Evidence for Circulation of the Rift Valley Fever Virus among Livestock in the Union of Comoros

Rift Valley fever virus (RVFV) is an arthropod-borne phlebovirus reported to be circulating in most parts of Africa. Since 2009, RVFV has been suspected of continuously circulating in the Union of Comoros. To estimate the incidence of RVFV antibody acquisition in the Comorian ruminant population, 191 young goats and cattle were selected in six distinct zones and sampled periodically from April 2010 to August 2011. We found an estimated incidence of RVFV antibody acquisition of 17.5% (95% confidence interval (CI): [8.9–26.1]) with a significant difference between islands (8.2% in Grande Comore, 72.3% in Moheli and 5.8% in Anjouan). Simultaneously, a longitudinal entomological survey was conducted and ruminant trade-related information was collected. No RVFV RNA was detected out of the 1,568 blood-sucking caught insects, including three potential vectors of RVFV mosquito species. Our trade survey suggests that there is a continuous flow of live animals from eastern Africa to the Union of Comoros and movements of ruminants between the three Comoro islands. Finally, a cross-sectional study was performed in August 2011 at the end of the follow-up. We found an estimated RVFV antibody prevalence of 19.3% (95% CI: [15.6%–23.0%]). Our findings suggest a complex RVFV epidemiological cycle in the Union of Comoros with probable inter-islands differences in RVFV circulation patterns. Moheli, and potentially Anjouan, appear to be acting as endemic reservoir of infection whereas RVFV persistence in Grande Comore could be correlated with trade in live animals with the eastern coast of Africa. More data are needed to estimate the real impact of the disease on human health and on the national economy.     

Sucrose protectable inhibition of the sucrose transporter by N-ethylmaleimide

To understand contradictory data published in the literature,the sensitivity of sucrose and of valine uptake to N-ethylmaleimide(NEM) was reinvestigated in detail with plasma membrane vesiclespurified by phase partitioning from mature sugar beet (Betavulgaris) leaves. Uptake in the vesicles was energized by anartificial proton-motive force combining a pH gradient and anelectrical gradient. Three main parameters were varied in theexperiments: the presence of a reducing agent, dlthiothreitol(DTT) In the medium used to store the vesicles, the temperatureof pretreatment with NEM (12 or 23°C) and the temperatureof incubation with the labelled substrate (12 or 23°C).Sensitivity of sucrose uptake to NEM only appeared with vesiclesthat had been stored in the presence of DTT, and if the pretreatmentwas run at 23°C. The temperature of incubation with labelledsucrose did not affect NEM sensitivity. The NEM sensitivityof valine uptake was not affected in the same way as sucroseuptake by the temperature of preincubation, showing that theeffects observed were specific for a given transporter. Underconditions which normally inhibit sucrose uptake, addition ofsucrose during NEM pretreatment protected the sucrose transporteragainst NEM inhibition. Key words: Sugar transport, plasma membrane, differential labelling, thiol reagents