Nonspecificity of the necrosis-inducing toxin of Sclerotium bataticola

1973 ◽  
Vol 51 (3) ◽  
pp. 690-692 ◽  
Author(s):  
Y. H. Chan ◽  
W. E. Sackston
Keyword(s):  
Host Species ◽  
Toxin Production ◽  
Susceptible Host ◽  
Necrotic Spotting

Sclerotium bataticola produces a translocatable toxin which induces necrotic spotting in sunflower leaves. The toxin is not host specific, and does not induce symptoms on all susceptible host species. Virulence of four isolates of S. bataticola is not correlated with their toxin production in culture.

Epidemiology and optimal foraging: modelling the ideal free distribution of insect vectors

Parasitology ◽  
2000 ◽  
Vol 120 (3) ◽  
pp. 319-327 ◽  
Author(s):  
D. W. KELLY ◽  
C. E. THOMPSON
Keyword(s):  
Host Species ◽  
Disease Transmission ◽  
Ideal Free Distribution ◽  
Host Population ◽  
Control Effort ◽  
Susceptible Host ◽  
Vector Density ◽  
Free Distribution ◽  
Blood Sucking ◽  
Ideal Free

Existing models of the basic case reproduction number (R0) for vector-borne diseases assume (i) that the distribution of vectors over the susceptible host species is homogenous and (ii) that the biting preference for the susceptible host species rather than other potential hosts is a constant. Empirical evidence contradicts both assumptions, with important consequences for disease transmission. In this paper we develop an Ideal Free Distribution (IFD) model of host choice by blood-sucking insects, predicated on the argument that vectors must have evolved to choose the least defensive hosts in order to maximize their feeding success. From a re-analysis of existing data, we demonstrate that the interference constant, m, of the IFD can vary between host species. As a result, the predicted distribution of insects over hosts has 2 desirable and intuitively plausible behaviours: that it is heterogeneous both within and between host species; and that the intensity of heterogeneity varies with host and vector density. When the IFD model is incorporated into R0, the relationship with the vector: host ratio becomes non-linear. If correct, the IFD could add considerable realism to models which seek to predict the effect of these ecological parameters on disease transmission as they vary naturally (e.g. through seasonality in vector density or host population movement) or as a consequence of artificial manipulation (e.g. zooprophylaxis, vector control). It raises the possibility of targeting transmission hot spots with greater accuracy and concomitant reduction in control effort. The robustness of the model to simplifying assumptions is discussed.

scholarly journals Methods for Detecting Mycobacterial Mixed Strain Infections–A Systematic Review

2020 ◽  
Vol 11 ◽  
Author(s):  
Alexander Stephen Byrne ◽  
Alex Goudreau ◽  
Nathalie Bissonnette ◽  
Isdore Chola Shamputa ◽  
Kapil Tahlan
Keyword(s):  
Systematic Review ◽  
Host Species ◽  
Search Strategy ◽  
Concurrent Infection ◽  
Accurate Identification ◽  
Susceptible Host ◽  
Mycobacterial Diseases ◽  
Typing Methods ◽  
Multiple Strains ◽  
Work Done

Mixed strain infection (MSI) refers to the concurrent infection of a susceptible host with multiple strains of a single pathogenic species. Known to occur in humans and animals, MSIs deserve special consideration when studying transmission dynamics, evolution, and treatment of mycobacterial diseases, notably tuberculosis in humans and paratuberculosis (or Johne's disease) in ruminants. Therefore, a systematic review was conducted to examine how MSIs are defined in the literature, how widespread the phenomenon is across the host species spectrum, and to document common methods used to detect such infections. Our search strategy identified 121 articles reporting MSIs in both humans and animals, the majority (78.5%) of which involved members of the Mycobacterium tuberculosis complex, while only a few (21.5%) examined non-tuberculous mycobacteria (NTM). In addition, MSIs exist across various host species, but most reports focused on humans due to the extensive amount of work done on tuberculosis. We reviewed the strain typing methods that allowed for MSI detection and found a few that were commonly employed but were associated with specific challenges. Our review notes the need for standardization, as some highly discriminatory methods are not adapted to distinguish between microevolution of one strain and concurrent infection with multiple strains. Further research is also warranted to examine the prevalence of NTM MSIs in both humans and animals. In addition, it is envisioned that the accurate identification and a better understanding of the distribution of MSIs in the future will lead to important information on the epidemiology and pathophysiology of mycobacterial diseases.

Effects of passaging through scarabeid hosts on virulence and host specificity of two strains of the entomopathogenic hyphomycete Metarhizium anisopliae

1983 ◽  
Vol 29 (5) ◽  
pp. 576-583 ◽  
Author(s):  
Jacques F. Fargues ◽  
Pierre H. Robert
Keyword(s):  
Host Species ◽  
Metarhizium Anisopliae ◽  
Insect Host ◽  
Artificial Medium ◽  
Susceptible Host ◽  
Single Host ◽  
Entomopathogenic Hyphomycete ◽  
Enzymatic Mechanisms ◽  
Phenotypic Responses

The effects on pathogenicity of Metarhizium anisopliae (Metsch.) Sor. following one or more passages through the original and the heterologous insect host species were investigated by using two pathotypes specific for Cetonia aurata L. and Oryctes rhinoceros L., respectively. A significant increase in virulence occurred after a single host passage. Thus, the infection potential of host-passed inocula could be increased by a factor of 10 to 100, and its host-induced adaptation was almost complete after the first in vivo passage. Bacteria located on the integument of the host cadaver were not implicated in this phenomenon. When the fungus was again grown on artificial medium, the loss in virulence was also very fast. Consequently, changes in virulence of the two tested strains seemed to be phenotypic responses implicating inducible enzymatic mechanisms. Nevertheless, the parasitic behaviour of the two pathotypes toward the larvae of the nonsusceptible species was not modified by host passaging through their respective insect hosts. It is concluded that changes in entomopathogenic hyphomycete virulence, resulting from host passage, concern only the naturally susceptible host species.

Host specificity and morphometric variation of Haemoproteus meleagridis Levine, 1961 (Protozoa: Haemosporina) in gallinaceous birds

1986 ◽  
Vol 64 (11) ◽  
pp. 2634-2638 ◽  
Author(s):  
Carter T. Atkinson
Keyword(s):  
Red Blood Cells ◽  
Host Specificity ◽  
Host Species ◽  
Blood Cells ◽  
Phasianus Colchicus ◽  
Morphometric Variation ◽  
Susceptible Host ◽  
Northern Bobwhites ◽  
Numida Meleagris ◽  
Intraperitoneal Inoculation

Haemoproteus meleagridis was transmitted to a ring-necked pheasant, Phasianus colchicus L., to a chuckar partridge, Alectoris chuckar (Gray), and to domestic turkeys by the intraperitoneal inoculation of sporozoites from pools of infected Culicoides edeni Wirth and Blanton, 1947, and Culicoides hinmani Khalaf, 1952. Guineafowl, Numida meleagris (L.), northern bobwhites, Colinus virginianus (L.), and chickens, Gallus gallus (L.), were not susceptible. Parasitemias in the infected chuckar and the infected pheasant were lower and more transient than parasitemias in domestic turkeys infected with the same number of sporozoites. Mature gametocytes of Haemoproteus meleagridis were morphologically similar in each susceptible host species. Infected red blood cells in each host species underwent increases in total area and decreases in nuclear size and area. The current taxonomy of Haemoproteus meleagridis is discussed in relation to recent revisions in the taxonomy of the avian hosts.

scholarly journals An experimental test of the independent action hypothesis in virus–insect pathosystems

2009 ◽  
Vol 276 (1665) ◽  
pp. 2233-2242 ◽  
Author(s):  
Mark P. Zwart ◽  
Lia Hemerik ◽  
Jenny S. Cory ◽  
J. Arjan G.M. de Visser ◽  
Felix J.J.A. Bianchi ◽  
...  
Keyword(s):  
Experimental Test ◽  
Host Species ◽  
Independent Action ◽  
Probabilistic Framework ◽  
Insect Larvae ◽  
Susceptible Host ◽  
Model Predictions ◽  
Late Instar ◽  
Early Instar ◽  
Host Death

The ‘independent action hypothesis’ (IAH) states that each pathogen individual has a non-zero probability of causing host death and that pathogen individuals act independently. IAH has not been rigorously tested. In this paper, we (i) develop a probabilistic framework for testing IAH and (ii) demonstrate that, in two out of the six virus–insect pathosystems tested, IAH is supported by the data. We first show that IAH inextricably links host survivorship to the number of infecting pathogen individuals, and develop a model to predict the frequency of single- and dual-genotype infections when a host is challenged with a mixture of two genotypes. Model predictions were tested using genetically marked, near-identical baculovirus genotypes, and insect larvae from three host species differing in susceptibility. Observations in early-instar larvae of two susceptible host species support IAH, but observations in late-instar larvae of susceptible host species and larvae of a less susceptible host species were not in agreement with IAH. Hence the model is experimentally supported only in pathosystems in which the host is highly susceptible. We provide, to our knowledge, the first qualitative experimental evidence that, in such pathosystems, the action of a single virion is sufficient to cause disease.

scholarly journals Mink is a highly susceptible host species to circulating human and avian influenza viruses

2021 ◽  
pp. 1-34
Author(s):  
Honglei Sun ◽  
Fangtao Li ◽  
Qingzhi Liu ◽  
Jianyong Du ◽  
Litao Liu ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Host Species ◽  
Influenza Viruses ◽  
Avian Influenza Viruses ◽  
Susceptible Host

scholarly journals Do Parasitic Trematode Cercariae Demonstrate a Preference for Susceptible Host Species?

PLoS ONE ◽  
2012 ◽  
Vol 7 (12) ◽  
pp. e51012 ◽  
Author(s):  
Brittany F. Sears ◽  
Andrea D. Schlunk ◽  
Jason R. Rohr
Keyword(s):  
Host Species ◽  
Susceptible Host

scholarly journals Global Geographic Distribution and Host Range of Fusarium circinatum, the Causal Agent of Pine Pitch Canker

Forests ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 724 ◽  
Author(s):  
Rein Drenkhan ◽  
Beccy Ganley ◽  
Jorge Martín-García ◽  
Petr Vahalík ◽  
Kalev Adamson ◽  
...  
Keyword(s):  
Host Range ◽  
Geographic Distribution ◽  
Host Species ◽  
Causal Agent ◽  
Global Distribution ◽  
Host Susceptibility ◽  
Pitch Canker ◽  
Fusarium Circinatum ◽  
Susceptible Host ◽  
Pinus Spp

Fusarium circinatum, the causal agent of pine pitch canker (PPC), is currently one of the most important threats of Pinus spp. globally. This pathogen is known in many pine-growing regions, including natural and planted forests, and can affect all life stages of trees, from emerging seedlings to mature trees. Despite the importance of PPC, the global distribution of F. circinatum is poorly documented, and this problem is also true of the hosts within countries that are affected. The aim of this study was to review the global distribution of F. circinatum, with a particular focus on Europe. We considered (1) the current and historical pathogen records, both positive and negative, based on confirmed reports from Europe and globally; (2) the genetic diversity and population structure of the pathogen; (3) the current distribution of PPC in Europe, comparing published models of predicted disease distribution; and (4) host susceptibility by reviewing literature and generating a comprehensive list of known hosts for the fungus. These data were collated from 41 countries and used to compile a specially constructed geo-database. A review of 6297 observation records showed that F. circinatum and the symptoms it causes on conifers occurred in 14 countries, including four in Europe, and is absent in 28 countries. Field observations and experimental data from 138 host species revealed 106 susceptible host species including 85 Pinus species, 6 non-pine tree species and 15 grass and herb species. Our data confirm that susceptibility to F. circinatum varies between different host species, tree ages and environmental characteristics. Knowledge on the geographic distribution, host range and the relative susceptibility of different hosts is essential for disease management, mitigation and containment strategies. The findings reported in this review will support countries that are currently free of F. circinatum in implementing effective procedures and restrictions and prevent further spread of the pathogen.

scholarly journals Between virus correlations in the outcome of infection across host species: evidence of virus genotype by host species interactions

2021 ◽  
Author(s):  
Ryan M. Imrie ◽  
Katherine E. Roberts ◽  
Ben Longdon
Keyword(s):  
Infectious Diseases ◽  
Host Species ◽  
Evolutionary Relationships ◽  
Susceptible Host ◽  
Transmission Rates ◽  
Host Shifts ◽  
Species Effects ◽  
Experimental Infections ◽  
Evolutionary Relatedness ◽  
Novel Host

AbstractVirus host shifts are a major source of outbreaks and emerging infectious diseases, and predicting the outcome of novel host and virus interactions remains a key challenge for virus research. The evolutionary relationships between host species can explain variation in transmission rates, virulence, and virus community composition between hosts, but the potential for different viruses to interact with host species effects has yet to be established. Here, we measure correlations in viral load of four Cripavirus isolates across experimental infections of 45 Drosophilidae host species. We find positive correlations between every pair of viruses tested, suggesting that broadly susceptible host clades could act as reservoirs and donors for certain types of viruses. Additionally, we find evidence of genotype-by-genotype interactions between viruses and host species, highlighting the importance of both host and virus traits in determining the outcome of virus host shifts. More closely related viruses tended to be more strongly correlated, providing tentative evidence that virus evolutionary relatedness may be a useful proxy for determining the likelihood of novel virus emergence, which warrants further research.Impact SummaryMany new infectious diseases are caused by viruses jumping into novel host species. Estimating the probability that jumps will occur, what the characteristics of new viruses will be, and how they are likely to evolve after jumping to new host species are major challenges. To solve these challenges, we require a detailed understanding of the interactions between different viruses and hosts, or metrics that can capture some of the variation in these interactions. Previous studies have shown that the evolutionary relationships between host species can be used to predict traits of infections in different hosts, including transmission rates and the damage caused by infection. However, the potential for different viruses to influence the patterns of these host species effects has yet to be determined. Here, we use four viruses of insects in experimental infections across 45 different fruit fly host species to begin to answer this question. We find similarities in the patterns of replication and persistence between all four viruses, suggesting susceptible groups of related hosts could act as reservoirs and donors for certain types of virus. However, we also find evidence that different virus genotypes interact in different ways with some host species. Viruses that were more closely related tended to behave in similar ways, and so we suggest that virus evolutionary relatedness may prove to be a useful metric for predicting the traits of novel infections and should be explored further in future studies.

scholarly journals Susceptibility of Selected Ericaceous Ornamental Host Species to Phytophthora ramorum

Plant Disease ◽  
2004 ◽  
Vol 88 (9) ◽  
pp. 993-999 ◽  
Author(s):  
P. W. Tooley ◽  
K. L. Kyde ◽  
L. Englander
Keyword(s):  
Mating Type ◽  
Host Species ◽  
The United States ◽  
Phytophthora Ramorum ◽  
Natural Conditions ◽  
Experimental Conditions ◽  
Susceptible Host ◽  
Disease Symptoms ◽  
Kalmia Latifolia ◽  
Mountain Laurel

We assessed disease reactions of 51 species or varieties of ericaceous ornamental hosts to two isolates of Phytophthora ramorum, the causal agent of sudden oak death. Inoculation was performed with an A2 mating type U.S. isolate from rhododendron and the P. ramorum type culture of A1 mating type from Germany. For only one host were statistically significant differences in disease observed between the two isolates. Several different inoculation methods were compared. The 51 hosts tested varied widely in susceptibility, ranging from 0% to over 90% leaf area infected. Two cultivars of Vaccinium macrocarpon (cranberry) showed no disease, while three cultivars of Kalmia latifolia (mountain laurel) were all highly susceptible. The results indicate that many ornamental hosts grown in the United States are susceptible to P. ramorum under artificial inoculation conditions. Inoculum density studies with two susceptible host species showed that P. ramorum is capable of producing disease symptoms over sporangium concentrations ranging from 100 to 5,000 sporangia per ml. Mean numbers of chlamydospores forming in host tissue of 21 hosts ranged from 2 to over 900 chlamydospores per 6-mm-diameter leaf disk. Whether hosts showing susceptiblity under the experimental conditions used in this study would become infected with P. ramorum in the presence of inoculum under natural conditions is unknown.

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