Towards an early warning system for Rhodesian sleeping sickness in savannah areas: man-like traps for tsetse flies

Background: In the savannahs of East and Southern Africa, tsetse flies (Glossina spp.) transmit Trypanosoma brucei rhodesiense which causes Rhodesian sleeping sickness, the zoonotic form of human African trypanosomiasis. The flies feed mainly on wild and domestic animals and are usually repelled by humans. However, this innate aversion to humans can be undermined by environmental stresses on tsetse populations, so increasing disease risk. To monitor changes in risk, we need traps designed specifically to quantify the responsiveness of savannah tsetse to humans, but the traps currently available are designed to simulate other hosts. Methodology/Principal Findings: In Zimbabwe, two approaches were made towards developing a man-like trap for savannah tsetse: either modifying an ox-like trap or creating new designs. Tsetse catches from a standard ox-like trap used with and without artificial ox odor were reduced by two men standing nearby, by an average of 34% for Glossina morsitans morsitans and 56% for G. pallidipes, thus giving catches more like those made by hand-nets from men. Sampling by electrocuting devices suggested that the men stopped flies arriving near the trap and discouraged trap-entering responses. Most of human repellence was olfactory, as evidenced by the reduction in catches when the trap was used with the odor of hidden men. Geranyl acetone, known to occur in human odor, and dispensed at 0.2 mg/h, was about as repellent as human odor but not as powerfully repellent as wood smoke. New traps looking and smelling like men gave catches like those from men. Conclusion/Significance: Catches from the completely new man-like traps seem too small to give reliable indices of human repellence. Better indications would be provided by comparing the catches of an ox-like trap either with or without artificial human odor. The chemistry and practical applications of the repellence of human odor and smoke deserve further study

Eocambrian—Cambrian palaeomagnetism of the Armorican Massif, France

In an attempt to clarify pre-Hercynian continental configurations, palaeomagnetic data were collected from the spilites de Paimpol (640 ± 12 Myr), the diorite de St Quay (583 ± 40 Myr), the gabbro de Keralain (undated), the granite de Port-Scarff (557 ± 16 Myr), the rhyolitic ignimbrites of LÉzardrieux (546 ± 8 Myr) and the rhyolites de St Germain-le-Gaillard (Undated) from the unmetamorphosed to slightly metamorphosed Eocambrian–Cambrian terranes of the Domnonean Domain of northern Brittany and north-western Normandy. Upon stepwise thermal and/or alternating field demagnetization and using vector subtraction, the spilites de Paimpol yield a characteristic direction with declination ( D ) = 226.4°, inclination ( I ) =– 15.7°. Local remagnetization by microgranite dykes (approximately 560 Myr old) produced a dircction of D = 235.1°, I =+ 63.4°. The diorite de St Quay exhibits multivectorial behaviour revealing a characteristic component of D = 31.2°, I =– 2.3°, and a secondary component of D = 299.9°, I =+ 38.2°. The gabbro de Keralain shows a characteristic component ( D = 290.9°, I = 41.4°) similar to the diorite's secondary component, and gives a secondary component of D = 221.0°, I =+ 55.8°. This secondary component of the gabbro appears again as the characteristic (although somewhat scattered) directions of the granite de Porz-Scarff. Thus, the gabbro may be relatively dated as having been magnetized before the intrusion and cooling of the granite (557 ± 16 Myr) and after that of the diorite (583 ± 40 Myr). The data from the rhyolites are the least certain because of ambiguities in the radiometric dating and uncertain bedding corrections, but they contain directions near to those of the granite and the microgranite dykes, all believed to be of the same episode of acidic volcanism. The trend in palaeomagnetic poles from the Armorican Massif for the Eocambrian–Cambrian corresponds well with coeval data from the southern United Kingdom and Czechoslovakia (Bohemian Massif), suggesting that a single continental mass, Armorica, contained all three areas. A comparison with poles from Gondwanaland also shows a remarkable agreement and suggests a period of coherent movement during the Latest Precambrian and the Cambrian for Armorica and Gondwana, followed by later separation. This leaves the Armorica plate as a separate continental unit at the outset of the Caledonian orogeny later in the Palaeozoic.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75303/1/j.1365-246X.1980.tb04830.x.pd