Dataset Information

Individual and population level effects of partner notification for Chlamydia trachomatis.

ABSTRACT: Partner notification (PN or contact tracing) is an important aspect of treating bacterial sexually transmitted infections (STIs), such as Chlamydia trachomatis. It facilitates the identification of new infected cases that can be treated through individual case management. PN also acts indirectly by limiting onward transmission in the general population. However, the impact of PN, both at the level of individuals and the population, remains unclear. Since it is difficult to study the effects of PN empirically, mathematical and computational models are useful tools for investigating its potential as a public health intervention. To this end, we developed an individual-based modeling framework called Rstisim. It allows the implementation of different models of STI transmission with various levels of complexity and the reconstruction of the complete dynamic sexual partnership network over any time period. A key feature of this framework is that we can trace an individual's partnership history in detail and investigate the outcome of different PN strategies for C. trachomatis. For individual case management, the results suggest that notifying three or more partners from the preceding 18 months yields substantial numbers of new cases. In contrast, the successful treatment of current partners is most important for preventing re-infection of index cases and reducing further transmission of C. trachomatis at the population level. The findings of this study demonstrate the difference between individual and population level outcomes of public health interventions for STIs.

SUBMITTER: Althaus CL

PROVIDER: S-EPMC3520891 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Individual and population level effects of partner notification for Chlamydia trachomatis.

Althaus Christian L CL Heijne Janneke C M JC Herzog Sereina A SA Roellin Adrian A Low Nicola N

PloS one 20121212 12

Partner notification (PN or contact tracing) is an important aspect of treating bacterial sexually transmitted infections (STIs), such as Chlamydia trachomatis. It facilitates the identification of new infected cases that can be treated through individual case management. PN also acts indirectly by limiting onward transmission in the general population. However, the impact of PN, both at the level of individuals and the population, remains unclear. Since it is difficult to study the effects of P ...[more]

PMID: 23251534

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Project description:BackgroundExpedited partner therapy (EPT), the practice of treating the sex partners of persons with sexually transmitted infections without their medical evaluation, increases partner treatment and decreases gonorrhea and chlamydia reinfection rates. We conducted a stepped-wedge, community-level randomized trial to determine whether a public health intervention promoting EPT could increase its use and decrease chlamydia test positivity and gonorrhea incidence in women.Methods and findingsThe trial randomly assigned local health jurisdictions (LHJs) in Washington State, US, into four study waves. Waves instituted the intervention in randomly assigned order at intervals of 6-8 mo. Of the state's 25 LHJs, 24 were eligible and 23 participated. Heterosexual individuals with gonorrhea or chlamydial infection were eligible for the intervention. The study made free patient-delivered partner therapy (PDPT) available to clinicians, and provided public health partner services based on clinician referral. The main study outcomes were chlamydia test positivity among women ages 14-25 y in 219 sentinel clinics, and incidence of reported gonorrhea in women, both measured at the community level. Receipt of PDPT from clinicians was evaluated among randomly selected patients. 23 and 22 LHJs provided data on gonorrhea and chlamydia outcomes, respectively. The intervention increased the percentage of persons receiving PDPT from clinicians (from 18% to 34%, p < 0.001) and the percentage receiving partner services (from 25% to 45%, p < 0.001). Chlamydia test positivity and gonorrhea incidence in women decreased over the study period, from 8.2% to 6.5% and from 59.6 to 26.4 per 100,000, respectively. After adjusting for temporal trends, the intervention was associated with an approximately 10% reduction in both chlamydia positivity and gonorrhea incidence, though the confidence bounds on these outcomes both crossed one (chlamydia positivity prevalence ratio = 0.89, 95% CI 0.77-1.04, p = 0.15; gonorrhea incidence rate ratio = 0.91, 95% CI .71-1.16, p = 0.45). Study findings were potentially limited by inadequate statistical power, by the institution of some aspects of the study intervention outside of the research randomization sequence, and by the fact that LHJs did not constitute truly isolated sexual networks.ConclusionsA public health intervention promoting the use of free PDPT substantially increased its use and may have resulted in decreased chlamydial and gonococcal infections at the population level.Trial registrationClinicalTrials.gov NCT01665690.

Project description:IntroductionPartner notification (PN) is a process aiming to identify, test and treat the sex partners of people (index patients) with sexually transmitted infections (STIs). Accelerated partner therapy (APT) is a PN method whereby healthcare professionals assess sex partners, by telephone consultation, before giving the index patient antibiotics and STI self-sampling kits to deliver to their sex partner(s). The Limiting Undetected Sexually Transmitted infections to RedUce Morbidity programme aims to determine the effectiveness of APT in heterosexual women and men with chlamydia and determine whether APT could affect Chlamydia trachomatis transmission at population level.Methods and analysisThis protocol describes a cross-over cluster randomised controlled trial of APT, offered as an additional PN method, compared with standard PN. The trial is accompanied by an economic evaluation, transmission dynamic modelling and a qualitative process evaluation involving patients, partners and healthcare professionals. Clusters are 17 sexual health clinics in areas of England and Scotland with contrasting patient demographics. We will recruit 5440 heterosexual women and men with chlamydia, aged ≥16 years.The primary outcome is the proportion of index patients testing positive for C. trachomatis 12-16 weeks after the PN consultation. Secondary outcomes include: proportion of sex partners treated; cost effectiveness; model-predicted chlamydia prevalence; experiences of APT.The primary outcome analysis will be by intention-to-treat, fitting random effects logistic regression models that account for clustering of index patients within clinics and trial periods. The transmission dynamic model will be used to predict change in chlamydia prevalence following APT. The economic evaluation will use mathematical modelling outputs, taking a health service perspective. Qualitative data will be analysed using interpretative phenomenological analysis and framework analysis.Ethics and disseminationThis protocol received ethical approval from London-Chelsea Research Ethics Committee (18/LO/0773). Findings will be published with open access licences.Trial registration numberISRCTN15996256.

Project description:The large number of sexually transmitted diseases and ocular trachoma cases that are caused globally each year by Chlamydia trachomatis has made this organism a World Health Organization priority for vaccine development. However, there is no gene transfer system for Chlamydia to help identify potential vaccine targets. To accelerate discoveries toward this goal, here we analyzed the broadest diversity of C. trachomatis genomes to date, including 25 geographically dispersed clinical and seven reference strains representing 14 of the 19 known serotypes. Strikingly, all 32 genomes were found to have evidence of DNA acquisition by homologous recombination in their history. Four distinct clades were identified, which correspond to all C. trachomatis disease phenotypes: lymphogranuloma venereum (LGV; Clade 1); noninvasive urogenital infections (Clade 2); ocular trachoma (Clade 3); and protocolitis (Clade 4; also includes some noninvasive urogenital infections). Although the ancestral relationship between clades varied, most strains acted as donor and recipient of recombination with no evidence for barriers to genetic exchange. The niche-specific LGV and trachoma clades have undergone less recombination, although the opportunity for mixing with strains from other clades that infect the rectal and ocular mucosa, respectively, is evident. Furthermore, there are numerous occasions for gene conversion events through sequential infections at the same anatomic sites. The size of recombinant segments is relatively small (~357 bp) compared with in vitro experiments of various C. trachomatis strains but is consistent with in vitro estimates for other bacterial species including Escherichia coli and Helicobacter pylori. Selection has also played a crucial role during the diversification of the organism. Clade 2 had the lowest nonsynonymous to synonymous ratio (dN/dS) but the highest effect of recombination, which is consistent with the widespread occurrence of synonymous substitutions in recombined genomic segments. The trachoma Clade 3 had the highest dN/dS estimates, which may be caused by an increased effect of genetic drift from niche specialization and a reduced effective population size. The degree of drift, selection, and recombination in C. trachomatis suggests that the challenge will remain to identify genomic regions that are stable and cross protective for the development of an efficacious vaccine.

Project description:It is hard to convince people to participate in chlamydia screening programs outside the clinical setting. In two earlier studies (BMC Public Health. 2013;13:1091; J Med Internet Res. 2014;16(1):e24), we identified explicit and implicit determinants of chlamydia screening behavior and attempted, unsuccessfully, to improve participation rates by optimizing the recruitment letter. In the present study, we examined the links between a number of social-cognitive determinants (e.g., stereotypical beliefs about a person with chlamydia, intentions, changes in partner status), and self-reported chlamydia testing behavior six months after the initial study.The present study is a follow-up to our first study (T0). We assessed self-reported testing behavior 6 months after the first measure by means of an online questionnaire (T1; N = 269). Furthermore, at T1, we measured the social-cognitive determinants in more detail, and explored the influence of stereotypical beliefs and any changes in partner status during this six month period.In total, 25 (9.1 %) of the participants tested for chlamydia at some point during the six months between baseline (T0) and follow up (T1). Testing behavior was influenced by testing intentions in combination with changes in risk behavior. The higher the participants' own numbers of partners ever, the higher they estimated the number of partners of the stereotypical person with chlamydia. Testing intentions were most strongly predicted by perceived norms and susceptibility, and having had multiple partners in the last 6 months (R(2) = .41).The most relevant determinants for testing intentions and behavior were susceptibility, subjective norms and changes in partner status. We found a systematic tendency for individuals to underestimate their own risk, especially the risk of inconsistent condom use. Future research should focus on more promising alternatives to population-based interventions, such as online interventions, screening in primary care, the rescreening of positives, and clinic-based interventions. This future research should also focus on making testing easier and reducing barriers to testing, as well as using social and sexual networks in order to reach more people.

Dataset Information

Individual and population level effects of partner notification for Chlamydia trachomatis.

Publications

Individual and population level effects of partner notification for Chlamydia trachomatis.

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