Causal Agent:• Several protozoan species in the genus

Entamoeba infect humans, but not all of them are associated with disease.

• Entamoeba histolytica is well recognized as a pathogenic ameba, associated with intestinal and extra-intestinal infections. 

• The other species are important because they may be confused with

E. histolytica in diagnostic investigations.

Introduction Entamoeba histolytica

1. The only pathogenic amoeba among all of the intestinal amoebae.2. Infecting perhaps 10% of the

world's population.3. Lead to invasive amoebiasis.

Entamoeba histolytica

•Worldwide, with higher incidence of amoebiasis in developing countries.

• risk groups include male homosexuals, travelers and recent immigrants, and institutional

populations.

morphology

Life cycle• Infection by Entamoeba histolytica

occurs by ingestion of mature cysts in fecally contaminated food, water, or hands.

•   Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine. 

• The trophozoites multiply by binary fission and produce cysts. 

• Cysts and trophozoites are passed in feces Cysts are found in formed stool, whereas trophozoites are found in diarrheal stool.

E.dispar has similar live cycle but non invasive ,not pathogenic.

Via polluted water; infected food handler, flies contaminating food, soil cultivation, direct contact

Viability : -Moist ,cool condtion Up to 12days -In water 9-30 day

transmission. • the cysts can survive days to weeks

in the external environment (protection by cyst walls) and are responsible for transmission. 

• Trophozoites in the stool are rapidly destroyed outside ,and if ingested not survive in the gastric juice. 

• In many cases, the trophozoites remain confined to the intestinal lumen of individuals who are known as (non-invasive infection) cyst passer.

1- the primary ulcer invasion of mucosa via crypts repair may occur.2- extension in mucosa muscularis mucosa relatively resistant. 3-formation of sinus accumulation of amoebae superficial to muscularis mucosa with lateral extension of lytic necrosis; abscesses may coalesce under intact mucosa , mucosa may slough with widespread ulceration 4-deep extension muscularis mucosa eventuallypierced (direct or via blood)deep necrosis of sub-mucosa even muscle and sub-serosa

1

2

3

4

Complications and squeals

-Pretonitis haemorrhag

-Surronging inflammatory reaction

-A mass under oedemotous mucosa

Amoeboma clinically simulates neoplasm

-Extraintestinal lesion

-Perforation hemorrhage (rare)

-Secondary infection

Amoeboma

Obestraction

intusssception

-Invasion of blood vessels.

-Direct extension outside bowel

-Ulcer with peritonitis - hemorrhage - surrounding inflammatory

reaction and fibroplastic proliferation a mass formed under edematous mucosa amoeboma (simulate

carcinoma)

Extra intestinal extension

Extra intestinal extension

Liver involvement

- Secondary to

- Concomitant with

-Independent of

.

A B

• the pathogenic E. histolytica is not morphologically differs from the nonpathogenic E. dispar! 

• Each trophozoite has a single nucleus, which has a centrally karyosome and uniformly distributed peripheral chromatin. 

• The cytoplasm has a granular or "ground-glass" appearance.  

• Entamoeba histolytica / E. dispar trophozoites measure usually 15 to 20 µm (range 10 to 60 µm), tending to be more elongated in diarrheal stool. 

C D

f e

erythro-phagocytosis,

Trophozoites of Entamoeba histolytica with ingested erythrocytes .The ingested erythrocytes appear as dark inclusions.

•Erythro-phagocytosis is the only morphologic

characteristic that can be used to differentiate E. histolytica from the non-pathogenic

E. dispar

•The nuclei of Entamoeba histolytica have characteristically centrally located karyosomes, and fine, uniformly distributed peripheral chromatin. 

• The cysts contain chromatoid bodies , with typically blunted ends.  •Entamoeba histolytica cysts

usually measure 12 to 15 µm.

MatureEntamoeba histolytica cysts usually measure 12 to 15 µm. cysts have 4 nuclei. 

h

I

Entamoeba coli

Trophozoites of Entamoeba coli

A

B

C

•Entamoeba coli -Trophozoites each have one nucleus

with a large, eccentric karyosome and coarse, irregular peripheral chromatin. 

-The cytoplasm is coarse , vacuolated (dirty cytoplasm). - Cytoplasm contains ingested

bacteria , yeasts or other materials.  - The trophozoites of E. coli measure

usually 20 to 25 µm, but it can reach up to 50 µm.

•Mature cysts typically have

8 nuclei, and measure about

20-25 µm (range 10 to 35 µm).  •   Chromatoid bodies are seen

less frequently than in E.histolytica.  they are splinter like with pointed ends.

• N.B. chromatoid bodies of E.histolytica have rounded ends.

DF

E

Entamoeba coli cyst

Clinical Features:A wide spectrum, from asymptomatic infection ("luminal amebiasis"), to invasive intestinal amebiasis (dysentery, colitis, appendicitis, toxic megacolon, amebomas), to invasive extra-intestinal amebiasis

(liver abscess, peritonitis, pleuropulmonary abscess, cutaneous and genital amebic lesions).

pinpoint lesion on mucous membrane

flask-shaped (Ulcers)

Amoebic abscess in liver

Pathogenesis: Clinical classification Intestinal • Asymptomatic infection (carrier)  85-95 % of cases.• Sympomatic cases 5-15%

a. Intestinal amoebiasis  - a. dysentery (blood and mucus in stool)   - b. non-dysenteric colitis  - c. amoeboma   

b.Extra-intestinal amoebiasis 

a. Hepatic (1) acute non suppurative hepatitis    (2) liver abscess  b. Pulmonary  c. Brain, Skin, Other extra- intestinal amoebiasis.

Hepatic amoebiasis:

sing & symptoms•Local discomfort.•Malaise, fluctuant temperature

• Toxemia.• Pain in right shoulder.

Diagnosis : intestinal Direct

_ Microscopic identification of cysts

and trophozoites in the stool _ trophozoites can also be identified in aspirates or biopsy samples obtained during colonoscopy or surgery.

Indirect by immunodiagnosis (elisa)

Diagnosis: of Amoebic liver abscess

•X-ray or ct scan show raised diaphragm•Blood picture –leucoytosis.•Serological test (elisa).•Examination of aspirate if

indicated as treatment.

•Treatment:-For asymptomatic infections, (furamide) is the drugs of choice.

-For symptomatic intestinal disease,

or extra intestinal, infections (e.g. hepatic abscess), the drugs

of choice are metronidazole or tinidazole, immediately followed by treatment with diloxanide furoate. 

Prevention•human feces should not be

used as fertilizer• food and drinks must be

protected from flies.

(mechanical transmission)•personal hygiene.  wash hands after defecation

and before meals. (autoinfection)

in summary pinpoint lesion on mucous membrane •flask-shaped Ulcers•Amoebic liver abscess• anchovy sauce sputum (lung) • brain , spleen , genito-urinary tract• amoeboma simulate carcinoma.- Cyst carrier is a healthy persons

(trophozoite only in intestinal lumen -Lumenal form).

- Pre-employments Stool analysis was done for food handler.

FREE-LIVING PROTOZOA Ameba Diseases•Naegleria fowleri PAM•Acanthamoeba spp. GAE, skin or lung lesions, amebic keratitis.

Acanthameoba• Have only 2 stage cyst And trophozoite.•Trophozoite and cyst are infective form.

•portal of entry unknown, possibly respiratory tract, eyes, skin.

• presumed hematogenous dissemination to the CNS.

Acanthamoeba Encephalitis• infection associated with

debilitation or immunosuppression. opportunistic parasitic inf.

• chronic GAE (granulomatous amebic encephalitis). the organisms cause a granulomatous encephalitis that leads to death.

•occurred in wearers of contact lenses.

Amebic Keratitis• Predisposing factors ocular trauma, contact lens (contaminated cleaning solutions).• Symptoms ocular pain, corneal

lesions (refractory to usual treatments).

• Diagnosis demonstration of amebas in corneal

scrapings.• Treatment difficult, limited success corneal grafts often required.

Naegleria fowleri

• found in fresh water.• ameba with loblose Pseudopodia.• motile bi-flagellated form.• PAM first recognized by Fowler (1965).

Primary Amebic Meningoencephalitis

(PAM)

• Symptoms usually within a few days after swimming in warm still waters.

• Infection believed to be introduced through nasal

cavity and olfactory bulbs.• Symptoms include headache,

disorientation, coma.

Clinical picture A-Asymptomatic infection majority , about 80% B-Symptomatic infection: 1* typical picture most of symptomatic cases: incubation period 1-2 weeks followed by diarrhea for bout 6 weeks. 2* atypical picture - malabsorption in children - fatty diahrrea - Sever diarrhoea.

Laboratory diagnosis- Stool examination daily for three

days .- Examination of duodenal aspirate,

or by string (enterotest)

No cyst form

Trichomonas vaginalis

•Transmission :sexual intercourse or contact with contaminated objects.

•Pathology: • Female: vaginitis ,profuse thin

yellowish discharge with bad smell.

• Male : invasion of urethra ,prostate and seminal vesicles ,causing urethritis but mostly asymptomatic.

•Diagnosis :

identification of parasites by microscopy of discharge.

(Examination of vaginal or uretheral discharge for T.vaginalis).

•N.B. No cyst stage Imp

Cryptosporidium Cryptosporidium parvumparvum

Cryptosporidiosis zoonosis,cosmopolitan,most human and animals infected by Cryptosporidium .

Life cycle• Infective stage : oocyst

with4sporozoites passed in feces.• Upon ingestion sporozoites are

released.•Sporozoite penetrate intestinal

epithelial cells and undergo two cycle :

1-schizogony 2-gametogony.•Sporulated oocyst ,4-5M (with 4

sporozoites) are passed in feces.

duodenal biopsy sample from a patient with AIDS and cryptosporidiosis

Pathology & clinical picture:

• Immunocopetent persons asymptomatic or mild enterocolitis ,last about 2 weeks.

• Immunodeficient persons sever diarrhoea with malabsorption.

Diagnosis & morphology:

• duodinal biopsy :gametes or schizont (4-8 merozoites) in epithelial cells.

• Stools :oocyst 4-5 m with 4 sporozoites (without sporocyst).

•Treatment - Self limited in immunocomptant

persons ,no effective drugs in cases of AIDS.

- Management of fluid and electrolytes loss.

•Prevention and control: -person-to person or animal to

person transmission controlled by sanitation.

-Identify common sources e.g. contaminated water