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Background Zoonotic pathogens respond to changes in host range and/or pathogen, vector and host ecology. Environmental changes (biodiversity, habitat changes, variability in climate), even at a local level, lead to variability in environmental pathogen dynamics and can facilitate their transmission from natural reservoirs to new susceptible hosts. Whilst the environmental dynamics of aquatic bacteria are directly linked to seasonal changes of their habitat they also rely on the ecological processes underpining their transmission. However data allowing the comparison of these ecological processes are lacking. Here we compared the environmental dynamics of generalist and vector-borne aquatic bacterial pathogens in the same unit of time and space, and across rural and urban habitats in French Guiana (South America). Principal findings Using Leptospira sp. and Mycobacterium ulcerans we performed an environmental survey that allowed the detection of both pathogens in urban vs. rural areas, and during rainy vs. dry weather conditions. All samples were subjected to qPCR amplifications of LipL32 (Leptospira sp.) and IS2404 and KR (M. ulcerans) genetic markers. We found (i) a greater presence of M. ulcerans in rural areas compared with Leptospira sp., (ii) that modified urban environments were more favourable to the establishment of both pathogens, (iii) that Leptospira sp. presence was enhanced during the rainy season and M. ulcerans during the dry period, and (iv) differences in the spatial distribution of both bacteria across urban sites, probably due to the mode of dissemination of each pathogen in the environment. Conclusions We propose that in French Guiana simplified and modified urban ecosystems might favour leptospirosis and Buruli ulcer emergence and transmission. Moreover, disease risk was also constrained by seasonality. We suggest that the prevention of aquatic bacterial disease emergence in impoverished urban areas of developing countries would benefit from seasonal diseases targeted surveys, which would maximise limited budgets from cash-strapped health agencies., Author summary Many emerging pathogens are zoonotic and transmit from their abiotic reservoir to wild animals, domesticated animals and humans. It is now well known that environmental changes lead to variability in their dynamics in the environment and contribute to changes in the infectious risk. Many aquatic bacteria are responsable for major public health concerns, and more importantly in developing countries where access to drinking-water and sanitation is often limited. Whilst their environmental dynamics are directly linked to seasonal changes of their habitat, they also rely on the ecological processes underpining their transmission, i.e. directly transmitted vs. vector-borne. However, few studies have compared such environmental dynamics despite the fact that it would help to better characterise the infectious risk in the environment, as well as to better monitor the emergence of infectious diseases. Our aim was to provide data on the prevalence of generalist vs. vector-borne aquatic bacterial pathogens in the environment that would further allow the comparison of their environmental dynamics in the same unit of time and space, and across rural and urban habitats. We showed that urbanization and seasonality are two important factors underlying Buruli ulcer and leptospirosis disease emergence in French Guiana (South America), and propose that the mode of transmission of such environmental pathogens might have a detrimental role in disseminating the infectious agent in the environment.

International audience; BACKGROUND:The preventive treatment of Plasmodium vivax relapse recommended by the World Health Organization is primaquine at a dose of 15 mg/day for 14 days, except for malaria cases from Asia and Oceania. Since 2006, CDC recommends the use of primaquine at 30 mg/day for 14 days. In France, all cases of malaria due to P. vivax are treated with 30 mg of primaquine. This systematically increased dosage needs to be evaluated according to epidemiological context. The aim of the study was to compare relapses after 14 days of primaquine at 15 or 30 mg/day.METHODS:All patients treated with primaquine after a vivax malaria episode in French Guiana, between 1 January, 2007 and 1 August, 2016, were studied. Based on the compulsory hospital pharmacy forms for primaquine delivery, adult patients who received 15 or 30 mg of primaquine during 14 days for hypnozoite eradication were included. The recommended dose was initially 15 mg and was changed to 30 mg in 2011. Vivax malaria recurrences within 2 months after primaquine treatment, and vivax malaria recurrences 2-6 months after primaquine in each treatment group were analysed using survival analysis at 2, 3 and 6 months.RESULTS:Out of 544 patients included, 283 received 15 mg/day and 261 received 30 mg/day of primaquine. At 2 and 3 months after primaquine treatment, the number of recurrences was 7 (2.5%) and 19 (7.3%), and 9 (3.4%) and 15 (5.3%), in the 15 and 30 mg groups (p = 0.51 respectively 0.35), respectively. Within 3 months, the median time to recurrence was 2.05 months in the 15 and 30 mg groups. At 6 months after primaquine treatment, the number of recurrences was 25 (8.8%) and 31 (11.9%) at 15 and 30 mg, respectively (p = 0.24). The median time to recurrence was 2.38 months at 15 mg/day and of 2.64 months at 30 mg/day.CONCLUSIONS:There were no significant differences between primaquine at 15 or 30 mg/day for 14 days in the prevention of P. vivax relapses at 2, 3 and 6 months after primaquine treatment in French Guiana