infected farms and other contacts via contaminated persons and vehicles, respectively. An increased risk of virus transmission from infected herds to neighbourhood farms was observed up to a radius of approximately 500m. More than two thirds of the infected herds were discovered due to clinical signs. About 20% were identified by epidemiological tracing on and back. These were scrutinised because contacts to infected herds were evident. In conclusion, tracing of contact herds and clinical examination combined with carefully targeted virological testing of suspicious animals is likely to be the most important measure to immediately uncover secondary outbreaks. Obligatory serological screening in the surveillance and the restriction zones do not seem to be efficient measures to detect follow-up outbreaks.

Animals↗

PubMed2000

Transient classical swine fever virus infection in wild boar piglets partially protected by maternal antibodies.

An experimental study was conducted to investigate the clinical course of classical swine fever (CSF) in wild boar piglets partially protected by maternal antibodies. Five healthy wild boar piglets with a low serum titre of colostral antibodies against CSF virus were challenged with virulent CSF virus at the age of three months. Apart of reduced food intake and diarrhoea no major clinical symptoms were noticed after challenge. These signs were seen during the second and third week of infection, afterwards the piglets recovered completely. CSF virus could be re-isolated from blood samples taken on day 12 and day 19 post challenge. From blood samples taken later on and from the organ material taken at post mortem examinations no CSF virus could be isolated anymore. It can be concluded that the presence of maternal antibodies influences the clinical course of CSF in terms that the outcome is rather transient than lethal. Such wild boar could play a crucial role in the spread of CSF virus and might contribute to the maintenance of long lasting epizootics.

Animals↗

PubMed1999

The spatio-temporal dynamics of a post-vaccination resurgence of rabies in foxes and emergency vaccination planning.

We used a simulation model to study the spatio-temporal dynamics of a potential rabies outbreak in an immunized fox population after the termination of a long-term, large-scale vaccination program with two campaigns per year one in spring and one in autumn. The 'worst-case' scenario of rabies resurgence occurs if rabies has persisted at a low prevalence despite control and has remained undetected by a customary surveillance program or if infected individuals invade to the control area. Even if the termination of a vaccination program entails such a risk of a subsequent new outbreak, prolonged vaccination of a wild host population is expensive and the declining cost-benefit ratio over time eventually makes it uneconomic. Based on the knowledge of the spatio-temporal dynamics of a potential new outbreak gained from our modelling study, we suggest "terminating but observing" to be an appropriate strategy. Simulating the decline of population immunity without revaccination, we found that a new outbreak of rabies should be detected by customary surveillance programs within two years after the termination of the control. The time until detection does not depend on whether vaccination was terminated within the fourth, fifth or sixth years of repeated biannual campaigns. But it is faster if the program was completed with an autumn campaign (because next-year dispersal then occurs after a noticeable decrease in population immunity). Finally, if a rabid fox is detected after terminating vaccination, we determine a rule for defining a circular hazard area based on the simulated spatial spread of rabies. The radius of this area should be increased with the time since the last vaccination campaign. The trade-off between the number of foxes potentially missed by the emergency treatment and the cost for the emergency measures in an enlarged hazard area was found.

Animals↗

PubMed1999

Liver fluke (Opisthorchiidae) findings in red foxes (Vulpes vulpes) in the eastern part of the Federal State Brandenburg, Germany--a contribution to the epidemiology of opisthorchiidosis.

Parasitological examination of 677 livers from red foxes shot in connection with a rabies control programme were carried out in the eastern districts of the Federal State Brandenburg/Germany in 1996. Of the foxes, 32.5% were positive for opisthorchiid flukes. Metorchis bilis, the most frequently occurring fluke was found in 28.1% of foxes with numbers between 1 and 185. Opisthorchis felineus was found in 6.7% of fox livers. A maximum of 169 specimens was removed from one animal. Pseudamphistomum truncatum was present in only 2 foxes. The percentage of positive foxes in different districts varied between 15.8 and 43.3%. Significant differences in fluke prevalence were found between districts with a high share of surface water compared with a district with a low percentage of surface water. No sex-dependent differences in opisthorchiid prevalence were established.

Animals↗

PubMed1999

Epidemiological analysis of Trichinella spiralis infections of foxes in Brandenburg, Germany.

In a cross-sectional study conducted between March 1993 and February 1995, 7103 indiscriminately collected foxes were examined for Trichinella larvae. A total of 3295 serum samples were serologically investigated with an ELISA based on excretory-secretory antigen. The proportion of serologically positive animals ranged between 3.3% and 17.6% in random samples from individual counties or towns and resulted in an estimated overall prevalence of 7.7% (95% CI: 6.9-8.7%). Trichinella larvae were detected in the muscles of five foxes, corresponding to an estimated prevalence of 0.07% in the total sample (95% CI: 0.02-0.16%). The analysis of DNA of the Trichinella isolates by random amplification of polymorphic DNA (RAPD) lead to the identification of the isolates as Trichinella spiralis. The differences between serological and parasitological findings are discussed.

Animals↗

PubMed1998

Chance and risk of controlling rabies in large-scale and long-term immunized fox populations.

The large-scale immunization of European fox populations against rabies is currently under the microscope for reducing the considerable expenditure without putting public health at risk. Empirical knowledge is inadequate to interpret the lasting sporadic incidences and, therefore, to verify the final success of the immunization campaigns. By using a proven simulation model we show that rabies can persist on a very low level in the form of spatio-temporal moving infection clusters within a highly immunized fox population. We found further: (i) the existence of a threshold after which the chance of eradicating the disease by vaccination increases clearly, and (ii) that at least six years of 70% mean immunization rate are required to guarantee a likely success.

Animals↗

PubMed1998

Spatial distribution patterns of Echinococcus multilocularis (Leuckart 1863) (Cestoda: Cyclophyllidea: Taeniidae) among red foxes in an endemic focus in Brandenburg, Germany.

Over a period of 40 months, 4374 foxes were randomly sampled from an area located in northwestern Brandenburg, Germany, and examined parasitologically for infections with Echinococcus multilocularis. Spatial analysis of the origin of infected animals identified two (one central and one southeastern) high-endemic foci with an estimated prevalence of 23.8%. By contrast, a prevalence of 4.9% was found in the remaining (low-endemic) area. The prevalences among juvenile and adult foxes were compared in the high-endemic and the low-endemic areas. To analyse the central high-endemic focus further, the random sample was stratified by zones representing concentric circles with a radius of 13 km (zone 1) or x(n-1) + 7 km for the remaining three zones from the apparent centre of this focus (anchor point). Prevalences calculated for each zone showed a decrease from zone 1 (18.8%) to zone 4 (2.4%) with significant differences for all zones but zones 3 and 4. The relative risk of an infection decreased rapidly in a distance range of 26 km around the high-endemic focus, whereas the relative risk remained unchanged within a distance of 5 km around the anchor point. The importance of heterogeneous spatial distribution patterns for the diagnosis and epidemiology of the infection is discussed.

Age Distribution↗