Protozoan Phyla Notes

Phylum Sarcomastagophora

Causative agent: Giardia lamblia
Most common waterborne illness in the United States.
Contracted from non-purified water sources (e.g., streams).
Backpackers should use iodine purification tablets or boil water.
Two-thirds of individuals exposed develop symptoms.
Infection requires as few as 10 cysts due to low infectious dose.
Reservoirs: beaver, raccoon, muskrat, dogs, and cats (typically asymptomatic).
Hosts: Organisms that show symptoms.
Incubation period: 6-20 days.
Symptoms: Range from mild indigestion to severe diarrhea lasting for days.
Duration: Usually lasts 1-4 weeks and is often self-limiting.
Prevention: Boiling water for at least 1 minute (5 minutes recommended), using bleach, iodine, or water purification tablets.
Treatment: Metronidazole (Flagyl), which is also an antifungal agent and treats Clostridium difficile infection.
Trophozoite form looks like an alien head, guitar pick, or pear cut in half lengthwise.
Has multiple flagella.
Two nuclei present.
Attaches to the intestinal lining using sucker-like structures.
Giardia stool has a very distinctive odor.

Causative agent: Various Leishmania species (e.g., Leishmania domini).
Insect vector: Female sand fly (not sand flea).
Only female sandflies collect a blood meal since they require protein to produce eggs.
Reservoirs: Rodents, possums, anteaters, sloths, and dogs.
Incubation period: 2 weeks to several months.
Three forms: cutaneous, mucocutaneous, and visceral.

A papule (blister-like) appears at the site of the bite (about 1 inch in diameter).
Self-limiting, heals, and goes away.
Leaves cratered scar tissue.

Occurs in 80% of individuals with cutaneous leishmaniasis.
Organism spreads to mucous membranes (oral and nasal passages).
Forms open wounds or lesions that do not heal well.
Wounds can become infected with secondary organisms, especially bacteria, leading to potentially fatal infections.

Can be asymptomatic or self-limiting, or frank visceral leishmaniasis.
Frank visceral leishmaniasis occurs 2-4 months after the bite.
Symptoms: Fever (intermittent), anorexia, malaise, weight loss, and diarrhea.
If untreated, can lead to anemia, enlargement of the spleen, and enlargement of the liver.
Without treatment, death typically occurs 2-3 years after the onset of symptoms.
The organism looks like a green bean cut in half lengthwise, with flagella on either end.
Not common in the United States due to the absence of sandflies but is found in the Middle East and parts of Africa.

Causative agent: Trichomonas vaginalis
Sexually transmitted infection (STI).
No known animal reservoirs; only found in humans.
Third most common cause of vaginal symptoms in women (after bacterial vaginosis and candidiasis).
2.5 to 3 million new cases diagnosed annually in the United States.
Requires large amounts of water to survive; easily destroyed if cells dry out.
Can survive on moist objects (towels, bathing suits, bathtubs, toilet seats).
Most often spread through sexual contact.
Infected children raise concerns about sexual abuse, leading to investigations by child and family services.
Prevention: Condoms.
Treatment: Metronidazole.

Men:
- Mostly asymptomatic.
- If symptoms occur: Painful or burning urination, painful testes, and a tender prostate gland.
Women:
- Itching of the vulva and inner thighs.
- Vaginal itching and burning.
- Burning or painful urination.
- Key symptom: Frothy, yellowish-green vaginal discharge with a rotten egg odor (malodorous).
Characterized by an undulating membrane that spins the cell for attachment to host cells.
Also has flagella for movement.

Causative agent: Trypanosoma cruzii.
Found primarily in Central and South America.
Transmitted by the kissing bug.
Kissing bugs regurgitate food on the host, causing irritation and potential entry point for the parasite when the host scratches.
Causes systemic disease, damaging the heart and intestine.

Causative agent: Trypanosoma brucei.
Found only on the African continent.
Transmitted by female tsetse flies.
Symptoms arise a week after the bite, with a tender bump near the bite site, which may open, and regionally enlarged lymph nodes.
The organism is injected directly into the host's bloodstream via fly saliva.
Eventually affects the central nervous system.
Progressive symptoms: gradual loss of interest in enjoyable activities, increased episodes of sleeping, poor coordination, confusion, slurred speech.
Terminal stage: coma, leading to death.
Trypanosomes visible in the bloodstream (snake-like organisms among red blood cells).

Trypanosoma brucei rhodesiense
- Found in East and Southern Africa (grassy, cattle-raising areas).
- Most dangerous form, progresses rapidly.
- Death within six months.
Trypanosoma brucei gambiense
- Found in Central and West Africa (forested regions).
- Slower progression.
- Death usually due to secondary infection.
- 95% of infections are chronic with recurring symptoms.

Prevention: Insect repellent, protective clothing, clearing brush to eliminate breeding grounds.
Treatment: Toxic drugs with severe side effects; slim chance of successful treatment once the central nervous system is affected.