protozoa parasites

Question 1

protozoa

Answer 1

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

Question 2

groups of protozoa ( based on motility)

Answer 2

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

Question 3

Amebae

Answer 3

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

Question 4

Entamoeba histolytica ( found where and how is spreads)

Answer 4

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

Question 5

Entamoeba histolytica identification

Answer 5

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) **

Question 6

non pathogenic ameba

Answer 6

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

Question 7

Entamoeba histolytica disease names & symptoms

Answer 7

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

Question 8

Entamoeba histolytica method of diagnosis & specimen requirements

Answer 8

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

Question 9

Entamoeba histolytica other tests & treatment

Answer 9

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

Question 10

Entamoeba histolytica general points

Answer 10

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

Question 11

Opportunistic amebae

Answer 11

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

may lead to serious complications in humans

• Naegleria fowleri
• Acanthamoeba spp.

Question 12

Naegleria fowleri

Answer 12

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

Question 13

Naegleria fowleri symtoms

Answer 13

infection state ( primary amebic meningoencephalitis)

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

Question 14

Naegleria fowleri Identification

Answer 14

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)

Question 15

Naegleria fowleri treatment

Answer 15

usually unsuccessful

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

Question 16

Acanthamoebia spp. location & symptoms

Answer 16

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

Question 17

Acanthamoebia spp. cyst, troph & treatment

Answer 17

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

Question 18

Flagellates

Answer 18

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)

Question 19

Giardia Lamblia

Answer 19

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 )

Question 20

Giardia Lamblia Identification

Answer 20

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

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

Question 21

Giardia Lamblia Disease names & symptoms

Answer 21

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

Question 22

Giardia Lamblia method of diagnosis & Specimen requirements

Answer 22

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

Question 23

Giardia Lamblia treatment & General Points

Answer 23

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

Question 24

Dientamoeba Fragilis

Answer 24

• 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 )

Question 25

Dientamoeba Fragilis symptoms, diagnosis & specimen requirements

Answer 25

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

Question 26

Dientamoeba Fragilis Treatment & general points

Answer 26

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

Question 27

Trichomonas Vaginalis ID/ size

Answer 27

- 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)

Question 28

Trichomonas vaginalis disease name & symptoms

Answer 28

disease names - Trichomonad vaginitis - urethritis - Trich Symptoms women- persistent vaginal inflammation - yellowish frothy, foul discharge - itching & burning on urination men- usually asymptomatic

Question 29

Trichomonas vaginalis diagnosis & specimen requirements

Answer 29

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

Question 30

Trichomonas vaginalis treatment & general points

Answer 30

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

Question 31

Trypanosoma spp.

Answer 31

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

Question 32

Trypanosoma spp. symptoms

Answer 32

``` 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 ```

Question 33

Trypanosoma spp. method of diagnosis

Answer 33

- 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

Question 34

Trypanosoma spp. Diagnostic stage, treatment

Answer 34

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

Question 35

Trypanosoma spp. general points

Answer 35

- 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

Question 36

Trypanosoma cruzi

Answer 36

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)

Question 37

Trypanosoma cruzi . symptoms

Answer 37

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

Question 38

Trypanosoma cruzi Method of diagnosis & diagnostic stage & treatment

Answer 38

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

Question 39

Trypanosoma spp. general points

Answer 39

- 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

Question 40

Plasmodium spp.

Answer 40

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

Question 41

Plasmodium spp. 5 species

Answer 41

``` P. vivax ( 80% of infections ) P. falciparum P. malariae P. ovale P. knowlesi ```

Question 42

Plasmodium spp. terms to know with cycle

Answer 42

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

Question 43

Plasmodium vivax

Answer 43

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

Question 44

Plasmodium ovale

Answer 44

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

Question 45

Plasmodium malariae

Answer 45

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

Question 46

Plasmodium falciparum

Answer 46

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)

Question 47

Plasmodium spp. method of diagnosis

Answer 47

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

Question 48

Plasmodium spp. treatment

Answer 48

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