scholarly journals Microbial grazers may aid in controlling infections caused by aquatic zoosporic fungi

2020 ◽  
Author(s):  
Hazel N. Farthing ◽  
Jiamei Jiang ◽  
Alexandra J. Henwood ◽  
Andy Fenton ◽  
Trent Garner ◽  
...  
Keyword(s):  
Maximum Rate ◽  
Batrachochytrium Dendrobatidis ◽  
Tetrahymena Pyriformis ◽  
Disease Dynamics ◽  
Free Living ◽  
Half Saturation Constant ◽  
Dispersal Stage ◽  
Zoosporic Fungi ◽  
Eukaryotic Microbes ◽  
Dynamics Simulations

AbstractFree-living eukaryotic microbes may reduce animal diseases. We evaluated the dynamics by which micrograzers (primarily protozoa) apply top-down control on the chytrid Batrachochytrium dendrobatidis (Bd) a devastating, panzootic pathogen of amphibians. Although micrograzers consumed zoospores (∼3 µm), the dispersal stage of chytrids, not all species grew monoxenically on zoospores. However, the ubiquitous ciliate Tetrahymena pyriformis, which likely co-occurs with Bd, grew at near its maximum rate (r = 1.7 d-1). A functional response (ingestion vs. prey abundance) for T. pyriformis, measured using spore-surrogates (microspheres) revealed maximum ingestion (Imax) of 1.63 × 103 zoospores d-1, with a half saturation constant (k) of 5.75 × 103 zoospores ml-1. Using these growth and grazing data we developed and assessed a population model that incorporated chytrid-host and micrograzer dynamics. Simulations using our data and realistic parameters obtained from the literature suggested that micrograzers could control Bd and potentially prevent chytridiomycosis (defined as 104 sporangia host-1). However, simulated inferior micrograzers (0.7 x Imax and 1.5 x k) did not prevent chytridiomycosis, although they ultimately reduced pathogen abundance to below levels resulting in disease. These findings indicate how micrograzer responses can be applied when modelling disease dynamics for Bd and other zoosporic fungi.

scholarly journals Microbial Grazers May Aid in Controlling Infections Caused by the Aquatic Zoosporic Fungus Batrachochytrium dendrobatidis

2021 ◽  
Vol 11 ◽  
Author(s):  
Hazel N. Farthing ◽  
Jiamei Jiang ◽  
Alexandra J. Henwood ◽  
Andy Fenton ◽  
Trent W. J. Garner ◽  
...  
Keyword(s):  
Population Model ◽  
Maximum Rate ◽  
Batrachochytrium Dendrobatidis ◽  
Tetrahymena Pyriformis ◽  
Disease Dynamics ◽  
Free Living ◽  
Half Saturation Constant ◽  
Dispersal Stage ◽  
Eukaryotic Microbes ◽  
Dynamics Simulations

Free-living eukaryotic microbes may reduce animal diseases. We evaluated the dynamics by which micrograzers (primarily protozoa) apply top-down control on the chytrid Batrachochytrium dendrobatidis (Bd) a devastating, panzootic pathogen of amphibians. Although micrograzers consumed zoospores (∼3 μm), the dispersal stage of chytrids, not all species grew monoxenically on zoospores. However, the ubiquitous ciliate Tetrahymena pyriformis, which likely co-occurs with Bd, grew at near its maximum rate (r = 1.7 d–1). A functional response (ingestion vs. prey abundance) for T. pyriformis, measured using spore-surrogates (microspheres) revealed maximum ingestion (Imax) of 1.63 × 103 zoospores d–1, with a half saturation constant (k) of 5.75 × 103 zoospores ml–1. Using these growth and grazing data we developed and assessed a population model that incorporated chytrid-host and micrograzer dynamics. Simulations using our data and realistic parameters obtained from the literature suggested that micrograzers could control Bd and potentially prevent chytridiomycosis (defined as 104 sporangia host–1). However, simulated inferior micrograzers (0.7 × Imax and 1.5 × k) did not prevent chytridiomycosis, although they ultimately reduced pathogen abundance to below levels resulting in disease. These findings indicate how micrograzer responses can be applied when modeling disease dynamics for Bd and other zoosporic fungi.

scholarly journals Fluorescent Acid-Fast Microscopy for Measuring Phagocytosis of Mycobacterium avium,Mycobacterium intracellulare, and Mycobacterium scrofulaceum by Tetrahymena pyriformis and Their Intracellular Growth

2001 ◽  
Vol 67 (10) ◽  
pp. 4432-4439 ◽  
Author(s):  
Eileen D. Strahl ◽  
Glenda E. Gillaspy ◽  
Joseph O. Falkinham
Keyword(s):  
Linear Relationship ◽  
Mycobacterium Avium ◽  
Tetrahymena Pyriformis ◽  
Mycobacterial Infection ◽  
Fresh Medium ◽  
Intracellular Growth ◽  
Free Living ◽  
Mycobacterium Intracellulare ◽  
Natural Hosts

ABSTRACT Fluorescent acid-fast microscopy (FAM) was used to enumerate intracellular Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceumin the ciliated phagocytic protozoan Tetrahymena pyriformis. There was a linear relationship between FAM and colony counts of M. avium cells both from cultures and within protozoa. The Ziehl-Neelsen acid-fast stain could not be used to enumerate intracellular mycobacteria because uninfected protozoa contained acid-fast, bacterium-like particles. Starved, 7-day-old cultures of T. pyriformis transferred into fresh medium readily phagocytized M. avium, M. intracellulare, and M. scrofulaceum. Phagocytosis was rapid and reached a maximum in 30 min. M. avium, M. intracellulare, and M. scrofulaceum grew within T. pyriformis, increasing by factors of 4- to 40-fold after 5 days at 30°C. Intracellular M. avium numbers remained constant over a 25-day period of growth (by transfer) of T. pyriformis. Intracellular M. avium cells also survived protozoan encystment and germination. The growth and viability of T. pyriformis were not affected by mycobacterial infection. The results suggest that free-living phagocytic protozoa may be natural hosts and reservoirs for M. avium, M. intracellulare, and M. scrofulaceum.

scholarly journals First detection of the amphibian chytrid fungus (Batrachochytridium dendrobatidis) in free- living anuran populations in Greece

2018 ◽  
Vol 67 (4) ◽  
pp. 253
Author(s):  
P. N. AZMANIS ◽  
I. STRACHINIS ◽  
P. LYMBERAKIS ◽  
R. E. MARSCHANG
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Batrachochytrium Dendrobatidis ◽  
Chytrid Fungus ◽  
Free Living ◽  
Bufo Viridis ◽  
First Report ◽  
Water Frogs ◽  
Preliminary Study ◽  
Amphibian Chytrid Fungus

The amphibian chytrid fungus (Batrachochytrium dendrobatidis) is a widespread, cosmopolitan pathogen largely affecting free-living amphibian populations. So far there are no published studies for the presence of B. dendrobatidis in Greece. In this preliminary study we sampled 59 metamorphosed anurans from four Greek wetlands. Five samples were positive for the fungus by real-time PCR. B. dendrobatidis was detected in three species (Bufo viridis, Pelophylax epeiroticus, Pelophylax ridibundus) but not in endangered endemic Karpathos water frogs (Pelophylax cerigensis). This is the first report of the amphibian chytrid fungus (Batrachochytrium dendrobatidis) in free-living anuran populations from Greece.

scholarly journals Variation in SARS-CoV-2 free-living survival and environmental transmission can modulate the intensity of COVID-19 outbreaks

2020 ◽  
Author(s):  
C. Brandon Ogbunugafor ◽  
Miles Miller-Dickson ◽  
Victor A. Meszaros ◽  
Lourdes M. Gomez ◽  
Anarina L. Murillo ◽  
...  
Keyword(s):  
Basic Reproductive Number ◽  
Reproductive Number ◽  
Disease Dynamics ◽  
Free Living ◽  
Environmental Transmission ◽  
Country Level ◽  
History Of ◽  
Virus Survival ◽  
Case Data

ABSTRACTCOVID-19 has circled the globe, rapidly expanding into a pandemic within a matter of weeks. While early studies revealed important features of SARS-CoV-2 transmission, the role of variation in free-living virus survival in modulating the dynamics of outbreaks remains unclear and controversial. Using an empirically determined understanding of the natural history of SARS-CoV-2 infection and detailed, country-level case data, we elucidate how variation in free-living virus survival influences key features of COVID-19 epidemics. Our findings suggest that environmental transmission can have a subtle, yet significant influence on COVID-19’s basic reproductive number () and other key signatures of outbreak intensity. Summarizing, we propose that variation in environmental transmission may explain some observed differences in disease dynamics from setting to setting, and can inform public health interventions.

scholarly journals The epidemiological signature of pathogen populations that vary in the relationship between free-living survival and virulence

2020 ◽  
Author(s):  
Lourdes M. Gomez ◽  
Victor A Meszaros ◽  
Wendy C. Turner ◽  
C. Brandon Ogbunugafor
Keyword(s):  
Public Health ◽  
Disease Dynamics ◽  
Free Living ◽  
Evolutionary Changes ◽  
Evolution Of Virulence ◽  
Parasite Survival ◽  
Transmission Studies ◽  
Pathogen Populations ◽  
Host Parasite ◽  
The Relationship

ABSTRACTThe relationship between parasite virulence and transmission is a pillar of evolutionary theory that has specific implications for public health. Part of this canon involves the idea that virulence and free-living survival (a key component of transmission) may have different relationships in different host-parasite systems. Most examinations of the evolution of virulence-transmission relationships—theoretical or empirical in nature—tend to focus on the evolution of virulence, with transmission a secondary consideration. And even within transmission studies, the focus on free-living survival is a smaller subset, though recent studies have examined its importance in the ecology of infectious diseases. Few studies have examined the epidemic-scale consequences of variation in survival across different virulence-survival relationships. In this study, we utilize a mathematical model motivated by aspects of SARS-CoV-2 natural history to investigate how evolutionary changes in survival may influence several aspects of disease dynamics at the epidemiological scale. Across virulence-survival relationships (where these traits are positively or negatively correlated), we found that small changes (5% above and below the nominal value) in survival can have a meaningful effect on certain outbreak features, including the R0, and the size of the infectious peak in the population. These results highlight the importance of properly understanding the mechanistic relationship between virulence and parasite survival, as evolution of increased survival across different relationships with virulence will have considerably different epidemiological signatures.

scholarly journals Social Behavior, Community Composition, Pathogen Strain, and Host Symbionts Influence Fungal Disease Dynamics in Salamanders

2021 ◽  
Vol 8 ◽  
Author(s):  
Mae Cowgill ◽  
Andrew G. Zink ◽  
Wesley Sparagon ◽  
Tiffany A. Yap ◽  
Hasan Sulaeman ◽  
...  
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Linear Models ◽  
Abiotic Factors ◽  
Historical Context ◽  
Maximum Temperature ◽  
Disease Dynamics ◽  
Amphibian Species ◽  
Host Interactions ◽  
Pathogen Invasion ◽  
Skin Bacteria

The emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), which can cause a fatal disease called chytridiomycosis, is implicated in the collapse of hundreds of host amphibian species. We describe chytridiomycosis dynamics in two co-occurring terrestrial salamander species, the Santa Lucia Mountains slender salamander, Batrachoseps luciae, and the arboreal salamander, Aneides lugubris. We (1) conduct a retrospective Bd-infection survey of specimens collected over the last century, (2) estimate present-day Bd infections in wild populations, (3) use generalized linear models (GLM) to identify biotic and abiotic correlates of infection risk, (4) investigate susceptibility of hosts exposed to Bd in laboratory trials, and (5) examine the ability of host skin bacteria to inhibit Bd in culture. Our historical survey of 2,866 specimens revealed that for most of the early 20th century (~1920–1969), Bd was not detected in either species. By the 1990s the proportion of infected specimens was 29 and 17% (B. luciae and A. lugubris, respectively), and in the 2010s it was 10 and 17%. This was similar to the number of infected samples from contemporary populations (2014–2015) at 10 and 18%. We found that both hosts experience signs of chytridiomycosis and suffered high Bd-caused mortality (88 and 71% for B. luciae and A. lugubris, respectively). Our GLM revealed that Bd-infection probability was positively correlated with intraspecific group size and proximity to heterospecifics but not to abiotic factors such as precipitation, minimum temperature, maximum temperature, mean temperature, and elevation, or to the size of the hosts. Finally, we found that both host species contain symbiotic skin-bacteria that inhibit growth of Bd in laboratory trials. Our results provide new evidence consistent with other studies showing a relatively recent Bd invasion of amphibian host populations in western North America and suggest that the spread of the pathogen may be enabled both through conspecific and heterospecific host interactions. Our results suggest that wildlife disease studies should assess host-pathogen dynamics that consider the interactions and effects of multiple hosts, as well as the historical context of pathogen invasion, establishment, and epizootic to enzootic transitions to better understand and predict disease dynamics.

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