ABSTRACT
Extremely contagious pathogens are a global biosecurity threat because of their high burden of morbidity and mortality, as well as their capacity for fast-moving epidemics that are difficult to quell. Understanding the mechanisms enabling persistence of highly transmissible pathogens in host populations is thus a central problem in disease ecology. Through a combination of experimental and theoretical approaches, we investigated how highly contagious foot-and-mouth disease viruses persist in the African buffalo, which serves as their wildlife reservoir. We found that viral persistence through transmission among acutely infected hosts alone is unlikely. However, the inclusion of occasional transmission from persistently infected carriers reliably rescues the most infectious viral strain from fade-out. Additional mechanisms such as antigenic shift, loss of immunity, or spillover among host populations may be required for persistence of less transmissible strains.
Subject(s)
Buffaloes/virology , Endemic Diseases/veterinary , Foot-and-Mouth Disease Virus/pathogenicity , Foot-and-Mouth Disease/transmission , Foot-and-Mouth Disease/virology , Animals , Foot-and-Mouth Disease Virus/isolation & purification , Population , Zoonoses/virologyABSTRACT
Peritumoral lesions identified during in vivo imaging of feline injection-site sarcoma (FISS) are frequently interpreted as neoplastic. We recently showed that most peritumoral imaging-identified lesions (PTIILs) in FISS are non-neoplastic. In this article, we describe a protocol to target PTIIL for microscopic examination and report on the protocol's performance. Ten client-owned cats with FISS were prospectively enrolled. A fiducial marker sutured onto the skin, centered on the palpable mass, served as reference point throughout the study. Each FISS and surrounding tissue was imaged in vivo by dual phase computed tomography angiography and multiple magnetic resonance imaging pulse sequences and each PTIIL documented. Subgross measurements obtained during trimming aided localization and identification of PTIIL during microscopy. Histologic findings were categorized by descending clinical relevance: neoplastic, equivocal, non-neoplastic, within normal limits (WNL). Based on in vivo imaging resolution limits, histologic findings were ≥3 mm in at least one dimension and ≥3 mm apart. Surgical margins served as control tissue for PTIILs. Eighty-one of 87 PTIIL were examined histologically; 13 were neoplastic, 16 equivocal, and 28 non-neoplastic; 24 had no identified histologic correlate. Two neoplastic and 10 equivocal findings were located outside of PTIILs but none of them were located in sections of surgical margins. Computation of a simple confusion matrix yielded fair sensitivity (70.4%) and low specificity (59.7%) for prediction of PTIIL by histologic findings. After combining instances of normal microanatomy with non-neoplastic histologic findings, specificity increased (85.1%) and sensitivity decreased (35.8%). The protocol is a blueprint for targeting PTIIL for microscopic examination but may benefit from further refinement.
Subject(s)
Cat Diseases , Sarcoma , Soft Tissue Neoplasms , Animals , Cat Diseases/diagnostic imaging , Cats , Magnetic Resonance Imaging/veterinary , Microscopy/veterinary , Sarcoma/diagnostic imaging , Sarcoma/veterinary , Soft Tissue Neoplasms/diagnostic imaging , Soft Tissue Neoplasms/veterinary , Tomography, X-Ray Computed/veterinaryABSTRACT
We consider a modified Holling-type II predator-prey model, based on the premise that the search rate of predators is dependent on the prey density, rather than constant. A complete analysis of the global behavior of the model is presented, and shows that the model exhibits a dichotomy similar to the classical Holling-type II model: either the coexistence steady state is globally stable; or it is unstable, and then a unique, globally stable limit cycle exists. We discuss the similarities, but also important differences between our model and the Holling-type II model. The main differences are that: 1. The paradox of enrichment which always occurs in the Holling-type II model, does not always occur here, and 2. Even when the paradox of enrichment occurs, predators can adapt by lowering their search rate, and effectively stabilize the system.
Subject(s)
Models, Biological , Predatory Behavior , Animals , Ecosystem , Food Chain , Population DynamicsABSTRACT
Within food webs, vectors of plant pathogens interact with individuals of other species across multiple trophic levels, including predators, competitors, and mutualists. These interactions may in turn affect vector-borne pathogens by altering vector fitness and behavior. Predators, for example, consume vectors and reduce their abundance, but often spur movement of vectors as they seek to avoid predation. However, a general framework to predict how species interactions affect vectors of plant pathogens, and the resulting spread of vector-borne pathogens, is lacking. Here we developed a mathematical model to assess whether interactions such as predation, competition, and mutualism affected the spread of vector-borne plant pathogens with nonpersistent or persistent transmission modes. We considered transmission mode because interactions affecting vector-host encounter rates were expected to most strongly affect nonpersistent pathogens that are transmitted with short feeding bouts; interactions that affect vector feeding duration were expected to most strongly affect persistent pathogens that require long feeding bouts for transmission. Our results show that interactions that affected vector behavior (feeding duration, vector-host encounter rates) substantially altered rates of spread for vector-borne plant pathogens, whereas those affecting vector fitness (births, deaths) had relatively small effects. These effects of species interactions were largely independent of transmission mode, except when interactions affected vector-host encounter rates, where effects were strongest for nonpersistent pathogens. Our results suggest that a better understanding of how vectors interact with other species within food webs could enhance our understanding of disease ecology.
Subject(s)
Ecology , Insect Vectors , Animals , Models, Theoretical , Plant Diseases , Predatory BehaviorABSTRACT
Although the HIV pandemic remains a global crisis, much progress has been made in implementing programmes to treat and prevent HIV infection. To guide prioritisation of efforts, the metric by which a country can declare its HIV epidemic as controlled has become increasingly relevant. Herein, we evaluate the merits of the four control criteria proposed by UNAIDS: percentage reduction in incidence over time; ratio of incidence to mortality; ratio of incidence to prevalence; and annual incidence. Using a transmission model to generate projections of demography, incidence, and mortality, we highlight potential pitfalls associated with each of the first three criteria. A definition of control based on annual incidence would provide clarity and consistency across settings.
Subject(s)
Epidemics/prevention & control , Global Health/standards , HIV Infections/epidemiology , HIV Infections/prevention & control , Benchmarking , Epidemics/statistics & numerical data , Forecasting , Global Health/trends , HIV Infections/mortality , Humans , Incidence , PrevalenceABSTRACT
Coinfecting parasites and pathogens remain a leading challenge for global public health due to their consequences for individual-level infection risk and disease progression. However, a clear understanding of the population-level consequences of coinfection is lacking. Here, we constructed a model that includes three individual-level effects of coinfection: mortality, fecundity, and transmission. We used the model to investigate how these individual-level consequences of coinfection scale up to produce population-level infection patterns. To parameterize this model, we conducted a 4-y cohort study in African buffalo to estimate the individual-level effects of coinfection with two bacterial pathogens, bovine tuberculosis (bTB) and brucellosis, across a range of demographic and environmental contexts. At the individual level, our empirical results identified bTB as a risk factor for acquiring brucellosis, but we found no association between brucellosis and the risk of acquiring bTB. Both infections were associated with reductions in survival and neither infection was associated with reductions in fecundity. The model reproduced coinfection patterns in the data and predicted opposite impacts of coinfection at individual and population scales: Whereas bTB facilitated brucellosis infection at the individual level, our model predicted the presence of brucellosis to have a strong negative impact on bTB at the population level. In modeled populations where brucellosis was present, the endemic prevalence and basic reproduction number ([Formula: see text]) of bTB were lower than in populations without brucellosis. Therefore, these results provide a data-driven example of competition between coinfecting pathogens that occurs when one pathogen facilitates secondary infections at the individual level.
Subject(s)
Brucellosis , Buffaloes/microbiology , Coinfection , Models, Biological , Tuberculosis, Bovine , Animals , Brucellosis/epidemiology , Brucellosis/microbiology , Brucellosis/transmission , Brucellosis/veterinary , Cattle , Coinfection/epidemiology , Coinfection/microbiology , Coinfection/transmission , Coinfection/veterinary , Female , Tuberculosis, Bovine/epidemiology , Tuberculosis, Bovine/microbiology , Tuberculosis, Bovine/transmissionABSTRACT
The efficacy of influenza vaccines varies from one year to the next, with efficacy during the 2017-2018 season anticipated to be lower than usual. However, the impact of low-efficacy vaccines at the population level and their optimal age-specific distribution have yet to be ascertained. Applying an optimization algorithm to a mathematical model of influenza transmission and vaccination in the United States, we determined the optimal age-specific uptake of low-efficacy vaccine that would minimize incidence, hospitalization, mortality, and disability-adjusted life-years (DALYs), respectively. We found that even relatively low-efficacy influenza vaccines can be highly impactful, particularly when vaccine uptake is optimally distributed across age groups. As vaccine efficacy declines, the optimal distribution of vaccine uptake shifts toward the elderly to minimize mortality and DALYs. Health practitioner encouragement and concerted recruitment efforts are required to achieve optimal coverage among target age groups, thereby minimizing influenza morbidity and mortality for the population overall.
Subject(s)
Influenza A virus/immunology , Influenza Vaccines/standards , Influenza, Human/economics , Influenza, Human/prevention & control , Resource Allocation/standards , Vaccination/statistics & numerical data , Adolescent , Adult , Aged , Child , Child, Preschool , Hospitalization/statistics & numerical data , Humans , Incidence , Infant , Infant, Newborn , Influenza Vaccines/administration & dosage , Influenza, Human/epidemiology , Middle Aged , Morbidity , Population Surveillance , Resource Allocation/economics , Resource Allocation/legislation & jurisprudence , Seasons , Survival Rate , United States/epidemiology , Young AdultABSTRACT
Apart from the traditional role of preventing progression from HIV to AIDS, antiretroviral drug therapy (ART) has been shown to have the additional beneï¬t of substantially reducing infectiousness in infected people, making ART potentially an important strategy in the ï¬ght against HIV. We developed a mathematical model based on the WHO's 5-stage classiï¬cation of HIV/AIDS disease progression. Our model stratiï¬es the population by disease stage, diagnosis and treatment. We used optimal control methods and data from South Africa to determine the best time-dependent treatment allocation required to minimize new infections, infection-years, deaths and cost. Our results indicated that the treatment strategy to minimize infection-years and new infections is to place emphasis on early treatment (i.e., treatment in Stage II & III), while to minimize cost and death, the emphasis should be on late treatment (i.e., Stage III & IV). Applying the optimal treatment strategy also leads to a substantial reduction in disease incidence and prevalence. The results of this study will hopefully provide some guidance for policymakers in determining how to best allocate antiretroviral drugs in order to maximize the beneï¬ts of treatment.
Subject(s)
HIV Infections/drug therapy , HIV Infections/epidemiology , HIV Infections/prevention & control , Acquired Immunodeficiency Syndrome/drug therapy , Adolescent , Adult , Anti-Retroviral Agents/therapeutic use , Antiretroviral Therapy, Highly Active , CD4 Lymphocyte Count , Disease Progression , Female , Global Health , Humans , Immunosuppression Therapy , Infectious Disease Medicine , Male , Models, Theoretical , Prevalence , Public Health , South Africa/epidemiology , Viral Load , Young AdultABSTRACT
The HIV pandemic continues to impose enormous morbidity, mortality, and economic burdens across the globe. Simultaneously, innovations in antiretroviral therapy, diagnostic approaches, and vaccine development are providing novel tools for treatment-as-prevention and prophylaxis. We developed a mathematical model to evaluate the added benefit of an HIV vaccine in the context of goals to increase rates of diagnosis, treatment, and viral suppression in 127 countries. Under status quo interventions, we predict a median of 49 million [first and third quartiles 44M, 58M] incident cases globally from 2015 to 2035. Achieving the Joint United Nations Program on HIV/AIDS 95-95-95 target was estimated to avert 25 million [20M, 33M] of these new infections, and an additional 6.3 million [4.8M, 8.7M] reduction was projected with the 2020 introduction of a 50%-efficacy vaccine gradually scaled up to 70% coverage. This added benefit of prevention through vaccination motivates imminent and ongoing clinical trials of viable candidates to realize the goal of HIV control.
Subject(s)
AIDS Vaccines/therapeutic use , HIV Infections/prevention & control , Vaccination Coverage , HIV Infections/epidemiology , Humans , United Nations , Vaccination Coverage/statistics & numerical dataABSTRACT
Marine protected areas (MPAs) are regions in the ocean where fishing is restricted or prohibited. Although several measures for MPA performance exist, here we focus on a specific one, namely the ratio of the steady state fish densities inside and outside the MPA. Several 2 patch models are proposed and analyzed mathematically. One patch represents the MPA, whereas the second patch represents the fishing ground. Fish move freely between both regions in a diffusive manner. Our main objective is to understand how fish mobility affects MPA performance. We show that MPA effectiveness decreases with fish mobility for single species models with logistic growth, and that densities inside and outside the MPA tend to equalize. This suggests that MPA performance is highest for the least mobile species. We then consider a 2 patch Lotka-Volterra predator-prey system. When one of the species moves, and the other does not, the ratio of the moving species first remains constant, and ultimately decreases with increased fish mobility, again with a tendency of equalization of the density in both regions. This suggests that MPA performance is not only highest for slow, but also for moderately mobile species. The discrepancy in MPA performance for single species models and for predator-prey models, confirms that MPA design requires an integrated, ecosystem-based approach. The mathematical approaches advocated here complement and enhance the numerical and theoretical approaches that are commonly applied to more complex models in the context of MPA design.
Subject(s)
Conservation of Natural Resources/methods , Ecosystem , Fisheries , Predatory Behavior , Animals , Fishes , Models, TheoreticalABSTRACT
BACKGROUND: As Zika virus continues to spread, decisions regarding resource allocations to control the outbreak underscore the need for a tool to weigh policies according to their cost and the health burden they could avert. For example, to combat the current Zika outbreak the US President requested the allocation of $1.8 billion from Congress in February 2016. METHODOLOGY/PRINCIPAL FINDINGS: Illustrated through an interactive tool, we evaluated how the number of Zika cases averted, the period during pregnancy in which Zika infection poses a risk of microcephaly, and probabilities of microcephaly and Guillain-Barré Syndrome (GBS) impact the cost at which an intervention is cost-effective. From Northeast Brazilian microcephaly incidence data, we estimated the probability of microcephaly in infants born to Zika-infected women (0.49% to 2.10%). We also estimated the probability of GBS arising from Zika infections in Brazil (0.02% to 0.06%) and Colombia (0.08%). We calculated that each microcephaly and GBS case incurs the loss of 29.95 DALYs and 1.25 DALYs per case, as well as direct medical costs for Latin America and the Caribbean of $91,102 and $28,818, respectively. We demonstrated the utility of our cost-effectiveness tool with examples evaluating funding commitments by Costa Rica and Brazil, the US presidential proposal, and the novel approach of genetically modified mosquitoes. Our analyses indicate that the commitments and the proposal are likely to be cost-effective, whereas the cost-effectiveness of genetically modified mosquitoes depends on the country of implementation. CONCLUSIONS/SIGNIFICANCE: Current estimates from our tool suggest that the health burden from microcephaly and GBS warrants substantial expenditures focused on Zika virus control. Our results justify the funding committed in Costa Rica and Brazil and many aspects of the budget outlined in the US president's proposal. As data continue to be collected, new parameter estimates can be customized in real-time within our user-friendly tool to provide updated estimates on cost-effectiveness of interventions and inform policy decisions in country-specific settings.
Subject(s)
Health Care Costs , Health Policy , Zika Virus Infection/economics , Zika Virus Infection/prevention & control , Aedes/genetics , Aedes/virology , Animals , Animals, Genetically Modified , Brazil/epidemiology , Caribbean Region/epidemiology , Cost of Illness , Cost-Benefit Analysis/legislation & jurisprudence , Costa Rica/epidemiology , Disease Outbreaks/economics , Disease Outbreaks/legislation & jurisprudence , Disease Outbreaks/prevention & control , Female , Health Care Costs/legislation & jurisprudence , Humans , Incidence , Infant , Microcephaly/etiology , Microcephaly/prevention & control , Microcephaly/virology , Pregnancy , Pregnancy Complications, Infectious/economics , Pregnancy Complications, Infectious/prevention & control , Pregnancy Complications, Infectious/virology , Zika Virus/isolation & purification , Zika Virus Infection/epidemiology , Zika Virus Infection/virologyABSTRACT
The 2014-2015 Ebola epidemic has been the most protracted and devastating in the history of the disease. To prevent future outbreaks on this scale, it is imperative to understand the reasons that led to eventual disease control. Here, we evaluated the shifts of Ebola dynamics at national and local scales during the epidemic in Liberia. We used a transmission model calibrated to epidemiological data between June 9 and December 31, 2014, to estimate the extent of community and hospital transmission. We found that despite varied local epidemic patterns, community transmission was reduced by 40-80% in all the counties analyzed. Our model suggests that the tapering of the epidemic was achieved through reductions in community transmission, rather than accumulation of immune individuals through asymptomatic infection and unreported cases. Although the times at which this transmission reduction occurred in the majority of the Liberian counties started before any large expansion in hospital capacity and the distribution of home protection kits, it remains difficult to associate the presence of interventions with reductions in Ebola incidence.
Subject(s)
Disease Outbreaks/statistics & numerical data , Hemorrhagic Fever, Ebola/epidemiology , Community-Acquired Infections/epidemiology , Community-Acquired Infections/transmission , Cross Infection/epidemiology , Cross Infection/transmission , Hemorrhagic Fever, Ebola/transmission , Humans , Liberia/epidemiology , Models, Statistical , Retrospective StudiesABSTRACT
Human African trypanosomiasis (HAT), transmitted by tsetse flies, has historically infected hundreds of thousands of individuals annually in sub-Saharan Africa. Over the last decade, concerted control efforts have reduced reported cases to below 10,000 annually, bringing complete elimination within reach. A potential technology to eliminate HAT involves rendering the flies resistant to trypanosome infection. This approach can be achieved through the introduction of transgenic Sodalis symbiotic bacteria that have been modified to produce a trypanocide, and propagated via Wolbachia symbionts, which confer a reproductive advantage to the paratransgenic tsetse. However, the population dynamics of these symbionts within tsetse flies have not yet been evaluated. Specifically, the key factors that determine the effectiveness of paratransgenesis have yet to be quantified. To identify the impact of these determinants on T.b. gambiense and T.b. rhodesiense transmission, we developed a mathematical model of trypanosome transmission that incorporates tsetse and symbiont population dynamics. We found that fecundity and mortality penalties associated with Wolbachia or recombinant Sodalis colonization, probabilities of vertical transmission, and tsetse migration rates are fundamental to the feasibility of HAT elimination. For example, we determined that HAT elimination could be sustained over 25 years when Wolbachia colonization minimally impacted fecundity or mortality, and when the probability of recombinant Sodalis vertical transmission exceeded 99.9%. We also found that for a narrow range of recombinant Sodalis vertical transmission probability (99.9-90.6% for T.b. gambiense and 99.9-85.8% for T.b. rhodesiense), cumulative HAT incidence was reduced between 30% and 1% for T.b. gambiense and between 21% and 3% for T.b. rhodesiense, although elimination was not predicted. Our findings indicate that fitness and mortality penalties associated with paratransgenic symbionts, as well as tsetse migration rates, are instrumental to HAT elimination, and should be a key focus in the development of paratransgenic symbionts.
Subject(s)
Disease Eradication , Enterobacteriaceae/growth & development , Symbiosis , Trypanosoma brucei brucei/growth & development , Trypanosomiasis, African/prevention & control , Tsetse Flies/microbiology , Wolbachia/physiology , Africa South of the Sahara , Animals , Animals, Genetically Modified , Communicable Disease Control/methods , Disease Transmission, Infectious/prevention & control , Enterobacteriaceae/genetics , Entomology/methods , Humans , Models, Theoretical , Population Dynamics , Trypanosomiasis, African/epidemiology , Trypanosomiasis, African/transmissionABSTRACT
BACKGROUND: Eastern equine encephalitis (EEE) virus (Togaviridae, Alphavirus) is a highly pathogenic mosquito-borne zoonosis that is responsible for occasional outbreaks of severe disease in humans and equines, resulting in high mortality and neurological impairment in most survivors. In the past, human disease outbreaks in the northeastern U.S. have occurred intermittently with no apparent pattern; however, during the last decade we have witnessed recurring annual emergence where EEE virus activity had been historically rare, and expansion into northern New England where the virus had been previously unknown. In the northeastern U.S., EEE virus is maintained in an enzootic cycle involving the ornithophagic mosquito, Culiseta melanura, and wild passerine (perching) birds in freshwater hardwood swamps. However, the identity of key avian species that serve as principal virus reservoir and amplification hosts has not been established. The efficiency with which pathogen transmission occurs within an avian community is largely determined by the relative reservoir competence of each species and by ecological factors that influence contact rates between these avian hosts and mosquito vectors. METHODOLOGY AND PRINCIPLE FINDINGS: Contacts between vector mosquitoes and potential avian hosts may be directly quantified by analyzing the blood meal contents of field-collected specimens. We used PCR-based molecular methods and direct sequencing of the mitochondrial cytochrome b gene for profiling of blood meals in Cs. melanura, in an effort to quantify its feeding behavior on specific vertebrate hosts, and to infer epidemiologic implications in four historic EEE virus foci in the northeastern U.S. Avian point count surveys were conducted to determine spatiotemporal host community composition. Of 1,127 blood meals successfully identified to species level, >99% of blood meals were from 65 avian hosts in 27 families and 11 orders, and only seven were from mammalian hosts representing three species. We developed an empirically informed mathematical model for EEE virus transmission using Cs. melanura abundance and preferred and non-preferred avian hosts. To our knowledge this is the first mathematical model for EEE virus, a pathogen with many potential hosts, in the northeastern U.S. We measured strong feeding preferences for a number of avian species based on the proportion of mosquito blood meals identified from these bird species in relation to their observed frequencies. These included: American Robin, Tufted Titmouse, Common Grackle, Wood Thrush, Chipping Sparrow, Black-capped Chickadee, Northern Cardinal, and Warbling Vireo. We found that these bird species, most notably Wood Thrush, play a dominant role in supporting EEE virus amplification. It is also noteworthy that the competence of some of the aforementioned avian species for EEE virus has not been established. Our findings indicate that heterogeneity induced by mosquito host preference, is a key mediator of the epizootic transmission of vector-borne pathogens. CONCLUSION AND SIGNIFICANCE: Detailed knowledge of the vector-host interactions of mosquito populations in nature is essential for evaluating their vectorial capacity and for assessing the role of individual vertebrates as reservoir hosts involved in the maintenance and amplification of zoonotic agents of human diseases. Our study clarifies the host associations of Cs. melanura in four EEE virus foci in the northeastern U.S., identifies vector host preferences as the most important transmission parameter, and quantifies the contribution of preference-induced contact heterogeneity to enzootic transmission. Our study identifies Wood Thrush, American Robin and a few avian species that may serve as superspreaders of EEE virus. Our study elucidates spatiotemporal host species utilization by Cs. melanura in relation to avian host community. This research provides a basis to better understand the involvement of Cs. melanura and avian hosts in the transmission and ecology of EEE virus and the risk of human infection in virus foci.
Subject(s)
Birds/blood , Culicidae/physiology , Encephalitis Virus, Eastern Equine/physiology , Encephalomyelitis, Eastern Equine/veterinary , Insect Vectors/physiology , Animal Distribution , Animals , Birds/classification , Connecticut/epidemiology , Disease Reservoirs , Ecosystem , Encephalomyelitis, Eastern Equine/epidemiology , Encephalomyelitis, Eastern Equine/virology , Encephalomyelitis, Equine/epidemiology , Encephalomyelitis, Equine/veterinary , Encephalomyelitis, Equine/virology , Feeding Behavior , Female , HumansABSTRACT
Uptake of vaccination against seasonal influenza is suboptimal in most countries, and campaigns to promote vaccination may be weakened by clustering of opinions and decisions not to vaccinate. This clustering can occur at myriad interacting levels: within households, social circles, and schools. Given that influenza is more likely to be transmitted to a household contact than any other contact, clustering of vaccination decisions is arguably most problematic at the household level. We conducted an international survey study to determine whether household members across different cultures offered direct advice to each other regarding influenza vaccination and whether this advice was associated with vaccination decisions. The survey revealed that household members across the world advise one another to vaccinate, although to varying degrees, and that advice correlates with an increase in vaccination uptake. In addition, respondents in Japan, China, and the United States were less likely to offer advice to older adults than to the young, despite older adults' being the target age group for vaccination in both Far Eastern countries. Furthermore, advice was not primarily directed to household members within the age groups advised to vaccinate by national health policies. In Japan, advice was offered more to ages outside of the policy guidelines than inside. Harnessing the influence of household members may offer a novel strategy to improve vaccination coverage across cultures worldwide.
Subject(s)
Cross-Cultural Comparison , Decision Making , Family Characteristics , Influenza Vaccines/administration & dosage , Vaccination , Female , Humans , Internationality , Male , Surveys and QuestionnairesABSTRACT
Free-roaming horse (Equus caballus) management is a complex issue incorporating social, economic, emotional, political, and environmental factors. Currently, few proven field techniques exist for managing free-roaming horse population growth, which can reach 20-25% annually. Although there are several strategies available for sterilizing mares when managing free-roaming horse populations, surgical vasectomy is the only method used in the field for stallions. Some managers believe that surgically vasectomizing dominant stallions would have significant effects on reducing horse populations. However, sterilizing only dominant harem stallions results in a relatively modest reduction in population growth as substantial reproduction may occur even when 100% of the dominant harem stallions are sterilized if other males perform as little as 10% of the breeding. The overall goal of the current project was to evaluate the efficacy of a novel nonsurgical method for sterilizing free-roaming horses (chemical vasectomy). In September of 2013, stallions that had been previously surgically vasectomized (SURG, n = 25), previously chemically vasectomized (CHEM, n = 16), or untreated (CONT, n = 32) were captured and surgically castrated in preparation for adoption. When comparing both sterilization methods to CONT, serum testosterone and estrone sulfate concentrations did not differ (P > 0.05), suggesting that these methods for sterilizing free-roaming stallions would not disrupt herd social hierarchy. However, similar to the CONT, all CHEM stallions had sperm present within the vas deferens seminal fluid samples. CHEM stallions had more morphologically abnormal sperm than did CONT stallions but it is not known if this affected the actual fertility. Additional research is needed using alternative sclerosing agents for chemical vasectomy in free-roaming horse populations.
Subject(s)
Chlorhexidine/pharmacology , Horses , Testis/physiology , Vasectomy/veterinary , Animals , Animals, Wild , Contraception/methods , Contraception/veterinary , Male , Sclerosing Solutions/pharmacology , Semen , Vasectomy/methodsABSTRACT
Traditional differential equation models of disease transmission are often used to predict disease trajectories and evaluate the effectiveness of alternative intervention strategies. However, such models cannot account explicitly for probabilistic events, such as those that dominate dynamics when disease prevalence is low during the elimination and re-emergence phases of an outbreak. To account for the dynamics at low prevalence, i.e. the elimination and risk of disease re-emergence, without the added analytical and computational complexity of a stochastic model, we develop a novel application of control theory. We apply our approach to analyze historical data of measles elimination and re-emergence in Iceland from 1923 to 1938, predicting the temporal trajectory of local measles elimination and re-emerge as a result of disease migration from Copenhagen, Denmark.
Subject(s)
Disease Eradication , Measles/epidemiology , Models, Biological , Basic Reproduction Number , Humans , Iceland , Measles/transmission , Time FactorsABSTRACT
BACKGROUND: In the weeks following the first imported case of Ebola in the U. S. on September 29, 2014, coverage of the very limited outbreak dominated the news media, in a manner quite disproportionate to the actual threat to national public health; by the end of October, 2014, there were only four laboratory confirmed cases of Ebola in the entire nation. Public interest in these events was high, as reflected in the millions of Ebola-related Internet searches and tweets performed in the month following the first confirmed case. Use of trending Internet searches and tweets has been proposed in the past for real-time prediction of outbreaks (a field referred to as "digital epidemiology"), but accounting for the biases of public panic has been problematic. In the case of the limited U. S. Ebola outbreak, we know that the Ebola-related searches and tweets originating the U. S. during the outbreak were due only to public interest or panic, providing an unprecedented means to determine how these dynamics affect such data, and how news media may be driving these trends. METHODOLOGY: We examine daily Ebola-related Internet search and Twitter data in the U. S. during the six week period ending Oct 31, 2014. TV news coverage data were obtained from the daily number of Ebola-related news videos appearing on two major news networks. We fit the parameters of a mathematical contagion model to the data to determine if the news coverage was a significant factor in the temporal patterns in Ebola-related Internet and Twitter data. CONCLUSIONS: We find significant evidence of contagion, with each Ebola-related news video inspiring tens of thousands of Ebola-related tweets and Internet searches. Between 65% to 76% of the variance in all samples is described by the news media contagion model.
Subject(s)
Hemorrhagic Fever, Ebola/epidemiology , Mass Media , Disease Outbreaks , Fear , Hemorrhagic Fever, Ebola/diagnosis , Humans , Information Dissemination , Social MediaABSTRACT
The ongoing Ebola outbreak poses an alarming risk to the countries of West Africa and beyond. To assess the effectiveness of containment strategies, we developed a stochastic model of Ebola transmission between and within the general community, hospitals, and funerals, calibrated to incidence data from Liberia. We find that a combined approach of case isolation, contact-tracing with quarantine, and sanitary funeral practices must be implemented with utmost urgency in order to reverse the growth of the outbreak. As of 19 September, under status quo, our model predicts that the epidemic will continue to spread, generating a predicted 224 (134 to 358) daily cases by 1 December, 280 (184 to 441) by 15 December, and 348 (249 to 545) by 30 December.
Subject(s)
Containment of Biohazards/methods , Hemorrhagic Fever, Ebola/epidemiology , Hemorrhagic Fever, Ebola/prevention & control , Africa, Western/epidemiology , Humans , Models, TheoreticalABSTRACT
Transitional cell carcinoma (TCC), the most common cancer of the urinary bladder in dogs, is usually diagnosed at an advanced disease stage with limited response to chemotherapy. Commercial screening tests lack specificity and current diagnostic procedures are invasive. A proof of concept pilot project for analyzing the canine urinary proteome as a noninvasive diagnostic tool for TCC identification was conducted. Urine was collected from 12 dogs in three cohorts (healthy, urinary tract infection, TCC) and analyzed using liquid chromatography tandem mass spectrometry. The presence of four proteins (macrophage capping protein, peroxiredoxin 5, heterogeneous nuclear ribonucleoproteins A2/B, and apolipoprotein A1) was confirmed via immunoblot. Of the total 379 proteins identified, 96 were unique to the TCC group. A statistical model, designed to evaluate the accuracy of this multiplex biomarker approach for diagnosis of TCC, predicted the presence of disease with 90% accuracy.