zoo 4103 lec 3.ppt

Ameba: Formally Phylum SarcodinaR & J Ch 7

• Protozoa with pseudopodia (or if not, distinct locomotive protoplasmic flow present).

• Mitochondria when present never in the form of a kinetoplasts.

• Without apical complex.

• Without axostyles.

Ameboid Movement

• Ameboid locomotion is used by certain protists including parasitic amoeba.

(gel-like)

(more fluid)

Complex changes in cell fine structure, chemistry, and behavior.

Mechanisms of Ameboid Movement

Mechanisms of Ameboid Movement

Ameba Diversity

• Most amoebas are harmless single cell protozoans living in mud, water, and soil feeding on other protozoans and bacteria.

• Some species are parasitic and endocommensals and are quite common inhabitants of animals.

Endocommensal and Parasitic Ameba Diversity

• Domestic animals

• Birds are free

• Reptiles one species that is pathogenic in snakes Entamoeba invadens

• Frogs and salamanders

• Leeches, termites, and cockroaches

• Hydra

• Humans

Some Ameba are Pathogenic

• Amebiasis- The pathological condition of having an amoebic infection.

• -iasis- “indicates a pathological condition”

Entamoeba histolytica

Entamoeba histolytica

• One of the most important and pathogenic parasites of humans.

Entamoeba histolytica

• One of the most important and pathogenic parasites of humans.

– Although dogs, cats and primates may be infected, these infections are rare and unimportant. This parasite is primarily a human parasite and is transmitted from human to human.

Entamoeba histolytica

• One of the most important and pathogenic parasites of humans.

– Although dogs, cats and primates may be infected, these infections are rare and unimportant. This parasite is primarily a human parasite and is transmitted from human to human.

• First seen in 1878 but not described until 1903.

Entamoeba histolytica

• One of the most important and pathogenic parasites of humans.

– Although dogs, cats and primates may be infected, these infections are rare and unimportant. This parasite is primarily a human parasite and is transmitted from human to human.

• First seen in 1878 but not described until 1903.

• Causative agent of the disease amebiasis (old name is Amebic Dysentery).

Entamoeba histolytica

Entamoeba histolytica

• Active, feeding stage• Growing stage• Amoeboid with blunt

pseudopodia• Non-foamy cytoplasm• Uninucleated; nucleus

with fine peripheral chromatin granules, small central endosomeTrophozoite: 20-30 µm

Entamoeba histolytica Trophozoites

Entamoeba histolytica

• Dormant/resistant stage

• Spherical• 1-4 nuclei, (4 in

mature cysts)• Bluntly rounded

chromatoidal bars

Cyst:10-20 μm

Entamoeba histolytica Cysts

Entamoeba histolytica Cysts

Uninucleate cyst Binucleate cyst

Entamoeba histolytica Cysts

Quadrinucleate or mature cysts

Entamoeba histolytica Life Cycle

• INFECTIVE STAGE: Cyst

Entamoeba histolytica Life Cycle

• INFECTIVE STAGE: Cyst

• Cysts are susceptible to heat (above 40 °C), freezing (below –5 °C), and drying.

Entamoeba histolytica Life Cycle

• INFECTIVE STAGE: Cyst

• Cysts are susceptible to heat (above 40 °C), freezing

(below –5 °C), and drying.

• Cysts remain viable in moist environment for 1 month.

Entamoeba histolytica Life Cycle

Entamoeba histolytica Life Cycle

• CYST: ingested with fecal contaminated food or water.

Entamoeba histolytica Life Cycle

• CYST: ingested with fecal contaminated food or water.

• Excystation occurs in the small intestine in an alkaline environment.

Entamoeba histolytica Life Cycle

• CYST: ingested with fecal contaminated food or water.

• Excystation occurs in the small intestine in an alkaline environment.

• Metacystic amebas emerge, divide and move down into the large intestine.

Entamoeba histolytica Life Cycle

• Trophozoites colonize the large intestine and invade the mucosa.

Entamoeba histolytica Life Cycle

• Trophozoites colonize the large intestine and invade the mucosa.

• They live within the crypts and mucosa of the large intestinal lining.

Entamoeba histolytica Life Cycle

• Trophozoites colonize the large intestine and invade the mucosa.

• They live within the crypts and mucosa of the large intestinal lining.

• Trophozoites may live and multiply indefinitely within the crypts of the LI mucosa feeding on starches and mucous secretions.

Entamoeba histolytica Life Cycle

• Cysts form in response to unfavorable (deteriorating) environmental conditions, as they move down the LI.

Entamoeba histolytica Life Cycle

• Cysts form in response to unfavorable (deteriorating) environmental conditions, as they move down the LI.

• They are released in formed feces.

Entamoeba histolytica

• E. histolytica has surface enzymes that can digest epithelial cells and therefore hydrolyze host tissues and cause pathology.

Entamoeba histolytica

• E. histolytica has surface enzymes that can digest epithelial cells and therefore hydrolyze host tissues and cause pathology.

• Usually the hosts’ repair of the epithelial cells can keep pace with the damage.

Entamoeba histolytica

• E. histolytica has surface enzymes that can digest epithelial cells and therefore hydrolyze host tissues and cause pathology.

• Usually the hosts’ repair of the epithelial cells can keep pace with the damage.

• However, when the host is stressed, has too much HCl, or a high bacterial flora, the digestion will be ahead of repair.

Entamoeba histolytica Pathology

1. A Primary Ulcer Can Occur.

Entamoeba histolytica Pathology

1. A Primary Ulcer Can Occur.

Flask Shaped Ulcers

Entamoeba histolytica Pathology

1. A Primary Ulcer Can Occur.

A primary ulcer can cause rupturing of the bowel and can cause Peritonitis.

Shows movement of trophozoites from large intestine to liver via hepatic portal vein.

Liver Abscesses

Entamoeba histolytica Pathology

2. Extra-Intestinal Lesions and Abscess Occurs

Entamoeba histolytica Pathology

2. Extra-Intestinal Lesions and Abscess Occurs

A. Hepatic Amebiasis

Entamoeba histolytica Pathology

2. Extra-Intestinal Lesions and Abscess Occurs

A. Hepatic Amebiasis

B. Pulmonary Amebiasis

Entamoeba histolytica Pathology

2. Extra-Intestinal Lesions and Abscess Occurs

A. Hepatic Amebiasis

B. Pulmonary Amebiasis

C. Cerebral Amebiasis

Entamoeba histolytica Pathology

• Frequently, intestinal lesions will heal themselves.

Entamoeba histolytica Pathology

• Frequently, intestinal lesions will heal themselves.

• Two exceptions- External ulcers that did not come from the intestine.

Ocular amebiasis

Genital amebiasis

Amoebic Amebiasis of the Skin

Symptoms

• 10% of people in the world infected with ameba, but only 3% ever have some sort of clinical signs.

Symptoms

• 10% of people in the world infected with ameba, but only 3% ever have some sort of clinical signs.

• Abdominal discomfort.

Symptoms

• 10% of people in the world infected with ameba, but only 3% ever have some sort of clinical signs.

• Abdominal discomfort.

• Intense pain localized on the right side.

Symptoms

• 10% of people in the world infected with ameba, but only 3% ever have some sort of clinical signs.

• Abdominal discomfort.

• Intense pain localized on the right side.

• Dysentery.

So How Bad is This?

• In theory, ingestion of 1 cyst could kill you.

• In practice, probably it will never happen.

Prognosis

• 90% of time recovery.

- How much damage.

- Body will repair itself but this repaired

connective tissue in bowel will not

function.

Diagnosis

• Fecal smear/Nested PCR and monoclonal antibody methods.

• Biopsy.

• Serological/Immunological tests (ELISA).

Seriousness of Diagnosis

• Could expose someone to unnecessary treatment.

• Will not be treating the real problem.

• There is an expense.

• Time factor.

Treatment

• Current drug of choice Metronidazole (Flagyl).

• Side effects: Insomnia, headaches, vomiting, intense vasodilation, mutations on bacteria, and carcinogenic in mice.

Epidemiology

• How an infectious organism spreads through a population.

Entamoeba histolytica

DISTRIBUTION - Parasite has worldwide distribution but is most common in the tropical and subtropical areas of the world.

Entamoeba histolytica

DISTRIBUTION - Parasite has worldwide distribution but is most common in the tropical and subtropical areas of the world.

 - it is estimated that up to 500 million people may be affected.

 - may cause up to 100,000 deaths each year.

Entamoeba histolytica

DISTRIBUTION - Parasite has worldwide distribution but is most common in the tropical and subtropical areas of the world.

 - it is estimated that up to 500 million people may be affected.

 - may cause up to 100,000 deaths each year.

PREVALENCE: < 1% in Canada and Alaska

0.9% in U.S.

40% in the tropics

Entamoeba histolytica

• A number of outbreaks have resulted from a breakdown in sanitation or behavioral practices of people.

Entamoeba histolytica

• A number of outbreaks have resulted from a breakdown in sanitation or behavioral practices of people.

• Outbreak in 1933 World's Fair in Chicago caused by defective plumbing (cross connections between water lines and sewer lines) caused over 1,000 cases of amebiasis resulting in 58 deaths.

Entamoeba histolytica

• A number of outbreaks have resulted from a breakdown in sanitation or behavioral practices of people.

• Outbreak in 1933 World's Fair in Chicago caused by defective plumbing (cross connections between water lines and sewer lines) caused over 1,000 cases of amebiasis resulting in 58 deaths.

• Outbreak in the late 1970’s in New York City among gay men.