A revision of Artemia biodiversity in Macaronesia

In a biogeographical context, the term Macaronesia broadly embraces the North Atlantic archipelagos of the Azores, Madeira, Selvagens, the Canary Islands, and Cape Verde. The peculiar arid climatic conditions in some of these places have led to the development of marine salt exploitations, which can be counted among the hypersaline habitats of the brine shrimp Artemia (Branchiopoda, Anostraca). Parthenogenetic populations of this anostracan were described in the Canary Islands during the last decades of the 20th century, while the American Artemia franciscana species was recently found in the Cape Verde archipelago. Following an invasive pattern, this exotic species has recently reached the Canary Islands, too. This paper reports information dealing with biotope loss (solar saltworks) in this biogeographical region, together with possible consequences concerning the arrival of invasive species, two factors that frequently promote dramatic biodiversity losses. The discussion of this threat focuses mainly on the Canary Islands archipelago where native species of Artemia still exist.

New records of mosquitoes from northwestern Argentina

Eleven mosquito species, namely Aedes hastatus, Ae. fulvus, Coquillettidia albicosta, Cq. juxtamansonia, Culex aliciae, Cx. delpontei, Cx. oedipus, Cx. pedroi, Mansonia flaveola, Uranotaenia leucoptera, and Wyeomyia oblita, are recorded for the first time from northwestern Argentina. In addition, 3 species, Cx. brethesi, Limatus durhami, and Ur. nataliae, are reported for the first time from Salta Province. These records extend the geographical distribution of these 3 species to Salta Province. This study also extends the geographical distributions of Cq. nigricans, Cx. chidesteri, and Ma. humeralis to Jujuy Province and of Ae. meprai, Ae. milleri, Ae. oligopistus, Cx. brethesi, Cx. fernandezi, and Cx. tatoi to Tucumán Province.

Does exposure to testosterone significantly alter endogenous metabolism in the marine mussel Mytilus galloprovincialis?

Mussels (Mytilus galloprovincialis) were exposed to different concentrations of testosterone (T: 20, 200 and 2000ng/L) in a semi-static water regime (1-day dosing intervals) for up to 5 days in an attempt to see whether endogenous steroid levels and steroid metabolism were altered by exogenous exposure to testosterone. Whole tissue levels of total testosterone (free+esterified) sharply increased in a concentration-dependent manner, from 2ng/g in controls to 290ng/g in organisms exposed to the highest concentration. In contrast, levels of free testosterone were only significantly elevated at the high-exposure group (5-fold increase with respect to controls). Increased activity of palmitoyl-CoA:testosterone acyltransferase (ATAT) was detected in organisms exposed to the highest concentration of testosterone, while those exposed to low and medium concentrations showed significant alterations in their polyunsaturated fatty acid profiles. The obtained results suggest that esterification of the excess of T with fatty acids might act as a homeostatic mechanism to maintain endogenous levels of free T stable. Interestingly, a decrease in CYP3A-like activity was detected in T-exposed mussels together with a significant decrease in the metabolism of the androgen precursor androstenedione to dihydrotestosterone (5α-DHT). Overall, the work contributes to the better knowledge of androgen metabolism in mussels.

Effect of ivermectin on the liver of gilthead sea bream Sparus aurata: a proteomic approach

Gilthead sea bream Sparus aurata is the most commercialized Mediterranean aquacultured fish species. Ivermectin has recently (experimentally) started to be used to control ectoparasitic infestations in Mediterranean cultured marine fish. The potential hepatotoxicity of ivermectin was investigated in gilthead sea bream juveniles (35g) following oral administration at the recommended dose of 0.2 mgkg(-1) fish for 10d. Difference Gel Electrophoresis Technology (DIGE) was used to study the effect of this treatment in gilthead sea bream liver protein profile under routine culture conditions. The 2D-DIGE protein maps obtained were analyzed using the DeCyder 6.5 software. The results obtained showed significant changes in the expression of 36 proteins respect to the control group. Among these proteins, six increased in abundance, and 30 decreased. Spot showing differential expression respect to the control were analyzed by mass spectrometry and database search, which resulted in three positive identifications corresponding to hepatic proteins involved in lipid metabolism (apoA-I), oxidative stress responses and energy generation (beta-globin, ATP synthase subunit beta). These proteins have not been previously associated to invermectin effect.

Tissue-specific robustness of fatty acid signatures in cultured gilthead sea bream (Sparus aurata L.) fed practical diets with a combined high replacement of fish meal and fish oil

The present study aimed to determine the tissue-specific robustness of fatty acid (FA) signatures of gilthead sea bream (Sparus aurata L.) by analyzing the changes in lipid class and FA composition of skeletal muscle, brain, liver, and mesenteric adipose tissue. Triplicate groups of fish were fed to visual satiety over a 14-mo production cycle with 2 practical plant protein-based diets formulated with either fish oil or a blend of vegetable oils (66% of fish oil replacement) to contain 53% CP and 21% crude fat on a DM basis. Growth rates (P = 0.22) and tissue lipid class composition were not altered by the dietary treatment (P = 0.34 and 0.52 for neutral lipids and phospholipids, respectively). The FA signatures of neutral lipids reflected the composition of the diet, although the output of principal components analysis revealed a divergent FA profile for liver compared with skeletal muscle, brain, and mesenteric adipose tissue. Because the theoretical EFA needs were met by the 2 diets, the FA composition of phospholipids remained almost unaltered in all tissues. Interestingly, however, the brain showed the greatest robustness and regulatory capacity to preserve the phenotype of fish fed fish oil-based diets. The FA signatures of total lipids are a combinatory result of neutral and polar lipids, and the most relevant fat storage tissues (mesenteric adipose tissue and skeletal muscle) were more easily influenced by dietary FA composition. The present study provides new insights into fish tissue FA composition and reinforces the use of FA signatures as useful criteria in determining whether EFA requirements for a wide range of physiological processes, including those of neural tissues, can be met with practical fish feeds.

Triphenyltin alters lipid homeostasis in females of the ramshorn snail Marisa cornuarietis

Molluscs are sensitive species to the toxic effects of organotin compounds, particularly to masculinisation. Both tributyltin (TBT) and triphenyltin (TPT) have been recently shown to bind to mollusc retinoid X receptor (RXR). If RXR is involved in lipid homeostasis, exposure to TPT would have an immediate effect on endogenous lipids. To test this hypothesis, the ramshorn snail Marisa cornuarietis was exposed to environmentally relevant concentrations of TPT (30, 125, 500 ng/L as Sn) in a semi-static water regime for 7 days. Percentage of lipids and total fatty acid content decreased significantly in TPT-exposed females while the activity of peroxisomal acyl-CoA oxidase, involved in fatty acid catabolism, increased. In addition, fatty acid profiles (carbon chain length and unsaturation degree) were significantly altered in exposed females but not in males. This work highlights the ability of TPT to disrupt lipid metabolism in M. cornuarietis at environmentally realistic concentrations and the higher susceptibility of females in comparison to males.

A double-blind, placebo-controlled, randomized, multicenter study to investigate CHInese Medicine Neuroaid Efficacy on Stroke recovery (CHIMES Study)

Rationale Traditional Chinese Medications(TCM) have been reported to have beneficial effects in stroke patients, but were not rigorously evaluated by GCP standards. Aim This study tests the hypothesis that Neuroaid, a TCM widely used in China post-stroke, is superior to placebo in reducing neurological deficit and improving functional outcome in patients with acute cerebral infarction of an intermediate severity. Design This is a multicenter, randomised, double-blind, placebo-controlled study of Neuroaid in ischemic stroke patients with National Institute of Health Stroke Scale(NIHSS) 6-14 treated within 48 h of stroke onset. Neuroaid or placebo is taken (4 capsules) 3 times daily for 3 months. Treatments are assigned using block randomization, stratified for centers, via a central web-randomization system. With a power of 90% and two-sided test of 5% type I error, a sample size is 874. Allowing for a drop-out rate of up to 20%, 1100 individuals should be enrolled in this study. Study Outcomes The primary efficacy endpoint is the modified Rankin Scale(mRS) grades at 3 months. Secondary efficacy endpoints are the NIHSS score at 3 months; difference of NIHSS scores between baseline and 10 days, and between baseline and 3 months; difference of NIHSS sub-scores between baseline and 10 days, and between baseline and 3 months; mRS at 10 days, 1 month, and 3 months; Barthel index at 3 months; Mini Mental State Examination at 10 days and 3 months. Safety outcomes include complete blood count, renal and liver panels, and electrocardiogram.

STUDY REGISTRATION

ClinicalTrials.gov identifier: NCT00554723.

Bipolar disorders and quality of life: the impact of attention deficit/hyperactivity disorder and substance abuse in euthymic patients

Patients with bipolar disorders (BPD) display high rates of comorbidities, especially substance abuse (20-40%) and attention deficit/hyperactivity disorder (ADHD) (6%-20%). However, there are virtually no data evaluating the role of current ADHD on the global functioning of patients with BPD. The recent literature suggests that impairments in quality of life are a key prognostic feature for predicting the long course of BPD. The aim of this study was to investigate the intrinsic impact of adult ADHD and substance abuse in patients with BPD on levels of social adaptation, functioning and vitality. Seventy-three outpatients with BPD I or II, all euthymic and being treated with mood stabilizers, were evaluated using the following measures: 1) the Diagnostic Interview of Genetics Study for DSM-IV criteria; 2) the ADHD Self-Report Scale (ASRS) (screening of adult ADHD); 3) measures of quality of life: social adaptation (Social Adjustment Scale Self-Report (SAS-SR)), well-being (Short Form 36 (SF-36) Health Survey), and the Brief Psychiatric Rating Scale. In this clinical sample, 30% met the ADHD criteria and 22% were substance abusers. The results showed that the presence of ADHD in BPD patients significantly predicted a low social functioning and adaptation by comparison with BPD patients without ADHD. By contrast, we failed to detect a significant impact of substance abuse on those functional outcomes. This is the first step towards improved screening for comorbidities and an understanding of their crucial role in the prognosis of the disorder, as well as in defining new multilevel therapeutic strategies.

Acute toxicity of dichlorvos to Aphanius iberus (Cuvier & Valenciennes, 1846) and its anti-cholinesterase effects on this species

This study evaluates the toxic effects of the organophosphate pesticide (OP) dichlorvos to the endangered Iberian toothcarp (Aphanius iberus). To this end, the lethal toxicity of dichlorvos based on 96h-LC50 bioassays was determined in saline water (50g/L), and in vivo effects of dichlorvos on cholinesterase (ChE) activity were investigated in adult female and male specimens. The 96h-LC50 value determined by probit analysis was 3.17mg/L (95% confidence limits: 1.34-3.97). The characterisation of the ChE using different substrates and specific inhibitors was also carried out in head and muscle tissues. Acetylthiocholine was the substrate preferred by both head and muscle ChE in males and females. Eserine sulphate and BW284C51 significantly inhibited both head and muscle enzyme activity at low concentrations (muM range), and iso-OMPA had no significant effect. These results indicate that in the head and muscle the predominant ChE form is acetylcholinesterase (AChE) for both sexes. The kinetic parameters for ChE activity (Km and Vmax) were similar in both sexes. The 96h-LC50 value obtained for adult specimens of Iberian toothcarp was 3.17mg/L. ChE activity in head and body tissues of both sexes was significantly inhibited in all concentrations tested (0.5, 1, 2 and 4mg/L) after "in vivo" dichlorvos exposure. However, Iberian toothcarp was able to tolerate high concentrations of dichlorvos, and resist high levels of brain and muscle ChE inhibition without mortality. Both ChE inhibition and recovery followed a similar time-course pattern in response to sub-lethal exposure to dichlorvos (1mg/L), and the enzyme activity did not return to control levels after 96h in clean water. The results of this study show that ChE activity is a good biomarker of exposure to OP in the Iberian toothcarp adults.

Exposure to TBT increases accumulation of lipids and alters fatty acid homeostasis in the ramshorn snail Marisa cornuarietis

Recent studies have shown that organotin compounds affect lipid homeostasis in vertebrates, probably through interaction with RXR and/or PPARgamma receptors. Molluscs are sensitive species to the toxic effects of tributyltin (TBT), particularly to masculinization, and TBT has been recently shown to bind to molluscs RXR. Thus, we hypothesized that exposure to TBT could affect lipid homeostasis in the ramshorn snail Marisa cornuarietis. For comparative purposes, the synthetic androgen methyl-testosterone (MT) was included in the study due to its masculinization effects, but its lack of binding to the RXR receptor. M. cornuarietis was exposed to different concentrations of TBT (30, 125, 500 ng/L as Sn) and MT (30, 300 ng/L) for 100 days. Females exposed to 500 ng/L TBT showed increased percentage of lipids and increased levels of fatty acids in the digestive gland/gonad complex (2- to 3-fold). In addition, fatty acid profiles were altered in both males and females exposed to 125 and 500 ng/L TBT. These effects were not observed in females exposed to MT. Overall, this work suggest that TBT acts as a potent inducer of lipid and fatty acid accumulation in M. cornuarietis as shown in vertebrate studies earlier, and that sex differences in sensitivity do exist.

Assessment of the efficacy of Artemia sp (Crustacea) cysts chorion as barrier to chlorpyrifos (organophosphorus pesticide) exposure. Effect on hatching and survival

In order to reveal the efficacy of the Artemia cysts chorion as barrier to the organophosphorus pesticide chlorpyrifos, whole and decapsulated cysts have been exposed to 10 mg L(-1) chlorpyrifos in sea water during hydration and hatching phase, separately. The concentration of chlorpyrifos in capsulated and decapsulated cysts after exposure has been determined in order to elucidate the efficacy of chorion as protection to the embryo. The results obtained demonstrate the ability of the cysts chorion to obstruct the pass of chlorpyrifos molecules through this protection structure. Thus, the concentration of chlorpyrifos in exposed decapsulated cysts is higher than in exposed whole cysts. Moreover, after removing the chorion of exposed cysts, the concentration of chlorpyrifos in the embryo was lower than that of cysts exposed, what would demonstrate the retention of chlorpyrifos molecules by the shell. Hatching was not severely affected by exposure to the insecticide whereas survival at 44 h of the nauplii exposed to chlorpyrifos was significantly different from the controls. Survival of nauplii hatched from exposed decapsulated cysts was higher than that from those hatched from exposed whole cysts, probably because of the lower vitality of the latter, due to depletion of energy reserves during hatching.

Usefulness of procalcitonin levels in community-acquired pneumonia according to the patients outcome research team pneumonia severity index

STUDY OBJECTIVES

To evaluate the usefulness of procalcitonin serum levels as a predictor of etiology and prognosis in adult patients with community-acquired pneumonia (CAP) when they are stratified according to severity.

DESIGN

One-year, population-based, prospective study.

SETTING

University teaching hospital.

PATIENTS

All adult patients who received a diagnosis of CAP throughout the study period.

INTERVENTIONS AND MEASUREMENTS

An extensive noninvasive microbiological workup was performed. In patients who gave informed consent, a blood sample was collected at the time the diagnosis of CAP was established to measure biological markers. Procalcitonin levels were measured by a commercially available monoclonal immunoluminometric assay (limit of detection, 0.1 microg/L). Patients were classified according to microbial diagnosis, Patients Outcome Research Team pneumonia severity index (PSI), and outcome measures, and procalcitonin levels were compared among groups.

RESULTS

Of 240 patients who received a diagnosis of CAP during the study period, procalcitonin concentrations were measured in 185 patients (77.1%). Levels were higher in patients with high-severity risk classes (PSI classes III-V) [p = 0.01] and in those with complications (p = 0.03) or death (p < 0.0001). Among patients classified into PSI low-severity risk classes (classes I-II), levels tended to be higher in those with bacterial etiology (p = 0.08); in this group, a serum procalcitonin level > or = 0.15 microg/L was more frequently found in patients with bacterial pneumonia than in those with nonbacterial pneumonia (p = 0.03). In patients with higher-severity risk classes, no significant differences were observed in procalcitonin levels among etiologic groups, but higher concentrations were associated with development of complications (p = 0.01) and death (p < 0.0001).

CONCLUSIONS

Procalcitonin contribution to the evaluation of CAP varies according to severity. While procalcitonin may have a role to predict the microbial etiology in patients with a low PSI score, in patients classified within high PSI risk classes, it is a prognostic marker rather than a predictor of etiology.

Antioxidant enzyme activities and lipid peroxidation in the freshwater cladoceran Daphnia magna exposed to redox cycling compounds

Contaminant-related changes in antioxidative processes in the freshwater crustacea Daphnia magna exposed to model redox cycling contaminant were assessed. Activities of key antioxidant enzymes including catalase, superoxide dismutase, glutathione peroxidase and glutathione S-transferases and levels of lipid peroxidation measured as thiobarbituric acid-reactive substances (TBARS) and lipofucsin pigment content were determined in D. magna juveniles after being exposed to sublethal levels of menadione, paraquat, endosulfan, cadmium and copper for 48 h. Results denoted different patterns of antioxidant enzyme responses, suggesting that different toxicants may induce different antioxidant/prooxidant responses depending on their ability to produce reactive oxygen species and antioxidant enzymes to detoxify them. Low responses of antioxidant enzyme activities for menadione and endosulfan, associated with increasing levels of lipid peroxidation and enhanced levels of antioxidant enzyme activities for paraquat, seemed to prevent lipid peroxidation, whereas high levels of both antioxidant enzyme activities and lipid peroxidation were found for copper. For cadmium, low antioxidant enzyme responses coupled with negligible increases in lipid peroxidation indicated low potential for cadmium to alter the antioxidant/prooxidant status in Daphnia. Among the studied enzymes, total glutathione peroxidase, catalase and glutathione S-transferase appeared to be the most responsive biomarkers of oxidative stress.

Changes in antioxidant enzyme activities, fatty acid composition and lipid peroxidation in Daphnia magna during the aging process

Age-related changes in the balance between endogenous pro-oxidative and antioxidative processes in the freshwater cladoceran Daphnia magna (Crustacea) were assessed. The activities of key antioxidant enzymes including catalase, superoxide dismutase and glutathione peroxidase and levels of lipid peroxidation measured as thiobarbituric acid-reactive substances (TBARS) were determined in eight age classes, covering juvenile, young and senescent adults. Age-related changes in fatty acid composition were also measured to examine the contribution of polyunsaturated fatty acids (PUFA) in the peroxidation status of animals. Biochemical responses depicted in this study demonstrated that age-related decline in survival was accompanied by increasing oxidative stress and oxidative damage. Enhanced oxidative stress in aging D. magna was suggested by the significant increase in the formation of lipid peroxides, and a concomitant reduction of unsaturated fatty acids of 20 or more carbon atoms. Because aging was accompanied by selective loss of key antioxidant enzymes and small changes in the amount of PUFA, the breakdown of antioxidant defences might have directly contributed to oxidative stress, membrane lipid peroxide and a decline of survival. Indeed, the results reported here, indicate that age-related increases of lipid peroxides were at least partially due to the functional imbalance of enzymatic antioxidant defences.

Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela

The distribution of the sylvatic subtype ID Venezuelan equine encephalitis (VEE) viruses in the lowland tropical forests of western Venezuela was investigated using remote sensing and geographic information system technologies. Landsat 5 Thematic Mapper satellite imagery was used to study the reflectance patterns of VEE endemic foci and to identify other locations with similar reflectance patterns. Enzootic VEE virus variants isolated during this study are the closest genetic relatives of the epizootic viruses that emerged in western Venezuela during 1992-1993. VEE virus surveillance was conducted by exposing sentinel hamsters to mosquito bites and trapping wild vertebrates in seven forests identified and located by means of the satellite image. We isolated VEE viruses from 48 of a total of 1,363 sentinel hamsters in two of the forests on six occasions, in both dry and wet seasons. None of the 12 small vertebrates captured in 8,190 trap-nights showed signs of previous VEE virus infection. The satellite image was classified into 13 validated classes of land use/vegetation using unsupervised and supervised techniques. Data derived from the image consisted of the raw digital values of near- and mid-infrared bands 4, 5, and 7, derived Tasseled Cap indices of wetness, greenness, and brightness, and the Normalized Difference Vegetation Index. Digitized maps provided ancillary data of elevation and soil geomorphology. Image enhancement was applied using Principal Component Analysis. A digital layer of roads together with georeferenced images was used to locate the study sites. A cluster analysis using the above data revealed two main groups of dense forests separated by spectral properties, altitude, and soil geomorphology. Virus was isolated more frequently from the forest type identified on flat flood plains of main rivers rather than the forest type found on the rolling hills of the study area. The spatial analysis suggests that mosquitoes carrying the enzootic viruses would reach 82-97% of the total land area by flying only 1-3 km from forests. We hypothesize that humans within that area are at risk of severe disease caused by enzootic ID VEE viruses. By contrast, equines could actually become naturally vaccinated, thus preventing the local emergence of epizootic IC VEE virus strains and protecting humans indirectly.

Comparison of PCR mediated amplification of DNA and the classical methods for detection of Mycobacterium leprae in different types of clinical samples in leprosy patients and contacts

Traditional staining and microscopic examination techniques for the detection of Mycobacterium leprae, DNA amplification by polymerase chain reaction (PCR) of a 531-bp fragment of the M. leprae specific gene encoding the 36-kDa antigen, and serodiagnosis with M. leprae specific antigens (PGL-1 and D-BSA) were compared on different clinical specimens (serum samples, slit-skin smears, biopsies and swabs) from 60 leprosy patients attending the Sanatorium of Fontilles. Patients were divided into groups; (i) 20 multibacillary patients (MB) with positive bacteriological index (BI) by conventional methods and on WHO multidrug therapy (MDT); (ii) 30 MB patients with negative BI and completed minimum 2 years treatment MDT; (iii) 10 paucibacillary (PB) patients who had completed 6 months MDT at least 8 years ago. Control groups included four non-leprosy patients for PCR methods and 40 health control patients and 10 tuberculosis patients for serological methods. In the multibacillary BI positive group, there was a good correlation between all methods. All tests were negative in the paucibacillary group, although only a few patients were tested and all had been treated many years ago. One must be cautious concerning the diagnostic potential of these techniques in this type of leprosy. We also studied different combinations of leprosy diagnosis methods to determine the potential risk in a leprosy contact individuals group. The prevalence of antibodies to M. leprae antigens in serum was measured, together with the presence of M. leprae DNA in the nose and lepromin status in a group of 43 contacts of leprosy patients (12 household and 31 occupational) to evaluate the maintenance of infection reservoirs and transmission of the disease. Only two individuals were found to form a potential high risk group.

Characterisation of cholinesterases and evaluation of the inhibitory potential of chlorpyrifos and dichlorvos to Artemia salina and Artemia parthenogenetica

In this study, the acute toxicity of the organophosphorous pesticides dichlorvos and chlorpyrifos to two different species of Artemia (A. salina and A. parthenogenetica) was evaluated. In addition, the in vivo effect of these two pesticides on cholinesterase (ChE) activity of both A. salina and A. parthenogenetica was also determined. The characterisation of the ChE, using different substrates and specific inhibitors, and the normal range of activity in non-exposed individuals were previously investigated for both species. The results obtained indicate that the ChE of A. salina is different from that of A. parthenogenetica and that both enzymes cannot be classified neither as acetylcholinesterase nor as butyrylcholinesterase since they show intermediary characteristics between the two vertebrate forms. The range of normal ChE activity was 2.65+/-0.15 U/mg protein for A. salina, and 3.69+/-0.17 U/mg protein for A. parthenogenetica. Significant in vivo effects of both pesticides on Artemia ChE activity were found, at concentrations between 5.38 and 9.30 mg/l for dichlorvos and between 1.85 and 3.19 mg/l for chlorpyrifos. Both Artemia species are resistant to these pesticides and they are able to survive with more than 80% ChE inhibition. However, A. parthenogenetica is more resistant than A. salina, with about a 95% reduction in its ChE activity respect to the control for nauplii exposed to the median lethal concentrations (LC50), without lethal effects after 24 h of exposure.

Bioaccumulation of chlorpyrifos through an experimental food chain: study of protein HSP70 as biomarker of sublethal stress in fish

The accumulation and transfer of the organophosphorus pesticide chlorpyrifos has been studied in an experimental aquatic two-level food chain using two species of the crustacean Artemia (A. franciscana and A. parthenogenetica) and the small fish Aphanius iberus. Artemia adults contaminated by exposure to the pesticide in water were used as live prey for Aphanius, the next trophic level. During the experimental bioaccumulation phase, fish were fed chlorpyrifos-contaminated Artemia pools with concentrations between 6.5 and 14.5 ng/g fresh weight for 32 days. Both concentrations accumulated in fish, and biomagnification factor (BMF) values showed a continuous decrease during the bioaccumulation phase, probably due to the physicochemical characteristics of the organophosphorus pesticide, to the biotransformation ability of fish and to the progressive adaptation of fish metabolism to toxic exposure. The first day that fish were fed uncontaminated preys, the pesticide accumulated via food was rapidly eliminated and was not detected. The effect of chlorpyrifos exposure through the food chain on stress protein (HSP70) synthesis was measured as a general biochemical response of stress in the fish (A. iberus). The levels of HSP70 were significantly higher in fish fed on contaminated Artemia than in the control fish fed on uncontaminated Artemia. Results showed that the HSP70 induction in fish could be associated to exposure of chlorpyrifos via food.

Genetic diversity and relationships among Venezuelan equine encephalitis virus field isolates from Colombia and Venezuela

During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences. The SSCP analysis distinguished isolates differing by as little as 1 nucleotide; overall, differences of > or = 1 nucleotide were recognized 89% of the time, and the sensitivity to distinguish strains that differed by only 1 or 4 nucleotides was 17 and 57%, respectively. Phylogenetic analyses of representative sequences showed that all recent isolates from the Catatumbo region of western Venezuela and the middle Magdalena Valley of Colombia were closely related to epizootic subtype IAB and IC strains; strains from Yaracuy and Miranda States were more distantly related. Cocirculation of the same virus genotype in both Colombian and Venezuelan foci indicated that these viruses are readily transported between enzootic regions separated by > 300 km. The SSCP analysis appears to be a simple, fast, and relatively efficient method of screening VEE virus isolates to identify meaningful genetic variants.

Spatial dispersion of adult mosquitoes (Diptera: Culicidae) in a sylvatic focus of Venezuelan equine encephalitis virus

We studied the spatial localization of mosquitoes in sylvatic focus of Venezuelan equine encephalitis virus in western Venezuela to identify mosquito species potentially involved in the hypothesized transport of viruses out of enzootic foci. The following criteria were used to identify species with potential for virus export: (1) common in the forest and surrounding area, (2) feeding on a wide range of vertebrates; (3) long dispersal capabilities, and (4) established vectorial competence for enzootic or epizootic VEE viruses. CDC traps baited with light/CO2 were operated for four and 12-h intervals to collect mosquitoes at four stations along two forest/open area transects from September to November 1997. We collected 60,444 mosquitoes belonging to 11 genera and 34 species. The most common species were Aedes serratus (Theobald), Ae. scapularis (Rondani), Ae. fulvus (Wiedmann), Culex nigripalus Theobald, Cx, (Culex) "sp", Cx. mollis Dyar & Knab, Cx. spissipes (Theobald), Cx. pedroi Sirivanakarn and Belkin, Psorophora ferox (Humboldt), Ps. albipes (Theobald), and Ps. cingulata (F.). Very few mosquitoes were captured during the (day in the open area outside the forest, suggesting that any virus export from the forest may occur at night. The following mosquitoes seemed to be mostly restricted to the forest habitat: Ae. serratus, Ps. ferox, Ps. albipes, sabethines, Cx. spissipes, Cx. pedroi, Cx. dunni Dyar, and Ae. fulvus. The main species implicated its potential virus export were Cx. nigripalpus, Ae. scapularis, and Mansonia titillans (Walker).

Ecological studies of enzootic Venezuelan equine encephalitis in north-central Venezuela, 1997-1998

From 1997-1998, we investigated the possible continuous circulation of epizootic Venezuelan equine encephalitis (VEE) virus suggested by a 1983 subtype IC interepizootic mosquito isolate made in Panaquire, Miranda State, Venezuela. The study area was originally covered by lowland tropical rainforest but has been converted into cacao plantations. Sentinel hamsters, small mammal trapping, mosquito collections, and human serosurveys were used to detect active or recent virus circulation. Six strains of subtype ID VEE virus were isolated from hamsters that displayed no apparent disease. Four other arboviruses belonging to group A (Togaviridae: Alphavirus), two Bunyamwera group (Bunyaviridae), and three Gamboa group (Bunyaviridae) arboviruses were also isolated from hamsters, as well as 8 unidentified viruses. Venezuelan equine encephalitis-specific antibodies were detected in 5 small mammal species: Proechimys guairae, Marmosa spp., and Didelphis marsupialis. Mosquito collections comprised of 38 different species, including 8 members of the subgenus Culex (Melanoconion), did not yield any virus isolates. Sera from 195 humans, either workers in the cacao plantation or nearby residents, were all negative for VEE virus antibodies. Sequences of 1,677 nucleotides from the P62 gene of 2 virus isolates indicated that they represent a subtype ID lineage that is distinct from all others characterized previously, and are unrelated to epizootic VEE emergence.