Connectivity,diversity, and hybridization between two endemic fish species (Percilia spp.) in a complex temperate landscape

The identification of closely related species with partially overlapping distributions is fundamental for effective conservation. Here we analyzed 28 sequenced microsatellites, mtDNA sequences, and morphological data, to describe the connectivity, genetic relationship, and distribution of Percilia gillissi and Percilia irwini, two endangered species inhabiting two contiguous watersheds in Chile (Itata and Biobío). We provide evidence of discordance in the spatial distribution of the two genomes (nuclear and mitochondrial). Three large clusters were identified with microsatellites, with one cluster straddling both watersheds. Three clusters were also evident in mtDNA with one cluster straddling both watersheds and the other two restricted to the Itata watershed’s northern reaches. Analyses of both microsatellite and mtDNA identified P. gillissi in the Itata watershed northern reaches and P. irwini in the Biobío watershed. Fish were detected in the Itata watershed that carried mtDNA characteristic of P. irwini but nuclear microsatellite profiles of P. gillissi suggesting an incomplete reproductive barrier between the species and connectivity between the watersheds. Additionally, fish were identified in the Itata northern reaches carrying mtDNA haplotypes sufficiently distinct from those of P. gillissi and P. irwini to suggest the existence of higher mtDNA diversity within P. gillissi than previously recognized. Finally, there was limited support for taxonomical classification based on morphological and meristic traits in this region.

     

Hydrological connectivity drives longitudinal movement of endangered endemic Chilean darter Percilia irwini (Eigenmann, 1927)

Movement is a fundamental aspect of fish ecology, and it therefore represents an important trait to monitor for the management and conservation of fish populations. This is especially true for small benthic fish, as they often inhabit part of the catchment where their movement may be restricted by alterations to river connectivity due to human activity. Still, the movement of these small benthic fish remains poorly understood, partly because of their small size and their cryptic nature. This applies to Percilia irwini, an endangered small darter native to the south-central region of Chile. Its habitat has been affected by the presence of large hydroelectric dams and is currently threatened by the construction of several others. In this study, the authors investigated movement patterns of P. irwini from populations inhabiting different parts of the Biobío catchment, with different levels of connectivity due to natural and/or human-induced features. The authors combined chronological clustering with random forest classification to reconstruct lifelong movements from multi-elemental otolith microchemistry transects. The majority of the movements detected occurred in an undisturbed part of the catchment. These were directional upstream movements occurring between capture sites from the lower and the middle reaches of the river, representing a distance of nearly 30 km, a distance much larger than previously thought. Nonetheless, in the part of the catchment where connectivity was affected by human activity, no such movements were identified. This study shows that connectivity alteration could impede naturally occurring movement and further threaten the resilience of populations of P. irwini. Furthermore, the results presented are used to discuss advantages and disadvantages of microchemistry analysis for studying movement of small benthic fish.     

The Potential Impact of Pre-Exposure Prophylaxis for HIV Prevention among Men Who Have Sex with Men and Transwomen in Lima, Peru: A Mathematical Modelling Study

Background

HIV pre-exposure prophylaxis (PrEP), the use of antiretroviral drugs by uninfected individuals to prevent HIV infection, has demonstrated effectiveness in preventing acquisition in a high-risk population of men who have sex with men (MSM). Consequently, there is a need to understand if and how PrEP can be used cost-effectively to prevent HIV infection in such populations.

Methods and Findings

We developed a mathematical model representing the HIV epidemic among MSM and transwomen (male-to-female transgender individuals) in Lima, Peru, as a test case. PrEP effectiveness in the model is assumed to result from the combination of a “conditional efficacy” parameter and an adherence parameter. Annual operating costs from a health provider perspective were based on the US Centers for Disease Control and Prevention interim guidelines for PrEP use. The model was used to investigate the population-level impact, cost, and cost-effectiveness of PrEP under a range of implementation scenarios. The epidemiological impact of PrEP is largely driven by programme characteristics. For a modest PrEP coverage of 5%, over 8% of infections could be averted in a programme prioritising those at higher risk and attaining the adherence levels of the Pre-Exposure Prophylaxis Initiative study. Across all scenarios, the highest estimated cost per disability-adjusted life year averted (uniform strategy for a coverage level of 20%, US$1,036–US$4,254) is below the World Health Organization recommended threshold for cost-effective interventions, while only certain optimistic scenarios (low coverage of 5% and some or high prioritisation) are likely to be cost-effective using the World Bank threshold. The impact of PrEP is reduced if those on PrEP decrease condom use, but only extreme behaviour changes among non-adherers (over 80% reduction in condom use) and a low PrEP conditional efficacy (40%) would adversely impact the epidemic. However, PrEP will not arrest HIV transmission in isolation because of its incomplete effectiveness and dependence on adherence, and because the high cost of programmes limits the coverage levels that could potentially be attained.

Conclusions

A strategic PrEP intervention could be a cost-effective addition to existing HIV prevention strategies for MSM populations. However, despite being cost-effective, a substantial expenditure would be required to generate significant reductions in incidence. Please see later in the article for the Editors'' Summary     

Estimating the Basic Reproductive Number (R0) for African Swine Fever Virus (ASFV) Transmission between Pig Herds in Uganda

African swine fever (ASF) is a highly contagious, lethal and economically devastating haemorrhagic disease of domestic pigs. Insights into the dynamics and scale of virus transmission can be obtained from estimates of the basic reproduction number (R₀). We estimate R₀ for ASF virus in small holder, free-range pig production system in Gulu, Uganda. The estimation was based on data collected from outbreaks that affected 43 villages (out of the 289 villages with an overall pig population of 26,570) between April 2010 and November 2011. A total of 211 outbreaks met the criteria for inclusion in the study. Three methods were used, specifically; (i) GIS- based identification of the nearest infectious neighbour based on the Euclidean distance between outbreaks, (ii) epidemic doubling time, and (iii) a compartmental susceptible-infectious (SI) model. For implementation of the SI model, three approaches were used namely; curve fitting (CF), a linear regression model (LRM) and the SI/N proportion. The R₀ estimates from the nearest infectious neighbour and epidemic doubling time methods were 3.24 and 1.63 respectively. Estimates from the SI-based method were 1.58 for the CF approach, 1.90 for the LRM, and 1.77 for the SI/N proportion. Since all these values were above one, they predict the observed persistence of the virus in the population. We hypothesize that the observed variation in the estimates is a consequence of the data used. Higher resolution and temporally better defined data would likely reduce this variation. This is the first estimate of R₀ for ASFV in a free range smallholder pig keeping system in sub-Saharan Africa and highlights the requirement for more efficient application of available disease control measures.     

The Cost and Impact of Scaling Up Pre-exposure Prophylaxis for HIV Prevention: A Systematic Review of Cost-Effectiveness Modelling Studies

Background

Cost-effectiveness studies inform resource allocation, strategy, and policy development. However, due to their complexity, dependence on assumptions made, and inherent uncertainty, synthesising, and generalising the results can be difficult. We assess cost-effectiveness models evaluating expected health gains and costs of HIV pre-exposure prophylaxis (PrEP) interventions.

Methods and Findings

We conducted a systematic review comparing epidemiological and economic assumptions of cost-effectiveness studies using various modelling approaches. The following databases were searched (until January 2013): PubMed/Medline, ISI Web of Knowledge, Centre for Reviews and Dissemination databases, EconLIT, and region-specific databases. We included modelling studies reporting both cost and expected impact of a PrEP roll-out. We explored five issues: prioritisation strategies, adherence, behaviour change, toxicity, and resistance. Of 961 studies retrieved, 13 were included. Studies modelled populations (heterosexual couples, men who have sex with men, people who inject drugs) in generalised and concentrated epidemics from Southern Africa (including South Africa), Ukraine, USA, and Peru. PrEP was found to have the potential to be a cost-effective addition to HIV prevention programmes in specific settings. The extent of the impact of PrEP depended upon assumptions made concerning cost, epidemic context, programme coverage, prioritisation strategies, and individual-level adherence. Delivery of PrEP to key populations at highest risk of HIV exposure appears the most cost-effective strategy. Limitations of this review include the partial geographical coverage, our inability to perform a meta-analysis, and the paucity of information available exploring trade-offs between early treatment and PrEP.

Conclusions

Our review identifies the main considerations to address in assessing cost-effectiveness analyses of a PrEP intervention—cost, epidemic context, individual adherence level, PrEP programme coverage, and prioritisation strategy. Cost-effectiveness studies indicating where resources can be applied for greatest impact are essential to guide resource allocation decisions; however, the results of such analyses must be considered within the context of the underlying assumptions made. Please see later in the article for the Editors'' Summary     

Diterpenoids from Haplopappus rigidus

Fractionation of the aerial parts of Haplopappus rigidus Phil., directed by the brine shrimp lethality test (BST), has led to the isolation of two new diterpenoids, rigidusol and deacetylrigidusol. Their structures were established as 13-hydroxy-18-acetoxy-cis-cleroda-3,14-diene (8betaH, 10betaH, 19beta, 20alpha form) and 13,18-dihydroxy-cis-cleroda-3,14-diene (8betaH, 10betaH, 19beta, 20alpha form), respectively. Rigidusol exhibit moderate cytotoxic activity against human breast adenocarcinoma cell line MCF-7. Their structures were established by spectral data, in particular using 2D NMR spectroscopy (DEPT, DQF-COSY, HMQC and HMBC).     

East African pigs have a complex Indian,Far Eastern and Western ancestry

In this study, we have characterized the mitochondrial diversity of 81 swine from Uganda. Median‐joining network analysis of D‐loop sequences from these individuals and others characterized in previous studies allowed us to determine that Ugandan pigs cluster with populations from the West (Europe/North Africa), Far East and India. In addition, partial sequencing of the Y‐chromosome UTY locus in 18 Ugandan domestic pigs revealed the segregation of a single HY1 lineage that has a cosmopolitan distribution. A Western and Far Eastern ancestry for East African pigs had been already reported, but this is the first study demonstrating an additional contribution from the Indian porcine gene pool. This result is consistent with the high frequency of zebuine alleles in cattle from East Africa. The geographic coordinates of East Africa, at the crossroads of many trading routes that, through the ages, linked Europe, Africa and Asia, might explain the rich and complex genetic heritage of livestock native to this area.     

The splice variant of the V2 vasopressin receptor adopts alternative topologies

The V2 receptor gene encodes two receptor variants by alternative splicing, the canonical V2 receptor (V2a receptor) and V2b. The V2b variant has an amino acid sequence identical to that of the V2a receptor up to the sixth transmembrane domain, but the V2b sequences corresponding to the putative seventh transmembrane domain and the carboxyl terminus are different from those of the V2a receptor. Here we investigate the topology and subcellular distribution of the V2b variant. We found that, in contrast to the V2a receptor, the V2b adopted two topologies: one with six transmembrane segments with the C-terminus on the extracellular side of the membrane and another with seven transmembrane segments with the C-terminus on the intracellular side, similar to typical G-protein-coupled receptors. Furthermore, we observed that both topological isoforms oligomerized with the V2a canonical receptor. Unlike the V2a receptor, V2b did not move to the plasma membrane, but it is retained in the ER--Golgi compartments. These findings indicate that the C-terminal sequence beyond the sixth transmembrane of the V2a is required for the stabilization of the seven-transmembrane topology of the receptor and is also essential for the trafficking of the receptor to the plasma membrane.     

Effects of dehulling,steam-cooking and microwave-irradiation on digestive value of white lupin (Lupinus albus) seed meal for rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

A digestibility trial was conducted to assess the effect of dehulling, steam-cooking and microwave-irradiation on the apparent digestibility of nutrients in white lupin (Lupinus albus) seed meal when fed to rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). Six ingredients, whole lupin seed meal (LSM), dehulled LSM, dehulled LSM steam-cooked for 15 or 45 min (SC15 and SC45, respectively) and LSM microwave-irradiated at 375 or 750 W (MW375 and MW750, respectively), were evaluated for digestibility of dry matter, crude protein (CP), lipids, nitrogen-free extractives (NFE) and gross energy (GE). The diet-substitution approach was used (70% reference diet + 30% test ingredient). Faeces from each tank were collected using a settlement column. Dehulled LSM showed higher levels of proximate components (except for NFE and crude fibre), GE and phosphorus in comparison to whole LSM. Furthermore, SC15, SC45, MW375 and MW750 showed slight variations of chemical composition in comparison to dehulled LSM. Results from the digestibility trial indicated that dehulled LSM, SC15, SC45 and MW375 are suitable processing methods for the improvement of nutrients’ apparent digestibility coefficient (ADC) in whole LSM. MW750 showed a lower ADC of nutrients (except for CP and lipids for rainbow trout) in comparison with MW350 for rainbow trout and Atlantic salmon, suggesting a heat damage of the ingredient when microwave-irradiation exceeded 350 W.     

An Investigation of Prebiotic Purine Synthesis from the Hydrolysis of HCN Polymers

The polymerization of concentrated NH₄CN solutions has been studied at various temperatures and ammonia concentrations. The products of the oligomerization of ammonium cyanide include adenine and guanine, as well as trace amounts of 2,6-diaminopurine. Our results indicate that the adenine yield is not strongly dependent on temperature. Guanine is produced in lower yield. The original studies by Oró and Kimball (1961) showed that the 6 N HCl hydrolysis of the NH₄CN polymerization supernatant greatly increased the adenine yield. However, this hydrolysis also decomposes adenine and other purines. Therefore, we have measured the yields from an NH₄CN polymerization as a function of hydrolysis time, and found that shorter hydrolytic periods give higher yields of adenine.We have also investigated the hydrolysis of the supernatant at pH 8, which is a more reasonable model of primitive oceanic conditions, and found that the adenine yield is comparable to that obtained with acid hydrolysis (approximately 0.1%). The yield of adenine does not decline at longer hydrolysis times because of the greater stability of adenine at pH 8. The insoluble black polymer formed from NH₄CN has been analyzed by both acid and neutral hydrolysis. In both cases adenine yields of approximately 0.05% were obtained. This suggests that the polymer may have been as important a prebiotic source of purines as the usually analyzed supernatant.