The effect of aggregative overwintering on an insect sexually transmitted parasite system

In contrast to the extensively studied sexually transmitted diseases (STDs) of humans, little is known of the ecology or evolutionary biology of sexually transmitted parasites in natural systems. This study of a sexually transmitted parasite on an insect host augments our understanding of both the parasite's population dynamics and virulence effects. The impact of overwintering was assessed on the prevalence of the parasitic mite Coccipolipus hippodamiae on the two-spot ladybird, Adalia bipunctata. First, the effect of infection on host survival was examined during the stressful overwintering period. Box experiments in the field revealed that the infected ladybirds, especially males, are less likely to survive overwintering. The study provides the first evidence that the parasite harms males and suggests revisions of theories on the adaptive virulence of sexually transmitted parasites. It also indicates the importance of using a range of experimental conditions because virulence can be dependent on host condition and sex. Box experiments were also used to examine whether transmission of the parasite occurs within overwintering aggregations. These revealed that substantial transmission does not occur in aggregations and that transmission is predominantly sexual. Overall, the virulence effects and the lack of transmission mean that the overwintering period acts to diminish parasite prevalence and will retard the spring epidemic associated with host reproductive activity.     

The sexually transmitted insect virus,Hz-2V

Hz-2V is one of only a very few sexually transmitted viruses currently known in insects. Replication of this insect pathogenic virus results in sterility of infected moths rather than mortality. The sterility of the infected host is a consequence of virus directed malformation of adult reproductive tissues, which in females results in cellular proliferation and hypertrophy of these tissues. Virus replication has additional ramifications in infected females. Infected females produce more mating pheromones and attract more mates than healthy females, ultimately facilitating virus transmission and enhancing viral fitness. The molecular mechanisms used by the virus to manipulate the host to enhance its fitness are yet to be determined. Unraveling the underlying principles of these mechanisms promises to enhance our understanding of insect reproductive physiology, as well as provide molecular tools for use in novel approaches in sterile insect control programs.     

The role of sexually transmitted diseases in HIV transmission

More than 42 million people worldwide are now infected with HIV, in spite of sustained prevention activities. Although the spread of HIV has been primarily sexual, epidemiological studies have indicated that the efficiency of the spread of HIV is poor, perhaps as infrequently as 1 in every 1,000 episodes of sexual intercourse. However, sexually transmitted diseases (STDs) that cause ulcers or inflammation greatly increase the efficiency of HIV transmission--by increasing both the infectiousness of, and the susceptibility to HIV infection. STDs might be particularly important in the early stages of a localized HIV epidemic, when people with risky sexual behaviour are most likely to become infected. In China, eastern Europe and Russia, there has been a remarkable increase in the incidence of STDs in recent years, and this is reflected in the rapid increase in the spread of HIV in these areas. Targeted STD detection and treatment should have a central role in HIV prevention in these emerging epidemics.     

Triggers of self-conscious emotions in the sexually transmitted infection testing process

Background

Self-conscious emotions (shame, guilt and embarrassment) are part of many individuals' experiences of seeking STI testing. These emotions can have negative impacts on individuals' interpretations of the STI testing process, their willingness to seek treatment and their willingness to inform sexual partners in light of positive STI diagnoses. Because of these impacts, researchers have called for more work to be completed on the connections between shame, guilt, embarrassment and STI testing. We examine the specific events in the STI testing process that trigger self-conscious emotions in young adults who seek STI testing; and to understand what it is about these events that triggers these emotions.Semi-structured interviews with 30 adults (21 women, 9 men) in the Republic of Ireland.

Findings

Seven specific triggers of self-conscious emotions were identified. These were: having unprotected sex, associated with the initial reason for seeking STI testing; talking to partners and peers about the intention to seek STI testing; the experience of accessing STI testing facilities and sitting in clinic waiting rooms; negative interactions with healthcare professionals; receiving a positive diagnosis of an STI; having to notify sexual partners in light of a positive STI diagnosis; and accessing healthcare settings for treatment for an STI. Self-conscious emotions were triggered in each case by a perceived threat to respondents' social identities.

Conclusion

There are multiple triggers of self-conscious emotions in the STI testing process, ranging from the initial decision to seek testing, right through to the experience of accessing treatment. The role of self-conscious emotions needs to be considered in each component of service design from health promotion approaches, through facility layout to the training of all professionals involved in the STI testing process.

     

The role of resources and natural enemies in determining the distribution of an insect herbivore population

1. Both resources and natural enemies can influence the distribution of a herbivore. The ideal free distribution predicts that herbivores distribute themselves to optimise utilisation of resources. There is also evidence of herbivores seeking out refuges that reduce natural enemy attack (enemy‐free space). Which of these theories predominates in a thistle–tephritid Terellia ruficauda (Diptera: Tephritidae)–parasitoid interaction is examined. 2. The plant, Cirsium palustre, had a contagious distribution approximated by the negative binomial distribution. Terellia ruficauda foraged preferentially and oviposited on isolated plants although its larvae gained neither nutritional benefit nor reduced natural enemy pressure from such behaviour. 3. Parasitoids of T. ruficauda foraged and oviposited more frequently on isolated than on crowded T. ruficauda, resulting in inverse density‐dependent parasitoid attack at all spatial scales examined. Neither the herbivore nor natural enemies distributed themselves according to the predictions of the ideal free distribution and the herbivore did not oviposit to reduce natural enemy attack. 4. Extrapolating from the theoretical predictions of the ideal free distribution and enemy‐free space to the field requires considerable caution. Terellia ruficauda and its parasitoids appear to select their oviposition sites to spread the risk of losses through factors (e.g. mammal herbivory) that may damage dense clusters of C. palustre.     

The statistical analysis of insect phenology

We introduce two simple methods for the statistical comparison of the temporal pattern of life-cycle events between two populations. The methods are based on a translation of stage-frequency data into individual 'times in stage'. For example, if the stage-k individuals in a set of samples consist of three individuals counted at time t(1) and two counted at time t(2), the observed times in stage k would be (t(1), t(1), t(1), t(2), t(2)). Times in stage then can be compared between two populations by performing stage-specific t-tests or by testing for equality of regression lines of time versus stage between the two populations. Simulations show that our methods perform at close to the nominal level, have good power against a range of alternatives, and have much better operating characteristics than a widely-used phenology model from the literature.     

昆虫内共生菌在昆虫防御中的作用

共生菌在昆虫体内的生长、繁殖过程中起着十分重要的作用,如营养功能、解毒作用、调控生殖及与寄主适应性等等。近些年,一些学者提出了共生菌在寄主抵御天敌等逆境的胁迫时也具有重要的作用。其在寄主防御中的作用可分为3类:(1)昆虫体内共生菌能产生具有抗真菌作用的代谢物,能够抵御病原真菌的入侵,提高寄主的适应性。(2)昆虫抵御寄生蜂的作用与其体内的共生细菌密切相关。(3)共生菌也能产生有毒物质保护寄主免于被捕食。昆虫共生菌在寄主防御中的作用机制除了产生抗菌物质和聚酮类等有毒物质外,还可能通过与水平传播的寄生物(horizontal transmission parasites,HTPs)竞争寄主资源来直接保护寄主。对共生菌的作用的深入研究将有可能进一步明确其功能,并加以利用。     

The regulation landscape of MAPK signaling cascade for thwarting Bacillus thuringiensis infection in an insect host

Host-pathogen interactions are central components of ecological networks where the MAPK signaling pathways act as central hubs of these complex interactions. We have previously shown that an insect hormone modulated MAPK signaling cascade participates as a general switch to trans-regulate differential expression of diverse midgut genes in the diamondback moth, Plutella xylostella (L.) to cope with the insecticidal action of Cry1Ac toxin, produced by the entomopathogenic bacterium Bacillus thuringiensis (Bt). The relationship between topology and functions of this four-tiered phosphorylation signaling cascade, however, is an uncharted territory. Here, we carried out a genome-wide characterization of all the MAPK orthologs in P. xylostella to define their phylogenetic relationships and to confirm their evolutionary conserved modules. Results from quantitative phosphoproteomic analyses, combined with functional validations studies using specific inhibitors and dsRNAs lead us to establish a MAPK “road map”, where p38 and ERK MAPK signaling pathways, in large part, mount a resistance response against Bt toxins through regulating the differential expression of multiple Cry toxin receptors and their non-receptor paralogs in P. xylostella midgut. These data not only advance our understanding of host-pathogen interactions in agricultural pests, but also inform the future development of biopesticides that could suppress Cry resistance phenotypes.     

Revisiting the particular role of host shifts in initiating insect speciation

The notion that shifts to new hosts can initiate insect speciation is more than 150 years old, yet widespread conflation with paradigms of sympatric speciation has led to confusion about how much support exists for this hypothesis. Here, we review 85 insect systems and evaluate the relationship between host shifting, reproductive isolation, and speciation. We sort insects into five categories: (1) systems in which a host shift has initiated speciation; (2) systems in which a host shift has made a contribution to speciation; (3) systems in which a host shift has caused the evolution of new reproductive isolating barriers; (4) systems with host‐associated genetic differences; and (5) systems with no evidence of host‐associated genetic differences. We find host‐associated genetic structure in 65 systems, 43 of which show that host shifts have resulted in the evolution of new reproductive barriers. Twenty‐six of the latter also support a role for host shifts in speciation, including eight studies that definitively support the hypothesis that a host shift has initiated speciation. While this review is agnostic as to the fraction of all insect speciation events to which host shifts have contributed, it clarifies that host shifts absolutely can and do initiate speciation.     

Female biased parasitism and the importance of host generation overlap in a sexually transmitted parasite of beetles

Sexual transmission is a widespread means of infection, but apart from those in humans, the ecology of sexually transmitted organisms is not well known. In this study, we present an ecological study of a sexually transmitted mite, Parobia husbandi Seeman and Nahrung (Acari: Podapolipidae), that lives beneath the elytra of Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae). In each of 2 yr, prevalence of mites on beetles began each spring at about 10-20% but gradually increased to 80-100% by late summer. Overlap of adult beetle generations at this time (i.e., the parental generation mating with the F1 generation) is essential for the persistence of these mites. Mites exhibited temporal change in their spatial distribution on beetles; these changes were probably a response to beetle activity (e.g., emergence from diapause) and the need for dispersal from parental to F1 generation beetles. Prevalence and mean intensity of mites was higher on female beetles compared with male beetles. Female bias of sexually transmitted infection has been predicted in animals but hitherto observed only in primates. We speculate that variable male mate-finding success is the cause of these sex-based differences of mite infections, and that female bias in sexually transmitted disease (STD) infection will be widespread in the animal kingdom.     

Spindles of an entomopoxvirus facilitate its infection of the host insect by disrupting the peritrophic membrane

The mode of action by which entomopoxvirus (EPV) spindles, proteinaceous crystalline bodies produced by EPVs, enhance EPV infection has not been clarified. We fed Anomala cuprea EPV (AcEPV) spindles to host insects; subsequent scanning electron microscopy revealed the disruption of the peritrophic membranes (PMs) of these insects. The PM is reportedly a barrier against the infection of some insects by viruses. Quantitative PCR of AcEPV DNA in the ectoperitrophic area revealed that PM disruption facilitated the passage of EPVs through the PM toward the initial infection site, the midgut epithelium. These results indicate that EPV spindles enhance infection by EPVs by disrupting the PM in the host insects. Fusolin is almost exclusively the constituent protein of the spindles and is the enhancing factor of the infectivity of nucleopolyhedroviruses (NPVs) and possibly that of EPVs. Spheroid is another type of proteinaceous crystalline structure produced by EPVs. Pseudaletia separata EPV (PsEPV) spheroids reportedly contain considerable amounts of fusolin and enhance NPV infection. We assessed the ability of AcEPV spheroids to enhance EPV infectivity and their effect on the PM and carried out immunological experiments; these experiments showed that AcEPV spheroids contain little or no fusolin and are biologically inactive, in contrasts to the situation in PsEPV.     

The influence of sexually active non-reproductive groups on persistent sexually transmitted diseases

We describe several population models exposed to a mild life-long sexually transmitted disease, i.e. without significant increased mortality among infected individuals and providing no immunity/recovery. We then modify these models to include non-reproductive groups consisting of those isolated from sexual contact and those who are sexually active but infertile due to choice, medical or other reasons. We analyse the potential effect on the dynamics of the population. We are interested in how the isolated class may curb the growth of the infected group while keeping the healthy population at acceptable levels. We also analyse the difference between being sexually active and abstained within the non-reproductive class and its impact on the epidemic reproductive number and the nature of the bifurcation around the disease-free equilibrium. We provide a comparison with our models introduced in a previous article, which include only the isolated from sexual contact class.     

The influence of sexually active non-reproductive groups on persistent sexually transmitted diseases

We describe several population models exposed to a mild life-long sexually transmitted disease, i.e. without significant increased mortality among infected individuals and providing no immunity/recovery. We then modify these models to include non-reproductive groups consisting of those isolated from sexual contact and those who are sexually active but infertile due to choice, medical or other reasons. We analyse the potential effect on the dynamics of the population. We are interested in how the isolated class may curb the growth of the infected group while keeping the healthy population at acceptable levels. We also analyse the difference between being sexually active and abstained within the non-reproductive class and its impact on the epidemic reproductive number and the nature of the bifurcation around the disease-free equilibrium. We provide a comparison with our models introduced in a previous article, which include only the isolated from sexual contact class.     

Genital herpes has played a more important role than any other sexually transmitted infection in driving HIV prevalence in Africa

Background

Extensive evidence from observational studies suggests a role for genital herpes in the HIV epidemic. A number of herpes vaccines are under development and several trials of the efficacy of HSV-2 treatment with acyclovir in reducing HIV acquisition, transmission, and disease progression have just reported their results or will report their results in the next year. The potential impact of these interventions requires a quantitative assessment of the magnitude of the synergy between HIV and HSV-2 at the population level.

Methods and Findings

A deterministic compartmental model of HIV and HSV-2 dynamics and interactions was constructed. The nature of the epidemiologic synergy was explored qualitatively and quantitatively and compared to other sexually transmitted infections (STIs). The results suggest a more substantial role for HSV-2 in fueling HIV spread in sub-Saharan Africa than other STIs. We estimate that in settings of high HSV-2 prevalence, such as Kisumu, Kenya, more than a quarter of incident HIV infections may have been attributed directly to HSV-2. HSV-2 has also contributed considerably to the onward transmission of HIV by increasing the pool of HIV positive persons in the population and may explain one-third of the differential HIV prevalence among the cities of the Four City study. Conversely, we estimate that HIV had only a small net impact on HSV-2 prevalence.

Conclusions

HSV-2 role as a biological cofactor in HIV acquisition and transmission may have contributed substantially to HIV particularly by facilitating HIV spread among the low-risk population with stable long-term sexual partnerships. This finding suggests that prevention of HSV-2 infection through a prophylactic vaccine may be an effective intervention both in nascent epidemics with high HIV incidence in the high risk groups, and in established epidemics where a large portion of HIV transmission occurs in stable partnerships.     

Plant virus infection modifies plant pigment and manipulates the host preference behavior of an insect vector

Insect-borne plant viruses may modify the phenotype of their host plants and thus influence the responses of insect vectors. When a plant virus modifies host preference behavior of a vector, it can be expected to influence the rate of virus transmission. In this study, we examined the effect of Maize Iranian mosaic virus (MIMV) infection on host preference behavior of the nymphs and adults of its vector, the small brown planthopper, Laodelphax striatellus Fallén (Hemiptera: Delphacidae), feeding on barley plants (Hordeum vulgare L., Poaceae). We found that both viruliferous nymphs and adults significantly preferred healthy plants, whereas non-viruliferous planthoppers preferred virus-infected barley. Further investigations revealed significant reductions in the chlorophyll and carotenoid contents of infected barley leaves. Based on these results, a possible association between insect host preferences and the pigment contents of the plants was observed. In summary, we suggest that host preference of L. striatellus could be affected by the propagative plant virus, possibly through association of this modification with some phenotypic traits of infected plants. These effects may have a critical impact on MIMV transmission rate, with significant implications for the development of virus epidemics.     

Mycoplasma genitalium: an emerging cause of sexually transmitted disease in women

Mycoplasma genitalium is an emerging sexually transmitted pathogen implicated in urethritis in men and several inflammatory reproductive tract syndromes in women including cervicitis, pelvic inflammatory disease (PID), and infertility. This comprehensive review critically examines epidemiologic studies of M. genitalium infections in women with the goal of assessing the associations with reproductive tract disease and enhancing awareness of this emerging pathogen. Over 27,000 women from 48 published reports have been screened for M. genitalium urogenital infection in high- or low-risk populations worldwide with an overall prevalence of 7.3% and 2.0%, respectively. M. genitalium was present in the general population at rates between those of Chlamydia trachomatis and Neisseria gonorrhoeae. Considering more than 20 studies of lower tract inflammation, M. genitalium has been positively associated with urethritis, vaginal discharge, and microscopic signs of cervicitis and/or mucopurulent cervical discharge in seven of 14 studies. A consistent case definition of cervicitis is lacking and will be required for comprehensive understanding of these associations. Importantly, evidence for M. genitalium PID and infertility are quite convincing and indicate that a significant proportion of upper tract inflammation may be attributed to this elusive pathogen. Collectively, M. genitalium is highly prevalent in high- and low-risk populations, and should be considered an etiologic agent of select reproductive tract disease syndromes in women.     

The beneficial sexually transmitted microbe hypothesis of avian copulation

Several hypotheses have been proposed to explain why femalebirds either copulate repeatedly with a single mate or copulatewith multiple partners even though only a single copulationmay be sufficient to fertilize an entire clutch. We hypothesizethat females may directly benefit from high frequencies of copulationand multiple copulation partners if they receive a cloacal inoculationof beneficial sexually transmitted microbes (STMs) that caneither protect them against future encounters with pathogensand/or serve as therapy against present infections. Experimentsin domestic animal production, wildlife rehabilitation, andclinical medicine indicate that inoculations of beneficial microbesderived from the indigenous microflora of hosts can lead tonutritional benefits, resistance to colonization by pathogens,the elimination of infection, and improved immune system functioningin recipients. Our hypothesis predicts greater copulatory rateswhen the probability of the transmission of beneficial microbesexceeds that of pathogens and when the positive effects of beneficialmicrobes on host fitness exceed the negative effects of pathogens.Patterns of copulatory behavior in birds suggest the potentialutility of our hypothesis. We discuss our hypothesis in thecontext of observed patterns of copulation in birds and proposesome ways to directly test our hypothesis. Information on the probabilitiesof transmission during copulation of beneficial and pathogenic microbesand their relative potencies in birds are needed to directlytest the predictions of our hypothesis.