1. unicellular eurkaryotes

2. possess organelles tha often function similarly to organs and systems of multicellular organisms

3. parasitic forms with holozoic nutrition

4. basic forms of locomotion

(flagella, cilia, pseudopodia, gliding)

Binary fission, the most common form of reproduction, is asexual

Multiple  asexual divisions occur in some form

Both sexual and asexual reproduction occur in the Apicomplexa

1. longitudinal binary fission

2. transverse binary fission

3. budding

4. multiple fission

5. endodyogeny

6. endopolyogeny

Equal division of organism into 2 across longitudinal axis

Ex/ Lumen dwelling flagellates

"Merogony" or "Schizogony"

Multiple karyokinesis followed by multiple cytokinesis

Ex/ malaria

2 daughter cells arising from internal budding of parent

Many parental membranes and organelles utilized

1. Conjugation - in ciliates, pairing and temporary plasma membrane fusion for genetic exhange

2. Syngamy - fusion of gametes  Ex/ malaria

3. Anisogamy - dissimilar gametes

4. Isogamy - similar gametes

Trophozoites: the stage of parasitic protozoa that actively feed and multiply

- in some protozoa, other terms are used for these stages

Cysts: stages with protective membrane or thickened wall

- Protozoan cysts that must survive outside the host usually have more resistant walls than cyst that form in tissues

1. Cell membrane

2. Cytoplasm

3. Nucleus

1. Skin:  Leishmania

2. Eye:  Acanthamoeba

3. Mouth:  Amoebae and flagellates (usually non-pathogenic)

4. Gut:  Gardia, Entamoeba, Cryptosporidium, Isospora, Balantidium

5. G.U. tract:  Trichomonas

6. Bloodstream:  Plasmodium, Trypanosoma

7. Spleen:  Leishmania

8. Liver:  Leishmania

9. Muscle:  Trypanosoma cruzi

10. CNS:  Trypanosoma, Naegleria, Toxoplasma, Plasmodium

- Have a flexible plasma membrane

- Flagella present in some species

- Use pseudopods for locomotion & feeding

- Come in 2 forms

--Trophozoites (feeding stage)

--Cyst (protective resistant stage

- Multinucleated

- Forms when temp decrease or dryness increases or change in pH

- Survives days to weeks

E. histolytica

Pathogenesis

- Organism has the ability to move beyond the colonic epithelium and invade submucosa

- Ulcers with potential for perforated colon

- Once below the epithelium, can be carried in the bloodstream to liver and produce amebic absexesses

- May also reach brain or other tissues

Giardia lamblia

General Info

1. Worldwide in distribution and very common

2. Most common cause of epidemic waterborne diarrheal disease in US "Bever Fever"

3. Rodents, deer, cattle, cats, dogs may act as Zoonosis for humans

ONCE SMELLED, NEVER FORGOTTEN

- has ER and 2 separate nuclei "monkey face"

Trichomonas vaginalis

(Trichomoniasis)

A sexually transmitted disease where leukocytes accumulate at the site of infection

(discharge is a symptom)

- found in semen or urine of males (carriers)

- Diagnosis by microscopic identification of protozoan

(found in the vaginal discharge)

- Treatment: metronidazole

Balantidium coli

(Balantidiasis)

-It is the only infectious ciliated protozoa

- worldwide prevalence of 1%

- Largest infectious protozoa

- Transmitted by fecal-oral route

Infection occurs when cysts (non-ciliated) are consumed

- More common among people who are frequently exposed to pigs

Balantidium coli

Symptoms

- Severe dysentery and diarrhea that can last for weeks to months

- Severe fluid loss

- Ulcers in intestines

- Many individuals are asymptomatic or have much milder cases

Balantidium coli

Treatment

- Administration of tetracycline, iodoquinol, or metronidazole in humans

- treat infected animals with metronidazole or albendazole

Balantidium coli

Control of Transmission

Cysts are persistent in the environment and are not inactivated by chlorine disinfection

- prevention of contamination is more useful than treatment

- avoid fecal contamination of food and water

- employ good personal hygiene and sanitation practices

Coccidia-- Phylum Apicomplexa

organisms of interest

Cryptosporidium

Isospora

Cyclospora

Toxoplasma

Plasmodium

Babesia

- Asymptomatic carriers

- Watery, foul smelling diarrhea

- Signs suggest malabsorptive diarrhea

- Abdominal pain, weakness, weight loss

- Diagnosis by ID of oocysts in feces using concentration techniques

Treatment:  Trimethoprim-sulfamethoxazole

Isospora belli

Morphology & Epidemiology

- Infective oocysts containing 2 sporocysts are ingested

- Both asexual and sexual development in new epithelial cells

- Large "football-shaped" oocysts with sporoblast pass in feces

- Immature oocysts mature in 4 days to become infective

- Most serious in immunocompromised patients

Cyclosporosis

"Tourist Diarrhea"

- prolonged (4-9 wks) diarrhea

- (4-10) watery stools/day

- non-inflammatory (no WBD in stools)

- anorexia, fatigue, upper GI symptoms, weight loss

- Oocysts sporulate in host

- Each oocyst contains 4 sporozoites that attach to surface of small intestinal cells

- Acid red stain of oocysts is diagnostic

Cryptosporidium parvum

Diagnosis & Treatment

- Examination of feces

- Morphologic

Stained smears, concentration techniques

- Immunologic

Fluorescent antibody, enzyme immunoassay test

Treatment: Nothing good

Cryptosporidium parvum

 Epidemiology

- Oocysts extremely resistant to disinfectants, environmental conditions

- humans and animals can become infected

Risk Factors: exposure to untreated or inadequately treated water, poor sanitation or contaminated food

Microsporidia

(Now considered to be a fungus)

- Unicellular spore

- uni or dinucleate

- spores with extrusion apparatus

(polar cap, polar tube)

- No mitochondria

Babesiosis

"Babesia"

- Infection of red blood cells cause by the one-celled parasite Babesia

- Transmitted by the same deer tick that transmits Lyme disease

- Babesia live inside RBCs and eventually destroys them, producing fever, headache, and muscle aces

- Anemia may result from the breakdown of RBCs

- In people whose spleen has been removed, the risk of severe disease & death is high

- Babesiosis resembles malria in these people

- A person with a functioning spleen usually has a mild illness that disappears w/o treatment

- Microscope examination of blood is required for diagnosis

- Treatment consist of taking quinine and clindamycin

- Take a good history in order to distinguish between babesiosis and malaria

1. Humans enter the cycle when bitten by infected tick

2. During a blood meal, a Babesia-infected tick introduces sporozoits into the human host

3. Sporozoites enter RBCs and undergo asexual replication (budding)

4. Multiplication of the blood stage parasites is responsible for the clinical manifestations of the disease

5. Humans are the dead-end host and there is little subsequent transmission that occurs from ticks feeding on infected persons

6. Human-human transmission can occur through blood transfusions

Toxoplasmosis

Toxoplasma gondii

- Toxoplamosis is an infection that comes from a single-celled parasite found in animal feces or undercooked meat

- Pregnant women and those with a poor immune system (AIDS) should be aware that serious complication or death may occur

- Oocysts are shed in a cat's stool and can survive in kitty litter and for up to 18 months in the soil

- Freezing and throughly cooking meat may destroy Toxoplasma

- A woman who was infected before the pregnancy will not pass the parasite on to the fetus; while pregnant, passes to fetus

Toxoplasma gondii

 Tachyzoites and Bradyzoites

Sporozoites emerge from oocysts, leave gut and begin the phase of rapid division in cells (Tachyzoites)

Eventually multiplication slows, organism accumuate in cysts (Bradyzoites)

Toxoplasma gondii

Clinical Signs

If Immunosuppressed:

- Encephalitis

- Reactivation of cysts with dissemination of tachyzoites

- In transplant patients, may come from the transplanted organ

What is Malaria?

(Plasmodium)

- a disease caused by a parasite that infects the RBCs

- 4 types of Malaria caused by:

Plasmodium falciparum (most serious type)

Plasmodium vivax

Plasmodium ovale

Plasmodium malaria

How is Malaria Spread?

Mosquitos

4 stages:

- Sporozoites

- Merozoites

- Trophozoites

- Gametocytes

- Located in the salivary glands of mosquitos

- Enters blood of human after puncture of skin has occurred

- Migrate to liver and become Merozoites

- Previously were Sporozites

- Have entered liver

- Remain in lever for 9-16 days

Move to blood and become Trophozoites

Malaria (Plasmodium)

Clinical signs and pathogenesis

- Flu like symptoms after incubation period

Headaches, vomiting, muscle pains

- Anemia

- Paroxysms of chills, sweats, fever (periodic)

Spikes in fever correlate with RBC destruction

P. falciparum: every 24 hours

P. vivax: every 48 hours

P. malariae: every 3 days

can be infected with all 3 causing multiple spikes in fever

Thick and thin blood smears

Dipstick technique

Acute Symptoms

Classical Cyclic paroxysm:

Cold Stage: chills and shaking

Hot Stage: warm, headache, vomiting

Sweating Stage: weakness

Infected person feels well for a period of time, then cycle repeats itself

If P. falciparum: Quinine +

Doxycycline

or Clindamycin

or Mefloquine

or Atovaquone/Proguanil

or Artemisinin

or Artesunate

If P. ovale or vivax:

Primaquine

Cutaneous leishmaniasis - L. tropica

Mucocutaneous leishmaniasis- L. braziliensis

Visceral leishmaniasis- L. donovani

Leishmania

Clinical signs and pathogenesis:

Cutaneous leishmaniasis

-Also known as Oriental sore, Aleppo evil, Baghdad or Delhi boil, chiclero ulcer, bay sore

- Organisms stay in skin (lower temp than viscera)

- Lesion begins as papule at bite site

- Eventually forms ulcer, often w/ raised edges

- Generally heals after a few months but may leave scars

Leishmania

Clinical signs and pathogenesis:

Mucocutaneous leishmaniasis

- Much less common form than regular cutaneous leishmaniais

- 1-3% patients develop metastatic spread to mucosal areas (Nasa, pharyngeal, buccal mucosa)

- Ulceration, erosion of soft tissue and cartilage

Leishmania

Clinical signs and pathogenesis:

Visceral leishmaniasis

- Most serious form of leishmaniasis

- Many infections asymptomatic

- Typically, initial low grade fever followed by progressive anemia, hepatosplenomegaly and wasting

- If not treated, death in 2-3 years

Strong relationship between AIDS and visceral leishmaniasis

Leishmania

Diagnosis and Treatment:

Cutaneous leishmaniasis

Diagnosis:

- Clinical presentation

- Impression smears from lesion biopsies

Treatment:

- Clean, cover lesion

- Not done unless concern

Leishmania

Diagnosis:

Visceral leishmaniasis

Microscopy of blood and bone marrow samples

PCR antigen test

- Has flagella

- vector borne

- Intra and extracellular forms

 American trypanosomiasis

(Chagas disease) "Trypanosoma cruzi"

African trypanosomiasis

(Sleeping sickness) "Trypanosoma brucei"

Trypanosoma cruzi

American Trypanosomiasis

Asymptomatic

Acute

- Mostly seen in children

Inflammation at bite site (Romanas sign)

Fever, lymphadenopathy

Liver, spleen enlargement

Transmission by blood transfusion has become very important in some areas

Trypanosoma brucei

African Trypanosmiasis

T.b. gambiense: West, Central Africa

T.b. rhodensiense: East, Southern Africa

Vector is the Tsetse fly

African Trypanosomiasis

Clinical signs and Pathogenesis

Acute stage of infection (1st phase)

- fever, headache, joint pain, itching

- Acute infection followed by asyptomatic period

(with gambiense can be years)

Neurologic phase- "sleeping sickness"

- Parasite enters CNS causing confusion, sensory disturbances, seizures, coma and eventual death