scholarly journals Genomic Epidemiology of Salmonid Alphavirus in Norwegian Aquaculture Reveals Recent Subtype-2 Transmission Dynamics and Novel Subtype-3 Lineages

Viruses ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2549
Author(s):  
Daniel J. Macqueen ◽  
Oliver Eve ◽  
Manu Kumar Gundappa ◽  
Rose Ruiz Daniels ◽  
Michael D. Gallagher ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Viral Evolution ◽  
Viral Disease ◽  
Transmission Dynamics ◽  
Disease Spread ◽  
Economic Losses ◽  
Fish Welfare ◽  
Major Barrier ◽  
Genomic Epidemiology ◽  
Northern Latitudes

Viral disease poses a major barrier to sustainable aquaculture, with outbreaks causing large economic losses and growing concerns for fish welfare. Genomic epidemiology can support disease control by providing rapid inferences on viral evolution and disease transmission. In this study, genomic epidemiology was used to investigate salmonid alphavirus (SAV), the causative agent of pancreas disease (PD) in Atlantic salmon. Our aim was to reconstruct SAV subtype-2 (SAV2) diversity and transmission dynamics in recent Norwegian aquaculture, including the origin of SAV2 in regions where this subtype is not tolerated under current legislation. Using nanopore sequencing, we captured ~90% of the SAV2 genome for n = 68 field isolates from 10 aquaculture production regions sampled between 2018 and 2020. Using time-calibrated phylogenetics, we infer that, following its introduction to Norway around 2010, SAV2 split into two clades (SAV2a and 2b) around 2013. While co-present at the same sites near the boundary of Møre og Romsdal and Trøndelag, SAV2a and 2b were generally detected in non-overlapping locations at more Southern and Northern latitudes, respectively. We provide evidence for recent SAV2 transmission over large distances, revealing a strong connection between Møre og Romsdal and SAV2 detected in 2019/20 in Rogaland. We also demonstrate separate introductions of SAV2a and 2b outside the SAV2 zone in Sognefjorden (Vestland), connected to samples from Møre og Romsdal and Trøndelag, respectively, and a likely 100 km Northward transmission of SAV2b within Trøndelag. Finally, we recovered genomes of SAV2a and SAV3 co-infecting single fish in Rogaland, involving novel SAV3 lineages that diverged from previously characterized strains >25 years ago. Overall, this study demonstrates useful applications of genomic epidemiology for tracking viral disease spread in aquaculture.

scholarly journals Pathogen transmission from vaccinated hosts can cause dose-dependent reduction in virulence

2019 ◽  
Author(s):  
Richard I. Bailey ◽  
Hans H. Cheng ◽  
Margo Chase-Topping ◽  
Jody K. Mays ◽  
Osvaldo Anacleto ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Infectious Virus ◽  
Pathogen Transmission ◽  
Transmission Dynamics ◽  
Disease Spread ◽  
Disease Development ◽  
Disease Symptoms ◽  
Pathogen Virulence ◽  
Pathogen Load ◽  
Dose Dependent

AbstractMany livestock and human vaccines are leaky as they block symptoms but do not prevent infection or onward transmission. This leakiness is concerning as it increases vaccination coverage required to prevent disease spread, and can promote evolution of increased pathogen virulence. Despite leakiness, vaccination may reduce pathogen load, affecting disease transmission dynamics. However, the impacts on post-transmission disease development and infectiousness in contact individuals are unknown. Here, we use transmission experiments involving Marek’s disease virus in chickens to show that vaccination with a leaky vaccine substantially reduces viral load in both vaccinated individuals and unvaccinated contact individuals they infect. Consequently, contact birds are less likely to develop disease symptoms or die, show less severe symptoms, and shed less infectious virus themselves, when infected by vaccinated birds. These results highlight that even partial vaccination with a leaky vaccine can have unforeseen positive consequences in controlling the spread and symptoms of disease.

scholarly journals Space-time patterns, change, and propagation of COVID-19 risk relative to the intervention scenarios in Bangladesh

2020 ◽  
Author(s):  
Arif Masrur ◽  
Manzhu Yu ◽  
Wei Luo ◽  
Ashraf Dewan
Keyword(s):  
Disease Transmission ◽  
Public Awareness ◽  
Space Time ◽  
Health Care Facilities ◽  
Transmission Dynamics ◽  
Disease Spread ◽  
Time Patterns ◽  
Significant Public Health ◽  
Novel Coronavirus ◽  
Elevated Exposure

The novel coronavirus (COVID-19) pandemic continues to be a significant public health threat worldwide. As of mid-June 2020, COVID-19 has spread worldwide with more than 7.7 million confirmed cases and more than 400,000 deaths. The impacts are substantial particularly in developing and densely populated countries like Bangladesh with inadequate health care facilities, where COVID-19 cases are currently surging. While early detection and isolation were identified as important non-pharmaceutical intervention (NPI) measures for containing the disease spread, this may not be pragmatically implementable in developing countries primarily due to social and economic reasons (i.e. poor education, less public awareness, massive unemployment). To shed light on COVID-19 transmission dynamics and impacts of NPI scenarios, e.g. social distancing, this study conducted emerging pattern analysis using the space-time scan statistic at district and thana (i.e. a sub-district or 'upazila' with at least one police station) levels in Bangladesh and its capital Dhaka city, respectively. We found that the central and south eastern regions in Bangladesh are currently exhibiting a high risk of COVID-19 transmission. Dhaka megacity remains as the highest risk "active" cluster since early April. The space-time progression of COVID-19 infection, when validated against the chronicle of government press releases and newspaper reports, suggests that Bangladesh have experienced a community level transmission at the early phase (i.e., March, 2020) primarily introduced by Bangladeshi citizens returning from coronavirus-affected countries in the Europe and the Middle East. A linkage is evident between the violation of NPIs and post-incubation period emergence of new clusters with elevated exposure risk around Bangladesh. This study provides novel insights into the space-time patterns of COVID-19 transmission dynamics and recommends pragmatic NPI implementation for reducing disease transmission and minimizing impacts in a resource-scarce country with Bangladesh as a case-study example.

scholarly journals Bee pathogen transmission dynamics: deposition, persistence and acquisition on flowers

2019 ◽  
Vol 286 (1903) ◽  
pp. 20190603 ◽  
Author(s):  
Laura L. Figueroa ◽  
Malcolm Blinder ◽  
Cali Grincavitch ◽  
Angus Jelinek ◽  
Emilia K. Mann ◽  
...  
Keyword(s):  
Plant Species ◽  
Disease Transmission ◽  
Infection Intensity ◽  
Sun Exposure ◽  
Lythrum Salicaria ◽  
Pathogen Transmission ◽  
Transmission Dynamics ◽  
Disease Spread ◽  
Pathogen Survival ◽  
Host Infection

Infectious diseases are a primary driver of bee decline worldwide, but limited understanding of how pathogens are transmitted hampers effective management. Flowers have been implicated as hubs of bee disease transmission, but we know little about how interspecific floral variation affects transmission dynamics. Using bumblebees ( Bombus impatiens ), a trypanosomatid pathogen ( Crithidia bombi ) and three plant species varying in floral morphology, we assessed how host infection and plant species affect pathogen deposition on flowers, and plant species and flower parts impact pathogen survival and acquisition at flowers. We found that host infection with Crithidia increased defaecation rates on flowers, and that bees deposited faeces onto bracts of Lobelia siphilitica and Lythrum salicaria more frequently than onto Monarda didyma bracts . Among flower parts, bracts were associated with the lowest pathogen survival but highest resulting infection intensity in bee hosts. Additionally, we found that Crithidia survival across flower parts was reduced with sun exposure. These results suggest that efficiency of pathogen transmission depends on where deposition occurs and the timing and place of acquisition, which varies among plant species and environmental conditions. This information could be used for development of wildflower mixes that maximize forage while minimizing disease spread.

AVIAN INFLUENZA AND ITS MASS DEPOPULATION STRATEGIES IN INFECTED POULTRY BIRDS

2015 ◽  
Vol 41 (02) ◽  
pp. 51-57
Author(s):  
Rabia Tahir ◽  
Aftab Ahmed Anjum ◽  
Khushi Muhammad ◽  
Asfa Rasool ◽  
Farah Khan
Keyword(s):  
Avian Influenza ◽  
Large Scale ◽  
Stocking Density ◽  
Infectious Agent ◽  
Viral Disease ◽  
Disease Spread ◽  
Economic Losses ◽  
Poultry Birds ◽  
Pain And Suffering ◽  
Human Operators

Avian influenza (AI) is a highly contagious and zoonotic viral disease that affects several animal species. It causes heavy economic losses in the domestic poultry. A quick response is always desired in the event of any disease outbreak. The principal approach to control a contagious disease involves the killing of diseased animals along with the bio containment of infectious agent. Mass depopulation of the infected birds plays an important role in the eradication of the disease. The possible strategies for mass depopulation include maceration, electrocution, cervical dislocation, gassing and foaming. All of these procedures are much intensive and time consuming because it involves a lot of man power, biosecurity risks, applicability for all house types and suitability for large-scale emergency implementation. The basic objectives of these strategies include (1) To reduce pain and suffering to the birds, (2) To minimize disease spread and (3) To ensure of protection to human operators from potential biohazards. A suitable depopulation technique can only be suggested keeping in view the species and type of bird involved, and differences in husbandry practices like management, housing and stocking density. Mass depopulation is an important tool to control the spread of any disease but the selection of procedure depends upon the prevailing circumstances. In this paper, various mass depopulation strategies and their selection in different conditions is reviewed and discussed.

scholarly journals Predicting the Time to Detect Moderately Virulent African Swine Fever Virus in Finisher Swine Herds Using a Stochastic Disease Transmission Model

2021 ◽  
Author(s):  
Sasidhar Malladi ◽  
Amos Ssematimba ◽  
Peter J. Bonney ◽  
Kaitlyn M. St. Charles ◽  
Timothy Boyer ◽  
...  
Keyword(s):  
Disease Transmission ◽  
African Swine Fever Virus ◽  
Clinical Signs ◽  
African Swine Fever ◽  
The United States ◽  
Disease Spread ◽  
Transmission Model ◽  
Economic Losses ◽  
Parameter Estimates ◽  
Disease Transmission Model

Abstract Background: African swine fever (ASF) is a highly contagious and devastating pig disease that has caused extensive global economic losses. Understanding ASF virus (ASFV) transmission dynamics within a herd is necessary in order to prepare for and respond to an outbreak in the United States. Although the transmission parameters for the highly virulent ASF strains have been estimated in several articles, there are relatively few studies focused on moderately virulent strains. Using an approximate Bayesian computation algorithm in conjunction with Monte Carlo simulation, we have estimated the adequate contact rate for moderately virulent ASFV strains and determined the statistical distributions for the durations of mild and severe clinical signs using individual, pig-level data. A discrete individual based disease transmission model was then used to estimate the time to detect ASF infection based on increased mild clinical signs, severe clinical signs, or daily mortality. Results: Our results indicate that it may take two weeks or longer to detect ASF in a finisher swine herd via mild clinical signs or increased mortality beyond levels expected in routine production. A key factor contributing to the extended time to detect ASF in a herd is the fairly long latently infected period for an individual pig (mean 4.5, 95% P.I., 2.4 - 7.2 days). Conclusion: These transmission model parameter estimates and estimated time to detection via clinical signs provide valuable information that can be used not only to support emergency preparedness but also to inform other simulation models of evaluating regional disease spread.

Simulating disease transmission dynamics at a multi-scale level

2007 ◽  
Vol 1 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Moshe B Hoshen ◽  
Anthony H Burton ◽  
Themis J V Bowcock
Keyword(s):  
Disease Transmission ◽  
Transmission Dynamics ◽  
Scale Level ◽  
Multi Scale

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.

scholarly journals Livestock movement informs the risk of disease spread in traditional production systems in East Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Divine Ekwem ◽  
Thomas A. Morrison ◽  
Richard Reeve ◽  
Jessica Enright ◽  
Joram Buza ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Production Systems ◽  
Control Strategies ◽  
Herd Size ◽  
Transmission Risk ◽  
Disease Spread ◽  
Transmission Potential ◽  
Spatial And Temporal Scales ◽  
Transmission Distance ◽  
Risk Of Disease

AbstractIn Africa, livestock are important to local and national economies, but their productivity is constrained by infectious diseases. Comprehensive information on livestock movements and contacts is required to devise appropriate disease control strategies; yet, understanding contact risk in systems where herds mix extensively, and where different pathogens can be transmitted at different spatial and temporal scales, remains a major challenge. We deployed Global Positioning System collars on cattle in 52 herds in a traditional agropastoral system in western Serengeti, Tanzania, to understand fine-scale movements and between-herd contacts, and to identify locations of greatest interaction between herds. We examined contact across spatiotemporal scales relevant to different disease transmission scenarios. Daily cattle movements increased with herd size and rainfall. Generally, contact between herds was greatest away from households, during periods with low rainfall and in locations close to dipping points. We demonstrate how movements and contacts affect the risk of disease spread. For example, transmission risk is relatively sensitive to the survival time of different pathogens in the environment, and less sensitive to transmission distance, at least over the range of the spatiotemporal definitions of contacts that we explored. We identify times and locations of greatest disease transmission potential and that could be targeted through tailored control strategies.

scholarly journals Sheep scab spatial distribution: the roles of transmission pathways

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Emily Joanne Nixon ◽  
Ellen Brooks-Pollock ◽  
Richard Wall
Keyword(s):  
Disease Transmission ◽  
Movement Control ◽  
Cost Effective ◽  
Infected Sheep ◽  
Disease Spread ◽  
Psoroptes Ovis ◽  
Long Distance ◽  
Sheep Scab ◽  
The Uk ◽  
The Impact

Abstract Background Ovine psoroptic mange (sheep scab) is a highly pathogenic contagious infection caused by the mite Psoroptes ovis. Following 21 years in which scab was eradicated in the UK, it was inadvertently reintroduced in 1972 and, despite the implementation of a range of control methods, its prevalence increased steadily thereafter. Recent reports of resistance to macrocyclic lactone treatments may further exacerbate control problems. A better understanding of the factors that facilitate its transmission are required to allow improved management of this disease. Transmission of infection occurs within and between contiguous sheep farms via infected sheep-to-sheep or sheep–environment contact and through long-distance movements of infected sheep, such as through markets. Methods A stochastic metapopulation model was used to investigate the impact of different transmission routes on the spatial pattern of outbreaks. A range of model scenarios were considered following the initial infection of a cluster of highly connected contiguous farms. Results Scab spreads between clusters of neighbouring contiguous farms after introduction but when long-distance movements are excluded, infection then self-limits spatially at boundaries where farm connectivity is low. Inclusion of long-distance movements is required to generate the national patterns of disease spread observed. Conclusions Preventing the movement of scab infested sheep through sales and markets is essential for any national management programme. If effective movement control can be implemented, regional control in geographic areas where farm densities are high would allow more focussed cost-effective scab management. Graphical Abstract

scholarly journals The effects of flooding and weather conditions on leptospirosis transmission in Thailand

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sudarat Chadsuthi ◽  
Karine Chalvet-Monfray ◽  
Anuwat Wiratsudakul ◽  
Charin Modchang
Keyword(s):  
Sensitivity Analysis ◽  
Public Education ◽  
Mathematical Models ◽  
Disease Transmission ◽  
Transmission Rate ◽  
Weather Conditions ◽  
Transmission Dynamics ◽  
Multiplication Rate ◽  
High Degree ◽  
Transmission Models

AbstractThe epidemic of leptospirosis in humans occurs annually in Thailand. In this study, we have developed mathematical models to investigate transmission dynamics between humans, animals, and a contaminated environment. We compared different leptospire transmission models involving flooding and weather conditions, shedding and multiplication rate in a contaminated environment. We found that the model in which the transmission rate depends on both flooding and temperature, best-fits the reported human data on leptospirosis in Thailand. Our results indicate that flooding strongly contributes to disease transmission, where a high degree of flooding leads to a higher number of infected individuals. Sensitivity analysis showed that the transmission rate of leptospires from a contaminated environment was the most important parameter for the total number of human cases. Our results suggest that public education should target people who work in contaminated environments to prevent Leptospira infections.

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