scholarly journals Hydrology-informed metapopulation modeling of liver fluke transmission in the Lawa Lake complex of northeast Thailand

2019 ◽  
Author(s):  
Tomás M. León ◽  
Vichian Plermkamon ◽  
Kittiwet Kuntiyawichai ◽  
Banchob Sripa ◽  
Robert C. Spear
Keyword(s):  
Disease Transmission ◽  
Liver Fluke ◽  
Pathogen Transmission ◽  
Transmission Dynamics ◽  
Northeast Thailand ◽  
Metapopulation Model ◽  
Hydrologic Processes ◽  
Lake System ◽  
Hydrologic Data ◽  
Liver Flukes

AbstractWhile hydrologic processes are intuitively understood to influence transmission dynamics of water-related diseases, limited research exists that explicitly links hydrologic and infectious disease data. In the case of the life cycle of liver flukes, hydrology influences several transmission processes that mediate infection risk for multiple hosts. Northeast Thailand is a hotspot for liver fluke transmission and has strong seasonal flooding patterns. A metapopulation model linking local hydrologic processes with transmission of the liver fluke Opisthorchis viverrini in a lake system in northeast Thailand was developed and parameterized using infection data from 2008-2016. A rainfall-runoff model and other hydrologic data were used to assess level of connectivity between villages and the influence of upstream communities on parasite distribution in the study area. Disease transmission was modeled with metapopulations representing six village clusters around the lake using known prevalence data from humans, cats and dogs, snails, and fish. The metapopulation model improved upon the single-village model in its match to historical data patterns for the six village clusters with the introduction of the new time-variable parameters. Results suggest there are three unique hydrologic-epidemiologic regimes within the Lawa Lake system in response to upstream watersheds and risk of overland flooding that contribute to risk for O. viverrini infection. While available data may be insufficient to specifically characterize exact transmission dynamics, the practical implications of such findings are the importance of addressing connectivity for any intermediate host-based intervention. Similar approaches using hydrologic data to assess the impacts of water on pathogen transmission dynamics and inform mechanistic disease transmission models could be applied across other water-related disease systems.

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 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.

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 Quantity and Quality of Aquaculture Enrichments Influence Disease Epidemics and Provide Ecological Alternatives to Antibiotics

Antibiotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 335
Author(s):  
Anssi Karvonen ◽  
Ville Räihä ◽  
Ines Klemme ◽  
Roghaieh Ashrafi ◽  
Pekka Hyvärinen ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Bacterial Infections ◽  
Environmental Heterogeneity ◽  
Pathogen Transmission ◽  
Central Component ◽  
Flavobacterium Columnare ◽  
Disease Epidemics ◽  
The Impact ◽  
Environmental Microbes

Environmental heterogeneity is a central component influencing the virulence and epidemiology of infectious diseases. The number and distribution of susceptible hosts determines disease transmission opportunities, shifting the epidemiological threshold between the spread and fadeout of a disease. Similarly, the presence and diversity of other hosts, pathogens and environmental microbes, may inhibit or accelerate an epidemic. This has important applied implications in farming environments, where high numbers of susceptible hosts are maintained in conditions of minimal environmental heterogeneity. We investigated how the quantity and quality of aquaculture enrichments (few vs. many stones; clean stones vs. stones conditioned in lake water) influenced the severity of infection of a pathogenic bacterium, Flavobacterium columnare, in salmonid fishes. We found that the conditioning of the stones significantly increased host survival in rearing tanks with few stones. A similar effect of increased host survival was also observed with a higher number of unconditioned stones. These results suggest that a simple increase in the heterogeneity of aquaculture environment can significantly reduce the impact of diseases, most likely operating through a reduction in pathogen transmission (stone quantity) and the formation of beneficial microbial communities (stone quality). This supports enriched rearing as an ecological and economic way to prevent bacterial infections with the minimal use of antimicrobials.

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.

scholarly journals Estimasi Reproduction Number Model Matematika Penyebaran Malaria di Sumba Tengah, Indonesia

2021 ◽  
Vol 2 (1) ◽  
pp. 13-19
Author(s):  
Ervin Mawo Banni ◽  
Maria A Kleden ◽  
Maria Lobo ◽  
Meksianis Zadrak Ndii
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Health Center ◽  
Disease Transmission ◽  
Reproduction Number ◽  
Transmission Dynamics ◽  
Awareness Program ◽  
Awareness Programs ◽  
Malaria Eradication

Malaria is transmitted via a bite of mosquitoes and it is dangerous if it is not properly treated. Mathematical modeling can be formulated to understand the disease transmission dynamics. In this paper, a mathematical model with an awareness program has been formulated and the reproduction number has been estimated against the data from Weeluri Health Center, Mamboro District, Central Sumba. The calculation showed that the reproduction number is R0 = 1.2562. Results showed that if the efficacy of the awareness program is lower than 20%, the reproduction number is still above unity. If the efficacy of the awareness program is higher than 20%, the reproduction number is lower than unity. This implies that the efficacy of awareness programs is the key to the success of Malaria eradication.

scholarly journals Relatedness and genetic structure of big brown bat (Eptesicus fuscus) maternity colonies in an urban-wildland interface provides insight into rabies transmission dynamics

2020 ◽  
Author(s):  
Faith M. Walker ◽  
Colin J. Sobek ◽  
Camille E. Platts-McPharlin ◽  
Carol L. Chambers
Keyword(s):  
Genetic Structure ◽  
Disease Transmission ◽  
Urban Areas ◽  
Genetic Relatedness ◽  
Radio Telemetry ◽  
Eptesicus Fuscus ◽  
Geographic Mobility ◽  
Transmission Dynamics ◽  
Urocyon Cinereoargenteus ◽  
Disease Exposure

AbstractBig brown bats (Eptesicus fuscus) are the bat species most frequently found to be rabid in North America and are a key source of sylvatic rabies in wildlife. Females can form summer maternity colonies in urban areas, often using access holes in the exterior of buildings to roost in relatively large numbers. In Flagstaff, Arizona, these roosts are commonly found in houses adjacent to golf courses, where habitat quality (food, water, shelter) is high for bats and for mesocarnivores such as striped skunks (Mephitis mephitis) and gray foxes (Urocyon cinereoargenteus). Periodic rabies outbreaks in Flagstaff involving all three of these mammals are primarily caused by an E. fuscus variant of the disease. However, little is known about E. fuscus social behavior during the summer months and how it may drive space use and hence disease exposure to conspecifics and mesocarnivores. To address this knowledge gap, we collected 88 unique genetic samples via buccal swabs from E. fuscus captured at four maternity roosts surrounding a golf course during summer of 2013. We used 7 microsatellite loci to estimate genetic relatedness among individuals and genetic structure within and among colonies in order to infer whether females selected roosts based on kinship, and used genetics and radio telemetry to determine the frequency of roost switching. We found roost switching through genetics (two mother and adult daughter pairs at the same and different roosts) and telemetry, and no evidence of elevated genetic relatedness within colonies or genetic structure between colonies. These results have important implications for disease transmission dynamics in that social cohesion based on relatedness does not act to constrain the virus to a particular roost area. Instead, geographic mobility may increase disease exposure to neighboring areas. We discuss mitigating actions for bat conservation and public health.

Characterisation of two calmodulin-like proteins from the liver fluke, Fasciola hepatica

2007 ◽  
Vol 388 (6) ◽  
pp. 593-599 ◽  
Author(s):  
Sean L. Russell ◽  
Neil V. McFerran ◽  
Elizabeth M. Hoey ◽  
Alan Trudgett ◽  
David J. Timson
Keyword(s):  
Metal Binding ◽  
Metal Ion ◽  
Liver Fluke ◽  
Fasciola Hepatica ◽  
Expression Vectors ◽  
Metal Ion Binding ◽  
Ion Sensing ◽  
Calcium Magnesium ◽  
Ion Binding Sites ◽  
Liver Flukes

Abstract Calmodulin is a calcium ion-sensing signalling protein found in eukaryotics. Two calmodulin-like gene sequences were identified in an EST library from adult liver flukes. One codes for a protein (FhCaM1) homologous to mammalian calmodulins (98% identity), whereas the other protein (FhCaM2) has only 41% identity. These genes were cloned into expression vectors and the recombinant proteins were expressed in Escherichia coli. Gel shift assays showed that both proteins bind to calcium, magnesium and zinc ions. Homology models have been built for both proteins. As expected, FhCaM1 has a highly similar structure to other calmodulins. Although FhCaM2 has a similar fold, its surface charge is higher than FhCaM1. One of the potential metal ion-binding sites has lower metal-ion co-ordination capability, while another has an adjacent lysine residue, both of which may decrease the metal-binding affinity. These differences may reflect a specialised role for FhCaM2 in the liver fluke.

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