Fine-scale mapping of vector habitats using very high resolution satellite imagery : a liver fluke case-study

The visualization of vector occurrence in space and time is an important aspect of studying vector-borne diseases. Detailed maps of possible vector habitats provide valuable information for the prediction of infection risk zones but are currently lacking for most parts of the world. Nonetheless, monitoring vector habitats from the finest scales up to farm level is of key importance to refine currently existing broad-scale infection risk models. Using Fasciola hepatica, a parasite liver fluke as a case in point, this study illustrates the potential of very high resolution (VHR) optical satellite imagery to efficiently and semi-automatically detect detailed vector habitats. A WorldView2 satellite image capable of <5m resolution was acquired in the spring of 2013 for the area around Bruges, Belgium, a region where dairy farms suffer from liver fluke infections transmitted by freshwater snails. The vector thrives in small water bodies (SWBs), such as ponds, ditches and other humid areas consisting of open water, aquatic vegetation and/or inundated grass. These water bodies can be as small as a few m(2) and are most often not present on existing land cover maps because of their small size. We present a classification procedure based on object-based image analysis (OBIA) that proved valuable to detect SWBs at a fine scale in an operational and semi-automated way. The classification results were compared to field and other reference data such as existing broad-scale maps and expert knowledge. Overall, the SWB detection accuracy reached up to 87%. The resulting fine-scale SWB map can be used as input for spatial distribution modelling of the liver fluke snail vector to enable development of improved infection risk mapping and management advice adapted to specific, local farm situations

Detection of Anaplasma phagocytophilum in horses from Germany by molecular and serological testing (2008–2021)

Background Equine granulocytic anaplasmosis (EGA) is a tick-borne disease caused by Anaplasma (A.) phagocytophilum. In Germany, this pathogen is transmitted primarily by Ixodes ricinus. There is limited knowledge about its prevalence in horses in Germany. The aim of this retrospective study was to analyze the results of serological and molecular testing for A. phagocytophilum in horses which were done in a commercial laboratory in Germany over fourteen years. Additionally, risk factors were evaluated, and hematological abnormalities were addressed in horses with positive PCR results. Methods This retrospective study examined results of direct (Polymerase chain reaction [PCR]) and indirect (immunofluorescence antibody test [IFAT]) detection methods for A. phagocytophilum in horses on samples provided by German veterinarians and processed by the commercial laboratory LABOKLIN from 2008 to 2021. In horses with positive test results, a Complete Blood Count (CBC) and Serum Amyloid A (SAA) were also analyzed where possible. Results In total, 1217/4834 horses tested positive (PCR: 190/1246 horses, 15.2%; IFAT: 1036/3849 horses, 26.9%). Seasonality and location, as classified by federal state, had a statistically significant impact on PCR results (P < 0.001 for both). In horses with positive PCR results, hematological abnormalities were detected in 112/118 horses (95%), with thrombocytopenia (86%) and anemia (52%) representing the most common findings. The remaining 6/118 horses (5%) showed no hematological abnormalities on CBC. SAA was measured in 35 horses with positive PCR results, which exclusively showed marked elevation. Conclusions The seasonality of A. phagocytophilum infections confirmed by PCR testing was consistent with known peaks in vector activity in Germany. The high rate of horses with positive PCR results when compared to dogs and cats may be due to a lack of ectoparasite prophylaxis. Infections with A. phagocytophilum should be considered as a differential diagnosis in horses with cytopenia on CBC and SAA elevation, especially in the summer and after any possible tick exposure

Molecular and Serological Detection of Anaplasma phagocytophilum in Dogs from Germany (2008–2020)

Anaplasma phagocytophilum is an obligate intracellular bacterium that causes granulocytic anaplasmosis in domestic animals, wildlife, and humans and is primarily transmitted by ticks of the Ixodes persulcatus complex. This retrospective study aims to determine the percentages of dogs that tested positive for A. phagocytophilum in Germany. It included the results of direct (polymerase chain reaction [PCR]) and indirect (immunofluorescence antibody test [IFAT], antibody-enzyme-linked immunosorbent assay [ELISA]) detection methods performed in the laboratory LABOKLIN on canine samples provided by German veterinarians from 2008 to 2020. Out of a total of 27,368 dogs tested by PCR, 1332 (4.9%) tested positive, while 24,720 (27.4%) of the 90,376 dogs tested by IFAT/ELISA had positive serology. High rates of positive PCR results were observed in months with known peaks in vector activity, showing that the dynamics of A. phagocytophilum infections in dogs in Germany are consistent with vector activity. In dogs with a positive PCR result, peaks in serology could be observed four weeks after initial testing. Male and senior dogs had higher rates of positive serology. A possible impact of environmental factors such as changes in climate should be investigated further. Overall, the upward trend in positive test results over the years indicates that canine granulocytic anaplasmosis will continue to become increasingly important for veterinary medicine

4E Interacting Protein as a Potential Novel Drug Target for Nucleoside Analogues in Trypanosoma brucei

Human African trypanosomiasis is a neglected parasitic disease for which the current treatment options are quite limited. Trypanosomes are not able to synthesize purines de novo and thus solely depend on purine salvage from the host environment. This characteristic makes players of the purine salvage pathway putative drug targets. The activity of known nucleoside analogues such as tubercidin and cordycepin led to the development of a series of C7-substituted nucleoside analogues. Here, we use RNA interference (RNAi) libraries to gain insight into the mode-of-action of these novel nucleoside analogues. Whole-genome RNAi screening revealed the involvement of adenosine kinase and 4E interacting protein into the mode-of-action of certain antitrypanosomal nucleoside analogues. Using RNAi lines and gene-deficient parasites, 4E interacting protein was found to be essential for parasite growth and infectivity in the vertebrate host. The essential nature of this gene product and involvement in the activity of certain nucleoside analogues indicates that it represents a potential novel drug target.</jats:p

Environmental changes and emergence of vector-borne diseases in Europe : improving risk surveillance and management

Vector-borne diseases are highly sensitive to environment and to environmental changes. Faced with their recrudescence and public concern about the possible consequences of climate and other environmental changes, the European commission has launched a large, integrative research project called EDEN (Emerging diseases in a changing European environment), involving 24 countries and 49 scientific partners from Europe, the Middle East and Africa. The goals of EDEN are to identify ecosystems exposed to a high risk of vector-borne disease emergence, and to explain and model the underlying epidemiological processes. For this purpose, an inter-disciplinary approach was adopted to ensure close interaction between biology, ecology, geography and modelling. The expected result is the development of new methods to help public-health agencies create disease-monitoring, early-warning and decision-making tools for the prevention and control of vector-borne diseases. After a general presentation of EDEN, we show results obtained with the Malaria sub-project, focusing on the Camargue ecosystem, to assess the risk of resurgence of disease previously eradicated from this region.Les maladies à transmission vectorielle sont par nature très sensibles à l'environnement et aux changements environnementaux. Devant leur recrudescence et les craintes liées aux conséquences de ces changements, la Commission européenne a financé un vaste projet de recherche intégrée: EDEN (Emerging diseases in a changing European environment). Ce projet concerne 24 pays et 49 partenaires d'Europe, du Moyen Orient et d'Afrique. Il vise à identifier les écosystèmes soumis à un risque élevé d'émergence de ces maladies, à expliquer et modéliser les processus épidémiologiques en cause. Pour atteindre cet objectif, une démarche inter-disciplinaire a été entreprise permettant une interaction optimale entre biologie, écologie, géographie et modélisation. Le résultat attendu est la mise au point de méthodes utilisables par les agences de santé publique pour développer des outils de surveillance, d'alerte précoce et d'aide à la décision pour la prévention et le contrôle des maladies à transmission vectorielle. Après une présentation générale du projet, nous exposons les résultats obtenus dans le domaine du paludisme, plus particulièrement dans l'écosystème de Camargue, pour évaluer le risque de résurgence de cette maladie éradiquée naguère de cette région