Biology 1A Past Paper 2024 - Parasites, People, and Pets PDF

Biology 1A 4 November 2024 Rick Maizels  Parasites, People and Pets Define parasitism and distinguish parasites from symbionts, commensals Define prevalence, incidence and intensity of infection Define mortality, morbidity and DALYs Define...

Biology 1A 4 November 2024 Rick Maizels  Parasites, People and Pets Define parasitism and distinguish parasites from symbionts, commensals Define prevalence, incidence and intensity of infection Define mortality, morbidity and DALYs Define ecto- and endoparasites and zoonosis Describe the basic features of named parasite life cycles Describe the pathology caused by named parasites Describe approaches taken to treat parasitic infections  Definition of Parasites (one of many) ‘A parasite is an organism living in or on another living organism, obtaining from it part or all of its organic nutrition, commonly exhibiting some degree of adaptive structural modification and potentially causing some degree of damage to its host’ Ancylostoma duodenale (hookworm)  Commensals, Mutualists, Parasites Commensalism Mutualism Mutually beneficial, (oxpecker); symbio:c, can be essen:al (microbiome) One (usually smaller) species Parasi:sm benefits, the other is unharmed (remora fish) One species benefits, the other is harmed  Defining Prevalence, Incidence and Intensity of Infection Prevalence - the proportion (%) of a population infected, e.g. 3%, or the total number in a country or across the world Incidence - the frequency of a population acquiring infection in a unit of time, eg 3% per week, or 100,000 per annum Intensity - measure of the number or density of parasites per host, e.g. ectoparasites on skin, or % of red blood cells infected with malaria Defining Disease - Mortality, Morbidity and DALYs Mortality - the number of deaths in a given time, or the % of deaths among all cases of infection Morbidity - the level of ill-health or disability among all cases of infection, or among the general population DALYs - Disability Adjusted Life Years A measure of overall disease burden. Number of healthy years lost to disease, disability or early death  Prevalence, Mortality, and DALYs Prevalence Mortality DALYs Ascaris roundworm 800 M 60 k 10.5 M Schistosomiasis 250 M 280 k 1.4 M Malaria 219 M 435 k 55 M Sleeping sickness 70 k 48 k 1.5 M Ascaris is directly transmitted through faecal contamination of soil Schistosomiasis is snail-borne Malaria is mosquito-borne VECTORS Sleeping sickness is tsetse fly-borne  Unicellular and Multicellular Parasites Eukaryotic Organisms at the Pathogen/Commensal Interface Helminths Protozoa Multicellular, metazoan Unicellular, either roundworms (nematodes), intracellular or schistosomes and extracellular tapeworms Arthropods Ectoparasites such as ticks and lice Millions of years of co-adaptation Co-evolution of hosts and Exquisite tuning to specific host parasites Infection not always pathogenic  Parasitic Protozoa Simple Classifica-on by Cellular Organisa-on Amoeboid Kinetoplastid Apicomplexa (Flagellated) (Apical Complex) Trypanosoma Plasmodium Entamoeba histoly-ca Leishmania Toxoplasma Sleeping spp. Malaria gondii Sickness Amoebic Dysentery Kala-Azar Toxoplasmosis  Helminths Mul-cellular roundworm and flatworm parasites Platyhelminthes Nematoda Intestinal nematodes Trematodes eg Schistosoma Cestodes eg Taenia Tapeworm living in small or large mansoni, living in hepatic in intestinal tract intestine vasculature  Ectoparasites Insects Arachnids Lice Fleas Ticks Polyparasitism is the rule in Nature Wood mouse (Apodemus sylvaticus)  Parasites, People and Pets Zoonosis : an infection or disease that is transmissible from animals to humans under natural conditions Toxocara Echinococcus canis granulosus (Helminth) (Helminth) Toxoplasma Fleas and Ticks gondii (Ectoparasites) (Protozoan)  Toxocara canis In dogs and foxes, predominant intestinal roundworm Infection by ingesting eggs from soil Accidental hosts (eg humans) larvae migrate in soft tissues Infants particularly at risk - pica (eating soil, sand etc) Visceral larva migrans - invades liver, causes fevers Ocular larva migrans - can enter the eye and impair sight  Toxocara canis Eggs have resilient coat, survive in soil for months, resist chemical treatments Eggs hatch in stomach releasing larvae Adult females release eggs in faeces In dogs, move to small Larvae intestine migrate - and mature lungs, liver, to adult brain worms  Toxocara canis In adult female dogs larvae remain arrested in the tissues and are “reawakened” during pregnancy Larvae cross placenta to infect pups before birth Larvae also migrate into colostrum to infect milk Readily controlled in companion animals with regular anthelmintic - especially late in pregnancy and in young pups Echinococcus granulosus Hydatid disease  Echinococcus granulosus Adult tapeworm in small intestine Releases eggs in Intermediate Host faeces Parasites encyst in tissues Definitive Host  Echinococcus granulosus Accidental Host Definitive Host Echinococcus granulosus  Echinococcus Surgery for Hydatid Cyst granulosus Prevention … as there is no cure Toxoplasma gondii Protozoan Parasite Zoonotic Cosmopolitan Definitive Host : Cats  Life Cycle of Toxoplasma gondii Cornell University College of Veterinary Medicine  Toxoplasma gondii Oocysts develop into tachyzoites to disseminate infection in the host Parasitophorous Attachment and Rapid Vacuole - Avoids Invasion - Broad Multiplication - Fusion with Cell Specificity 16 Daughters Lysosomes  Toxoplasma gondii Oocysts Oral Tachyzoites Inges-on (Acute Infec:on) Congenital Can Toxoplasmosis: Bradyzoites Re-ac-vate Hydrocephaly, Visual and (Chronic Infec:on, Mental Impairment Dormant Tissue Cysts eg in brain) Pathological Consequences of Toxoplasma Infec-on Cysts in brain Tachyzoites invade the foetus change behaviour of naïve mother Mice lose aversion to cats Infec=on of brain in Car drivers may be third trimester less risk-averse  Toxoplasma gondii World’s most successful parasite ? 30% of humans infected. Human infec-on from cat liXer, unwashed food, raw meat Risk is first infec-on in later life, especially during pregnancy Incidence of congenital toxoplasmosis < 1/10,000 World’s most clever parasite? Migrates to brain to alter behaviour  Ectoparasites Insects Arachnids Lice Fleas Ticks  48% of primary school children in the UK experience head lice infesta:on each year! Adapted to Parasitism  Spreading Disease Yersinia pestis Gram –ve bacteria Oriental rat flea Xenopsylla cheopis  Ticks (Ixodes ricinus) < ! ! ! ! Orkney & ! ! ! Shetland Islands ! ! < ! < ! ! ! ! ! ! ! ! ! ! ! ! < ! ! ! ! < ! ! < ! < < ! ! ! ! < < ! ! < ! < ! < < ! < ! < < ! < ! < < ! < < < < < < < < ! ! ! ! < ! < ! ! ! < < ! ! ! ! ! < < ! ! < ! < ! ! < ! < ! ! < < ! < < ! ! < < ! ! < < ! ! < < < < < < < < < ! ! < ! < < ! ! ! < < ! ! < ! ! ! < < ! ! ! ! ! ! ! ! < < ! ! ! < ! ! ! ! < ! ! < < ! < ! ! ! ! ! < ! < ! < ! ! ! < < < ! ! ! < < < ! ! ! ! ! ! ! ! < < < < < < ! ! < ! ! ! < ! ! < ! < < ! ! < < < ! < ! < < < < < < ! ! ! < ! ! < < ! < ! < ! < ! < ! Ixodes ricinus ! ! < ! < ! ! < < < ! ! ! < < < PHE Tick Recording Scheme ! ! ! < < < < ! ! < < ! ! < ! BRC tick distributions < ! ! ! ! < < ! ! < ! < < < < ! ! ! ! ! < ! ! ! ! ! ! ! < ! < ! ! < ! < ! ! < < < ! < < < < < < < ! < < ! < Spread Lyme Disease caused by < ! < < < < < ! ! < < < < < < < ! < < ! ! < < < < ! < ! < < < ! ! ! < < < < < < < ! < < < < < < < < ! < ! < < < < < < spirochaete bacterium ! < < < ! < < < < < < < < < < < < < < < < < < < < < < Borrelia burgdorfi < ! < < < < < ! < ! ! < < < < < < ! < ! < ! < ! ! < ! < ! ! ! ! < ! < ! < < < ! ! < < ! ! < ! ! ! < ! < < < ! < ! ! < < < ! < < ! ! < ! < < ! ! < ! ! ! ! < < ! < < < ! ! < < ! ! ! < ! < ! < ! < < < ! ! ! < ! ! ! ! ! ! < < ! < ! < ! < ! ! ! ! < ! < ! ! < < ! ! < ! ! ! ! < ! < ! < ! < ! ! ! < ! ! ! ! < < ! ! ! ! < ! < < ! < < ! < < ! ! < ! ! ! < < < ! < < < ! < ! ! < < ! ! ! < ! < < < ! < < ! ! < < < ! ! ! < < < ! ! < < ! ! < ! < ! < < ! < < ! < < ! < < < < < < ! ! < ! ! < < < < < ! < < ! < < < < < < < < < ! < ! < < ! < ! < < ! < < ! < < < < < < < < < < < < < < < < ! ! < < < < < < ! < < < < < < ! < ! ! < ! < ! < < ! < ! < ! < < < < < < < < < < < < ! < < < < < < ! < ! < < < < < < < < < < ! < < < < < < < < < ! < < ! < < < < < < < < ! < < < < ! < < ! < < < ! < < < < < < < ! < < < < < < < < ! < ! < < ! < < ! < < < < < < < < ! < < < < < < < < < < < < ! < < < < < ! < < < < ! < < < < ! < ¯ < < ! < < < < < < < ! < ! < ! < < < ! < ! < < < < ! < < < < < < < < < < < < < < < < < < < ! ! < ! < < ! < < < < < ! < ! ! < < < < < < < ! < < < < < < < ! < < < ! < < < < < ! ! < < < < < < ! ! < < < < < < < < < < < < ! < ! < < < < < ! ! ! < < < < ! ! ! ! < < < < < < < < < ! < < ! < ! < ! ! < < ! < ! < < < < < ! < < < < < < < < < ! < < < ! < < ! ! < < < < < ! < ! ! < < ! ! < ! Service Layer Credits: Esri, HERE, DeLorme, MapmyIndia, © OpenStreetMap contributors, and the GIS user community < ! Contains Ordnance Survey data © Crown copyright and database right 2015. Contains National Statistics data © Crown copyright and database right 2015. < 3000 cases in UK p.a. < ! Lyme Disease transmiWed by Ixodes ricinus :cks Erythema, bull’s eye inflamma-on Subsequent myalgia, arthralgia, malaise Can cause chronic arthri-s, neuropathy, fa-gue Fully treatable with early an-bio-c treatment  Questions ? Ask Now or email [email protected]