Parasitology Exam 4: Coccidia, Amoeba, Flagellates + Ciliates Flashcards
What is the class/phylum/subkingdom of Coccidia? What does each classification indicate?
Class: Coccidia
Phylum: Sporozoa (Apicomplexa) –> Indicates there is an apical complex and intracellular parasites
Subkingdom: Protozoa –> Indicates they are unicellular
Describe Coccidia as a whole.
Unicellular
Obligate intracellular parasites
Have an apical complex
What is an apical complex?
Organelle used for host cell penetration and establishment of the intracellular parasitism
What are the intestinal coccidia?
Cryptosporidium sp.
Cystoisospora belli
Cyclospora cayetanensis
What are the tissue coccidia?
Sarcocystis sp.
Toxoplasma gondii
What are the 2 pertinent Cryptosporidium species and what do they each primarily infect?
Cryptosporidium parvum –> mammals in general, including humans
Cryptosporidium hominis –> humans
Cannot differentiate between these 2 species morphologically
Cryptosporidium infects BOTH ___________ and __________ individuals.
Immunocompromised AND immunocompetent
Briefly describe the Cryptosporidium life cycle!
- Oocysts ingested
- Oocytes release sporozoites which invade epi cells
- Development into trophozoites
- Trophozoites undergo asexual amplification called merogony to form meronts which contain merozoites
- Merozoites undergo gametogony to form sexual gametocytes
- New oocysts formed in epi cells via sporogony
What is a parasitophorous vacuole?
Layers of endoplasmic reticulum around an intracellular parasite
Thin-walled vs thick-walled oocysts
Thin-walled: ~20%, excyst in the digestive tract, associated with autoinfections
Thick-walled: ~80%, excreted in the environment, resistant to low temperature, salinity, and most disinfectants
What is the ONLY extracellular stage in cryptosporidium life cycle?
Oocysts
Transmission of Cryptosporidium sp.
Direct contact w/ infected people or animals
Consumption of contaminated water or food
Oocysts are IMMEDIATELY infectious when passed in stool
What is the infective and diagnostic stages of Cryptosporidium?
Infective: Oocysts
Diagnostic: thick-walled oocysts in feces
Briefly describe the disease associated with Cryptosporidium in immunocompetent vs immunocompromised individuals.
Immunocompetent: diarrhea, nausea, low-grade fever (self-limiting)
Immunocompromised: renal failure patients or renal transplant patients can experience life-threatening diarrhea and AIDS patients can experience extraintestinal infections
Lab diagnosis of Cryptosporidium
Modified acid fast stain (bright red oocysts against blue background)
OR
DFA with Giardia (Crypto will appear smaller than Giardia)
OR
H&E staining in jejunum
Reporting/Prevention of Cryptosporidium
Cryptosporidiosis = reportable disease in the US, positive diagnosis should be sent to reference lab for confirmation
Prevention: highly resistant to most commercial disinfectants, chlorine can dramatically decrease the oocysts but almost pointless due to exposure time and concentration needed
Infectious/diagnostic stage of Cystoisospora belli
Infective: sporulated oocyst –> releases sporozoites
Diagnostic: oocysts in feces
Transmission of Cystoisospora belli
Ingestion of food or water contaminated with water, sporulated oocysts
Cystoisospora belli disease
Diarrhea
Doctors should consider C. belli infection in AIDS patients who . . . .
- Have immigrated from or traveled to Latin America
- Are Hispanics born in the US
- Are young adults
- Have not received prophylaxis for Pneumocystis infection
Cystoisospora belli lab diagnosis
Modified acid fast stain of oocysts in stool
H&E stain on histology specimen
Cystoisospora belli reporting/prevention
Quantitation NOT required, but should be reported if seen in stool
Prevention = improve hygiene, improve sanitary conditions
Cyclospora cayetanensis host
ONLY HUMANS
Cyclospora cayetanensis infective/diagnostic stages
Diagnostic stage = UNSPORULATED oocysts
Infective stage = SPORULATED oocysts
Transmission of C. cayetanensis
Fecal-oral - associated with ingestion of contaminated fruits and vegetables
Disease of C. cayetanensis
Flulike illness
May be associated with biliary disease
C. cayetanensis lab diagnosis
Oocysts are variably acid-fast, may contain granules or have a bubbly appearance (“wrinkled cellophane”)
C. cayetanensis reporting/prevention
- Report to local public health authorities AND CDC
Prevention: wear gloves when gardening, wash your produce thoroughly
2 relevant Sarcocystis species
Sarcocystis hominis
Sarcocystis suihominis
Definitive and intermediate hosts of Sarcocystis species
Both species definitive hosts = humans
Intermediate host of S. hominis = cattle
Intermediate host of S. suihominis = pigs
Describe the infection process of Sarcocystis species.
Intermediate hosts (cows and pigs) infected via ingestion of sporocysts excreted in the feces of definitive hosts.
Definitive hosts infected via ingestion of mature cysts found in the muscles of intermediate hosts.
Diagnostic/infective stage of Sarcocystis species
Diagnostic: sporocysts in stool
Infective: ingestion of sporocysts
Disease of Sarcocystis species
Sarcocysts develop in human muscle after ingestion of oocysts
Few problems/evidence of being infected
Patients MAY develop muscle swellings with erythema of overlying skin
Lab ID of Sarcocystis
Human fecal specimens containing sporocysts
Biopsy specimens containing sarcocysts (mostly cardiac and skeletal muscle) after ingestion of beef or pork
Sarcocystis sp. Reporting/Prevention
Reporting = cannot differentiate species, ID should be confirmed by reference lab
Prevention = thoroughly cook meat, careful disposal of animal feces
Definitive host of Toxoplasma gondii
Cats
How are cats infected with Toxoplasma gondii?
Ingestion of oocysts or carnivorism (outdoor cats more likely to become infected)
3 infectious stages of Toxoplasma gondii
Tachyzoites - rapidly multiply
Bradyzoites - in tissue cysts, slowly multiply
Sporozoites - in oocysts of cat feces
Differentiate between tachyzoites and bradyzoites (T. gondii)
Tachyzoites - rapidly multiply, crescent shaped, one end more rounded than the other
Bradyzoites - slowly multiply, strong PAS positive
T. gondii disease
Toxoplasmosis can be categorized into 4 groups -
Acquired in immunocompetent patient –> usually asymptomatic
Acquired or reactivated in immunocompromised patient –> CNS primarily involved (altered mental state)
Congenital –> can pass to baby and cause microcephaly, etc. (This is why Kristen cannot change cat litter)
Ocular –> chorioretinitis
T. gondii lab diagnosis
Most common method is serological diagnosis through antibody testing
2 situations where T. gondii detection is very significant :
- Tachyzoites in smears/tissue cultures inoculated from CSF
- Tachyzoites in patients with acute pulmonary disease and demonstration of tachyzoites in BAL fluid
What group are Flagellates?
Mastigophora
Describe flagella as a whole
Have specialized locomotor organelles called flagella (long, thin, cytoplasmic extensions)
May infect intestinal tract, bloodstream, or tissues
Distinctive criteria for ID of:
Giardia duodenalis
Chilomastix mesnili
Trichomonas spp
Giardia –> sucking disk and axonemes
Chilomastix –> cytostome and spiral grove
Trichomonas –> undulating membrane
Types of pathogenic Intestinal flagella
Giardia duodenalis
Dientamoeba fragilis
Types of pathogenic urogenital flagella
T. vaginalis
What is the most common cause of intestinal infection worldwide?
Giardia duodenalis
Types of non-pathogenic intestinal flagella
Chilomastix mesnili
Pentatrichomonas hominis
Describe the life cycle of Giardia duodenalis including diagnostic and infective stages
Trophozoite and cyst stages –> ingestion of infective cysts from contaminated food/water (infective stage)
Trophozoites are produced and divide by longitudinal binary fission that produce two daughter trophozoites
- Trophozoites attach to intestinal epithelium of the host villi using their ventral sucking disk, leave impression prints
Giardia epidemiology (transmission, hosts, affected populations)
Transmission: ingestion of viable cysts
Beavers are a common reservoir host
Associated with travelers and campters
What is the disease of Giardiasis like?
GI disease that has stools with lack of blood, mucus, and cellular exudate
Giardia lab diagnosis
Entero-test capsule or duodenal aspirates can be used for recovering organisms
Antigen detection using DFA
Describe the trophozoite of Giardia
Pear shaped, looks like old man
Sucking disks, median bodies, and 8 flagella may also be seen
What is villous atrophy and what is it associated with?
Lack of villi in intestines; degree of atrophy correlates with the degree of malabsorption; associated with Giardia
Reporting and prevention of Giardia
Reporting = may need to examine up to 6 stool samples, positive stool does NOT require quantitation
Prevention = ensure safe drinking water
Describe Chilomastix mesnili (transmission, infection/disease)
Transmitted by ingestion of cysts
Nonpathogenic, does not cause disease
Chilomastix mesnili trophozoite morphology
Distinct oral groove called a cytostome close to the nucleus
Chilomastix mesnili cyst morphology
Curves cytostomal fibril called the shepherd’s crook
Transmission and Affected populations of Dientamoeba fragilis
Fecal-oral route suspected due to presence of cyst stage - associated with helminth eggs
Higher infection rates in mental institutions, missionaries, and native americans in arizona
Infective/diagnostic stage of Dientamoeba fragilis
Infective: fecal-oral route of eggs/cysts
Diagnostic: trophs in feces
Trophozoite morphology of Dientamoeba fragilis
Lacks external flagella!!!
Resembles amoebae but is NOT
Tramission/epidemiology of Paratrichomonas hominis
One of the most commonly identified flagellates (after G. duodenalis and D. fragilis)
Nonpathogenic and noninvasive
NO cyst stage
Transmission probably occurs in the trophic form
Trophozoite morphology of Paratrichomonas hominis
Slender axostyle projects from posterior end
Undulating membrane
5 Flagella (4 anteriorly, 1 posterior)
Describe trichomonas vaginalis (transmission, etc)
Transmitted through sexual intercourse
The most common nonviral STD
Life cycle only includes trophozoite
What is the only natural host for T. vag?
Humans
Preferred vaginal pH for trichomonas
Slightly alkaline
Trophozoite morphology of T. vag
Obvious axostyle that protrudes through the bottom of the organism, slightly unvisible flagella at anterior end
Symptoms of T. vag
Vaginal pruritus, discharge, odor, edema, etc
T. vag lab ID
Often recovered in centrifuged urine sediment
Wet mounts –> must be performed within 10-20 min after sample collection in order to visualize motility
Trichomonas tenax is known as?
Oral trichomonas
Disease of T. tenax
Colonizes patients with poor oral hygiene and periodontal disease
T. tenax is the _______ of the trichomonads
Smallest
Transmission of T. tenax
Saliva, droplet spray, kissing, contaminated dishes or drinking water
lab ID of T. tenax
Mouth scrapings
Describe ciliates as a whole
Move by means of cilia - short extensions of the cytoplasm that cover the surface of the organism
What is the one ciliate that infects humans?
Neobalantidium coli
Ciliates have two different types of nuclei. Describe them
Macronucleus - only one
Micronucleus - one or more
Describe the life cycle of Neobalantidium coli (infective and diagnostic stage)
Infective stage = cyst form
Ingestion of cyst –> excystation –> trophozoites secrete hyaluronidase –> organisms live in small intestine –> cyst formed as trophozoite move down intestine
Neobalantidium coli is widely distributed. What animals would it be found in and what climates?
Hogs in warm temps
Monkeys in tropics
Describe the trophozoite morphology of Neobalantidium coli
Anterior end has a cytostome, two nuclei (one bean shaped macronucleus and one smaller round micronucleus)
Transmission of neobalantidium coli
Ingestion of infective cysts through contaminated food or water
Lab ID of neobalantidium coli
Stool specimens
Therapy of neobalantidium coli
Therapy: tetracycline drugs
Amoebae class
Sarcodina
Describe the amoebae as a class.
Multiply by binary fission
Capable of movement by pseudopods
Usually transmitted through fecal-oral route
Have both trophozoite and cyst stages - cyst = infective stage
What are the pathogenic, free-living amoebae?
Naegleria fowleri
Acanthamoeba sp.
Balamuthia mandrillaris
What are the pathogenic, intestinal amoebae?
Entamoeba histolytica
Blastocystis hominis (controversial)
What is the only pathogenic intestinal amoebae?
Entamoeba histolytica
(Controversial if B. hominis is pathogenic)
Describe Entamoeba histolytica in terms of distribution, affected populations, and transmission.
Worldwide distribution from tropics to Arctics.
Affected: men who have sex with men, travelers, institutionalized
Transmission: Ingestion of cysts from contaminated hands/food
What is considered DIAGNOSTIC for Entamoeba histolytica?
Presence of RBCs in the cytoplasm!!
Describe E. histolytica trophozoite (motility and morphology)
Monopodial (one pseudopod at a time) motility
Centrally located karyosome
Ingested RBCs = diagnostic for E. histolytica
Describe E. histolytica pre-cyst morphology
Single nucleus
2 inclusions: chromatoidal bars with SMOOTH, ROUND edges and glycogen mass
Describe E. histolytica cyst morphology
Can have up to 4 nuclei
Chromatoidal bars with rounded edges still seen
Cyst morphology not used to differentiate Entamoeba species since they all look similar
What is the disease of E. histolytica like?
amebiasis, amebic dysentery, amebic colitis, amebic hepatitis
Lyses host cells and causes tissue destruction
What is trogocytosis?
Adherence to mucosa (E. histolytica) - amoeba takes a bite out of host cellular membrane –> development of amebic ulcers and tissue damage in intestinal tract
E. histolytica lab ID
Start with O&P exam, permanent stained smears are key
Reporting of E. histolytica
Note genus, species, and life cycle stage present
Should report E. histolytica/dispar group
If species ID is not available, physician is responsible to determine if treatment is warranted
E. dispar
morphologically identical to E. histolytica, but is the nonpathogenic form
Can only be determined through molecular analysis
How is Entamoeba coli different from Entamoeba histolytica?
- Not pathogenic
- Does not ingest or invade host tissue
- Cyst chromatoidal bars are IRREGULAR, SPLINTER-SHAPED
- Cyst contains 8 NUCLEI with eccentrically placed karyosome in each
How is Entamoeba hartmanii morphology different from other Entamoeba?
- Mature cyst contains 4 nuclei
- Mature cysts RETAIN THEIR CHROMATOIDAL BARS (not seen in E. histolytica/dispar)
- Smaller and more numerous chromatoidal bars
What is the smallest of the intestine-dwelling amoebae infecting humans? (nonpathogenic)
Endolimax nana
What is standout about Iodamoeba butschlii (nonpathogenic intestinal amoeba) morphology?
Cyst has a LARGE GLYCOGEN VACUOLE
Only one nucleus!
Blastocystis spp. –> what is standout?
Pathogenicity is controversial
May be considered a stramenophile (includes brown algae, slime molds, etc)
4 major forms including central vacuole form –> most common form found in clinical stool samples
What is the most common form of Blastocystis found in clinical stool samples?
Central vacuole form
Reporting of Blastocystis species
SHOULD be quantified
NOT necessary to state the life cycle form present
What causes PAM?
N. fowleri
What causes GAE?
Acanthamoeba spp. and Balamuthia
Acanthamoeba keratitis
related to poor lens care in contact lens wearers
Transmission of Naegleria fowleri
Amoebae enter the nasal cavity by inhalation or aspiration of water containing cysts or trophozoites and migrate via olfactory nerves to the brain
What types of environments does Naegleria fowleri live in?
Freshwater; Highly thermophilic; can survive temperatures up to 45C
N. fowleri disease
PAM (primary amebic meningoencephalitis) –> infection of the brain and meninges that can be rapidly fatal
What is N. fowleri associated with?
Neti pots
Swimming in warm lakes and rivers
What is the specimen of choice for N. fowleri lab diagnosis?
CSF; will show trophozoites; increased protein, decreased glucose high wbc count
NEVER refrigerate
N. fowleri culture
Bacteria are a food source for the amoebae, tracks made by amoeba as it moves across the plate eating the bacteria
Most cases of N. fowleri are diagnosed when?
At autopsy
Trophozoite morphology of Acanthamoeba sp.
Spinelike pseudopods
Single nucleus has a large karyosome
Cyst morphology of Acanthamoeba sp.
Single nucleus, large karyosome, double wall, slightly wrinkled outer cyst wall
What disease is associated with Acanthamoeba sp?
GAE (granulomatous amoebic encephalitis)
NOT associated with swimming such as N. fowleri
Associated with keratitis and unproper care of contact lens
What is the leading risk factor of Acanthamoeba sp infection?
Use of contact lens
Morphology of Balamuthia mandrillaris
3 visible cyst layers
Difficult to differentiate from Acanthamoeba morphologically
Ectocyst – outer, wrinkled
Mesocyst – middle, structureless
Endocyst – inner, thin
Balamuthia disease
GAE, similar to Acanthamoeba
T/F: Balamuthia will leave tracks on an agar plate.
FALSE; does not feed on bacteria like N. fowleri
