Prävalenz von sexuell und durch Blut übertragenen Infektionen und Tuberkulose bei Menschen in Wohnungs­losigkeit in Berlin – Erste Ergebnisse der Pilotstudie POINT

Das RKI hat in Kooperation mit Fixpunkt e. V. und BeSog Berliner Sozialprojekte gGmbH die Querschnittsstudie POINT initiiert, um valide Aussagen zur Prävalenz von sexuell und durch Blut übertragbaren Infektionen und Tuberkulose bei wohnungslosen Personen treffen zu können. Mit den gewonnenen Daten sollen Präventions- und Versorgungsangebote ausgestaltet sowie internationale Strategien zur Eliminierung der untersuchten Infektionen unterstützt werdenPeer Reviewe

Prävalenz von sexuell und durch Blut übertragenen Infektionen und Tuberkulose bei Menschen in Wohnungs­losigkeit in Berlin – Erste Ergebnisse der Pilotstudie POINT

Das RKI hat in Kooperation mit Fixpunkt e. V. und BeSog Berliner Sozialprojekte gGmbH die Querschnittsstudie POINT initiiert, um valide Aussagen zur Prävalenz von sexuell und durch Blut übertragbaren Infektionen und Tuberkulose bei wohnungslosen Personen treffen zu können. Mit den gewonnenen Daten sollen Präventions- und Versorgungsangebote ausgestaltet sowie internationale Strategien zur Eliminierung der untersuchten Infektionen unterstützt werdenPeer Reviewe

Infection success of Echinoparyphium aconiatum (Trematoda) in its snail host under high temperature: role of host resistance

Background: Extreme weather events such as summer heat waves become more frequent owing to global climate change and are predicted to alter disease dynamics. This is because high temperatures can reduce host immune function. Predicting the impact of climate change on host-parasite interactions is, however, difficult as temperature may also affect parasite infective stages and other host characteristics determining the outcome of interaction. Methods: Two experiments were conducted to investigate these phenomena in a Lymnaea stagnalis–Echinoparyphium aconiatum (Trematoda) interaction. In the first experiment, the effects of exposure of snails to experimental heat waves [maintenance at 25°C vs. 15°C (control)] with different durations (3 days, 7 days) on the infection success of parasite cercariae was examined. In the second experiment, the infection success was examined under similar conditions, while controlling for the possible temperature effects on cercariae and at least partly also for host physiological changes that take place rapidly compared to alterations in immune function (exposure to cercariae at intermediate 20°C). Results: In the first experiment, increased infection success at 25°C was found independently of the duration of the heat wave. In the second experiment, increased infection success was found only in snails maintained at 25°C for 7 days, a treatment in which snail immune defence is known to be impaired. Conclusions: These results suggest that the effects of host resistance in determining overall parasite infection success can be overridden by effects of temperature on parasite transmission stages and/or alterations in other host traits than immune defence.peerReviewe

Data from: Quality attracts parasites: host condition-dependent chemo-orientation of trematode larvae

1. Environmental factors impairing physiological condition of organisms are assumed to predispose them to parasite infections. This is because host immune function is typically condition-dependent. However, poor physiological condition has been reported to reduce host susceptibility to parasites in various systems. 2. We examined whether such an effect can be due to altered exposure of hosts to active parasite transmission stages by investigating chemo-orientation of free-swimming cercariae larvae of a parasite Echinoparyphium aconiatum towards its snail host Lymnaea stagnalis. 3. We used both long-term and short-term feeding treatments to manipulate the body condition and physiological traits related to food processing in experimental (i.e. target) snails and measured the preference of cercariae towards snail-conditioned water (SCW) over clean water. 4. We found that chemo-orientation of cercariae depended on the nutritional status of target snails. High physiological condition (long-term feeding) attracted parasites, but cercariae did not show preference towards SCW from individuals in poor physiological condition (long-term starvation). Food processing (short-term feeding treatments) did not affect chemo-orientation. 5. Our results suggest that host condition-dependent chemo-orientation of parasite larvae is a likely mechanism explaining the reduced susceptibility of snails to infection due to food limitation in our study system. In general, the use of condition-dependent host cues can be highly beneficial for parasites as it increases their transmission to high-quality hosts. Furthermore, evolving counter adaptations to such a transmission strategy can be very difficult for hosts

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Data from: Potential for adaptation to climate change: family-level variation in fitness-related traits and their responses to heat waves in a snail population

Background: On-going global climate change poses a serious threat for natural populations unless they are able to evolutionarily adapt to changing environmental conditions (e.g. increasing average temperatures, occurrence of extreme weather events). A prerequisite for evolutionary change is within-population heritable genetic variation in traits subject to selection. In relation to climate change, mainly phenological traits as well as heat and desiccation resistance have been examined for such variation. Therefore, it is important to investigate adaptive potential under climate change conditions across a broader range of traits. This is especially true for life-history traits and defences against natural enemies (e.g. parasites) since they influence organisms’ fitness both directly and through species interactions. We examined the adaptive potential of fitness-related traits and their responses to heat waves in a population of a freshwater snail, Lymnaea stagnalis. We estimated family-level variation and covariation in life history (size, reproduction) and constitutive immune defence traits [haemocyte concentration, phenoloxidase (PO)-like activity, antibacterial activity of haemolymph] in snails experimentally exposed to typical (15 °C) and heat wave (25 °C) temperatures. We also assessed variation in the reaction norms of these traits between the treatments. Results: We found that at the heat wave temperature, snails were larger and reproduced more, while their immune defence was reduced. Snails showed high family-level variation in all examined traits within both temperature treatments. The only negative genetic correlation (between reproduction and antibacterial activity) appeared at the high temperature. However, we found no family-level variation in the responses of most examined traits to the experimental heat wave (i.e. largely parallel reaction norms between the treatments). Only the reduction of PO-like activity when exposed to the high temperature showed family-level variation, suggesting that the cost of heat waves may be lower for some families and could evolve under selection. Conclusion: Our results suggest that there is genetic potential for adaptation within both thermal environments and that trait evolution may not be strongly affected by trade-offs between them. However, rare differences in thermal reaction norms across families indicate limited evolutionary potential in the responses of snails to changing temperatures during extreme weather events

Inbreeding does not alter the response to an experimental heat wave in a freshwater snail

Global climate change affects natural populations of many species by increasing the average temperature and the frequency of extreme weather events (e.g. summer heat waves). The ability of organisms to cope with these environmental changes can, however, depend on their genetic properties. For instance, genetic load owing to inbreeding could alter organisms’ responses to climate change-mediated environmental changes but such effects are often overlooked. We investigated the effects of an experimental heat wave (25°C versus 15°C) on life history (reproduction, size) and constitutive immune defence traits (phenoloxidase-like and antibacterial activity of haemolymph) in relation to inbreeding by manipulating the mating type (outcrossing, self-fertilization) in two populations of a hermaphroditic freshwater snail, Lymnaea stagnalis. High temperature increased reproduction and size of snails but impaired their immune function. In one of the two study populations, inbreeding reduced reproductive output of snails indicating inbreeding depression. Furthermore, this effect did not depend on the temperature snails were exposed to. Our results suggest that L. stagnalis snails can be negatively affected by inbreeding but it may not alter their responses to heat waves.peerReviewe

Data

Data is saved as a tab delimited text file (data.txt). Data file has the following columns: 1) temp - temperature treatment (15C, 25C); 2) fam - snail family (15 families); 3) block - block of the experiment (6 blocks); 4) size - shell length (mm); 5) rep - reproduction during the experiment (0 = no, 1 = yes); 6) eggs - number of produced eggs; 7) haemo - haemocyte concentration of haemolymph (cells/ul); 8) A - antibacterial activity of haemolymph; 9) PO - PO-like activity of haemolymph