Modeling the indirect effect of Wolbachia on the infection dynamics of horizontally transmitted viruses

Multiscale modelling the effects of CI genetic evolution in mosquito population on the control of dengue fever

Endosymbiotic Wolbachia bacteria are widely applied for the control of dengue fever by manipulating the reproductive mechanism of mosquitoes, including maternal inheritance and cytoplasmic incompatibility (CI). CI means that the offsprings from the matings between Wolbachia infected males and uninfected females can not be hatched. At present, CI effect is assumed as a constant in most of dynamic systems for the spread of Wolbachia. However, their spread may arouse the evolution of mosquitoes to resist CI. Thus, a multiscale model combining a birth-pulse model with a gene-induced discrete model for the frequencies of alleles is proposed to describe the spread of Wolbachia in mosquito population with resistance allele of CI. The main results indicate that the strategy of population eradication can not be realized, while the strategy of population replacement may be realized with the success of sensitive or resistance allele. If appropriate Wolbachia strains can not be selected, then there is a high probability of the failure of population replacement. Moreover, Wolbachia-induced parameters may arouse the catastrophic shifts among stable states of the model. In addition, the demographic parameters and Wolbachia-induced parameters may affect the level and the speed of population replacement and the density of uninfected mosquitoes.

The evolutionary and coevolutionary consequences of defensive microbes for host-parasite interactions

Background

Animal and plant species can harbour microbes that provide them with protection against enemies. These beneficial microbes can be a significant component of host defence that complement or replaces a repertoire of immunity, but they can also be costly. Given their impact on host and parasite fitness, defensive microbes have the potential to influence host-parasite interactions on an evolutionary timescale.

Results

Using a phenotypic framework, we explore the evolutionary and coevolutionary dynamics of a host-parasite interaction in the presence of defensive microbes. We show that costs of host-defensive microbe systems are critical in determining whether a defensive microbe based system or an immune system provides better host protection investment. Partitioning the coevolutionary dynamics yields testable predictions. The density of defensive microbes influences the strength of selection resulting from host - defensive microbe - parasite coevolutionary interactions. We find that they lessen the negative effects of infection on hosts and reduce infectivity by directly competing with parasites.

Conclusions

Defensive microbes might thus play a central role in host-parasite interactions, by outright replacing host-based defences, engaging in within-host competition with parasites, and ultimately driving tripartite coevolutionary dynamics.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-017-1030-z) contains supplementary material, which is available to authorized users.

Human Permanent Ectoparasites; Recent Advances on Biology and Clinical Significance of Demodex Mites: Narrative Review Article

BACKGROUND

Demodex is a genus of mites living predominantly in mammalian pilosebaceous units. They are commonly detected in the skin of face, with increasing numbers in inflammatory lesions. Causation between Demodex mites and inflammatory diseases, such as rosacea, blepharitis, perioral and seborrhoeic dermatitis or chalazion, is controversially discussed. Clinical observations indicate a primary form of human Demodex infection. The aim of this review was to highlight the biological aspects of Demodex infestation and point out directions for the future research.

METHODS

We conducted a broad review based on the electronic database sources such as MEDLINE, PubMed and Scopus with regard to the characteristics of the Demodex species, methods of examination and worldwide epidemiology, molecular studies and its role in the complex human ecosystem.

RESULTS

Demodex mites are organisms with a worldwide importance as they act in indicating several dermatoses, under certain conditions. However, correlations between Demodex and other parasites or microorganisms occupying one host, as well as interactions between these arachnids and its symbiotic bacteria should be considered. There are few methods of human mites' examination depending on purpose of the study. Nevertheless, paying attention must be needed as polymorphism of Demodex species has been reported.

CONCLUSION

Overall, the present review will focus on different aspects of Demodex mites' biology and significance of these arachnids in human's health.

Host and Parasite Evolution in a Tangled Bank

Most hosts and parasites exist in diverse communities wherein they interact with other species, spanning the parasite-mutualist continuum. These additional interactions have the potential to impose selection on hosts and parasites and influence the patterns and processes of their evolution. Yet, host-parasite interactions are almost exclusively studied in species pairs. A wave of new research has incorporated a multispecies community context, showing that additional ecological interactions can alter components of host and parasite fitness, as well as interaction specificity and virulence. Here, we synthesize these findings to assess the effects of increased species diversity on the patterns and processes of host and parasite evolution. We argue that our understanding of host-parasite interactions would benefit from a richer biotic perspective.