Information

Parasite - host equations

Parasite - host equations


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

The Lotka-Volterra equations describe how predator-prey interactions affect population growth. Do these equations describe parasite-host interactions? If not, how would they change by adding these interactions as well?


Parasite vs predators

In terms of ecological interaction, a parasite is essentially a predator. As such, of course the Lotka-Volterra equations apply to host-parasites interactions.

Lotka-Volterra equations

However, Lotka-Volterra equations are very simple and very general. So much so, that in order to make good prediction about the real world, one most often have to build more advanced models.

Host-parasite interaction models

There exist a whole set of models specific to host-parasite interactions. You should have a look at the wikipedia entry for epidemic model which is a pretty good overview and introduction.

Most models of host-parasite interactions fall into the category of the SIR (or SIRS and other derivatives) model. The term SIR comes from Susceptible-Infected-Recovered. The whole point of the SIR models is to categorize host individuals on whether they are Susceptible, Infected of Recovered (hence the abbreviation SIR).

The SIR models are very much used by national and international centers for epidemiology and underly many of the decisions of vaccination and other methods of disease control.

Host-parasite co-evolution

Of course, the Lotka-Volterra model and the SIR models assume absence of evolution and only track changes in population size (within each category for the SIR models). There are models that also take into account that populations also evolve in response to the interaction and demographic events that the interactions are causing. Such models are much more complicated to keep track of and we often (I think) make use of technics such as separation of time scales. These models are essential though typically for to control viral epidemic but not only. But these models are outside the scope of your question.


The evolution of parasite host range in heterogeneous host populations

Amanda K. Gibson, Department of Biology, University of Virginia, Charlottesville, VA 22902, USA.

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, University of Virginia, Charlottesville, VA, USA

Amanda K. Gibson, Department of Biology, University of Virginia, Charlottesville, VA 22902, USA.

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Department of Biology, Emory University, Atlanta, GA, USA

Institutional Login
Log in to Wiley Online Library

If you have previously obtained access with your personal account, please log in.

Purchase Instant Access
  • View the article PDF and any associated supplements and figures for a period of 48 hours.
  • Article can not be printed.
  • Article can not be downloaded.
  • Article can not be redistributed.
  • Unlimited viewing of the article PDF and any associated supplements and figures.
  • Article can not be printed.
  • Article can not be downloaded.
  • Article can not be redistributed.
  • Unlimited viewing of the article/chapter PDF and any associated supplements and figures.
  • Article/chapter can be printed.
  • Article/chapter can be downloaded.
  • Article/chapter can not be redistributed.

Abstract

Theory on the evolution of niche width argues that resource heterogeneity selects for niche breadth. For parasites, this theory predicts that parasite populations will evolve, or maintain, broader host ranges when selected in genetically diverse host populations relative to homogeneous host populations. To test this prediction, we selected the bacterial parasite Serratia marcescens to kill Caenorhabditis elegans in populations that were genetically heterogeneous (50% mix of two experimental genotypes) or homogeneous (100% of either genotype). After 20 rounds of selection, we compared the host range of selected parasites by measuring parasite fitness (i.e. virulence, the selected fitness trait) on the two focal host genotypes and on a novel host genotype. As predicted, heterogeneous host populations selected for parasites with a broader host range: these parasite populations gained or maintained virulence on all host genotypes. This result contrasted with selection in homogeneous populations of one host genotype. Here, host range contracted, with parasite populations gaining virulence on the focal host genotype and losing virulence on the novel host genotype. This pattern was not, however, repeated with selection in homogeneous populations of the second host genotype: these parasite populations did not gain virulence on the focal host genotype, nor did they lose virulence on the novel host genotype. Our results indicate that host heterogeneity can maintain broader host ranges in parasite populations. Individual host genotypes, however, vary in the degree to which they select for specialization in parasite populations.

Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.


Anderson, R. M., May R. M.: Coevolution of hosts and parasites, Preprint

Beck, K. C., Keener, J. P., Ricciardi, P.: The effect of epidemics on genetic evolution. J. Math. Biol. (1983)

Gillespie, J. H.: Natural selection for resistance to epidemics. Ecology 56, 493–495 (1975)

Hoppensteadt, F. C.: Singular perturbations on the infinite interval. Trans. Amer. Math. Soc. 123, 521–535 (1966)

Kemper, J. T.: The evolutionary effect of endemic infectious disease. Preprint

Levin, S. A.: Some approaches to the modelling of coevolutionary interactions. Coevolution. Chicago: U. Chicago Press, in press

Levin, S. A., Pimental, D.: Selection of intermediate rates of increase in parasite-host systems. Am. Nat. 117, 308–315 (1981)

Levin, S. A., Udovic, J. D.: A mathematical model of coevolving populations. Am. Nat. 111, 657–675 (1977)

Lewis, J. W.: On the coevolution of pathogen and host, in two parts. J. Theoret. Biology 93 927–985 (1981)

Saunders, I. W.: Epidemics in competition. J. Math. Biol. 11, 311–318, (1981)


The Effect of Parasites on Host Population Density and Extinction: Experimental Epidemiology with Daphnia and Six Microparasites

Parasites have been shown to reduce host density and to induce host population extinction in some cases but not in others. Epidemiological models suggest that variable effects of parasites on individual hosts can explain this variability on the population level. Here, we aim to support this hypothesis with a specific epidemiological model using a cross‐parasite species approach. We compared the effect of six parasites on host fecundity and survival to their effects on density and risk of extinction of clonal host populations. We contrast our empirical results of population density with predictions from a deterministic model and contrast our empirical results of host and parasite extinction rates with those predicted by a stochastic model. Five horizontally transmitted microparasites (two bacteria: white bacterial disease, Pasteuria ramosa two microsporidia: Glugoides intestinalis, Ordospora colligata one fungus: Metschnikowiella biscuspidata) and six strains of a vertically transmitted microsporidium (Flabelliforma magnivora) of the planktonic crustacean Daphnia magna were used. In life table experiments, we quantified fecundity and survival in individual parasitized and healthy hosts and compared these with the effect of the parasites on host population density and on the likelihood of host population extinction in microcosm populations. Parasite species varied strongly in their effects on host fecundity, host survival, host density reduction, and the frequency with which they drove host populations to extinction. The fewer offspring an infected host produced, the lower the density of an infected host population. This effect on host density was relatively stronger for the vertically transmitted parasite strains than for the horizontally transmitted parasites. As predicted by the stochastic simulations, strong effects of a parasite on individual host survival and fecundity increased the risk of host population extinction. The same was true for parasite extinctions. Our results have implications for the use of microparasites in biological control programs and for the role parasites play in driving small populations to extinction.


What are parasitic plants explain with an example

Parasitic plants are those plants which are obtaining their nutrition, food, minerals and water from another plant known as host through special specialised pennetrating organ name haustarium, without contributing to the benefit of the host, and in some cases it causing extreme damage to the host.

Define structural features of parasitic plant in the presence of haustaria that is modified part of roots of parasitic plants is specialised organ that penetrates the host and make connection with xylem and phloem, a vascular union between the plants and absorb prepared food, nutrients, minerals and water from host plants without contributing to the benefit of the host and in some cases it causing extreme damage to the host plant.

Parasitic plants differ from others plants such as climbing vines, Lianas, aerophyte and epiphyte, all these are supported by other plant and it is not in parasitic in nature.

Santalum album, Rafflesia, Orbanche, Viscum, Cuscuta, Loranthus, Striga and Thesium are well known examples of parasitic plants. Rafflesia and Orbanche are total root parasite, Cuscuta is total stem parasite, Viscum and Loranthus are partial (semiparasite) stem parasite and Santalum album, Thesium and Striga are partial root parasite.

What are types of parasitic plants?

According to absorbing, nutrients, foods, minerals and water and connection with host plant parasitic plants categorised into two types- 1) holoparasite or total and 2) Partial or semiparasite.

What is holoparasite or total parasite? give examples

Holoparasite or total parasite:- holoparasite define as those parasitic plants which are non green, totally dependent on host for obtain their total food material including organic nutrients, water and minerals from the host body are called as holoparasites and they cannot survive without host. Cuscuta, Orobanche, Balanophora, Rafflesia are example of holoparasite.

What is semiparasite or partial parasite? give examples

Semiparasite or partial parasite :- semiparasite is define as those parasitic plants are green and can synthesise their own food but depend on host for absorption of minerals and water supply is known as semi parasite. So these types of parasitic plants partially dependent on other plant for making their own food. Loranthus, Santalum, Viscum, striga and Thesium are examples of semi or partial parasites

◆you should also visits our website https://biologysir.com and other website for civil engineer calculation at https://www.civilsir.com

According to nature of parasitic plants where they grew on stems or root, totaly dependent or partialy dependent, parasitic plants are categorised into 4 types:- 1) total stem parasite, 2) partial stem parasite, 3) total root parasite and 4) partial stem parasite

What is total stem parasite? give examples

Total stem parasite defined as those parasitic plant which are non green, rootless, grow on stem of host plant and totally dependent on host plant for food nutrition, minerals and water, all this make easy by special define structure known as haustaria that make vascular union between stem of host plant and parasitic plant. Cuscuta is well known example of total stem parasite

What is total root parasite? give examples

Total root parasite defined as those parasitic plants which are non green, rootless, grow on root of host plant and totally dependent on host plant for food nutrition, minerals and water, all this make easy by special define structure known as haustaria that make vascular union between root of host plant and parasitic plant. Rafflesia, Orbanche and Balanophora is well known example of total root parasite.

What is partial root parasite? give examples

Partial root parasite defined as those parasitic plants which are green, grow on root of host plant and partialy dependent on host plant for nutition, only absorb minerals and water. Santalum album, Striga and Thesium are well known example of partial root parasite.

What is partial stem parasite? give examples

Partial stem parasite defined as those parasitic plants which are green, grow on stem of host plant and partialy dependent on host plant for nutition, only absorb minerals and water. Viscum album and Loranthus are well known example of partial stem parasite.

What are parasitic plants? give examples

Parasitic plants are those plants which are obtaining their nutrition, food, minerals and water from another plant known as host through special specialised pennetrating organ name haustarium, without contributing to the benefit of the host, and in some cases it causing extreme damage to the host.

Santalum album, Rafflesia, Orbanche, Viscum, Cuscuta, Loranthus, Striga and Thesium are well known examples of parasitic plants. Rafflesia and Orbanche are total root parasite, Cuscuta is total stem parasite, Viscum and Loranthus are partial (semiparasite) stem parasite and Santalum album, Thesium and Striga are partial root parasite

What is example of parasitic plants?

Santalum album, Rafflesia, Orbanche, Viscum, Cuscuta, Loranthus, Striga and Thesium are well known examples of parasitic plants. Define structural features of parasitic plant is the presence of haustorium that make connection with xylem and phloem of host plant and absorb prepared food, nutrients, minerals and water from plants without contributing to the benefit of the host and in some cases it causing extreme damage to the host plant.

What is example of total root parasitic plant?

Example of total root parasite:– Rafflesia and Orbanche are example of total root parasite. It develop define structural features haustorium modified roots of parasitic plants that’s penetrating the roots of host that make connection with xylem and phloem of host plant and absorb prepared food, nutrients, minerals and water from host plants without contributing to the benefit of the host and in some cases it causing extreme damage to the host plant.

What is example of partial root parasitic plant?

Example of partial root parasite:– Santalum album, Striga and Thesium are example of partial (semi- parasite) root parasite. Santalum album is evergreen partial root parasite which grow in South India and it grow in roots of dalbergia Sisso and Eucalyptus. Striga grows on roots of sugarcane and Thesium on the roots of grasses. Partial root parasitic plant develop define structural features haustorium modified roots of parasitic plants that’s penetrating the roots of host that make connection with xylem of host plant and only absorb minerals and water from host plants without contributing to the benefit of the host.

What is example of total stem parasitic plant?

Example of total stem parasite:- Cuscuta is example of total stem parasite, it is rootless total stem parasite, yellow coloured, slender stem with small scale leaves, which twins around the host plant and define structural features haustorium of cuscuta that’s penetrating the stems of host that make connection with xylem and phloem of host plant and absorb prepared food, nutrients, minerals and water from host plants without contributing to the benefit of the host.

What is example of partial stem parasitic plant?

Example of partial stem parasite:- Viscum album (mistletoe) and Loranthus are example of partial (semi- parasite) stem parasite. Viscum album grow on number of shrubs and trees, it sends secondary haustarium with make connection with the xylem of host and absorb only Minerals and water.

Cuscuta total stem parasite

Cuscuta well known as Dodder, Amarbel, Akash bel is common example of total stem parasite. It is stem parasite of many Angiospermic plant like Zizyphus, Citrus, Duranta and Clover.

Seeds of Amarbel germinate in the soil seedlings are long filamentous and without cotyledons the young plants grow and perform circumutation or rotatory movement and they twin around the stem and sometime leaves of host plant. If the host plant is not available the young plant of amarbel will die. For the establishment contact with the host plant the young seedling develop obsorbing organ that is known as haustoria.

Haustoria is modified adventitious root which deeply penetrate into the body of host and vascular tissue of parasites make contact with that of host through these haustoria. The haustoria are metabolic active organs which help in absorption of nutrients and provide the channel for their transportation. When strong connection is established between Amarbel and host plant then mature plant loses its connection with the soil and become totally dependent on their host.

The mature plant of Amarbel is very long filamentous branched pale yellow in colour with small scaly leaves and it can produces bunches of white or pale yellow bell shaped flowers.

Viscum album partial stem parasite

Viscum is common example of partial stem parasite and their host plant is shrubs and fruit trees. The mature plant of Viscum is is branched with Green Leaves born in pairs attached on each node of stem. Shoot of Viscum is attached to the host by means of haustoria

There is two type of haustorium develop in viscum parasitic plant that is primary haustoria and secondary haustoria .The primary haustorium reaches up to cortex of the host and it sends secondary haustoria which make connection with xylem of host and absorb water and Minerals.

Orbanche total root parasite

Orobanche is common example of total root parasite and that parasitizes on the roots of many angiospermic plant such as mustard tomato potato brinjal. Orobanche parasitic plant have no chlorophyll and the flowers are pinkish or bluish in colour . The tips of roots make haustorial connection with the roots of host and absorb nourishment.

Rafflesia total root parasite

Rafflesia is common example of total root parasite and it has about 14 species commonly distributed in Indonesia and Myanmar. The vegetative parts of parasites are highly reduced and represented by cellular filament resembling fungal mycelium. These filaments are embedded in the soft tissue of post root such as Figs. While the flowers emerged out in the form of buds. The flowers of Rafflesia are the largest in the world and they are about 11 kg in weight and 1 metre in diameter.

Santalum sandal wood tree

Santalum album partial root parasite

Santalum album ( sandal wood tree ) is common example of partial root parasites and evergreen which grows at many places in South India. The young seedlings of santalum can grow independently upto year but not beyond that . within this period some of the roots develop haustoria which make contacts with the roots of nearby tree like Morinda, Dalbergia, Eucalyptus . They are normally green in colour but depend on host for water and mineral supply.


Neural parasitology: how parasites manipulate host behaviour

The ability of parasites to alter the behaviour of their hosts fascinates both scientists and non-scientists alike. One reason that this topic resonates with so many is that it touches on core philosophical issues such as the existence of free will. If the mind is merely a machine, then it can be controlled by any entity that understands the code and has access to the machinery.

This special issue of The Journal of Experimental Biology highlights some of the best-understood examples of parasite-induced changes in host brain and behaviour, encompassing both invertebrate and vertebrate hosts and micro- and macro-parasites. The observation that parasitic infection can modify specific host behaviours is an old one (see Moore, 2002). The general consensus has been that these parasites have evolved the ability to manipulate host behaviour in order to advance their own reproductive success (Moore, 2002). Unfortunately, there has been a lack of information on two key points of this hypothesis. Firstly, it has proved difficult to unequivocally demonstrate that changes in host behaviour benefit the parasite (i.e. enhance parasitic fitness). Secondly, the mechanisms that parasites use to change host behaviour were completely unknown for many years, particularly in the case of vertebrate host systems.

Undoubtedly, the design and interpretation of investigations in this field is hampered by our inadequate understanding of the physiological basis of ‘normal’ host behaviour, even when uninfected, making the identification of possible parasitic mechanisms difficult. Furthermore, distinguishing between parasitic and host effects on host behaviour is not straightforward. For example, infected animals, including humans, can exhibit a range of so-called general ‘sickness’ behaviours (Dantzer, 2001). These may reflect key adaptive responses of the host immune infection in an effort to combat or at least minimize the impact of infections. Under certain conditions, the same behavioural alterations observed may, however, be directly mediated or manipulated by the parasite itself to enhance transmission (Adamo, 2012). Furthermore, parasites may utilize the same or similar mechanistic routes to achieve their effect, thereby exacerbating the difficulties of distinguishing between the two. Finally, many cases of parasitic manipulation occur in host–parasite systems in which the host is not a typical model for behavioural neuroscience research. Work in these systems is therefore hindered by a lack of background information and species-specific neuroethological techniques and measurements. In other systems, even where information about the host is available, the experimental host may be exposed to unnaturally high parasite doses and/or unnatural laboratory-constrained research conditions. Such studies are thus often unrepresentative for monitoring the types of traits that may be under selection in the wild. Dealing with these methodological issues is a major focus of this special issue.

Joanne P. Webster is Professor of Parasite Epidemiology at the School of Public Health, Imperial College London, UK. Her research encompasses both T. gondii-altered host behaviour and also the epidemiology and control of a range of neglected tropical diseases across Africa and Asia. E-mail: [email protected]

Joanne P. Webster is Professor of Parasite Epidemiology at the School of Public Health, Imperial College London, UK. Her research encompasses both T. gondii-altered host behaviour and also the epidemiology and control of a range of neglected tropical diseases across Africa and Asia. E-mail: [email protected]

Shelley A. Adamo is a Killam Professor at Dalhousie University, Canada. Her expertise is in invertebrate behavioural physiology, and she is known for her studies on immune–behavioural interactions in insects. E-mail: [email protected]

Shelley A. Adamo is a Killam Professor at Dalhousie University, Canada. Her expertise is in invertebrate behavioural physiology, and she is known for her studies on immune–behavioural interactions in insects. E-mail: [email protected]

There has, nevertheless, been a leap in our understanding of parasitic manipulation over the past few years. Part of the advance has been due to recent developments in neuroscience and molecular technologies, and this special issue highlights these successes. However, it also demonstrates the need for a multi-disciplinary integration of studies concerning the molecular, biochemical and physiological aspects of infection with studies on the evolutionary, ecological and behavioural functions of host behavioural change.

How parasites manipulate their hosts is not an arcane topic, fascinating merely because it inspires the macabre (e.g. Schlozman, 2011). There are practical reasons for understanding how they exert their effects. Parasites are ubiquitous – and many have a predilection for the ‘immunologically privileged’ site of the central nervous system because it shelters them from the full fury of the host’s immune system (Galea et al., 2007). However, this location also provides a parasite with direct ‘access to the machinery’ to alter host behaviour. Classic examples include the protozoan Toxoplasma gondii, where parasite-induced changes in the behaviour of its rodent intermediate host appear to enhance transmission to the feline definitive host (Webster, 2007). What T. gondii does to manipulate its rodent host is highly germane, as it appears to be doing the same thing in human brains. Papers in this issue present evidence that T. gondii also alters human behaviour and may be involved in the etiology of serious mental disorders such as schizophrenia. The latter also highlights the utility of studying natural host–parasite manipulations as potential avenues for further research into animal models of specific human affective disorder symptoms. Unfortunately, however, the public health significance of such parasitic infections on the pathogenesis, prognosis, treatment and outcome of human disease, especially perhaps those of the brain and ‘mind’, is still underappreciated.

Parasites also provide a unique window into the functioning of the uninfected brain. Neurobiologists tend to manipulate a subject’s behaviour using approaches that target specific neural areas and/or specific neurotransmitter systems. Parasites use other, often multiple, mechanisms, far ‘sloppier’ in their neuroanatomical targets but still capable of precise behavioural control. Such multiple routes likely reflect that we are dealing with selection and evolution rather than ‘intelligent design’. Nevertheless, the multifaceted approach of parasites illustrates novel methods for altering brain and behaviour. Exploring these mechanisms will uncover previously unknown principles of neural control.

Thus, the research discussed in this special issue opens new opportunities for further research. One successful outcome of The Journal of Experimental Biology symposium (hosted by The Company of Biologists) that generated this special issue is the determination of many of the participants to carry out research that synthesizes information and approaches from multiple levels of analysis. We hope that this issue will help stimulate and foster further multi-disciplinary research and collaboration.


Selected Publications

Lokesh D. Kori, Neena Valecha and Anup R. Anvikar. (2020). Glutamate dehydrogenase: a novel candidate to diagnose Plasmodium falciparum through rapid diagnostic test in blood specimen from fever patients. Scientific Reports. 10 (6307).

Transcriptional modulation of the host immunity mediated by cytokines and transcriptional factors in Plasmodium falciparum infected patients of North-East India. MZ Ahmed, N Bhardwaj, S Sharma, V Pande and AR Anvikar . 2019 Biomolecules

Clinicopathological study of potential biomarkers of P. falciparum malaria severity and complications. N Bhardwaj, MZ Ahmed, S Sharma, B Srivastava, V Pande and AR Anvikar. 2019 Infection, Genetics and Evolution

Improved access to early diagnosis and complete treatment of malaria in Odisha, India. Pradhan S, Pradhan MM, Dutta A, Shah NK, Joshi PL, Pradhan K, Sharma SK, Grewal Daumerie P, Banerji J, Duparc S, Mendis K, Murugasampillay S, Valecha N, Anvikar AR. PLoS One 2019 Jan 2 14(1) e0208943

Epidemiology of Plasmodium vivax Malaria in India. Anvikar AR, Shah N, Dhariwal AC, Sonal GS, Pradhan MM, Ghosh SK, Valecha N. Am J Trop Med Hyg. 201695(6 Suppl):108-120.

Genetic deletion of HRP2 and HRP3 in Indian P. falciparum population and false negative malaria rapid diagnostic test. Navin Kumar, Veena Pande, R. M. Bhatt, Naman K Shah, Neelima Mishra, Bina Srivastava, Neena Valecha, Anupkumar R. Anvikar. Acta Tropica 2013125(1):119-21.


GRC Biology of Host-Parasite Interactions

After a somewhat stressful journey with a bit too many too-close-for-comfort connections between flights and shuttle buses, it looks like I will actually make it in time to Newport, RI for another GRC conference on the “Biology of Host-Parasite Interactions”. It’s been 2 years since the last meeting, and just like last time, this year’s schedule looks packed with great parasitology talks ranging from parasite cell biology to disease transmission and control, featuring a wide cast not restricted to Plasmodium and Trypanosomes. As I can’t really bare to watch another movie (it’s been a long day!) and the internet in the shuttle isn’t really fast enough to work a little, I found myself with a little free time on the bus journey from Boston to Newport and felt this would be a nice chance to go over how parasitology has been represented in our pages since the last meeting. This is by no means an exhaustive analysis, but I think I’ve listed pretty much every paper we published over the last couple of years below, and there are a few interesting things that jump out:

  • Nature Microbiology published 24 parasitology articlesover the last 24 months (23 research articles and 1 review), for the nice round average of 1 paper / month. We don’t have quotas for different subjects at the journal but try to make sure that all areas of microbiology are represented in our pages, so it’s nice to think that our readers open our table of contents to find at least one parasitology paper each month that may spark their interest.
  • The papers published feature a wide array of parasites, and although Plasmodium (11 articles) and Trypanosomes (x5) clearly dominate the list, we’ve also featured Toxoplasma (x2), Onchocerca (x2), Leishmania, Babesia and microsporidia.
  • We've featured a vast range of topics, from genomics and evolution to pathogenesis, from cellular and molecular biology to drugs and drug resistance, from structural biology to disease transmission (see below for a more detailed list).
  • Parasites made the cover 5 times over the last 2 years, including some really cool visual representations of Onchocerca genomes, a colorful view of Plasmodium DNA replication, striking EM images of Trypanosomes and Leishmania parasites, and in the form of ape hosts (in a cover that may feature one of our favourite set of cover words ever, in the form of the punny “Plasmodium of the apes”, courtesy of our editor Emily White).

It’s hard to do each of these papers justice in a short blog post, so I’ll leave them just as a list organized by topic and hope that at least some of those titles will inspire you to read some of them in a bit more detail – they’re certainly worth the time. It’s also tough to cover just a few of them in a bit more detail without seeming to be picking favorites, so I won’t do it – just like any parent, I’m proud of all the parasitology papers we publish in our pages. So I’ll just finish with the wish that in two years’ time the list will be at least as long as the current one and filled with amazing stories as this one is. In the meantime, I’m very much looking forward to what looks like a great meeting over the next few days – and if you see me around, please stop and say hi (and maybe tell me which is your favourite piece).


Parasite - host equations - Biology

Biology of Pediculus

Figure 1: Pediculus humanus. Illustration by Sharon Belkin. Garcia 547. Figure 2: Phthirus pubis. Illustration by Sharon Belkin. Garcia 548. Figure 3: Louse egg (nit) on hair shaft. Photograph by Duane J. Gubler, CDC. Garcia 548.

Agents:
Pediculosis is caused by organisms of the phylum Arthropoda, class Insecta, order Anoplura (blood-sucking lice) and genus Pediculus. The three species that commonly infest humans are Pediculus humanus capitus or head lice, Pediculus humanus humanus or body lice, and Phthirus pubis or pubic lice, also known as crabs.

Morphology:
Lice are visible to the naked eye, with P. humanus 2-4 mm long (see Figure 1) and P.pubis 1mm long (see Figure 2). The lice are flattened dorsoventrally, and are characterized by legs with claws adapted for clinging to hairs and fibers on the body of the host, as well as mouth parts used for piercing the skin of the host to attach to it to suck blood. Lice are wingless, so they can only be transmitted from host to host via direct contact. The eggs laid by the female louse are oval shaped (see Figure 3) and attached to the hair shaft of the host.

Life Cycle:
The adult louse attaches to the skin via its mouthparts and sucks blood from the host to feed itself. Female lice lay eggs at the base of the hair shaft for up to 30 days, though few live that long, and then die. In body lice and head lice, females can lay six to eight eggs per day, and the eggs take on average 7 days to hatch and then another 7 days to reach sexual maturity. If they do not hatch within 20 days the eggs die. Female pubic lice lay about five eggs per day. Egg hatching requires 8 days and then it takes another 8 days for the louse to reach maturity. Adult pubic lice live three weeks longer than body or head lice.
Therefore the incubation period for the infestation is highly variable, as adult lice may be noticed as early as five days after infestation or as late as three weeks later.

Transmission:
Transmission of Pediculosis can only occur through parasite transfer from host to host through direct body contact with lice or lice eggs (nits) on bodies, clothing or personal articles. P. pubis are transmitted through sexual contact or other contact with infested external genitalia. Lice are host specific, and can only survive on the host and briefly (up to one week) in the environment. Head and pubic lice deposit and cement nits onto the hair shaft on the scalp or pubic area, while the body louse deposits eggs primarily on the seams of clothing. Contact with these eggs can also spread the infestation.
Reservoir: There is no reservoir for Pediculus other than humans because the lice are host-dependent (they cannot survive long in the environment) and host-specific (there are several types of animal lice as well but they do not typically affect humans).
•Vector: There is no vector for Pediculus because they are transmitted via direct contact. However, the body lice themselves are vectors of louse-borne relapsing fever (Borrelia recurrentis) and louse-borne typhus (Rickettsia prowazeki, R. quintana). Lice become infected when they feed off the blood of a person infected with either relapsing fever or typhus. The infected louse dislikes the intense heat of the fevered body, so leaves the infected person and movees to a new host, where it deposist the parasites on the body of the new hosts through fecal matter excreted as it feeds on the new host. This fecal matter is rubbed into the skin by scratching, and thus the B. recurrentis and Rickettsia parasites are able to enter the new host's body and infect him.


All Science Journal Classification (ASJC) codes

  • APA
  • Author
  • BIBTEX
  • Harvard
  • Standard
  • RIS
  • Vancouver

In: Quarterly Review of Biology , Vol. 63, No. 2, 01.01.1988, p. 139-165.

Research output : Contribution to journal › Article › peer-review

T1 - The population biology of parasite-induced changes in host behavior

N2 - Although changes in the behavior of infected hosts do occur for pathogens with direct life cycles, they are most commonly recorded in the intermediate hosts of parasites with complex life cycles. All the changes in host behavior serve to increase rates of transmission of the parasites between hosts. In the simplest case the changes in behavior increase rates of contact between infected and susceptible conspecific hosts in more complex cases fairly sophisticated manipulations of the host's behavioral repertory are achieved. Three topics are dealt with in detail: 1) behavior of the insect vectors of such diseases as malaria and trypanosomiasis 2) intermediate host of helminths whose behavior is affected in such a way as to make them more susceptible to predation by the definitive host in the life cycle and 3) behavior and fecundity of molluscs infected with asexually reproducing parasitic flatworms. In each case an expression is derived for R0, the basic reproductive rate of the parasite when first introduced into the population. This is used to determine the threshold numbers of definitive and intermediate hosts needed to maintain a population of the pathogen. In all cases, parasite-induced changes in host behavior tend to increase R0 and reduce the threshold number of hosts required to sustain the infection. The population dynamics of the interaction between parasites and their hots are then explored using phase plane analyses. This suggests that both the parasite and intermediate host populations may show oscillatory patterns of abundance. Both asexual reproduction of the parasite within a host and parasite-induced reduction in host fecundity may be stabilizing mechanisms when they occur in the intermediate hosts of parasite species with indirect life cycles. -from Author

AB - Although changes in the behavior of infected hosts do occur for pathogens with direct life cycles, they are most commonly recorded in the intermediate hosts of parasites with complex life cycles. All the changes in host behavior serve to increase rates of transmission of the parasites between hosts. In the simplest case the changes in behavior increase rates of contact between infected and susceptible conspecific hosts in more complex cases fairly sophisticated manipulations of the host's behavioral repertory are achieved. Three topics are dealt with in detail: 1) behavior of the insect vectors of such diseases as malaria and trypanosomiasis 2) intermediate host of helminths whose behavior is affected in such a way as to make them more susceptible to predation by the definitive host in the life cycle and 3) behavior and fecundity of molluscs infected with asexually reproducing parasitic flatworms. In each case an expression is derived for R0, the basic reproductive rate of the parasite when first introduced into the population. This is used to determine the threshold numbers of definitive and intermediate hosts needed to maintain a population of the pathogen. In all cases, parasite-induced changes in host behavior tend to increase R0 and reduce the threshold number of hosts required to sustain the infection. The population dynamics of the interaction between parasites and their hots are then explored using phase plane analyses. This suggests that both the parasite and intermediate host populations may show oscillatory patterns of abundance. Both asexual reproduction of the parasite within a host and parasite-induced reduction in host fecundity may be stabilizing mechanisms when they occur in the intermediate hosts of parasite species with indirect life cycles. -from Author


Watch the video: ΒΟΤΑΝΟΘΕΡΑΠΕΙΑ 150118 - ΠΑΡΑΣΙΤΑΣΚΟΥΛΙΚΙΑΤΟΞΙΝΕΣ ΣΤΑ ΕΝΤΕΡΑ ΚΑΙ ΛΕΜΦΙΚΟ ΣΥΣΤΗΜΑ ΑΝΑΛΥΣΗΘΕΡΑΠΕΙΑ (October 2022).