Specificity

2021 ◽  
pp. 159-182
Author(s):  
Paul Schmid-Hempel
Keyword(s):  
Host Range ◽  
Host Species ◽  
Cross Reactivity ◽  
Geographical Range ◽  
Immune Memory ◽  
Phylogenetic Distance ◽  
Immune Priming ◽  
Number Of Factors ◽  
Ecological Filter ◽  
Immune Defences

infect a number of host species. This host range is given by an ecological filter (the possibility of encounter) and a physiological one (the capacity of establishing an infection). Host ranges typically are right-skewed, with most parasites infecting only a few, but few infecting very many hosts. There is no universally valid hypothesis that explains host range. However, a number of factors contribute to host range, such as geographical range, phylogenetic distance, host predictability, and parasite virulence. Specificity and cross-reactivity of immune defences are important mechanisms. Moreover, immune memory is based on specificity; transgenerational immune priming protects offspring when parents have already been exposed to the same or similar parasites.

scholarly journals Phylogenetic aggregation increases zoonotic potential of mammalian viruses

2019 ◽  
Vol 15 (12) ◽  
pp. 20190668 ◽  
Author(s):  
Andrew W. Park
Keyword(s):  
Host Range ◽  
Host Species ◽  
Phylogenetic Relationships ◽  
Zoonotic Potential ◽  
Phylogenetic Distance ◽  
Wild Mammals ◽  
High Fitness

While many viruses of wild mammals are capable of infecting humans, our understanding of zoonotic potential is incomplete. Viruses vary in their degree of generalism, characterized by the phylogenetic relationships of their hosts. Among the dimensions of this phylogenetic landscape, phylogenetic aggregation, which is largely overlooked in studies of parasite host range, emerges in this study as a key predictor of zoonotic status of viruses. Plausibly, viruses that exhibit aggregation, typified by discrete clusters of related host species, may (i) have been able to close the phylogenetic distance to humans, (ii) have subsequently acquired an epidemiologically relevant host and (iii) exhibit relatively high fitness in realized host communities, which are frequently phylogenetically aggregated. These mechanisms associated with phylogenetic aggregation may help explain why correlated fundamental traits, such as the ability of viruses to replicate in the cytoplasm, are associated with zoonoses.

scholarly journals The phylogenetic range of bacterial and viral pathogens of vertebrates

2019 ◽  
Author(s):  
Liam P. Shaw ◽  
Alethea D. Wang ◽  
David Dylus ◽  
Magda Meier ◽  
Grega Pogacnik ◽  
...  
Keyword(s):  
Host Range ◽  
Host Species ◽  
Research Effort ◽  
Quantitative Measure ◽  
Zoonotic Potential ◽  
Phylogenetic Distance ◽  
Human Pathogens ◽  
Viral Pathogens ◽  
Host Pathogen ◽  
Single Host

AbstractMany major human pathogens are multi-host pathogens, able to infect other vertebrate species. Describing the general patterns of host-pathogen associations across pathogen taxa is therefore important to understand risk factors for human disease emergence. However, there is a lack of comprehensive curated databases for this purpose, with most previous efforts focusing on viruses. Here, we report the largest manually compiled host-pathogen association database, covering 2,595 bacteria and viruses infecting 2,656 vertebrate hosts. We also build a tree for host species using nine mitochondrial genes, giving a quantitative measure of the phylogenetic similarity of hosts. We find that the majority of bacteria and viruses are specialists infecting only a single host species, with bacteria having a significantly higher proportion of specialists compared to viruses. Conversely, multi-host viruses have a more restricted host range than multi-host bacteria. We perform multiple analyses of factors associated with pathogen richness per host species and the pathogen traits associated with greater host range and zoonotic potential. We show that factors previously identified as important for zoonotic potential in viruses—such as phylogenetic range, research effort, and being vector-borne—are also predictive in bacteria. We find that the fraction of pathogens shared between two hosts decreases with the phylogenetic distance between them. Our results suggest that host phylogenetic similarity is the primary factor for host-switching in pathogens.

scholarly journals Experimental evolution of insect immune memory versus pathogen resistance

2017 ◽  
Vol 284 (1869) ◽  
pp. 20171583 ◽  
Author(s):  
Imroze Khan ◽  
Arun Prakash ◽  
Deepa Agashe
Keyword(s):  
Secondary Infection ◽  
Pathogen Resistance ◽  
Immune Memory ◽  
High Dose ◽  
Basal Resistance ◽  
Immune Priming ◽  
Resistance To Infection ◽  
Empirical Tests ◽  
Rapid Modulation ◽  
Specific Priming

Under strong pathogen pressure, insects often evolve resistance to infection. Many insects are also protected via immune memory (immune priming), whereby sublethal exposure to a pathogen enhances survival after secondary infection. Theory predicts that immune memory should evolve when the pathogen is highly virulent, or when pathogen exposure is relatively rare. However, there are no empirical tests of these hypotheses, and the adaptive benefits of immune memory relative to direct resistance against a pathogen are poorly understood. To determine the selective pressures and ecological conditions that shape immune evolution, we imposed strong pathogen selection on flour beetle ( Tribolium castaneum ) populations, infecting them with Bacillus thuringiensis (Bt) for 11 generations. Populations injected first with heat-killed and then live Bt evolved high basal resistance against multiple Bt strains. By contrast, populations injected only with a high dose of live Bt evolved a less effective but strain-specific priming response. Control populations injected with heat-killed Bt did not evolve priming; and in the ancestor, priming was effective only against a low Bt dose. Intriguingly, one replicate population first evolved priming and subsequently evolved basal resistance, suggesting the potential for dynamic evolution of different immune strategies. Our work is the first report showing that pathogens can select for rapid modulation of insect priming ability, allowing hosts to evolve divergent immune strategies (generalized resistance versus specific immune memory) with potentially distinct mechanisms.

Host Range of Some Eucalypt Mycorrhizal Fungi

1973 ◽  
Vol 21 (1) ◽  
pp. 103 ◽  
Author(s):  
GA Chilvers
Keyword(s):  
Host Range ◽  
Host Species ◽  
Mycorrhizal Fungi ◽  
Wide Range ◽  
Genus Eucalyptus

Various fungi are shown to form mycorrhizas with a wide range of host species within the genus Eucalyptus. In general, the same fungi do not appear to be capable of forming mycorrhizas with Pinus.

WHY DO INSECTS EVOLVE IMMUNE PRIMING? A SEARCH FOR CROSSROADS

2021 ◽  
Author(s):  
Arun Prakash ◽  
imroze khan
Keyword(s):  
Immune Responses ◽  
Low Dose ◽  
Immune Memory ◽  
Comparative Approach ◽  
Future Research ◽  
Subsequent Infection ◽  
Immune Priming ◽  
Trade Offs ◽  
Evolutionary Response ◽  
Basal Immunity

Until recently, it was assumed that insects lack immune memory since they do not have vertebrate-like specialized memory cells. Therefore, their most well studied evolutionary response against pathogens was increased basal immunity. However, growing evidence suggests that many insects also exhibit a form of immune memory (immune priming), where prior exposure to a low dose of infection confers protection against subsequent infection by the same pathogen that acts both within and across generations. Most strikingly, they can rapidly evolve as a highly parallel and mutually exclusive strategy from basal immunity, under different selective conditions and with divergent evolutionary trade-offs. However, the relative importance of priming as an optimal immune strategy also has contradictions, primarily because supporting mechanisms are still unclear. In this review, we adopt a comparative approach to highlight several emerging evolutionary, ecological and mechanistic features of priming vs basal immune responses that warrant immediate attention for future research.

The natural history of defences

2021 ◽  
pp. 51-108
Author(s):  
Paul Schmid-Hempel
Keyword(s):  
Innate Immunity ◽  
Natural History ◽  
Adaptive Immunity ◽  
Immune Memory ◽  
History Of ◽  
Molecular Backbone ◽  
Somatic Diversification ◽  
Signalling Compounds ◽  
Immune Defences ◽  
Signalling Cascade

Hosts can avoid infections by behavioural changes and by body walls. After infection, hosts can change their behaviours to reduce the effects of parasitism. Immune defences have different arms (humoral or cellular), and organization (innate, adaptive). Innate immunity consists of a collection of different systems that are evolutionarily very old. Adaptive immunity, based on expansion of specific lymphocytes, evolved in the higher vertebrates. Immune defences are regulated tightly and based on receptors that can recognize parasites (or their activity). This triggers a complex signalling cascade that results in the production of further signalling compounds and effectors. Important protein families, e.g. the immunoglobulins, form the molecular backbone. A key to efficient defences is the diversification of receptors, such as the highly evolved somatic diversification processes of advanced adaptive immunity. The microbiota adds to defences in many ways. Immune memory and priming occur throughout the tree of life.

Nematodes and cestodes of rodents in South Africa: baseline data on diversity and geographic distribution

2019 ◽  
Vol 94 ◽  
Author(s):  
A. Spickett ◽  
K. Junker ◽  
G. Froeschke ◽  
V. Haukisalmi ◽  
S. Matthee
Keyword(s):  
South Africa ◽  
Host Range ◽  
Geographic Distribution ◽  
Host Species ◽  
Baseline Data ◽  
Helminth Species ◽  
Rodent Species ◽  
Helminth Parasites ◽  
Gastrointestinal Helminths ◽  
Naturally Occurring

Abstract Currently, descriptive information on the host range and geographic distribution of helminth parasites associated with naturally occurring rodents in South and southern Africa is scant. Therefore, we embarked on a countrywide study to: (1) identify gastrointestinal helminths and their host range, and (2) provide baseline data on the geographic distribution of helminths across the country. Altogether, 55 helminth taxa were recovered from at least 13 rodent species (n = 1030) at 26 localities across South Africa. The helminth taxa represented 25 genera (15 nematodes, nine cestodes and one acanthocephalan). Monoxenous nematodes were the most abundant and prevalent group, while the occurrence of heteroxenous nematodes and cestodes was generally lower. The study recorded several novel helminth–host associations. Single-host-species infections were common, although multiple-host-species infections by helminth species were also recorded. Monoxenous nematodes and some cestodes were recovered countrywide, whereas heteroxenous nematodes were restricted to the eastern regions of South Africa. The study highlights the as yet unexplored diversity of helminth species associated with naturally occurring rodent species and provides initial data on their geographical distribution in South Africa.

Host range and geographic distribution of Armillaria root rot pathogens in the Canadian prairie provinces

1990 ◽  
Vol 20 (12) ◽  
pp. 1859-1863 ◽  
Author(s):  
K. I. Mallett
Keyword(s):  
Host Range ◽  
Geographic Distribution ◽  
Host Species ◽  
Root Rot ◽  
Boreal Forests ◽  
Common Species ◽  
Canadian Prairie ◽  
Armillaria Root Rot ◽  
Armillaria Species ◽  
Prairie Provinces

A survey to identify Armillaria root rot pathogens, their host range, and geographic distribution was conducted in the Canadian prairie provinces. Collections of basidiocarps and isolates from the wood of gymptomatic or dead trees were made. Armillaria species were identified by interfertility testing and by the L-DOPA method. Three Armillaria species, A. ostoyae (Romagn.) Herink, A. sinapina Bérubé & Dessureault, and A. calvescens Bérubé & Dessureault, were identified. Armillariaostoyae was the most common species in both the subalpine and boreal forests and was found on a wide variety of coniferous and deciduous host species. Armillariasinapina was in both the boreal and subalpine forests but occurred primarily on deciduous host species. Armillariacalvescens was rare and was found only in the boreal forest on both coniferous and deciduous host species.

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.

Sign in / Sign up

Export Citation Format

Share Document