Dilution effect and identity effect by wildlife in the persistence and recurrence of bovine tuberculosis

Parasitology ◽  
2014 ◽  
Vol 141 (7) ◽  
pp. 981-987 ◽  
Author(s):  
Z. Y. X. HUANG ◽  
C. XU ◽  
F. VAN LANGEVELDE ◽  
H. H. T. PRINS ◽  
K. BEN JEBARA ◽  
...  
Keyword(s):  
Risk Factors ◽  
Disease Transmission ◽  
Bovine Tuberculosis ◽  
Disease Risk ◽  
Control Strategies ◽  
Dilution Effect ◽  
Effective Control ◽  
African Buffalo ◽  
Mammal Species ◽  
Positive Interaction

SUMMARYCurrent theories on disease-diversity relationships predict a strong influence of host richness on disease transmission. In addition, identity effect, caused by the occurrence of particular species, can also modify disease risk. We tested the richness effect and the identity effects of mammal species on bovine tuberculosis (bTB), based on the regional bTB outbreak data in cattle from 2005–2010 in Africa. Besides, we also tested which other factors were associated with the regional bTB persistence and recurrence in cattle. Our results suggested a dilution effect, where higher mammal species richness (MSR) was associated with reduced probabilities of bTB persistence and recurrence in interaction with cattle density. African buffalo had a positive effect on bTB recurrence and a positive interaction effect with cattle density on bTB persistence, indicating an additive positive identity effect of buffalo. The presence of greater kudu had no effect on bTB recurrence or bTB persistence. Climatic variables only act as risk factors for bTB persistence. In summary, our study identified both a dilution effect and identity effect of wildlife and showed that bTB persistence and recurrence were correlated with different sets of risk factors. These results are relevant for more effective control strategies and better targeted surveillance measures in bTB.

scholarly journals Dilution effect in bovine tuberculosis: risk factors for regional disease occurrence in Africa

2013 ◽  
Vol 280 (1765) ◽  
pp. 20130624 ◽  
Author(s):  
Zheng Y. X. Huang ◽  
Willem F. de Boer ◽  
Frank van Langevelde ◽  
Chi Xu ◽  
Karim Ben Jebara ◽  
...  
Keyword(s):  
Bovine Tuberculosis ◽  
Disease Risk ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Single Species ◽  
Economic Losses ◽  
African Buffalo ◽  
Mammal Species ◽  
Disease Occurrence ◽  
Regional Disease

Changes in host diversity have been postulated to influence the risk of infectious diseases, including both dilution and amplification effects. The dilution effect refers to a negative relationship between biodiversity and disease risk, whereas the amplification effect occurs when biodiversity increases disease risk. We tested these effects with an influential disease, bovine tuberculosis (BTB), which is widespread in many countries, causing severe economic losses. Based on the BTB outbreak data in cattle from 2005 to 2010, we also tested, using generalized linear mixed models, which other factors were associated with the regional BTB presence in cattle in Africa. The interdependencies of predictors and their correlations with BTB presence were examined using path analysis. Our results suggested a dilution effect, where increased mammal species richness was associated with reduced probability of BTB presence after adjustment for cattle density. In addition, our results also suggested that areas with BTB infection in the preceding year, higher cattle density and larger percentage of area occupied by African buffalo were more likely to report BTB outbreaks. Climatic variables only indirectly influenced the risk of BTB presence through their effects on cattle density and wildlife distribution. Since most studies investigating the role of wildlife species on BTB transmission only involve single-species analysis, more efforts are needed to better understand the effect of the structure of wildlife communities on BTB dynamics.

scholarly journals Methods to infer transmission risk factors in complex outbreak data

2011 ◽  
Vol 9 (68) ◽  
pp. 456-469 ◽  
Author(s):  
Simon Cauchemez ◽  
Neil M. Ferguson
Keyword(s):  
Risk Factors ◽  
Missing Data ◽  
Disease Transmission ◽  
Control Strategies ◽  
Model Fitting ◽  
Structured Populations ◽  
Transmission Risk ◽  
Effective Control ◽  
Reconstruction Methods ◽  
History Of

Data collected during outbreaks are essential to better understand infectious disease transmission and design effective control strategies. But analysis of such data is challenging owing to the dependency between observations that is typically observed in an outbreak and to missing data. In this paper, we discuss strategies to tackle some of the ongoing challenges in the analysis of outbreak data. We present a relatively generic statistical model for the estimation of transmission risk factors, and discuss algorithms to estimate its parameters for different levels of missing data. We look at the problem of computational times for relatively large datasets and show how they can be reduced by appropriate use of discretization, sufficient statistics and some simple assumptions on the natural history of the disease. We also discuss approaches to integrate parametric model fitting and tree reconstruction methods in coherent statistical analyses. The methods are tested on both real and simulated datasets of large outbreaks in structured populations.

Effect of host diversity and species assemblage composition on bovine tuberculosis (bTB) risk in Ethiopian cattle

Parasitology ◽  
2017 ◽  
Vol 144 (6) ◽  
pp. 783-792 ◽  
Author(s):  
DEJENE W. SINTAYEHU ◽  
IGNAS M. A. HEITKÖNIG ◽  
HERBERT H. T. PRINS ◽  
ZEWDU K. TESSEMA ◽  
WILLEM F. DE BOER
Keyword(s):  
Species Diversity ◽  
Habitat Use ◽  
Bovine Tuberculosis ◽  
Disease Risk ◽  
Control Strategies ◽  
Dilution Effect ◽  
Tuberculin Test ◽  
Diversity Indices ◽  
Species Identity ◽  
Greater Kudu

SUMMARYCurrent theories on diversity–disease relationships describe host species diversity and species identity as important factors influencing disease risk, either diluting or amplifying disease prevalence in a community. Whereas the simple term ‘diversity’ embodies a set of animal community characteristics, it is not clear how different measures of species diversity are correlated with disease risk. We therefore tested the effects of species richness, Pielou's evenness and Shannon's diversity on bovine tuberculosis (bTB) risk in cattle in the Afar Region and Awash National Park between November 2013 and April 2015. We also analysed the identity effect of a particular species and the effect of host habitat use overlap on bTB risk. We used the comparative intradermal tuberculin test to assess the number of bTB-infected cattle. Our results suggested a dilution effect through species evenness. We found that the identity effect of greater kudu – a maintenance host – confounded the dilution effect of species diversity on bTB risk. bTB infection was positively correlated with habitat use overlap between greater kudu and cattle. Different diversity indices have to be considered together for assessing diversity–disease relationships, for understanding the underlying causal mechanisms. We posit that unpacking diversity metrics is also relevant for formulating disease control strategies to manage cattle in ecosystems characterized by seasonally limited resources and intense wildlife–livestock interactions.

scholarly journals Global Stability and Optimal Control of Dengue with Two Coexisting Virus Serotypes

MATEMATIKA ◽  
2019 ◽  
Vol 35 (4) ◽  
pp. 149-170
Author(s):  
Afeez Abidemi ◽  
Rohanin Ahmad ◽  
Nur Arina Bazilah Aziz
Keyword(s):  
Optimal Control ◽  
Global Stability ◽  
Disease Transmission ◽  
Deterministic Model ◽  
Control Strategies ◽  
Equilibrium Points ◽  
Effective Control ◽  
Asymptotically Stable ◽  
Globally Asymptotically Stable ◽  
Boundary Equilibrium

This study presents a two-strain deterministic model which incorporates Dengvaxia vaccine and insecticide (adulticide) control strategies to forecast the dynamics of transmission and control of dengue in Madeira Island if there is a new outbreak with a different virus serotypes after the first outbreak in 2012. We construct suitable Lyapunov functions to investigate the global stability of the disease-free and boundary equilibrium points. Qualitative analysis of the model which incorporates time-varying controls with the specific goal of minimizing dengue disease transmission and the costs related to the control implementation by employing the optimal control theory is carried out. Three strategies, namely the use of Dengvaxia vaccine only, application of adulticide only, and the combination of Dengvaxia vaccine and adulticide are considered for the controls implementation. The necessary conditions are derived for the optimal control of dengue. We examine the impacts of the control strategies on the dynamics of infected humans and mosquito population by simulating the optimality system. The disease-freeequilibrium is found to be globally asymptotically stable whenever the basic reproduction numbers associated with virus serotypes 1 and j (j 2 {2, 3, 4}), respectively, satisfy R01,R0j 1, and the boundary equilibrium is globally asymptotically stable when the related R0i (i = 1, j) is above one. It is shown that the strategy based on the combination of Dengvaxia vaccine and adulticide helps in an effective control of dengue spread in the Island.

scholarly journals Assessment of Risk Factors of African Swine Fever in India: Perspectives on Future Outbreaks and Control Strategies

Pathogens ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1044
Author(s):  
Mousumi Bora ◽  
Durlav Prasad Bora ◽  
Mohan Manu ◽  
Nagendra Nath Barman ◽  
Lakshya Jyoti Dutta ◽  
...  
Keyword(s):  
Risk Factors ◽  
Disease Transmission ◽  
Control Strategies ◽  
African Swine Fever ◽  
Small Scale ◽  
Wild Pigs ◽  
Wildlife Reservoirs ◽  
Potential Risk Factors ◽  
And Control ◽  
Near Future

African swine fever (ASF) is one of the most important transboundary diseases of pigs. ASF has been identified in India for the first time in domestic pigs from outbreaks reported in two of the northeastern states, Arunachal Pradesh and Assam in 2020. A total of 11 ASF outbreaks in different regions killed over 3700 pigs and devastated the economy of small-scale livestock owners of both the states. Considering the first outbreak of ASF in India, a generic risk assessment framework was determined to identify potential risk factors that might favor future emergence of the disease. Based on the Indian scenario, we considered population density of host, farming practice, availability of biological vectors and wildlife reservoirs, epidemiological cycles, and international trade to analyze the possibility of future outbreaks of ASF and chances of establishment of endemism. On critical analysis of the identified risk factors associated with ASFV transmission, we observed that the risk factors are well preserved in the Indian geography and might participate in future outbreaks, further disseminating the disease to nearby countries. Since no vaccine is currently available against ASF, the domestic and the wild pigs (wild boars and the endangered pygmy hogs native to India) of this region are under constant threat of infection. For the near future, this region will have to continue to rely on the implementation of preventive measures to avoid the devastating losses that outbreaks can cause. The various adaptive control strategies to minimize the risks associated with the transmission of ASF, keeping our views to Indian settings, have been described. The risk-analysis framework presented in the study will give a further understanding of the dynamics of disease transmission and will help to design control strategies and corresponding measures to minimize the catastrophic consequences of ASF disease.

scholarly journals Modelling interference between vectors of non-persistently transmitted plant viruses to identify effective control strategies

2021 ◽  
Vol 17 (12) ◽  
pp. e1009727
Author(s):  
Marta Zaffaroni ◽  
Loup Rimbaud ◽  
Ludovic Mailleret ◽  
Nik J. Cunniffe ◽  
Daniele Bevacqua
Keyword(s):  
Disease Transmission ◽  
Plant Disease ◽  
Control Strategies ◽  
Management Strategies ◽  
Plant Viruses ◽  
Effective Control ◽  
Agronomic Practices ◽  
Ecological Principles ◽  
Single Host ◽  
Primary Vector

Aphids are the primary vector of plant viruses. Transient aphids, which probe several plants per day, are considered to be the principal vectors of non-persistently transmitted (NPT) viruses. However, resident aphids, which can complete their life cycle on a single host and are affected by agronomic practices, can transmit NPT viruses as well. Moreover, they can interfere both directly and indirectly with transient aphids, eventually shaping plant disease dynamics. By mean of an epidemiological model, originally accounting for ecological principles and agronomic practices, we explore the consequences of fertilization and irrigation, pesticide deployment and roguing of infected plants on the spread of viral diseases in crops. Our results indicate that the spread of NPT viruses can be i) both reduced or increased by fertilization and irrigation, depending on whether the interference is direct or indirect; ii) counter-intuitively increased by pesticide application and iii) reduced by roguing infected plants. We show that a better understanding of vectors’ interactions would enhance our understanding of disease transmission, supporting the development of disease management strategies.

Live-trapping and bovine tuberculosis testing of free-ranging white-tailed deer for targeted removal

2012 ◽  
Vol 39 (2) ◽  
pp. 104 ◽  
Author(s):  
Melinda K. Cosgrove ◽  
Henry Campa ◽  
Stephen M. Schmitt ◽  
David R. Marks ◽  
Anthony S. Wilson ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Bovine Tuberculosis ◽  
Blood Test ◽  
Bacterial Culture ◽  
Control Strategies ◽  
Rapid Test ◽  
The North ◽  
Live Trapping ◽  
The Cost ◽  
Free Ranging

Context Significant efforts have been made in Michigan, USA, to reduce the prevalence of bovine tuberculosis (TB) in free-ranging white-tailed deer (Odocoileus virginianus) over the past 15 years. Since 2002, however, prevalence has changed little, prompting the need for new control strategies. Aims In January–March of 2007 and 2008, a trap–test–cull project was conducted on an 11 000-ha property in the north-eastern Lower Peninsula of Michigan. The objectives were to assess the feasibility of live-trapping and testing white-tailed deer for TB as a means for targeted removal and estimate the cost of this effort. Methods Live-trapped deer were ear-tagged and a blood sample was drawn for use with the CervidTB STAT-PAK (commonly called Rapid Test) for TB diagnosis in the field. Deer testing negative were released, whereas deer testing positive were euthanised to confirm blood-test results via bacterial culture. Key results In all, 762 (741 with known sex and age) individual deer were captured and tested for TB. Adults comprised 59% (437 of 741) of the captures. Eight (1.8%) adults were positive on the blood test; six of eight (1.4% of adults) were confirmed TB positive via bacterial culture. Estimated TB prevalence in the present study was 2.5% (adjusted for Rapid Test sensitivity of 56%), being lower than what would be expected on the basis of routine hunter-harvest surveillance for this site which has yielded prevalence rates from 3.4% to 4.8%. Results demonstrated the ability to trap and test a substantial number of deer given high deer densities (16–20 deer per km2), availability of traps and abundant workers. The 2-year project cost a total of ~US$228 000, or US$38 000 per culture-positive animal. Conclusions Because of the cost and effort involved, a project such as the present one applied to Michigan’s larger TB-management area (148 018 ha) is not feasible. Implications If the efficiency and effectiveness of a trap–test–cull project could be improved by vaccinating test-negative animals, should a vaccine be approved for use in free-ranging white-tailed deer, a trap–test–cull project applied on a scale similar to the present study may prove beneficial by possibly reducing disease transmission, in addition to removing TB-positive animals.

scholarly journals Bushmeat and zoonoses threats warrant need for national zoonoses combat inter-disciplinary research partnership, evolving citizen science and policy ban of trade and consumption

2020 ◽  
Vol 7 (1) ◽  
pp. 68
Author(s):  
Ansu Thomas
Keyword(s):  
Species Diversity ◽  
Citizen Science ◽  
Disease Transmission ◽  
Meta Analysis ◽  
Dilution Effect ◽  
Research Partnership ◽  
Mammal Species ◽  
Science And Policy ◽  
Deforestation Rate ◽  
Bat Coronavirus

<p class="Noindentpara">“We must find them before they find us” said Dr.Shi, Bat Virologist”. Indian bat species diversity stands 127 ssp and China 147 bat ssp. Indian publications online (2000-2020), searching “bat”, “Chiroptera”, “India”, retrieved results viz., 191 (Elsevier); 27 (Scopus) and 0 (Wiley). For China, 594 publications exist (2000-2017)2; Himalayan cave bat biodiversity is not systematized, average annual deforestation rate, from 2000 to 2014 being 0.5% (Bhutan, Nepal) but 1.3% in India, China. “Dilution effect”, so-called “negative diversity–disease”, says ‘biodiversity losses promote disease transmission’. Protecting natural areas from human incursion reduces zoonotic disease spillover. Emergence of bat coronavirus represents recent viral explosion reaction to declining biodiversity. Meta-analysis of 143 hunting studies from India showed 114 mammal species but bat-hunting data absent.</p>

scholarly journals 205Zoonotic disease transmission risk in displaced populations

2021 ◽  
Vol 50 (Supplement_1) ◽  
Author(s):  
Gates Scholar Dorien Braam ◽  
Freya Jephcott ◽  
James Wood
Keyword(s):  
Risk Factors ◽  
Disease Transmission ◽  
Disease Risk ◽  
Forced Migration ◽  
Zoonotic Disease ◽  
Humanitarian Assistance ◽  
Transmission Risk ◽  
Case Study Methodology ◽  
Displaced Populations ◽  
Zoonotic Disease Transmission

Abstract Background Repeated spillover events of zoonotic diseases from animals to humans, in combination with unprecedented levels of forced migration, present a major challenge to the global health security agenda. Infectious disease risk is affected by a range of ecological, political and socio-economic drivers. Methods This study uses a qualitative case study methodology to determine how displacement affects the risks of zoonotic disease transmission. Based on key informant interviews and observational studies in Jordan and Pakistan, the study analyses social-structural factors impacting zoonotic disease transmission. Results The study shows that displacement may influence zoonotic disease transmission through its impact on environmental, socio-economic and behavioural factors, influenced by historical, political and socio-economic processes. Sporadic outbreaks of zoonoses including cutaneous leishmaniasis, rabies and Tuberculosis are reported among displaced populations. Risk factors include a decline in health services, increased population density, changes in environment, and reduced quality and availability of shelter, water and nutrition, in turn determining vulnerability to vectors and pathogens. Conclusions Risk factors affecting zoonoses in displacement are complex and interlinked. While the presence of animals may increase the risk in densely populated areas lacking hygiene, livestock may be beneficial to the health status of displaced by improving nutrition. Responses need to be interdisciplinary, multilevel and contextualized. Key messages To mitigate the risk of zoonotic disease transmission during displacement, responses need to include pathogen and vector control, as well as reducing vulnerability to disease, including through access to health and veterinary services and humanitarian assistance.

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