0000000001308039
AUTHOR
Ilona Merikanto
Invasion Ability and Disease Dynamics of Environmentally Growing Opportunistic Pathogens under Outside-Host Competition
Most theories of the evolution of virulence concentrate on obligatory host-pathogen relationship. Yet, many pathogens replicate in the environment outside-host where they compete with non-pathogenic forms. Thus, replication and competition in the outside-host environment may have profound influence on the evolution of virulence and disease dynamics. These environmentally growing opportunistic pathogens are also a logical step towards obligatory pathogenicity. Efficient treatment methods against these diseases, such as columnaris disease in fishes, are lacking because of their opportunist nature. We present a novel epidemiological model in which replication and competition in the outside-hos…
Outside-host growth of pathogens attenuates epidemiological outbreaks.
Opportunist saprotrophic pathogens differ from obligatory pathogens due to their capability in host-independent growth in environmental reservoirs. Thus, the outside-host environment potentially influences host-pathogen dynamics. Despite the socio-economical importance of these pathogens, theory on their dynamics is practically missing. We analyzed a novel epidemiological model that couples outside-host density-dependent growth to host-pathogen dynamics. Parameterization was based on columnaris disease, a major hazard in fresh water fish farms caused by saprotrophic Flavobacterium columnare. Stability analysis and numerical simulations revealed that the outside-host growth maintains high pr…
Outside-host phage therapy as a biological control against environmental infectious diseases
Background Environmentally growing pathogens present an increasing threat for human health, wildlife and food production. Treating the hosts with antibiotics or parasitic bacteriophages fail to eliminate diseases that grow also in the outside-host environment. However, bacteriophages could be utilized to suppress the pathogen population sizes in the outside-host environment in order to prevent disease outbreaks. Here, we introduce a novel epidemiological model to assess how the phage infections of the bacterial pathogens affect epidemiological dynamics of the environmentally growing pathogens. We assess whether the phage therapy in the outside-host environment could be utilized as a biologi…
Additional file 2: of Outside-host phage therapy as a biological control against environmental infectious diseases
Equilibrium population densities and the Jacobian matrices for phage therapy model (1)â (6). Local stability analysis of the P-S-I submodel at S=Iâ =â 0 in the absence of recovery. (DOCX 30 kb)
Outside-host predation as a biological control against an environmental opportunist disease
Abstract Environmentally growing opportunist pathogens are a common threat to human health and food production. Due to environmental growth of the pathogen, these diseases are difficult to control with disinfectants and antibiotics. Thus, there is a need for sustainable and effective control methods against environmentally growing opportunist diseases. Predation is often a major limiting factor in the outside host environment. Here we propose that it could be used in the biological control of these diseases. We introduce a novel epidemiological model for environmentally growing opportunists combining pathogen growth within-host (SI model) and outside-host into classical predator-prey model.…
Additional file 3: of Outside-host phage therapy as a biological control against environmental infectious diseases
Figure S2 Local stability analysis for susceptible host, infected host, pathogen and bacteriophage dynamics (S-I-P-F) when the phage transmission and release rate are varied (10− 9 0 is locally stable for high values of Λ F and β F (blue area). The coexistence equilibrium does not exist for lower values of when Λ F and β F (yellow area). In this case S and I become asymptotically extinct. Pathogen P always survives and even coexists with the phage F in the absence of the host S. The parameter values used are shown in Table 1. (TIF 2096 kb)
Additional file 4: of Outside-host phage therapy as a biological control against environmental infectious diseases
Figure S3 Time dynamics of pathogen, susceptible, infected host and bacteriophage dynamics (S-I-P-F) when the phage transmission and release rate are high (β F = 10− 3 and Λ F = 100). X-axis shows time in days and y-axis the population density. The pathogen population decreases close to extinction almost immediately, while there is a delay of approximately 47 days for the elimination of the disease and more than 50 days for decrease of the phage population close to extinction. The parameter values used are shown in Table 1. (TIF 2818 kb)
Additional file 1: of Outside-host phage therapy as a biological control against environmental infectious diseases
Figure S1 Time dynamics of pathogen, susceptible and infected host dynamics (S-I-P) in the absence of viral infection by bacteriophages and competition between the phage-resistant bacteria and the pathogen. X-axis and y-axis show time in days and the population density, respectively. Parameter values used are given in Table 1. In the absence of bacteriophages and phage-resistant bacteria, the pathogen (P), drives the susceptible host quickly extinct after which the infected host population goes extinct as well and the pathogen population stabilizes to grow saprothrophically in the absence of susceptible hosts. (TIF 2383 kb)