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Journal of Neurovirology Jun 2015The AIDS research field has embarked on a bold mission to cure HIV-1-infected individuals of the virus. To do so, scientists are attempting to identify the reservoirs... (Review)
Review
The AIDS research field has embarked on a bold mission to cure HIV-1-infected individuals of the virus. To do so, scientists are attempting to identify the reservoirs that support viral persistence in patients on therapy, to understand how viral persistence is regulated and to come up with strategies that interrupt viral persistence and that eliminate the viral reservoirs. Most of the attention regarding the cure of HIV-1 infection has focused on the CD4+ T cell reservoir. Investigators are developing tools to probe the CD4+ T cell reservoirs as well as in vitro systems that provide clues on how to perturb them. By comparison, the myeloid cell, and in particular, the macrophage has received far less attention. As a consequence, there is very little understanding as to the role played by myeloid cells in viral persistence in HIV-1-infected individuals on suppressive therapy. As such, should myeloid cells constitute a viral reservoir, unique strategies may be required for their elimination. This article will overview research that is examining the role of macrophage in virus-host interplay and will discuss features of this interplay that could impact efforts to eliminate myeloid cell reservoirs.
Topics: Disease Reservoirs; HIV Infections; HIV-1; Host-Parasite Interactions; Humans; Myeloid Cells; Virus Latency
PubMed: 25236811
DOI: 10.1007/s13365-014-0281-3 -
Philosophical Transactions of the Royal... Sep 2019Predicting pathogen spillover requires counting spillover events and aligning such counts with process-related covariates for each spillover event. How can we connect...
Predicting pathogen spillover requires counting spillover events and aligning such counts with process-related covariates for each spillover event. How can we connect our analysis of spillover counts to simple, mechanistic models of pathogens jumping from reservoir hosts to recipient hosts? We illustrate how the pathways to pathogen spillover can be represented as a directed graph connecting reservoir hosts and recipient hosts and the number of spillover events modelled as a percolation of infectious units along that graph. Percolation models of pathogen spillover formalize popular intuition and management concepts for pathogen spillover, such as the inextricably multilevel nature of cross-species transmission, the impact of covariance between processes such as pathogen shedding and human susceptibility on spillover risk, and the assumptions under which the effect of a management intervention targeting one process, such as persistence of vectors, will translate to an equal effect on the overall spillover risk. Percolation models also link statistical analysis of spillover event datasets with a mechanistic model of spillover. Linear models, one might construct for process-specific parameters, such as the log-rate of shedding from one of several alternative reservoirs, yield a nonlinear model of the log-rate of spillover. The resulting nonlinearity is approximately piecewise linear with major impacts on statistical inferences of the importance of process-specific covariates such as vector density. We recommend that statistical analysis of spillover datasets use piecewise linear models, such as generalized additive models, regression clustering or ensembles of linear models, to capture the piecewise linearity expected from percolation models. We discuss the implications of our findings for predictions of spillover risk beyond the range of observed covariates, a major challenge of forecasting spillover risk in the Anthropocene. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.
Topics: Animals; Communicable Diseases, Emerging; Disease Reservoirs; Humans; Models, Theoretical; Zoonoses
PubMed: 31401950
DOI: 10.1098/rstb.2018.0331 -
Trends in Parasitology Jul 2015Renewed interest in malaria eradication has placed greater emphasis on the development of tools to interrupt Plasmodium transmission, such as transmission-blocking... (Review)
Review
Renewed interest in malaria eradication has placed greater emphasis on the development of tools to interrupt Plasmodium transmission, such as transmission-blocking vaccines. However, effective deployment of such tools is likely to depend on improving our understanding of which individuals transmit infections to mosquitoes. To date, only a handful of studies have directly determined the infectiousness of individuals in endemic populations. Here we review these studies and their relative merits. We also highlight factors influencing transmission potential that are not normally considered: the duration of human infectiousness, frequency of sampling by mosquitoes, and variation in vector competence among different mosquito populations. We argue that more comprehensive xenodiagnostic assessments of infectivity are necessary to accurately quantify the infectious reservoir and better target interventions.
Topics: Animals; Culicidae; Disease Reservoirs; Humans; Malaria, Falciparum; Plasmodium falciparum
PubMed: 25985898
DOI: 10.1016/j.pt.2015.04.004 -
Infection, Genetics and Evolution :... Dec 2018The life cycle of spirochetes of the genus Borrelia includes complex networks of vertebrates and ticks. The tripartite association of Borrelia-vertebrate-tick has proved... (Review)
Review
The life cycle of spirochetes of the genus Borrelia includes complex networks of vertebrates and ticks. The tripartite association of Borrelia-vertebrate-tick has proved ecologically successful for these bacteria, which have become some of the most prominent tick-borne pathogens in the northern hemisphere. To keep evolutionary pace with its double-host life history, Borrelia must adapt to the evolutionary pressures exerted by both sets of hosts. In this review, we attempt to reconcile functional, phylogenetic, and ecological perspectives to propose a coherent scenario of Borrelia evolution. Available empirical information supports that the association of Borrelia with ticks is very old. The major split between the tick families Argasidae-Ixodidae (dated some 230-290 Mya) resulted in most relapsing fever (Rf) species being restricted to Argasidae and few associated with Ixodidae. A further key event produced the diversification of the Lyme borreliosis (Lb) species: the radiation of ticks of the genus Ixodes from the primitive stock of Ixodidae (around 217 Mya). The ecological interactions of Borrelia demonstrate that Argasidae-transmitted Rf species remain restricted to small niches of one tick species and few vertebrates. The evolutionary pressures on this group are consequently low, and speciation processes seem to be driven by geographical isolation. In contrast to Rf, Lb species circulate in nested networks of dozens of tick species and hundreds of vertebrate species. This greater variety confers a remarkably variable pool of evolutionary pressures, resulting in large speciation of the Lb group, where different species adapt to circulate through different groups of vertebrates. Available data, based on ospA and multilocus sequence typing (including eight concatenated in-house genes) phylogenetic trees, suggest that ticks could constitute a secondary bottleneck that contributes to Lb specialization. Both sets of adaptive pressures contribute to the resilience of highly adaptable meta-populations of bacteria.
Topics: Adaptation, Biological; Animals; Biological Evolution; Borrelia; Disease Reservoirs; Disease Vectors; Host-Pathogen Interactions; Humans; Lyme Disease; Selection, Genetic; Ticks
PubMed: 29654924
DOI: 10.1016/j.meegid.2018.03.023 -
Transboundary and Emerging Diseases Jul 2022Countries survey wildlife for bovine tuberculosis (bTB) to ensure case detection or to ascertain a high probability of freedom from bTB in wildlife. The Eurasian badger...
Countries survey wildlife for bovine tuberculosis (bTB) to ensure case detection or to ascertain a high probability of freedom from bTB in wildlife. The Eurasian badger (Meles meles) is a potential bTB reservoir host. Between 2008 and 2019, 282 badgers were examined post-mortem in the context of general wildlife disease and targeted bTB surveillance programmes in the Netherlands, and no bTB cases were detected. However, it was unclear how effective this surveillance effort was to demonstrate freedom from Mycobacterium bovis infection in the badger population of ±6000 or to detect cases if present. Therefore, surveillance effectiveness was assessed using scenario tree modelling. For lack of standards for wildlife, the models were run against three assumed levels of disease in the population called design prevalence P*: 0.1%, 0.5%, and 3%. A small risk of introduction (0.015/year) was applied, because the Netherlands are officially free from bTB in cattle, with rare import of bTB-infected cattle and no bTB-infected wildlife reported along the Belgian and German borders with the Netherlands. Surveillance more readily picks up bTB presence in badgers when case detection sensitivity tends towards 100% and demonstrates freedom best when the probability of freedom tends towards 100%. For P* 0.1%, 0.5% and 3%, respectively, maximum case detection sensitivity during 2008-2019 was 8%, 35% and 94% and the probability of freedom in 2019 was 46%, 67%, and 95%. At P* = 3%, performing targeted surveillance on 300 badgers in a year would make it extremely unlikely to miss a case (case detection sensitivity > 99.9%); and if no cases are detected, the adjusted probability of freedom would then reach nearly 98.5%. Stakeholders should be made aware that at P* = 3%, one case detected implies around 3% infected badgers. Additional surveillance system components to assess bTB in wildlife and its economics are to be explored further.
Topics: Animals; Animals, Wild; Cattle; Cattle Diseases; Disease Reservoirs; Mustelidae; Mycobacterium bovis; Prevalence; Tuberculosis, Bovine
PubMed: 34110708
DOI: 10.1111/tbed.14186 -
Communications Biology Nov 2021Powassan virus lineage 2 (deer tick virus) is an emergent threat to American public health, causing severe neurologic disease. Its life cycle in nature remains poorly...
Powassan virus lineage 2 (deer tick virus) is an emergent threat to American public health, causing severe neurologic disease. Its life cycle in nature remains poorly understood. We use a host-specific retrotransposon-targeted real time PCR assay to test the hypothesis that white-footed mice, considered the main eastern U.S. reservoir of the coinfecting agent of Lyme disease, is the reservoir for deer tick virus. Of 20 virus-infected host-seeking nymphal black-legged ticks 65% fed on shrews and none on mice. The proportion of ticks feeding on shrews at a site is positively associated with prevalence of viral infection, but not the Lyme disease agent. Viral RNA is detected in the brain of one shrew. We conclude that shrews are a likely reservoir host for deer tick virus and that host bloodmeal analysis can provide direct evidence to incriminate reservoir hosts, thereby promoting our understanding of the ecology of tick-borne infections.
Topics: Animals; Disease Reservoirs; Encephalitis Viruses, Tick-Borne; Encephalitis, Tick-Borne; Massachusetts; Rhode Island; Shrews
PubMed: 34811484
DOI: 10.1038/s42003-021-02828-1 -
Viruses Jul 2021Rodents (order Rodentia), followed by bats (order Chiroptera), comprise the largest percentage of living mammals on earth. Thus, it is not surprising that these two... (Review)
Review
Rodents (order Rodentia), followed by bats (order Chiroptera), comprise the largest percentage of living mammals on earth. Thus, it is not surprising that these two orders account for many of the reservoirs of the zoonotic RNA viruses discovered to date. The spillover of these viruses from wildlife to human do not typically result in pandemics but rather geographically confined outbreaks of human infection and disease. While limited geographically, these viruses cause thousands of cases of human disease each year. In this review, we focus on three questions regarding zoonotic viruses that originate in bats and rodents. First, what biological strategies have evolved that allow RNA viruses to reside in bats and rodents? Second, what are the environmental and ecological causes that drive viral spillover? Third, how does virus spillover occur from bats and rodents to humans?
Topics: Animals; Chiroptera; Disease Outbreaks; Disease Reservoirs; Humans; Rodentia; Virus Diseases; Zoonoses
PubMed: 34452374
DOI: 10.3390/v13081509 -
Vector Borne and Zoonotic Diseases... Mar 2021Although rodents are well-known reservoirs and vectors for a number of zoonoses, the functional role that peridomestic rodents serve in the amplification and... (Review)
Review
Although rodents are well-known reservoirs and vectors for a number of zoonoses, the functional role that peridomestic rodents serve in the amplification and transmission of foodborne pathogens is likely underappreciated. Clear links have been identified between commensal rodents and outbreaks of foodborne pathogens throughout Europe and Asia; however, comparatively little research has been devoted to studying this relationship in the United States. In particular, regional studies focused on specific rodent species and their foodborne pathogen reservoir status across the diverse agricultural landscapes of the United States are lacking. We posit that both native and invasive species of rodents associated with food-production pipelines are likely sources of seasonal outbreaks of foodborne pathogens throughout the United States. In this study, we review the evidence that identifies peridomestic rodents as reservoirs for foodborne pathogens, and we call for novel research focused on the metagenomic communities residing at the rodent-agriculture interface. Such data will likely result in the identification of new reservoirs for foodborne pathogens and species-specific demographic traits that might underlie seasonal enteric disease outbreaks. Moreover, we anticipate that a One Health metagenomic research approach will result in the discovery of new strains of zoonotic pathogens circulating in peridomestic rodents. Data resulting from such research efforts would directly inform and improve upon biosecurity efforts, ultimately serving to protect our food supply.
Topics: Animals; Biosecurity; Disease Outbreaks; Disease Reservoirs; Europe; Rodentia; United States; Zoonoses
PubMed: 33351736
DOI: 10.1089/vbz.2020.2640 -
Journal of the Royal Society, Interface Jul 2022In this article, we take a mathematical approach to the study of population-level disease spread, performing a quantitative and qualitative investigation of an model...
In this article, we take a mathematical approach to the study of population-level disease spread, performing a quantitative and qualitative investigation of an model which is a susceptible-infectious-susceptible () model with exposure to an external disease reservoir. The external reservoir is non-dynamic, and exposure from the external reservoir is assumed to be proportional to the size of the susceptible population. The full stochastic system is modelled using a master equation formalism. A constant population size assumption allows us to solve for the stationary probability distribution, which is then used to investigate the predicted disease prevalence under a variety of conditions. By using this approach, we quantify outbreak vulnerability by performing the sensitivity analysis of disease prevalence to changing population characteristics. In addition, the shape of the probability density function is used to understand where, in parameter space, there is a transition from disease free, to disease present, and to a disease endemic system state. Finally, we use Kullback-Leibler divergence to compare our semi-analytical results for the model with more complex susceptible-infectious-recovered () and susceptible-exposed-infectious-recovered () models.
Topics: Communicable Diseases; Disease Outbreaks; Disease Reservoirs; Disease Susceptibility; Epidemiological Models; Humans; Models, Biological; Stochastic Processes
PubMed: 35857906
DOI: 10.1098/rsif.2022.0253 -
Reviews on Environmental Health Sep 2018
Review
Topics: Acinetobacter; Acinetobacter Infections; Disease Reservoirs; Environment; Humans; Prevalence; Soil Microbiology; Water Microbiology
PubMed: 29982240
DOI: 10.1515/reveh-2017-0034