Evidence for memorized site-fidelity in Anopheles arabiensis.

A mark-recapture experiment was carried out in northern Tanzania to determine whether Anopheles arabiensis exhibits memory, by investigating if bloodfed individuals would return to either the location or the host where or on which they had obtained a previous bloodmeal, behaviours termed site-fidelity and host-fidelity respectively. Over 4300 mosquitoes were collected from 2 houses, marked with different fluorescent colours according to whether they were caught in cattle sheds, 'cattle-fed', or within human bednets, 'human-fed', at either location, then released from a third location. Over 17,000 mosquitoes were collected and examined over the next 8 days. In total, 1% of released mosquitoes were recaptured. Of these, 68% had returned to the house where they were first caught, demonstrating site-fidelity (P = 0.007). However, 86% of recaptured mosquitoes were caught on cattle regardless of where they were initially caught (P = 0.185). Bloodmeal identification showed that a high proportion of mosquitoes classed as human-fed contained bovine blood, thereby confounding the investigation into host-fidelity. Notably, the proportion of mosquitoes with mixed bloodmeals depended on the proximity of cattle and humans, with significantly higher proportions of mixed bloodmeals occurring when cattle and humans slept in close proximity. The effects of the observed behaviours on malaria epidemiology are discussed.

Analysis of illicit ecstasy tablets: implications for clinical management in the accident and emergency department.

OBJECTIVE: To examine the composition of illicitly manufactured "ecstasy" tablets sold on the UK drugs market. METHODS: Analysis by gas chromatography of 25 illicit ecstasy tablets handed in under amnesty to Leeds Addiction Unit. RESULTS: Illicitly manufactured ecstasy tablets contain a range of ingredients, of widely differing concentrations, and even tablets with the same brand name have variable concentrations of active ingredients. Concentrations of 3,4-methylenedioxymethamphetamine (MDMA) more popularly known as ecstasy, varied 70-fold between tablets. Nine tablets contained neither MDMA nor related analogues. CONCLUSIONS: These results have implications for emergency workers attending to those who have become casualties of the drug ecstasy. Those claiming to have ingested ecstasy may actually have taken other agents that require different clinical management.

Assessment of vector microfilarial uptake as a comparatively non-invasive technique for monitoring onchocerciasis treatment campaigns in the Americas.

Since 1992, efforts have been made to combat onchocerciasis in Guatemala through mass distribution of ivermectin. The impact of the campaign is assessed by taking skin-snips from sentinel groups within selected communities. This method gives an estimate of the prevalence and intensity of infection, and thus the efficacy of the treatment. In some communities people are becoming reluctant to volunteer for skin-snipping, and so there is a need for an alternative technique that will give quantitative results. In most hyperendemic communities in Guatemala, biting blackflies are so ubiquitous that few people object to allowing 10 to 20 flies to engorge upon them. We examined data on the quantitative uptake of microfilariae by Simulium ochraceum before and after ivermectin distribution to see whether results similar to skin-snip data could be obtained. Counts of microfilariae ingested by S. ochraceum are compared to the numbers found in skin-snips from the same volunteers. In a group of 31 untreated infected persons, a skin-snip survey detected 64.5% positive, while feeding flies (vector microfilarial uptake, VmfU) detected 96.8%. Post-treatment, in a sample of 58 of whom 52 (89.7%) had a history of infection, both skin-snips and VmfU detected 54.2%. Vector blood meals contained more microfilariae than a mg of skin before treatment, but both recorded about equal numbers after treatment. When the data set was subdivided to compare samples taken at 2-3, 6-8 and 14-17 months post-treatment, the effect of ivermectin was still apparent at 6-8 months, but had virtually disappeared by 14 months post-treatment. A surprising observation was that the flies ingested fewer microfilariae from treated persons than was expected from the skin densities as estimated by skin-snip. This effect lasted for over 8 months, and could indicate that ivermectin has a greater effect on transmission than previously suspected. We conclude that VmfU could be used as an alternative to skin-snipping, and discuss the ethical implications.