Collective decision-making appears more egalitarian in populations where group fission costs are higher.

Collective decision-making is predicted to be more egalitarian in conditions where the costs of group fission are higher. Here, we ask whether Trinidadian guppies (Poecilia reticulata) living in high or low predation environments, and thereby facing differential group fission costs, make collective decisions in line with this prediction. Using a classic decision-making scenario, we found that fish from high predation environments switched their positions within groups more frequently than fish from low predation environments. Because the relative positions individuals adopt in moving groups can influence their contribution towards group decisions, increased positional switching appears to support the prediction of more evenly distributed decision-making in populations where group fission costs are higher. In an agent-based model, we further identified that more frequent, asynchronous updating of individuals' positions could explain increased positional switching, as was observed in fish from high predation environments. Our results are consistent with theoretical predictions about the structure of collective decision-making and the adaptability of social decision-rules in the face of different environmental contexts.

Concentrated and linked epidemics of both HSV-2 and HIV-1/HIV-2 infections in Senegal: public health impacts of the spread of HIV.

The objective of this article is to report seroprevalences on HIV and herpes simplex virus 2 (HSV-2) in female sex workers (FSW) and in two sentinel populations of pregnant women living in Senegal. Serosurveys of HIV and HSV-2 were conducted in two unselected sentinel populations from Dakar, Senegal, and its provinces, including in 2003 only pregnant women and 2006 pregnant women and FSW. The population study involved 888 pregnant women and 604 FSW. In pregnant women, HIV and HSV-2 seroprevalences were, respectively, 1.01% and 15.65%. There was no association between HSV-2 and HIV infection, whatever the age. In contrast, the seroprevalence of HIV infection in the group of FSW was high, reaching 22.9% in women over 30 years old. FSW above 20 years of age harboured much higher HSV-2 seroprevalences that those found in pregnant women of similar age groups. In FSW, strong associations between HSV-2 and age, and among HSV-2 and HIV-1 as well HIV-2, were evidenced. In conclusion, HIV epidemic remains concentrated in high-risk groups of the Senegalese population, such as the FSW population in which the seroprevalence of HSV-2 infection is very high. Intervention against STI including HSV-2 is urgently needed to prevent the spreading of HIV epidemic.

[Decentralization of the immunological monitoring of people living with HIV/AIDS in a limiting setting with a low HIV seroprevalence: the experience of Senegal]. / Décentralisation du suivi immunologique des personnes vivant avec le VIH dans un pays à ressources limitées et à prévalence faible: expérience du Sénégal.

Our work aimed to propose a manual method of counting CD4 T lymphocytes which is an alternative magnetic immunoseparation followed by a reading with a fluorescence microscope as an alternative to the automated flow cytometry. This alternative technique is easier for use, less expensive and could answer the difficulties encountered for the monitoring CD4 T cells count in developing countries. The specific objectives were: 1) to train the technicians of the peripheral sites in order to make the numeration of the CD4 T lymphocytes more accessible at the peripheral level; 2) to equip the sites with necessary facilities for the T lymphocytes CD4 count; 3) to put in place a system of quality control permitting the reliability of the results. A hundred and fifty patients have been enrolled in three care services for people living with HIV/AIDS in Dakar. This population was constituted of 119 seropositive and 31 seronegative patients acting as control group to have some patients with high rates of T lymphocytes CD4. For the follow-up at peripheral level, the patients were constituted of the active line of the patients living with HIV/AIDS supported in the targeted sites. The measurements allowed studying concordances for different rates of lymphocytes: 0 to 199, 200 to 499 and over 500 cells by mm3. The results showed also a very good correlation (r = 0.97 or r = 0.98 according to the operator) between the two methods for CD4 rates inferior to 500 cells by mm3 among both the negative group and the HIV positive patients. We also discussed the profit of decentralization for the program and the patient, as well as the setting up of an external quality control to validate the alternative technique. According to the results, the Dynabeads is well correlated with the Facscount. It is a technique that can be used as an alternative in the zones with limited resources, low prevalence and for a small number of samples.

Qualitative changes in AIDS preventative attitudes in a rural Senegalese population.

Recent changes in knowledge and attitudes towards AIDS in a rural population of Senegal were assessed comparing two cross-sectional studies conducted six years apart (1997 and 2003). Random samples of 866 and 709 adults aged 15-59 were included. Sociodemographic characteristics of the two population samples were very similar. The proportion of those who estimated their personal risk of being infected by HIV as high or very high fell from 49.1% in 1997 to 17.2% in 2003. The proportion of those who reported having already changed their behaviour to protect themselves from AIDS fell from 56.3% to 24.9%. Methods cited as protection against HIV changed over the period. Fidelity and/or partner selection was cited by 93% of respondents in 1997 and 58% in 2003 when suspicion of potentially soiled materials appeared. Finally, attitudes towards persons living with HIV or AIDS (PLWHA) in 2003 were ambivalent: while 73.9% thought that a PLWHA should not be allowed to mix with other villagers, 65.1% would be ready to provide care to a PLWHA. Drastic changes in attitudes towards the AIDS threat could be identified over the period. AIDS preventive attitudes measured in 1997 were not sustained in 2003, while stigmatization of PLWHA was very widespread.

Prevention of HIV and other STIs in rural Senegal: a study of prevention-related events collected by sentinel observers.

We conducted a study of AIDS/STI prevention-related events based on a network of sentinel observers over a 35-month period in three rural communities of Senegal (May 2000 - March 2003). In one of these communities we also conducted a population-based study on self-reported prevention events and attitudes towards AIDS. Sentinel observers recorded 1 590 AIDS/STI prevention-related events. More than half of the reported events were radio programmes. The proportion of events on the occasion of which therapies was addressed increased significantly between 2000 and 2001, from less than 3% to about 10%, while sharp decreases in the proportion of events dealing with condoms and STIs, both from around 25% to less than 15%, were observed at the same time. The population-based survey indicated that men were more influenced by individual events like informal discussions or radio programmes while women seemed to be more influenced by collective events such as public meetings and school education.

[Effectiveness of syndromic approach for management of urethral discharge in Senegal]. / Evaluation de l'efficacité du traitement des écoulements urétraux au Sénégal selon l'approche syndromique.

The World Health Organization has proposed the syndromic approach for management of sexually transmissible diseases (STD) in countries where diagnostic laboratory tests are not consistently available. The purpose of this study was to evaluate the effectiveness of this approach for treatment of ureteral discharge in Senegal. Twenty seven men presenting ureteral discharge underwent two-week treatment using a combination of cotrimoxazole plus tetracycline for suspected gonococcal and a chlamydial infections. Ureteral samples were collected before and after treatment to detect Neisseria gonorrhoeae by culture and Chlamydia trachomatis by direct immunofluorescence and ELISA. Results demonstrated successful treatment of all patients presenting gonococcal and chlamydial infections i.e. 84.6% of cases. Neither germ was detected in 15.4% of cases. Before treatment, Neisseria gonorrhoeae, Chlamydia trachomatis or both were found respectively in 53.9%, 5.1% and 25.6% of samples respectively. Based on these findings we conclude that the syndromic approach was effective in 84.6% of cases but treatment was in adequation with STD biologically documented only with 25.6% of cases.