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Parasitology: a biological science that studies parasites hosts relationship between them Parasite: lives, feeds, grows, multiplies on another organism, its host. Types of parasites celled, organized cellular structure ingest solid particles aquatic environment binary fission at some point in life c...

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Parasitology: a biological science that studies -the parasites -their hosts -the relationship between them Parasite: lives, feeds, grows, multiplies on another organism, its host. Types of parasites -Protozoa ---Single celled, organized cellular structure ---May ingest solid particles ---Require aquatic environment ---Reproduce by binary fission at some point in life cycle -Helminths (worms) ---Multicellular, Organized internal structure; includes ---Platyhelminths (flatworms) ---Nematoda (roundworms) ---Acantocephalans -Ectoparasites ---Insects and arachnida found on the skin. Phoresis ---NO physiological or biochemical dependence ---“traveling together” --Phoront – smaller, mechanically carried Mutualism ---Beneficial for both partners ---Obligatory ---Cleaning symbiosis Commensalism ---One benefits, other is unaffected. ---“eating at the same table” ---Types: ---Facultative ---Obligate Parasitism -Parasitism: The most common mode of life on the planet. ---symbiotic between different species, one organism, the parasite, benefits host doesn’t. ---Parasites  mechanical injury  inflammatory/immune response to host  ‘rob’ host of nutrition. Types of Parasitism -Life cycle ---Obligate ---Facultative ---Accidental (incidental) ---Permanent ---Temporary (intermittent) – micropredators -Location on the host ---Endoparasitic ---Ectoparasitic Adaptations to a Parasitic Existence 1,High reproductive potential --multiple fission in Apicomplexa --hermaphrodism of trematodes --partenogenesis in Strongyloides spp. --strobilation of tapeworms for high ova output --high ova/larval output of many worms (one Ascaris ♀ can lay 200,000 eggs per day for a year) 2.Unique morphological/physiological specializations, loss of structures, etc. --loss of structures or enzymes (e.g. GI tract in tapeworms). --development and refinement of a TEGUMENT; a living external layer of digeneans, cestodes and acanthocephalans; allows digestion & other functions across body surface --development of pathogenic adaptations (e.g. mechanisms of attachment). --production of anti-coagulants in leeches and hookworms 3.Special site specificity 4.Usually, but not always, non-lethal to host 5.More numerous than hosts 6.Much smaller than host (if larger, then termed a predator) 7.Many parasites are now being shown to change host behaviour 8.Often have evolved methods of evading host immune system Adaptations: help parasites stay in the host, get nutrients they need to grow & reproduce, & disperse --Feeding ----according to the location in or on the host where the parasite feeds, and the type of material it feeds on. --Reproduction ----parasites reproduce at several points during their life cycle, sometimes sexually and sometimes asexually. ----Reproduction may simply produce progeny that will be transmitted to new hosts → important consequences for parasite transmission & for the host in which these progeny are produced ----Reproduction may also produce progeny that remain in the host and continue to develop. --Dispersal & Transmission ----ways in which parasites are spread from the host, so that they increase their chances of encountering new hosts. ----await ingestion by a blood-feeding vector vs. simply pass out in the host's excreta as produced

----timing their leave vs. simply taking chances. ----no "better“way than others parasites → a variety of techniques, which all work (or the parasite would be extinct!) --Adaptations for Feeding ----Ectoparasites – use one of two food sources from the host: --Blood: must possess some structure that allows them to penetrate the epidermis and reach blood vessels. --tissues: often graze on sloughed epithelium or mucus from the host. ----may use mechanical or chemical means to erode living tissue and ingest it. -Fleas have mouthparts adapted for piercing & sucking -Ticks insert their moth parts through the host's skin. - Endoparasites –: can acquire their nutrients from the host: --blood,ingesting it whole or absorbing nutrients from it. --intestinal contents --no damage to host tissue from feeding. Adaptations for Reproduction - Sexual Reproduction – --Hermaphroditism vs. dioecy --Many taxa (i.e. Digenea) are hermaphroditic ---Some become dioecious (Nematoda) ---Rhabditida have hermaphroditic species. Adaptations for Reproduction - Asexual Reproduction – --By adults - few helminths multiply asexually as adults. --Gyrodactylus = polyembryony (embryo developing in uterus contains another, less-developed, embryo) --Many protozoans multiply asexually entering cyst stage. --Entamoeba produces 4 or 8 nuclei (N), depending on species, cytoplasm doesn’t divide until a new host is entered. --Giardia doubles nuclei & other structures. Cell division completes when next host is infected. --Sporocysts of Digenea, in the molluscan host, asexually make either daughter sporocysts, rediae, cercariae, depends on species. ----Few Cestoda use asexual. Except for Echinococcus, which produces a hydatid cyst. --The cyst (Cy) is produced by the parasite and is surrounded by a capsule (Ca) produced by host tissue (H) as a defense response. The inner lining of the hydatid is a germinative epithelium (G) which can sprout numerous brood capsules and larval parasites. Typical Ways of Parasites Transmission -INGESTION from food or water / inhalation included here -VECTORS -DIRECT PENETRATION of skin from environment Adaptations for Dispersal -Dispersal - the process by which individual parasites move from one geographic location to another -direct activity by free-living stages (dispersal on the order of meters). -many adult ectoparasites:(i.e.fleas), leave the host frequently &can disperse for short distances, but the host is the main agent of dispersal. -Some free-living larval endoparasites have specialized structures (i.e. tails, cilia) Adaptations for Host Finding Parasites spend some or all of their existence in or on a host → host finding - everything involved in getting into (or onto) a new host. ---Passive Methods – similar to dispersal methods ---In terrestrial environments – adaptations to withstand desiccation -Active Methods --selective in choosing their host, mobile, often have sensory structures Transmission by Vectors & Intermediate Hosts Vectors -Parasites enter vectors passively, as the vectors are feeding -parasite then undergoes some development or replication in the vector When the vector seeks out a new host to feed on, it also introduces the parasites it is harbouring. Blood-feeding arthropods are the most common vectors in terrestrial habitats PLASMODIUM transmitted by mosquitos Transmission by Intermediate Hosts -Common method for terrestrial parasites -Parasites may enter IH actively or passively. -Once inside they usually transform into a stage that can resist the defence responses of the IH, and persist for long periods, until that host is eaten by another animal that can serve as a 2nd IH or DH --IH for endoparasites: --Crustaceans, Fish, Insect larvae Enhance Transmission – Host Manipulation Behavior -Many parasites infect an intermediate host that needs to be eaten by the definitive host for the parasite to complete its lifecycle.

-There are many instances of parasites altering their intermediate host’s behavior to make it more vulnerable to a predator (the definitive host). -Leucochloridium "Pulse!“ paradoxum - fluke -DH: birds, IH: snails -Anthroponoses - human diseases that can be transmitted to animals -Zoonosis - animal diseases that may be transmitted from animals to humans -Epidemic - disease that affects a large number of humans and spreads rapidly -Epizootic - disease that affects a large number of non-human animals and spreads rapidly -Euryxenous - broad host range -Monoxenous - single host life cycle -Heteroxenous - alternation of generations of a parasite in different host species -Incidence - the number of cases of an infection occurring during a given period of time in relation to the population unit in which they occur -Prevalence - number of organisms in a population infected with a parasite at any one time -Virulence - relative infectiousness of a parasite -Infection - parasitic invasion resulting in injury and reaction to injury -Latent - non-visible infection -Pathogenic - results in disease or morbid symptoms -Premunition - resistance to superinfection; depends upon survival of parasites in host and disappears with their elimination -Parasitemia - parasites in blood Protozoans - General Characteristics – -large group of unicellular organisms, extremely diverse in morphology, life cycles and modes of reproduction. -most are free living. -parasitic species vary in their modes of transmission, and level of pathological response by their hosts. -diseases caused by protozoans are among the most devastating of all parasitic infections to humans and wildlife. Morphology -single-celled eukaryotes -small organisms (few µm in length up to 1 mm) -basic body organization: --external plasma membrane --cytoplasm --nucleus --one or more nuclei - in some taxa the nuclei are of two types: ---larger macronuclei ---smaller micronuclei. --food-containing vacuoles may be present --mitochondria occasionally large enough to be seen. Locomotion --One or more long flagella --Cilia - shorter and more numerous than flagella --Flagella and cilia aid in swimming. --Pseudopodia - temporary extensions of the cytoplasm elongating the plasma membrane - enable crawling. Morphological Forms at least 2 distinct morphological forms during their life cycle: -Trophozoites - feeding stages ---may reproduce asexually -Cysts - transmission stages enclosed within a membrane to resist conditions in the external environment. -Gametocytes - stages which are about to reproduce sexually and form gametes. Location in Host Tissues -intercellular (between cells) -intracellular (inside cells), -within the lumen of various organs. Protozoans – Diversity Traditionally classified based on their means of locomotion: -Sporozoans --Apicomplexa, Myxozoa, Microsporidia --Flagellates (e.g. Giardia lamblia) --Amoeboids (e.g. Entamoeba histolytica) --Ciliates (e.g. Balantidium coli) Apicomplexa (sporozoans) - General Characteristics – -intracellular -transmission from host to host: ---using a vector (i.e. mosquitoes) ---ingestion of food / water contaminated by oocysts. ---prey – predator relation -life cycle - alternate reproduction cycles of: ---sexual (gametogony) ---asexual:, schizogony – inside the host; sporogony – outside of the host) Apicomplexa – Morphology --Sporozoites and merozoites ---infective stage ---banana-shaped bodies with an apical complex. ---located at the anterior end of the organism,

---aids in the penetration of host cells Trophozoites -uninucleate cells, may have a large vacuole , various other inclusions. Schizonts -multinucleated cells. Gametocytes -large cells, uninucleate, often containing granules Oocysts -surrounded by a cyst wall, which may be impermeable in those species that pass through the external environment. --may contain a number of sporocysts, which each contain a number of sporozoites. Apicomplexa - Diversity & Importance – -An extremely large and diverse group (>5000 named species) -Piroplasms - pear-shaped protozoan organisms that live in red blood cells of mammals; transmitted by ticks. --Plasmodium - causative agent of malaria --Babesia - relatively rare zoonotic infection --Theileria - in cattle -Coccidia - opportunistic pathogens often associated with AIDS --Cryptosporidium - causative agent of cryptosporidiosis (important zoonosis) --Eimeria - in birds, mammals --Isospora - in carnivors --Sarcocystis - causative agent of sarcosporidiosis (zoonosis) --Toxoplasma - causative agent of toxoplasmosis (important zoonosis). Plasmodium --causative agent of malaria (a major killer of humans) --various species infect mammals, birds, and even poikilotherms. ---blood cells - the main target of these parasites. ---transmitted between vertebrates by blood feeding arhropods. ---successfully resisted human attempts to control it by vaccine, chemotherapy, and insecticide treatment of its vectors. Malaria a mosquito-borne infectious disease caused by Plasmodium. -naturally transmitted by the bite of a female Anopheles mosquito. -widespread in tropical and subtropical regions (Americas, Asia, and Africa). -approximately 350–500 million cases of malaria yearly, killing 1-3 million people, especially young children in sub-Saharan Africa -commonly associated with poverty, -also a cause of poverty and a major hindrance to economic development. -5 species can infect humans: -the most serious forms of the disease are caused by Plasmodium falciparum. -malaria caused by Plasmodium vivax, Plasmodium ovale and Plasmodium malariae causes milder disease in humans that is not generally fatal. -Plasmodium knowlesi that causes malaria in macaques but can also infect humans (zoonosis). Protozoa and Trematodes Plasmodium Latin and particular name of the parasite --Plasmodium spp. Malaria Its life cycle -definitive host: idk cycle doesn’t finish in humans us, mosquito is a vector -intermdiate host Human -infective stages for both hosts --Human: when mosquito takes a blood meal, diagnostic stage = maturation of trophozoites --Mosquito: ruptured oocyst, release of sporozoites infective names of larval stages Ways to get infected: stung by mosquito carrying disease Which parasitic stage causes it: sporozoites and merozoites Parasite location/migration inside the host: --attacks liver cells which rupture then they enter blood cells (main target) Symptoms: --Headache, fever, muscle pain & fatigue, chills, sweating, dry cough, enlarged spleen, nausea, vomiting Prevention: --WHO’s roll back malaria initiative, Primaquine® active against the hepatic stages, Chloroquine derivative drugs, Mosquito control Generalized life cycle of GI Apicomplexa protozoans Cryptosporidium --definitive host: Cattle, humans and mammals --intermediate host: none, All 3 stages happen in the same host once infected, once the oocysts are left from the feces they are ready to infect again (can auto infect the host again, or a new host) require no external conditions to become infective infective stages for both hosts: infective when it exits host infective names of larval stages: doesn’t need external conditions to be infective, sporulated oocysts

Ways to get infected: swimming in contaminated water or food with oocysts which parasitic stage causes it: merozoites: parasite location/migration inside the host: Parasites inhabit the microvillus (brush) border of the gastric glands (C. muris) or lower half of the small intestine (C. parvum) -symptoms: severe diarrhoea which may take many weeks to resolve, immunity is short-lived -prevention: cook meat well, avoid contaminated waters Toxoplasma gondii First isolated from an African rodent (Ctenodactylus gundi) - Its life cycle definitive host: humans, cattle, mammals, cats --intermdiate host: cats (extraintestinal stages --infective stages for both hosts ---Human: cysts with bradyzoites, oocysts ---Cat: schizonts -Ways to get infected: soiled water, uncooked meat, unborn baby can be infected by mother (congenital toxoplasmosis) (her milk will also be infected) -which parasitic stage causes it: sporozoites and merozoites (schizogony, merogony) -parasite location/migration inside the host: intestinal tract, move throughout -symptoms: flu like symptoms(Fever, Malaise ("general feeling of being unwell“), Lymphadenopathy, Encephalitis, Myocarditis, Pneumonia, Retinochoroiditis), most people don’t know they have it, Acute toxoplasmosis associated with formation of pseudocysts containing tachyzoites (rapidly dividing merozoites). Chronic (asymptomatic) toxoplasmosis associated with formation of cysts containing bradyzoites (slowly dividing merozoites) --major cause of abortion in sheep – economic loss. Controls the behavior of the host, Takes more risks, Increases chanced of being eaten -prevention: cook food, don’t go to poor places, clean cat litter box, clean water supply HEMOFLAGELLATES - TRYPANOSOMES sleeping sickness, Chagas disease Its life cycle -definitive host: humans, horses, cattle, pigs, dogs -intermediate host: blood feeding arthropod -infective stages for both hosts ---Human: when mosquito takes a blood meal, diagnostic stage = maturation of trophozoites ---Mosquito: ruptured oocyst, release of sporozoites -infective names of larval stages ---pleomorphic. ---Different morphologic forms based on the host they are in (mammal vs. insect). ---Each morphologic form is based on the flagellum in relation to the nucleus. ---Amastigotes Ways to get infected: blood feeding arthropods, STD’s, TseTse fly -biting fly (very painful) -only bites during the day -locals move animals at night to avoid Which parasitic stage causes it: Parasite location/migration inside the host: Gut, Can invade the CNS --attacks liver cells which rupture then they enter blood cells (main target) Symptoms: --swollen lymph nodes, Fever, generalized pain, headaches, weakness, cramps --Rapid weight loss --apathy, disinclination to work, mental dullness, disturbed coordination, tremor of tongue, hands & trunk, paralysis & convulsion, increased sleepiness, coma & death) --Myocarditis, anemia, hemorrhage & death. Prevention: --WHO’s roll back malaria initiative, Primaquine® active against the hepatic stages, Chloroquine derivative drugs, Mosquito control Leishmania Its life cycle -definitive host: humans, dogs, cats -intermediate host: sand fly -infective stages for both hosts ---Human: when sandfly takes a blood meal, injects macrophages infected with amastigotes ---Mosquito: ruptured oocyst, release of sporozoites Ways to get infected: blood feeding arthropods, STD’s, TseTse fly -biting fly (very painful) -only bites during the day -locals move animals at night to avoid Parasite location/migration inside the host: internal organs, GI tract, lesions on body -attacks liver cells which rupture then they enter blood cells (main target)

Symptoms: --Diffuse cutaneous ---more severe in HIV patients ---fever, splenomegaly, diarrhea, abdominal pain, dysphagia -mucotaneous ---ulcers, sloughing of cartilage (nose, ears) -Visceral ---Liver and spleen enlarge -Post kala-azar ---Contains numerous amastigotes ---Occurs with relapses of the visceral form Trichomonas vaginalis -Flagellated protozoan -No cystic stage (lives only as trophozoite) -Anaerobic -Transmission: STD, soiled washcloths, towels, clothing -Diagnosis: presence of thicomonads in vaginal secretions -Treatment: metronidazole – very toxic to the liver, threatment should be short -Men don’t show symptoms (maybe enlarged prostate) – important carriers Giardia -Host: mammals, birds, humans -Intermediate host: beavers -Most common flagellate of the GI tract -Beaver fever -Once in host it can complete whole cycle -Located in intestine -Zoonic -Cyst stage = dormant in the poop = infective stage -Transmitted orally or anally -Water or food borne -Asymptomatic, very greasy mucus, diarrhea, weight loss, gas, chronic wasting -Prevention: water filter, awareness, not swimming in contaminated Entamoeba -Cause of amoebic dysentery -E. histolytica = Zoonotic = humans, nonhuman primates ---Cyst = infective stage ---Transmitted from feces to water ---Little harm to humans or animals (we carriers) ---Prevention = boil water, wash foods, improve hygiene ---E. gingivalis = humans mouth --------No known cyst stage --------Transmitted person to person -E. coli = non pathogenic -E. invadins = pathogen of reptiles Balamuthia mandrallaris -Definitive host = human, no IH -Trophozoite = infective stage -Found in respiratory tract Balantidium Coli -Hosts = humans, non-human primates -Live in GI tractus -Cyst = infective stage Premunition -Infected with a low number of parasites gives protection is not enough to cause clinical manifestation ---Person is considered healthy --Will transmit future infections ---In endemic areas they will not be treated because they will be reinfected and possibly get sick ---In normal areas they will get treated because they can still spread the disease Trophozoite --Feeding stage. Found in the host, inside the cell host --They can initiate either asexual or sexual reproduction --Once oocysts or something else infect, they become trophozoites Miracidium --Larval stage of flukes, Found free living once released fro...