scholarly journals Non-random biodiversity loss underlies predictable increases in viral disease prevalence

2014 ◽  
Vol 11 (92) ◽  
pp. 20130947 ◽  
Author(s):  
Christelle Lacroix ◽  
Anna Jolles ◽  
Eric W. Seabloom ◽  
Alison G. Power ◽  
Charles E. Mitchell ◽  
...  
Keyword(s):  
Host Species ◽  
Species Abundance ◽  
Virus Transmission ◽  
Biodiversity Loss ◽  
Viral Disease ◽  
Field Trials ◽  
Disease Prevalence ◽  
Infection Prevalence ◽  
Virus Prevalence ◽  
Local Host

Disease dilution (reduced disease prevalence with increasing biodiversity) has been described for many different pathogens. Although the mechanisms causing this phenomenon remain unclear, the disassembly of communities to predictable subsets of species, which can be caused by changing climate, land use or invasive species, underlies one important hypothesis. In this case, infection prevalence could reflect the competence of the remaining hosts. To test this hypothesis, we measured local host species abundance and prevalence of four generalist aphid-vectored pathogens (barley and cereal yellow dwarf viruses) in a ubiquitous annual grass host at 10 sites spanning 2000 km along the North American West Coast. In laboratory and field trials, we measured viral infection as well as aphid fecundity and feeding preference on several host species. Virus prevalence increased as local host richness declined. Community disassembly was non-random: ubiquitous hosts dominating species-poor assemblages were among the most competent for vector production and virus transmission. This suggests that non-random biodiversity loss led to increased virus prevalence. Because diversity loss is occurring globally in response to anthropogenic changes, such work can inform medical, agricultural and veterinary disease research by providing insights into the dynamics of pathogens nested within a complex web of environmental forces.

Gastric Nematode Communities in Lizards From the Great Victoria Desert, and an Hypothesis for Their Evolution

1995 ◽  
Vol 43 (2) ◽  
pp. 141 ◽  
Author(s):  
HI Jones
Keyword(s):  
Host Species ◽  
Species Abundance ◽  
Nematode Species ◽  
Geographical Range ◽  
Infection Prevalence ◽  
Intermediate Hosts ◽  
Epidemiological Evidence ◽  
Lizard Species ◽  
Evolutionary Phase ◽  
Paratenic Hosts

This study examines the biology of gastric nematodes in two communities of lizards from the Great Victoria Desert, and develops an hypothesis for their evolution. Abbreviata antarctica A. hastaspicula, A, levicauda, A. tumidocapitis, Skrjabinoptera goldmanae, Kreisiella chrysocampa, Physalopteroides filicauda, Wanaristrongylus ctenoti and W. papangawurpae were recovered from 3023 lizards of 45 species from two different habitats. Genera in the Physalopterinae (Abbreviata, Skrjabinoptera and Kreisiella) exhibited narrow host specificities, Abbreviara and Skrjabinoptera occurring as adults only in larger host species (Varanus gouldii, V. tristis and Pogona minor). P. filicauda and encysted larvae of Physalopterinae occurred widely in the smaller lizard species in all five families represented. Eight of the nine nematode species were recovered from both lizard populations, and differences in prevalence and number of host species infected are discussed in terms of core hosts providing an infective pool. Associations were derived between parameters of infection (prevalence, intensity and abundance) and host size across and within species; abundance of nematodes in Ctenotus skinks correlated with host geographical range. Epidemiological evidence is presented that suggests that termites are intermediate hosts to species of Physalopterinae, and that Orthoptera may be intermediate hosts to P.filicauda. It is suggested that species in the Physalopterinae arose in smaller lizards (where they are now represented by the morphologically primitive Kreisiella), and that they were acquired by large predatory species by host capture, and in which they are now speciating. The small lizards now act as paratenic hosts to their larvae, and the niches left vacant have been occupied by P. filicauda. It is concluded that P.filicauda is at an early non-interactive phase and that Abbreviata and Skrjabinoptera are at an evolutionary phase, and are evolving along with their hosts. Thus, the two principal nematode groups arose at different times in response to the radiation and ecology of their hosts, and are at different stages in their own evolution.

scholarly journals Toward a unified dilution effect theory: How competence, competition, and the transmission mechanism influence disease prevalence

2020 ◽  
Author(s):  
Michael H. Cortez ◽  
Meghan A. Duffy
Keyword(s):  
Host Species ◽  
Dilution Effect ◽  
Disease Prevalence ◽  
Pathogen Transmission ◽  
Transmission Mechanism ◽  
Infection Prevalence ◽  
Host Interactions ◽  
Host Diversity ◽  
Disease Patterns ◽  
Effect Theory

ABSTRACTBiodiversity in communities is changing globally, including the gain and loss of host species in host-pathogen communities. The dilution effect argues for a mechanistic link between increased host diversity and decreased disease in a focal host. However, we currently have a limited understanding of how the pathogen transmission mechanism and between-host interactions influence whether increased host diversity leads to increased (amplification) or decreased (dilution) infection prevalence. We use a two-host-one-pathogen model to unify theory for pathogens with environmental transmission and density-dependent and frequency-dependent direct transmission. We then identify general rules governing how the pathogen transmission mechanism and characteristics of the introduced host (disease competence and competitive ability) influence whether the introduction of a second host species increases or decreases disease prevalence in a focal host. We discuss how our results yield insight into how specific biological mechanisms shape host biodiversity-disease patterns.

scholarly journals Assessing Habitat Vulnerability and Loss of Naturalness: Applying the GLOBIO3 Model in the Czech Republic

2021 ◽  
Vol 13 (10) ◽  
pp. 5355
Author(s):  
Vilém Pechanec ◽  
Ondřej Cudlín ◽  
Miloš Zapletal ◽  
Jan Purkyt ◽  
Lenka Štěrbová ◽  
...  
Keyword(s):  
Land Use ◽  
Czech Republic ◽  
Habitat Quality ◽  
Species Abundance ◽  
Biodiversity Loss ◽  
Infrastructure Development ◽  
Natural Habitats ◽  
The Czech Republic ◽  
New Equation ◽  
The Impact

Global and regional biodiversity loss is caused by several drivers including urban development, land use intensification, overexploitation of natural resources, environmental pollution, and climate change. The main aim of our study was to adapt the GLOBIO3 model to the conditions of the Czech Republic (CR) to assess loss of naturalness and biodiversity vulnerability at the habitat level on a detailed scale across the entire CR. An additional aim was to assess the main drivers affecting the biodiversity of habitat types. The GLOBIO3 model was adapted to CZ-GLOBIO by adapting global to local scales and using habitat quality and naturalness data instead of species occurrence data. The total mean species abundance (MSA) index of habitat quality, calculated from the spatial overlay of the four MSA indicators by our new equation, reached the value 0.62. The total value of MSA for natural and near-natural habitats was found to be affected mainly by infrastructure development and fragmentation. Simultaneously, intensity of land use change and atmospheric nitrogen deposition contributed primarily to the low total value of MSA for distant natural habitats. The CZ-GLOBIO model can be an important tool in political decision making to reduce the impact of the main drivers on habitat biodiversity in the CR.

scholarly journals Rotational worker vaccination provides indirect protection to vulnerable groups in regions with low COVID-19 prevalence

2021 ◽  
Vol 7 (3) ◽  
pp. 3988-4003
Author(s):  
Maria M. Martignoni ◽  
◽  
Proton Rahman ◽  
Amy Hurford ◽  
◽  
...  
Keyword(s):  
Older Adults ◽  
Labour Force ◽  
Disease Prevalence ◽  
Vulnerable Groups ◽  
Severe Illness ◽  
Infection Prevalence ◽  
Average Risk ◽  
Susceptible Population ◽  
Icu Admission ◽  
Indirect Protection

<abstract><p>As COVID-19 vaccines become available, different model-based approaches have been developed to evaluate strategic priorities for vaccine allocation to reduce severe illness. One strategy is to directly prioritize groups that are likely to experience medical complications due to COVID-19, such as older adults. A second strategy is to limit community spread by reducing importations, for example by vaccinating members of the mobile labour force, such as rotational workers. This second strategy may be appropriate for regions with low disease prevalence, where importations are a substantial fraction of all cases and reducing the importation rate reduces the risk of community outbreaks, which can provide significant indirect protection for vulnerable individuals. Current studies have focused on comparing vaccination strategies in the absence of importations, and have not considered allocating vaccines to reduce the importation rate. Here, we provide an analytical criteria to compare the reduction in the risk of hospitalization and intensive care unit (ICU) admission over four months when either older adults or rotational workers are prioritized for vaccination. Vaccinating rotational workers (assumed to be 6,000 individuals and about 1% of the Newfoundland and Labrador (NL) population) could reduce the average risk of hospitalization and ICU admission by 42%, if no community spread is observed at the time of vaccination, because epidemic spread is reduced and vulnerable individuals are indirectly protected. In contrast, vaccinating all individuals aged 75 and older (about 43,300 individuals, or 8% of the NL population) would lead to a 24% reduction in the average risk of hospitalization, and to a 45% reduction in the average risk of ICU admission, because a large number of individuals at high risk from COVID-19 are now vaccinated. Therefore, reducing the risk of hospitalization and ICU admission of the susceptible population by reducing case importations would require a significantly lower number of vaccines. Benefits of vaccinating rotational workers decrease with increasing infection prevalence in the community. Prioritizing members of the mobile labour force should be considered as an efficient strategy to indirectly protect vulnerable groups from COVID-19 exposure in regions with low disease prevalence.</p></abstract>

Transmission and pathogenicity of papaya virus E: insights from an experimental papaya orchard

Plant Disease ◽  
2021 ◽  
Author(s):  
Juan F Cornejo-Franco ◽  
Edison Gonzalo Reyes-Proaño ◽  
Dimitre Mollov ◽  
Joseph Mowery ◽  
Diego Fernando Quito-Avila
Keyword(s):  
Mosaic Virus ◽  
Bemisia Tabaci ◽  
Carica Papaya ◽  
Virus Transmission ◽  
Ringspot Virus ◽  
Mixed Infections ◽  
Papaya Ringspot Virus ◽  
Greenhouse Experiments ◽  
Virus Prevalence ◽  
Macroptilium Lathyroides

A study was conducted to investigate epidemiological aspects of papaya virus E (PpVE), a cytorhabdovirus commonly found in papaya (Carica papaya L.) plantings of Ecuador. Besides papaya, PpVE was found in three Fabaceae weeds, including Rhynchosia minima, Centrosema plumieri and Macroptilium lathyroides; the latter being the species with the highest virus prevalence. Greenhouse experiments showed that in M. lathyroides, single infections of PpVE induce only mild leaf mosaic, whereas in mixed infections with cowpea severe mosaic virus, PpVE contributes to severe mosaic. In papaya, PpVE did not induce noticeable symptoms in single or mixed infections with papaya ringspot virus. Transmission experiments confirmed that whiteflies (Bemisia tabaci) transmit PpVE in a semi-persistent, non-propagative manner.

The influence of landscape and environmental factors on ranavirus epidemiology in amphibian assemblages

2017 ◽  
Author(s):  
Brian J. Tornabene ◽  
Andrew R. Blaustein ◽  
Cheryl J. Briggs ◽  
Dana M. Calhoun ◽  
Pieter T. J. Johnson ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Host Species ◽  
Dilution Effect ◽  
Variance Partitioning ◽  
Lower Probability ◽  
Infection Prevalence ◽  
Taxonomic Richness ◽  
Amphibian Disease ◽  
Competing Models ◽  
Reservoir Hosts

ABSTRACTAimTo quantify the influence of a suite of landscape, abiotic, biotic, and host-level variables on ranavirus disease dynamics in amphibian assemblages at two biological levels (site and host-level).LocationWetlands within the East Bay region of California, USA.MethodsWe used competing models, multimodel inference, and variance partitioning to examine the influence of 16 landscape and environmental factors on patterns in site-level ranavirus presence and host-level ranavirus infection in 76 wetlands and 1,377 amphibian hosts representing five species.ResultsThe landscape factor explained more variation than any other factors in site-level ranavirus presence, but biotic and host-level factors explained more variation in host-level ranavirus infection. At both the site- and host-level, the probability of ranavirus presence correlated negatively with distance to nearest ranavirus-positive wetland. At the site-level, ranavirus presence was associated positively with taxonomic richness. However, infection prevalence within the amphibian population correlated negatively with vertebrate richness. Finally, amphibian host species differed in their likelihood of ranavirus infection: American Bullfrogs had the weakest association with infection while Western Toads had the strongest. After accounting for host species effects, hosts with greater snout-vent length had a lower probability of infection.Main conclusionsStrong spatial influences at both biological levels suggest that mobile taxa (e.g., adult amphibians, birds, reptiles) may facilitate the movement of ranavirus among hosts and across the landscape. Higher taxonomic richness at sites may provide more opportunities for colonization or the presence of reservoir hosts that may influence ranavirus presence. Higher host richness correlating with higher ranavirus infection is suggestive of a dilution effect that has been observed for other amphibian disease systems and warrants further investigation. Our study demonstrates that an array of landscape, environmental, and host-level factors were associated with ranavirus epidemiology and illustrates that their importance vary with biological level.

scholarly journals Favipiravir at high doses has potent antiviral activity in SARS-CoV-2−infected hamsters, whereas hydroxychloroquine lacks activity

2020 ◽  
Vol 117 (43) ◽  
pp. 26955-26965 ◽  
Author(s):  
Suzanne J. F. Kaptein ◽  
Sofie Jacobs ◽  
Lana Langendries ◽  
Laura Seldeslachts ◽  
Sebastiaan ter Horst ◽  
...  
Keyword(s):  
Antiviral Drug ◽  
Virus Transmission ◽  
Small Animal ◽  
Antiviral Effect ◽  
Viral Disease ◽  
Scientific Basis ◽  
Infection Model ◽  
High Dose ◽  
High Doses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly spread around the globe after its emergence in Wuhan in December 2019. With no specific therapeutic and prophylactic options available, the virus has infected millions of people of which more than half a million succumbed to the viral disease, COVID-19. The urgent need for an effective treatment together with a lack of small animal infection models has led to clinical trials using repurposed drugs without preclinical evidence of their in vivo efficacy. We established an infection model in Syrian hamsters to evaluate the efficacy of small molecules on both infection and transmission. Treatment of SARS-CoV-2−infected hamsters with a low dose of favipiravir or hydroxychloroquine with(out) azithromycin resulted in, respectively, a mild or no reduction in virus levels. However, high doses of favipiravir significantly reduced infectious virus titers in the lungs and markedly improved lung histopathology. Moreover, a high dose of favipiravir decreased virus transmission by direct contact, whereas hydroxychloroquine failed as prophylaxis. Pharmacokinetic modeling of hydroxychloroquine suggested that the total lung exposure to the drug did not cause the failure. Our data on hydroxychloroquine (together with previous reports in macaques and ferrets) thus provide no scientific basis for the use of this drug in COVID-19 patients. In contrast, the results with favipiravir demonstrate that an antiviral drug at nontoxic doses exhibits a marked protective effect against SARS-CoV-2 in a small animal model. Clinical studies are required to assess whether a similar antiviral effect is achievable in humans without toxic effects.

scholarly journals Culicoides species abundance and potential over-wintering of African horse sickness virus in the Onderstepoort area, Gauteng, South Africa

2014 ◽  
Vol 85 (1) ◽  
Author(s):  
Gert J. Venter ◽  
Karien Labuschagne ◽  
Daphney Majatladi ◽  
Solomon N.B. Boikanyo ◽  
Carina Lourens ◽  
...  
Keyword(s):  
South Africa ◽  
Species Abundance ◽  
Winter Period ◽  
Infection Prevalence ◽  
African Horse Sickness ◽  
African Horse Sickness Virus ◽  
Pcr Assay ◽  
Culicoides Imicola ◽  
The Mean ◽  
Polymerase Chain

In South Africa, outbreaks of African horse sickness (AHS) occur in summer; no cases are reported in winter, from July to September. The AHS virus (AHSV) is transmitted almost exclusively by Culicoides midges (Diptera: Ceratopogonidae), of which Culicoides imicola is considered to be the most important vector. The over-wintering mechanism of AHSV is unknown. In this study, more than 500 000 Culicoides midges belonging to at least 26 species were collected in 88 light traps at weekly intervals between July 2010 and September 2011 near horses in the Onderstepoort area of South Africa. The dominant species was C. imicola. Despite relatively low temperatures and frost, at least 17 species, including C. imicola, were collected throughout winter (June–August). Although the mean number of midges per night fell from > 50 000 (March) to < 100 (July and August), no midge-free periods were found. This study, using virus isolation on cell cultures and a reverse transcriptase polymerase chain reaction (RT-PCR) assay, confirmed low infection prevalence in field midges and that the detection of virus correlated to high numbers. Although no virus was detected during this winter period, continuous adult activity indicated that transmission can potentially occur. The absence of AHSV in the midges during winter can be ascribed to the relatively low numbers collected coupled to low infection prevalence, low virus replication rates and low virus titres in the potentially infected midges. Cases of AHS in susceptible animals are likely to start as soon as Culicoides populations reach a critical level.

Disruption of a host-parasite system following the introduction of an exotic host species

Parasitology ◽  
2005 ◽  
Vol 130 (6) ◽  
pp. 661-668 ◽  
Author(s):  
S. TELFER ◽  
K. J. BOWN ◽  
R. SEKULES ◽  
M. BEGON ◽  
T. HAYDEN ◽  
...  
Keyword(s):  
Bank Vole ◽  
Host Species ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Wood Mouse ◽  
Clethrionomys Glareolus ◽  
Infection Prevalence ◽  
Wood Mice ◽  
Effect Hypothesis ◽  
Host Parasite

The potential of biological invasions to threaten native ecosystems is well recognized. Here we describe how an introduced species impacts on native host-parasite dynamics by acting as an alternative host. By sampling sites across an invasion front in Ireland, we quantified the influence of the introduced bank vole (Clethrionomys glareolus) on the epidemiology of infections caused by flea-transmitted haemoparasites of the genusBartonellain native wood mice (Apodemus sylvaticus).Bartonellainfections were detected on either side of the front but occurred exclusively in wood mice, despite being highly prevalent in both rodent species elsewhere in Europe. Bank vole introduction has, however, affected the wood mouse-Bartonellainteraction, with the infection prevalence of bothBartonella birtlesiiandBartonella tayloriideclining significantly with increasing bank vole density. Whilst flea prevalence in wood mice increases with wood mouse density in areas without bank voles, no such relationship is detected in invaded areas. The results are consistent with the dilution effect hypothesis. This predicts that for vector-transmitted parasites, the presence of less competent host species may reduce infection prevalence in the principal host. In addition we found a negative relationship betweenB. birtlesiiandB. tayloriiprevalences, indicating that these two microparasites may compete within hosts.

scholarly journals Linking community and disease ecology: the impact of biodiversity on pathogen transmission

2012 ◽  
Vol 367 (1604) ◽  
pp. 2807-2813 ◽  
Author(s):  
Benjamin Roche ◽  
Andrew P. Dobson ◽  
Jean-François Guégan ◽  
Pejman Rohani
Keyword(s):  
Host Species ◽  
Disease Ecology ◽  
Biodiversity Loss ◽  
Pathogen Transmission ◽  
Community Diversity ◽  
Ecological Interactions ◽  
Disease Emergence ◽  
Pathogen Dynamics ◽  
Wildlife Pathogens ◽  
The Impact

The increasing number of zoonotic diseases spilling over from a range of wild animal species represents a particular concern for public health, especially in light of the current dramatic trend of biodiversity loss. To understand the ecology of these multi-host pathogens and their response to environmental degradation and species extinctions, it is necessary to develop a theoretical framework that takes into account realistic community assemblages. Here, we present a multi-host species epidemiological model that includes empirically determined patterns of diversity and composition derived from community ecology studies. We use this framework to study the interaction between wildlife diversity and directly transmitted pathogen dynamics. First, we demonstrate that variability in community composition does not affect significantly the intensity of pathogen transmission. We also show that the consequences of community diversity can differentially impact the prevalence of pathogens and the number of infectious individuals. Finally, we show that ecological interactions among host species have a weaker influence on pathogen circulation than inter-species transmission rates. We conclude that integration of a community perspective to study wildlife pathogens is crucial, especially in the context of understanding and predicting infectious disease emergence events.

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