Acta Tropica

Published by Elsevier
Online ISSN: 0001-706X
Publications
Article
We conducted a study to determine the degree of personal protection provided by the Terminix(®) ALLCLEAR(®) Mosquito Mister - Lantern Edition. This outdoor unit was operated to disperse an aerosolized aqueous 0.3% geraniol emulsion in timed-release intervals of 5.0, 7.5, and 10.0 min. Human volunteers participated in landing catch experiments to test the effect of geraniol sprayed at pre-set time intervals, at two distances: (1) 18 ft (5.49 m), the maximum effective distance claimed by the manufacturer, and (2) 9 ft (2.74 m), half the effective distance from the unit. When aerosolized geraniol was dispensed, reductions in biting pressure (landing, probing and biting mosquitoes) of Culex pipiens and Aedes albopictus, at all times and distances, were evident compared to dispensation of the water spray control. The degree of protection correlated well with the distance from the subject and the time interval of releases. The 5 min time interval mode reduced overall biting pressure by more than 90% at 9 ft (2.74 m) and 18 ft (5.49 m). Reduction of biting pressure in the 7.5 min mode was still well over 80% and even in the 10 min mode, overall protection was slightly above 80% at a distance of 9 ft. The lowest but still reasonable protection level was observed in the 10 min mode, at the periphery of the area the unit claims to protect (300 ft(2)), with a biting pressure reduction of approximately two-thirds.
 
Article
Pyriproxyfen, 0.5% granular formulation (GR), an insect growth regulator (IGR) was tested against Culex quinquefasciatus larvae and pupae in disused wells, cesspits and drains at the dosages of 0.1, 0.25, and 0.5kg(ai)/ha to determine the most appropriate field dosage. The IGR was found to be effective against C. quinquefasciatus larvae and pupae in all the larval habitats tested. In drains with slow moving water, application of pyriproxyfen 0.5% GR at 0.5kg(ai)/ha resulted in >80% emergence inhibition (EI) of adults for 4 weeks. At 0.1 and 0.25kg(ai)/ha, the EI was always less than 80%. In stagnant drains, the IGR yielded >80% EI for 1-week period at 0.1kg(ai)/ha. At 0.25 and 0.5kg(ai)/ha, the efficacy was 5-10 times higher. In cesspits, the EI was >80% for 6 weeks when pyriproxyfen 0.5% GR was applied at 0.1kg(ai)/ha, for 11 weeks at 0.25kg(ai)/ha and 9 weeks at 0.5kg(ai)/ha. In disused wells treated at the dosage 0.1kg(ai)/ha, there was >80% EI for 15 weeks and at 0.25 and 0.5kg(ai)/ha, the effective duration was about 1.6-1.8 times longer (24-28 weeks). Considering the quantum of IGR required and the cost and also for safety reasons, the low dosage 0.1kg(ai)/ha is recommended as the field dosage to be applied at weekly interval in stagnant drains, 6 weeks interval in cesspits and 15 weeks interval in disused wells. Since pyriproxyfen 0.5% GR has a relatively longer residual effect than the other IGRs the operational cost could be minimized. Pyriproxyfen 0.5% GR could be one of the choices in the chemical control strategy in Integrated Vector Control Programmes.
 
Article
We previously reported the association of the major histocompatibility complex class II HLA-DQB1*0201 allele with hepatosplenic schistosomiasis. The aim of this study was to evaluate the cytokine responses of peripheral blood mononuclear cells (PBMCs) and the serum levels of immunoglobulin isotypes. The study population was selected from a schistosomiasis endemic area. No significant differences in cytokine profiles were detected in PBMCs stimulated with Schistosoma mansoni soluble egg antigen (SEA), regardless of the subjects DQB1*0201 genotype or infection status. However, previously infected DQB1*0201 positive individuals had significantly lower levels of IgG4 compared to DQB1*0201 negative individuals (P<0.05).
 
Article
Several beta-carboline compounds were evaluated for in vitro trypanocidal activity against Trypanosoma cruzi and their potential toxic effects was also assessed. beta-Carboline derivative 4 showed good activity against epimastigote, trypomastigote, and amastigote forms of T. cruzi, with a dose-dependent inhibitory effect. It showed an IC(50) of 14.9 microM against the epimastigote form and an EC(50) of 45 microM and 33 microM against trypomastigote and amastigote forms, respectively. Additionally, 4 was able to be active on mammalian cell-protozoan interaction, reducing the number of infected cells and the number of internalized parasites. The compound showed low cytotoxicity, with a selective index 31 times higher to the parasite than for mammalian cells. In human red-blood cells beta-Carboline 4 at 14.9 microM not caused haemolysis. Observed at electron microscopy 4-treated epimastigotes showed abnormal swelling of the mitochondrion, a diffuse kinetoplast, and distortions of the parasite cell body. The present data support the potential effect of this class of compounds against T. cruzi and encourage further experiments in vitro to evaluate the action mechanism of this drug and also with in vivo models.
 
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Xiao-Nong Zhou
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