Efficacy of chemical disinfectants for the containment of the salamander chytrid fungus Batrachochytrium salamandrivorans

The recently emerged chytrid fungus Batrachochytrium salamandrivorans (Bsal) causes European salamander declines. Proper hygiene protocols including disinfection procedures are crucial to prevent disease transmission. Here, the efficacy of chemical disinfectants in killing Bsal was evaluated. At all tested conditions, Biocidal (R), Chloramine-T (R), Dettol medical (R), Disolol (R), ethanol, F10 (R), Hibiscrub (R), potassium permanganate, Safe4 (R), sodium hypochlorite, and Virkon S (R), were effective at killing Bsal. Concentrations of 5% sodium chloride or lower, 0.01% peracetic acid and 0.001-1% copper sulphate were inactive against Bsal. None of the conditions tested for hydrogen peroxide affected Bsal viability, while it did kill Batrachochytrium dendrobatidis (Bd). For Bsal, enzymatic breakdown of hydrogen peroxide by catalases and specific morphological features (clustering of sporangia, development of new sporangia within the original sporangium), were identified as fungal factors altering susceptibility to several of the disinfectants tested. Based on the in vitro results we recommend 1% Virkon S (R), 4% sodium hypochlorite and 70% ethanol for disinfecting equipment in the field, lab or captive setting, with a minimal contact time of 5 minutes for 1% Virkon S (R) and 1 minute for the latter disinfectants. These conditions not only efficiently target Bsal, but also Bd and Ranavirus

Amphibian chytridiomycosis : a review with focus on fungus-host interactions

Amphibian declines and extinctions are emblematic for the current sixth mass extinction event. Infectious drivers of these declines include the recently emerged fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans (Chytridiomycota). The skin disease caused by these fungi is named chytridiomycosis and affects the vital function of amphibian skin. Not all amphibians respond equally to infection and host responses might range from resistant, over tolerant to susceptible. The clinical outcome of infection is highly dependent on the amphibian host, the fungal virulence and environmental determinants. B. dendrobatidis infects the skin of a large range of anurans, urodeles and caecilians, whereas to date the host range of B. salamandrivorans seems limited to urodeles. So far, the epidemic of B. dendrobatidis is mainly limited to Australian, neotropical, South European and West American amphibians, while for B. salamandrivorans it is limited to European salamanders. Other striking differences between both fungi include gross pathology and thermal preferences. With this review we aim to provide the reader with a state-of-the art of host-pathogen interactions for both fungi, in which new data pertaining to the interaction of B. dendrobatidis and B. salamandrivorans with the host's skin are integrated. Furthermore, we pinpoint areas in which more detailed studies are necessary or which have not received the attention they merit

Chytridiomycosis related mortality in a midwife toad (Alytes obstetricans) in Belgium

Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, contributes to amphibian declines worldwide. Recently, the fungus has shown to be widely distributed in Belgium and the Netherlands, although no clinical cases of the disease have been diagnosed yet. This case report describes the first case of mortality due to chytridiomycosis in Belgium in a wild population of midwife toads (Alytes obstetricans). The presence of clinical chytridiomycosis, combined with the relatively high prevalence of the fungus in Belgium, emphasizes the urgent need for a thorough study on the impact of infection on the native amphibian populations in Belgium

In vitro modeling of Batrachochytrium dendrobatidis infection of the amphibian skin

The largest current disease-induced loss of vertebrate biodiversity is due to chytridiomycosis and despite the increasing understanding of the pathogenesis, knowledge unravelling the early host-pathogen interactions remains limited. Batrachochytrium dendrobatidis (Bd) zoospores attach to and invade the amphibian epidermis, with subsequent invasive growth in the host skin. Availability of an in vitro assay would facilitate in depth study of this interaction while reducing the number of experimental animals needed. We describe a fluorescent cell-based in vitro infection model that reproduces host-Bd interactions. Using primary keratinocytes from Litoria caerulea and the epithelial cell line A6 from Xenopus laevis, we reproduced different stages of host cell infection and intracellular growth of Bd, resulting in host cell death, a key event in chytridiomycosis. The presented in vitro models may facilitate future mechanistic studies of host susceptibility and pathogen virulence

Instant killing of pathogenic chytrid fungi by disposable nitrile gloves prevents disease transmission between amphibians

To prevent transmission of the pathogenic chytrid fungi Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), hygiene protocols prescribe the single use of disposable gloves for handling amphibians. We discovered that rinse water from nitrile gloves instantly kills 99% of Bd and Bsal zoospores. Transmission experiments using midwife toads (Alytes obstetricans) and Bd, and Alpine newts (Ichthyosaura alpestris) and Bsal, show that the use of the same pair of gloves for 2 subsequent individuals does not result in significant transmission of any chytrid fungus. In contrast, handling infected amphibians bare-handed caused transmission of Bsal in 4 out of 10 replicates, but did not result in transmission of Bd. Based on the manufacturer’s information, high resolution mass spectrometry (HRMS) and colorimetric tests, calcium lactate and calcium nitrate were identified as compounds with antifungal activity against both Bd and Bsal. These findings corroborate the importance of wearing gloves as an important sanitary measure in amphibian disease prevention. If the highly recommended single use of gloves is not possible, handling multiple post-metamorphic amphibians with the same pair of nitrile gloves should still be preferred above bare-handed manipulation

Analyzing hierarchical multi-view MRI data with StaPLR: An application to Alzheimer's disease classification

Multi-view data refers to a setting where features are divided into feature sets, for example because they correspond to different sources. Stacked penalized logistic regression (StaPLR) is a recently introduced method that can be used for classification and automatically selecting the views that are most important for prediction. We introduce an extension of this method to a setting where the data has a hierarchical multi-view structure. We also introduce a new view importance measure for StaPLR, which allows us to compare the importance of views at any level of the hierarchy. We apply our extended StaPLR algorithm to Alzheimer's disease classification where different MRI measures have been calculated from three scan types: structural MRI, diffusion-weighted MRI, and resting-state fMRI. StaPLR can identify which scan types and which derived MRI measures are most important for classification, and it outperforms elastic net regression in classification performance.Comment: 36 pages, 9 figures. Accepted manuscrip

Inhibin reduces spermatogonial numbers in testes of adult mice and chinese hamsters

Bovine follicular fluid (bFF) injected ip in mice during 2 days (65,000 U inhibin/day, 1 U inhibin the activity in 1 /μg bFF protein) caused a significant decrease in the numbers of A4, intermediate (In), and B spermatogonia to 91%,74%, and 67% of the control values, respectively. The numbers of undifferentiated spermatogonia remained unchanged. These injections suppressed peripheral FSH levels to 6% of the control values, suggesting that FSH might be the modulator of the effects on spermatogenesis. However, in the Chinese hamster, intratesticular injections of bFF during 4 days (6500 U inhibin/day into one testis) also caused a significant decrease in the numbers of A3, In, B1, and B2 spermatogonia to 86%, 61%, 55%, and 94% of the control values, respectively. Similarly, treatment with a partially purified inhibin preparation from rat Sertoli cell-conditioned medium (rSCCM) during 4 days (Mono Q fraction; 1512 U inhibin/day; 37.8 μg protein) caused a significant decrease in the numbers of A3, In, B1, and B2 spermatogonia to 90%, 87%, 66%, and 93% of the control values, respectively. Treatment with a highly purified inhibin preparation from rSCCM during 4 days (30K inhibin; 750 U inhibin/day; 100 ng protein) significantly decreased the numbers of In and B1 spermatogonia to, respectively, 87% and 91% of the control values. These effects were limited to the testis into which the material was injected; the contralateral testis or testes injected with control fluid always showed normal numbers of spermatogonia. This implies that the effects on the seminiferous epithelium are not FSH mediated. Intratesticular injections of bFF or pure inhibin did not affect the number of undifferentiated spermatogonia. However, the Mono Q fraction caused a significant increase in the numbers of undifferentiated spermatogonia in stages IV-VII of the cycle, suggesting the presence of a mitogenic factor for undifferentiated spermatogonia in rSCCM which is not present or is counteracted in bFF. The results suggest that inhibin may have a role in the regulation of spermatogonial development in the adult animal

Voriconazole, a safe alternative for treating infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii in bearded dragons (Pogona vitticeps)

Dermal and systemic infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii (CANV) are highly prevalent in reptiles and may result in severe disease and high mortality. Due to the high incidence of therapeutic failures, optimizing treatment is required. We first determined in this study the minimal inhibitory concentrations (MIC) of itraconazole, voriconazole, amphotericin B and terbinafine against 32 CANV isolates. For voriconazole, amphotericin B and terbinafine a monomodal MIC distribution was seen, whereas a bimodal MIC distribution was present for itraconazole, indicating acquired resistance in one isolate. Fourteen naturally-infected bearded dragons (Pogona vitticeps), from the same owner, were treated orally with either itraconazole (5 mg/kg q24h) or voriconazole (10 mg/kg q24h). The clinical condition, drug plasma concentrations and the presence of CANV in skin samples were followed. The animals were treated until complete clearance of the fungus. The plasma concentrations of voriconazole and itraconazole exceeded the minimal inhibitory concentrations of the CANV isolates. Elimination of CANV was achieved on average after 27 and 47 days of treatment with itraconazole and voriconazole, respectively. Whereas only 2 out of 7 survived after itraconazole treatment, only a single animal died in the voriconazole treated group. In conclusion, based on a limited number of animals, voriconazole applied at a regimen of 10 mg/kg bodyweight (BW) q24h seems to be a safe and effective antimycotic drug to eliminate CANV infections in bearded dragons

Late Holocene current patterns in the northern Patagonian fjords recorded by sediment drifts in Aysén Fjord

Present-day circulation patterns in the southeastern Pacific Ocean are driven by the Antarctic Circumpolar Current, directing subantarctic surface water into the Patagonian fjords since at least the early Holocene. In this way, bottom current patterns in the area are regulated by the regional climate, although the complex bathymetry of the fjords has a significant impact as well. To understand the potential interplay of climate, seafloor topography and circulation patterns, we study the sedimentary infill of Aysén Fjord (~45°S) and reveal the first active sediment drifts in the region. These allow constraining the present-day circulation patterns in northern Patagonia and show an incoming (southward) as well as returning (northward) flow direction. While the general sedimentary evolution of the fjord (and thus also the sediment drifts) is climate-driven (i.e., it reflects variability in southern westerly wind strength), the onset of drift formation at ~3.7 ka does not seem to have originated from an abrupt change in regional climate. Instead, we propose that a megathrust earthquake described in paleoseismic records in the area could have resulted in subsidence of one (or more) of the many bathymetric highs in the Patagonian fjords, thus contributing to enhanced spilling of subantarctic water into the fjord. This study underscores the importance of multidisciplinary research to understand past and present bottom current circulation patterns and disentangle different possible feedback mechanisms

Genome-wide association studies in economics and entrepreneurship research: promises and limitations

The recently developed genome-wide association study (GWAS) design enables the identification of genes specifically associated with economic outcomes such as occupational and other choices. This is a promising new approach for economics research which we aim to apply to the choice for entrepreneurship. However, due to multiple testing issues, very large sample sizes are needed to differentiate between true and false positives. For a GWAS on entrepreneurship, we expect that a sample size of at least 30,000 observations is required