Detection of trypanosomes in small ruminants and pigs in western Kenya: important reservoirs in the epidemiology of sleeping sickness?

Background

Trypanosomosis is a major impediment to livestock farming in sub-Saharan Africa and limits the full potential of agricultural development in the 36 countries where it is endemic. In man, sleeping sickness is fatal if untreated and causes severe morbidity. This study was undertaken in western Kenya, an area that is endemic for both human and livestock trypanosomosis. While trypanosomosis in livestock is present at high levels of endemicity, sleeping sickness occurs at low levels over long periods, interspersed with epidemics, underscoring the complexity of the disease epidemiology. In this study, we sought to investigate the prevalence of trypanosomes in small ruminants and pigs, and the potential of these livestock as reservoirs of potentially human-infective trypanosomes. The study was undertaken in 5 villages, to address two key questions: i) are small ruminants and pigs important in the transmission dynamics of trypanosomosis? and ii), do they harbour potentially human infective trypanosomes? Answers to these questions are important in developing strategies for the control of both livestock and human trypanosomosis.

Results

Eighty-six animals, representing 21.3% of the 402 sampled in the 5 villages, were detected as positive by PCR using a panel of primers that identify trypanosomes to the level of the species and sub-species. These were categorised as 23 (5.7%) infections of T. vivax, 22 (5.5%) of T. simiae, 21 (5.2%) of the T. congolense clade and 20 (5.0%) of T. brucei ssp. The sheep was more susceptible to trypanosome infection as compared to goats and pigs. The 20 T. brucei positive samples were evaluated by PCR for the presence of the Serum Resistance Associated (SRA) gene, which has been linked to human infectivity in T. b. rhodesiense. Three samples (one pig, one sheep and one goat) were found to have the SRA gene. These results suggest that sheep, goats and pigs, which are kept alongside cattle, may harbour human-infective trypanosomes.

Conclusion

We conclude that all livestock kept in this T. b. rhodesiense endemic area acquire natural infections of trypanosomes, and are therefore important in the transmission cycle. Sheep, goats and pigs harbour trypanosomes that are potentially infective to man. Hence, the control of trypanosomosis in these livestock is essential to the success of any strategy to control the disease in man and livestock.

     

Do phytoseiid mites select the best prey species in terms of reproductive success?

Optimal foraging theory predicts that predators prefer those prey species that are most rewarding in terms of reproductive success, which is dependent on prey quality and prey availability. To investigate which selection pressures may have moulded prey preference in an acarine system consisting of two prey species and three predator species, we tested whether prey preference of the predators is matched by the associated reproductive success.The predators involved areAmblyseius finlandicus (Oudemans),Am. potentillae (Garman) andTyphlodromus pyri Scheuten. The prey species are the apple rust mite (Aculus schlechtendali (Nalepa)) and the fruit-tree red spider mite (Panonychus ulmi (Koch)).Reproductive success was assessed in terms of intrinsic rate of increase and for one predator also in terms of diapause induction. All three predator species reached highest reproductive success on the same prey species: apple rust mite. This was most pronounced for the predatorAm. finlandicus, because its larval stage suffered severe mortality when feeding onP. ulmi.An independent study on prey preference of the three predator species (Dicke et al., 1988) revealed thatAm. finlandicus prefersAc. schlechtendali toP. ulmi, whereas the other two predator species have the reverse preference.Thus, on the basis of current data, prey preference ofAm. finlandicus can be understood in terms of reproductive success. However, this is not so for prey preference ofT. pyri andAm. potentillae. Investigations needed for a better understanding of prey preference of the last-named two predator species are discussed.     

The plot thickens: does low density affect visitation and reproductive success in a perennial herb, and are these effects altered in the presence of a co-flowering species?

Plants may experience reduced reproductive success at low densities, due to lower numbers of pollinator visits or reduced visit quality. Co-occurring plant species that share pollinators have the potential to facilitate pollination by either increasing numbers of pollinator visits or increasing the quality of visits, but also have the potential to reduce plant reproductive success through competition for pollination. I used a field experiment with a common distylous perennial (Piriqueta caroliniana) in the presence and absence of a co-flowering species (Coreopsis leavenworthii) in plots with one of four different distances between conspecific plants. I found strong negative effects of increasing interplant distance (related to conspecific density) on several components of P. caroliniana reproductive success: pollinator visits to plants per plot visit, visits received by individual plants, conspecific pollen grains on stigmas, outcross pollen grains on stigmas, and probability of fruit production. Although P. caroliniana and C. leavenworthii share pollinators, the co-flowering species did not affect visitation, pollen receipt or reproductive effort in P. caroliniana. Pollinators moved very infrequently between species in this experiment, so floral constancy might explain the lack of effect of the co-flowering species on P. caroliniana reproductive success at low densities. In co-occurring self-incompatible plants with floral rewards, reproductive success at low density may depend more on conspecific densities than on the presence of other species.     

Why are taeniae,haustra, and semilunar folds differentiated in the gastrointestinal tract of mammals,including man?

When a small change, either contraction or dilation, of the surface area of a digestive tube coincides with a considerable change in internal volume, this can be considered an effective influence of surface on volume. This study discusses the effects of anatomical differences between those types of digestive tracts where the longitudinal musculature is reduced to small bands, the taeniae, and those where such differentiations are not found. With the help of a geometric model the efficiency of transport (eta = net volume expelled aborally / volume of the tube) from haustra in tubes with two, three, four, and six taeniae was determined. It could be shown that efficiency of transport from haustra decreases when the number of taeniae increases. The second model applies the program "Surface Evolver" (author K.A. Brakke). The program is applied to investigate the relationships between changes in surface area of tubes with different numbers of taeniae (0, 2, 3, 4, and 6) and the respective changes of the internal volumes of tubes. Both haustra formation and formation of semilunar folds between haustra are considered. Tubes with two or three taeniae reduce their internal volume more efficiently than all others, namely, with a relatively small reduction of the surface area and contraction of the Tunica muscularis at a relatively low rate. In addition to chemical and mechanical decomposition of digesta the gastrointestinal tube has three tasks: propagation, storage, and retention of digesta. A tube without taeniae, i.e., with a complete longitudinal muscular layer, propagates contents with peristaltic movements. Storage can take place in areas of the tract with a dilated cross-section. Finally, folds can retain digesta. In many sections of the gastrointestinal tract folds are differentiated as permanent structures. However, folds formed with relatively little contraction of the musculature, i.e., little change in the surface area, represent an effective means of retention and thus of flow regulation. Tubes with taeniae and semilunar folds are adaptations for this effective type of regulation of digesta transit through the tract.     

Why is epigenetics important in understanding the pathogenesis of inflammatory musculoskeletal diseases?

In its widest sense, the term epigenetics describes a range of mechanisms in genome function that do not solely result from the DNA sequence itself. These mechanisms comprise DNA and chromatin modifications and their associated systems, as well as the noncoding RNA machinery. The epigenetic apparatus is essential for controlling normal development and homeostasis, and also provides a means for the organism to integrate and react upon environmental cues. A multitude of functional studies as well as systematic genome-wide mapping of epigenetic marks and chromatin modifiers reveal the importance of epigenomic mechanisms in human pathologies, including inflammatory conditions and musculoskeletal disease such as rheumatoid arthritis. Collectively, these studies pave the way to identify possible novel therapeutic intervention points and to investigate the utility of drugs that interfere with epigenetic signalling not only in cancer, but possibly also in inflammatory and autoimmune diseases.     

When do we eat? Ingestive behavior,survival, and reproductive success

The neuroendocrinology of ingestive behavior is a topic central to human health, particularly in light of the prevalence of obesity, eating disorders, and diabetes. The study of food intake in laboratory rats and mice has yielded some useful hypotheses, but there are still many gaps in our knowledge. Ingestive behavior is more complex than the consummatory act of eating, and decisions about when and how much to eat usually take place in the context of potential mating partners, competitors, predators, and environmental fluctuations that are not present in the laboratory. We emphasize appetitive behaviors, actions that bring animals in contact with a goal object, precede consummatory behaviors, and provide a window into motivation. Appetitive ingestive behaviors are under the control of neural circuits and neuropeptide systems that control appetitive sex behaviors and differ from those that control consummatory ingestive behaviors. Decreases in the availability of oxidizable metabolic fuels enhance the stimulatory effects of peripheral hormones on appetitive ingestive behavior and the inhibitory effects on appetitive sex behavior, putting a new twist on the notion of leptin, insulin, and ghrelin “resistance.” The ratio of hormone concentrations to the availability of oxidizable metabolic fuels may generate a critical signal that schedules conflicting behaviors, e.g., mate searching vs. foraging, food hoarding vs. courtship, and fat accumulation vs. parental care. In species representing every vertebrate taxa and even in some invertebrates, many putative “satiety” or “hunger” hormones function to schedule ingestive behavior in order to optimize reproductive success in environments where energy availability fluctuates.     

Why are there about 5000 species of phytoplankton in the sea?

The relative abundances of phytoplankton taxa conform approximatelyto a finite geometric series in which there are 20–25species per decade of ranked abundance. Such series can contain160–400 species between the commonest (10²²–10²⁶cells) and the rarest (10¹⁰–10¹⁴ cells). Thus, between12 and 31 such series are needed to explain the observed diversity,5x10³ species, of marine phytoplankton. The number of seriesis similar to the number (20–25) of upper-ocean watermasses defined by dilution time scale of order 10¹–10²years. Interpretations of this coincidence are discussed.     

Why are most EU pigs tail docked? Economic and ethical analysis of four pig housing and management scenarios in the light of EU legislation and animal welfare outcomes

To limit tail biting incidence, most pig producers in Europe tail dock their piglets. This is despite EU Council Directive 2008/120/EC banning routine tail docking and allowing it only as a last resort. The paper aims to understand what it takes to fulfil the intentions of the Directive by examining economic results of four management and housing scenarios, and by discussing their consequences for animal welfare in the light of legal and ethical considerations. The four scenarios compared are: ‘Standard Docked’, a conventional housing scenario with tail docking meeting the recommendations for Danish production (0.7 m²/pig); ‘Standard Undocked’, which is the same as ‘Standard Docked’ but with no tail docking, ‘Efficient Undocked’ and ‘Enhanced Undocked’, which have increased solid floor area (0.9 and 1.0 m²/pig, respectively) provision of loose manipulable materials (100 and 200 g/straw per pig per day) and no tail docking. A decision tree model based on data from Danish and Finnish pig production suggests that Standard Docked provides the highest economic gross margin with the least tail biting. Given our assumptions, Enhanced Undocked is the least economic, although Efficient Undocked is better economically and both result in a lower incidence of tail biting than Standard Undocked but higher than Standard Docked. For a pig, being bitten is worse for welfare (repeated pain, risk of infections) than being docked, but to compare welfare consequences at a farm level means considering the number of affected pigs. Because of the high levels of biting in Standard Undocked, it has on average inferior welfare to Standard Docked, whereas the comparison of Standard Docked and Enhanced (or Efficient) Undocked is more difficult. In Enhanced (or Efficient) Undocked, more pigs than in Standard Docked suffer from being tail bitten, whereas all the pigs avoid the acute pain of docking endured by the pigs in Standard Docked. We illustrate and discuss this ethical balance using numbers derived from the above-mentioned data. We discuss our results in the light of the EU Directive and its adoption and enforcement by Member States. Widespread use of tail docking seems to be accepted, mainly because the alternative steps that producers are required to take before resorting to it are not specified in detail. By tail docking, producers are acting in their own best interests. We suggest that for the practice of tail docking to be terminated in a way that benefits animal welfare, changes in the way pigs are housed and managed may first be required.     

Can the pollination biology and floral ontogeny of the threatened Acacia carneorum explain its lack of reproductive success?

Many Acacia species in arid areas of eastern Australia have been severely impacted by grazing, habitat degradation and fragmentation. These factors have been at the core of proposed explanations for the reproductive failure and numerical decline of Acacia carneorum and other threatened acacias. Paradoxically, the sympatric Acacia ligulata is thriving and highly fecund. Although these species have superficially similar floral displays, differences in sexual reproductive success may reflect interactions between flower and inflorescence ontogeny and pollinator assemblages. We compared the floral biology and flower visitor assemblages of A. carneorum and A. ligulata at four sites per species. Both species displayed similar floral ontogeny and synchronicity of display, with inflorescences simultaneously hermaphroditic for 4–5 days. However, A. ligulata displayed a higher density of flowers than A. carneorum and, while both species received a range of flower visitors, A. ligulata was visited by relatively few species and was serviced primarily by the non-native honeybee Apis mellifera, which typically made many within-plant movements during foraging bouts. In contrast, A. carneorum was visited by a diverse suite of native insects that carried little pollen and made fewer within plant movements. On average, Apis mellifera carried 98.4 % A. ligulata pollen, whereas the native insect visitors of A. carneorum carried only 45 % A. carneorum pollen. Differing floral ontogeny or lack of native pollinators does not explain the reproductive failure of A. carneorum. The success of A. ligulata may reflect pollination services provided by A. mellifera and interactions with plant mating systems.     

Egg-size variation and reproductive success in the Herring Gull Lams argentatus: adaptive or constrained size of the last egg?

Herring Gull Larus argentatus eggs from a study colony in the Baltic showed a slight but significant variation in egg size within the laying sequence. Last-laid eggs were only about 5% smaller by volume than first eggs. There was no significant difference in dry yolk weight or dry albumen weight, although possible differences were evident. The chicks had nearly equal hatching weights and equally long tarsi. There was no differential mortality in the third chick in the study colony, and there were no indications of egg-size-mediated mortality. The birds in the colony produced an average of 1.45 fledglings per pair. Compared with several other studied colonies, the difference in egg size within a clutch was low, and a comparison of colonies from northwestern Europe suggests that variance within the clutch is negatively correlated with fledging success, so that a large difference in size between first and last eggs is associated with low fledging success. We suggest that the size of the last egg in the clutch reflects the feeding potential in the environment and is mainly a nonadaptive response to poor feeding conditions during laying.     

Fusion of vacuoles--where are the membranes, and where are the holes?

In the February 8th issue of Cell, Wang et al. report the surprising finding that vacuolar fusion occurs at the periphery of the contact area of the vacuoles and not by the expansion of a central fusion pore. During fusion, a disk of boundary membrane is excised and left behind within the fused vacuoles.     

Cultural and reproductive success and the causes of war: A Yanomamö perspective

Inter-group competition including warfare is posited to be a key force in human evolution (Alexander, 1990; Choi & Bowles, 2007; Wrangham, 1999). Chagnon's research on the Yanomamö is seminal to understanding warfare in the types of societies characteristic of human evolutionary history. Chagnon's empirical analyses of the hypothesis that competition for status or cultural success is linked to reproduction (Irons, 1979) and warfare attracted considerable controversy. Potential causal factors include “blood revenge”, mate competition, resource shortages or inequality, and peace-making institutions (Boehm, 1984; Keeley's (1997); Meggitt, 1977; Wiessner and Pupu, 2012; Wrangham et al., 2006). Here we highlight Chagnon's contributions to the study of human warfare.     

Innovation in mental health services: what are the key components of success?

Background

Service development innovation in health technology and practice is viewed as a pressing need within the field of mental health yet is relatively poorly understood. Macro-level theories have been criticised for their limited explanatory power and they may not be appropriate for understanding local and fine-grained uncertainties of services and barriers to the sustainability of change. This study aimed to identify contextual influences inhibiting or promoting the acceptance and integration of innovations in mental health services in both National Health Service (NHS) and community settings.

Methods

A comparative study using qualitative and case study data collection methods, including semi-structured interviews with key stakeholders and follow-up telephone interviews over a one-year period. The analysis was informed by learning organisation theory. Drawn from 11 mental health innovation projects within community, voluntary and NHS settings, 65 participants were recruited including service users, commissioners, health and non-health professionals, managers, and caregivers. The methods deployed in this evaluation focused on process-outcome links within and between the 11 projects.

Results

Key barriers to innovation included resistance from corporate departments and middle management, complexity of the innovation, and the availability and access to resources on a prospective basis within the host organisation. The results informed the construction of a proposed model of innovation implementation within mental health services. The main components of which are context, process, and outcomes.

Conclusions

The study produced a model of conducive and impeding factors drawn from the composite picture of 11 innovative mental health projects, and this is discussed in light of relevant literature. The model provides a rich agenda to consider for services wanting to innovate or adopt innovations from elsewhere. The evaluation suggested the importance of studying innovation with a focus on context, process, and outcomes.

     

Why is the number of pregnancies among teenagers decreasing?

The issue of pregnancy among adolescent women has received considerable attention from the media. Contrary to common belief, both the numbers and the rates of such pregnancies, even when data on abortion are included, have been declining. Patterns of contraception may account for some of the decrease; however, more study is required. In the past, unmarried teenagers who became pregnant either got married or put the baby up for adoption. Now they can either have an abortion or keep the baby. Solutions to the problems of pregnancy among teenagers must therefore be addressed to these altered social consequences rather than to misleading comments about "epidemics", with their suggestion of increased rates of pregnancy.     

NMπ 2.0: Software update to minimize the risk of false positives among determinants of reproductive success

In plant populations, parentage analysis helps understand factors shaping individual reproductive success. However, estimating reproductive success determinants based on parentage counts requires decoupling the effects of individual fecundity and propagule dispersal. The neighbourhood model implemented in the NMπ software provides a standard solution for this problem based on the fixed-effects regression-like approach. Nonetheless, it has been recently shown that the method is prone to false discoveries when important fecundity determinants are omitted. To account for the unexplained variance in fecundity, the Bayesian approach was developed based on the new model (the hierarchical neighbourhood model; HNM). Here, I present the NMπ software update that allows the HNM approach to be used in the framework of a friendly interface. More importantly, the HNM approach is now made available for both dispersed (seedlings) and nondispersed (seeds with known mothers) progeny data. The Bayesian approach, among others, selects significant fecundity determinants, estimates the proportion of variance in reproductive potential explained by selected determinants (R²), and provides individual female and male fecundity values. Although the software was designed to handle microsatellite marker data, a solution is proposed for large sets of single nucleotide polymorphisms. The program can be run on Windows (using either a terminal or a graphical interface) as well as (using a terminal) on Linux, or macOS platforms. In any case, NMπ can utilize multicore processors to speed up the analysis. The updated package containing the code, the executable file, the user manual, and example data is available at https://www.ukw.edu.pl/pracownicy/plik/igor_chybicki/3694/ .     

Why are there so few fish in the sea?

The most dramatic gradient in global biodiversity is between marine and terrestrial environments. Terrestrial environments contain approximately 75-85% of all estimated species, but occupy only 30 per cent of the Earth's surface (and only approx. 1-10% by volume), whereas marine environments occupy a larger area and volume, but have a smaller fraction of Earth's estimated diversity. Many hypotheses have been proposed to explain this disparity, but there have been few large-scale quantitative tests. Here, we analyse patterns of diversity in actinopterygian (ray-finned) fishes, the most species-rich clade of marine vertebrates, containing 96 per cent of fish species. Despite the much greater area and productivity of marine environments, actinopterygian richness is similar in freshwater and marine habitats (15 150 versus 14 740 species). Net diversification rates (speciation-extinction) are similar in predominantly freshwater and saltwater clades. Both habitats are dominated by two hyperdiverse but relatively recent clades (Ostariophysi and Percomorpha). Remarkably, trait reconstructions (for both living and fossil taxa) suggest that all extant marine actinopterygians were derived from a freshwater ancestor, indicating a role for ancient extinction in explaining low marine richness. Finally, by analysing an entirely aquatic group, we are able to better sort among potential hypotheses for explaining the paradoxically low diversity of marine environments.     

Why are there four letters in the genetic alphabet?

We list, without thinking, the four base types that make up DNA as adenine, guanine, cytosine and thymine. But why are there four? This question is now all the more relevant as organic chemists have synthesized new base pairs that can be incorporated into nucleic acids. Here, I argue that there are theoretical, experimental and computational reasons to believe that having four base types is a frozen relic from the RNA world, when RNA was genetic as well as enzymatic material.