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.

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.

A Candide response to Panglossian accusations by Randolph and Dobson: biodiversity buffers disease

Parasitology ◽  
2013 ◽  
Vol 140 (10) ◽  
pp. 1196-1198 ◽  
Author(s):  
RICHARD S. OSTFELD
Keyword(s):  
Infectious Disease ◽  
Disease Risk ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Widespread Phenomenon ◽  
High Diversity

SUMMARYRandolph and Dobson (2012) criticize the dilution effect, which describes the negative relationship between biodiversity and infectious disease risk. Unfortunately, their commentary includes distortions, errors of omission, and errors of commission, which are rebutted herein. Contrary to their claims, the dilution effect is not a ‘mantra’ that asserts that reduced disease risk is a ‘universal’ outcome of high diversity. Although universality of the dilution effect has not been claimed, and conditions under which diversity can amplify disease risk have been described, the growing literature indicates that the dilution effect is indeed a widespread phenomenon.

The diversity–disease relationship: evidence for and criticisms of the dilution effect

Parasitology ◽  
2016 ◽  
Vol 143 (9) ◽  
pp. 1075-1086 ◽  
Author(s):  
Z. Y. X. HUANG ◽  
F. VAN LANGEVELDE ◽  
A. ESTRADA-PEÑA ◽  
G. SUZÁN ◽  
W. F. DE BOER
Keyword(s):  
Species Diversity ◽  
Host Species ◽  
Disease Risk ◽  
Current Knowledge ◽  
Risk Measures ◽  
Extinction Risk ◽  
Meta Analysis ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Landscape Fragmentation

SUMMARYThe dilution effect, that high host species diversity can reduce disease risk, has attracted much attention in the context of global biodiversity decline and increasing disease emergence. Recent studies have criticized the generality of the dilution effect and argued that it only occurs under certain circumstances. Nevertheless, evidence for the existence of a dilution effect was reported in about 80% of the studies that addressed the diversity–disease relationship, and a recent meta-analysis found that the dilution effect is widespread. We here review supporting and critical studies, point out the causes underlying the current disputes. The dilution is expected to be strong when the competent host species tend to remain when species diversity declines, characterized as a negative relationship between species’ reservoir competence and local extinction risk. We here conclude that most studies support a negative competence–extinction relationship. We then synthesize the current knowledge on how the diversity–disease relationship can be modified by particular species in community, by the scales of analyses, and by the disease risk measures. We also highlight the complex role of habitat fragmentation in the diversity–disease relationship from epidemiological, evolutionary and ecological perspectives, and construct a synthetic framework integrating these three perspectives. We suggest that future studies should test the diversity–disease relationship across different scales and consider the multiple effects of landscape fragmentation.

scholarly journals Tracing cross species transmission of Mycobacterium bovis at the wildlife/livestock interface in South Africa 

2020 ◽  
Author(s):  
Petronillah Rudo Sichewo ◽  
Tiny M. Hlokwe ◽  
Eric M.C. Etter ◽  
Anita L. Michel
Keyword(s):  
South Africa ◽  
Mycobacterium Bovis ◽  
Bovine Tuberculosis ◽  
Variable Number ◽  
Control Measures ◽  
Economic Losses ◽  
African Buffalo ◽  
High Genetic Variability ◽  
Spoligotype Pattern ◽  
Public Health Threat

Abstract Background: Bovine tuberculosis (bTB) affects cattle and wildlife in South Africa with the African buffalo (Syncerus caffer) as the principal maintenance host. The presence of a wildlife maintenance host at the wildlife/livestock interface acting as spill-over host makes it much more challenging to control and eradicate bTB in cattle. Spoligotyping and mycobacterial interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) genotyping methods were performed to investigate the genetic diversity of Mycobacterium bovis (M. bovis) isolates from cattle and wildlife, their distribution and transmission at the wildlife/livestock interface in northern Kwa-Zulu Natal (KZN), South Africa. Results: SB0130 was identified as the dominant spoligotype pattern at this wildlife/livestock interface, while VNTR typing revealed a total of 29 VNTR profiles (strains) in the KZN province signifying high genetic variability. The detection of 5 VNTR profiles shared between cattle and buffalo suggests M. bovis transmission between species. MIRU-VNTR confirmed co-infection in one cow with three strains of M. bovis that differed at a single locus, with 2 being shared with buffalo, implying pathogen introduction from most probably unrelated wildlife sources. Conclusion: Our findings highlight inter and intra species transmission of bTB at the wildlife/livestock interface and the need for the implementation of adequate bTB control measures to mitigate the spread of the pathogen responsible for economic losses and a public health threat.

scholarly journals Tracing cross species transmission of Mycobacterium bovis at the wildlife/livestock interface in South Africa

2020 ◽  
Author(s):  
Petronillah Rudo Sichewo ◽  
Tiny M. Hlokwe ◽  
Eric M.C. Etter ◽  
Anita L. Michel
Keyword(s):  
South Africa ◽  
Mycobacterium Bovis ◽  
Bovine Tuberculosis ◽  
Variable Number ◽  
Control Measures ◽  
Economic Losses ◽  
African Buffalo ◽  
High Genetic Variability ◽  
Spoligotype Pattern ◽  
Public Health Threat

Abstract Background Bovine tuberculosis (bTB) affects cattle and wildlife in South Africa with the African buffalo ( Syncerus caffer ) as the principal maintenance host. The presence of a wildlife maintenance host at the wildlife/livestock interface acting as spill-over host makes it much more challenging to control and eradicate bTB in cattle. Spoligotyping and mycobacteria interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) genotyping methods were performed to investigate the genetic diversity of Mycobacterium bovis ( M. bovis ) isolates from cattle and wildlife, their distribution and transmission at the wildlife/livestock interface in northern Kwa-Zulu Natal (KZN), South Africa. Results SB0130 was identified as the dominant spoligotype pattern at this wildlife/livestock interface, while VNTR typing revealed a total of 29 VNTR profiles (strains) in the KZN province signifying high genetic variability. The detection of 5 VNTR profiles shared between cattle and buffalo suggests M. bovis transmission between species. MIRU-VNTR confirmed co-infection in one cow with three strains of M. bovis that differed at a single locus, with 2 being shared with buffalo, implying pathogen introduction from most probably unrelated wildlife sources. Conclusion Our findings highlight inter and intra species transmission of bTB at the wildlife/livestock interface and the need for the implementation of adequate bTB control measures to mitigate the spread of the pathogen responsible for economic losses and a public health threat.

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 Tracing cross species transmission of Mycobacterium bovis at the wildlife/livestock interface in South Africa

2019 ◽  
Author(s):  
Petronillah Rudo Sichewo ◽  
Tiny M. Hlokwe ◽  
Eric M.C. Etter ◽  
Anita L. Michel
Keyword(s):  
South Africa ◽  
Mycobacterium Bovis ◽  
Bovine Tuberculosis ◽  
Variable Number ◽  
Control Measures ◽  
Economic Losses ◽  
African Buffalo ◽  
High Genetic Variability ◽  
Spoligotype Pattern ◽  
Public Health Threat

Abstract Background Bovine tuberculosis (bTB) affects cattle and wildlife in South Africa with the African buffalo ( Syncerus caffer ) as the principal maintenance host. The presence of a wildlife maintenance host at the wildlife/livestock interface acting as spill-over host makes it much more challenging to control and eradicate bTB in cattle. Spoligotyping and mycobacteria interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) genotyping methods were performed to investigate the genetic diversity of Mycobacterium bovis ( M. bovis ) isolates from cattle and wildlife, their distribution and transmission at the wildlife/livestock interface in northern Kwa-Zulu Natal (KZN), South Africa. Results SB0130 was identified as the dominant spoligotype pattern at this wildlife/livestock interface, while VNTR typing revealed a total of 29 VNTR profiles (strains) in the KZN province signifying high genetic variability. The detection of 5 VNTR profiles shared between cattle and buffalo suggests M. bovis transmission between species. MIRU-VNTR confirmed co-infection in one cow with three strains of M. bovis that differed at a single locus, with 2 being shared with buffalo, implying pathogen introduction from most probably unrelated wildlife sources. Conclusion Our findings highlight inter and intra species transmission of bTB at the wildlife/livestock interface and the need for the implementation of adequate bTB control measures to mitigate the spread of the pathogen responsible for economic losses and a public health threat.

scholarly journals Root-Plate Characteristics of Common Aspen in Hemiboreal Forests of Latvia: A Case Study

Forests ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 32
Author(s):  
Valters Samariks ◽  
Dace Brizga ◽  
Jeļena Rūba ◽  
Andris Seipulis ◽  
Āris Jansons
Keyword(s):  
Root System ◽  
Complex Structure ◽  
Mineral Soil ◽  
Negative Relationship ◽  
Tree Height ◽  
Belowground Biomass ◽  
Rooting Depth ◽  
Economic Losses ◽  
Coarse Roots ◽  
Root Plate

Climate change will cause winds to strengthen and storms to become more frequent in Northern Europe. Windstorms reduce the financial value of forests by bending, breaking, or uprooting trees, and wind-thrown trees cause additional economic losses. The resistance of trees to wind damage depends on tree species, tree- and stand-scale parameters, and root-soil plate characteristics such as root-plate size, weight, and rooting depth. The root-soil plate is a complex structure whose mechanical strength is dependent on root-plate width and depth, as the root system provides root attachment with soil and structural support. In Latvia, the common aspen (Populus tremula L.) root system has been studied to develop a belowground biomass model, because information about root system characteristics in relation to tree wind resistance is scarce. The aim of this study was to assess the root-plate dimensions of common aspen stands on fertile mineral soil (luvisol). Study material was collected in the central region of Latvia, where pure mature (41–60 years old) common aspen stands were randomly selected, and dominant trees within the stand were chosen. In total, ten sample trees from ten stands were uprooted. The diameter at breast height (DBH) and tree height (H) were measured for each sample tree, and their roots were excavated, divided into groups, washed, measured, and weighed. The highest naturally moist biomass values were observed for coarse roots, and fine root biomass was significantly lower compared to other root groups. All root group biomass values had a strong correlation with the tree DBH. The obtained results show that there is a close, negative relationship between the relative distance from the stem and the relative root-plate depth distribution.

scholarly journals Lower Richness of Small Wild Mammal Species and Chagas Disease Risk

2012 ◽  
Vol 6 (5) ◽  
pp. e1647 ◽  
Author(s):  
Samanta Cristina das Chagas Xavier ◽  
André Luiz Rodrigues Roque ◽  
Valdirene dos Santos Lima ◽  
Kerla Joeline Lima Monteiro ◽  
Joel Carlos Rodrigues Otaviano ◽  
...  
Keyword(s):  
Chagas Disease ◽  
Disease Risk ◽  
Wild Mammal ◽  
Mammal Species

scholarly journals Bovine tuberculosis disturbs parasite functional trait composition in African buffalo

2019 ◽  
Vol 116 (29) ◽  
pp. 14645-14650 ◽  
Author(s):  
Brianna R. Beechler ◽  
Kate S. Boersma ◽  
Peter E. Buss ◽  
Courtney A. C. Coon ◽  
Erin E. Gorsich ◽  
...  
Keyword(s):  
Community Composition ◽  
Bovine Tuberculosis ◽  
Community Dynamics ◽  
Parasite Community ◽  
Functional Trait ◽  
Taxonomic Composition ◽  
African Buffalo ◽  
Emerging Infections ◽  
Parasite Communities ◽  
Parasite Richness

Novel parasites can have wide-ranging impacts, not only on host populations, but also on the resident parasite community. Historically, impacts of novel parasites have been assessed by examining pairwise interactions between parasite species. However, parasite communities are complex networks of interacting species. Here we used multivariate taxonomic and trait-based approaches to determine how parasite community composition changed when African buffalo (Syncerus caffer) acquired an emerging disease, bovine tuberculosis (BTB). Both taxonomic and functional parasite richness increased significantly in animals that acquired BTB than in those that did not. Thus, the presence of BTB seems to catalyze extraordinary shifts in community composition. There were no differences in overall parasite taxonomic composition between infected and uninfected individuals, however. The trait-based analysis revealed an increase in direct-transmitted, quickly replicating parasites following BTB infection. This study demonstrates that trait-based approaches provide insight into parasite community dynamics in the context of emerging infections.

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