scholarly journals How to maintain a high virulence: evolution of a killer in hosts of various susceptibilities

2019 ◽  
Author(s):  
Aurélien Chateigner ◽  
Yannis Moreau ◽  
Davy Jiolle ◽  
Cindy Pontlevé ◽  
Carole Labrousse ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Transmission Probability ◽  
Evolutionary Potential ◽  
Virulence Evolution ◽  
Specific Host ◽  
Trade Offs ◽  
Virulent Strains ◽  
High Virulence ◽  
Infection Cycles ◽  
Highly Virulent

AbstractPathogens should evolve to avirulence. However, while baculoviruses can be transmitted through direct contact, their main route of infection goes through the death and liquefaction of their caterpillar hosts and highly virulent strains still seem to be advantaged through infection cycles. Furthermore, one of them,Autographa californicamultiple nucleopolyhedrovirus, is so generalist that it can infect more than 100 different hosts.To understand and characterize the evolutionary potential of this virus and how it is maintained while killing some of its hosts in less than a week, we performed an experimental evolution starting from an almost natural isolate of AcMNPV, known for its generalist infection capacity. We made it evolve on 4 hosts of different susceptibilities for 10 cycles and followed hosts survival each day. We finally evaluated whether the generalist capacity was maintained after evolving on one specific host species and tested an epidemiological model through simulations to understand how.Finally, on very highly susceptible hosts, transmission-virulence trade-offs seem to disappear and the virus can maximize transmission and virulence. When less adapted to its host, the pathogen’s virulence has not been modified along cycles but the yield was increased, apparently through an increased transmission probability and an increased latent period between exposition and infection.

scholarly journals Host heterogeneity mitigates virulence evolution

2020 ◽  
Vol 16 (1) ◽  
pp. 20190744 ◽  
Author(s):  
P. Signe White ◽  
Angela Choi ◽  
Rishika Pandey ◽  
Arthur Menezes ◽  
McKenna Penley ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Parasite Prevalence ◽  
Mixed Genotype ◽  
Selective Pressures ◽  
Virulence Evolution ◽  
Specific Host ◽  
Trade Offs ◽  
Evolutionary Trajectories ◽  
Parasite Populations ◽  
Host Heterogeneity

Parasites often infect genetically diverse host populations, and the evolutionary trajectories of parasite populations may be shaped by levels of host heterogeneity. Mixed genotype host populations, compared to homogeneous host populations, can reduce parasite prevalence and potentially reduce rates of parasite adaptation due to trade-offs associated with adapting to specific host genotypes. Here, we used experimental evolution to select for increased virulence in populations of the bacterial parasite Serratia marcescens exposed to either heterogeneous or homogeneous populations of Caenorhabditis elegans . We found that parasites exposed to heterogeneous host populations evolved significantly less virulence than parasites exposed to homogeneous host populations over several hundred bacterial generations. Thus, host heterogeneity impeded parasite adaptation to host populations. While we detected trade-offs in virulence evolution, parasite adaptation to two specific host genotypes also resulted in modestly increased virulence against the reciprocal host genotypes. These results suggest that parasite adaptation to heterogeneous host populations may be impeded by both trade-offs and a reduction in the efficacy of selection as different host genotypes exert different selective pressures on a parasite population.

scholarly journals Transient virulence of emerging pathogens

2009 ◽  
Vol 7 (46) ◽  
pp. 811-822 ◽  
Author(s):  
Benjamin M. Bolker ◽  
Arjun Nanda ◽  
Dharmini Shah
Keyword(s):  
Genetic Variance ◽  
Evolutionary Dynamics ◽  
Growth Conditions ◽  
Emerging Pathogens ◽  
Potential Significance ◽  
Phase Selection ◽  
Transmission Rates ◽  
Virulence Evolution ◽  
High Virulence ◽  
Highly Virulent

Should emerging pathogens be unusually virulent? If so, why? Existing theories of virulence evolution based on a tradeoff between high transmission rates and long infectious periods imply that epidemic growth conditions will select for higher virulence, possibly leading to a transient peak in virulence near the beginning of an epidemic. This transient selection could lead to high virulence in emerging pathogens. Using a simple model of the epidemiological and evolutionary dynamics of emerging pathogens, along with rough estimates of parameters for pathogens such as severe acute respiratory syndrome, West Nile virus and myxomatosis, we estimated the potential magnitude and timing of such transient virulence peaks. Pathogens that are moderately evolvable, highly transmissible, and highly virulent at equilibrium could briefly double their virulence during an epidemic; thus, epidemic-phase selection could contribute significantly to the virulence of emerging pathogens. In order to further assess the potential significance of this mechanism, we bring together data from the literature for the shapes of tradeoff curves for several pathogens (myxomatosis, HIV, and a parasite of Daphnia ) and the level of genetic variation for virulence for one (myxomatosis). We discuss the need for better data on tradeoff curves and genetic variance in order to evaluate the plausibility of various scenarios of virulence evolution.

scholarly journals Genetic diversity of Colletotrichum lupini and its virulence on white and Andean lupin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. A. Alkemade ◽  
M. M. Messmer ◽  
R. T. Voegele ◽  
M. R. Finckh ◽  
P. Hohmann
Keyword(s):  
Fungal Pathogen ◽  
Intraspecific Diversity ◽  
White Lupin ◽  
Breeding Programs ◽  
Center Of Origin ◽  
Genetic Groups ◽  
Virulent Strains ◽  
High Virulence ◽  
Colletotrichum Lupini ◽  
Highly Virulent

AbstractLupin cultivation worldwide is threatened by anthracnose, a destructive disease caused by the seed- and air-borne fungal pathogen Colletotrichum lupini. In this study we explored the intraspecific diversity of 39 C. lupini isolates collected from different lupin cultivating regions around the world, and representative isolates were screened for their pathogenicity and virulence on white and Andean lupin. Multi-locus phylogeny and morphological characterizations showed intraspecific diversity to be greater than previously shown, distinguishing a total of six genetic groups and ten distinct morphotypes. Highest diversity was found across South America, indicating it as the center of origin of C. lupini. The isolates that correspond to the current pandemic belong to a genetic and morphological uniform group, were globally widespread, and showed high virulence on tested white and Andean lupin accessions. Isolates belonging to the other five genetic groups were mostly found locally and showed distinct virulence patterns. Two highly virulent strains were shown to overcome resistance of advanced white lupin breeding material. This stresses the need to be careful with international seed transports in order to prevent spread of currently confined but potentially highly virulent strains. This study improves our understanding of the diversity, phylogeography and pathogenicity of a member of one of the world’s top 10 plant pathogen genera, providing valuable information for breeding programs and future disease management.

scholarly journals Treating symptomatic infections and the co-evolution of virulence and drug resistance

2020 ◽  
Author(s):  
Samuel Alizon
Keyword(s):  
Evolutionary Dynamics ◽  
Adaptive Dynamics ◽  
Drug Resistant ◽  
Treatment Rate ◽  
Virulence Evolution ◽  
Trade Offs ◽  
Virulent Strains ◽  
Host Mortality ◽  
Parameter Values

AbstractAntimicrobial therapeutic treatments are by definition applied after the onset of symptoms, which tend to correlate with infection severity. Using mathematical epidemiology models, I explore how this link affects the coevolutionary dynamics between the virulence of an infection, measured via host mortality rate, and its susceptibility to chemotherapy. I show that unless resistance pre-exists in the population, drug-resistant infections are initially more virulent than drug-sensitive ones. As the epidemic unfolds, virulence is more counter-selected in drug-sensitive than in drug-resistant infections. This difference decreases over time and, eventually, the exact shape of genetic trade-offs govern long-term evolutionary dynamics. Using adaptive dynamics, I show that two types of evolutionary stable strategies (ESS) may be reached in the context of this simple model and that, depending on the parameter values, an ESS may only be locally stable. In general, the more the treatment rate increases with virulence, the lower the ESS value. Overall, both on the short-term and long-term, having treatment rate depend on infection virulence tend to favour less virulent strains in drug-sensitive infections. These results highlight the importance of the feedbacks between epidemiology, public health policies and parasite evolution, and have implications for the monitoring of virulence evolution.

How Molecular Epidemiology Can Affect Tuberculosis Control in the Middle East Countries: A Systematic Review and Meta-Analysis

2020 ◽  
Vol 20 ◽  
Author(s):  
Mohammad Asgharzadeh ◽  
Jalil Rashedi ◽  
Behroz Mahdavi Poor ◽  
Hossein Samadi kafil ◽  
Hossein Moharram Zadeh ◽  
...  
Keyword(s):  
Middle East ◽  
Molecular Epidemiology ◽  
Average Rate ◽  
Meta Analysis ◽  
Close Monitoring ◽  
Drug Resistant ◽  
Middle East Countries ◽  
Virulent Strains ◽  
Recent Transmission ◽  
Highly Virulent

: Nowadays, due to the incidence of specific strains of Mycobacterium tuberculosis and also increase the rate of drug resistant-TB mortality rate has elevated by this disease. Identification of common strains in the region as well as sources of transmission are essential to control the disease that this has been possible by using molecular epidemiology. In this survey, studies which have been carried out based on spoligotyping method in Muslim Middle East countries were considered to determine their role in control of TB. All studies conducted from 2005 to June 2016 were considered systematically in three electronic data bases and finally, 23 studies were selected. The average rate of clustering was 84% and the rate of recent transmission was variable from 21.7% to 92.4%. Incidence of Beijing strains was been rising in the considered countries. In Iran and Saudi Arabia which are immigration and labour-hosting countries, respectively, rapid transmittable strains and drug resistant Beijings were higher than other considered countries. Considering the incidence of highly virulent strains, due to the increase of immigration and people infected with HIV, tuberculosis, especially drug resistant form, the lack of close monitoring in the future will be induce trouble.

scholarly journals Sero- and apx-typing of German Actinobacillus pleuropneumoniae field isolates from 2010 to 2019 reveals a predominance of serovar 2 with regular apx-profile

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
Lukas Schuwerk ◽  
Doris Hoeltig ◽  
Karl-Heinz Waldmann ◽  
Peter Valentin-Weigand ◽  
Judith Rohde
Keyword(s):  
Reference Strain ◽  
Actinobacillus Pleuropneumoniae ◽  
Etiological Agent ◽  
Toxin Gene ◽  
Gene Profile ◽  
Field Isolates ◽  
Porcine Pleuropneumonia ◽  
Virulent Strains ◽  
Highly Virulent

AbstractSerotyping is the most common method to characterize field isolates of Actinobacillus (A.) pleuropneumoniae, the etiological agent of porcine pleuropneumonia. Based on serology, many farms seem to be infected and antibodies against a wide variety of serovars are detectable, but, so far it is unknown to what degree respective serovars contribute to outbreaks of clinical manifest disease. In this study, 213 German A. pleuropneumoniae field isolates retrieved for diagnostic purposes from outbreaks of porcine pleuropneumonia between 2010 and 2019 were genetically serotyped and analyzed regarding their apx-toxin gene profile using molecular methods. Serotyping revealed a prominent role of serovar 2 in clinical cases (64% of all isolates) and an increase in the detection of this serovar since 2010 in German isolates. Serovar 9/11 followed as the second most frequent serovar with about 15% of the isolates. Furthermore, very recently described serovars 16 (n = 2) and 18 (n = 8) were detected. Most isolates (93.4%) showed apx-profiles typical for the respective serovar. However, this does not hold true for isolates of serovar 18, as 75% (n = 6) of all isolates of this serovar deviated uniformly from the “typical” apx-gene profile of the reference strain 7311555. Notably, isolates from systemic lesions such as joints or meninges did not harbor the complete apxICABD operon which is considered typical for highly virulent strains. Furthermore, the extremely low occurrence (n = 1) of NAD independent (biovar II) isolates in German A. pleuropneumoniae was evident in our collection of clinical isolates.

scholarly journals Sexual conflict drives micro- and macroevolution of sexual dimorphism in immunity

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Basabi Bagchi ◽  
Quentin Corbel ◽  
Imroze Khan ◽  
Ellen Payne ◽  
Devshuvam Banerji ◽  
...  
Keyword(s):  
Sex Differences ◽  
Sexual Dimorphism ◽  
Mating System ◽  
Sexual Conflict ◽  
Experimental Evolution ◽  
Parasitic Infections ◽  
Pathogen Dynamics ◽  
Trade Offs ◽  
Host Pathogen ◽  
Seed Beetles

Abstract Background Sexual dimorphism in immunity is believed to reflect sex differences in reproductive strategies and trade-offs between competing life history demands. Sexual selection can have major effects on mating rates and sex-specific costs of mating and may thereby influence sex differences in immunity as well as associated host–pathogen dynamics. Yet, experimental evidence linking the mating system to evolved sexual dimorphism in immunity are scarce and the direct effects of mating rate on immunity are not well established. Here, we use transcriptomic analyses, experimental evolution and phylogenetic comparative methods to study the association between the mating system and sexual dimorphism in immunity in seed beetles, where mating causes internal injuries in females. Results We demonstrate that female phenoloxidase (PO) activity, involved in wound healing and defence against parasitic infections, is elevated relative to males. This difference is accompanied by concomitant sex differences in the expression of genes in the prophenoloxidase activating cascade. We document substantial phenotypic plasticity in female PO activity in response to mating and show that experimental evolution under enforced monogamy (resulting in low remating rates and reduced sexual conflict relative to natural polygamy) rapidly decreases female (but not male) PO activity. Moreover, monogamous females had evolved increased tolerance to bacterial infection unrelated to mating, implying that female responses to costly mating may trade off with other aspects of immune defence, an hypothesis which broadly accords with the documented sex differences in gene expression. Finally, female (but not male) PO activity shows correlated evolution with the perceived harmfulness of male genitalia across 12 species of seed beetles, suggesting that sexual conflict has a significant influence on sexual dimorphisms in immunity in this group of insects. Conclusions Our study provides insights into the links between sexual conflict and sexual dimorphism in immunity and suggests that selection pressures moulded by mating interactions can lead to a sex-specific mosaic of immune responses with important implications for host–pathogen dynamics in sexually reproducing organisms.

scholarly journals Genome-Assisted Development of a Diagnostic Protocol for Distinguishing High Virulence Pseudomonas syringae pv. tomato Strains

Plant Disease ◽  
2015 ◽  
Vol 99 (4) ◽  
pp. 527-534 ◽  
Author(s):  
Lisa A. Jones ◽  
Surya Saha ◽  
Alan Collmer ◽  
Christine D. Smart ◽  
Magdalen Lindeberg
Keyword(s):  
New York ◽  
Pseudomonas Syringae ◽  
Genome Comparison ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Host Interaction ◽  
Group I ◽  
Virulent Strains ◽  
High Virulence ◽  
Relationship Of

A severe outbreak of bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, occurred in central New York in 2009. Isolate 09150, collected from this outbreak and subsequently named NYS-T1, was found to be highly virulent on tomato. To better understand the relationship of 09150 to other P. syringae strains and develop a diagnostic assay for aggressive strains of this pathogen, the 09150 genome was sequenced. Genome comparison revealed it to be highly similar to a previously sequenced isolate, T1. Genetic factors linked to host interaction including type III effectors, toxin biosynthetic genes, and elicitors of host innate immunity were identified. Type III effector repertoires were compared with other strains in the high virulence T1-like subgroup and lower virulence DC3000/P. syringae pv. maculicola subgroup within P. syringae phylogenetic Group I. Primers for conventional PCR were developed using sequences for avrA, hopW, conserved in the former subgroup and hopN, present in the latter. These were tested on isolates in the two subgroups, other pseudomonads, and other bacterial pathogens of tomato. Primers developed for avaA and hopW were diagnostic for more virulent strains of P. syringae pv. tomato while primers for hopN were diagnostic for P. syringae pv. tomato DC3000 and related P. syringe pv. maculicola strains. Primers designed against hopR distinguished both of these P. syringae subgroups from other P. syringae strains.

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