Challenging the trade-off model for the evolution of virulence: is virulence management feasible?

2003 ◽  
Vol 11 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Dieter Ebert ◽  
James J. Bull
Keyword(s):  
Trade Off ◽  
Evolution Of Virulence

scholarly journals Parasite variation and the evolution of virulence in a Daphnia-microparasite system

Parasitology ◽  
2007 ◽  
Vol 135 (3) ◽  
pp. 303-308 ◽  
Author(s):  
T. J. LITTLE ◽  
W. CHADWICK ◽  
K. WATT
Keyword(s):  
Genetic Variation ◽  
Rank Order ◽  
Genetic Relationships ◽  
Natural Populations ◽  
Host Genotype ◽  
Relative Growth ◽  
Trade Off ◽  
Relative Growth Rates ◽  
Pasteuria Ramosa ◽  
Evolution Of Virulence

SUMMARYUnderstanding genetic relationships amongst the life-history traits of parasites is crucial for testing hypotheses on the evolution of virulence. This study therefore examined variation between parasite isolates (the bacterium Pasteuria ramosa) from the crustacean Daphnia magna. From a single wild-caught infected host we obtained 2 P. ramosa isolates that differed substantially in the mortality they caused. Surprisingly, the isolate causing higher early mortality was, on average, less successful at establishing infections and had a slower growth rate within hosts. The observation that within-host replication rate was negatively correlated with mortality could violate a central assumption of the trade-off hypothesis for the evolution of virulence, but we discuss a number of caveats which caution against premature rejection of the trade-off hypothesis. We sought to test if the characteristics of these parasite isolates were constant across host genotypes in a second experiment that included 2 Daphnia host clones. The relative growth rates of the two parasite isolates did indeed depend on the host genotype (although the rank order did not change). We suggest that testing evolutionary hypotheses for virulence may require substantial sampling of both host and parasite genetic variation, and discuss how selection for virulence may change with the epidemiological state of natural populations and how this can promote genetic variation for virulence.

scholarly journals Detection, not mortality, constrains the evolution of virulence

2021 ◽  
Author(s):  
David A Kennedy
Keyword(s):  
Mathematical Model ◽  
Disease Severity ◽  
Behavioral Change ◽  
Scientific Literature ◽  
Empirical Support ◽  
Infectious Period ◽  
Trade Off ◽  
Evolution Of Virulence ◽  
Host Mortality

Why would a pathogen evolve to kill its hosts when killing a host ends a pathogen's own opportunity for transmission? A vast body of scientific literature has attempted to answer this question using "trade-off theory," which posits that host mortality persists due to its cost being balanced by benefits of other traits that correlate with host mortality. The most commonly invoked trade-off is the mortality-transmission trade-off, where increasingly harmful pathogens are assumed to transmit at higher rates from hosts while the hosts are alive, but the pathogens truncate their infectious period by killing their hosts. Here I show that costs of mortality are too small to plausibly constrain the evolution of disease severity except in systems where survival is rare. I alternatively propose that disease severity can be much more readily constrained by a cost of behavioral change due to the detection of infection, whereby increasingly harmful pathogens have increasing likelihood of detection and behavioral change following detection, thereby limiting opportunities for transmission. Using a mathematical model, I show the conditions under which detection can limit disease severity. Ultimately, this argument may explain why empirical support for trade-off theory has been limited and mixed.

WITHIN-HOST PARASITE DYNAMICS, EMERGING TRADE-OFF, AND EVOLUTION OF VIRULENCE WITH IMMUNE SYSTEM

Evolution ◽  
2003 ◽  
Vol 57 (7) ◽  
pp. 1489 ◽  
Author(s):  
Jean-Baptiste André ◽  
Jean-Baptiste Ferdy ◽  
Bernard Godelle
Keyword(s):  
Immune System ◽  
Trade Off ◽  
Evolution Of Virulence ◽  
Host Parasite ◽  
Parasite Dynamics

scholarly journals Competition–colonization trade-off promotes coexistence of low-virulence viral strains

2012 ◽  
Vol 9 (74) ◽  
pp. 2244-2254 ◽  
Author(s):  
Samuel Ojosnegros ◽  
Edgar Delgado-Eckert ◽  
Niko Beerenwinkel
Keyword(s):  
Rna Viruses ◽  
Rna Virus ◽  
Diverse Populations ◽  
Trade Off ◽  
Virulent Strains ◽  
Evolution Of Virulence ◽  
Virulence Attenuation ◽  
Fast Spreading ◽  
Infected Cells ◽  
Virus Clone

RNA viruses exist as genetically diverse populations displaying a range of virulence degrees. The evolution of virulence in viral populations is, however, poorly understood. On the basis of the experimental observation of an RNA virus clone in cell culture diversifying into two subpopulations of different virulence, we study the dynamics of mutating virus populations with varying virulence. We introduce a competition–colonization trade-off into standard mathematical models of intra-host viral infection. Colonizers are fast-spreading virulent strains, whereas the competitors are less-virulent variants but more successful within co-infected cells. We observe a two-step dynamics of the population. Early in the infection, the population is dominated by colonizers, which later are outcompeted by competitors. Our simulations suggest the existence of steady state in which all virulence classes coexist but are dominated by the most competitive ones. This equilibrium implies collective virulence attenuation in the population, in contrast to previous models predicting evolution of the population towards increased virulence.

scholarly journals The Evolution of Virulence in RNA Viruses under a Competition–Colonization Trade-Off

2010 ◽  
Vol 73 (8) ◽  
pp. 1881-1908 ◽  
Author(s):  
Edgar Delgado-Eckert ◽  
Samuel Ojosnegros ◽  
Niko Beerenwinkel
Keyword(s):  
Rna Viruses ◽  
Trade Off ◽  
Evolution Of Virulence

scholarly journals WITHIN-HOST PARASITE DYNAMICS, EMERGING TRADE-OFF, AND EVOLUTION OF VIRULENCE WITH IMMUNE SYSTEM

Evolution ◽  
2003 ◽  
Vol 57 (7) ◽  
pp. 1489-1497 ◽  
Author(s):  
Jean-Baptiste André ◽  
Jean-Baptiste Ferdy ◽  
Bernard Godelle
Keyword(s):  
Immune System ◽  
Trade Off ◽  
Evolution Of Virulence ◽  
Host Parasite ◽  
Parasite Dynamics

scholarly journals Within-host parasite cooperation and the evolution of virulence

2011 ◽  
Vol 278 (1725) ◽  
pp. 3738-3747 ◽  
Author(s):  
Samuel Alizon ◽  
Sébastien Lion
Keyword(s):  
Population Level ◽  
Linear Functions ◽  
Parasite Transmission ◽  
Trade Off ◽  
Selective Pressures ◽  
Virulent Strains ◽  
Evolution Of Virulence ◽  
Simplifying Assumptions ◽  
Complex Relationships ◽  
Host Parasite

Infections by multiple genotypes are common in nature and are known to select for higher levels of virulence for some parasites. When parasites produce public goods (PGs) within the host, such co-infections have been predicted to select for lower levels of virulence. However, this prediction is based on simplifying assumptions regarding epidemiological feedbacks on the multiplicity of infections (MOI). Here, we analyse the case of parasites producing a PG (for example, siderophore-producing bacteria) using a nested model that ties together within-host and epidemiological processes. We find that the prediction that co-infection should select for less virulent strains for PG-producing parasites is only valid if both parasite transmission and virulence are linear functions of parasite density. If there is a trade-off relationship such that virulence increases more rapidly than transmission, or if virulence also depends on the total amount of PGs produced, then more complex relationships between virulence and the MOI are predicted. Our results reveal that explicitly taking into account the distribution of parasite strains among hosts could help better understand the selective pressures faced by parasites at the population level.

A Flow-Preserving Algorithm for the Time-Cost Trade-Off Problem

1982 ◽  
Vol 14 (2) ◽  
pp. 109-113 ◽  
Author(s):  
Suleyman Tufekci
Keyword(s):  
Time Cost ◽  
Trade Off

Dual Goals for Speed and Accuracy on the Same Performance Task

2012 ◽  
Vol 11 (3) ◽  
pp. 118-126 ◽  
Author(s):  
Olive Emil Wetter ◽  
Jürgen Wegge ◽  
Klaus Jonas ◽  
Klaus-Helmut Schmidt
Keyword(s):  
Memory Scanning ◽  
Performance Task ◽  
Performance Tasks ◽  
Trade Off ◽  
Test Experiment ◽  
Trade Offs ◽  
New Finding ◽  
Sternberg Paradigm ◽  
Speed Accuracy ◽  
Speed And Accuracy

In most work contexts, several performance goals coexist, and conflicts between them and trade-offs can occur. Our paper is the first to contrast a dual goal for speed and accuracy with a single goal for speed on the same task. The Sternberg paradigm (Experiment 1, n = 57) and the d2 test (Experiment 2, n = 19) were used as performance tasks. Speed measures and errors revealed in both experiments that dual as well as single goals increase performance by enhancing memory scanning. However, the single speed goal triggered a speed-accuracy trade-off, favoring speed over accuracy, whereas this was not the case with the dual goal. In difficult trials, dual goals slowed down scanning processes again so that errors could be prevented. This new finding is particularly relevant for security domains, where both aspects have to be managed simultaneously.

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