Chapter 12: Parasites Flashcards
Parasite
organism that lives off host, and uses host to replicate and reproduce
-Protozoa
-helminths
Vector
arthropod or insect that will transmit the parasite to the host
Parasitic infections: digestive system
-stool sample
-wet mount
Parasitic infections
-Vectors may transmit the parasite
-malaria
-Intermediate host and definitive hosts may harbor stages of the parasite
Life cycle of protozoa
-Mobility: flagella, cilia, pseudopods
1) Trophozoite (active, feeding stage); reproducing stage, motile; irregular shape
-Drying, lack of nutrient, loses motility>
2) early cyst wall formation
3) Round to oval cyst- infectious stage, non motile, dormant and resistant to disinfectant: mature cyst (dormant, resting stage)
-Moisture, nutrients restored
4) cyst wall breaks open
Trophozoite is reactivated (then back to stage 1)
Flagellates: Giardia duodenalis (formerly lamblia)
-giardiasis
-protozoa
-Trophozoite
-Teardrop/pear shape
-Includes adhesive, sucking disc- attach to host, digest cells and tissue fluids
-may ➖intestinal absorption
-Reservoir: water, soil, small mammals
-Transmitted by oral/fecal route
-Water
-Feces
-Vegetables
-found in small intestine of humans and other mammals
-Life cycle of Giardia duodenalis
-signs and symptoms: Chronic non-bloody greasy, fatty diarrhea, vomiting, nausea, abdominal pain, gas, malabsorption syndrome
1) cyst are ingested (fecal oral route)
2) trophozoites emerge as flagellates in the small intestine
3) Trophozoites live on the surface of villi
-Normal villi vs. flattened villi
-hosts= beavers, small mammals, humans
4) Trophozoites adhere to intestinal lining using suckers
5) cysts pass in feces (then back to stage 1)
-Giardia duodenalis- cyst
-Trichrome cyst
-Nuclei- red
-Rest or cyst blue
-Outbreaks of giardiasis
-Daycare centers, swimming pools
-Dx of Giardiasis
-Microscopic exam of stool for cysts or trophozoites
-ELISA (giardia antigen) or FA test
-Direct fluorescent-labeled antibodies combine w/ antigen (fluorescent microscopy)
-PCR test- amplify nucleic acid
-Giardiasis
-Treatment: metronidazole (Flagyl), Nitazoxanide
-Prevention: handwashing, personal hygiene, filtration, boiling to destroy cysts
-often identified because of cysts in feces
Flagellates: Trichomonas vaginalis
-protozoa
-urethritis/vaginitis- trichomoniasis
-often accompanied by gonorrhea
-in response to infection, body accumulates leukocytes at infection site
-Found in semen or urine of male carriers
-Causes urinary and genital tract infections
-Sexually transmitted
-Parasite relies on estrogen (therefore, men do not have symptoms)
-Signs and symptoms: vaginal itching, green vaginal discharge with fishy odor
-Dx: wet mount, DNA probes, serology (antigen), culture (in anaerobic conditions)
-discharge sample
-Treatment: metronidazole
-Trophozoite only, no cyst (disadvantage)
-lacks mitochondria
-does not have cyst stage
-found in vagina and male urinary tract
Apicomplexa
-Nonmotile, intracellular parasites Replicate inside cells
-Complex life cycle
-Plasmodium- malaria
-Toxoplasma gondii
-Cryptosporidium- chronic diarrhea
Plasmodium
-Is the causative agent of malaria
-Grows by sexual reproduction in Anopheles mosquito, the definitive host
-A human is the intermediate host
-Anopheles mosquito vector transmits malaria
-Blood transfusion- rare transmission method
-Saliva of mosquito contains sporozoites
-Malaria signs and symptoms: intermittent fever, chills, night sweats, headaches, vomiting, hepatomegaly, splenomegaly, hemolytic anemia, dry cough, coma
-Lab dx: malaria
-Giemsa or Wright stain
-Plasmodium vivax, falciparum (malignant- coma when enters brain), malariae, ovale (relapse)
-Dx: examine Giemsa-stained blood smears for ring-forms of Plasmodium
-Malaria is serious problem in tropics of Asia and Africa
-Treated w/ quinine derivatives (chloroquine) and derivatives of artemisinin
-Malaria prevention for travelers
Mefloquine (larium) or Malarone Prophylaxis
-Malaria Prevention
-Sleeping under bed nets- treated w/ repellent
Toxoplasma gondii
-toxoplasmosis
-Transmission: ingestion of oocysts (infectious form derived from cyst- resistant to disinfectant)- fecal-oral
-From cat feces- through cat litter
-Tachyzoites infect liver cells
-Reproducing tachyzoite stage- could cross placenta from mother to fetus
-Hydroencaphalitis in newborns
-Intermediate hosts: cattle, human, mouse
-Definitive Host: cat
-Healthy individuals are asymptomatic
-Healthy host: cyst formation
-Immunocompromised host: brain lesion (ring-enhancing lesion)- HIV pt
-Va impairment- if spreads to eye
-Swollen lymph node
-Congenital infections
-Reservoir: soil, environment
-Pregnant women should not clean litter box
-Dx:
-Serology/immunofluorescence: Detect antibodies in pt’s serum- immunofluorescence (IFA) - see tachyzoite
-PCR: false (+/-) possible
-Treatment: pyrimethamine used w/ other drugs; targets tachyzoites
-Prevention: avoid cat litter, indoor cat, dry cat food, and handwashing
Cryptosporidium hominis
-Cryptosporidiosis
-Immunocompromised are susceptible
-Signs and symptoms: watery/explosive diarrhea, dehydration, vomiting, nausea, abdominal pain, may lead to shock in immunocompromised pt’s
-Transmission: water- swimming in pool (fecal-oral)
-From defecation in pool
-Common in water
-Dx:
-Modified Acid-fast stain of oocysts in feces
-Stain red (acid-fast)
-Antigen test (ELISA)- false (+/-) possible
-PCR
-Serology: Fluorescent antibody (FA) stain: oocyst and giardia cyst visible
-Treatment: fluid and electrolyte replacement
-Prevention: avoid public pools, boiling contaminated water
Helminths
-multicellular
-eukaryotes
-Roundworms (nematoda)
-Pinworm, hookworm, Ascaris
-Flatworms (platyhelminthes)
-Cestodes (tapeworms)
-Trematodes (flukes)
Enterobius vermuclaris
-round worm/pinworm
-life cycle
1) eggs are ingested (released by worm)
-Resistant to disinfectants
2) Larvae hatch in small intestine and migrate to colon
3) adult matures in colon and migrates to anus at night
-Larva mate
4) adult female lay eggs on perianum
5) Autoinoculation
-Signs and symptoms: (nocturnal peri)anal itching, itching, insomnia, weight loss
-Most common in children
-Daycare centers
-Will most likely infect entire household
-Definitive host: humans
-Transmission: ingestion of eggs -Treatment: mebendazole*- interfere w/ nutrient absorption of worm, Pyrantel pamoate
Prevention: handwashing
Dx:
cellophane tape on perianal area, clean glass slide- iodine on slide- 40x under microscope
Football shape
At home can also been seen w/ flashlight
Cyst vs. trophozoite
In the context of protozoan life cycles, a trophozoite is the active, feeding, and multiplying stage, while a cyst is a dormant, protective stage
Defining characteristics of Protozoa
-unicellular eukaryotes
-5 micrometers
-most live on their own
-exception: some- parasitic, requires host for nutrients
-motile- via flagella,cilia, pseudopods
-some are photosynthetic (ex. Euglena)
-reproduce sexually or asexually
-lack cell wall- this trait allows for flexibility and movement
-(chemo)heterotrophic
Intermediate host
an organism that harbors a parasite during a part of its life cycle, where the parasite undergoes development or asexual reproduction, but not sexual reproduction
Definitive host
an organism which supports the adult or sexually reproductive form of a parasite.
List the distinguishing characteristics of parasitic helminths
-chemohetertroph
-eukaryotic
-multicellular
-2 groups:
-flatworms (platyhelminthes)
-roundworms (nematoda)
-could be dioeicious (male or female) or monoecious (both male and female)
-similar to humans
