Alkali cation specific adsorption onto fcc(111) transition metal electrodes.

The presence of alkali cations in electrolyte solutions is known to impact the rate of electrocatalytic reactions, though the mechanism of such impact is not conclusively determined. We use density functional theory (DFT) to examine the specific adsorption of alkali cations to fcc(111) electrode surfaces, as specific adsorption may block catalyst sites or otherwise impact surface catalytic chemistry. Solvation of the cation-metal surface structure was investigated using explicit water models. Computed equilibrium potentials for alkali cation adsorption suggest that alkali and alkaline earth cations will specifically adsorb onto Pt(111) and Pd(111) surfaces in the potential range of hydrogen oxidation and hydrogen evolution catalysis in alkaline solutions.

Risk factors for Nipah virus encephalitis in Bangladesh.

Nipah virus (NiV) is a paramyxovirus that causes severe encephalitis in humans. During January 2004, twelve patients with NiV encephalitis (NiVE) were identified in west-central Bangladesh. A case-control study was conducted to identify factors associated with NiV infection. NiVE patients from the outbreak were enrolled in a matched case-control study. Exact odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by using a matched analysis. Climbing trees (83% of cases vs. 51% of controls, OR 8.2, 95% CI 1.25-infinity) and contact with another NiVE patient (67% of cases vs. 9% of controls, OR 21.4, 95% CI 2.78-966.1) were associated with infection. We did not identify an increased risk for NiV infection among persons who had contact with a potential intermediate host. Although we cannot rule out person-to-person transmission, case-patients were likely infected from contact with fruit bats or their secretions.

Regulation of rodent-borne viruses in the natural host: implications for human disease.

Prevalence and transmission rates of rodent-borne viruses within host populations vary in time and space and among host-virus systems. Improving our understanding of the causes of these variations will lead to a better understanding of changes in disease risk to humans. The regulators of prevalence and transmission can be categorized into five major classes: (1) Environmental regulators such as weather and food supply affect transmission rates through their effect on reproductive success and population densities. (2) Anthropogenic factors, such as disturbance, may lead to ecosystem simplification and decreased diversity. These changes favor opportunistic species, which may serve as reservoirs for zoonotic viruses. (3) Genetic factors influence susceptibility of mice to infection or capacity for chronic shedding and may be related to population cycling. (4) Behavioral factors, such as fighting, increase risk of transmission of some viruses and result in different patterns of infection between male and female mice. Communal nesting may result in overwinter transmission in colder climates. (5) Physiologic factors control host response to infection and length of time the host remains infectious. Risk prediction is difficult because these regulators are numerous and often interact, and the relative importance of each varies according to the host species, season, year, and geographic location.

Leukemia inhibitory factor induces leukocyte infiltration and cartilage proteoglycan degradation in goat joints.

Recent studies have implicated leukemia inhibitory factor (LIF) in human joint disease. LIF is produced by cultured synovial cells and articular chondrocytes, stimulates cartilage and bone resorption, and has been detected in inflammatory exudates from arthritic joints. The aim of this study was to evaluate the effect of intraarticular injections of human recombinant LIF in the goat. Endotoxin-free, sterile normal saline containing 1 micrograms recombinant human LIF (rhLIF) was injected into the right radiocarpal joints (RCJs) of eight angora goats. The left RCJs were injected with an equivalent volume of vehicle alone (n = 6) or vehicle containing 1 micrograms human albumin (n = 2). Goat joints were examined for clinical features of inflammation, and synovial fluid (SF) was aspirated on days 0, 2, and 6 postinjection. Leukocyte counts and concentrations of keratan sulfate, IL-1 beta, and TNF-alpha were determined in the SF. Proteoglycan synthesis was determined ex vivo in cartilage explants obtained on day 6 postinjection. A statistically significant increase in joint swelling and effusion volume was observed in LIF-injected joints but not in control joints. In the LIF-injected RCJs, the leukocyte count increased from 82 +/- 9 cells/microliters before injection to 10,300 +/- 3357 cells/microliters at day 2 postinjection (p < 0.005) and declined to 678 +/- 113 cells/microliters at day 6 postinjection. Polymorphonuclear leukocytes and monocyte/macrophages predominated in the infiltrate. No appreciable change in leukocyte counts was observed in control joints.(ABSTRACT TRUNCATED AT 250 WORDS)

The proinflammatory and chondral activities of leukemia inhibitory factor in goat joints are partially a function of interleukin-1.

We wished to determine if the effects of injected recombinant human leukemia inhibitory factor (LIF) are a function of endogenous goat interleukin-1 (IL-1) production and, conversely, if the effects of injected recombinant human IL-1 are a function of endogenous LIF production in goat radiocarpal joints (RCJ). In preliminary experiments, murine LIF binding protein (MuLBP) and recombinant HuIL-1RA were found to independently attenuate the cartilage proteoglycan resorbing activity of goat synovial membrane-conditioned medium (GSMCM), implying activity against goat LIF and goat IL-1, respectively. The present study shows that the proinflammatory and chondral actions of rHuLIF in goat RCJ are partially attenuated by rHuIL-1RA. This implies that a small but important component of the in vivo activity of rHuLIF is a result of IL-1 production in the synovial joint. With the exception of proteoglycan synthesis, the absence of significant effects by MuLBP on the actions of rHuIL-1alpha in goat RCJ suggests that the proinflammatory and chondral effects of IL-1alpha in vivo are probably not mediated by LIF.

Patterns of infection with Laguna Negra virus in wild populations of Calomys laucha in the central Paraguayan chaco.

In 1995, an outbreak of hantavirus pulmonary syndrome occurred in the central Paraguayan chaco. The primary reservoir of the virus, Laguna Negra virus, was identified as the vesper mouse, Calomys laucha. Over a 15-month period, we collected 1,090 small mammals at 12 locations representing 4 habitats common in the central Paraguayan chaco. Calomys laucha was common in agricultural habitats and uncommon in the native forest habitat. Populations of C. laucha were greater during the dry season months and declined during the wet season. A total of 643 small mammals were tested for antibodies cross-reactive to Sin Nombre virus. All of the antibody-positive animals were C. laucha (crude antibody prevalence ratio 12.1% [25 of 206]). Antibody prevalence ratio increased with body size and was more common among male (18%; n = 115) than among female (4%; n = 96) vesper mice. Antibody prevalence ratio was highest among animals from cropland habitats (18%; n = 72), followed by thorn scrub (13%; n = 46) and pastureland (7%; n = 81) and may be positively correlated to the proportion of C. laucha in the small mammal community. These data suggest that community-level dynamics, in addition to population-level dynamics, may be involved in the transmission of the virus through natural populations of vesper mice.

Antibody to sin nombre virus in rodents associated with peridomestic habitats in west central Montana.

Most human cases of hantavirus pulmonary syndrome are acquired in the peridomestic environment, yet studies of the ecology and infection dynamics in the reservoir host, the deer mouse (Peromyscus maniculatus), have focused on sylvan populations. We describe a 2.5-year study of hantavirus infection in rodents associated with peridomestic habitats in west central Montana. Antibodies reactive with Sin Nombre virus (SNV) were found in five species. Overall SNV antibody prevalence was highest among deer mice (25% of individuals tested). As has been demonstrated for sylvan populations, the antibody-positive component of the deer mouse population consisted of a higher proportion of adults and males. However, the prevalence of antibodies to SNV was higher in this study than has been reported in most sylvan studies. The average monthly proportion of deer mouse blood samples with antibodies to SNV ranged from approximately 20% to 25% and was highest in the late spring/early summer. The higher SNV antibody prevalence in peridomestic compared with sylvan settings may be related to behavioral differences and/or potentially longer survival of the virus deposited inside buildings. Peridomestic settings presented higher concentrations of virus and may present a higher risk of human infection than do sylvan settings.

Experimental evaluation of rodent exclusion methods to reduce hantavirus transmission to humans in rural housing.

An experimental assessment of methods to reduce rodent infestations in rural housing was conducted in Yosemite National Park, California, Sequoia/Kings Canyon National Parks, California, and Shenandoah National Park, Virginia. During pretreatment surveys, nearly all (63 of 68) selected units had past or ongoing rodent activity inside. Active infestations were found in 58.8% of the units. Peromyscus spp. represented 91.2% of all animals caught inside housing units. Despite little harborage, rodent activity was common near housing (290 animals/2,254 trap nights). The most common species present was Peromyscus maniculatus (43-50% of all captures). This species was especially frequent (49-87% of Peromyscus captures) around the foundations of housing units. Habitat had little effect on captures. There were 1.8 Peromyscus caught per unit along the foundations of housing in modified rural settings with grass lawns compared with 1.2 Peromyscus caught per unit in sites located in mature woodlands. During autumn of 1994, randomly selected housing units were rodent proofed by sealing openings associated with chases, roof eaves, and attics with insulation and wire mesh. Housing was examined and the fauna was resampled in the spring-summer of 1995. Rodent-proofed houses were infested significantly less often (3 of 28) than control houses (13 of 36) (P = 0.02) and the intensity of infestation was lower in experimental houses (6 versus 23 mice/treatment). More than 25% of the mice trapped inside the houses had been marked outside the houses during the three-day surveys, demonstrating movement of mice adjacent to the buildings into not rodent-proofed housing. As in the previous autumn, most of the animals captured in (98.9%) and along the foundations of the houses (77.5%) were Peromyscus spp. These results demonstrate that Peromyscus frequently invade rural housing but rodent-proofing effectively eliminates or substantially reduces rodent activity.

Prevalence of infection with Junin virus in rodent populations in the epidemic area of Argentine hemorrhagic fever.

We report the results of indirect fluorescent antibody screening for antibody to Junin virus in 1,101 sera from small mammals captured on two mark-recapture grids in the epidemic area of Argentine hemorrhagic fever. Twenty-six of 29 seropositive animals were the cricetid rodent Calomys musculinus, for a 30-month prevalence of 7.9% in that species. Combining these data with previously published data on antigen detection provided an estimated total prevalence of infection of 10.9% for this, the principal reservoir species. Other infected species included two cricetids, C. laucha and Bolomys obscurus, and a predatory carnivore, Galictis cuja. Approximately half of infected animals simultaneously carried serum antibody and antigen in blood and saliva, some for 29-61 days. Except for C. laucha, which was associated with crop habitats, seropositive animals were strongly associated with the relatively rare roadside and fence-line habitats. Seropositive C. musculinus were predominantly males in the oldest age and heaviest body mass classes, and seropositive males were twice as likely to have body scars as seronegative males. These observations suggest that most infections were acquired through horizontal transmission and that aggressive encounters among adult, male C. musculinus in relatively densely populated roadside and fence-line habitats are an important mechanism of transmission of Junin virus within reservoir populations.

Longitudinal studies of Sin Nombre virus in deer mouse-dominated ecosystems of Montana.

Sin Nombre virus (SNV), hosted by the deer mouse (Peromyscus maniculatus), is the primary etiologic agent of Hantavirus pulmonary syndrome (HPS) in North America. To improve our understanding of the epidemiology of HPS in the western United States, we conducted studies of population dynamics and SNV antibody prevalence in deer mouse populations for 6 years on 12 mark-recapture grids in Montana. Monthly numbers of deer mice ranged from zero to over 170 on 1-hectare grids. SNV antibody prevalence was higher than observed in studies in other parts of the United States, averaging 13% (0% to 50%), and peaking in May or June each year. Antibody-positive mice were older (heavier) (78% of positives were adults versus 52% of negatives) and more likely to be males (61% of positives versus 53.4% of negatives). A higher proportion of antibody-positive deer mice of all age-mass classes had scars than did antibody-negative mice. Month-to-month survivorship of antibody-positive adult mice was similar to that of antibody-negative mice, but survival of young antibody-positive deer mice was lower than antibody-negative deer mice. This is the first study to clearly suggest a detrimental effect of SNV infection on deer mice.

Isolation, genetic diversity, and geographic distribution of Bayou virus (Bunyaviridae: hantavirus).

Bayou hantavirus, previously implicated in human hantavirus pulmonary syndrome in Louisiana, was isolated from a rice rat (Oryzomys palustris) captured in Georgia. The presence of antibody among rice rats captured throughout the southeastern United States and the extent of diversity among the genetic variants of Bayou viruses suggest that the rice rat is the most likely natural reservoir of the virus and that both virus and host have probably co-evolved for some years.

Prevalence of antibodies to arenaviruses in rodents from the southern and western United States: evidence for an arenavirus associated with the genus Neotoma.

The objectives of this study were to extend our knowledge of the geographic distribution and rodent host range of arenaviruses in North America. Sera from wild rodents collected from the southern and western United States were tested for antibody against Tamiami, Pichinde, Junin, and lymphocytic choriomeningitis viruses, using an indirect fluorescent antibody test. Antibody to at least one arenavirus was found in 220 (3.1%) of 7,106 rodents tested. The antibody-positive animals included Mus musculus from Florida and Texas; Neotoma albigula from Arizona, Colorado, and New Mexico; N. fuscipes and N. lepida from California: N. mexicana from Arizona, New Mexico, and Utah; N. stephensi from Arizona and New Mexico; and Oryzomys palustris and Sigmodon hispidus from Florida. Sigmodon hispidus seropositive for Tamiami virus were found only in Florida (156 [27.0%] of 578 tested), although 463 hispid cotton rats from outside that state were examined. High-titered antibodies to Tamiami virus were present in sera from S. hispidus, (geometric mean antibody titer [GMAT] of 1:792), whereas sera from Neotoma spp. reacted at high titer to both Tamiami (GMAT = 1:905) and Pichinde (GMAT = 1:433) viruses. The results suggest that arenaviruses are widely distributed in the southern United States and that one or more indigenous arenaviruses are associated with Neotoma spp. in North America.

Junin virus activity in rodents from endemic and nonendemic loci in central Argentina.

Small mammals were trapped during a 21-month period at 27 farm sites in 15 localities within and beyond the known endemic area for Argentine hemorrhagic fever (AHF). Prevalence of Junin virus (JV) was assessed by antigen-capture enzyme immunoassay (ELISA) on samples of body fluids and/or organs from 3, 282 captured rodents. Infection in rodent populations was variable (0-3.7%) among localities but, in all cases, was lower than previously reported rates. Overall prevalence was 1.4% in the AHF epidemic area, 0.6% in the historic (currently low incidence of AHF) area, and 0.4% in two localities beyond the previously defined endemic area. These low values underestimate the actual prevalence of JV, as ELISA validation by virus isolation indicated a sensitivity of 30% and a specificity of 99%. Of 37 positive rodents, 28 (76%) were of two species: Calomys musculinus (23 animals) and C. laucha (5 animals). Antigen also was found in three Akodon azarae, four Bolomys obscurus, one Mus musculus, and one Oxymycterus rufus, and JV was isolated from two Oligoryzomys flavescens. Three of these rodent species (B. obscurus, O. flavescens, and O. rufus) have heretofore not been implicated in JV maintenance in the field. Evidence suggests that the AHF endemic area may continue to expand northward.

A longitudinal study of Junin virus activity in the rodent reservoir of Argentine hemorrhagic fever.

We monitored Junin virus (JV) activity in rodent populations for 30 months at seven mark-recapture grids located in agricultural fields and adjacent roadsides and fence lines in endemic and nonendemic areas of Argentine hemorrhagic fever. Blood and oral swabs taken from rodents captured at five-week intervals were analyzed by enzyme-linked immunosorbent assay for JV antigen (Ag). Calomys laucha and C. musculinus were the most frequently captured rodents, making up 47% and 22% of captures, respectively. Of 41 Ag-positive captures, 37 were C. musculinus and four were C. laucha; 34 were from two trapping grids in the same locality. Antigen-positive Calomys were more frequently male (76%), and were found significantly more frequently among the oldest animals and the largest body mass classes. These patterns, combined with the greater mobility and higher frequencies of wounds among males than females, implicated horizontal transmission as the primary route of JV transmission between rodents. Seasonal maximum levels in JV prevalence (up to 25% of captured Ag-positive C. musculinus) occurred during periods of maximal population densities of Calomys. Spatial distribution of Ag-positive rodents reflected habitat preferences; most Ag-positive C. musculinus were captured from border habitats (roadsides and fence lines), and all Ag-positive C. laucha were captured in crop fields. These distinct, but previously undocumented, habitat preferences suggest that the disease in humans may be related to exposures to the primary reservoir species, C. musculinus, in border habitats rather than in crop fields.

Patterns of association with host and habitat: antibody reactive with Sin Nombre virus in small mammals in the major biotic communities of the southwestern United States.

The distribution and prevalence of antibody reactive with Sin Nombre virus were determined in mammals in biotic communities of the southwestern United States. Small mammals (n = 3,069) of 69 species were trapped in nine communities from lower Sonoran desert to alpine tundra. Antibody was found in rodents from all communities (overall prevalence = 6.3%); prevalence was lowest at the altitudinal and climatic extremes (0.4% in desert and 2.0% in alpine tundra). Antibody occurred in 11% of 928 deer mice, 20% of 355 brush mice, 23% of 35 western harvest mice, and 12% of 24 Mexican voles. No infected deer mice were found in desert habitat; prevalence varied from 4% in chaparral to 17% in pinyon-juniper. Brush mice were frequently infected in chaparral and montane forest (25%). Seropositivity was higher in males and in heavier animals, suggesting horizontal transmission among adult males. Decreasing prevalence with age among the youngest deer mice suggests that infected dams confer passive immunity to pups.

An outbreak of hantavirus pulmonary syndrome in western Paraguay.

During an investigation of hantavirus pulmonary syndrome (HPS) in Paraguay in 1995, sera from persons with HPS-like illness, houshold contacts of confirmed HPS case-patients, and a sample of the area residents were analyzed by ELISA for antibodies to Sin Nombre virus (SNV). Rodent serosurveys and analysis of precipitation records were also conducted. Twenty-three of 24 available probable cases were SNV antibody-positive, 17 of whom were ill between July 1995 and January 1996. Four (14.8%) of 27 case-contacts and 44 (12.8%) of 345 community residents were also seropositive. Calomys laucha (vesper mouse) was the most common rodent species captured and the most frequently SNV-seropositive. Rainfall in May 1995 was 10-fold greater than that seen in May over the preceding 11 years. This 17 case-cluster represents the largest documented outbreak since HPS was first recognized in 1993. Calomys laucha is the likely primary rodent reservoir for a SNV-like hantavirus in western Paraguay. Fluctuations in monthly precipitation rates may have contributed to increased risk for HPS in this region.

Characterization of Oliveros virus, a new member of the Tacaribe complex (Arenaviridae: Arenavirus).

Oliveros virus is an agent isolated in cell culture from Bolomys obscurus (Rodentia, Muridae, Sigmodontinae) captured on the central Argentine pampa. Oliveros virus was shown to be related to members of the Tacaribe complex of the family Arenaviridae by immunofluorescent antibody (IFA) tests, electrophoretic pattern of viral proteins, and morphology as observed by electron microscopy. It was distinct from 12 other arenaviruses by a combination of plaque-reduction neutralization tests, comparison of endpoint titers among cross-IFA tests, and comparison of viral RNA sequence data. This agent is the third new arenavirus from South America described within the last three years.

Black Creek Canal Virus infection in Sigmodon hispidus in southern Florida.

A total of 1,500 small mammals were collected and tested for antibodies cross-reactive to Sin Nombre virus (Hantavirus: Bunyaviridae) at 89 sites in a 1,600 km2 study area of southern Florida. More than 95% of the 123 seropositive animals were cotton rats (Sigmodon hispidus), suggesting infection by Black Creek Canal Virus, although seroreactive Rattus rattus (5 of 294) and Peromyscus gossypinus (1 of 39) also were captured. Crude seroprevalence in S. hispidus was 11%. Seroprevalence increased with body size and was more common in male (18%; n=451) than in female (6%; n=593) cotton rats. Infection within S. hispidus populations was widespread throughout the study area. Prevalence ranged from 0% to 60% at sites where more than five cotton rats were sampled but was not only a function of sample size. Sites with seropositive cotton rats were geographically clustered compared with sites with no seropositive cotton rats. Clustering was not due to the spatial distribution of sites with few animals, season of collection, or sex bias of animals captured at these sites. However, sites with no seropositive animals had an excess of animals in the intermediate size class (60-99 g) and a deficit of the largest and smallest animals. These data suggest that population structure within the habitat mosaic may play a significant role in the spatial distribution of hantavirus infection in local populations of reservoir species.

A survey of hantavirus antibody in small-mammal populations in selected United States National Parks.

Hantavirus activity in 39 National Parks in the eastern and central United States was surveyed by testing 1,815 small mammals of 38 species for antibody reactive to Sin Nombre virus. Antibody-positive rodents were found throughout the area sampled, and in most biotic communities. Antibody was detected in 7% of 647 deer mice (Peromyscus maniculatus), 2% of 590 white-footed mice (P. leucopus), 17% of 12 rice rats (Oryzomys palustris), 3% of 31 cotton rats (Sigmodon hispidus), and 33% of 18 western harvest mice (Reithrodontomys megalotis). Antibody was also found in three of six species of voles, and in one of 33 chipmunks (Tamias minimus). Prevalence among Peromyscus was highest in the northeast. Although few cases of hantavirus pulmonary syndrome have been identified from the eastern and central regions, widespread infection in reservoir populations indicates that potential exists for human infection throughout much of the United States.

Arthropod venom citrate inhibits phospholipase A2.

Citrate has been identified as a major component of honey bee (Apis mellifera) venom by gas liquid chromatography-mass spectrometry. A citrate concentration of 9% was found for dried bee venom by a coupled enzyme assay, aconitase-isocitric dehydrogenase. A liquid honey bee venom would contain 140 mM citrate concentration (if the solids content were 30%). Bee venom phospholipase was inhibited at a 43% level with a citrate concentration of 20 mM and calcium ion at 3 mM with the enzyme assay. Citrate was also found in the venoms of bumble bee, Bombus fervidus, 7%; yellow jacket, Vespula maculifrons, 4%; scorpion, Centruroides sculpturatus, 8%; tarantula, Grammastola cala, 8% and brown recluse spider venom gland extract, Loxoceles reclusa, 1.5% based on dried venom solids. Citrate may serve as an endogenous inhibitor of divalent metal ion-dependent enzymes in arthropod venoms as described by Francis et al. (1992, Toxicon 30, 1239-1246). Many arthropod venoms contain calcium-dependent phospholipases. A direct effect of citrate as a venom component may be possible. The presence of citrate in venoms must be considered in research on receptors, ion channels and divalent ion-dependent toxins.