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

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


• 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.




• First seen in 1878 but not described until 1903.

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


• 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


• Dormant/resistant stage

• Spherical• 1-4 nuclei, (4 in

mature cysts)• Bluntly rounded

chromatoidal bars

Cyst:10-20 μm

Entamoeba histolytica Cysts


Uninucleate cyst Binucleate cyst


Quadrinucleate or mature cysts

Entamoeba histolytica Life Cycle

• INFECTIVE STAGE: Cyst



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



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

(below –5 °C), and drying.

• Cysts remain viable in moist environment for 1 month.



• CYST: ingested with fecal contaminated food or water.



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



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

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


• Trophozoites colonize the large intestine and invade the mucosa.



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



• 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.


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


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

• They are released in formed feces.


• 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.



• 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.



Flask Shaped Ulcers



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


2. Extra-Intestinal Lesions and Abscess Occurs



A. Hepatic Amebiasis




B. Pulmonary Amebiasis




B. Pulmonary Amebiasis

C. Cerebral Amebiasis


• Frequently, intestinal lesions will heal themselves.


• 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


• Abdominal discomfort.

Symptoms



• Intense pain localized on the right side.

Symptoms



• 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.


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.



- 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


• 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 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.

zoo 4103 lec 3.ppt

Documents