Day-to-Day Population Movement and the Management of Dengue Epidemics

Dengue is a growing public health problem in tropical and subtropical cities. It is transmitted by mosquitoes, and the main strategy for epidemic prevention and control is insecticide fumigation. Effective management is, however, proving elusive. People’s day-to-day movement about the city is believed to be an important factor in the epidemiological dynamics. We use a simple model to examine the fundamental roles of broad demographic and spatial structures in epidemic initiation, growth and control. We show that the key factors are local dilution, characterised by the vector–host ratio, and spatial connectivity, characterised by the extent of habitually variable movement patterns. Epidemic risk in the population is driven by the demographic groups that frequent the areas with the highest vector–host ratio, even if they only spend some of their time there. Synchronisation of epidemic trajectories in different demographic groups is governed by the vector–host ratios to which they are exposed and the strength of connectivity. Strategies for epidemic prevention and management may be made more effective if they take into account the fluctuating landscape of transmission intensity associated with spatial heterogeneity in the vector–host ratio and people’s day-to-day movement patterns.     

Antidiatom activity of marine bacteria associated with sponges from San Juan Island,Washington

Crude extracts of 52 marine bacteria associated with sponges, which were collected from the sea near San Juan Island, Washington, USA, were screened using diatom attachment assays against Amphora sp., Nitzschia closterium, Sellaphora sp. and Stauroneis sp. to investigate their antidiatom activities. Among these samples, five expressed strong anti-adhesion effects on all four tested diatoms. There was no negative effect observed from those five active samples on the growth of Amphora sp. Those five active samples were prepared from respective isolates, which all belonged to the genus Bacillus based on 16S rRNA gene sequencing analysis. The results of present study indicate that Bacillus may play important roles for sponges’ chemical defence against biofouling of diatoms and that the metabolites of Bacillus may be a potential source of natural antifouling compounds.     

An unusual macrourid larva (Gadiformes) from San Juan Island, Washington, USA

An unusual macrourid larva was collected in Friday Harbor, San Juan Island, Washington, USA. This specimen is remarkable in appearance having very long anterior dorsal- and pelvic-fin rays, with flattened distal ends free of the fin membrane, and a long, whiplike, heavily pigmented caudal filament. It is similar to smaller Coryphaenoides pectoralis larvae reported from the California Current region, and different from larger specimens of C. pectoralis from the northern North Pacific. Counts and other morphological similarities suggest that this larva should be tentatively assigned to genus Coryphaenoides.     

Wood-inhabiting marine fungi from San Juan Island, with special reference to ascospore appendages

Forty-four species were found on driftwood–two Basidiomycotina, six Deuteromycotina and 36 Ascomycotina. The most common species were Haligena elaterophora, Herpotrichiella ciliomaris, Remispora maritima, Halosphaeria appendiculata and Ceriosporopsis halima. Three species not previously illustrated are discussed. Ten new records for Washington State, U.S.A. are listed in Table 1. SEM observations on spore appendages in Banhegyia, Ceriosporopsis, Haligena, Herpotrichiella, Lulworthia, Remispora and Torpedospora are given.     

The Role of Imported Cases and Favorable Meteorological Conditions in the Onset of Dengue Epidemics

Background

Travelers who acquire dengue infection are often routes for virus transmission to other regions. Nevertheless, the interplay between infected travelers, climate, vectors, and indigenous dengue incidence remains unclear. The role of foreign-origin cases on local dengue epidemics thus has been largely neglected by research. This study investigated the effect of both imported dengue and local meteorological factors on the occurrence of indigenous dengue in Taiwan.

Methods and Principal Findings

Using logistic and Poisson regression models, we analyzed bi-weekly, laboratory-confirmed dengue cases at their onset dates of illness from 1998 to 2007 to identify correlations between indigenous dengue and imported dengue cases (in the context of local meteorological factors) across different time lags. Our results revealed that the occurrence of indigenous dengue was significantly correlated with temporally-lagged cases of imported dengue (2–14 weeks), higher temperatures (6–14 weeks), and lower relative humidity (6–20 weeks). In addition, imported and indigenous dengue cases had a significant quantitative relationship in the onset of local epidemics. However, this relationship became less significant once indigenous epidemics progressed past the initial stage.

Conclusions

These findings imply that imported dengue cases are able to initiate indigenous epidemics when appropriate weather conditions are present. Early detection and case management of imported cases through rapid diagnosis may avert large-scale epidemics of dengue/dengue hemorrhagic fever. The deployment of an early-warning surveillance system, with the capacity to integrate meteorological data, will be an invaluable tool for successful prevention and control of dengue, particularly in non-endemic countries.     

Palm Community Structure and Land Cover Changes in the San Juan Biological Corridor, Costa Rica

Biological corridors connect forest fragments, minimize the isolation of remaining habitats, and reduce the negative impact of fragmentation. Important studies in a corridor include documentation of land cover and the relationships between the plant community and land cover changes. In this study, density, species richness, and species diversity of palms of different life stages and growth forms were documented in forty 10 × 10 m census plots in the San Juan Biological Corridor (SJBC), Costa Rica. Changes in the percent cover of agricultural, partially forested, and forested lands from 1979 to 2001 were quantified based on existing land classifications. Associations between these palm community characteristics and the reduction in forest cover in 200-m and 1000-m annuli surrounding the census plots were investigated. These palm community characteristics were spatially interpolated to examine their distributions in SJBC. The community characteristics of palms of all growth forms varied among census plots. Forested lands in SJBC decreased from 88 percent to 26 percent during 1979–2001, while the percentage cover of agricultural and partially forested lands increased. The annual deforestation rate was 0.8 percent from 1979 to 1992, 4.3 percent from 1992 to 1997, and 7.5 percent from 1997 to 2001. Overall, palm community characteristics of small-canopy palms, dwarf palms, and cotyledonous seedlings had lower values with a lower percentage forest cover. The spatially interpolated palm community characteristics were consistently greatest within or adjacent to protected areas. This study demonstrates the complexity of the landscape and the effect of loss of adjacent forests on the palm community.     

Circulating nutrient concentrations in free-ranging Humboldt penguins (Spheniscus humboldti) in Punta San Juan,Peru

Free-ranging Humboldt penguin (HP, Spheniscus humboldti) populations are under pressure from resource competition with industrial fisheries, habitat loss, and El Niño Southern Oscillation events. Foraging patterns for this top marine predator change during periods of aberrant oceanographic conditions and scarce fish stock numbers. These radical dietary fluctuations can lead to poor fertility, early embryonic death, poor hatchability, suppressed immune function, high chick mortality, and illness. To understand the variability of nutrient status in reproductive seasons, we measured select circulating nutrient concentrations (fat-soluble vitamins A, D, E, and carotenoids, fatty acids, amino acids, minerals, and electrolytes) of 105 HP at Punta San Juan, Peru during the first reproductive seasons of 2007 and 2008. We determined significant differences in nutrient status between sexes, years of sampling, and reproductive stages. Males (4.5 ± 0.38 kg) weighed more than females (4.0 ± 0.29 kg) and exhibited higher concentrations of vitamin A (0.71 ± 0.11 vs. 0.61 ± 0.12 µg/ml) and docosahexaenoic acid (6.70 ± 1.61 vs. 5.65 ± 1.59%). Males also displayed lower concentrations of β-carotene (0.01 ± 0.01 vs. 0.012 ± 0.001 µg/ml) and phosphorus (3.43 ± 0.83 vs. 4.40 ± 1.66 mg/dl). Comparison between the 2 years showed most circulating amino acid concentrations were higher in 2007. Significant differences in circulating amino acids and vitamins were also noted between different reproductive stages. These results demonstrate concentrations of nutrients can vary due to the physiological state of the animal, as well as the overall dynamics of their marine ecosystem habitat.     

Succession of Carrion Fauna in the Arid Region of San Juan Province, Argentina and Its Forensic Relevance

The succession of carrion fauna and the decomposition stages were studied in the arid environment of San Juan Province, Argentina (31°32??34.7?? S; 68°34??39.4?? W). Two pig carcasses (Sus scrofa) were placed in wire mesh cages, 100?m apart from each other. Each carcass was surrounded by pitfall traps, and a modified Malaise trap was placed above. Daily samplings were carried out to collect the insects present in the carcasses and the traps, and body and environmental temperature were measured. The main colonizer species was Chrysomya albiceps (Wiedemann) and its larvae were dominant over other Diptera. The first adult blowflies emerged at 8.9?days. The time to reach the remains stage was 8?days shorter than for other South American sites. We recorded the early arrival of adult Dermestes maculates De Geer and Dermestes ater De Geer 2?days after the beginning of the assay, and larvae of these species were recorded 4?days after. We determined a 1.5-day error in the postmortem interval estimation using the temperatures measured in the assay and those recorded by the nearest meteorological station.     

Inter- and Intraspecific Variations of Bacterial Communities Associated with Marine Sponges from San Juan Island,Washington

This study attempted to assess whether conspecific or congeneric sponges around San Juan Island, Washington, harbor specific bacterial communities. We used a combination of culture-independent DNA fingerprinting techniques (terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis [DGGE]) and culture-dependent approaches. The results indicated that the bacterial communities in the water column consisted of more diverse bacterial ribotypes than and were drastically different from those associated with the sponges. High levels of similarity in sponge-associated bacterial communities were found only in Myxilla incrustans and Haliclona rufescens, while the bacterial communities in Halichondria panicea varied substantially among sites. Certain terminal restriction fragments or DGGE bands were consistently obtained for different individuals of M. incrustans and H. rufescens collected from different sites, suggesting that there are stable or even specific associations of certain bacteria in these two sponges. However, no specific bacterial associations were found for H. panicea or for any one sponge genus. Sequencing of nine DGGE bands resulted in recovery of seven sequences that best matched the sequences of uncultured Proteobacteria. Three of these sequences fell into the sponge-specific sequence clusters previously suggested. An uncultured alphaproteobacterium and a culturable Bacillus sp. were found exclusively in all M. incrustans sponges, while an uncultured gammaproteobacterium was unique to H. rufescens. In contrast, the cultivation approach indicated that sponges contained a large proportion of Firmicutes, especially Bacillus, and revealed large variations in the culturable bacterial communities associated with congeneric and conspecific sponges. This study revealed sponge species-specific but not genus- or site-specific associations between sponges and bacterial communities and emphasized the importance of using a combination of techniques for studying microbial communities.Marine sponges (phylum Porifera) harbor a remarkable array of microorganisms, including bacteria (51, 54), unicellular algae (50), cyanobacteria (45, 48), dinoflagellates (14), zoochlorellae (58), and members of the domain Archaea (33). Of these microorganisms, bacteria are the most dominant group of microbial associates in sponges and can account for up to 40 to 50% of a sponge''s biomass (17). The density of bacteria can be up to 10⁸ to 10¹⁰ bacteria per g (wet weight) of sponge (18). The great abundance of bacteria in sponges caused workers to coin the term “bacteriosponges” (35) and has attracted much research interest in the role and specificity of the sponge-bacterium association.There are generally two pathways by which sponges may acquire their bacterial associates. The first pathway is filter feeding and selective retention of bacteria (44). Bacteria in the surrounding seawater can be captured by sponges when sponges filter the food particles out of the water column. The bacteria that resist digestion by sponge choanocytes and archaeocytes can survive and live inside the sponges. Sponge-associated bacterial communities acquired via this pathway are therefore heavily influenced by the type of bacteria in the water column. The second pathway is vertical transmission of bacterial associates from adult sponges to their progeny (10, 40, 49). Bacteria acquired through this pathway may exhibit specificity for genera or species of sponges due to coevolution (for a review, see reference 44).Sponge-bacterium symbioses are often mutualistic; while bacteria may benefit from the favorable nutritional conditions in sponges (18, 44), some bacterial associates may help their hosts eliminate metabolic waste (4), stabilize the sponge skeleton (36), and defend against pathogens, predators, or competitors via the production of bioactive secondary metabolites (5, 21, 39, 47). In addition, some cyanobacterial symbionts are a source of nutrients for their hosts because of their photosynthetic and nitrogen-fixing abilities (3, 57).There is a large body of knowledge concerning the possible roles of bacterial associates in sponges, but whether sponges harbor specific bacterial communities deserves more detailed study. Many previous investigations demonstrated that associated bacterial communities in certain species of sponges were highly similar and consistently different from the bacterial communities in the ambient environment (6, 22, 46). For instance, Hentschel et al. (16) showed that there were uniform microbial communities in the marine sponges Aplysina aerophoba, Rhopaloeides odorabile, and Theonella swinhoei from different geographic regions that were distinct from those in the water column or in sediments. In addition, Friedrich et al. (12) demonstrated that the composition of sponge-associated bacterial communities was resistant to environmental perturbations resulting from transplantation to different habitats. These studies suggest that there is a stable, specific, and perhaps mutualistic relationship between the two types of organisms (44). However, some bacterium-sponge symbioses do not appear to be consistent. For instance, Wichels et al. (56) demonstrated that the bacterial communities associated with the North Sea sponge Halichondria panicea varied substantially over time. Qian et al. (34) and Lee et al. (25) showed that the congeneric Callyspongia and Mycale sponges from different biogeographic regions had different bacterial associates. Although the discrepancies may be attributed to the methods employed in different studies, whether consistent sponge-bacterium associations occur in different species or genera of sponges remains unclear. Furthermore, most of the previous studies focused on only one sponge species or involved a few sponges from geographically separated regions. So far, there has been no large-scale study comparing the bacterial communities associated with sponges of different genera and species.In this study, we compared the bacterial communities associated with marine sponges around San Juan Island, Washington, in order to investigate the specificity of congeneric and conspecific sponge-associated bacterial communities. Most previous studies have relied on only one method to assess the bacterial communities, limiting the resolution of community assessments. In addition, different studies have used different approaches to address the same question, creating uncertainties and making generalizations difficult. Here, we employed both culture-independent and -dependent approaches to compensate for the limitations of different methods and to obtain a more reliable assessment of the associated bacterial communities. We used two DNA fingerprinting techniques, terminal restriction fragment length polymorphism (TRFLP) (27) and denaturing gradient gel electrophoresis (DGGE) (11). TRFLP is an effective, sensitive, high-throughput technique that differentiates bacterial community structures, while DGGE allows subsequent identification of bacteria of interest by excision and sequencing of specific bands. Both techniques have been successfully and widely used for characterization of bacterial communities in marine samples (13, 26, 28, 43, 56). In addition, bacteria associated with sponges were isolated using cultivation methods and identified by comparative analysis of 16S rRNA gene sequences. Phylogenetic affiliations of the isolates were determined and compared for different samples in order to study the specificity of the sponge-associated culturable bacterial communities.     

Antimicrobial and antioxidant activities of Gentianella multicaulis collected on the Andean Slopes of San Juan Province, Argentina

The infusion of the aerial parts of Gentianella multicaulis (Gillies ex Griseb.) Fabris (Gentianaceae), locally known as 'nencia', is used in San Juan Province, Argentina, as stomachic and as a bitter tonic against digestive and liver problems. The bioassay-guided isolation of G. multicaulis extracts and structural elucidation of the main compounds responsible for the antifungal and free radical scavenging activities were performed. The extracts had strong free radical scavenging effects in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay (45-93% at 10 microg/mL) and ferric-reducing antioxidant power (FRAP) assay at 200 microg/mL. Demethylbellidifolin (4) had high antioxidant activity in the DPPH and FRAP assay. The dermatophytes Microsporum gypseum, Trichophyton mentagrophytes, and T. rubrum were moderately inhibited by the different extracts (MIC values of 125-250 microg/mL). Demethylbellidifolin (4), bellidifolin (5), and isobellidifolin (6) showed an antifungal effect (MIC values of 50 microg/mL), while swerchirin (3) was less active with a MIC value of 100 microg/mL. In addition, oleanolic acid (1) and ursolic acid (2) were also isolated. These findings demonstrate that Gentianella multicaulis collected in the mountains of the Province of San Juan, Argentina, is an important source of compounds with antifungal and antioxidant activities.