VET278 Lecture Notes on Parasite Taxonomy PDF

VET278 Lecture notes Parasite taxonomy; **What is the basis for classification?** Process of placing organisms in groups (taxa) based on their phylogenetic relationships - Morphology (how they look embryo, lava, adult, development, structural) - Molecular relationships Genus and specie...

VET278 Lecture notes Parasite taxonomy; **What is the basis for classification?** Process of placing organisms in groups (taxa) based on their phylogenetic relationships - Morphology (how they look embryo, lava, adult, development, structural) - Molecular relationships Genus and species always in italics Keep, Ponds, Clear Or Frogs Get Sick Kinky People Come Over For Good Sex **Parasite Taxa:** Arisen independently, from many ancestors **Kingdom**: Protista: Phyla; Sacromastigophora, Cliliophora, Apicomplexa) **Phylum** Platyhelminthes : Classes: Mongenea, Trematoda, Cestoda **Phylum**: Acanthocephala **Phylum**: Nemathelminthes: Class Nematoda **Phylum**: Arthopoda; Class: Insecta, Arachnida, Crustacea Protozoans: What? Small single celled organisms, extracellular or intracellular -------- --------------------------------------------------------------- Where? Tissue, blood, GI tract What is taxonomic hierarchy? What is basic characteristics are used to differentiate major parasitic phyla? **Platyhelminthes:** "flat worm" - Soft bodied - Acoelomate - Usually dorso ventrally flattened - Gut incomplete or absent - Mostly hermaphroditic - Attachment organs (suckers, hooks or spines) - Complex lifecycles with at least two host species - Classes: Monogenea, Trematoda and cestoda - +-----------------------------------+-----------------------------------+ | **Trematodes:** |  | | | | | "flukes" | | | | | | Class; Mongenea or class | | | Trematoda. | | | | | | Mostly leak like, simple gut | | | | | | Ectoparasitic: Mongenea (fish) | | | | | | Endoparastic: Trematoda | | +===================================+===================================+ | **Cestodes** |  | | | | | "tapeworms" | | | | | | Long segmented, ribbon like | | | structure | | | | | | Attachment: suckers and or hooks | | | | | | Two hosts, lava and adult | | | (predator and prey - | | | intermediate) | | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | |  Nematodes | | | in medical research | +===================================+===================================+ | **Protista: Phylum | | | Sacaromastigophora** | | +-----------------------------------+-----------------------------------+ | Subphylum Mastigophora | Subphylum Sarodina | +-----------------------------------+-----------------------------------+ | Mastio (whip) phora (bearing) | Pseudopodia, used for locomotion | | | and food capture "amoebae" (false | | One or more | feet) | | flagella used for locomotion | | | "flagellates" | Incyst for protection -forming | | | the yellow complex above | | Ie//Giardia (left) trypanosoma | | | (right) | | +-----------------------------------+-----------------------------------+ | **Phylum Ciliophora** | **Phylum Apicomplexa** | +-----------------------------------+-----------------------------------+ | 'Ciliates" | Class: Sporozoa | | | | | Process 2 nuclei | - Cell penetration (apical | | | complex) | | Cilia used for locomotion and | | | capture food | - Mostly intracellular | | | | | Macro and mirco nucleus | | | | | | Incyst | | +-----------------------------------+-----------------------------------+ | Order Eucoccidia | Order Haemosporina | | | | | Suborder Eimeriina: Intracellular | Mostly parasties of the blood | | parasites of intestinal | "Plasmodium" | | epithelium, liver kindneys and | | | muscles | Order Piroplasmida | | | | | CNS Coccidia | Small blood parasites | +-----------------------------------+-----------------------------------+ | | | +-----------------------------------+-----------------------------------+ **Phylum Acanthocephala** Thorn and head - Long thing worms - Body cavidty - No gut - Anterior spiny holdfast   +-----------------------------------+-----------------------------------+ |  | Ticks can be permanent but mostly | | | 3 Host temperory; hard outter | | Lice are permanent cannot live | shell males is bigger, female are | | without the host | bigger blood takers | | | | | | Mites: | +-----------------------------------+-----------------------------------+  **Host/parasite coevolution: the shared history of parasites and hosts** **Explain what is meant by the terms coevolution, cospeciation and coadaptation** **Coevolution**: Process by which two or more species (ie// host and parasite) reciprocally affect each other's evolution Ie// Between pollinator and plant, predator and prey and parasite and host as well as choosiness to select against virulence factors **Cospeciation:** Process by which speciation of host is accompanied by the speciation of parasite- produces congruent evolutionary trees Ie// lice on an dog jumping onto another dog whilst they are mating. - Pocket golfers and chewing lice **Farenholz's rule**: phylogeny of a parasite group parallels the phylogeny of its host group - It depends on the relative frequency of cospeciation compared to other processes such as host switching, such as lineage, extinction, and unilateral speciation. **Coadaptation**: Evolution of adaptions in the host in response to selection imposed by a parasite, followed by the evolution of adaption in the parasite in response to reciprocal selection imposed by the host. **Coadaptation** = evolutionary arms race (red queen hypothesis) -- maintain the balance between defence and offense Ie// lice in birds, (feather lice) white species on cockatoos and black on black cockatoos for body lice. Inferring that colouration is to blend in. Ie// trypanosomes t.b brucei cattle only affecting not humen due to APOL1 protein that kills the trypanosomes. T.B rhodesiense that causes sleeping sickness adapted so can infect humans. **Local adaptation** = ability of parasites to perform better on hosts from the same geographic area - Local adaptation is favoured by shorter generation time and greater fecundity of parasites relative to hosts - IE// fish from Germany or Sweden or Denmark infect fish within their geography more consistently. **Describe the difference between parasite virulence, infectivity and pathogenicity** **Infectivity:** Encounter filter: excludes all host species that the parasite cannot meet for ecological or behavioural reasons [Compatibility filter:] getting in the host, host immune response, or morphological response physiological response - Ectoparasite live in immunological site are at least risk of being harmed by the body - Internal ones are at the mercy of host of the immune system. *Specialist parasite*; one species or similar high host specificity (depend on stage of life?) - They are well-adapted to their hosts but can't usually exploit other hosts - Endangered host species are unlikely to be threatened by the specialist parasites *Generalists*: infect whatever they can ie// Toxoplasma gondii - May be out-competed by specialists but can exploit alternative hosts - 60% human parasites are generalists - 80% animal parasites due to generalist parasites *Host* *range*: number of species used at each stage of lifecycle [What determines pathogenicity?] 1. Parasite replication (faster rep = bigger pop) 2. Parasite activity (browsing food or taking blood) 3. Host response (inflammatory reaction and have negative affects, worst affects are due to what the host does to itself in defense) 4. Exogenous (environmental) facts (aquaculture, bacterial and protozoan **Explain, using examples, how a trade off between virulence and transmission affects the evolution of parasite virulence** - Virulence often greater in water-borne parasites than in those that rely on direct host to host contact : - - Virulence often greater in intermediate hosts than in definitive hosts when transmission depends on the intermediate host being eaten - - Virulence greater in horizontally transmitted parasites than in vertically transmitted parasites. (horizontal host to host and vertical is from parent to offspring) cant compromise host until its passed onto next generation - Phage reproductive rate: vertical and horizontal transmission. Virulence with one day vert and one day hori = increase virulence. - View that parasites always evolve to be less virulent to hists (ie// rabbits and myxoma) - Parasites evolve to increase their fitness may result in decreased or increased virulence, Ie// covid was high mortality and morbidity but as new strains evolve then less virulence occurs - May be advantageous to kill the host to increase your infection via transmission. Larval stage tapeworms hydatid cyst that's consumed by a predator - Farming livestock, host to host transmission ideal conditions to increase conditions for transmission and treatment ie//vaccine kill 100% OF target but some (imperfect vaccines) can just decrease the replication rate allowing for evolution to take place to outcompete with new strains that have a faster replication rate. Ie// Marek's disease in chickens. **Describe the difference between host resistance, tolerance and resilience** Resistance = host's ability to reduce parasite burden - Tolerance = host's ability to withstand parasite burden - Trade off may exist between resistance and tolerance Genetic variation in host defence EBV lower the faecal egg count the better breeding factor to resistance to parasite eggs. **Explain what is meant by parasite aggregation and why aggregation is important in understanding parasite transmission** Arrogation of parasites: a lot of parasites of the same species (negative binomial distribution) - Leads to heterogeneity in transmission: 20/80 rule: 20% of most infected hosts - Target treatment to the most infected indivuals you have the best chance of overcoming the transmission of parasites Distributed of parasites : dispersed = a few **Explain why interactions between parasites within a host may affect the severity of parasitic disease**  - Woyliel: usually infected by more than one species, multiple infection (coninfection) gastrointestinal parasites. - Interaction betweens species of parasites within host can compete for resources within the stomach or blood. - Indirect thru host immune system (benefical (synergistic allowing better pathology in the host) or detrimental ( harmfull to parasite species = antagonistic to host pathology) - Platy, nematodoes, protozoan - Gastro worms reducing the RBC count allowing more damage and less immune response from host - Summary: Hosts and parasites are involved in a co-evolutionary arms race - Virulence is the parasite-induced reduction in host fitness - For parasites, there is often a trade-off between virulence and the efficiency of transmission - Hosts may respond to parasite infection by attacking the parasite (resistance) or limiting the parasite damage (tolerance) - For hosts, there is often a trade-off between resistance and tolerance - Parasite distributions are typically aggregated among hosts and this has important epidemiological implications - Coinfections are common and interactions among parasite species can affect disease outcome **Parasites in ecosystems L14** [Objective]: treat, control or even eliminate parasites from system **Describe how parasites may affect the functioning of ecosystems** The function of ecosystem: refers to the flow of the energy system - Ecosystem stocks - Ecosystem flows Ecosystem health? - *"We propose that a healthy ecosystem is one that is sustainable -- that is, it has the ability to maintain its structure (organisation) and function (vigor) over time in the face of external stress (resilience)." - Costanza & Mageau, 1999* **How do parasites affect the function of ecosystems?** - Regulate host population - - Mediate interactions among free-living species - Feature prominently in trophic networks adding complexity and parasites as prey [Density-dependent regulation of host population]: - Difficult to demonstrate in field studies (requires addition or removal of a parasite to a population - *Trichostronglus tenuis* in red goose - *High-intensity correlate with poor breeding* - *77% of populations with cyclic crashes 4-8 years* - Studied 175 individually managed populations Treated 1000--3000 (15--50%)per population with anthelmintic Treating \>20% sufficient to prevent crashes - [2. parasites may mediate predation interactions :] - hosts which have greater parasite burden may be predated more frequently - trophically transmitted parasites may manipulate host to increase the probability of transmission crucial for the survival and evolution of the parasite - *behaviour and activity levels* - *microhabitat use* - *colouration* - Polypipapiliotrema stenometra (Opecoelidae) Poritid coral polyps - Small, poor nutrition - Infected polyps larger, more nutrition, no defence, conspicuous Chaetodon multicinctus: - Spend 90% time budget foraging - Pluck individual polyps - Prefer infected polyps - Ingest up to 340 trematode larvae per half hour - Average worm load \