The use of remote imagery captured by unmanned aerial vehicles (UAV) has tremendous potential for designing detailed site-specific weed control treatments in early post-emergence, which have not possible previously with conventional airborne or satellite images. A robust and entirely automatic object-based image analysis (OBIA) procedure was developed on a series of UAV images using a six-band multispectral camera (visible and near-infrared range) with the ultimate objective of generating a weed map in an experimental maize field in Spain. The OBIA procedure combines several contextual, hierarchical and object-based features and consists of three consecutive phases: 1) classification of crop rows by application of a dynamic and auto-adaptive classification approach, 2) discrimination of crops and weeds on the basis of their relative positions with reference to the crop rows, and 3) generation of a weed infestation map in a grid structure. The estimation of weed coverage from the image analysis yielded satisfactory results. The relationship of estimated versus observed weed densities had a coefficient of determination of r(2)=0.89 and a root mean square error of 0.02. A map of three categories of weed coverage was produced with 86% of overall accuracy. In the experimental field, the area free of weeds was 23%, and the area with low weed coverage (<5% weeds) was 47%, which indicated a high potential for reducing herbicide application or other weed operations. The OBIA procedure computes multiple data and statistics derived from the classification outputs, which permits calculation of herbicide requirements and estimation of the overall cost of weed management operations in advance.

Objectives

Syphilis is endemic among men who have sex with men (MSM) and transgender women in Latin America. The objective of this study was to assess if those who screen positive for syphilis are receiving appropriate care and treatment.

Methods

We use data from the 2011 Peruvian National HIV Sentinel Surveillance to describe the syphilis care cascade among high-risk MSM and transgender women. Medical records from participants who had a positive syphilis screening test at two of the enrolment sites in Lima were reviewed to determine their subsequent course of care.

Results

We identified a cohort of 314 syphilis seropositive participants (median age: 30, 33.7% self-identified as transgender). Only 284/314 (90.4%) participants saw a physician for evaluation within 28 days of their positive test. Of these, 72/284 (25.4%) were asked to return for confirmatory results before deciding whether or not to start treatment; however, 45/72 (62.5%) of these participants did not follow up within 28 days. Of the people prescribed three weekly doses of penicillin, 34/63 (54%) received all three doses on time.

Conclusions

Many MSM and transgender women with a positive syphilis screening test are lost at various steps along the syphilis care cascade and may have persistent infection. Interventions in this population are needed to increase testing, link seropositive patients into care and ensure that they receive appropriate and timely treatment.

BACKGROUND: Partnership type is an important factor associated with unprotected anal intercourse (UAI) and subsequent risk for HIV and sexually transmitted infections (STI). We examined the association of partnership type with UAI among men who have sex with men (MSM) and male-to-female transgender women (TGW) in Lima, Peru, recently diagnosed with HIV and/or STI. METHODS: We report data from a cross-sectional analysis of MSM and TGW recently diagnosed with HIV and/or STI in Lima, Peru between 2011 and 2012. We surveyed participants regarding UAI with up to their three most recent sexual partners according to partner type. Multivariable Generalized Estimate Equating (GEE) models with Poisson distribution were used to estimate prevalence ratios (PR) for UAI according to partner type. RESULTS: Among 339 MSM and TGW recently diagnosed with HIV and/or STI (mean age: 30.6 years, SD 9.0), 65.5% self-identified as homosexual/gay, 16.0% as bisexual, 15.2% as male-to-female transgender, and 3.3% as heterosexual. Participants provided information on 893 recent male or TGW partners with whom they had engaged in insertive or receptive anal intercourse: 28.9% stable partners, 56.4% non-stable/non-transactional partners (i.e. casual or anonymous), and 14.7% transactional partners (i.e. transactional sex client or sex worker). Unprotected anal intercourse was reported with 41.3% of all partners. In multivariable analysis, factors associated with UAI included partnership type (non-stable/non-transactional partner APR 0.73, [95% CI 0.59-0.91], transactional partner APR 0.53 [0.36-0.78], p<0.05) and the number of previous sexual encounters with the partner (>10 encounters APR 1.43 [1.06-1.92], p<0.05). CONCLUSION: UAI was more commonly reported for stable partners and in partnerships with >10 sexual encounters, suggesting UAI is more prevalent in partnerships with a greater degree of interpersonal commitment. Further research assessing partner-level factors and behavior is critical for improving HIV and/or STI prevention efforts among Peruvian MSM and TGW.

Cry proteins from Bacillus thuringiensis are insecticidal PFTs (pore-forming toxins). In the present study, we show that two distinct functional pre-pores of Cry1Ab are formed after binding of the protoxin or the protease-activated toxin to the cadherin receptor, but before membrane insertion. Both pre-pores actively induce pore formation, although with different characteristics, and contribute to the insecticidal activity. We also analysed the oligomerization of the mutant Cry1AbMod protein. This mutant kills different insect populations that are resistant to Cry toxins, but lost potency against susceptible insects. We found that the Cry1AbMod-protoxin efficiently induces oligomerization, but not the activated Cry1AbMod-toxin, explaining the loss of potency of Cry1AbMod against susceptible insects. These data are relevant for the future control of insects resistant to Cry proteins. Our data support the pore-formation model involving sequential interaction with different midgut proteins, leading to pore formation in the target membrane. We propose that not only different insect targets could have different receptors, but also different midgut proteases that would influence the rate of protoxin/toxin activation. It is possible that the two pre-pore structures could have been selected for in evolution, since they have differential roles in toxicity against selected targets, increasing their range of action. These data assign a functional role for the protoxin fragment of Cry PFTs that was not understood previously. Most PFTs produced by other bacteria are secreted as protoxins that require activation before oligomerization, to finally form a pore. Thus different pre-pores could be also part of the general mechanism of action of other PFTs.

Background

New strategies to support partner notification (PN) are critical for STD control and require detailed understanding of how specific individual and partnership characteristics guide notification decisions.

Methods

From 2011 to 2012, 397 MSM and TW recently diagnosed with HIV, syphilis, or another STD completed a survey on anticipated notification of recent sexual partners and associated factors. Qualitative interviews were conducted with a subset of participants to provide further depth to quantitative findings. Prevalence ratios and generalized estimating equation (GEE) models were used to analyze participant- and partner-level factors associated with anticipated PN.

Results

Among all partners reported, 52.5% were described as "Very Likely" or "Somewhat Likely" to be notified. Anticipated notification was more likely for main partners than casual (adjusted Prevalence Ratio [aPR], 95% CI: 0.63, 0.54-0.75) or commercial (aPR, 95% CI: 0.44, 0.31-0.62) partners. Other factors associated with likely notification included perception of the partner as an STD source (aPR, 95% CI: 1.27, 1.10-1.48) and anticipated future sexual contact with the partner (aPR, 95% CI: 1.30, 1.11-1.52). An HIV diagnosis was associated with a lower likelihood of notification than non-HIV STDs (aPR: 0.68, 0.55-0.86). Qualitative discussion of the barriers and incentives to PN reflected a similar differentiation of anticipated notification according to partnership type and type of HIV/STD diagnosis.

Discussion

Detailed attention to how partnership characteristics guide notification outcomes is essential to the development of new PN strategies. By accurately and thoroughly assessing the diversity of partnership interactions among individuals with HIV/STD, new notification techniques can be tailored to partner-specific circumstances.

Background

We explored the association between alcohol use and condomless receptive (CRAI) and insertive (CIAI) anal intercourse within partnership contexts of men who have sex with men (MSM) and transgender women (TGW) in Lima, Peru.

Methods

From 2012-2014, we surveyed men and TGW (n=1607) who reported anal intercourse with ≥1 male or TGW. Alcohol use with up to 3 sexual partners during the prior 90days was evaluated. Bivariate and multivariate analyses used generalized estimating equations to assess event-level associations between alcohol use, CRAI, CIAI, and partnership characteristics while adjusting for participant clustering from multiple partners.

Results

Of 4774 sexual partnerships reported, 48% were casual, 34% primary, 10% anonymous, and 8% commercial. Alcohol use preceding sex was significantly (p<0.05) associated with CRAI (PR=1.26) and CIAI (PR=1.37). Partnership characteristics significantly associated with alcohol use included commercial sex work (PR=2.21) and trended (p<0.10) towards alcohol use with casual (PR=1.16), transgender (PR=1.48), and moderno ("versatile"; PR=1.17) partners. CRAI and CIAI were more common among participants who reported knowing they (PR=1.52; PR=1.41, respectively) or their partner (PR=1.47; PR=1.44, respectively) was HIV-uninfected. Yet, only CIAI (PR=1.42) was more commonly reported with known HIV-infected partners. Participants who drank alcohol prior to sex were less likely to know their partner's HIV serostatus.

Conclusions

Alcohol use prior to intercourse was associated with CRAI and CIAI, varied by partnership type, and may impair knowledge of partner HIV serostatus. Detailed knowledge of alcohol use within partner-specific contexts is essential for informing condom-based and alternative HIV prevention strategies for MSM and TGW in Peru.

Bacillus thuringiensis (Bt) Cyt1Aa toxin shows toxicity to mosquitoes, to certain coleopteran pests and also to red blood cells (RBC). However, its mode of action in the different target cells is not well defined. This protein is a single α-β domain pore-forming toxin, where a β sheet is wrapped by two α-helices layers. The Cyt1Aa α-helix hairpin in the N-terminal has been proposed to be involved in initial membrane binding and oligomerization, while the β sheet inserts into the membrane to form a pore that lyze the cells. To determine the role of the N-terminal α-helix hairpin region of Cyt1Aa in its mode of action, we characterized different single point mutations located in helices α-1 and α-2. Eight cysteine substitutions in different residues were produced in Bt, and we found that three of them: Cyt1AaA65C, Cyt1AaL85C and Cyt1AaN89C, lost insecticidal toxicity against Aedes aegypti larvae but retained similar or increased hemolytic activity towards rabbit RBC. Analysis of toxin binding and oligomerization using Ae. aegypti midgut brush border membrane vesicles showed that the three Cyt1Aa mutants non-toxic to Ae. aegypti were affected in oligomerization. However, these mutants were still hemolytic. Our data shows that oligomerization of Cyt1Aa toxin is essential for its toxicity to Ae. aegypti but not for its toxicity against RBC indicating that the mode of action of Cyt1Aa is different in these distinct target membranes.

Background: Binge drinking (BD) is common in Peru, but may not be routinely detected by standard assessments of hazardous drinking. Objectives: We describe prevalence and risk behaviors of men who have sex with men (MSM) and transgender women (TW) in Peru who met criteria for BD as compared with those who met criteria for hazardous drinking. Methods: In a cross-sectional sample of MSM and TW from Lima (2012-2014), we calculated prevalence of BD (consuming ≥6 alcoholic drinks per occasion by AUDIT-3 criteria), conducted bivariate analyses of associations of BD with demographic and behavioral characteristics, and compared prevalence and behaviors of BD to those of hazardous drinkers (identified by AUDIT-10 criteria). Results: Of 1,520 MSM (n = 1,384) and TW (n = 137) with median age 27 years, 74.4% of MSM and 86.9% of TW met criteria for BD. Among MSM, BD was associated with a greater likelihood of using alcohol (41.6% vs. 13.8%; p < .01) or drugs (7.8% vs. 2.8%; p < .01) prior to a recent sexual contact. Among TW, BD was associated with greater frequency of alcohol use (44.9% vs. 11.1%; p < .01) or unprotected anal intercourse (58.8% vs. 33.3%; p = .04) during ≥1 of their three most recent sexual contacts. There was a higher prevalence of BD (75.5%) than hazardous drinking (53.2%) in our sample, with binge drinkers exhibiting similar sexual risk behaviors to hazardous drinkers. Conclusions: Binge drinking is common among MSM and TW in Lima, associated with risky sexual behavior, and may not be adequately captured by AUDIT-10 criteria.

Objectives

Partner notification (PN) following sexually transmitted disease (STI) diagnosis is a key strategy for controlling HIV/STI transmission. Anonymous partnerships are an important barrier to PN and often associated with high-risk sexual behaviour. Limited research has examined the profile of men who have sex with men (MSM) and transgender women (TW) who engage in anonymous sex. To better understand anonymous partnership practices in Lima, Peru, we assessed participant-level and partnership-level characteristics associated with anonymous sex among a sample of MSM and TW recently diagnosed with HIV/STI.

Methods

MSM and TW diagnosed with HIV/STI within the past month completed a cross-sectional survey regarding anticipated PN practices. Participants reported sexual partnership types and characteristics of up to three of their most recent partners. Using a Poisson generalised estimating equation model, we assessed participant-level and partnership-level characteristics associated with anonymous partnerships.

Results

Among 395 MSM and TW with HIV/STI, 36.0% reported at least one anonymous sexual partner in the past 3 months (mean of 8.6 anonymous partners per participant; SD 17.0). Of the 971 partnerships reported, 118 (12.2%) were anonymous and the majority (84.8%) were with male partners, followed by 11.0% with female partners and 4.2% with transgender/travesti partners. Partner-level characteristics associated with increased likelihood of having an anonymous partner included female (adjusted prevalence ratio (aPR) 2.28, 95% CI 1.05 to 4.95, p=0.04) or transgender/travesti (aPR 4.03, 95% CI 1.51 to 10.78, p=0.006) partner gender.

Conclusions

By assessing both individual-level and dyadic-level factors, these results represent an important step in understanding the complexity of partnership interactions and developing alternative PN strategies for Latin America.