ASU BIO 162 - parasites (18 pages)

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parasites



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parasites

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Pages:
18
School:
Arizona State University
Course:
Bio 162 - Microbiology Concepts for Allied Health
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Eukaryotic Microbes Parasites Protozoa Helminths Arthropods Eukaryotic Microbes Table 12 1 Protozoa Life Stages Trophozoite vegetative feeding mostly motile Cyst dormant protective thick wall Most are free living in water and soil Classified by motility life cycle Subdivided by location in human host GI blood GU 1 2 3 4 Sarcodina Amoeba move by pseudopods Ciliophora Ciliates move by cilia Mastigophora Flagellates move by flagella Apicomplexan Sporozoa complex life cycle 1 Diversity among Protozoa Amoeba Entamoeba histolytica Amoebic dysentery Naegleria primary amoebic meningoencephalitis Acanthamoeba contact lens contaminant Figure 12 18a Amoebae Protozoa with no truly defined shape Move and acquire food through the use of pseudopodia Found in water sources throughout the world Few cause disease 2 Entamoeba histolytica Carried asymptomatically in the digestive tracts of humans No animal reservoir exists Infection usually occurs by drinking water contaminated with feces that contain cysts Trophozoites migrate to the large intestine where they multiply Entamoeba histolytica Three types of amebiasis can result from infection Luminal amebiasis Least severe form that is asymptomatic Invasive amebic dysentery More common form of infection Characterized by bloody mucus containing stools and pain Invasive extraintestinal amebiasis Trophozoites carried via the bloodstream throughout the body Maintaining clean water is important in prevention The Course of Amoebiasis Due to Entamoeba histolytica 3 Acanthamoeba and Naegleria Cause rare and usually fatal brain infections Common inhabitants of natural waterways as well as artificial water systems Contact lenses wearers who use tap water to wash their lenses can become infected Acanthamoeba diseases Infection occurs through cuts or scrapes the conjunctiva or through inhalation Acanthamoeba keratitis results from conjunctival inoculation Amebic encephalitis is the more common disease Acanthamoeba and Naegleria Naegleria disease Infection occurs when swimmers inhale contaminated water Amoebic meningoencephalitis results when trophozoites migrate to the brain Prevention is difficult because these organisms are environmentally hardy Flagellate Trichomonas vaginalis no cyst stage Trichomoniasis STI Giardia lamblia intestinal malabsorption Traveler s diarrhea day care centers hikers Figure 12 17b d 4 Giardia Hemoflagellates Trypanosoma African sleeping sickness or Chagas disease Transmitted by tsetse flies or reduviid bugs Leishmania leishmaniasis Baghdad Boil Desert Storm Transmitted by sand fly vector Ciliates Complex cells with rudimentary mouth cytostome Balantidium coli is the only human parasite intestinal disease associated with pork Paramecium Vorticella Figure 12 20 5 Ciliates Protozoa that use cilia in their trophozoite stage Balantidium coli is the only ciliate known to cause disease in humans Commonly found in animal intestinal tracts Humans become infected by consuming food or water contaminated with feces containing cysts Trophozoites attach to the mucosal epithelium lining the intestine B coli infections are generally asymptomatic in healthy adults Ciliates Balantidiasis occurs in those with poor health Characterized by persistent diarrhea abdominal pain and weight loss Dysentery results in severe infections Presence of trophozoites is diagnostic for the disease Prevention relies on good personal hygiene and efficient water sanitation Apicomplexans Sporozoa Characteristics Nonmotile Intracellular parasites Complex life cycles Asexual sexual reproduction Plasmodium malaria transmitted by Anopheles mosquito Cryptosporidium diarrhea AIDS related Toxoplasma toxoplasmosis AIDS related 6 Plasmodium 1 Infected mosquito bites Sporozoites in salivary gland 2 Sporozoites undergo schizogony in liver cell merozoites are produced human sporozoites migrate through bloodstream to liver of human 9 Resulting sporozoites migrate to salivary glands of mosquito 3 Merozoites Sexual reproduction Asexual reproduction 8 In mosquito s Zygote Female gametocyte digestive tract gametocytes unite to form zygote released into bloodsteam from liver may infect new red blood cells Intermediate host 4 Merozoite develops into ring stage in red blood cell Male gametocyte Ring stage Definitive host 7 Another mosquito bites infected human and ingests gametocytes 6 Merozoites are released when red blood cell ruptures some merozoites infect new red blood cells and some develop into male and female gametocytes Merozoites 5 Ring stage grows and divides producing merozoites Figure 12 19 Plasmodium Cryptosporidium parvum Waterborne Found in cattle Attach to intestinal lining Cause watery diarrhea Acid fast Oocysts Resistant to chlorine Figure 25 19 7 Cryptosporidium life cycle Toxoplasma gondii Eukaryotic Microbes Table 12 1 8 Helminths worms Life Stages egg larva adult complex life cycles infective stage egg or larva definitive host harbors adult stage intermediate hosts may be more than one Classifications Nematodes roundworms Platyhelminthes flatworms Trematodes flukes nonsegmented Cestodes tapeworms segmented Nematodes Roundworms Intestinal roundworms Ascaris Giant intestinal roundworm Enterobius Pinworm Necator Ancylostoma Hookworm Tissue roundworms Trichinella spiralis trichinosis Features of the Life Cycle of Roundworms Parasites of almost all vertebrates Have a number of reproduction strategies Most intestinal nematodes shed their eggs into the lumen of the intestine Eggs are eliminated in feces Eggs are consumed in contaminated food or water Some intestinal nematodes release their eggs into the soil Larvae actively penetrate the skin of a host Inside the body they travel to the intestine Other nematodes encyst in muscle tissue and are consumed in raw or undercooked meat Mosquitoes transmit a few species of nematodes Adult sexually mature stages are found only in definitive hosts 9 Nematodes roundworms Ascaris lumbricoides adult stage Pinworm disease is the most prevalent helminthic infection in the United States Enterobius vermicularis Life cycle Diagnosis with cellophane tape Transmission 10 Enterobius Pinworm Figure 12 29 Diagnosing Pinworm Disease Necator or Ancylostoma Hookworm 11 The Life Cycle of the Hookworms Ancylostoma duodenale and Necatur americanus Trichinella Filariasis is a lymphatic system infection Wuchereria bancrofti Life cycle Transmission by mosquito Symptoms Elephantiasis 12 Platyhelminthes Flatworms Trematodes Flukes nonsegmented Schistosoma


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