Pair approximation for a model of vertical and horizontal transmission of parasites.

We apply Stochastic Dynamics method for a differential equations model, proposed by Marc Lipsitch and collaborators (Proc. R. Soc. Lond. B 260, 321, 1995), for which the transmission dynamics of parasites occurs from a parent to its offspring (vertical transmission), and by contact with infected host (horizontal transmission). Herpes, Hepatitis and AIDS are examples of diseases for which both horizontal and vertical transmission occur simultaneously during the virus spreading. Understanding the role of each type of transmission in the infection prevalence on a susceptible host population may provide some information about the factors that contribute for the eradication and/or control of those diseases. We present a pair mean-field approximation obtained from the master equation of the model. The pair approximation is formed by the differential equations of the susceptible and infected population densities and the differential equations of pairs that contribute to the former ones. In terms of the model parameters, we obtain the conditions that lead to the disease eradication, and set up the phase diagram based on the local stability analysis of fixed points. We also perform Monte Carlo simulations of the model on complete graphs and Erdös-Rényi graphs in order to investigate the influence of population size and neighborhood on the previous mean-field results; by this way, we also expect to evaluate the contribution of vertical and horizontal transmission on the elimination of parasite. Pair Approximation for a Model of Vertical and Horizontal Transmission of Parasites.

Sexual abuse victimisation and perpetration in a cohort of men living with HIV/AIDS who have sex with women from Sao Paulo, Brazil

Sexual abuse leads to physical harm and devastating psychosocial consequences. It increases risk of HIV transmission and is associated with risky behaviour. Little is known about sexual abuse victimisation (SAV) and perpetration (SAP) among HIV-positive men who have sex with women (MSW). We investigated self-reported SAV and SAP among 242 Brazilian MSW selected at HIV care centres. Patients were questioned about sociodemographic data, mode of HIV acquisition, sexual practices, drug use and history of SAV or SAP. Prevalence of outcomes was estimated and risk factors for SAP investigated by logistic regression. Fifty-eight (24.1%) interviewees reported SAV. Of patients abused before 15 years of age, 64.3% reported events before the age of ten. Aggressors included relatives, friends and teachers. Among those victimised after 15 years old, 57.7% described events before 17 and 38.5% had acquainted aggressors. Fourteen (5.8%) interviewees reported SAP and most knew their victims. Sexual abuse perpetration was associated with lower schooling, marital status, illicit drug use and self-reported SAV. Sexual abuse was frequently reported by MSW from this cohort. Identifying predictors of violence and addressing SAV and SAP in comprehensive HIV care may help reduce violent behaviour, psychological distress and contribute to maximise benefits of preventive and care interventions.

Monitoring Drug Use Among HIV/AIDS Patients in Brazil: Should we Combine Self-Report and Urinalysis?

Illicit drug use in HIV-infected patients can be linked to impairment of physical and mental health, low health-related quality of life, and suboptimal adherence to HIV treatment. This study aimed to evaluate the correlation of self-report illicit drug use, urinalysis for cocaine and cannabis metabolites, and severity of dependence among HIV-infected patients on antiretroviral therapy (ART) in a treatment center in Brazil. Four hundred and thirty-eight outpatients of an HIV referral center were interviewed and assessed for drug use (lifetime, last year and last month). Urinalysis was performed to detect the presence of cocaine and cannabis metabolites in urine samples. Overall agreement between self-report and urinalysis was almost 68% for cannabis and higher than 85% for cocaine. Positive urinalysis was significantly associated with more than once a week cannabis (p < .0001) and cocaine (p <.0001) use during the last-month. Severity of Dependence Scale (SDS) properly predicted positive cocaine urinalysis results (area under the curve [AUC] = .81, p = .0001). Frequency of cannabis and cocaine use, SDS score degree and positive urinalysis for both drugs were correlated. Our findings suggest that positive self-report is a reliable predictor of positive urine sample both for cannabis and cocaine, but since the agreement was not perfect, there is a role for urine drug screening in the care of patients with HIV-related conditions.

Association between muscle strength and the cardiopulmonary status of individuals living with HIV/AIDS

OBJECTIVE: The purpose of this study was to compare aerobic function [anaerobic threshold (%_VVO2-AT), respiratory compensation point (%_VVO2-RCP) and peak oxygen uptake (_VVO2peak)] between physically active patients with HIV/AIDS and matched controls and to examine associations between disease status, poor muscle strength, depression (as estimated by the profile of mood states questionnaire) and the aerobic performance of patients. METHODS: Progressive treadmill test data for %_VVO2-AT (V-slope method), RCP and (_VVO2peak) were compared between 39 male patients with HIV/AIDS (age 40.6¡1.4 years) and 28 male controls (age 44.4¡2.1 years) drawn from the same community and matched for habitual physical activity. Within-patient data were also examined in relation to CD4+ counts (nadir and current data) and peak isokinetic knee torque. RESULTS: AT, RCP and (_VVO2peak) values were generally similar for patients and controls.Within the patient sample, binary classification suggested that AT, RCP and (_VVO2peak) values were not associated with either the nadir or current CD4+ count, but treadmill test variables were positively associated with peak isokinetic knee torque. CONCLUSION: The aerobic performance of physically active patients with HIV/AIDS is generally well conserved. Nevertheless, poor muscle strength is observed in some HIV/AIDS patients, which is associated with lower anaerobic power and (_VVO2peak), suggesting the possibility of enhancing the aerobic performance of patients with weak muscles through appropriate muscle-strengthening activities.