scholarly journals What Does Tolerance Mean for Animal Disease Dynamics When Pathology Enhances Transmission?

2019 ◽  
Vol 59 (5) ◽  
pp. 1220-1230 ◽  
Author(s):  
Amberleigh E Henschen ◽  
James S Adelman
Keyword(s):  
Graphical Models ◽  
Tissue Level ◽  
Pathogen Transmission ◽  
Infectious Period ◽  
Disease Dynamics ◽  
Animal Populations ◽  
Damage Repair ◽  
Host Competence ◽  
And Control ◽  
Damage Avoidance

Abstract Host competence, or how well an individual transmits pathogens, varies substantially within and among animal populations. As this variation can alter the course of epidemics and epizootics, revealing its underlying causes will help predict and control the spread of disease. One host trait that could drive heterogeneity in competence is host tolerance, which minimizes fitness losses during infection without decreasing pathogen load. In many cases, tolerance should increase competence by extending infectious periods and enabling behaviors that facilitate contact among hosts. However, we argue that the links between tolerance and competence are more varied. Specifically, the different physiological and behavioral mechanisms by which hosts achieve tolerance should have a range of effects on competence, enhancing the ability to transmit pathogens in some circumstances and impeding it in others. Because tissue-based pathology (damage) that reduces host fitness is often critical for pathogen transmission, we focus on two mechanisms that can underlie tolerance at the tissue level: damage-avoidance and damage-repair. As damage-avoidance reduces transmission-enhancing pathology, this mechanism is likely to decrease host competence and pathogen transmission. In contrast, damage-repair does not prevent transmission-relevant pathology from occurring. Rather, damage-repair provides new, healthy tissues that pathogens can exploit, likely extending the infectious period and increasing host competence. We explore these concepts through graphical models and present three disease systems in which damage-avoidance and damage-repair alter host competence in the predicted directions. Finally, we suggest that by incorporating these links, future theoretical studies could provide new insights into infectious disease dynamics and host–pathogen coevolution.

scholarly journals Challenges and Opportunities Developing Mathematical Models of Shared Pathogens of Domestic and Wild Animals

2018 ◽  
Vol 5 (4) ◽  
pp. 92 ◽  
Author(s):  
Kathryn Huyvaert ◽  
Robin Russell ◽  
Kelly Patyk ◽  
Meggan Craft ◽  
Paul Cross ◽  
...  
Keyword(s):  
Mathematical Models ◽  
Domestic Animals ◽  
Domestic Animal ◽  
Pathogen Transmission ◽  
Management Actions ◽  
Animal Populations ◽  
Challenges And Opportunities ◽  
Conservation Concern ◽  
Transmission Pathways ◽  
And Control

Diseases that affect both wild and domestic animals can be particularly difficult to prevent, predict, mitigate, and control. Such multi-host diseases can have devastating economic impacts on domestic animal producers and can present significant challenges to wildlife populations, particularly for populations of conservation concern. Few mathematical models exist that capture the complexities of these multi-host pathogens, yet the development of such models would allow us to estimate and compare the potential effectiveness of management actions for mitigating or suppressing disease in wildlife and/or livestock host populations. We conducted a workshop in March 2014 to identify the challenges associated with developing models of pathogen transmission across the wildlife-livestock interface. The development of mathematical models of pathogen transmission at this interface is hampered by the difficulties associated with describing the host-pathogen systems, including: (1) the identity of wildlife hosts, their distributions, and movement patterns; (2) the pathogen transmission pathways between wildlife and domestic animals; (3) the effects of the disease and concomitant mitigation efforts on wild and domestic animal populations; and (4) barriers to communication between sectors. To promote the development of mathematical models of transmission at this interface, we recommend further integration of modern quantitative techniques and improvement of communication among wildlife biologists, mathematical modelers, veterinary medicine professionals, producers, and other stakeholders concerned with the consequences of pathogen transmission at this important, yet poorly understood, interface.

scholarly journals A mechanistic, stigmergy model of territory formation in asocial animals: Territorial behavior can dampen disease prevalence but increase persistence

2019 ◽  
Author(s):  
Lauren A. White ◽  
Sue VandeWoude ◽  
Meggan E. Craft
Keyword(s):  
Disease Ecology ◽  
Scent Marking ◽  
Movement Ecology ◽  
Pathogen Transmission ◽  
Disease Spread ◽  
Movement Behavior ◽  
Infectious Period ◽  
Trade Offs ◽  
Animal Populations ◽  
Territory Formation

AbstractMechanistic portrayals of how animals form and maintain territories remain rare, and as a discipline, collective movement ecology has tended to focus on synergistic (e.g., migration, shoaling) rather than agonistic or territorial interactions. Here we ask how dynamic territory formation and maintenance might contribute to disease dynamics in an asocial territorial animal for an indirectly transmitted pathogen. We developed a mechanistic individual-based model where stigmergy—the deposition of signals into the environment (e.g., scent marking, scraping)—dictates not only local movement choices and long-term territory formation, but also the risk of pathogen transmission. Based on a variable importance analysis, the length of the infectious period was the single most important variable in predicting outbreak success, maximum prevalence, and outbreak duration. Population size and rate of pathogen decay were also key predictors. We found that territoriality best reduced maximum prevalence in conditions where we would otherwise expect outbreaks to be most successful: slower recovery rates (i.e., longer infectious periods) and higher conspecific densities. However, at high enough densities, outbreak duration became considerably more variable. Our findings therefore support a limited version of the “territoriality benefits” hypothesis—where reduced home range overlap leads to reduced opportunities for pathogen transmission, but with the caveat that reduction in outbreak severity may increase the likelihood of pathogen persistence. For longer infectious periods and higher host densities, key trade-offs emerged between the strength of pathogen load, strength of the stigmergy cue, and the rate at which those two quantities decayed; this finding raises interesting questions about the evolutionary nature of these competing processes and the role of possible feedbacks between parasitism and territoriality. This work also highlights the importance of considering social cues as part of the movement landscape in order to improve our understanding of the consequences of individual behaviors on population level outcomes.Author summaryMaking decisions about conservation and disease management relies on our understanding of what allows animal populations to be successful. However, movement ecology, as a field, tends to focus on how animals respond to their abiotic environment. Similarly, disease ecology often focuses on the social behavior of animals without accounting for their individual movement patterns. We developed a simulation model that bridges these two fields by allowing hosts to inform their movement based on the past trajectories of other hosts. As hosts navigate their environment, they leave behind a scent trail while avoiding the scent trails of other individuals. We wanted to know if this means of territory formation could heighten or dampen disease spread when infectious hosts leave pathogens in their wake. We found that territoriality could inhibit disease spread under conditions that we would normally expect pathogens to be most successful: where there are many hosts on the landscape and hosts stay infectious for longer. This work points to how incorporating movement behavior into disease models can provide improved understanding of how diseases spread in wildlife populations; such understanding is particularly important in the face of combatting ongoing and emerging infectious diseases.

Randomized Prospective Study of the Impact of Three Needleless Intravenous Systems on Needlestick Injury Rates

1996 ◽  
Vol 17 (12) ◽  
pp. 803-808
Author(s):  
Paul B. L'Ecuyer ◽  
Elizabeth Owens Schwab ◽  
Elizabeth Iademarco ◽  
Norma Barr ◽  
Elizabeth A. Aton ◽  
...  
Keyword(s):  
Controlled Trial ◽  
Tertiary Care ◽  
Control Area ◽  
Needlestick Injury ◽  
Pathogen Transmission ◽  
Needlestick Injuries ◽  
Injury Rates ◽  
Rate Ratios ◽  
And Control ◽  
The Impact

AbstractObjective:To determine the impact of three needleless intravenous systems on needlestick injury rates.Design:Randomized controlled trial.Setting:1,000-bed tertiary-care Midwestern hospital.Participants:Nursing personnel from general medical, general surgical, and intensive-care units.Interventions:From June 1992 through March 1994, a metal blunt cannula (MBC), two-way valve (2-way), and plastic blunt cannula (PBC) were introduced into three study areas, and needlestick injury rates were compared to three control areas using traditional needled devices.Results:24 and 29 needlestick injuries were reported in study and control areas. Intravenous-therapy-related injuries comprised 45.8% and 57.1% of injuries in each area. Thirty-seven percent and 20.7% of study and control area needlestick injuries were considered to pose a high risk of bloodborne infection. The 2-way group had similar rates of total and intravenous-related needlestick injuries compared to control groups. The PBC group had lower rates of total and intravenous-related needlestick injuries per 1,000 patient-days (rate ratios [RR], 0.32 and 0.24; 95°% confidence intervals [CI95], 0.12-0.81 and 0.09-0.61;P=.02 andP=.003, respectively) and per 1,000 productive hours worked (RR, 0.11 and 0.08; CI95, 0.01-0.92 and 0.010.69;P=.03 andP=.005, respectively) compared to controls.Conclusions:Needlestick injuries continued in study areas despite the introduction of needleless devices, and risks of bloodborne pathogen transmission were similar to control areas. The PBC device group noted lower rates of needlestick injuries compared to controls, but there were problems with product acceptance, correct product use, and continued traditional device use in study areas. Low needlestick injury rates make interpretations difficult. Further studies of safety devices are needed and should attempt greater control of worker behavior to aid interpretation.

scholarly journals Investigation of the spread of brucellosis among human and animal populations in southeastern Bulgaria, 2007

2009 ◽  
Vol 14 (17) ◽  
Author(s):  
V Tzaneva ◽  
S Ivanova ◽  
M Georgieva ◽  
E Tasheva
Keyword(s):  
Dairy Products ◽  
Domestic Animals ◽  
Effective Prevention ◽  
Health Authorities ◽  
Animal Populations ◽  
Control Programmes ◽  
Public Health Authorities ◽  
Spread Of Infection ◽  
And Control ◽  
Positive Results

Three human cases of brucellosis were reported in summer 2007 in the region of Haskovo in southeastern Bulgaria. Subsequently, the regional veterinary and public health authorities carried out investigations to determine the spread of infection in domestic animals and in the human population. As a result, over 90,000 animals were tested, and 410 were found infected with brucellosis. The screening of 561 people believed to have been at risk of infection yielded 47 positive results. The majority of these persons had direct contact with domestic animals or had consumed unpasteurised dairy products. The investigations revealed evidence of disease among animals in the region and a considerable risk to humans, thus emphasising the need for effective prevention and control programmes.

Changes in small native animal populations following control of European rabbits (Oryctolagus cuniculus) by warren ripping in the Australian arid zone

2019 ◽  
Vol 46 (4) ◽  
pp. 343 ◽  
Author(s):  
P. Elsworth ◽  
D. Berman ◽  
M. Brennan
Keyword(s):  
Arid Zone ◽  
Control Program ◽  
Fold Increase ◽  
Food Sources ◽  
Pitfall Trapping ◽  
Animal Populations ◽  
Introduced Predators ◽  
Paired Control ◽  
European Rabbits ◽  
And Control

Context European rabbits have a great impact on native vegetation and small vertebrates in Australia. Rabbits consume vegetation and promote invasive plants and invasive predators, and compete directly and indirectly with native animals suppressing those populations. Aims We explored the changes in small native vertebrates and invertebrates following the removal of rabbits. Methods Warren ripping was undertaken on a property in south-western Queensland at four sites and the results of pitfall trapping were compared with four nearby paired control sites. Invertebrates and small mammals were counted in pitfall traps, and bird surveys were conducted in all treatment and control sites. Key results Following a rabbit-control program, we observed a four-fold increase in the number of dunnarts trapped in treatment plots, whereas no change was observed in control plots. The spring following the rabbit-control program also saw an increase in some lizards in treatment plots. Conclusions The presence of rabbits in arid-zone Australia can suppress native animal populations. Implications Many species of small native mammals and lizards rely on food sources that fluctuate greatly with environmental conditions. The presence of rabbits altering the landscape, supporting introduced predators, reducing vegetation and, therefore, insects, adds increased pressure for insectivorous species. Rabbit control through warren ripping in arid-zone Australia is an effective method to reduce rabbit numbers, and allowed for an increase in small vertebrates in treated areas.

scholarly journals Disease outbreak thresholds emerge from interactions between movement behavior, landscape structure, and epidemiology

2018 ◽  
Vol 115 (28) ◽  
pp. 7374-7379 ◽  
Author(s):  
Lauren A. White ◽  
James D. Forester ◽  
Meggan E. Craft
Keyword(s):  
Spatial Heterogeneity ◽  
Landscape Structure ◽  
Spatial Organization ◽  
Complex Disease ◽  
Animal Movement ◽  
Pathogen Transmission ◽  
Movement Behavior ◽  
Disease Dynamics ◽  
Conspecific Density ◽  
Pathogen Persistence

Disease models have provided conflicting evidence as to whether spatial heterogeneity promotes or impedes pathogen persistence. Moreover, there has been limited theoretical investigation into how animal movement behavior interacts with the spatial organization of resources (e.g., clustered, random, uniform) across a landscape to affect infectious disease dynamics. Importantly, spatial heterogeneity of resources can sometimes lead to nonlinear or counterintuitive outcomes depending on the host and pathogen system. There is a clear need to develop a general theoretical framework that could be used to create testable predictions for specific host–pathogen systems. Here, we develop an individual-based model integrated with movement ecology approaches to investigate how host movement behaviors interact with landscape heterogeneity (in the form of various levels of resource abundance and clustering) to affect pathogen dynamics. For most of the parameter space, our results support the counterintuitive idea that fragmentation promotes pathogen persistence, but this finding was largely dependent on perceptual range of the host, conspecific density, and recovery rate. For simulations with high conspecific density, slower recovery rates, and larger perceptual ranges, more complex disease dynamics emerged, and the most fragmented landscapes were not necessarily the most conducive to outbreaks or pathogen persistence. These results point to the importance of interactions between landscape structure, individual movement behavior, and pathogen transmission for predicting and understanding disease dynamics.

scholarly journals Ungulate use of locally infectious zones in a re-emerging anthrax risk area

2020 ◽  
Vol 7 (10) ◽  
pp. 200246 ◽  
Author(s):  
Morgan A. Walker ◽  
Maria Uribasterra ◽  
Valpa Asher ◽  
José Miguel Ponciano ◽  
Wayne M. Getz ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Control Strategies ◽  
Pathogen Transmission ◽  
Camera Traps ◽  
Risk Area ◽  
Southwestern Montana ◽  
Increased Risk ◽  
Anthrax Spores ◽  
Causative Bacterium ◽  
And Control

Environmentally mediated indirect pathogen transmission is linked to host movement and foraging in areas where pathogens are maintained in the environment. In the case of anthrax, spores of the causative bacterium Bacillus anthracis are released into the environment following host death and create locally infectious zones (LIZs) around carcass sites; by grazing at LIZs, herbivores are potentially exposed to spores. Here, we used camera traps to assess how ungulate species use carcass sites in southwestern Montana and evaluated how these behaviours may promote indirect anthrax transmission, thus providing, to our knowledge, the first detailed documentation and study of the fine-scale mechanisms underlying foraging-based disease transmission in this ecosystem. We found that carcasses at LIZs significantly increased aboveground biomass of vegetation and concentrations of sodium and phosphorus, potentially making these sites more appealing to grazers. Host behavioural responses to LIZs varied depending on species, sex, season and carcass age; but, overall, our results demonstrated that carcasses or carcass sites serve as an attractant to herbivores in this system. Attraction to LIZs probably represents an increased risk of exposure to B. anthracis and, consequently, increased anthrax transmission rates. Accordingly, continued anthrax surveillance and control strategies are critical in this system.

Prevention and control strategies for ticks and pathogen transmission

2015 ◽  
Vol 34 (1) ◽  
pp. 249-264 ◽  
Author(s):  
FUENTE J. DE LA FUENTE ◽  
K.M. KOCAN ◽  
M. CONTRERAS
Keyword(s):  
Prevention And Control ◽  
Control Strategies ◽  
Pathogen Transmission ◽  
And Control

scholarly journals Network-based vaccination improves prospects for disease control in wild chimpanzees

2014 ◽  
Vol 11 (97) ◽  
pp. 20140349 ◽  
Author(s):  
Julie Rushmore ◽  
Damien Caillaud ◽  
Richard J. Hall ◽  
Rebecca M. Stumpf ◽  
Lauren Ancel Meyers ◽  
...  
Keyword(s):  
Large Scale ◽  
Vaccination Strategy ◽  
Pathogen Transmission ◽  
Wild Chimpanzee ◽  
Contact Rates ◽  
Individual Traits ◽  
Pathogen Control ◽  
Wildlife Populations ◽  
And Control ◽  
Biological Differences

Many endangered wildlife populations are vulnerable to infectious diseases for which vaccines exist; yet, pragmatic considerations often preclude large-scale vaccination efforts. These barriers could be reduced by focusing on individuals with the highest contact rates. However, the question then becomes whether targeted vaccination is sufficient to prevent large outbreaks. To evaluate the efficacy of targeted wildlife vaccinations, we simulate pathogen transmission and control on monthly association networks informed by behavioural data from a wild chimpanzee community (Kanyawara N = 37, Kibale National Park, Uganda). Despite considerable variation across monthly networks, our simulations indicate that targeting the most connected individuals can prevent large outbreaks with up to 35% fewer vaccines than random vaccination. Transmission heterogeneities might be attributed to biological differences among individuals (e.g. sex, age, dominance and family size). Thus, we also evaluate the effectiveness of a trait-based vaccination strategy, as trait data are often easier to collect than interaction data. Our simulations indicate that a trait-based strategy can prevent large outbreaks with up to 18% fewer vaccines than random vaccination, demonstrating that individual traits can serve as effective estimates of connectivity. Overall, these results suggest that fine-scale behavioural data can help optimize pathogen control efforts for endangered wildlife.

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