INTESTINAL AND LUMINAL PROTOZOA

Bushehr University of Medical Sciences

Department: Medical Microbiology and Parasitology

Module: Medical Parasitology (Lecture)

Semester: 2 (1392-93)

Instructor: Dr. Mohammad Rayani

INTESTINAL AND LUMINAL PROTOZOA

Flagellates:

• Giardia lamblia

• Dientamoeba fragilis

• Chilomastix mesnili

• Trichomonas hominis

• Enteromonas hominis

• Retortamonas intestinalis

Ameba:

• Entamoeba histolytica

• Entamoeba dispar

• Entamoeba coli

• Entamoeba hartmanni

• Endolimax nana

• Iodamoeba bütschlii

Apicomplexa:

• Cryptosporidium hominis

• Cryptosporidium parvum

• Cyclospora cayetanensis

• Isospora belli

Other:

• Blastocystis hominis

• Balantidium coli

INTESTINAL PROTOZOA

unicellular eukaryotic organisms

Fecal-Oral Transmission Factors

• poor personal hygiene• food handlers

• children in day care centers

• developing countries• highly endemic

• poor sanitation

• travelers diarrhea

• water-borne epidemics

• zoonosis• Entamoeba = no

• Cryptosporidium = yes

• Giardia = controversial

Control/Prevention

• improve personal hygiene

• especially institutions

• treat asymptomatic carriers

• eg, family members

• health education

• hand-washing

• sanitation

• food handling

• protect water supply

• treat water if questionable

• boiling

• iodine

• not chlorine

Intestinal protozoans

Divided into classes based on motility

Majority live in colon

Few in small intestine - Giardia lamblia , Cryptosporidium

parvum, Isopora belli,

Transmission - direct fecal/oral route

Difficult ID

small size

similar morphological characteristics

Intestinal protozoans cont.

Permanent stained smear - MOST important for ID

Developmental stages

Trophozoite

motile, feeding stage

reproduces by binary fission

Cyst - resistant stage, infective for humans

AMOEBA

Entamoeba

histolytica

dispar

hartmani

coli

gingevalis

Endolimaxnana

Iodamoebabutschlii

Characteristics of Intestinal amebae

Move by cytoplasmic protrusions (pseudopods); most slow,

random motility

Identification based on:

size

number of nuclei

nuclear structure

presence of specific internal structures

Treatment - only Entamoeba histolytica

Amebiasis

Cause: Entamoeba histolytica

A parasitic ameba; class Sarcodina

Transmitted via contaminated food & water

Cysts are shed in the feces

When ingested: Excystation occurs in the intestine

Trophozoites grow & reproduce in the intestinal tract

Symptoms

Abdominal pain

Little diarrhea but often blood in the stool (“amebic

dysentery”)

Possibly of intestinal ulceration; perforation; infection of

internal organs such as liver & lungs

Entamoeba histolytica - Pathogen

Trophozoite

15 - 20 uM

progressive motility

small, central karyosome

fine, evenly distributed chromatin

red blood cells diagnostic

Cyst

mature: 4 nuclei

cigar-shaped chromatoid bodies

Entamoeba histolytica cont.

Only pathogenic ameba

World-wide, 40,000 - 100,000 deaths/year

Transmitted - fecal contamination of food/ water; direct

with dirty hands & objects

Disease: invasive intestinal/extraintestinal infection causing

liver, lung or brain abscesses. Bloody stools, increased liver

enzymes

Treatment: metronidazale

Primary Amebic Meningoencephalitis

Cause: Naegleria fowleri

A fresh water, free living ameba

No cyst stage

Several cases of infections in swimmers

Transmission and Symptoms:

Transmission through the nasal & sinus

passages

Infection of the brain & meninges

Headaches; delirium; seizures

Entamoeba hartmanni (non-pathogen)

Central karyosome (like E. histolytica)

May have uneven peripheral chromatin

Size is critical: Trophs less than 12 um, cysts less than

10 um –

Entamoeba coli (non-pathogen)

Trophozoite

average size 25um (15 -30um)

large ± eccentric karyosome

coarse, uneven/dark solid chromatin ring

cytoplasm: purple with vacuoles

Cyst

mature: 8 nuclei (5+ diagnostic)

chromotoidal bars (if present) - splintered

Endolimax nana (non-pathogen)

Trophozoite

large karyosome

no peripheral chromatin

vacuolated cytoplasm

average size 10um (5 -12 um)

Cyst

oval/spherical, 5 - 10 um

up to 4 large karyosomes

Iodamoeba butschlii (non-pathogen)

Less commonly seen than E. coli & E. nana

Nucleus

single karyosome

no peripheral chromatin

Trophozoite: 12-15 uM, vacuolated cytoplasm

Cysts

large glycogen vacuole

The Urogenital & Digestive Tract Flagellates

Giardia lamblia

Trichomonas vaginalis

Tenax

hominis

Chilomastix mesnili

Retortamonas intestinalis

Enteromonas hominis

Dientamoeba fragilis

Giardiasis

Cause: Giardia lamblia

A flagellate of class Mastigophora

The trophozoite has four pairs of flagella & two nuclei;

giving it a face-like appearance

Grows in the intestinal tract

Cysts are shed in the feces

Transmission and Symptoms

Transmitted via contaminated water & food

Foul-smelling profuse diarrhea

Sometimes chronic

Often misdiagnosed

Diagnosis via microscopic examination, Enterotest capsule

Trichomonas vaginalis (urogenital pathogen)

one of most common STDs

women: itching, discharge, dysuria

men: generally asymptomatic

keep specimens moist for motility

Wet mount: 5-18 um, look for jerky motility

Culture - most sensitive, takes up to 7 days

Trichomoniasis

Cause: Trichomonas vaginalis

Flagellate of the class Mastigophora

No cyst stage

Transmission & Symptoms

Transmitted via sexual contact

Genital itching

Painful urination with a white, mucoid

discharge

Occasional reduction of sperm count or erosion

of the cervix

Chilomastix mesnili (non-pathogen)

World-wide distribution

Found in chimpanzees and monkeys

Trophozoite

pear shaped

10-20 mu by 3-10 mu

elongated cytostome

Cyst - lemon shaped with anterior protrusion

Dientamoeba fragilis (pathogen)

Transmission - no cyst form (oral/fecal route unlikely)

Incidence 9x higher if E. vermicularis infection

Usually asymptomatic but can be carrier

50-80% binucleate, 4-8 karyosomes, no chromatin, 5-12 um

Food vacuoles in cytoplasm

Balantidium coli (pathogen)

only infectious ciliate (covers surface)

largest protozoan

generally asymptomatic or self-limiting diarrhea, vomiting

Trophozoite - oval, vacuoles in cytoplasm

Cyst - 45-75 um; 2 kidney-shaped nuclei

Symptoms: mostly asymptomatic or similar to amebasis

Reservoirs: Human and animals (pigs, himpanzees,…)

Transmission: waterborne, foodborne

Prevention: personal hygiene, water treatment, food safety program

Balantidiasis

Cause: Balantidium coli

Ciliated, in Class Ciliophora

Trophozoites grow in the intestinal tract

Cysts are shed in the feces and may remain

embedded in intestinal walls, causing chronic

infections

Transmission & Symptoms

Contaminated water & food

Ulceration in intestines

Profuse diarrhea

Coccidia

• characterized by thick-walled oocysts excreted in feces

In Humans

• Cryptosporidium

• Isospora

• Cyclospora

• Sarcocystis

• Toxoplasma

Cryptosporidium• 4-5 mm oocysts

• 4 sporozoites

• no sporocysts

Cyclospora• 8-10 mm oocyts

• 2 sporocysts

• 2 sporozoites each

Isospora belli• 30 x 12 mm oocyts

• 2 sporocysts

• 4 sporozoites each

Coccidian protozoa

Located worldwide

Primarily infects small intestine

Transmission

Fecal-oral Person-to-person

Animal-to-person

Waterborne

Foodborne

• self-limiting diarrhea in immunocompetent persons

• watery diarrhea associated with AIDS (life threatening)

Cryptosporidium parvum

Cryptosporidiosis

Cause: Cryptosporidium species

In class Sporozoa

A common protozoan parasite in humans

Transmission and Symptoms

Contaminated water (waterborne disease outbreak)

Mild diarrhea in non-immunosuppressed persons

Severe diarrhea in immunosuppressed persons

Is a minute coccidian parasite with worldwide distribution.

20 species of the parasite have been described from a varietyof vertebrates including mammals, birds, reptiles and fish.

Pathogenesis

oocysts infective when passed

+/- auto-infection if cysts rupture in gut

Clinical infection - immunocompetent: rapid but self-

limiting diarrhea and cramps

AIDS patient

life-threatening diarrhea (3-17 L/day)

electrolyte imbalance

possible malabsorption due to injury to villi

Modified Ziehl-Nielsen acid-fast stain

oocyst: red, 4-6 um, yeast: green

Cryptosporidiosis

Cryptosporidium Life Cycle

• Infectious form = oocyst

• Sporozoites ‘invade’ intestinal

epithelial cells

• Merogony

• produce merozoites

• Gametogony

• produce micro- and

macrogametes

• Sporogony

• produce sporozoites

• completed on host cell

• thin (autoinfection) or thick

walled oocysts

Molecular Epidemiology

2 major genotypes identified:

• genotype 1 (C. hominis)• only human sources

• non-infective for mice or calves

• anthroponotic transmission

• genotype 2 (C. parvum)• human and bovine sources

• infective for mice and calves

• zoonotic transmission

Epidemiology

Cosmopolitan ( A serious problem in the warmer ports).

The children are more commonly infected than are adults and that non-breast-fed infants have more cryptosporidiosis than breast-fed infants.

Immune deficiency increase risk of disease

Infection is by fecal-oral contamination

A number of animals can serve as reservoirs of infection

Important for travelers (One of the causative travelers diarrhea & in

boarding house).

Transmited to human by infected water & food & any contaminated

sources

Cryptosporidiosis:

Symptoms & pathgenesis

- In immune competent persons

Self-limited diarrhea that usually lasts about 2 weeks

& less commonly is accompanied by Abdominal discomfort, Anorexia, Fever, Nausea, Weight loss

- Immunodeficient patients

typically have severe diarrhea some times 17 liter water loss/days accompanied by these symptoms.

- In patients with AIDS

may couse life-threatening disease and has been found in sputum in lang biopsy material and in the biliary tract and has been associated with malabsorption.

Cryptosporidiosis:

Diagnosis

Finding oocyst in fecal material

Acid fast modified stains

Oocyst:

- 4-5

- Round

- Without Sporocyst

- With 4 Sporozoite are passed in the feces

Concentration procedures to improve sensitivity:

Sucrose solution or Sheather, s technique

Formalin-ether (Formalin ethyl asetate )

Cryptosporidiosis:

Prevention

Prevention: personal hygiene, surface disinfection, water treatment,

food safety program

Especial in AIDS disease:

Boil drinking water for 1 minue

Filter drinking water with devices that remove particles 1m and

larger

Use bottled drinking water, especially water obtained from

underground sources, i.e., springs or welds which are less likely to be

contaminated by Cryptosporidium oocysts

Diease is self-limited infection in immunocompetent patients

In AIDS patients: Oral paromomycin 1gr 3times/days, 2 weeksappears to suitable

Treatment

Cryptosporidiosis:

Clinical infection same as C. parvum

Life cycle similar to C. parvum except not infective for 24 - 48

hours

Disease - AIDS patients

Diarrhea and weight loss for immunodeficient & suppressed

persistent diarrhea that leads to dehydration and electrolyte

imbalance, which can be fatal

most infections are asymptomatic & self-limiting

Isosporiasis

• wide geographical distribution (higher prevalence in warmer

climates)

• monoxenous, probably not zoonosis

• invades intestinal epithelial cells

• often asymptomatic

• symptoms range from mild gastro-intestinal distress to severe

dysentery

• often self-limiting, but can become chronic (wasting,

anorexia)

• symptoms more severe in AIDS patients

Isosporiasis

Isosporiasis: Pathology / clinical symptoms

Most infections are asymptomatic and self-limited

Symptomatic disease in immune competent individualsincludes diarrhea and malabsorption

AIDS patients have severe persistent diarrhea that leadsto dehydration and electrolyte imbalance, which can befatal

Mucosal epithelial cells in which I. belli develop rupturewhen the organsims are released creating the symptomsdescribed above

Wet preps

Modified acid-fast stain

Permanent smears: best if preserved in

SAF

10% formalin

Mature oocyst: Oval, 20-30 um with 2 sporocysts

Isosporiasis: Diagnosis

Cyclospora

• Infection with cyclospora spp. is widely distributed probably cosmopolitan.

• Countries initially identified as having endemic cyclosporiasis: Haiti,

Guatemala, Peru and Nepal

• Infection most common in HIV/AIDS patients.

• Also important cyclosporosis in travelers.

• Associated with imported food items, specially raspberries and green leafy

vegetables such as basil and mesclun lettuce.

Pathology

• Cyclospora infects enterocytes of the small

bowel where various stages, sexual and

asexual stages have been observed. Villous

blunting, mild crypt hyperplasi.

• The main symptom is watery diarrhea, loss

of appetite, weight loss, abdominal bloating

and cramping, nausea, fatigue and low

grade fever.

• Incubation period averages one week and

illness lasts 6 weeks.

• In the immunocompromised patient, severe

diarrhea can last up to 4 months or longe.

• Extra-intestinal infection appears to be

more common in AIDS patients

• symptoms similar to

Cryptosporidium and Isospora

• watery diarrhea/frequent

stools

• 1-2 week duration typical

• relapses over 1-2 months

Clinical Features

Epidemiology

• Food-borne pathogen

• Not sure if water could also have a role in transmission

• Infected humans are the only known sources of oocysts

• Not other reservoir host identified

• No methods available to grow them in the lab

•Marked seasonality of cyclospora: temp, humidity, may facilitate sporulation

• associated with food-borne outbreaks

• oocysts detected on market vegetables in Peru

• presumed source: contaminated water or human waste as fertilizer

Cyclospora:

Diagnosis and treatment

• Detection of oocysts in stool sample by microscopy

• Recovery of oocysts in intestinal fluid or small bowel biopsy

specimens

•Demonstration of oocyst sporulation

• PCR amplification of Cyclospora DNA

• Can be successfully treated with trimethoprim (TMP)-

sulfamethoxasole: TMP 160 mg/ SMX 800 mg bid × 7-10d

Cyclospora:

Sarcocystis

rare human infection

heteroxenous parasite

predator-prey life cycle

humans support both stages

taxonomic confusion

generally named after host species

Sarcocystis bovihominis

Sarcocystis suihominis

ingest undercooked meat

transient mild to severe diarrhea

excrete sporulated sporocysts

13x10 mm

4 sporozoites

Blastocystis hominis (Possible Pathogen)

one of the most common parasites found in the human

intestinal tract (resides in the colon and cecum).

a nonpathogenic protozoan parasite may be associated with

clinical illnesses such as diarrhea, abdominal pain, abdominal

ballooning, anorexia, vomiting, and urticaria

Controversial: Some labs evaluate when

symptoms with no other enteric pathogens

5-15 um, cytoplasm - dark green, nuclei - dark purple/black

B. hominis reproduces asexually, most likely by binary fission.

B. hominis does not have a cell wall and therefore there is great

variation in its size and shape, ranging from 5 to 40 μm.

Multiple forms of B. hominis have been described in culture including

amoeboid, vacuolar, granular.

The amoeboid form is more likely associated with disease.

Acquisition of B. hominis is thought to occur as a result of frequent

animal–human, human–human and human–animal transmission.

Blastocystis hominis (Possible Pathogen)

INTESTINAL AND LUMINAL PROTOZOA

Documents

Transcript of INTESTINAL AND LUMINAL PROTOZOA