Publications by authors named "Franz J Conraths"

117 Publications

Molecular analysis suggests that Namibian cheetahs (Acinonyx jubatus) are definitive hosts of a so far undescribed Besnoitia species.

Parasit Vectors 2021 Apr 14;14(1):201. Epub 2021 Apr 14.

Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Street 17, 10315, Berlin, Germany.

Background: Besnoitia darlingi, B. neotomofelis and B. oryctofelisi are closely related coccidian parasites with felids as definitive hosts. These parasites use a variety of animal species as intermediate hosts. North American opossums (Didelphis virginiana), North American southern plains woodrats (Neotoma micropus) and South American domestic rabbits (Oryctolagus cuniculus) are intermediate hosts of B. darlingi, B. neotomofelis and B. oryctofelisi, respectively. Based on conserved regions in the internal transcribed spacer-1 (ITS1) sequence of the ribosomal DNA (rDNA), a real-time PCR for a sensitive detection of these Besnoitia spp. in tissues of intermediate hosts and faeces of definitive hosts has recently been established. Available sequence data suggest that species such as B. akodoni and B. jellisoni are also covered by this real-time PCR. It has been hypothesised that additional Besnoitia spp. exist worldwide that are closely related to B. darlingi or B. darlingi-like parasites (B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni). Also related, but not as closely, is B. besnoiti, the cause of bovine besnoitiosis.

Methods: Faecal samples from two free-ranging cheetahs (Acinonyx jubatus) from Namibia that had previously tested positive for coccidian parasites by coproscopy were used for this study. A conventional PCR verified the presence of coccidian parasite DNA. To clarify the identity of these coccidia, the faecal DNA samples were further characterised by species-specific PCRs and Sanger sequencing.

Results: One of the samples tested positive for B. darlingi or B. darlingi-like parasites by real-time PCR, while no other coccidian parasites, including Toxoplasma gondii, Hammondia hammondi, H. heydorni, B. besnoiti and Neospora caninum, were detected in the two samples. The rDNA of the B. darlingi-like parasite was amplified and partially sequenced. Comparison with existing sequences in GenBank revealed a close relationship to other Besnoitia spp., but also showed clear divergences.

Conclusions: Our results suggest that a so far unknown Besnoitia species exists in Namibian wildlife, which is closely related to B. darlingi, B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni. The cheetah appears to be the definitive host of this newly discovered parasite, while prey species of the cheetah may act as intermediate hosts.
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http://dx.doi.org/10.1186/s13071-021-04697-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048190PMC
April 2021

Introduction and spread of variegated squirrel bornavirus 1 (VSBV-1) between exotic squirrels and spill-over infections to humans in Germany.

Emerg Microbes Infect 2021 Dec;10(1):602-611

Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.

The variegated squirrel bornavirus 1 (VSBV-1) is a recently discovered emerging viral pathogen which causes severe and eventually fatal encephalitis in humans after contact to exotic squirrels in private holdings and zoological gardens. Understanding the VSBV-1 epidemiology is crucial to develop, implement, and maintain surveillance strategies for the detection and control of animal and human infections. Based on a newly detected human encephalitis case in a zoological garden, epidemiological squirrel trade investigations and molecular phylogeny analyses of VSBV-1 with temporal and spatial resolution were conducted. Phylogenetic analyses indicated a recent emergence of VSBV-1 in European squirrel holdings and several animal-animal and animal-human spill-over infections. Virus phylogeny linked to squirrel trade analysis showed the introduction of a common ancestor of the known current VSBV-1 isolates into captive exotic squirrels in Germany, most likely by Prevost's squirrels (). The links of the animal trade between private breeders and zoos, the likely introduction pathway of VSBV-1 into Germany, and the role of a primary animal distributor were elucidated. In addition, a seroprevalence study was performed among zoo animal caretakers from VSBV-1 affected zoos. No seropositive healthy zoo animal caretakers were found, underlining a probable high-case fatality rate of human VSBV-1 infections. This study illustrates the network and health consequences of uncontrolled wild pet trading as well as the benefits of molecular epidemiology for elucidation and future prevention of infection chains by zoonotic viruses. To respond to emerging zoonotic diseases rapidly, improved regulation and control strategies are urgently needed.
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http://dx.doi.org/10.1080/22221751.2021.1902752DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8018504PMC
December 2021

What Do Lithuanian Hunters Think of African Swine Fever and Its Control-Perceptions.

Animals (Basel) 2021 Feb 18;11(2). Epub 2021 Feb 18.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald, Germany.

After the introduction of African swine fever (ASF) into Lithuania in 2014, continuous spread of the disease resulted in infection of the wild boar populations in most parts of Lithuania. The virus has been moving closer to other Western European countries where pig density is high. An efficient surveillance system detecting ASF cases early in domestic and wild animals is necessary to manage this disease. To make surveillance appropriate and effective, it is critical to understand how key players perceive the implemented control measures. This study investigated the attitudes and beliefs of hunters in Lithuania regarding currently implemented or proposed measures for the control of ASF in the wild boar population. Study data were collected through questionnaires distributed via the internet and by hunting associations in Lithuania. In total, 621 fully completed questionnaires were received and analyzed. All measures interfering with extensive hunting, like ban of driven or individual hunting or ban of supplementary feeding were considered as unacceptable and as ineffective measures to control ASF in wild boar. However, selective hunting of female wild boar was generally considered as an unethical act and therefore rejected. Some measures that seem to have been successful in other countries, like involvement of additional forces, were rejected by Lithuanian hunters, thus implementation of these measures could be difficult. The study highlighted that there is a need for improving important relationships with other stakeholders, since many hunters expressed a lack of trust in governmental institutions and regarded cooperation with them as insufficient. Hunters emphasized that their motivation to support passive surveillance measures could be improved with financial compensation and reduction of workload. The present study provides insights into hunters' perceptions, which may be used as a foundation for additional discussions with these important stakeholders and for adapting measures to improve their acceptance if appropriate.
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http://dx.doi.org/10.3390/ani11020525DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7922269PMC
February 2021

A real-time quantitative polymerase chain reaction for the specific detection of Hammondia hammondi and its differentiation from Toxoplasma gondii.

Parasit Vectors 2021 Jan 25;14(1):78. Epub 2021 Jan 25.

National Reference Laboratory for Toxoplasmosis, Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald-Insel Riems, Germany.

Introduction: Hammondia hammondi and Toxoplasma gondii are closely related protozoan parasites, but only T. gondii is zoonotic. Both species use felids as definitive hosts and cannot be differentiated by oocyst morphology. In T. gondii, a 529-base pair (bp) repetitive element (TgREP-529) is of utmost diagnostic importance for polymerase chain reaction (PCR) diagnostic tests. We identified a similar repetitive region in the H. hammondi genome (HhamREP-529).

Methods: Based on reported sequences, primers and probes were selected in silico and optimal primer probe combinations were explored, also by including previously published primers. The analytical sensitivity was tested using serial dilutions of oocyst DNA. For testing analytical specificity, DNA isolated from several related species was used as controls. The newly established TaqMan PCR (Hham-qPCR1) was applied to tissues collected from H. hammondi-infected gamma-interferon gene knockout (GKO) mice at varying time points post-infection.

Results: Ten forward and six reverse primers were tested in varying combinations. Four potentially suitable dual-labelled probes were selected. One set based on the primer pair (Hham275F, Hham81R) and the probe (Hham222P) yielded optimal results. In addition to excellent analytic specificity, the assay revealed an analytical sensitivity of genome equivalents of less than one oocyst. Investigation of the tissue distribution in GKO mice revealed the presence of parasite DNA in all examined organs, but to a varying extent, suggesting 100- to 10,000-fold differences in parasitic loads between tissues in the chronic state of infection, 42 days post-infection.

Discussion: The use of the 529-bp repeat of H. hammondi is suitable for establishing a quantitative real-time PCR assay, because this repeat probably exists about 200 times in the genome of a single organism, like its counterpart in T. gondii. Although there were enough sequence data available, only a few of the primers predicted in silico revealed sufficient amplification; the identification of a suitable probe was also difficult. This is in accord with our previous observations on considerable variability in the 529-bp repetitive element of H. hammondi.

Conclusions: The H. hammondi real-time PCR represents an important novel diagnostic tool for epidemiological and cell biological studies on H. hammondi and related parasites.
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http://dx.doi.org/10.1186/s13071-020-04571-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830817PMC
January 2021

Spatial distance between sites of sampling associated with genetic variation among Neospora caninum in aborted bovine foetuses from northern Italy.

Parasit Vectors 2021 Jan 13;14(1):47. Epub 2021 Jan 13.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald-Insel Riems, Germany.

Background: Neospora caninum, a coccidian protozoan, represents an important cause of bovine abortion. Available N. caninum strains show considerable variation in vitro and in vivo, including different virulence in cattle. To which extent sexual recombination, which is possible in the intestines of domestic dogs and closely related carnivores as definitive hosts, contributes to this variation is not clear yet.

Methods: Aborted bovine foetuses were collected between 2015 and early 2019 from Italian Holstein Friesian dairy herds suffering from reproductive problems. A total of 198 samples were collected from 165 intensive farms located in Lombardy, northern Italy. N. caninum samples were subjected to multilocus-microsatellite genotyping using ten previously established microsatellite markers. In addition to our own data, those from a recent study providing data on five markers from other northern Italian regions were included and analysed.

Results: Of the 55 samples finally subjected to genotyping, 35 were typed at all or 9 out of 10 loci and their individual multilocus-microsatellite genotype (MLMG) determined. Linear regression revealed a statistically significant association between the spatial distance of the sampling sites with the genetic distance of N. caninum MLMGs (P < 0.001). Including data from this and a previous North Italian study into eBURST analysis revealed that several of N. caninum MLMGs from northern Italy separate into four groups; most of the samples from Lombardy clustered in one of these groups. Principle component analysis revealed similar clusters and confirmed MLMG groups identified by eBURST. Variations observed between MLMGs were not equally distributed over all loci, but predominantly observed in MS7, MS6A, or MS10.

Conclusions: Our findings confirm the concept of local N. caninum subpopulations. The geographic distance of sampling was associated with the genetic distance as determined by microsatellite typing. Results suggest that multi-parental recombination in N. caninum is a rare event, but does not exclude uniparental mating. More comprehensive studies on microsatellites in N. caninum and related species like Toxoplasma gondii should be undertaken, not only to improve genotyping capabilities, but also to understand possible functions of these regions in the genomes of these parasites.
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http://dx.doi.org/10.1186/s13071-020-04557-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805081PMC
January 2021

Testing Different Deterrents as Candidates for Short-Term Reduction in Wild Boar Contacts-A Pilot Study.

Animals (Basel) 2020 Nov 19;10(11). Epub 2020 Nov 19.

Friedrich-Loeffler-Institut, Institute of Epidemiology, 17493 Greifswald, Germany.

African swine fever (ASF) is a viral infection of pigs and represents a major threat to animal health and trade. Due to the high tenacity of the causative virus in carcasses of wild boar, contacts of wild boar with infectious carcasses are regarded an important driver of the so-called habitat cycle. The latter is believed to play a major role in maintaining the present ASF situation in wild boar in Europe. Therefore, search campaigns and timely removal and disposal of carcasses are considered important disease control approaches. If timely disposal is not feasible due to logistic reasons, deterrence of wild boar may be a provisionary option. The performance of seven deterrents (physical and chemical) was tested in a forest near Greifswald, Germany. Carcasses as entities of attraction for wild boar were substituted by luring sites. It could be demonstrated in this pilot study that certain physical (LED blinkers, aluminum strips) and chemical (HAGOPUR Wildschwein-Stopp™, Hukinol™) deterrents are capable of reducing the odds of wild boar contacts to one third, but in depth testing of the aforementioned promising deterrent candidates is recommended. A choice of those deterrents identified as suitable, reasonable, and easy to apply should be carried out, when carcass search campaigns are launched in the case of an outbreak of ASF in wild boar.
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http://dx.doi.org/10.3390/ani10112156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7699385PMC
November 2020

Joining the club: First detection of African swine fever in wild boar in Germany.

Transbound Emerg Dis 2020 Oct 21. Epub 2020 Oct 21.

Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.

African swine fever (ASF) has spread across many countries in Europe since the introduction into Georgia in 2007. We report here on the first cases of ASF in wild boar detected in Germany close to the border with Poland. In addition to the constant risk of ASF virus (ASFV) spread through human activities, movements of infected wild boar also represent a route of introduction. Since ASF emerged in Western Poland in November 2019, surveillance efforts, in particular examination of wild boar found dead, were intensified in the regions of Germany bordering with Poland. The first case of ASF in wild boar in Germany was therefore detected by passive surveillance and confirmed on 10 September 2020. By 24 September 2020, 32 cases were recorded. Testing of samples from tissues of carcasses in different stages of decomposition yielded cycle threshold values from 18 to 36 in the OIE-recommended PCR, which were comparable between the regional and national reference laboratory. Blood swabs yielded reliable results, indicating that the method is suitable also under outbreak conditions. Phylogenetic analysis of the ASFV whole-genome sequence generated from material of the first carcass detected in Germany, revealed that it groups with ASFV genotype II including all sequences from Eastern Europe, Asia and Belgium. However, some genetic markers including a 14 bp tandem repeat duplication in the O174L gene were confirmed that have so far been detected only in sequences from Poland (including Western Poland). Epidemiological investigations that include estimated postmortem intervals of wild boar carcasses of infected animals suggest that ASFV had been introduced into Germany in the first half of July 2020 or even earlier.
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http://dx.doi.org/10.1111/tbed.13890DOI Listing
October 2020

Stability of African Swine Fever Virus in Carcasses of Domestic Pigs and Wild Boar Experimentally Infected with the ASFV "Estonia 2014" Isolate.

Viruses 2020 10 1;12(10). Epub 2020 Oct 1.

Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany.

Europe is currently experiencing a long-lasting African swine fever (ASF) epidemic, both in domestic pigs and wild boar. There is great concern that carcasses of infected wild boar may act as long-term virus reservoirs in the environment. We evaluated the tenacity of ASF virus (ASFV) in tissues and body fluids from experimentally infected domestic pigs and wild boar, which were stored on different matrices and at different temperatures. Samples were analysed at regular intervals for viral genome and infectious virus. ASFV was most stable in spleen or muscles stored at -20 °C and in blood stored at 4 °C. In bones stored at -20 °C, infectious virus was detected for up to three months, and at 4 °C for up to one month, while at room temperature (RT), no infectious virus could be recovered after one week. Skin stored at -20 °C, 4 °C and RT remained infectious for up to three, six and three months, respectively. In urine and faeces, no infectious virus was recovered after one week, irrespective of the matrix. In conclusion, tissues and organs from decomposing carcasses that persist in the environment for a long time can be a source of infection for several months, especially at low temperatures.
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http://dx.doi.org/10.3390/v12101118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7600355PMC
October 2020

Species Detection within the Complex by Novel Probe-Based Real-Time PCRs.

Pathogens 2020 Sep 26;9(10). Epub 2020 Sep 26.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, National Reference Centre for Echinococcosis, 17493 Greifswald-Insel Riems, Germany.

Infections with eggs of () can cause cystic echinococcosis in intermediate host animals and humans. Upon ingestion of viable eggs, oncospheres hatch from the eggs and subsequently develop into fluid-filled larval cysts, most frequently in the liver or the lungs. The slowly growing cysts progressively interfere with organ function. The risk of infection is determined by the host range of the parasite, its pathogenicity and other epidemiologically relevant parameters, which differ significantly among the five species within the complex. It is therefore essential to diagnose the correct species within to help understand specific disease epidemiology and to facilitate effective implementation of control measures. For this purpose, simple, fast and cost-effective typing techniques are needed. We developed quantitative real-time polymerase chain reactions (qPCRs) to target polymorphic regions in the mitochondrial genome of In a single-step typing approach, we distinguished members in four epidemiologically relevant subgroups. These were , , and the cluster. The technique also allowed identification and differentiation of these species from other Echinococcus or Taenia taxa for samples isolated from cysts or faeces.
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http://dx.doi.org/10.3390/pathogens9100791DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7599986PMC
September 2020

The genetics of highly pathogenic avian influenza viruses of subtype H5 in Germany, 2006-2020.

Transbound Emerg Dis 2020 Sep 22. Epub 2020 Sep 22.

Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Insel Riems, Germany.

The H5 A/Goose/Guangdong/1/1996 (gs/GD) lineage emerged in China in 1996. Rooted in the respective gs/GD lineage, the hemagglutinin (HA) gene of highly pathogenic avian influenza viruses (HPAIV) has genetically diversified into a plethora of clades and subclades and evolved into an assortment of sub- and genotypes. Some caused substantial losses in the poultry industry and had a major impact on wild bird populations alongside public health implications due to a zoonotic potential of certain clades. After the primary introduction of the HPAI H5N1 gs/GD lineage into Europe in autumn 2005 and winter 2005/2006, Germany has seen recurring incursions of four varying H5Nx subtypes (H5N1, H5N8, H5N5, H5N6) carrying multiple distinct reassortants, all descendants of the gs/GD virus. The first HPAIV H5 epidemic in Germany during 2006/2007 was caused by a clade 2.2 subtype H5N1 virus. Phylogenetic analysis confirmed three distinct clusters belonging to clades 2.2.1, 2.2.2 and 2.2, concurring with geographic and temporal structures. From 2014 onwards, HPAIV clade 2.3.4.4 has dominated the epidemiological situation in Germany. The initial clade 2.3.4.4a HPAIV H5N8, reaching Germany in November 2014, caused a limited epidemic affecting five poultry holdings, one zoo in Northern Germany and few wild birds. After November 2016, HPAIV of clade 2.3.4.4b have dominated the situation to date. The most extensive HPAIV H5 epidemic on record reached Germany in winter 2016/2017, encompassing multiple incursion events with two subtypes (H5N8, H5N5) and entailing five reassortants. A novel H5N6 clade 2.3.4.4b strain affected Germany from December 2017 onwards, instigating low-level infection in smallholdings and wild birds. Recently, in spring 2020, a novel incursion of a genetically distinct HPAI clade 2.3.4.4b H5N8 virus caused another epidemic in Europe, which affected a small number of poultry holdings, one zoo and two wild birds throughout Germany.
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http://dx.doi.org/10.1111/tbed.13843DOI Listing
September 2020

Hunters' Acceptance of Measures against African Swine Fever in Wild Boar in Estonia.

Prev Vet Med 2020 Sep 11;182:105121. Epub 2020 Aug 11.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald-Insel Riems, Germany. Electronic address:

African swine fever (ASF) was first identified in Estonia in 2014, initially detected in wild boar and spreading to affect almost the whole country from late 2016 onwards. Passive surveillance and the control measures applied in Estonia are the main actions in the attempt to control the wild boar population and therefore limit the spread of ASF. Implementation and success of both activities depend mainly on the involvement and commitment of the executing force: the Estonian hunters. Thus, their acceptance of the measures is of utmost importance and with the help of participatory methods, their acceptability can be assessed. Participatory epidemiology allows the involvement of key stakeholders in planning control measures and surveillance strategies and gathering information otherwise inaccessible. By conducting focus group discussions and utilizing participatory tools, this study aimed to assess the acceptance of ASF control measures by hunters in Estonia. Furthermore, the study aimed to detect means to improve the motivation of hunters to support passive surveillance. Among hunters, the results ranked the trust in lower authorities (e.g. local official veterinarians) towards implementing control measures as high (in contrast to higher officials e.g. 'Ministry of Rural Affairs'), while perceiving themselves as the most trustworthy group among those implementing ASF control measures. Hunting and every measure supporting increased hunting, for example selective hunting, bait feeding and incentives for hunting wild boar, were deemed favourable for hunters. These measures also received the highest trust for controlling ASF. All measures hindering hunting and the movement of wildlife, for example fencing or involvement of the army in ASF control, were described as unpleasant or even unethical and trust in these measures to control the disease successfully was lacking. When assessing the perceived consequences for hunters of finding a dead wild boar, arising financial costs, additional workload and time consumption were highlighted. In line with these results, the two tools with the strongest motivational effect for taking part in passive surveillance were: (1) higher monetary incentives as compensation for the hunters' work, and (2) the reduction of the negative consequences by limiting the hunters' duties to solely reporting found dead wild boar. In conclusion, participatory methods can be used as a highly suitable tool for the evaluation of acceptance of measures and surveillance systems. Potentially, the results can help to improve control and passive surveillance in Estonia, as well as functioning as an example for other countries battling or awaiting ASF.
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http://dx.doi.org/10.1016/j.prevetmed.2020.105121DOI Listing
September 2020

Fluorescent bead-based serological detection of Toxoplasma gondii infection in chickens.

Parasit Vectors 2020 Jul 31;13(1):388. Epub 2020 Jul 31.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, National Reference Centre for Toxoplasmosis, Greifswald-Insel Riems, Germany.

Background: Free-ranging chickens are often infected with Toxoplasma gondii and seroconvert upon infection. This indicates environmental contamination with T. gondii.

Methods: Here, we established a bead-based multiplex assay (BBMA) using the Luminex technology for the detection of T. gondii infections in chickens. Recombinant biotinylated T. gondii surface antigen 1 (TgSAG1) bound to streptavidin-conjugated magnetic Luminex beads served as antigen. Serum antibodies were detected by a fluorophore-coupled secondary antibody. Beads of differing color codes were conjugated with anti-chicken IgY or chicken serum albumin and served for each sample as an internal positive or negative control, respectively. The assay was validated with sera from experimentally and naturally infected chickens. The results were compared to those from reference methods, including other serological tests, PCRs and bioassay in mice.

Results: In experimentally infected chickens, the vast majority (98.5%, n = 65/66) of birds tested seropositive in the BBMA. This included all chickens positive by magnetic-capture PCR (100%, n = 45/45). Most, but not all inoculated and TgSAG1-BBMA-positive chickens were also positive in two previously established TgSAG1-ELISAs (TgSAG1-ELISA, n = 61/65; or TgSAG1-ELISA, n = 60/65), or positive in an immunofluorescence assay (IFAT, n = 64/65) and in a modified agglutination test (MAT, n = 61/65). All non-inoculated control animals (n = 28/28, 100%) tested negative. In naturally exposed chickens, the TgSAG1-BBMA showed a high sensitivity (98.5%; 95% confidence interval, CI: 90.7-99.9%) and specificity (100%; 95% CI: 85.0-100%) relative to a reference standard established using ELISA, IFAT and MAT. Almost all naturally exposed chickens that were positive in bioassay or by PCR tested positive in the TgSAG1-BBMA (93.5%; 95% CI: 77.1-98.9%), while all bioassay- or PCR-negative chickens remained negative (100%; 95% CI: 85.0-100%).

Conclusions: The TgSAG1-BBMA represents a suitable method for the detection of T. gondii infections in chickens with high sensitivity and specificity, which is comparable or even superior to other tests. Since assays based on this methodology allow for the simultaneous analysis of a single biological sample with respect to multiple analytes, the described assay may represent a component in future multiplex assays for broad serological monitoring of poultry and other farm animals for various pathogens.
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http://dx.doi.org/10.1186/s13071-020-04244-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393333PMC
July 2020

How to Demonstrate Freedom from African Swine Fever in Wild Boar-Estonia as an Example.

Vaccines (Basel) 2020 Jun 25;8(2). Epub 2020 Jun 25.

Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald, Insel Riems, Germany.

Estonia has been combatting African swine fever (ASF) for six years now. Since October 2017, the disease has only been detected in the wild boar population, but trade restrictions had to remain in place due to international regulations. Yet, the epidemiological course of the disease has changed within the last few years. The prevalence of ASF virus (ASFV)-positive wild boar decreased steadily towards 0%. In February 2019, the last ASFV-positive wild boar was detected. Since then, positive wild boar samples have exclusively been positive for ASFV-specific antibodies, suggesting the possible absence of circulating ASFV in the Estonian wild boar population. However, as the role of seropositive animals is controversially discussed and the presence of antibody-carriers is regarded as an indication of virus circulation at EU and OIE level, Estonia remains under trade restrictions. To make the disease status of a country reliable for trading partners and to facilitate the process of declaration of disease freedom, we suggest to monitor the prevalence of seropositive wild boar in absence of ASFV-positive animals. The possibility to include ASF in the list of diseases, for which an official pathway for recognition of disease status is defined by the OIE should be evaluated.
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http://dx.doi.org/10.3390/vaccines8020336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7350251PMC
June 2020

Pitfalls in SARS-CoV-2 PCR diagnostics.

Transbound Emerg Dis 2021 Mar 5;68(2):253-257. Epub 2020 Jul 5.

Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.

To combat the COVID-19 pandemic, millions of PCR tests are performed worldwide. Any deviation of the diagnostic sensitivity and specificity will reduce the predictive values of the test. Here, we report the occurrence of contaminations of commercial primers/probe sets with the SARS-CoV-2 target sequence of the RT-qPCR as an example for pitfalls during PCR diagnostics affecting diagnostic specificity. In several purchased in-house primers/probe sets, quantification cycle values as low as 17 were measured for negative control samples. However, there were also primers/probe sets that displayed very low-level contaminations, which were detected only during thorough internal validation. Hence, it appears imperative to pre-test each batch of reagents extensively before use in routine diagnosis, to avoid false-positive results and low positive predictive value in low-prevalence situations. As such, contaminations may have happened more widely, and COVID-19 diagnostic results should be re-assessed retrospectively to validate the epidemiological basis for control measures.
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http://dx.doi.org/10.1111/tbed.13684DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7323359PMC
March 2021

ApiCOWplexa 2019 - 5th International Meeting on Apicomplexan Parasites in Farm Animals.

Int J Parasitol 2020 05;50(5):345-347

Australian Institute of Tropical Health & Medicine, James Cook University, Cairns, Queensland 4870, Australia.

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http://dx.doi.org/10.1016/j.ijpara.2020.05.002DOI Listing
May 2020

Stability of African swine fever virus on heat-treated field crops.

Transbound Emerg Dis 2020 Nov 8;67(6):2318-2323. Epub 2020 Jun 8.

Friedrich-Loeffler-Institut, Greifswald, Germany.

African swine fever (ASF) is an infectious disease of pigs and represents a massive threat to animal health and the pig industry worldwide. The ASF virus (ASFV) is efficiently transmitted via blood and meat from infected animals and can be highly stable in the environment. There is therefore great concern about the potential role of contaminated raw materials used for feed or bedding in the spread of ASFV. Especially crops and derived products originating from areas with ASF in wild boar and thus with high environmental ASFV contamination may be a risk for virus introduction into domestic pig herds. However, little is known about the stability of ASFV on contaminated crops and possible inactivation methods. In this study, we tested the effect of drying and heat treatment on the inactivation of ASFV on six different types of field crops, namely wheat, barley, rye, triticale, corn, and peas, contaminated with infectious blood. Samples were analysed for the presence of viral DNA and infectious virus after 2 hr drying at room temperature or after drying and 1 hr exposure to moderate heat at a specific temperature between 40°C and 75°C. ASFV genome was detected in all samples by real-time polymerase chain reaction (PCR), including samples that had been dried for 2 hr and incubated for 1 hr at 75°C. On the other hand, no infectious virus could be detected after 2 hr drying using virus isolation in porcine macrophages in combination with the detection of ASFV by the haemadsorption test (HAT). We therefore conclude that the risk of ASFV transmission via contaminated crops is most likely low, if they are incubated for at least 2 hr minimum at room temperature. Nonetheless, to minimize the risk of transmission as much as possible crops from ASF-affected zones should not be used for pig feed.
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http://dx.doi.org/10.1111/tbed.13650DOI Listing
November 2020

Author Correction: The potential role of scavengers in spreading African swine fever among wild boar.

Sci Rep 2020 May 20;10(1):8624. Epub 2020 May 20.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Greifswald-Insel Riems, Germany.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41598-020-65547-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7239944PMC
May 2020

Modelling the monthly abundance of Culicoides biting midges in nine European countries using Random Forests machine learning.

Parasit Vectors 2020 Apr 15;13(1):194. Epub 2020 Apr 15.

Institute of Parasitology and Tropical Pathology of Strasbourg, UR7292, Université de Strasbourg, Strasbourg, France.

Background: Culicoides biting midges transmit viruses resulting in disease in ruminants and equids such as bluetongue, Schmallenberg disease and African horse sickness. In the past decades, these diseases have led to important economic losses for farmers in Europe. Vector abundance is a key factor in determining the risk of vector-borne disease spread and it is, therefore, important to predict the abundance of Culicoides species involved in the transmission of these pathogens. The objectives of this study were to model and map the monthly abundances of Culicoides in Europe.

Methods: We obtained entomological data from 904 farms in nine European countries (Spain, France, Germany, Switzerland, Austria, Poland, Denmark, Sweden and Norway) from 2007 to 2013. Using environmental and climatic predictors from satellite imagery and the machine learning technique Random Forests, we predicted the monthly average abundance at a 1 km resolution. We used independent test sets for validation and to assess model performance.

Results: The predictive power of the resulting models varied according to month and the Culicoides species/ensembles predicted. Model performance was lower for winter months. Performance was higher for the Obsoletus ensemble, followed by the Pulicaris ensemble, while the model for Culicoides imicola showed a poor performance. Distribution and abundance patterns corresponded well with the known distributions in Europe. The Random Forests model approach was able to distinguish differences in abundance between countries but was not able to predict vector abundance at individual farm level.

Conclusions: The models and maps presented here represent an initial attempt to capture large scale geographical and temporal variations in Culicoides abundance. The models are a first step towards producing abundance inputs for R modelling of Culicoides-borne infections at a continental scale.
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http://dx.doi.org/10.1186/s13071-020-04053-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7161244PMC
April 2020

Monitoring of Pseudorabies in Wild Boar of Germany-A Spatiotemporal Analysis.

Pathogens 2020 Apr 10;9(4). Epub 2020 Apr 10.

Friedrich-Loeffler-Institut, Institute of Molecular Virology and Cell Biology, 17493 Greifswald-Insel Riems, Germany.

To evaluate recent developments regarding the epidemiological situation of pseudorabies virus (PRV) infections in wild boar populations in Germany, nationwide serological monitoring was conducted between 2010 and 2015. During this period, a total of 108,748 sera from wild boars were tested for the presence of PRV-specific antibodies using commercial enzyme-linked immunosorbent assays. The overall PRV seroprevalence was estimated at 12.09% for Germany. A significant increase in seroprevalence was observed in recent years indicating both a further spatial spread and strong disease dynamics. For spatiotemporal analysis, data from 1985 to 2009 from previous studies were incorporated. The analysis revealed that PRV infections in wild boar were endemic in all German federal states; the affected area covers at least 48.5% of the German territory. There were marked differences in seroprevalence at district levels as well as in the relative risk (RR) of infection of wild boar throughout Germany. We identified several smaller clusters and one large region, where the RR was two to four times higher as compared to the remaining areas under investigation. Based on the present monitoring intensity and outcome, we provide recommendations with respect to future monitoring efforts concerning PRV infections in wild boar in Germany.
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http://dx.doi.org/10.3390/pathogens9040276DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7238075PMC
April 2020

Research paper on abiotic factors and their influence on Ixodes ricinus activity-observations over a two-year period at several tick collection sites in Germany.

Parasitol Res 2020 May 26;119(5):1455-1466. Epub 2020 Mar 26.

Friedrich-Loeffler-Institut, Institute of Bacterial Infections and Zoonoses, Naumburger Str. 96a, D-07743, Jena, Germany.

Tick-borne diseases are a public health issue. To predict vector tick abundance and activity, it is necessary to understand the driving factors for these variables. In this study, the activity of Ixodes ricinus was investigated in forest and meadow habitats in Germany with a focus on abiotic factors. Ixodes ricinus adults, nymphs and larvae were caught by flagging over a period of 2 years. Microclimatic and weather conditions were recorded at the collection sites. Statistical models were applied to describe correlations between abiotic factors and tick activity in univariable and multivariable analyses. Tick activity was observed in a broad range of air temperature between 3 and 28 °C, and air humidity varied between 35 and 95%. In general, tick activity of nymphs and larvae was higher in forest habitats than that in meadows. With the exception of a single specimen of Dermacentor reticulatus, all ticks were Ixodes ricinus, most of them nymphs (63.2% in 2009 and 75.2% in 2010). For the latter, a negative binomial mixed-effects model fitted best to the observed parameters. The modelling results showed an activity optimum between 20 and 23 °C for air temperature and between 13 and 15 °C for ground temperature. In univariable analyses, the collection site, month, season, ground and air temperature were significant factors for the number of ticks caught and for all life stages. In the multivariable analysis, temperature, season and habitat turned out to be key drivers. Ixodes ricinus positive for RNA of tick-borne encephalitis virus was only found at a single sampling site. The results of this study can be used in risk assessments and to parameterise predictive models.
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http://dx.doi.org/10.1007/s00436-020-06666-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184057PMC
May 2020

Geographic Distribution of Raccoon Roundworm, Baylisascaris procyonis, Germany and Luxembourg.

Emerg Infect Dis 2020 04;26(4):821-823

Infestation with Baylisascaris procyonis, a gastrointestinal nematode of the raccoon, can cause fatal disease in humans. We found that the parasite is widespread in central Germany and can pose a public health risk. The spread of B. procyonis roundworms into nematode-free raccoon populations needs to be monitored.
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http://dx.doi.org/10.3201/eid2604.191670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7101099PMC
April 2020

First highly sensitive and specific competitive ELISA for detection of bovine besnoitiosis with potential as a multi-species test.

Int J Parasitol 2020 05 10;50(5):389-401. Epub 2020 Mar 10.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald, Insel Riems, Germany.

Serological cross-reactions represent a serious problem in some currently available tests to diagnose Besnoitia infections in many species including cattle, caribou and donkeys. False-positive results are due to the low positive-predictive value of these serological tests for besnoitiosis. These tests therefore have clear limitations if large herds are screened in areas with low prevalence, since increased numbers of false-positive reactions require confirmatory testing by alternative serological methods, e.g. immunoblotting, which are time-consuming and create extra costs. To overcome this problem, we aimed to develop a highly sensitive and specific competitive ELISA (cELISA) using a panel of 12 monoclonal antibodies raised against the tachyzoite stage of Besnoitia besnoiti. A cELISA set up with one of these antibodies (Bb-cELISA1) was screened with a large panel of B. besnoiti-positive bovine sera to estimate the diagnostic sensitivity of the test. Sera from herds with Neospora caninum- or Sarcocystis spp.-infected cattle were used to estimate its diagnostic specificity. Relative to a reference standard, which combined the results obtained in a previously established highly sensitive and specific ELISA, in the immunofluorescence antibody test and in B. besnoiti tachyzoite and bradyzoite immunoblots, the new Bb-cELISA1 revealed a diagnostic sensitivity of 99.2% (95% confidence interval: 97.1-99.9%) and a diagnostic specificity of 99.9% (95% confidence interval: 97.7-100%). This novel assay was tested on a variety of proven Besnoitia-positive sera from other species, including B. besnoiti-infected cats, rabbits or Besnoitia bennetti-infected donkeys or Besnoitia tarandi-infected caribou. The results obtained with the new Besnoitia-cELISA for these animal species also corresponded almost perfectly with those of the reference tests, which included immunoblot and immunofluorescence antibody tests. In conclusion, the novel Besnoitia-cELISA represents a valuable tool for the diagnosis and control of bovine besnoitiosis and for studies on the epidemiology of Besnoitia infections in a variety of host species, including naturally exposed wildlife and experimental hosts.
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http://dx.doi.org/10.1016/j.ijpara.2019.12.010DOI Listing
May 2020

Economic Impact of a Bluetongue Serotype 8 Epidemic in Germany.

Front Vet Sci 2020 14;7:65. Epub 2020 Feb 14.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Greifswald-Insel Riems, Germany.

Germany was affected by Bluetongue virus serotype 8 (BTV-8) from 2006 to 2009 and recorded new cases since December 2018. We assessed the economic impact of the epidemic from the first cases in 2006 until 2018. Direct costs include production losses, animal deaths, and veterinary treatment. Indirect costs include surveillance, additional measures for animal export, disease control (preventive vaccination and treatment with insecticides), vector monitoring, and administration. To estimate the financial impact of BTV-8 on different species and production types at the animal level, we performed a gross margin analysis (GMA) for dairy and beef cattle, and sheep. To estimate the impact on the national level, we used a modified framework described by Rushton et al. (1) and applied a methodology described by Bennett (2). Both the GMA and the economic model on national level were implemented in Excel and the Excel Add-in @Risk. The tools, which are widely applicable, also for other diseases, are made available here. The financial impact of a BTV-8 infection at the animal level was estimated at 119-136 Euros in dairy cattle, at 27 Euros in beef cattle, and at 74 Euros in sheep. At the national level, the impact of the BTV-8 epidemic ranged between 157 and 203 million Euros (mean 180 million Euros). This figure consisted of 132 (73%) and 48 (27%) million Euros for indirect and direct costs. Indirect costs included 89 million Euros (67%) for vaccination, 18 million Euros (14%) for insecticide treatment, 15 million Euros (11%) for diagnostic testing of animals dispatched for trade, 8 million Euros (6%) for monitoring and surveillance, and 3 million Euros (2%) for administration. The highest costs were induced by a compulsory vaccination campaign in 2008 (51 million Euros; 28% of the total costs) and the disease impact on cattle in 2007 (30 million Euros; 17%). We compare the outcome of our study with economic analyses of Bluetongue disease in other countries, and discuss the suitability of GMA and the developed tools for a wider application in veterinary economics.
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http://dx.doi.org/10.3389/fvets.2020.00065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7034324PMC
February 2020

Spatial-Temporal Dynamics of Hepatitis E Virus Infection in Foxes () in Federal State of Brandenburg, Germany, 1993-2012.

Front Microbiol 2020 31;11:115. Epub 2020 Jan 31.

Institute for Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.

Hepatitis E virus (HEV) is the main course for acute hepatitis in humans throughout the world. Human associated genotypes 1 and 2 as well as zoonotic genotypes 3 and 4 are grouped in the species . In addition, a large variety of HEV-related viruses has been found in vertebrates including carnivores, rats, bats, and chickens, which were classified in species . In 2015, partial genome sequences of a novel hepevirus were detected in feces of red foxes (). However, no further information about virus circulation and the prevalence in foxes was available. We therefore assayed a unique panel of 880 transudates, which was collected from red foxes over 19 years (1993-2012) in Brandenburg, Germany, for HEV-related viral RNA and antibodies. Our results demonstrate a high antibody prevalence of HEV in red foxes, which oscillated annually between 40 and 100%. Molecular screening of the transudates revealed only a single RNA-positive sample, which was assigned to the carnivore species based on the amplified partial sequence. These data indicate that the virus is circulating widely in the fox population and that foxes are carriers of this virus.
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http://dx.doi.org/10.3389/fmicb.2020.00115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7005575PMC
January 2020

Sensitive, quantitative detection of and related parasites in intermediate hosts and to assess felids as definitive hosts for known and as-yet undescribed related parasite species.

Int J Parasitol Parasites Wildl 2020 Apr 24;11:114-119. Epub 2020 Jan 24.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald, Insel Riems, Germany.

and are closely related coccidian parasites with cats as definitive hosts. While uses opossums as intermediate hosts, and have been described in Southern Plains woodrats () from the USA and in domestic rabbits from Argentina, respectively. A comparison of the Internal Transcribed Spacer-1 (ITS-1) region of the ribosomal DNA (rDNA) of these spp. showed only a few differences. The present study aimed at developing a real-time PCR to detect and in tissues of intermediate and in faeces of definitive hosts in order to support studies of these organisms' epidemiology and pathogenesis. The established PCR was based on primer regions distinct from the ITS-1 sequences of ungulate spp. and made use of a Besnoitia universal probe. To monitor inhibition, a heterologous internal control was established based on the enhanced green fluorescent protein gene. The real-time PCR reacted with , and while the novel PCR did not recognize ungulate spp. (). DNA of Apicomplexa ascribed to other Besnoitia-related genera, including other gut parasites of cats (, , ), was not recognized. The real-time PCR had an analytic sensitivity of less than 1 tachyzoite per reaction. In feline faeces spiked with oocysts, the limit of detection was a DNA amount equivalent to 1 oocyst per PCR reaction. In infected ɣ-interferon knock-out mice, the lung was identified as the predilection organ. In conclusion, this real-time PCR should advance further studies on these parasites and may inspire research on related species, not only in the Americas, but also in other parts of the world.
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http://dx.doi.org/10.1016/j.ijppaw.2020.01.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7000450PMC
April 2020

Modulation of lethal HPAIV H5N8 clade 2.3.4.4B infection in AIV pre-exposed mallards.

Emerg Microbes Infect 2020 23;9(1):180-193. Epub 2020 Jan 23.

Friedrich-Loeffler-Institut, Greifswald, Germany.

In 2016/2017, a severe epidemic of HPAIV H5N8 clade 2.3.4.4 group B (H5N8B) affected Europe. To analyse the role of mallards in the spatiotemporal dynamics of global HPAIV H5N8B dispersal, mallards (), naturally exposed to various AIV and therefore seropositive, were challenged with H5N8B. All experiments were controlled by infection and co-housing of seronegative juvenile Pekin ducklings. All ducks that survived the first infection were re-challenged 21 dpi with the homologous H5N8B strain. After the first H5N8B infection, seropositive mallards showed only mild clinical symptoms. Moderate to low viral shedding, occurring particularly from the oropharynx and lasting for 7 days maximum, led to severe clinical disease of all contact ducklings. All challenged seronegative Pekin ducks and contact ducklings died or had to be euthanized. H5-specific antibodies were detected in surviving birds within 2 weeks. Virus and viral RNA could be isolated from several water samples until 6 and 9 dpi, respectively. Conversely, upon re-infection with homologous H5N8B neither inoculated nor contact ducklings showed any clinical symptoms, nor was an antibody titer increase of seropositive mallards or any seroconversion of contact ducklings observed. Mallard ducks naturally pre-exposed to LPAIV can play a role as a clinically unsuspicious virus reservoir for H5N8B effective in virus transmission. Mallards with homologous immunity did not contribute to virus transmission.
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http://dx.doi.org/10.1080/22221751.2020.1713706DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7006783PMC
September 2020

Crimean-Congo haemorrhagic fever virus in ticks collected from livestock in Balochistan, Pakistan.

Transbound Emerg Dis 2020 Jul 25;67(4):1543-1552. Epub 2020 Feb 25.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Novel and Emerging Infectious Diseases, Greifswald-Insel Riems, Germany.

Background: Crimean-Congo haemorrhagic fever virus (CCHFV) is a tick-borne zoonotic pathogen. It causes a fatal haemorrhagic disease in humans. Hard ticks, in particular Hyalomma spp., are considered to function as reservoir as well as vector for CCHFV.

Methods: A cross-sectional study was conducted in the province of Balochistan, Pakistan, from September to November 2017. Ticks were collected from cattle, sheep and goats in livestock farms. The ticks were morphologically identified, followed by confirmation with molecular methods (PCR and sequencing). Furthermore, ticks were examined for CCHFV genomes (S segment) by a one-step multiplex real-time RT-qPCR and positive samples were sequenced to determine the CCHFV genotype.

Results: In total, 525 of 529 livestock infesting adult ticks belonged to the genus Hyalomma, and 4 ticks to the genus Rhipicephalus (R. microplus 3×, R. turanicus 1×). In the genus Hyalomma, H. marginatum (28%), H. excavatum (26%), H. dromedarii (22%), H. anatolicum (16%) and H. scupense (8%) ticks were identified. Tick infestations were as follows: sheep 58%, goats 28% and cattle 14%. Four per cent (20/525) of ticks were CCHFV genome-positive, and all genomes clustered in CCHFV genotype Asia 1. Among CCHFV-positive ticks, 75% (15/20) were female and 25% (5/20) male. CCHFV genomes were most frequently detected in H. marginatum (30%, 6/20), followed by H. dromedarii (25%, 5/20), H. excavatum (20%, 4/20), H. anatolicum (20%, 4/20) and H. scupense (5%, 1/20). All CCHFV-positive ticks were found on sheep. The largest number of CCHFV-positive ticks were detected in the district of Kalat (60%, 12/20), followed by the districts of Quetta (30%, 6/20) and Killa Abdullah (10%, 2/20).

Conclusions: This study confirms the circulation of CCHFV in ticks in Balochistan, south-western Pakistan. It is imperative to take effective tick control measures in this area, especially to control livestock tick infestations to prevent CCHF infections in humans.
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http://dx.doi.org/10.1111/tbed.13488DOI Listing
July 2020

Estimating the Postmortem Interval of Wild Boar Carcasses.

Vet Sci 2020 Jan 5;7(1). Epub 2020 Jan 5.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, 17493 Greifswald-Insel Riems, Germany.

Knowledge on the postmortem interval (PMI) of wild boar () carcasses is crucial in the event of an outbreak of African swine fever in a wild boar population. Therefore, a thorough understanding of the decomposition process of this species in different microhabitats is necessary. We describe the decomposition process of carcasses exposed in cages. Trial 1 compared a wild boar and a domestic pig () under similar conditions; Trial 2 was performed with three wild boar piglets in the sunlight, shade, or in a wallow, and Trial 3 with two adult wild boar in the sun or shade. The wild boar decomposed more slowly than the domestic pig, which shows that standards derived from forensic studies on domestic pigs are not directly applicable to wild boar. The carcasses exposed to the sun decomposed faster than those in the shade did, and the decomposition of the carcass in the wallow took longest. To assess the state of decomposition, we adapted an existing total body scoring system originally developed for humans. Based on our studies, we propose a checklist tailored to wild boar carcasses found in the field that includes the most important information for a reliable PMI estimation.
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http://dx.doi.org/10.3390/vetsci7010006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7157510PMC
January 2020

Locally temperature - driven mathematical model of West Nile virus spread in Germany.

J Theor Biol 2020 03 19;488:110117. Epub 2019 Dec 19.

Friedrich-Loeffler-Institut, Institute of Epidemiology, Südufer 10, Greifswald 17493, Germany. Electronic address:

West Nile virus (WNV) is an arthropod-borne virus (arbovirus) transmitted by the bites of infected mosquitoes. WNV can also infect horses and humans, where it may cause serious illness and can be fatal. Birds are the natural reservoir, and humans, equines and probably other mammals are dead-end hosts. In 2018, WNV occurred for the first time in Germany, affecting birds and horses. Seroconversion of an exposed veterinarian has also been reported. It is therefore of importance to evaluate the circumstances, under which WNV may establish in Germany as a whole or in particular favourable regions. In our current work, we formulate a dynamic model to describe the spreading process of West Nile virus in the presence of migratory birds. To investigate the possible role of migratory birds in the dissemination of WNV in Germany, we include the recurring presence of migratory birds through a mechanistic ordinary differential equations (ODE) model system. We also perform a sensitivity analysis of the infection curves. Seasonal impacts are also taken into consideration. As result, we present an analytical expression for the basic reproduction number R. We find that after introducing WNV into Germany, R will be above the critical value in many regions of the country. Furthermore, we observe that in the south of Germany, the disease reoccurs in the following season after the introduction. We include a potential distribution map associated with WNV cases in Germany to illustrate our findings in a spatial scale.
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http://dx.doi.org/10.1016/j.jtbi.2019.110117DOI Listing
March 2020

An Epidemiological and Economic Simulation Model to Evaluate Strategies for the Control of Bovine Virus Diarrhea in Germany.

Front Vet Sci 2019 19;6:406. Epub 2019 Nov 19.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Greifswald, Germany.

Models can be used to plan, evaluate, and improve programs for animal disease control. In Germany, a nationwide compulsory program to eradicate Bovine viral diarrhea (BVD) is in force since January 2011. As it is associated with substantial expenditures, the program is currently under revision. To provide the basis for a science-based decision on the future course of BVD control in Germany, we evaluated 13 scenarios (sc1-13) with respect to the chance of reaching freedom from disease and their economic implications for a period of 20 years (2011-2030). To simulate the impact of different control strategies on disease dynamics, a disease spread model was developed. To estimate the effects of a transient infection (TI) on animal level, a gross margin analysis was performed. To assess the value of cattle that died prematurely, a valuation model was used. Finally, an economic model was developed to perform a cost-benefit analysis and to compare each control scenario with a baseline setting with no BVD control. Costs comprised the expenditures for diagnostics, vaccination, preventive culling, and trade restrictions. Benefits were animal and production losses avoided by having control measures in place. The results show that reducing the PI prevalence on animal level to 0% is only feasible in scenarios that combine antigen or antibody testing with compulsory vaccination. All other scenarios, i.e., those based exclusively on a "test and cull" approach, including the current control program, will, according to the model, not achieve freedom of BVD by 2030. On the other hand, none of the scenarios that may lead to complete BVD eradication is economically attractive [benefit-cost ratio (BCR) between 0.64 and 0.94]. The average direct costs of BVD in Germany are estimated at 113 million Euros per year (34-402 million Euros), corresponding to 28.3 million Euros per million animals. Only the concepts of the former and the current national BVD control program ("ear tag testing and culling") may reduce the BVD prevalence to 0.01% with an acceptable BCR (net present value of 222 and 238 million Euros, respectively, with a BCR of 1.22 and 1.24).
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http://dx.doi.org/10.3389/fvets.2019.00406DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877714PMC
November 2019