Reach and catchment-scale characteristics are relatively uninfluential in explaining the occurrence of stream fish species.

The objectives of this study were (1) to determine whether the presence or absence of prairie fishes can be modelled using habitat and biotic characteristics measured at the reach and catchment scales and (2) to identify which scale (i.e. reach, catchment or a combination of variables measured at both scales) best explains the presence or absence of fishes. Reach and catchment information from 120 sites sampled from 1999 to 2004 were incorporated into tree classifiers for 20 prairie fish species, and multiple criteria were used to evaluate models. Fewer than six models were considered significant when modelling individual fish occurrences at the reach, catchment or combined scale, and only one species was successfully modelled at all three scales. The scarcity of significant models is probably related to the rigorous criteria by which these models were evaluated as well as the prevalence of tolerant, generalist fishes in these stochastic and intermittent streams. No significant differences in the amount of reduced deviance, mean misclassification error rates (MER), and mean improvement in MER metrics was detected among the three scales. Results from this study underscore the importance of continued habitat assessment at smaller scales to further understand prairie-fish occurrences as well as further evaluations of modelling methods to examine habitat relationships for tolerant, ubiquitous species. Incorporation of such suggestions in the future may help provide more accurate models that will allow for better management and conservation of prairie-fish species.

Longitudinal Changes in Cerebral Perfusion, Perivascular Space Volume, and Ventricular Volume in a Healthy Cohort Undergoing a Spaceflight Analog.

BACKGROUND AND PURPOSE: A global decrease in brain perfusion has recently been reported during exposure to a ground-based spaceflight analog. Considering that CSF and glymphatic flow are hypothesized to be propelled by arterial pulsations, it is unknown whether a change in perfusion would impact these CSF compartments. The aim of the current study was to evaluate the relationship among changes in cerebral perfusion, ventricular volume, and perivascular space volume before, during, and after a spaceflight analog. MATERIALS AND METHODS: Eleven healthy participants underwent 30 days of bed rest at 6° head-down tilt with 0.5% atmospheric CO2 as a spaceflight analog. For each participant, 6 MR imaging brain scans, including perfusion and anatomic-weighted T1 sequences, were obtained before, during, and after the analog period. Global perfusion, ventricular volume, and perivascular space volume time courses were constructed and evaluated with repeated measures ANOVAs. RESULTS: Global perfusion followed a divergent time trajectory from ventricular and perivascular space volume, with perfusion decreasing during the analog, whereas ventricular and perivascular space volume increased (P < .001). These patterns subsequently reversed during the 2-week recovery period. CONCLUSIONS: The patterns of change in brain physiology observed in healthy participants suggest a relationship between cerebral perfusion and CSF homeostasis. Further study is warranted to determine whether a causal relationship exists and whether similar neurophysiologic responses occur during spaceflight.

Prolonged Microgravity Affects Human Brain Structure and Function.

BACKGROUND AND PURPOSE: Widespread brain structural changes are seen following extended spaceflight missions. The purpose of this study was to investigate whether these structural changes are associated with alterations in motor or cognitive function. MATERIALS AND METHODS: Brain MR imaging scans of National Aeronautics and Space Administration astronauts were retrospectively analyzed to quantify pre- to postflight changes in brain structure. Local structural changes were assessed using the Jacobian determinant. Structural changes were compared with clinical findings and cognitive and motor function. RESULTS: Long-duration spaceflights aboard the International Space Station, but not short-duration Space Shuttle flights, resulted in a significant increase in total ventricular volume (10.7% versus 0%, P < .001, n = 12 versus n = 7). Total ventricular volume change was significantly associated with mission duration (r = 0.72, P = .001, n = 19) but negatively associated with age (r = -0.48, P = .048, n = 19). Long-duration spaceflights resulted in significant crowding of brain parenchyma at the vertex. Pre- to postflight structural changes of the left caudate correlated significantly with poor postural control; and the right primary motor area/midcingulate correlated significantly with a complex motor task completion time. Change in volume of 3 white matter regions significantly correlated with altered reaction times on a cognitive performance task (bilateral optic radiations, splenium of the corpus callosum). In a post hoc finding, astronauts who developed spaceflight-associated neuro-ocular syndrome demonstrated smaller changes in total ventricular volume than those who did not (12.8% versus 6.5%, n = 8 versus n = 4). CONCLUSIONS: While cautious interpretation is appropriate given the small sample size and number of comparisons, these findings suggest that brain structural changes are associated with changes in cognitive and motor test scores and with the development of spaceflight-associated neuro-optic syndrome.

Development of High Signal Intensity within the Globus Pallidus and Dentate Nucleus following Multiple Administrations of Gadobenate Dimeglumine.

BACKGROUND AND PURPOSE: Previous studies have evaluated various gadolinium based contrast agents and their association with gadolinium retention, however, there is a discrepancy in the literature concerning the linear agent gadobenate dimeglumine. Our aim was to determine whether an association exists between the administration of gadobenate dimeglumine and the development of intrinsic T1-weighted signal in the dentate nucleus and globus pallidus. MATERIALS AND METHODS: In this single-center, retrospective study, the signal intensity of the globus pallidus, dentate nucleus, thalamus, and middle cerebellar peduncle was measured on unenhanced T1-weighted images in 29 adult patients who had undergone multiple contrast MRIs using exclusively gadobenate dimeglumine (mean, 10.1 ± 3.23 doses; range, 6-18 doses). Two neuroradiologists, blinded to the number of prior gadolinium-based contrast agent administrations, separately placed ROIs within the globi pallidi, thalami, dentate nuclei, and middle cerebellar peduncles on the last MR imaging examinations. The correlations between the globus pallidus:thalamus and the dentate nucleus:middle cerebellar peduncle signal intensity ratios with the number of gadolinium-based contrast agent administrations and cumulative dose were tested with either 1-tailed Pearson or Spearman correlations. A priori, P < .05 was considered statistically significant. RESULTS: Both the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the number of gadolinium-based contrast agent administrations (r = 0.39, P = .017, and r = 0.58, P = .001, respectively). Additionally, the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the cumulative dose of gadobenate dimeglumine (r = 0.48, P = .004, and r = 0.43, P = .009, respectively). Dentate nucleus hyperintensity was qualitatively present on the last MR imaging in 79.3%-86.2% of patients and in all patients who had received >10 doses. CONCLUSIONS: At high cumulative doses (commonly experienced by patients, for example, with neoplastic disease), gadobenate dimeglumine is associated with an increase in the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncles signal intensity ratios.

Comparison of Gadoterate Meglumine and Gadobutrol in the MRI Diagnosis of Primary Brain Tumors: A Double-Blind Randomized Controlled Intraindividual Crossover Study (the REMIND Study).

BACKGROUND AND PURPOSE: Effective management of patients with brain tumors depends on accurate detection and characterization of lesions. This study aimed to demonstrate the noninferiority of gadoterate meglumine versus gadobutrol for overall visualization and characterization of primary brain tumors. MATERIALS AND METHODS: This multicenter, double-blind, randomized, controlled intraindividual, crossover, noninferiority study included 279 patients. Both contrast agents (dose = 0.1 mmol/kg of body weight) were assessed with 2 identical MRIs at a time interval of 2-14 days. The primary end point was overall lesion visualization and characterization, scored independently by 3 off-site readers on a 4-point scale, ranging from "poor" to "excellent." Secondary end points were qualitative assessments (lesion border delineation, internal morphology, degree of contrast enhancement, diagnostic confidence), quantitative measurements (signal intensity), and safety (adverse events). All qualitative assessments were also performed on-site. RESULTS: For all 3 readers, images of most patients (>90%) were scored good or excellent for overall lesion visualization and characterization with either contrast agent; and the noninferiority of gadoterate meglumine versus gadobutrol was statistically demonstrated. No significant differences were observed between the 2 contrast agents regarding qualitative end points despite quantitative mean lesion percentage enhancement being higher with gadobutrol (P < .001). Diagnostic confidence was high/excellent for all readers in >81% of the patients with both contrast agents. Similar percentages of patients with adverse events related to the contrast agents were observed with gadoterate meglumine (7.8%) and gadobutrol (7.3%), mainly injection site pain. CONCLUSIONS: The noninferiority of gadoterate meglumine versus gadobutrol for overall visualization and characterization of primary brain tumors was demonstrated.

Monitoring of aromatic amine exposures in workers at a chemical plant with a known bladder cancer excess.

BACKGROUND: In April 1991, an excess of bladder cancer cases among workers employed at a chemical manufacturing facility in Niagara Falls, NY, was reported. This excess was primarily confined to 708 workers who had ever been employed in the rubber chemicals manufacturing area of the plant, where the aromatic amines aniline and o-toluidine have historically been used. PURPOSE: An environmental and biological monitoring survey was conducted to evaluate current exposures to aniline and o-toluidine in the rubber chemicals department. METHODS: Personal air sampling for aniline and o-toluidine was conducted with the use of a modified Occupational Safety and Health Administration (OSHA) 73 method. Urine samples were collected before and after work (i.e., pre-shift and post-shift, respectively) and stored at -70 degrees C. Base hydrolysis was used to convert acetanilide and N-acetyl-o-toluidine, metabolites of aniline and o-toluidine present in the urine, to the parent compounds. The parent compounds were extracted from the alkaline urine into butyl chloride and then back-extracted from the butyl chloride into aqueous hydrochloric acid. An aliquot of each acidic extract was subjected to ion-interaction reversed-phase liquid chromatography with coulometric electrochemical detection. Hemoglobin (Hb) was extracted from blood and stored at -70 degrees C. For the measurement of adducts of aniline, o-toluidine, and 4-aminobiphenyl (4-ABP), precipitated Hb was dissolved in 0.1 M sodium hydroxide in the presence of recovery standards, and the hydrolysate was extracted with hexane, derivatized with pentafluoropropionic anhydride, and analyzed by gas chromatography-mass spectrometry with negative chemical ionization. RESULTS: A total of 73 workers, including 46 of 64 exposed workers who were employed in the rubber chemicals department and had the potential for exposure to aniline and o-toluidine and 27 of 52 unexposed workers employed in other departments where aniline and o-toluidine were not used or produced, had data available for both aniline and o-toluidine and Hb adducts; 28 of the workers in the former group also had personal air-sampling data. Personal air sample measurements showed that airborne concentrations of aniline and o-toluidine were well within the limits allowed in the workplace by OSHA. Urinary aniline and o-toluidine levels, however, were substantially higher among exposed workers than among unexposed control subjects. The most striking differential was for post-shift urinary o-toluidine levels, which averaged (+/- standard deviation) 2.8 micrograms/L (+/- 1.4 micrograms/L) in unexposed subjects and 98.7 micrograms/L (+/- 119.4 micrograms/L) in exposed subjects (P = .0001). Average aniline-Hb and o-toluidine-Hb adduct levels were also significantly higher (P = .0001) among exposed workers than among unexposed control subjects. Average levels of adducts to 4-ABP, a potential contaminant of process chemicals, were not significantly different (P = .48), although three exposed workers had 4-ABP levels above the range in unexposed workers. CONCLUSIONS: The adduct data suggest that, among current workers, o-toluidine exposure substantially exceeds aniline exposure and that 4-ABP exposure, if it occurs at all, is not widespread. These data support the conclusion that occupational exposure to o-toluidine is the most likely causal agent of the bladder cancer excess observed among workers in the rubber chemicals department of the plant under study, although exposures to aniline and 4-ABP cannot be ruled out.

Pediatric Patients Demonstrate Progressive T1-Weighted Hyperintensity in the Dentate Nucleus following Multiple Doses of Gadolinium-Based Contrast Agent.

BACKGROUND AND PURPOSE: While there have been recent reports of brain retention of gadolinium following gadolinium-based contrast agent administration in adults, a retrospective series of pediatric patients has not previously been reported, to our knowledge. We investigated the relationship between the number of prior gadolinium-based contrast agent doses and increasing T1 signal in the dentate nucleus on unenhanced T1-weighted MR imaging. We hypothesized that despite differences in pediatric physiology and the smaller gadolinium-based contrast agent doses that pediatric patients are typically administered based on weighted-adjusted dosing, the pediatric brain would also demonstrate dose-dependent increasing T1 signal in the dentate nucleus. MATERIALS AND METHODS: We included children with multiple gadolinium-based contrast agent administrations at our institution. A blinded reader placed ROIs within the dentate nucleus and adjacent cerebellar white matter. To eliminate reader bias, we also performed automated ROI delineation of the dentate nucleus, cerebellar white matter, and pons. Dentate-to-cerebellar white matter and dentate-to pons ratios were compared with the number of gadolinium-based contrast agent administrations. RESULTS: During 20 years at our institution, 280 patients received at least 5 gadolinium-based contrast agent doses, with 1 patient receiving 38 doses. Sixteen patients met the inclusion/exclusion criteria for ROI analysis. Blinded reader dentate-to-cerebellar white matter ratios were significantly associated with gadolinium-based contrast agent doses (rs = 0.77, P = .001). The dentate-to-pons ratio and dentate-to-cerebellar white matter ratios based on automated ROI placement were also significantly correlated with gadolinium-based contrast agent doses (t = 4.98, P < .0001 and t = 2.73, P < .02, respectively). CONCLUSIONS: In pediatric patients, the number of prior gadolinium-based contrast agent doses is significantly correlated with progressive T1-weighted dentate hyperintensity. Definitive confirmation of gadolinium deposition requires tissue analysis. Any potential clinical sequelae of gadolinium retention in the developing brain are unknown. Given this uncertainty, we suggest taking a cautious stance, including the use, in pediatric patients, of higher stability, macrocyclic agents, which in both human and animal studies have been shown to be associated with lower levels of gadolinium deposition, and detailed documentation of dosing. Most important, a patient should not be deprived of a well-indicated contrasted MR examination.

Characterisation of oligosaccharides from Drosophila melanogaster glycoproteins.

An analysis of the released oligosaccharides from a membrane glycoprotein preparation of third instar larvae (3rdIL), and purified larval serum protein 2 (LSP2) from Drosophila melanogaster was performed. Sequential exoglycosidase digestion in combination with high-resolution gel permeation chromatography and partial acetolysis indicated the presence of two series of oligomannosides; one of these series was unusual and characterized by the presence of a core alpha 1-6 linked fucose, the other was a typical mammalian oligomannose series containing the following isomers -D1, -D2, -D12, -D123 and -CD123 as well as the unprocessed Man9GlcNAc2 structure. Conventional oligomannose could only be detected in the LSP2 sample. This study opens the way to use powerful molecular and classical genetic techniques to analyse the control and functional significance of glycosylation in higher organisms.

Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight.

BACKGROUND AND PURPOSE: Following long-term spaceflight, a subset of the National Aeronautics and Space Administration astronauts present with visual impairment and increased intracranial pressure, known as visual impairment and intracranial pressure syndrome. We investigated structural brain changes following long-term head-down tilt bed rest as a spaceflight analog. MATERIALS AND METHODS: Volumetric analysis was performed on structural pre- and post-bed rest brain MR images. RESULTS: Comparing post-bed rest to pre-bed rest images, we found the following: 1) no significant group differences in GM, WM, CSF, or ventricular volumes; 2) shift of the center of mass of the brain upward and posterior rotation of the brain relative to the skull; 3) a significant correlation between posterior brain rotation and changes in ventricular volume; and 4) significant increases in brain tissue density in regions at the vertex, including the frontoparietal lobes, with contraction of adjacent extra-axial CSF spaces, and significant decreases in tissue density in areas along the base of the brain, including the orbitofrontal cortex. CONCLUSIONS: We observed widespread morphologic changes with brain tissue redistribution in response to gravity changes; possible associated functional changes are unknown. The observation that ventricular change is correlated to posterior brain rotation suggests an alteration in CSF homeostasis. Ultimately, to elucidate any structural changes that may play a role in visual impairment and intracranial pressure syndrome, volumetric analysis of pre- and postflight structural scans of astronauts is needed.

A combined TMS/fMRI study of intensity-dependent TMS over motor cortex.

BACKGROUND: Transcranial magnetic stimulation (TMS) allows noninvasive stimulation of neurons using time-varying magnetic fields. Researchers have begun combining TMS with functional imaging to simultaneously stimulate and image brain activity. Recently, the feasibility of interleaving TMS with functional magnetic resonance imaging (fMRI) was demonstrated. This study tests this new method to determine if TMS at different intensities shows different local and remote activation. METHODS: Within a 1.5 Tesla (T) MRI scanner, seven adults were stimulated with a figure-eight TMS coil over the left motor cortex for thumb, while continuously acquiring blood oxygen level dependent (BOLD) echoplanar images. TMS was applied at 1 Hz in 18-second long trains delivered alternately at 110% and 80% of motor threshold separated by rest periods. RESULTS: Though the TMS coil caused some artifacts and reduced the signal to noise ratio (SNR), higher intensity TMS caused greater activation than lower, both locally and remotely. The magnitude (approximately 3% increase) and temporal onset (2 to 5 sec) of TMS induced blood flow changes appear similar to those induced using other motor and cognitive tasks. CONCLUSIONS: Though work remains in refining this potentially powerful method, combined TMS/fMRI is both technically feasible and produces measurable dose-dependent changes in brain activity.

Unilateral left prefrontal transcranial magnetic stimulation (TMS) produces intensity-dependent bilateral effects as measured by interleaved BOLD fMRI.

Transcranial magnetic stimulation (TMS) administered over the prefrontal cortex has been shown to subtly influence neuropsychological tasks, and has antidepressant effects when applied daily for several weeks. Prefrontal TMS does not, however, produce an immediate easily observable effect, making it hard to determine if one has stimulated the cortex. Most prefrontal TMS studies have stimulated using intensity relative to the more easily determined motor threshold (MT) over motor cortex. Five healthy adults were studied in a 1.5 T MRI scanner during short trains of 1 Hz TMS delivered with a figure eight MR compatible TMS coil followed by rest epochs. In a randomized manner, left prefrontal TMS was delivered at 80%, 100% and 120% of MT interleaved with BOLD fMRI acquisition. Compared to rest, all TMS epochs activated auditory cortex, with 80% MT having no other areas of significant activation. 100% MT showed contralateral activation and 120% MT showed bilateral prefrontal activation. Higher intensity TMS, compared to lower, in general produced more activity both under the coil and contralaterally. Higher prefrontal TMS stimulation intensity produces greater local and contralateral activation. Importantly, unilateral prefrontal TMS produces bilateral effects, and TMS at 80% MT produces only minimal prefrontal cortex activation.

Occupational exposure of workers to 1,3-butadiene.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted an extent-of-exposure study of the 1,3-butadiene monomer, polymer, and end-user industries to determine the size of the exposed workforce, evaluate control technologies and personal protective equipment programs, and assess occupational exposure to 1,3-butadiene. A new analytical method was developed for 1,3-butadiene that increased the sensitivity and selectivity of the previous NIOSH method. The new method is sensitive to 0.2 microgram per 1,3-butadiene sample. Walk-through surveys were conducted in 11 monomer, 17 polymer, and 2 end-user plants. In-depth industrial hygiene surveys were conducted at 4 monomer, 5 polymer, and 2 end-user plants. Airborne exposure concentrations of 1,3-butadiene were determined using personal sampling for each job category. A total of 692 full shift and short-term personnel and 259 area air samples were examined for the presence of 1,3-butadiene. Sample results indicated that all worker exposures were well below the current OSHA PEL of 1000 ppm. Exposures ranged from less than 0.006 ppm to 374 ppm. The average exposure for all samples was less than 2 ppm. The present American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value for 1,3-butadiene is 10 ppm. To reduce the potential for occupational exposure, it is recommended that quality control sampling be conducted using a closed loop system. Also all process pumps should be retrofitted with dual mechanical seals, magnetic gauges should be used in loading and unloading rail cars, and engineering controls should be designed for safely voiding quality control cylinders.

Motor cortex brain activity induced by 1-Hz transcranial magnetic stimulation is similar in location and level to that for volitional movement.

RATIONALE AND OBJECTIVES: The relatively high temporal and spatial resolution of functional MR imaging was used to compare the blood oxygenation level dependent (BOLD) response associated with movement induced by transcranial magnetic stimulation (TMS) with that for a similar movement executed volitionally (VOL). METHODS: Seven healthy adults were studied in a 1.5-T MR scanner. One hertz TMS at 110% of motor threshold was applied over the motor cortex for the thumb in 21-pulse trains in alternation with VOL every 63 seconds and interleaved with functional MR imaging. RESULTS: BOLD increases in motor cortex associated with TMS and VOL movement were similar (2%-3%). Mean separation of their centers of activity was 3.7 + 1.9 mm (mean displacement: left/right = 0.3 +/- 4.1 mm; superior/inferior = 0.7 +/- 1.9 mm). There was no indication of supraphysiological brain activity. CONCLUSIONS: Motor cortex BOLD response associated with thumb movement induced by 1-Hz TMS at 110% motor threshold is similar in both location and level to that caused by a similar movement executed volitionally.

The environment, remote sensing, and malaria control.

Results of studies in California, Mexico and Belize demonstrate the value of remote sensing technology for studying vector-borne diseases. These studies have also shown that it is necessary to fully define the environmental factors associated with the presence of vectors and disease transmission, and to be able to detect these environmental factors with image data. These studies, and other published reports, are demonstrating many potential uses of remotely sensed data in managing and targeting vector and disease control measures.

Insecticide resistance issues in vector-borne disease control.

Vector-borne diseases are an increasing cause of death and suffering worldwide. Efforts to control these diseases have been focused on the use of chemical pesticides, but arthropod resistance (whether physiological, biochemical, or behavioral) to pesticides is now an immense practical problem. The pharmacokinetic interactions of pesticides with arthropods, mechanisms of resistance, and the strengths and shortcomings of different resistance test methods are briefly reviewed. Using malaria control as an example, the differences between the efficacy of insecticide-sprayed houses in reducing malaria transmission, and the actual effect of such treatments on vectors are discussed. Reduced malaria transmission as a result of spraying house walls occurs through some combination of killing vectors that land on sprayed walls (insecticidal effect) and by preventing vectors from entering or remaining inside long enough to bite (behavioral effects). Both insecticidal and behavioral effects of insecticides are important, but the relative importance of one versus the other is controversial. Field studies in Africa, India, Brazil, and Mexico provide persuasive evidence for strong behavioral avoidance of DDT by the primary vector species. This avoidance behavior, exhibited when malaria vectors avoid insecticides by not entering or by rapidly exiting sprayed houses, should raise serious questions about the overall value of current physiological and biochemical resistance tests. The continued efficacy of DDT in Africa, India, Brazil, and Mexico, where 69% of all reported cases of malaria occur and where vectors are physiologically resistant to DDT (excluding Brazil), serves as one indicator that repellency is very important in preventing indoor transmission of malaria. This experience with DDT has implications for future control efforts because pyrethroids also stimulate avoidance behaviors in arthropods. Each chemical should be studied early (before broad-scale use) to define types of action against vector species by geographic area, especially for impregnated bed net applications. The problems for vector control created by use of insecticides in agriculture and the potential for management of resistance in both agriculture and vector-borne disease control are discussed.

Predictions of adult Anopheles albimanus densities in villages based on distances to remotely sensed larval habitats.

Remote sensing is particularly helpful for assessing the location and extent of vegetation formations, such as herbaceous wetlands, that are difficult to examine on the ground. Marshes that are sparsely populated with emergent macrophytes and dense cyanobacterial mats have previously been identified as very productive Anopheles albimanus larval habitats. This type of habitat was detectable on a classified multispectral System Probatoire d'Observation de la Terre image of northern Belize as a mixture of two isoclasses. A similar spectral signature is characteristic for vegetation of river margins consisting of aquatic grasses and water hyacinth, which constitutes another productive larval habitat. Based on the distance between human settlements (sites) of various sizes and the nearest marsh/river exhibiting this particular class combination, we selected two groups of sites: those located closer than 500 m and those located more than 1,500 m from such habitats. Based on previous adult collections near larval habitats, we defined a landing rate of 0.5 mosquitoes/human/min from 6:30 PM to 8:00 PM as the threshold for high (> or = 0.5 mosquitoes/human/min) versus low (< 0.5 mosquitoes/human/min) densities of An. albimanus. Sites located less than 500 m from the habitat were predicted as having values higher than this threshold, while lower values were predicted for sites located greater than 1,500 m from the habitat. Predictions were verified by collections of mosquitoes landing on humans. The predictions were 100% accurate for sites in the > 1,500-m category and 89% accurate for sites in the < 500-m category.

Oropouche virus. IV. Laboratory transmission by Culicoides paraensis.

Biological transmission of Oropouche (ORO) virus by Culicoides paraensis (Goeldi) has been successfully demonstrated in the laboratory. Adult Culicoides, collected in an area where ORO virus was absent, were infected by feeding on viremic hamsters and then periodically exposed to susceptible hamsters at specific intervals post-infectious blood meal. These C. paraensis were capable of biological transmission of the virus 4-9 days post-feeding on viremic hamsters circulating 6.7-9.9 log10SMLD50/ml virus. Infection rates of 54% and 80% were found for C. paraensis assayed 7 days post-feeding. Virus transmission rates for these experiments were 83% and 25%, respectively. No evidence of mechanical transmission of ORO virus by C. paraensis was observed when interrupted feeding of Culicoides on viremic hamsters was followed by feeding on susceptible hamsters.