8 research outputs found
Entomological Surveillance of Behavioural Resilience and Resistance in Residual Malaria Vector Populations.
The most potent malaria vectors rely heavily upon human blood so they are vulnerable to attack with insecticide-treated nets (ITNs) and indoor residual spraying (IRS) within houses. Mosquito taxa that can avoid feeding or resting indoors, or by obtaining blood from animals, mediate a growing proportion of the dwindling transmission that persists as ITNs and IRS are scaled up. Increasing frequency of behavioural evasion traits within persisting residual vector systems usually reflect the successful suppression of the most potent and vulnerable vector taxa by IRS or ITNs, rather than their failure. Many of the commonly observed changes in mosquito behavioural patterns following intervention scale-up may well be explained by modified taxonomic composition and expression of phenotypically plastic behavioural preferences, rather than altered innate preferences of individuals or populations. Detailed review of the contemporary evidence base does not yet provide any clear-cut example of true behavioural resistance and is, therefore, consistent with the hypothesis presented. Caution should be exercised before over-interpreting most existing reports of increased frequency of behavioural traits which enable mosquitoes to evade fatal contact with insecticides: this may simply be the result of suppressing the most behaviourally vulnerable of the vector taxa that constituted the original transmission system. Mosquito taxa which have always exhibited such evasive traits may be more accurately described as behaviourally resilient, rather than resistant. Ongoing national or regional entomological monitoring surveys of physiological susceptibility to insecticides should be supplemented with biologically and epidemiologically meaningfully estimates of malaria vector population dynamics and the behavioural phenotypes that determine intervention impact, in order to design, select, evaluate and optimize the implementation of vector control measures
Chemical fate and biological effects of several endocrine disrupters compounds in two echinoderm species
Two echinoderm species, the sea urchin Paracentrotus
lividus and the feather star Antedon mediterranea,
were exposed for 28 days to several EDCs: three putative
androgenic compounds, triphenyltin (TPT), fenarimol
(FEN), methyltestosterone (MET), and two putative antiandrogenic
compounds, p,p0-DDE (DDE) and cyproterone
acetate (CPA). The exposure nominal concentrations were
from 10 to 3000 ng L-1, depending on the compound. This
paper is an attempt to join three different aspects coming
from our ecotoxicological tests: (1) the chemical behaviour
inside the experimental system; (2) the measured toxicological
endpoints; (3) the biochemical responses, to which
the measured endpoints may depend. The chemical fate of
the different compounds was enquired by a modelling
approach throughout the application of the âAquarium
modelâ. An estimation of the day-to-day concentration
levels in water and biota were obtained together with the
amount assumed each day by each animal (uptake in
lg animal-1 d-1 or ng g-wet weight-1 d-1). The toxicological
endpoints investigated deal with the reproductive potential
(gonad maturation stage, gonad index and oocyte diameter)
and with the regenerative potential (growth and histology).
Almost all the compounds exerted some kind of effect at the
tested concentrations, however TPT was the most effective
in altering both reproductive and regenerative parameters
(also at the concentration of few ng L-1). The biochemical analyses of testosterone (T) and 17b-estradiol (E2) also
showed the ability of the selected compounds to significantly
alter endogenous steroid concentrations.The present work has received financial support
from the EU âCOMPRENDOâ project no. EVK1-CT-2002-00129.Peer reviewe