scholarly journals Disruption of Metapopulation Structure Reduces Tasmanian Devil Facial Tumour Disease Spread at the Expense of Abundance and Genetic Diversity

Pathogens ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1592
Author(s):  
Rowan Durrant ◽  
Rodrigo Hamede ◽  
Konstans Wells ◽  
Miguel Lurgi
Keyword(s):  
Genetic Diversity ◽  
Disease Transmission ◽  
Transmission Rate ◽  
Extinction Risk ◽  
Disease Prevalence ◽  
Disease Spread ◽  
Tasmanian Devil ◽  
Local Populations ◽  
Metapopulation Structure ◽  
Devil Facial Tumour Disease

Metapopulation structure plays a fundamental role in the persistence of wildlife populations. It can also drive the spread of infectious diseases and transmissible cancers such as the Tasmanian devil facial tumour disease (DFTD). While disrupting this structure can reduce disease spread, it can also impair host resilience by disrupting gene flow and colonisation dynamics. Using an individual-based metapopulation model we investigated the synergistic effects of host dispersal, disease transmission rate and inter-individual contact distance for transmission, on the spread and persistence of DFTD from local to regional scales. Disease spread, and the ensuing population declines, are synergistically determined by individuals’ dispersal, disease transmission rate and within-population mixing. Transmission rates can be magnified by high dispersal and inter-individual transmission distance. The isolation of local populations effectively reduced metapopulation-level disease prevalence but caused severe declines in metapopulation size and genetic diversity. The relative position of managed (i.e., isolated) local populations had a significant effect on disease prevalence, highlighting the importance of considering metapopulation structure when implementing metapopulation-scale disease control measures. Our findings suggest that population isolation is not an ideal management method for preventing disease spread in species inhabiting already fragmented landscapes, where genetic diversity and extinction risk are already a concern.

scholarly journals Disruption of metapopulation structure effectively reduces Tasmanian devil facial tumour disease spread at the expense of abundance and genetic diversity

2021 ◽  
Author(s):  
Rowan Durrant ◽  
Rodrigo Hamede ◽  
Konstans Wells ◽  
Miguel Lurgi
Keyword(s):  
Genetic Diversity ◽  
Disease Transmission ◽  
Transmission Rate ◽  
Disease Spread ◽  
Tasmanian Devil ◽  
Population Mixing ◽  
Metapopulation Structure ◽  
High Dispersal ◽  
Contact Distance ◽  
Devil Facial Tumour Disease

Metapopulation structure (i.e. the spatial arrangement of local populations and corridors between them) plays a fundamental role in the persistence of wildlife populations, but can also drive the spread of infectious diseases. While the disruption of metapopulation connectivity can reduce disease spread, it can also impair host resilience by disrupting gene flow and colonisation dynamics. Thus, a pressing challenge for many wildlife populations is to elucidate whether the benefits of disease management methods that reduce metapopulation connectivity outweigh the associated risks. Directly transmissible cancers are clonal malignant cell lines capable to spread through host populations without immune recognition, when susceptible and infected hosts become in close contact. Using an individual-based metapopulation model we investigate the effects of the interplay between host dispersal, disease transmission rate and inter-individual contact distance for transmission (determining within-population mixing) on the spread and persistence of a transmissible cancer, Tasmanian devil facial tumour disease (DFTD), from local to regional scales. Further, we explore population isolation scenarios to devise management strategies to mitigate disease spread. Disease spread, and the ensuing population declines, are synergistically determined by individuals' dispersal, disease transmission rate and within-population mixing. Low to intermediate transmission rates can be magnified by high dispersal and inter-individual transmission distance. Once disease transmission rate is high, dispersal and inter-individual contact distance do not impact the outcome of the disease transmission dynamics. Isolation of local populations effectively reduced metapopulation-level disease prevalence but caused severe declines in metapopulation size and genetic diversity. The relative position of managed (i.e. isolated) populations within the metapopulation had a significant effect on disease prevalence, highlighting the importance of considering metapopulation structure when implementing metapopulation-scale disease control measures. Our findings suggests that population isolation is not an ideal management method for preventing disease spread in species inhabiting already fragmented landscapes, where genetic diversity and extinction risk are already a concern, such as the Tasmanian devil.

scholarly journals Rate of intersexual interactions affects injury likelihood in Tasmanian devil contact networks

2019 ◽  
Vol 30 (4) ◽  
pp. 1087-1095 ◽  
Author(s):  
David G Hamilton ◽  
Menna E Jones ◽  
Elissa Z Cameron ◽  
Hamish McCallum ◽  
Andrew Storfer ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Cancer Cell Line ◽  
Mate Guarding ◽  
Disease Spread ◽  
Tasmanian Devil ◽  
Mating Season ◽  
Wildlife Diseases ◽  
Individual Level ◽  
Contact Patterns ◽  
Bite Wounds

Abstract Identifying the types of contacts that result in disease transmission is important for accurately modeling and predicting transmission dynamics and disease spread in wild populations. We investigated contacts within a population of adult Tasmanian devils (Sarcophilus harrisii) over a 6-month period and tested whether individual-level contact patterns were correlated with accumulation of bite wounds. Bite wounds are important in the spread of devil facial tumor disease, a clonal cancer cell line transmitted through direct inoculation of tumor cells when susceptible and infected individuals bite each other. We used multimodel inference and network autocorrelation models to investigate the effects of individual-level contact patterns, identities of interacting partners, and position within the social network on the propensity to be involved in bite-inducing contacts. We found that males were more likely to receive potentially disease-transmitting bite wounds than females, particularly during the mating season when males spend extended periods mate-guarding females. The number of bite wounds individuals received during the mating season was unrelated to any of the network metrics examined. Our approach illustrates the necessity for understanding which contact types spread disease in different systems to assist the management of this and other infectious wildlife diseases.

scholarly journals No Place Like Home: Cross-National Data Analysis of the Efficacy of Social Distancing During the COVID-19 Pandemic (Preprint)

2020 ◽  
Author(s):  
Dursun Delen ◽  
Enes Eryarsoy ◽  
Behrooz Davazdahemami
Keyword(s):  
Disease Transmission ◽  
Transmission Rate ◽  
Disease Spread ◽  
Data Sets ◽  
Mobility Patterns ◽  
Social Distancing ◽  
Mobility Data ◽  
Simulation Based ◽  
Transactional Data ◽  
Cross National

BACKGROUND In the absence of a cure in the time of a pandemic, social distancing measures seem to be the most effective intervention to slow the spread of disease. Various simulation-based studies have been conducted to investigate the effectiveness of these measures. While those studies unanimously confirm the mitigating effect of social distancing on disease spread, the reported effectiveness varies from 10% to more than 90% reduction in the number of infections. This level of uncertainty is mostly due to the complex dynamics of epidemics and their time-variant parameters. However, real transactional data can reduce uncertainty and provide a less noisy picture of the effectiveness of social distancing. OBJECTIVE The aim of this paper was to integrate multiple transactional data sets (GPS mobility data from Google and Apple as well as disease statistics from the European Centre for Disease Prevention and Control) to study the role of social distancing policies in 26 countries and analyze the transmission rate of the coronavirus disease (COVID-19) pandemic over the course of 5 weeks. METHODS Relying on the susceptible-infected-recovered (SIR) model and official COVID-19 reports, we first calculated the weekly transmission rate (<i>β</i>) of COVID-19 in 26 countries for 5 consecutive weeks. Then, we integrated these data with the Google and Apple mobility data sets for the same time frame and used a machine learning approach to investigate the relationship between the mobility factors and <i>β</i> values. RESULTS Gradient boosted trees regression analysis showed that changes in mobility patterns resulting from social distancing policies explain approximately 47% of the variation in the disease transmission rates. CONCLUSIONS Consistent with simulation-based studies, real cross-national transactional data confirms the effectiveness of social distancing interventions in slowing the spread of COVID-19. In addition to providing less noisy and more generalizable support for the idea of social distancing, we provide specific insights for public health policy makers regarding locations that should be given higher priority for enforcing social distancing measures.

scholarly journals A Tasmanian devil breeding program to support wild recovery

2019 ◽  
Vol 31 (7) ◽  
pp. 1296 ◽  
Author(s):  
C. E. Grueber ◽  
E. Peel ◽  
B. Wright ◽  
C. J. Hogg ◽  
K. Belov
Keyword(s):  
Genetic Diversity ◽  
Reproductive Success ◽  
Genetic Research ◽  
Breeding Program ◽  
Natural Environments ◽  
Tasmanian Devil ◽  
Strategic Approach ◽  
Devil Facial Tumour Disease ◽  
Transmissible Cancer ◽  
In The Wild

Tasmanian devils are threatened in the wild by devil facial tumour disease: a transmissible cancer with a high fatality rate. In response, the Save the Tasmanian Devil Program (STDP) established an ‘insurance population’ to enable the preservation of genetic diversity and natural behaviours of devils. This breeding program includes a range of institutions and facilities, from zoo-based intensive enclosures to larger, more natural environments, and a strategic approach has been required to capture and maintain genetic diversity, natural behaviours and to ensure reproductive success. Laboratory-based research, particularly genetics, in tandem with adaptive management has helped the STDP reach its goals, and has directly contributed to the conservation of the species in the wild. Here we review this work and show that the Tasmanian devil breeding program is a powerful example of how genetic research can be used to understand and improve reproductive success in a threatened species.

scholarly journals Reducing the Extinction Risk of Populations Threatened by Infectious Diseases

Diversity ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 63
Author(s):  
Gael L. Glassock ◽  
Catherine E. Grueber ◽  
Katherine Belov ◽  
Carolyn J. Hogg
Keyword(s):  
Gene Flow ◽  
Infectious Diseases ◽  
Extinction Risk ◽  
Population Decline ◽  
Outbreeding Depression ◽  
Tasmanian Devil ◽  
Adaptive Potential ◽  
Genetic Management ◽  
Animal Populations ◽  
Devil Facial Tumour Disease

Extinction risk is increasing for a range of species due to a variety of threats, including disease. Emerging infectious diseases can cause severe declines in wild animal populations, increasing population fragmentation and reducing gene flow. Small, isolated, host populations may lose adaptive potential and become more susceptible to extinction due to other threats. Management of the genetic consequences of disease-induced population decline is often necessary. Whilst disease threats need to be addressed, they can be difficult to mitigate. Actions implemented to conserve the Tasmanian devil (Sarcophilus harrisii), which has suffered decline to the deadly devil facial tumour disease (DFTD), exemplify how genetic management can be used to reduce extinction risk in populations threatened by disease. Supplementation is an emerging conservation technique that may benefit populations threatened by disease by enabling gene flow and conserving their adaptive potential through genetic restoration. Other candidate species may benefit from genetic management via supplementation but concerns regarding outbreeding depression may prevent widespread incorporation of this technique into wildlife disease management. However, existing knowledge can be used to identify populations that would benefit from supplementation where risk of outbreeding depression is low. For populations threatened by disease and, in situations where disease eradication is not an option, wildlife managers should consider genetic management to buffer the host species against inbreeding and loss of genetic diversity.

scholarly journals No Place Like Home: Cross-National Data Analysis of the Efficacy of Social Distancing During the COVID-19 Pandemic

10.2196/19862 ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. e19862 ◽  
Author(s):  
Dursun Delen ◽  
Enes Eryarsoy ◽  
Behrooz Davazdahemami
Keyword(s):  
Disease Transmission ◽  
Transmission Rate ◽  
Disease Spread ◽  
Data Sets ◽  
Mobility Patterns ◽  
Social Distancing ◽  
Mobility Data ◽  
Simulation Based ◽  
Transactional Data ◽  
Cross National

Background In the absence of a cure in the time of a pandemic, social distancing measures seem to be the most effective intervention to slow the spread of disease. Various simulation-based studies have been conducted to investigate the effectiveness of these measures. While those studies unanimously confirm the mitigating effect of social distancing on disease spread, the reported effectiveness varies from 10% to more than 90% reduction in the number of infections. This level of uncertainty is mostly due to the complex dynamics of epidemics and their time-variant parameters. However, real transactional data can reduce uncertainty and provide a less noisy picture of the effectiveness of social distancing. Objective The aim of this paper was to integrate multiple transactional data sets (GPS mobility data from Google and Apple as well as disease statistics from the European Centre for Disease Prevention and Control) to study the role of social distancing policies in 26 countries and analyze the transmission rate of the coronavirus disease (COVID-19) pandemic over the course of 5 weeks. Methods Relying on the susceptible-infected-recovered (SIR) model and official COVID-19 reports, we first calculated the weekly transmission rate (β) of COVID-19 in 26 countries for 5 consecutive weeks. Then, we integrated these data with the Google and Apple mobility data sets for the same time frame and used a machine learning approach to investigate the relationship between the mobility factors and β values. Results Gradient boosted trees regression analysis showed that changes in mobility patterns resulting from social distancing policies explain approximately 47% of the variation in the disease transmission rates. Conclusions Consistent with simulation-based studies, real cross-national transactional data confirms the effectiveness of social distancing interventions in slowing the spread of COVID-19. In addition to providing less noisy and more generalizable support for the idea of social distancing, we provide specific insights for public health policy makers regarding locations that should be given higher priority for enforcing social distancing measures.

scholarly journals Extensive population decline in the Tasmanian devil predates European settlement and devil facial tumour disease

2014 ◽  
Vol 10 (11) ◽  
pp. 20140619 ◽  
Author(s):  
Anna Brüniche-Olsen ◽  
Menna E. Jones ◽  
Jeremy J. Austin ◽  
Christopher P. Burridge ◽  
Barbara R. Holland
Keyword(s):  
Genetic Diversity ◽  
Environmental Changes ◽  
Southern Oscillation ◽  
Demographic History ◽  
Population Decline ◽  
Tasmanian Devil ◽  
Term Survival ◽  
Temporal Sampling ◽  
Low Genetic Diversity ◽  
Devil Facial Tumour Disease

The Tasmanian devil ( Sarcophilus harrisii ) was widespread in Australia during the Late Pleistocene but is now endemic to the island of Tasmania. Low genetic diversity combined with the spread of devil facial tumour disease have raised concerns for the species’ long-term survival. Here, we investigate the origin of low genetic diversity by inferring the species' demographic history using temporal sampling with summary statistics, full-likelihood and approximate Bayesian computation methods. Our results show extensive population declines across Tasmania correlating with environmental changes around the last glacial maximum and following unstable climate related to increased ‘El Niño–Southern Oscillation’ activity.

scholarly journals Disease and the dynamics of extinction

2012 ◽  
Vol 367 (1604) ◽  
pp. 2828-2839 ◽  
Author(s):  
Hamish McCallum
Keyword(s):  
Infectious Diseases ◽  
Disease Transmission ◽  
Management Strategies ◽  
Host Density ◽  
Habitat Destruction ◽  
Broad Host Range ◽  
Tasmanian Devil ◽  
Management Options ◽  
Reservoir Species ◽  
Devil Facial Tumour Disease

Invading infectious diseases can, in theory, lead to the extinction of host populations, particularly if reservoir species are present or if disease transmission is frequency-dependent. The number of historic or prehistoric extinctions that can unequivocally be attributed to infectious disease is relatively small, but gathering firm evidence in retrospect is extremely difficult. Amphibian chytridiomycosis and Tasmanian devil facial tumour disease (DFTD) are two very different infectious diseases that are currently threatening to cause extinctions in Australia. These provide an unusual opportunity to investigate the processes of disease-induced extinction and possible management strategies. Both diseases are apparently recent in origin. Tasmanian DFTD is entirely host-specific but potentially able to cause extinction because transmission depends weakly, if at all, on host density. Amphibian chytridiomycosis has a broad host range but is highly pathogenic only to some populations of some species. At present, both diseases can only be managed by attempting to isolate individuals or populations from disease. Management options to accelerate the process of evolution of host resistance or tolerance are being investigated in both cases. Anthropogenic changes including movement of diseases and hosts, habitat destruction and fragmentation and climate change are likely to increase emerging disease threats to biodiversity and it is critical to further develop strategies to manage these threats.

scholarly journals Host Genetic Diversity and Infectious Diseases. Focus on Wild Boar, Red Deer and Tuberculosis

Animals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1630
Author(s):  
Javier Pérez-González ◽  
Juan Carranza ◽  
Remigio Martínez ◽  
José Manuel Benítez-Medina
Keyword(s):  
Genetic Diversity ◽  
Infectious Diseases ◽  
Wild Boar ◽  
Cervus Elaphus ◽  
Disease Transmission ◽  
Red Deer ◽  
Disease Spread ◽  
Disease Emergence ◽  
Host Genetic ◽  
Diversity Studies

Host genetic diversity tends to limit disease spread in nature and buffers populations against epidemics. Genetic diversity in wildlife is expected to receive increasing attention in contexts related to disease transmission and human health. Ungulates such as wild boar (Sus scrofa) and red deer (Cervus elaphus) are important zoonotic hosts that can be precursors to disease emergence and spread in humans. Tuberculosis is a zoonotic disease with relevant consequences and can present high prevalence in wild boar and red deer populations. Here, we review studies on the genetic diversity of ungulates and determine to what extent these studies consider its importance on the spread of disease. This assessment also focused on wild boar, red deer, and tuberculosis. We found a disconnection between studies treating genetic diversity and those dealing with infectious diseases. Contrarily, genetic diversity studies in ungulates are mainly concerned with conservation. Despite the existing disconnection between studies on genetic diversity and studies on disease emergence and spread, the knowledge gathered in each discipline can be applied to the other. The bidirectional applications are illustrated in wild boar and red deer populations from Spain, where TB is an important threat for wildlife, livestock, and humans.

scholarly journals Identification of effective spreaders in contact networks using dynamical influence

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Ruaridh A. Clark ◽  
Malcolm Macdonald
Keyword(s):  
Disease Transmission ◽  
Average Rate ◽  
Laplacian Matrix ◽  
Disease Spread ◽  
Eigenvector Centrality ◽  
Contact Networks ◽  
Human Contact ◽  
Spread Dynamics ◽  
Definition Of ◽  
High Degree

AbstractContact networks provide insights on disease spread due to the duration of close proximity interactions. For systems governed by consensus dynamics, network structure is key to optimising the spread of information. For disease spread over contact networks, the structure would be expected to be similarly influential. However, metrics that are essentially agnostic to the network’s structure, such as weighted degree (strength) centrality and its variants, perform near-optimally in selecting effective spreaders. These degree-based metrics outperform eigenvector centrality, despite disease spread over a network being a random walk process. This paper improves eigenvector-based spreader selection by introducing the non-linear relationship between contact time and the probability of disease transmission into the assessment of network dynamics. This approximation of disease spread dynamics is achieved by altering the Laplacian matrix, which in turn highlights why nodes with a high degree are such influential disease spreaders. From this approach, a trichotomy emerges on the definition of an effective spreader where, for susceptible-infected simulations, eigenvector-based selections can either optimise the initial rate of infection, the average rate of infection, or produce the fastest time to full infection of the network. Simulated and real-world human contact networks are examined, with insights also drawn on the effective adaptation of ant colony contact networks to reduce pathogen spread and protect the queen ant.

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