Eukaryotic MicrobesParasitesProtozoa, Helminths, Arthropods

Eukaryotic MicrobesTable 12.1

ProtozoaLife Stages Trophozoite -vegetative; feeding, mostly motileCyst dormant; protective thick wallMost are free living in water and soil Classified by motility & life cycleSubdivided by location in human host (GI, blood, GU)

Sarcodina- Amoeba - move by pseudopodsCiliophora - Ciliates - move by ciliaMastigophora - Flagellates - move by flagellaApicomplexan - Sporozoa complex life cycle

Diversity among Protozoa

AmoebaEntamoeba histolyticaAmoebic dysentery

Naegleriaprimary amoebic meningoencephalitis

Acanthamoebacontact lens contaminantFigure 12.18a

AmoebaeProtozoa with no truly defined shape Move and acquire food through the use of pseudopodiaFound in water sources throughout the worldFew cause disease

Entamoeba histolyticaCarried asymptomatically in the digestive tracts of humansNo animal reservoir existsInfection usually occurs by drinking water contaminated with feces that contain cystsTrophozoites migrate to the large intestine where they multiply

Entamoeba histolyticaThree types of amebiasis can result from infectionLuminal amebiasisLeast severe form that is asymptomaticInvasive amebic dysenteryMore common form of infectionCharacterized by bloody, mucus-containing stools and painInvasive extraintestinal amebiasisTrophozoites carried via the bloodstream throughout the bodyMaintaining clean water is important in prevention

The Course of Amoebiasis Due to Entamoeba histolytica

Acanthamoeba and NaegleriaCause rare and usually fatal brain infectionsCommon inhabitants of natural waterways as well as artificial water systemsContact lenses wearers who use tap water to wash their lenses can become infectedAcanthamoeba diseasesInfection occurs through cuts or scrapes, the conjunctiva, or through inhalationAcanthamoeba keratitis results from conjunctival inoculationAmebic encephalitis is the more common disease

Acanthamoeba and NaegleriaNaegleria diseaseInfection occurs when swimmers inhale contaminated waterAmoebic meningoencephalitis results when trophozoites migrate to the brainPrevention is difficult because these organisms are environmentally hardy

FlagellateTrichomonas vaginalisno cyst stage Trichomoniasis - STIGiardia lambliaintestinal malabsorptionTraveler's diarrhea, day care centers, hikersFigure 12.17b-d

Giardia

HemoflagellatesTrypanosomaAfrican sleeping sickness or Chagas diseaseTransmitted by tsetse flies or reduviid bugs

Leishmanialeishmaniasis Baghdad Boil- Desert StormTransmitted by sand fly vector

CiliatesComplex cells with rudimentary mouth (cytostome)

Balantidium coli is the only human parasiteintestinal diseaseassociated with porkParameciumVorticellaFigure 12.20

CiliatesProtozoa that use cilia in their trophozoite stageBalantidium coli is the only ciliate known to cause disease in humansCommonly found in animal intestinal tractsHumans become infected by consuming food or water contaminated with feces containing cystsTrophozoites attach to the mucosal epithelium lining the intestineB.coli infections are generally asymptomatic in healthy adults

CiliatesBalantidiasis occurs in those with poor healthCharacterized by persistent diarrhea, abdominal pain, and weight lossDysentery results in severe infectionsPresence of trophozoites is diagnostic for the diseasePrevention relies on good personal hygiene and efficient water sanitation

Apicomplexans (Sporozoa)Characteristics:Nonmotile, Intracellular parasitesComplex life cycles, Asexual/sexual reproduction

Plasmodium malariatransmitted by Anopheles mosquitoCryptosporidium diarrhea; AIDS relatedToxoplasma toxoplasmosis; AIDS related

PlasmodiumFigure 12.19Infected mosquito bites human; sporozoites migrate through bloodstream to liver of humanSporozoites undergo schizogony in liver cell; merozoites are producedMerozoites released into bloodsteam from liver may infect new red blood cellsMerozoites are released when red blood cell ruptures; some merozoites infect new red blood cells, and some develop into male and female gametocytes12346Asexual reproductionIntermediate hostMerozoite develops into ring stage in red blood cellRingstageMerozoitesAnother mosquito bites infected human and ingests gametocytes75Ring stage grows and divides, producing merozoitesDefinitive hostIn mosquitos digestive tract, gametocytes unite to form zygote8Male gametocyteFemale gametocyteZygoteSexual reproductionResulting sporozoites migrate to salivary glands of mosquito9Sporozoites in salivary gland

Plasmodium

Cryptosporidium parvumFigure 25.19WaterborneFound in cattleAttach to intestinal liningCause watery diarrheaAcid-fast OocystsResistant to chlorine

Cryptosporidium life cycle

Toxoplasma gondii

Eukaryotic MicrobesTable 12.1

Helminths - wormsLife Stagesegg, larva, adult; complex life cyclesinfective stage: egg or larvadefinitive host: harbors adult stageintermediate hosts: may be more than one

Classifications:Nematodes - roundwormsPlatyhelminthes - flatwormsTrematodes - flukes- nonsegmented Cestodes - tapeworms- segmented

Nematodes- RoundwormsIntestinal roundworms:Ascaris (Giant intestinal roundworm)Enterobius (Pinworm)Necator / Ancylostoma (Hookworm)Tissue roundwormsTrichinella spiralis - trichinosis

Features of the Life Cycle of RoundwormsParasites of almost all vertebratesHave a number of reproduction strategiesMost intestinal nematodes shed their eggs into the lumen of the intestineEggs are eliminated in feces Eggs are consumed in contaminated food or waterSome intestinal nematodes release their eggs into the soil Larvae actively penetrate the skin of a hostInside the body, they travel to the intestine

Other nematodes encyst in muscle tissue and are consumed in raw or undercooked meatMosquitoes transmit a few species of nematodesAdult sexually mature stages are found only in definitive hosts

Nematodes - roundwormsAscaris lumbricoides- adult stage

Pinworm disease is the most prevalent helminthic infection in the United StatesEnterobius vermicularisLife cycle Diagnosis with cellophane tapeTransmission

Enterobius - PinwormFigure 12.29

Diagnosing Pinworm Disease

Necator or Ancylostoma - Hookworm

The Life Cycle of the Hookworms Ancylostoma duodenale and Necatur americanus

Trichinella

Filariasis is a lymphatic system infectionWuchereria bancroftiLife cycleTransmission by mosquitoSymptomsElephantiasis

Platyhelminthes - FlatwormsTrematodes Flukes - nonsegmentedSchistosoma - blood fluke; Swimmers itch

Cestodes Tapeworms - segmentedTaenia beef or pork tapewormEchinococcus wild dog tapeworm

Trematodes - FlukesFigure 12.25

Schistosoma blood fluke

Cestodes - TapewormsFigure 12.27Tapeworm parts:Scolexhead with attachment siteProglottids body segments with testes and ovaries

Taenia saginatabeef tapewormTaenia solium pork tapewormcysticercosis

A few other tapeworms also cause diseaseHymenolepis nana, the dwarf tapeworm, most common human tapeworm worldwideEchinococcus granulosus, the dog tapeworm, humans are intermediate hosts

EchinococcusFigure 12.28

Arthropods as VectorsKingdom: AnimaliaPhylum: Arthropoda (exoskeleton, jointed legs)Class: Insecta (6 legs)Lice, fleas, mosquitoesClass: Arachnida (8 legs)Mites and ticksMay transmit diseases (vectors)Figure 12.31, 32

Arthropods as VectorsFigure 12.33

Arthropod VectorsFigure 23.24

Scabies - mite

ArachnidsAdult arachnids have four pairs of legsTicks and mites resemble each other morphologicallyTicks are the most important arachnid vectorsServe as vectors for bacterial, viral, and protozoan diseasesSecond only to mosquitoes in the number of diseases they transmitHard ticks are the most prominent disease vectorTransmit Lyme disease, Rocky Mountain spotted fever, tularemia, relapsing fever, and tick-borne encephalitis

ArachnidsParasitic mites are found wherever humans and animals coexistTransmit rickettsial diseases among animals and humans

InsectsAdults have three pairs of legs as well as a head, thorax, and abdomenFleasMost fleas are not associated with humans but a few do feed on humansPlague is the most significant disease transmitted by fleasBody liceParasites that can also transmit diseaseMost common among poor or overcrowded communities

InsectsFliesAmong the most common insectsThose that transmit disease are generally bloodsuckersMosquitoesMost important arthropod vector of diseaseCarry some of the worlds most devastating diseasesKissing bugsOften take blood meals near the mouth of their human hostsFeed on blood nocturnally while the host sleeps

Eukaryotic Microbe ParasitesProtozoa AmoebaEntamoeba histolyticaNaegleriaAcanthamoebaFlagellatesGiardia lambliaTrichomonas vaginalisTrypanosomaLeishmaniaCiliatesBalantidium coliSporozoaPlasmodiumCryptosporidiumToxoplasma

HelminthsRoundwormsIntestinalAscaris lumbricoidesEnterobius vermicularisNecatur americanusTissueTrichinella spiralisWucheraria bancrofti

FlatwormsFlukesSchistosomaTapewormsTaenia

ArthropodsInsectsArachnids