Nagetiere und Nagetierassoziierte Krankheitserreger

Farmers' Attitudes in Connection with the Potential for Rodent Prevention in Livestock Farming in a Municipality in North Rhine-Westphalia, Germany

Rodents in livestock farming constitute a threat to the one health approach. In the present observational case study, livestock farmers worked together with a pest controller within a pilot project. The aim of the study was to assess determinants associated with rodent-prevention potential. The study started in March 2019 on 24 livestock farms in a municipality in North Rhine-Westphalia/Germany. At the beginning of the project a survey on the determinants expected to be related to prevention potential was conducted. To determine the potential for rodent prevention, an expert person, who was not involved in the project before, assessed the on-site conditions of the farms after 1.5 years of project duration in 2020. The potential for rodent prevention was good for about half of the farms. There were significant differences in the willingness to make changes at the project's start between farms with a high and a low potential for rodent prevention after 1.5 years. There is a general need for action to provide farmers with more practical information on rodent control. This is aggravated by the insufficient advisory services offered to farmers. This study confirms the importance of implementing preventive measures in the control of rodents to ensure that anticoagulant rodenticides are handled responsibly to reduce the impact on non-target species.

[Viral zoonoses in Germany: a One Health perspective]

The COVID-19 pandemic and the increasing occurrence of monkeypox (mpox) diseases outside Africa have illustrated the vulnerability of populations to zoonotic pathogens. In addition, other viral zoonotic pathogens have gained importance in recent years.This review article addresses six notifiable viral zoonotic pathogens as examples to highlight the need for the One Health approach in order to understand the epidemiology of the diseases and to derive recommendations for action by the public health service. The importance of environmental factors, reservoirs, and vectors is emphasized, the diseases in livestock and wildlife are analyzed, and the occurrence and frequency of diseases in the population are described. The pathogens selected here differ in their reservoirs and the role of vectors for transmission, the impact of infections on farm animals, and the disease patterns observed in humans. In addition to zoonotic pathogens that have been known in Germany for a long time or were introduced recently, pathogens whose zoonotic potential has only lately been shown are also considered.For the pathogens discussed here, there are still large knowledge gaps regarding the transmission routes. Future One Health-based studies must contribute to the further elucidation of their transmission routes and the development of prevention measures. The holistic approach does not necessarily include a focus on viral pathogens/diseases, but also includes the question of the interaction of viral, bacterial, and other pathogens, including antibiotic resistance and host microbiomes.

Start-up financing of professional pest control in pig farming in North Rhine-Westphalia in Germany

Background

Due to the risk of spreading epizootic diseases through rodents, pest control is mandatory in pig farming in European countries. However, there is limited research focused on rodent control practices, usage of anticoagulant rodenticides, and the acceptance of Pest Control Operators (PCOs) in pig farming in Germany. Therefore, the present study aims to investigate current control practices in pig holdings and to analyze the potential of a financial support on the implementation of professional pest control.

Results

Data were collected from monitoring records of PCOs and personal interviews with farmers and PCOs. 33 of 47 farmers, who were offered the possibility to outsource rodent control to PCOs supported by financial contribution of the North Rhine-Westphalian Animal Disease Fund (TSK) for a period of 2 years, joined the project.Despite the widespread opinion that the professional would not be beneficial - the authors figured out that farmers could financially benefit in time saved and by improved rodent control measures from the work of the PCOs. Costs of pest control measures per operation on average did not differ significantly between costs incurred by employment of PCOs (1.310 € per year) and calculated costs that arise by farmers themselves (1.217 € per year).All PCOs used Difenacoum and Brodifacoum against pest infestations. In doing so, the infestation with rodents was reduced and most of the participating farmers assessed the project as successful and employ the PCOs permanently. However, mapping the farm locations to resistance areas of the Rodenticide Resistance Action Committee (RRAC) shows that Brodifacoum was frequently used in areas which are marked as areas that are at low risk or rather have no risk for resistance. The environmental risks, however, are increased in these areas.

Conclusion

The instrument of temporal start-up financing professional pest control allows ensuring the continuous engagement of PCOs after the project period. This could possibly lead to long-term effects on the individual farm hygiene and on disease prevention. Nevertheless, important research questions with regard to the application of anticoagulant rodenticides of farmers and PCOs in livestock farming and with regard to risk mitigation measures were generated, meriting further investigation.

Lysogenic conversion of atypical enteropathogenic Escherichia coli (aEPEC) from human, murine, and bovine origin with bacteriophage Φ3538 Δstx2::cat proves their enterohemorrhagic E. coli (EHEC) progeny

Bacteriophages play an important role in the evolution of bacterial pathogens. A phage-mediated transfer of stx-genes to atypical enteropathogenic E. coli (aEPEC) which are prevalent in different hosts, would convert them to enterohemorrhagic E. coli (EHEC). We decided to confirm this hypothesis experimentally to provide conclusive evidence that aEPEC isolated from different mammalian hosts are indeed progenitors of typical EHEC which gain the ability to produce Shiga-Toxin by lysogeny with stx-converting bacteriophages, utilizing the model phage Φ3538 Δstx₂::cat. We applied a modified in vitro plaque-assay, using a high titer of a bacteriophage carrying a deletion in the stx₂ gene (Φ3538 Δstx₂::cat) to increase the detection of lysogenic conversion events. Three wild-type aEPEC strains were chosen as acceptor strains: the murine aEPEC-strain IMT14505 (sequence type (ST)28, serotype Ont:H6), isolated from a striped field mouse (Apodemus agrarius) in the surrounding of a cattle shed, and the human aEPEC-strain 910#00 (ST28, Ont:H6). The close genomic relationship of both strains implies a high zoonotic potential. A third strain, the bovine aEPEC IMT19981, was of serotype O26:H11 and ST21 (STC29). All three aEPEC were successfully lysogenized with phage Φ3538 Δstx₂::cat. Integration of the bacteriophage DNA into the aEPEC host genomes was confirmed by amplification of chloramphenicol transferase (cat) marker gene and by Southern-Blot hybridization. Analysis of the whole genome sequence of each of the three lysogens showed that the bacteriophage was integrated into the known tRNA integration site argW, which is highly variable among E. coli. In conclusion, the successful lysogenic conversion of aEPEC with a stx-phage in vitro underlines the important role of aEPEC as progenitors of EHEC. Given the high prevalence and the wide host range of aEPEC acceptors, their high risk of zoonotic transmission should be recognized in infection control measures.

Occurrence and distribution of Giardia species in wild rodents in Germany

BACKGROUND

Giardiasis is an important gastrointestinal parasitic disease in humans and other mammals caused by the protozoan Giardia duodenalis. This species complex is represented by genetically distinct groups (assemblages A-H) with varying zoonotic potential and host preferences. Wild rodents can harbor potentially zoonotic assemblages A and B, and the rodent-specific assemblage G. Other Giardia spp. found in these animals are Giardia muris and Giardia microti. For the latter, only limited information on genetic typing is available. It has been speculated that wild rodents might represent an important reservoir for parasites causing human giardiasis. The aim of this study was to investigate the occurrence and distribution of Giardia spp. and assemblage types in wild rodents from different study sites in Germany.

RESULTS

Screening of 577 wild rodents of the genera Apodemus, Microtus and Myodes, sampled at eleven study sites in Germany, revealed a high overall Giardia prevalence. Giardia species determination at the SSU rDNA gene locus revealed that Apodemus mice, depending on species, were predominantly infected with one of two distinct G. muris sequence types. Giardia microti was the predominant parasite species found in voles of the genera Microtus and Myodes. Only a few animals were positive for potentially zoonotic G. duodenalis. Subtyping at the beta-giardin (bg) and glutamine dehydrogenase (gdh) genes strongly supported the existence of different phylogenetic subgroups of G. microti that are preferentially harbored by distinct host species.

CONCLUSIONS

The present study highlights the preference of G. muris for Apodemus, and G. microti for Microtus and Myodes hosts and argues for a very low prevalence of zoonotic G. duodenalis assemblages in wild rodents in Germany. It also provides evidence that G. muris and G. microti subdivide into several phylogenetically distinguishable subgroups, each of which appears to be preferentially harbored by species of a particular rodent host genus. Finally, the study expands the database of sequences relevant for sequence typing of G. muris and G. microti isolates which will greatly help future analyses of these parasites' population structure.

[Monitoring populations of rodent reservoirs of zoonotic diseases. Projects, aims and results]

Rodents can harbor and transmit pathogens that can cause severe disease in humans, companion animals and livestock. Such zoonotic pathogens comprise more than two thirds of the currently known human pathogens. The epidemiology of some zoonotic pathogens, such as hantaviruses, can be linked to the population dynamics of the rodent host. In this case, during an outbreak of the rodent host population many human infections may occur. In other rodent-borne zoonotic diseases such phenomena are not known and in many cases the rodent host specificity of a given pathogen is unclear. The monitoring of relevant rodent populations and of the rodent-borne zoonotic pathogens is essential to (1) understand the distribution and epidemiology of pathogens and (2) develop forecasting tools to predict outbreaks of zoonoses. Presently, there are no systematic long-term monitoring programs in place for zoonoses in Germany. Rodent monitoring activities are largely restricted to the plant protection sector, such as for the common vole (Microtus arvalis) and forest-damaging rodents. However, during the last 10-15 years a number of specific research projects have been initiated and run for a few years and Norway rat (Rattus norvegicus) monitoring has been implemented in Hamburg and Lower Saxony. Based on close cooperation of federal and state authorities and research institutions these efforts could be utilized to gain information about the distribution and importance of rodent-borne zoonoses. Nevertheless, for the integration of rodent population dynamics and zoonotic disease patterns and especially for developing predictive models, long-term monitoring is urgently required. To establish a systematic long-term monitoring program, existing networks and cooperation need to be used, additional collaborators (e.g., pest control operators) should be included and synergetic effects of different scientific fields should be utilized.

Continental-scale footprint of balancing and positive selection in a small rodent (Microtus arvalis)

Genetic adaptation to different environmental conditions is expected to lead to large differences between populations at selected loci, thus providing a signature of positive selection. Whereas balancing selection can maintain polymorphisms over long evolutionary periods and even geographic scale, thus leads to low levels of divergence between populations at selected loci. However, little is known about the relative importance of these two selective forces in shaping genomic diversity, partly due to difficulties in recognizing balancing selection in species showing low levels of differentiation. Here we address this problem by studying genomic diversity in the European common vole (Microtus arvalis) presenting high levels of differentiation between populations (average F_ST = 0.31). We studied 3,839 Amplified Fragment Length Polymorphism (AFLP) markers genotyped in 444 individuals from 21 populations distributed across the European continent and hence over different environmental conditions. Our statistical approach to detect markers under selection is based on a Bayesian method specifically developed for AFLP markers, which treats AFLPs as a nearly codominant marker system, and therefore has increased power to detect selection. The high number of screened populations allowed us to detect the signature of balancing selection across a large geographic area. We detected 33 markers potentially under balancing selection, hence strong evidence of stabilizing selection in 21 populations across Europe. However, our analyses identified four-times more markers (138) being under positive selection, and geographical patterns suggest that some of these markers are probably associated with alpine regions, which seem to have environmental conditions that favour adaptation. We conclude that despite favourable conditions in this study for the detection of balancing selection, this evolutionary force seems to play a relatively minor role in shaping the genomic diversity of the common vole, which is more influenced by positive selection and neutral processes like drift and demographic history.

Rickettsia spp. in wild small mammals in Lower Bavaria, South-Eastern Germany

So far, data on the natural cycle of rickettsiae of the tick-borne spotted fever group (SFG) in Central Europe are barely available. Some studies showed the occurrence of different Rickettsia species in their arthropod vectors, but it is unclear which animals might have any kind of reservoir function. This survey was therefore set up to provide information on the occurrence of SFG rickettsiae in small mammals in Germany. A total of 124 rodents and insectivores were collected over a period of 3 years in Lower Bavaria, South-Eastern Germany. Screening for Rickettsia antibodies was performed using immunofluorescence with Rickettsia conorii and R. helvetica slides, and the comparability of sera and body fluids (transudates) was investigated in these assays. Further, real-time polymerase chain reaction (PCR) was used for screening of Rickettsial DNA in rodents and insectivores. Ear versus liver tissue was compared to evaluate the more suitable tissue for detection of specific DNA. Further, a new PCR targeting the 18S ribosomal nucleic acid was established as internal control. The results indicated that transudates are a sufficient alternative to proof infection in cases where no sera are available. Rickettsial DNA, that is, Rickettsia felis and R. helvetica, was found in seven animals with the ears proving to be a proper choice for PCR. Statistical analyses revealed that the presence of ectoparasites and the body size positively correlated with the occurrence of rickettsial DNA. Overall, our study suggests that rodents and other small mammals may act as reservoir hosts for Rickettsia. However, with the course of infection and its transmission in wild animals still unknown, further investigations are needed to better understand the natural cycle of SFG rickettsiae.

First insights into antimicrobial resistance among faecal Escherichia coli isolates from small wild mammals in rural areas

Wild rodents can be carriers of antimicrobial resistant Escherichia coli. As rodents are known to be involved in the transmission of bacteria of human and animal health concern, they could likewise contribute to the dissemination of antimicrobial resistant bacteria in the environment. The aim of this study was therefore to get first insights into the antimicrobial resistance status among E. coli isolated from wild small mammals in rural areas. We tested 188 faecal isolates from eight rodent and one shrew species originating from Germany. Preselected resistant isolates were screened by minimal inhibitory concentration (MIC) testing or agar diffusion test and subsequent PCR analysis of resistance genes. The prevalence of antimicrobial resistant isolates was low with only 5.5% of the isolates exhibiting resistant phenotypes against at least one antimicrobial compound including beta-lactams, tetracyclines, aminoglycosides and sulfonamides. These results suggest a minor role of wild rodents from rural areas in the cycle of transmission and spread of antimicrobial resistant E. coli into the environment. Nevertheless E. coli with multiple antimicrobial resistances were significantly more often detected in wildlife rodents originating from areas with high livestock density suggesting a possible transmission from livestock to wild rodents.