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protozoa parasites Flashcards

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1
Q

protozoa

A

unicellular eukaryotes, free- living or parasitic
feed on organic matter
most multiply but binary fission

2 major modes of transmission

  • ingestion of protozoa ( infective stage)
  • arthropod vector
  • *** some are transmitted through sexual contact
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2
Q

groups of protozoa ( based on motility)

A

Amebae - move by means id pseudopodia

flagellates - move by means of flagella ( one -to-multiple)

Ciliates - move by means of many cilia on the cell surface

Sporozoa ( Apicomplexa) - lack pseudopodia, flagella & cilia but move using a gliding mechanism that use adhesion & small static myosin motors

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3
Q

Amebae

A

contain pseudopodia ( cytoplasmic protrusions)

are free living & can be pathogenic or non pathogenic

often found in the lower GI tact however may be in other areas

Trophozoites are the motile, reproducing & feeding stage

Cysts are the non- motile, non-feeding infective stage

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4
Q

Entamoeba histolytica ( found where and how is spreads)

A

major pathogenic species of amebae

intestinal amebic dysentery- bloody diarrhea &/or mucus in feces

both stages( trophozoite & cyst) may be found in fecal specimens

can cause extraintestinal amebic infections- liver, lungs, brain or other tissues

  • parasites penetrate the intestinal wall & spread through the blood
  • can be fatal
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5
Q

Entamoeba histolytica identification

A

ID is based in nuclear & intracellular structures seen in a permanent stain ( Trichrome)

rapid & unidirectional movement 
size 10-20µm ( cyst & troph) 
# of nuceli 1, 2 or 4 ( cyst) 
                     1   (troph) 
nuclear appearance : small central karyosome with even chromatin

cytoplasmic inclusions : cyst- cigar sahped chromatoid body
troph- RBCs ( ingestion) **

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6
Q

non pathogenic ameba

A

Entamoeba dispar - morphologically identical to E.histolytica except
E.dispar is non invaseive & will never ingest RBCs
Entamoeba coli
Entamoeba hartmanni
Entamoeba nana
Lodamoeba butschlii

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7
Q

Entamoeba histolytica disease names & symptoms

A

disease names

  • Amebiasis
  • Amebic dysentery
  • Amebic hepatitis ( when liver is involved)

symptoms
- asymptomatic
- abdominal discomfort, malaise, diarrhea &/or constipation or bloody
dysentery & fever
- amebic hepatitis - enlarged liver, fever, chills & leukocytosis

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8
Q

Entamoeba histolytica method of diagnosis & specimen requirements

A

recover & identify trophozoites or cysts in feces or intestinal mucosa

Specimen Requirements:
At least 3 fresh stool specimens should be examined for the presence of
parasites
- stained smear & concentration procedure
- a wet mount may be preformed on wet liquid or soft stool ( motility)

Sigmoidoscopy - 6 different sites
- stained smears from each site

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9
Q

Entamoeba histolytica other tests & treatment

A

tests

  • antigen based immunoassays- fresh or frozen fecal samples
  • serological methods- extraintestinal infections

treatment

  • dependant on infection site
  • all positive cases should be treated
  • Iodoquinol, Paromomycin, Metronidazole, Dehydroemetine or combinations
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10
Q

Entamoeba histolytica general points

A

can be found worldwide

chronic infections can last for years

onset may be gradual or sudden & is characterized nu blood tinged mucus dysentery with up to 10 stools/ day

sudden onset cases mimic appendicitis

now considered a sexually transmitted disease

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11
Q

Opportunistic amebae

A

found in fresh & salt water, moist soil & decaying vegetation

may lead to serious complications in humans

  • Naegleria fowleri
  • Acanthamoeba spp.
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12
Q

Naegleria fowleri

A

ameboflagellate

  • can alternate from an amebae phase & form 2 flagella
  • only ameboid phase found in host

often occurs during summer

enters through nasal mucosa during water activities in ponds & lakes

migrates along olfactory nerves & within days can invade the brain

thermophilic & can tolerate chlorinated water

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13
Q

Naegleria fowleri symtoms

A

infection state ( primary amebic meningoencephalitis)

  • rapid & usually fatal
  • headache, fever,nausea, vomitting (1-2days)
  • progress irrational behaviour, coma & death ( within 6 days)
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14
Q

Naegleria fowleri Identification

A

often diagnosed during autopsy

CSF- always STAT
- often purulent with high # of neutrophils (200-20,000/µmol) w/o bacteria
present
- active trophozoites in unstained preps
- Giemsa or trichrome stains may help with identification
- Ameboid form: elongated with tapered posterior ( 7-20µm)
- Rounded form: large central nuclear karyosome & granular, vacuolated
cytoplasm (15µm)

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15
Q

Naegleria fowleri treatment

A

usually unsuccessful

some cases, Amphotericin B & Sulfadiazine have been effective when administered promptly

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16
Q

Acanthamoebia spp. location & symptoms

A

granulomatous amebic encephalitis- chronic form of meningoencephalitis

slow onset of symptoms

isolated from upper respiratory tract of healthy individuals

occur through either inhalation of contaminated dust or aerosols or through invasion of broken skin & mucous membranes

have been found in lungs, nasal & sinus passages, eyes, ears, skin lesions & vagina

Acanthamoeba keratitis has be linked to poor contact lens care-contaminated saline cleaning solution or wearing lenses while swimming
- corneal scrapings can be cultured for diagnosis

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17
Q

Acanthamoebia spp. cyst, troph & treatment

A

cyst

  • resistant to chlorination & drying
  • 10-25µm
  • round with a single nucleus & a double wall ( outer wall slightly wrinkled )

Trophozoites
- spine-like pseudopodia, not motile

treatment
- treatment of keratitis is often successful but CNS infections rarely respond to
therapy
- antimicrobial sensitivities vary

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18
Q

Flagellates

A

contain flagella

genera may live in the gastrointestinal tract, bloodstream or other tissues

common species include:

  • Giardia lamblia ( Pathogenic- gastrointestinal)
  • Dientamoeba fragilis ( Pathogenic- Intestinal)
  • Chilomastix mesnii ( Non-Pathogenic- intestinal)
  • Pentatrichomas hominis ( Non-Pathogenic- intestinal)
  • Trichomonas vaginalis ( Pathogenic-VAgina & Urethra)
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19
Q

Giardia Lamblia

A

Most common intestinal protozoa in North America ( traveler’s Diarrhea)

Acquired from ingestion of infective cysts- contaminated food or drink

Giardiasis causes diarrhea with no blood, mucus or exudate

Trophozoites are tear-drop shaped

  • bilaterally symmetric with two anterior nuclei & eight flagella
  • “sucking disk” concavity on ventral side ( means of attachment)

children are most frequently affected or travelers to foreign countries

locally, infection is called “beaver fever”

flagella
- 4 pairs- anterior, ventral, lateral & posterior

Motility- characteristic slow oscillation about the long ( like a falling leaf )

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20
Q

Giardia Lamblia Identification

A

wet preps
Trophozoites
- Progressive, “falling leaf” motility
- pear-shaped body with attenuated posterior end

Cysts( unstained)
- ovoid body shape, numerous refractive threads in cytoplasm

21
Q

Giardia Lamblia Disease names & symptoms

A

disease names

  • Giardiasis
  • traveler’s diarrhea

Symptoms

  • Absominal pain
  • Foul smelling diarrhea & gas ( rotten eggs)
  • Mechanical irritation of intestinal mucosa with shortening of villi & inflammatory foci
  • Malabsorption syndrome may occur in heavy infections
22
Q

Giardia Lamblia method of diagnosis & Specimen requirements

A

recover & identify trophozoites or cysts in feces or duodenal contents

Specimen requirements:

At least 3 stool specimens should be examined for the presence of parasites

  • stained smear prepared & examined
  • Examine areas of mucus in feces for presence of parasites

String test may be used if fecal examinations are negative
Antigen based immunoassays on fecal samples

23
Q

Giardia Lamblia treatment & General Points

A

treatment

  • Quinacrine
  • Metronidazole or Furazolidone

general points

  • can be found worldwide
  • outbreaks have been related to cross contamination of water & sewage systems & contamination of streams by wild animals (beaver)
  • travellers to endemic areas suffer symptoms while residents generally do not
24
Q

Dientamoeba Fragilis

A
  • Associated with cases of diarrhea
  • Believed to be acquired from hand to mouth transfer from
    infective individuals
  • lives in cecum & colons
  • does not form cysts
  • Trophozoite has two nuclei connected by a division spindle filament
  • no observable flagella
  • moves by means of pseudopodia when seen in feces ( sluggish nondirectional motility )
25
Q

Dientamoeba Fragilis symptoms, diagnosis & specimen requirements

A

symptoms

  • usually asymptomatic
  • may be associated with diarrhea , anorexia & abdominal pain

diagnosis
- identify trophozoites in feces ( no cyst stage)

specimen requirements

  • at least 3 stool specimens should be examined for presence of parasites
    • stained smear prepared & examined for trophozoites
    • Trophozoites can be found in formed stools
26
Q

Dientamoeba Fragilis Treatment & general points

A

treatment : Iodoquinol, Tetracycline or Paramomycin

General points

  • can be found worldwide
  • in some areas, D.fragilis is more common than G.lamblia
  • Most organisms have two nuclei but some only have one
27
Q

Trichomonas Vaginalis ID/ size

A
  • Genitourinary parasite of both men & women
  • Transmitted by direct sexual contact
  • Do not form Cysts
  • Motile trophozoites may be identified in fresh urine or in smears of vaginal & uretheral discharge
  • Large anterior nucleus , four anterior flagella, an axostyle & an undulating membrane ( a thin sheet of protoplasm which joins the body)
  • characteristic structure, jerky motility & “rippling” motion help ID
  • usually 3-15µm but can reach 30 µm ( approx. size of WBC)
28
Q

Trichomonas vaginalis disease name & symptoms

A

disease names

  • Trichomonad vaginitis
  • urethritis
  • Trich

Symptoms
women- persistent vaginal inflammation
- yellowish frothy, foul discharge
- itching & burning on urination
men- usually asymptomatic

29
Q

Trichomonas vaginalis diagnosis & specimen requirements

A

diagnosis
- recover & identify motile trophozoites in fresh urethral discharge vaginal smear or urine

specimen requirements

  • fresh vaginal or urethral discharges or prostatic secretions are examined as a met mount ( jerky “rippling” motility)
  • urines ( centrifuged) may be examined
  • multiple specimens may be required before diagnosis is confirmed
  • specimens must never be refrigerated for either culture or wet mount
30
Q

Trichomonas vaginalis treatment & general points

A

treatment : Metronidazole

points
- T. hominis may be found as a fecal contaminant in urine samples that are examined fro T. vaginalis - correct ID of species is extremely important

31
Q

Trypanosoma spp.

A

Trypanosoma brucei

  • flagellated protozoa in the bloodstream; hemoflagellates
  • transmitted through arthropod ( fly bite) & infect the blood which can lead ot systemic disease

T.b. rhodesiense
- east african sleeping sicjness

T.b. gambiense
- west african sleeping sickness

32
Q

Trypanosoma spp. symptoms

A 
lesion at the bite site ( chancre) 
enlarged lymph nodes 
fever, headache, night sweats 
joint & muscle pain 
CNS impairment 
Lethargy & motor changes 
Coma 
Cardiac failure 
Death
33
Q

Trypanosoma spp. method of diagnosis

A
  • examine fluid bite sight chancre or the buffy coat of blood for trypomastigotes during febrile period ( trypomastigote form in plasma is diagnostic)
  • thick blood smears increase the chance of diagnosis
  • multiple whole blood specimens may be needed
  • thick & thin blood smears are stained with Giemsa or Wrights stain
  • later stage of infection- trypomastigotes are best found in the lymph nodes or CSF
  • animal inoculation may be helpful with detecting trypomastigotes
34
Q

Trypanosoma spp. Diagnostic stage, treatment

A

diagnostic stage

  • trypomastigotes form in plasma is diagnostic
  • may be seen dividing in peripheral blood

treatment

  • will depend on phase of disease ( early or late)
  • dont need to know drugs
35
Q

Trypanosoma spp. general points

A
  • primarily found in east or west Africa
  • RBC autoagglutination is commonly observed in vitro
  • high levels of both IgM & spinal fluid proteins
  • IgM in spinal fluid is diagnostic
  • enzyme-linked immunosorbent assay ( ELISA) method to detect antigen in serum & CSF is usually for clinical staging of the disease & evaluating therapy
36
Q

Trypanosoma cruzi

A

found in central & south America

causes the debilitating condition called Chagas’ disease
- can result in an enlarged heart, esophagus & colon & man lead to death

Transmitted by Triatoma spp. bug ( intermediate host)

37
Q

Trypanosoma cruzi . symptoms

A

In chronic cases, may be no history of acute illness but an enlarged weakened heart may cause sudden death

Symptoms: fever, weakness& enlarged spleen, liver & lymph nodes

Acute infection ( most common in children ) results in initial reactions at bite site, cardiac ganglia destruction, megacolon & often rapid death

38
Q

Trypanosoma cruzi Method of diagnosis & diagnostic stage & treatment

A

method of diagnosis

  • find amastigotes in stained tissue scraping of skin lesion at bite site
  • identify C-shaped trypomastigotes in blood smear during acute symptoms
  • allow uninfected bugs to feed on patient, then later examine bug feces for parasite (xenodiagnoses)
  • serology testing
  • culturing
  • PCR techniques

diagnostic stage

  • amastigotes occasionally found in heart muscle, liver or CNS in macrophages
  • Trypomastigotes occasionally found in blood smear
  • will not be seen dividing in blood

treatment
- Nifurtimox

39
Q

Trypanosoma spp. general points

A
  • found primarily in Mexico, Central America & South America ( more cases
    being reported in Southwest regions of USA)
  • Many animals serve as reservoir hosts in the warmer southwestern states of
    North America
  • Triatoma spp. feed at night on warm blooded hosts, frequently on the
    conjunctiva of the eye
  • T.cruzi can cross the placenta & cause the disease prenatally
  • Donor blood must be tested using two different serologic tests for evidence
    of infection
40
Q

Plasmodium spp.

A

Sporozoa - Obligate endoparasitic protozoa with no apparent organelles of locomotion

  • most species produce a spore from that is infective for the definitive host after it is ingested or injected by a biting arthropod vector
  • life cycle includes both sexual & asexual phases of reproduction
  • most have a two host life cycle

view cycle in powerpoint lecture 3

41
Q

Plasmodium spp. 5 species

A 
P. vivax ( 80% of infections ) 
P. falciparum 
P. malariae 
P. ovale 
P. knowlesi
42
Q

Plasmodium spp. terms to know with cycle

A

vector is the female anopheline mosquito
parasites feed on RBC hemoglobin as they mature

merozoite- is the young trophozoite

Schizont- is a trophozoite with dividing nuclei

Mature schizont- contains merozoites that invade RBCs

Gametocytes - includes mature male or female merozoites

43
Q

Plasmodium vivax

A

Causes benign tertian malaria

widely distributed in the tropics, subtropics & temperate zones

characteristics:

  • infection of young cells
  • enlargement of RBCs
  • Schuffner dots
  • Delicate ring
  • Very amoeboid trophozoites
  • Schizont containing 12-24 merozoites

relapses occur

paroxysms may cycle every 48hrs

resting stages are called hypnozoites

44
Q

Plasmodium ovale

A

central west Africa & some South Pacific islands

characteristics

  • infection in young cells
  • enlargement of RBCs with fimbriated edges ( oval)
  • early appearance of Schuffner dots
  • smaller ring than P. vivax
  • Schizont containing eight merozoites

relapses are possible but with spontaneous recovery

Paroxysms cycle every 48 hrs

45
Q

Plasmodium malariae

A

causes quartan malaria

is sporadically distributed

may be associated with nephrotic syndrome

characteristics:

  • infection of older cells
  • normal size RBCs
  • no stippling
  • thick ring, large nucleus
  • Trophozoites that form “bands” across the cell
  • Schizont containing 6 to 12 merozoites

no relapses occur, but recrudescence is recognized

paroxysms cycle every 72 hrs

46
Q

Plasmodium falciparum

A

causes malignant tertian malaria

confined to tropical areas

characteristics include:

  • invasion of all stages of RBCs ( heavy parasitemia)
  • comma-like red dots (maurer dots)
  • multiple ring forms, some applique forms
  • crescent-shaped gametocytes
  • fever cycles every 36 to 48 hrs

no relapses occur

vessels of organs become plugged, causing fatal complications (e.g black water fever)

47
Q

Plasmodium spp. method of diagnosis

A

method of diagnosis:

Thick & thick blood films ( gold standard )
- between 200 & 300 oil immersion fields are examined
- Giemsa or wright stain is acceptable
- ethylenediaminetetraacetic acid (EDTA) anticoagulant tubes are
preferred

rapid malaria tests are now available ( dipstick, cartridges)

polymerase chain reaction (PCR) with specific deoxyribonucleic acid (DNA) probes is used

automated instruments are not designed to detect intracellular parasites

48
Q

Plasmodium spp. treatment

A 
chloroquine 
Quinine 
Pyrimethamine 
Sulfadiazine 
Tetracyline 
**Chloroquine resistant P.falciparum is present in most endemic areas

Microbiology 2 (22 decks)

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