How do tsetse recognise their hosts? The role of shape in the responses of tsetse (Glossina fuscipes and G. palpalis) to artificial hosts

Palpalis-group tsetse, particularly the subspecies of Glossina palpalis and G. fuscipes, are the most important transmitters of human African trypanomiasis (HAT), transmitting .95% of cases. Traps and insecticide-treated targets are used to control tsetse but more cost-effective baits might be developed through a better understanding of the fly’s host-seeking behaviour.Electrocuting grids were used to assess the numbers of G. palpalis palpalis and G. fuscipes quanzensis attracted to and landing on square or oblong targets of black cloth varying in size from 0.01 m2 to 1.0 m2. For both species, increasing the size of a square target from 0.01 m2 (dimensions = 0.1 x 0.1 m) to 1.0 m2 (1.0 x 1.0 m) increased the catch ,4x however the numbers of tsetse killed per unit area of target declined with target size suggesting that the most cost efficient targets are not the largest. For G. f. quanzensis, horizontal oblongs, (1 m wide x 0.5 m high) caught, 1.8x more tsetse than vertical ones (0.5 m wide x 1.0 m high) but the opposite applied for G. p. palpalis. Shape preference was consistent over the range of target sizes. For G. p. palpalis square targets caught as many tsetse as the oblong; while the evidence is less strong the same appears to apply to G. f. quanzensis. The results suggest that targets used to control G. p. palpalis and G. f. quanzensis should be square, and that the most cost-effective designs, as judged by the numbers of tsetse caught per area of target, are likely to be in the region of 0.25 x 0.25 m2. The preference of G. p. palpalis for vertical oblongs is unique amongst tsetse species, and it is suggested that this response might be related to its anthropophagic behaviour and hence importance as a vector of HAT

Revisiting the Immune Trypanolysis Test to Optimise Epidemiological Surveillance and Control of Sleeping Sickness in West Africa

Human African trypanosomiasis (HAT) due to Trypanosoma brucei (T.b.) gambiense is usually diagnosed using two sequential steps: first the card agglutination test for trypanosomiasis (CATT) used for serological screening, followed by parasitological methods to confirm the disease. Currently, CATT will continue to be used as a test for mass screening because of its simplicity and high sensitivity; however, its performance as a tool of surveillance in areas where prevalence is low is poor because of its limited specificity. Hence in the context of HAT elimination, there is a crucial need for a better marker of contact with T.b. gambiense in humans. We evaluated here an existing highly specific serological tool, the trypanolysis test (TL). We evaluated TL in active, latent and historical HAT foci in Guinea, Côte d'Ivoire and Burkina Faso. We found that TL was a marker for exposure to T.b. gambiense. We propose that TL should be used as a surveillance tool to monitor HAT elimination

The exchangeability of shape

<p>Abstract</p> <p>Background</p> <p>Landmark based geometric morphometrics (GM) allows the quantitative comparison of organismal shapes. When applied to systematics, it is able to score shape changes which often are undetectable by traditional morphological studies and even by classical morphometric approaches. It has thus become a fast and low cost candidate to identify cryptic species. Due to inherent mathematical properties, shape variables derived from one set of coordinates cannot be compared with shape variables derived from another set. Raw coordinates which produce these shape variables could be used for data exchange, however they contain measurement error. The latter may represent a significant obstacle when the objective is to distinguish very similar species.</p> <p>Results</p> <p>We show here that a single user derived dataset produces much less classification error than a multiple one. The question then becomes how to circumvent the lack of exchangeability of shape variables while preserving a single user dataset. A solution to this question could lead to the creation of a relatively fast and inexpensive systematic tool adapted for the recognition of cryptic species.</p> <p>Conclusions</p> <p>To preserve both exchangeability of shape and a single user derived dataset, our suggestion is to create a free access bank of reference images from which one can produce raw coordinates and use them for comparison with external specimens. Thus, we propose an alternative geometric descriptive system that separates 2-D data gathering and analyzes.</p

Qualite microbiologique et physicochimique des eaux en sachet "pure water" et le risque sanitaire lie a leur consommation dans la ville de Cotonou au Benin

L’abondance des eaux en sachet communément appelées «Pure water» dans la ville de Cotonou soulève beaucoup de questions quant à leur qualité et aux risques sanitaires liés à leur consommation. Dès lors, nous avons jugé utile d’évaluer le niveau de contamination de ces eaux fortement commercialisées dans la ville de Cotonou.Pour y parvenir, 30 producteurs de « Pure water » ont été enquêtés et un échantillon de 10 producteurs a été retenu pour la collecte et l’évaluation de la qualité physicochimique et microbiologique des eaux. Des analyses microbiologiques (recherche des coliformes totaux, des coliformes fécaux et de la flore totale) et physicochimiques (pH, température, turbidité, conductivité, TDS, nitrates, nitrites et chlore résiduel ont été effectuées sur les eaux collectées.Les enquêtes ont révélés que l’eau de la Société Nationale des Eaux du Bénin (SONEB) reste la seule source d’eau utilisée pour la production des « Pure water» à Cotonou. 90% des producteurs sont agréés par la Direction de l’Alimentation et de la Nutrition Appliquée (DANA) du Bénin. Les eaux échantillonnées étaient contaminées par les coliformes totaux 80%, coliformes fécaux 50% et les germes aérobies 100%. Deux échantillons d’eaux en bouteille collectés et utilisés pour comparaison des données étaient faiblement pollués par les coliformes totaux et les germes aérobies. Par contre, tous les paramètres physicochimiques des eaux analysées respectaient les valeurs fixées par les normes béninoises.En somme, les «pure water » distribuées à Cotonou représentent un important risque sanitaire à cause de leur contamination microbienne en coliformes et en germes aérobies.Mots clés: pure water, physicochimique, coliformes, germes aérobies, BéninEnglish Title: Microbiological and physicochemical quality of sachet water "pure water" and the health risk related to their consumption in the city of Cotonou in BeninEnglish AbstractThe huge distribution of ‘pure water’ in the city of Cotonou in Benin raises polemics on the quality as well as the health risks associated to the consumption of these waters. Therefore we found judicious to evaluate the quality of sacked waters in Cotonou through microbial (screening of fecal and total coliforms, and aerobic germs) and physicochemical (pH, temperature, turbidity, conductivity, TDS, nitrites, nitrates, and chlorine) analyses. Overall, 30 producers of sacked waters were surveyed and 10 producers were systematically selected for water collection and analysis. Data showed that water from the national water company (SONEB) constitutes the only source of water used to produce pure water in the town of Cotonou. Up to 90% of producers are recognized by the Applied Food and Nutrition Direction of Benin (DANA). Microbial analysis of sampled water revealed the presence of fecal coliforms (5/10), total coliforms (8/10) and aerobic germs (10/10). Bottled waters (2) revealed a low level of total coliforms and aerobic germs and were less contaminated than sacked waters. The physico-chemical properties of all sampled waters were under the Beninese threshold standards.In summary, the consumption of sacked waters distributed in the city of Cotonou might pose a health hazard due to contamination by microbial pathogens.Keywords: pure water, physicochemical, coliforms, aerobic germs, Beni