protozoa parasites Flashcards
protozoa
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
groups of protozoa ( based on motility)
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
Amebae
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
Entamoeba histolytica ( found where and how is spreads)
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
Entamoeba histolytica identification
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) **
non pathogenic ameba
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
Entamoeba histolytica disease names & symptoms
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
Entamoeba histolytica method of diagnosis & specimen requirements
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
Entamoeba histolytica other tests & treatment
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
Entamoeba histolytica general points
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
Opportunistic amebae
found in fresh & salt water, moist soil & decaying vegetation
may lead to serious complications in humans
- Naegleria fowleri
- Acanthamoeba spp.
Naegleria fowleri
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
Naegleria fowleri symtoms
infection state ( primary amebic meningoencephalitis)
- rapid & usually fatal
- headache, fever,nausea, vomitting (1-2days)
- progress irrational behaviour, coma & death ( within 6 days)
Naegleria fowleri Identification
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)
Naegleria fowleri treatment
usually unsuccessful
some cases, Amphotericin B & Sulfadiazine have been effective when administered promptly
Acanthamoebia spp. location & symptoms
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
Acanthamoebia spp. cyst, troph & treatment
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
Flagellates
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)
Giardia Lamblia
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 )
Giardia Lamblia Identification
wet preps
Trophozoites
- Progressive, “falling leaf” motility
- pear-shaped body with attenuated posterior end
Cysts( unstained)
- ovoid body shape, numerous refractive threads in cytoplasm
Giardia Lamblia Disease names & symptoms
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
Giardia Lamblia method of diagnosis & Specimen requirements
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
Giardia Lamblia treatment & General Points
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
Dientamoeba Fragilis
- 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 )
Dientamoeba Fragilis symptoms, diagnosis & specimen requirements
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
Dientamoeba Fragilis Treatment & general points
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
Trichomonas Vaginalis ID/ size
- 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)
Trichomonas vaginalis disease name & symptoms
disease names
- Trichomonad vaginitis
- urethritis
- Trich
Symptoms
women- persistent vaginal inflammation
- yellowish frothy, foul discharge
- itching & burning on urination
men- usually asymptomatic
Trichomonas vaginalis diagnosis & specimen requirements
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
Trichomonas vaginalis treatment & general points
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
Trypanosoma spp.
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
Trypanosoma spp. symptoms
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
Trypanosoma spp. method of diagnosis
- 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
Trypanosoma spp. Diagnostic stage, treatment
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
Trypanosoma spp. general points
- 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
Trypanosoma cruzi
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)
Trypanosoma cruzi . symptoms
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
Trypanosoma cruzi Method of diagnosis & diagnostic stage & treatment
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
Trypanosoma spp. general points
- 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
Plasmodium spp.
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
Plasmodium spp. 5 species
P. vivax ( 80% of infections ) P. falciparum P. malariae P. ovale P. knowlesi
Plasmodium spp. terms to know with cycle
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
Plasmodium vivax
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
Plasmodium ovale
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
Plasmodium malariae
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
Plasmodium falciparum
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)
Plasmodium spp. method of diagnosis
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
Plasmodium spp. treatment
chloroquine Quinine Pyrimethamine Sulfadiazine Tetracyline **Chloroquine resistant P.falciparum is present in most endemic areas
