Time to Update and Quantitative Changes in the Results of Cochrane Pregnancy and Childbirth Reviews

Background

The recommended interval between updates for systematic reviews included in The Cochrane Library is 2 years. However, it is unclear whether this interval is always appropriate. Whereas excessive updating wastes time and resources, insufficient updating allows out-of-date or incomplete evidence to guide clinical decision-making. We set out to determine, for Cochrane pregnancy and childbirth reviews, the frequency of updates, factors associated with updating, and whether updating frequency was appropriate.

Methodology/Principal Findings

Cochrane pregnancy and childbirth reviews published in Issue 3, 2007 of the Cochrane Database of Systematic Reviews were retrieved, and data were collected from their original and updated versions. Quantitative changes were determined for one of the primary outcomes (mortality, or the outcome of greatest clinical significance). Potential factors associated with time to update were assessed using the Cox proportional hazard model. Among the 101 reviews in our final sample, the median time before the first update was 3.3 years (95% CI 2.7–3.8). Only 32.7% had been updated within the recommended interval of 2 years. In 75.3% (76/101), a median of 3 new trials with a median of 576 additional participants were included in the updated versions. There were quantitative changes in 71% of the reviews that included new trials (54/76): the median change in effect size was 18.2%, and the median change in 95% CI width was 30.8%. Statistical significance changed in 18.5% (10/54) of these reviews, but conclusions were revised in only 3.7% (2/54). A shorter time to update was associated with the same original review team at updating.

Conclusions/Significance

Most reviews were updated less frequently than recommended by Cochrane policy, but few updates had revised conclusions. Prescribed time to update should be reconsidered to support improved decision-making while making efficient use of limited resources.     

Effect of light intensity on Opisthorchis viverrini cercarial shedding levels from Bithynia snails--a preliminary study

Opisthorchis viverrini requires Bithynia snails as the first intermediate host and cyprinid fish as the second intermediate host. Very low natural infection rates have been reported in Bithynia snails, but very high rates have been found in cyprinid fish in the same endemic region. This study investigated the effect of light intensity, the most important stimulus, on the quantity of O. viverrini cercariae shed from naturally infected Bithynia (Digoniostoma) siamensis goniomphalos snails. Snails were evaluated for cercariae output every hour after exposure to various light intensities for a total period of 7 h. The same infected snail was tested under different intensities of light: in the dark, and at 1000, 3000 and 5000 lx. The data showed that under exposure to 1000 and 3000 lx of light, the average percentage and number of cercariae released were higher than that exposed to 5000 lx during the first 2 h of the experiment. In contrast, under higher illumination (5000 lx) a longer time (6 h) was required to stimulate the peak emergence of cercariae. Darkness was not able to induce O. viverrini cercariae emergence. Among the three intensities of light, exposure at 1000 lx induced the highest average number of released cercariae per snail and the highest percentage of cercarial emergence within the first 2 h (125, 54.86%), followed by exposure at 3000 lx (69, 25.58%) and 5000 lx (12, 7.78%). The results suggest that the light intensity of 1000 lx for 2 h would be optimal for O. viverrini cercarial shedding from naturally infected B. (D.) siamensis goniomphalos snails.     

Fecal bacterial contamination in natural water reservoirs as an indicator of seasonal infection by Opisthorchis viverrini in snail intermediate hosts

Opisthorchis viverrini, a carcinogenic liver fluke, requires Bithynia snails as the first intermediate host, which release cercariae after ingesting fluke eggs from contaminated water. Fecal bacterial contamination and O. viverrini-infected Bithynia snails were investigated in samples collected from natural water reservoirs in Ban Phai, Chonnabot and Muang Districts (Ban Lerngpeuy) in Khon Kaen Province, northeast Thailand, where there is a high incidence of cholangiocarcinoma. Water was sampled and examined six times (February, April, June, August, October and December 2006). The most probable number (MPN) index and coliform counts were utilized to evaluate fecal contamination; the cercarial shedding method was conducted for detecting infected snails. The data revealed that all water samples had a high MPN index number, and fecal coliform levels above the WHO standard. This indicated that water in these reservoirs was contaminated with feces or manure constituents. Water sampling from Ban Lerngpeuy showed full-scale bacterial contamination (> 1609 MPN index) throughout the year. This finding was correlated with the highest prevalence of O. viverrini-infected snails, which were found nearly all year round in this area. Slightly lower fecal contamination levels were detected in water samples from Chonnabot and Ban Phai, with high MPN index numbers and coliform counts from April to October. This corresponded with the higher recovery of infected snails in June and August, but with relatively lower prevalence than those found in Ban Lerngpeuy. Among the sampling sites, the people in Ban Lerngpeuy live nearer to the reservoir than do those in Ban Phai and Chonnabot. These results indicate that fecal bacterial contamination in natural water reservoirs is an important indicator of seasonal transmission of O. viverrini eggs to snail intermediate hosts. Sanitation improvement is essential and future investigations on the sources of contamination are needed.     

Assessing resource and predator effects on habitat use of tropical small carnivores

Habitat use of animals is influenced by a combination of factors including food abundance and interactions with other species. Animals typically must forage while simultaneously avoiding predation from multiple potential predators, but habitat use in tropical forest ecosystems that assesses effects of both predation risk and resources has rarely been conducted. We used camera traps and occupancy analyses to document small mammalian carnivore occurrence in relation to food abundance and interactions with large predators. We hypothesized that habitat use of six small mammalian carnivores (≤15 kg) would be influenced by (1) abundance of resources (fruit, rodents, and streams) and/or (2) large predators. Predictions regarding food and habitat resources were only supported for one species (crab-eating mongoose, Urva urva), which was positively associated with rodents and streams. Three small carnivores (masked palm civet Paguma larvata, common palm civet Paradoxurus hermaphroditus, yellow-throated marten Martes flavigula) were affected negatively by leopard and mesopredators as predicted. Counter to our predictions, two species (masked palm civet and yellow-throated marten) showed spatial avoidance of tiger suggesting that an apex predator might also pose predation risk to small carnivores. The focal small carnivores and large predators of this study appeared to have moderately to highly overlapping temporal activity indicating no temporal avoidance. In conclusion, food resources appeared to have minimal effects for six small carnivores in this ecosystem probably due to continuous resource availability. Predation risk appeared to affect some species in terms of spatial occupancy but not in temporal activity, indicating perhaps complex, but not entirely negative interactions between larger carnivores and this guild of small carnivores. The mechanisms which facilitate co-occurrence between small carnivores and large predators may, however, operate at finer spatiotemporal scales than we investigated here.     

The shared preference niche of sympatric Asiatic black bears and sun bears in a tropical forest mosaic

Background

Ecologically similar species often coexist by partitioning use of habitats or resources. Such partitioning can occur through divergent or shared niches. We investigated overlap in habitat use and spatial co-occurrence by sympatric Asiatic black bears and sun bears in three habitats in Thailand, and thereby assessed which niche model best accounts for their coexistence.

Methods/Principal Findings

We used density of species-specific signs to assess habitat use. Signs of both bear species occurred in all three habitats, and on >60% of sampling transects. Both species fed mostly on fruit; insect feeding signs were uncommon, and were mostly from sun bears. Significant differences in habitat use occurred only in montane forest, the habitat in which fruit was most abundant; incidence of black bear sign there was six times higher than that of sun bears. Habitat use was similar between the two species in the other habitats, which comprised 85% of the area. Of 10 habitat attributes examined, fruiting tree density was the best predictor of occurrence for both species. Models that included interspecific competition (fresh foraging activity of the other species) were less supported than the top models without competition.

Conclusions/Significance

Bear species co-occurrence at both coarse and fine spatial scales and use of the same resources (fruit trees) indicated common niche preferences. However, their habitat use differed in ways expected from their physical differences: larger black bears dominated in the most fruit-rich habitat, and smaller sun bears used less-preferred insects. These results indicate broadly overlapping fundamental niches combined with asymmetric competition—features consistent with the concept of shared preference niches. This model of the niche has received little attention in ecology, but appears to be relatively common in nature.     

YHV-protease dsRNA inhibits YHV replication in Penaeus monodon and prevents mortality

Yellow head virus infects cultured shrimps and causes severe mortality resulting in a great economic loss. Haemolymph injection of dsRNA(pro) corresponding to the protease motif of YHV genome resulted in a complete inhibition of YHV replication. The effect of dsRNA lasted for at least 5 days. Injecting sequence-unrelated dsRNA(gfp) or dsRNA(TSV-pol) also resulted in an inhibition of YHV replication but at a comparatively much less extent. Shrimp mortality was monitored for 10 days when more than 90% shrimps receiving no dsRNA died within 8 dpi. However, those receiving dsRNA(pro) showed no mortality. A partial mortality was observed among the shrimps receiving dsRNA(gfp) or dsRNA(TSV-pol). Thus, Penaeus monodon possesses the sequence-specific protection to YHV infection, most likely through the RNAi pathway, in addition to sequence-independent protection. It gives a new notion that dsRNA induction of antiviral immunity in shrimp goes through two pathways, sequence-independent and sequence-dependent.     

Occurrence of Three Felids across a Network of Protected Areas in Thailand: Prey,Intraguild, and Habitat Associations

Clouded Leopard, Leopard, and Tiger are threatened felids in Southeast Asia, but little is known about the factors influencing their distributions. Using logistic regression, we assessed how habitat variables, prey detection patterns, and presence of intraguild predators affect the occurrence of these felids across 13 protected areas within Thailand. Our analysis is based on data from 1108 camera‐trap locations (47,613 trap‐nights). Clouded Leopard and Leopard are associated with habitat where Red Muntjac and Eurasian Wild Pig were most likely to be present. Tiger are associated with habitat with a higher likelihood for the presence of Gaur, Eurasian Wild Pig, and Sambar. Clouded Leopard and Tiger were both weakly associated with areas with mature evergreen forest. Besides availability of prey, associations with potential competitors also appear to influence the distribution of these felids, although the strength of these effects requires further investigation. Occurrence rates for Clouded Leopard were no different in protected areas with Leopard versus without Leopards. Leopard had similar occurrence rates regardless of the presence of Tiger, but Leopards were less likely to be detected at the same camera‐trap points with the larger felid. Our results suggest that the two most commonly photographed prey species in the study areas serve as key prey species, Eurasian Wild Pig for all three carnivores and Red Muntjac for Leopard and Clouded Leopard.     

Chitosan lactate as a nonviral gene delivery vector in COS-1 cells

The purpose of this research was to evaluate chitosan lactate (CL) of different molecular weights (MWs) as a DNA complexing agent for its efficiency in transfecting COS-1 cells (green monkey fibroblasts) and its effect on cell viability compared with polyethylenimine (PEI), a commercially available cationic polymer. CL and chitosan base dissolved in dilute acetic acid (chitosan acetate, [CA]) of different MWs (20, 45, 200, 460 kDa) and N/P ratios (2∶1, 4∶1, 8∶1, 12∶1, 24∶1) formed complexes with pSV β-galactosidase plasmid DNA. The complexes were characterized by agarose gel electrophoresis and investigated for their ability to transfect COS-1 cells compared with PEI. Additionally, the effect of CL on the viability of COS-1 cells was investigated using 3-(4,5-dimethyliazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The binding of CL/DNA and CA/DNA was dependent on chitosan MWs. The N/P ratio of CL to completely form the complex with the DNA was higher than that of CA. Both CL and CA were comparable in transfection efficiencies at an N/P ratio of 12∶1, but less efficient than PEI (P<.05). The cell viability in the presence of CL and CA at all MWs was over 90%, whereas that of PEI-treated cells was ≈50%. These results suggest the advantage of CL for in vitro gene transfection, with the ease of preparation of polymer/DNA complexes and low cytotoxicity. Published: August 4, 2006