Beyond mortality: Sterility as a neglected component of parasite virulence

International audienceVirulence is generally defined as the reduction in host fitness following infection by a parasite (see Box 1 for glossary) [1]. In general, parasite exploitation of host resources may reduce host survival (mortality virulence), decrease host fecundity (sterility virulence), or even have sub-lethal effects that disturb the way individuals interact within a community (morbidity) [2,3]. In fact, the virulence of many parasites involves a combination of these various effects (Box 2). In practice, however, virulence is most often defined as disease-induced mortality [1, 4-6]. This is especially true in the theoretical literature, where the evolution of sterility virulence, morbidity, and mixed strategies of host exploitation have received relatively little attention. While the focus on mortality effects has allowed for easy comparison between models and, thus, rapid advancement of the field, we ask whether these theoretical simplifications have led us to inadvertently minimize the evolutionary importance of host sterilization and secondary virulence effects. As explicit theoretical work on morbidity is currently lacking (but see [7]), our aim in this Opinion piece is to discuss what is understood about sterility virulence evolution, its adaptive potential, and the implications for parasites that utilize a combination of host survival and reproductive resources

Quantifying the epidemic spread of Ebola virus (EBOV) in Sierra Leone using phylodynamics

International audienceMeasuring epidemic parameters early in an outbreak is essential to inform control efforts. Using the viral genome sequence and collection date from 74 infections in the 2014 Ebola virus outbreak in Sierra Leone, we estimate key epidemiological parameters such as infectious period duration (approximately 71 hours) and date of the first case in Sierra Leone (approximately April 25(th)). We also estimate the effective reproduction number, Re, (approximately 1.26), which is the number of secondary infections effectively caused by an infected individual and accounts for public health control measures. This study illustrates that phylodynamics methods, applied during the initial phase of an outbreak on fewer and more easily attainable data, can yield similar estimates to count-based epidemiological studies

Sympatry and interference of divergent Microbotryum pathogen species

The impact of infectious diseases in natural ecosystems is strongly influenced by the degree of pathogen specialization and by the local assemblies of potential host species. This study investigated anther-smut disease, caused by fungi in the genus Microbotryum, among natural populations of plants in the Caryophyllaceae. A broad geographic survey focused on sites of the disease on multiple host species in sympatry. Analysis of molecular identities for the pathogens revealed that sympatric disease was most often due to co-occurrence of distinct, host-specific anther-smut fungi, rather than localized cross-species disease transmission. Flowers from sympatric populations showed that the Microbotryum spores were frequently moved between host species. Experimental inoculations to simulate cross-species exposure to the pathogens in these plant communities showed that the anther-smut pathogen was less able to cause disease on its regular host when following exposure of the plants to incompatible pathogens from another host species. These results indicate that multi-host/multi-pathogen communities are common in this system and they involve a previously hidden mechanism of interference between Microbotryum fungi, which likely affects both pathogen and host distributions

Might Interspecific Interactions between Pathogens Drive Host Evolution? The Case of Plasmodium Species and Duffy-Negativity in Human Populations

International audienceMalarial infections have long been recognized as a driver of human evolution, as demonstrated by the influence of Plasmodium falciparum on sickle-cell anemia persistence. Duffy-negativity is another blood disorder thought to have been selected because it confers nearly complete resistance against Plasmodium vivax infection. Recent evidence suggests that the benefits of being Duffy-negative cannot be expected to play a strong selective pressure on humans, whereas its costs cannot be considered as negligible. Here, we suggest that the cross-talk between P. falciparum and P. vivax in coinfected children could represent the most parsimonious explanation of the frequency of Duffy-negativity. We discuss how this new hypothesis could be tested and call for a reconsideration of the evolution of the Duffy-negative group

The macroecology of cancer incidences in humans is associated with large-scale assemblages of endemic infections.

8 pagesInternational audienceIt is now well supported that 20% of human cancers have an infectious causation (i.e., oncogenic agents). Accumulating evidence suggests that aside from this direct role, other infectious agents may also indirectly affect cancer epidemiology through interactions with the oncogenic agents within the wider infection community. Here, we address this hypothesis via analysis of large-scale global data to identify associations between human cancer incidence and assemblages of neglected infectious agents. We focus on a gradient of three widely-distributed cancers with an infectious cause: bladder (~2% of recorded cancer cases are due to Shistosoma haematobium), liver (~60% consecutive to Hepatitis B and C infection) and stomach (Helicobacter pylori is associated with ~70% of cases). We analyzed countries in tropical and temperate regions separately, and controlled for many confounding social and economic variables. First, we found that particular assemblages of bacteria are associated with bladder cancer incidences. Second, we observed a specific and robust association between helminths and liver cancer incidences in both biomes. Third, we show that certain assemblages of viruses may facilitate stomach cancer in tropical area, while others protect against its development in temperate countries. Finally, we discuss the implications of our results in terms of cancer prevention and highlight the necessity to consider neglected diseases, especially in tropics, to adapt public health strategies against infectious diseases and cancer

Co-occurrence among three divergent plant-castrating fungi in the same Silene host species

BGPI : équipe 5International audienceThe competitive exclusion principle postulates that different species can only coexist in sympatry if they occupy distinct ecological niches. The goal of this study was to understand the geographical distribution of three species of Microbotryum anther-smut fungi that are distantly related but infect the same host plants, the sister species Silene vulgaris and S. uniflora, in Western Europe. We used microsatellite markers to investigate pathogen distribution in relation to host specialization and ecological factors. Microbotryum violaceo-irregulare was only found on S. vulgaris at high elevations in the Alps. Microbotryum lagerheimii could be subdivided into two genetically differentiated clusters, one on S. uniflora in the UK and the second on S. vulgaris in the Alps and Pyrenees. The most abundant pathogen species, M. sile-nes-inflatae, could be subdivided into four genetic clusters, co-occurring in the Alps, the UK and the Pyrenees, and was found on both S. vulgaris and S. uniflora. All three fungal species had high levels of homozygosity, in agreement with the selfing mating system generally observed in anther-smut fungi. The three pathogen species and genetic clusters had large range overlaps, but occurred at sites with different elevations , temperatures and precipitation levels. The three Microbotryum species thus do not appear to be maintained by host specialization or geographic allopatry, but instead may occupy different ecological niches in terms of environmental conditions

Effect of Filler Therapy on Psychosocial Distress in Facial Paralysis: Patients with Major Asymmetry Derive Greater Benefit

Background: Facial filler is an effective nonsurgical treatment option for improving facial symmetry in patients with facial paralysis (FP).Objective: To compare the effects of filler among patients with FP that is self-perceived as major or minor asymmetry, by measuring psychosocial distress.Methods: In this prospective cohort study of patients with FP undergoing filler at a tertiary academic center, patients were classified as having minor or major self-perceived asymmetry using a visual analog scale (VAS). FACE-Q Appearance-Related Psychosocial Distress was administered before and after filler. Descriptive statistics and a random-effects generalized linear model assessed the relationship between perceived facial asymmetry and change in psychosocial distress.Results: A total of 28 patients participated. Twenty-five (89%) patients were female with median age of 54 (interquartile range [IQR]: 49-66). Median VAS score was 2 (IQR: 1-3.5, 0 = completely asymmetric, 10 = no asymmetry). Psychosocial distress improved in all patients after filler. In multivariable modeling, patients with major asymmetry experienced 2.45 (confidence interval: 0.46-4.44, p = 0.016) points more improvement in psychosocial distress than patients with minor asymmetry. Age, gender, and FP duration were not associated with change in psychosocial distress.Conclusion: Facial filler treatment was seen to improve psychosocial distress in patients with FP, especially by those with more self-perceived deficit

Cretaceous environmental changes led to high extinction rates in a hyperdiverse beetle family: Cretaceous environmental changes led to high extinction rates in a hyperdiverse beetle family

Times Cited: 00Background: As attested by the fossil record, Cretaceous environmental changes have significantly impacted the diversification dynamics of several groups of organisms. A major biome turnover that occurred during this period was the rise of angiosperms starting ca. 125 million years ago. Though there is evidence that the latter promoted the diversification of phytophagous insects, the response of other insect groups to Cretaceous environmental changes is still largely unknown. To gain novel insights on this issue, we assess the diversification dynamics of a hyperdiverse family of detritivorous beetles (Tenebrionidae) using molecular dating and diversification analyses. Results: Age estimates reveal an origin after the Triassic-Jurassic mass extinction (older than previously thought), followed by the diversification of major lineages during Pangaean and Gondwanan breakups. Dating analyses indicate that arid-adapted species diversified early, while most of the lineages that are adapted to more humid conditions diversified much later. Contrary to other insect groups, we found no support for a positive shift in diversification rates during the Cretaceous; instead there is evidence for an 8.5-fold increase in extinction rates that was not compensated by a joint increase in speciation rates. Conclusions: We hypothesize that this pattern is better explained by the concomitant reduction of arid environments starting in the mid-Cretaceous, which likely negatively impacted the diversification of arid-adapted species that were predominant at that time

High prevalence and diversity of hepatitis B and hepatitis delta virus in Gabon

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