Ch. 12.2 - Protozoan Diseases

Phaeophyta

brown algae (kelp), lives in medium-shallow waters with pneumatocysts for floating to surface (for sunlight)

cell wall: cellulose + algin (thickening agent)

multicellular

Rhodophyta

red algae, lives in deep waters

cell wall: cellulose; in red moss: agar + carrageenan

most multicellular

Cholorophyta

green algae, live in shallow waters

cell wall: cellulose

unicellular or multicellular

Euglena

also protozoan

eyespot (photodetector) & flagellum (motility)

no cell wall— pellicle has cellulose

has chloroplast, but can also ingest food when dark (unable to photosynthesize)

Bacillariophyta

diatoms

cell wall: pectin & silica (glass)

unicellular

store oil as energy source

Domoic Acid Intoxication — buildup in clams/mussels/other animals that eat diatoms → consumed by humans

• causes: diarrhea, memory loss (brain damage)

Dinoflagellata

no cell wall— cellulose in cell membrane

unicellular

genera

• Alexandrium

• Karenia brevis

• Phytophthora infestans

Algal bloom

caused by extra nutrients entering body of water

algae covers surface & kills organisms underneath

• blocks sunlight from photosynthesizers

• depletes O2 as algae dies & decomposes

• only obligate anaerobes can survive

Protozoa

unicellular

no cell wall— pellicle cell membrane

found in water & damp soil

form cysts

Paramecium

ciliates (cilia for motility)

structures:

• cytosome (food enters) & anal pore (waste exits)

• food vacuoles

• macronucleus + micronucleus

• contractile vacuole: expels water, prevents lysis

Balantidium coli

ciliate

source: monkeys & pigs

causes: severe dysentery

identified by kidney bean nucleus

Entamoeba histolytica

causes amebic dysentery

pseudopods: “false feet” (motility)

transmission: ingestion → can enter liver & lungs

symptoms: bloody mucoid stool, constipation, fever, abdominal pain

identifies by RBCs inside ameoba

Ancanthamoeba

causes keratinitis

transmission: enters minute pores/scratches

present in tap water

can lead to blindness — cornea infection, lens inflammation

Trichomonas vaginalis

Parabasalid— no cyst stage & no mitochondria

causes UTI & genital tract infection

has undulating (wavy) membrane & flagella

transmission: sexual & from moist towels/ baths/toilets/etc

symptoms:

• male: usually none; burning sensation with urination, testicle pain

• female: itching, burning, unusual discharge, burning with urination

Giardia intestinalis

diplomonads

structures:

• no mitochondria, 8 flagella, 2 nuclei

• sucker disk: adheres to epithelial cells of intestinal tract

found in contaminated water & nearby moist soil

transmission: ingestion

cysts unaffected by chlorine, removed by filters

symptoms: weight loss, fatigue, loss of water & electrolytes (diarrhea)

Apicomplexa

apical complex: located at tip of cell, dissolve & penetrate tissue

nonmotile

intracellular parasite

Toxoplasma gondii

causes Toxoplasmosis

found in cat (definitive host) intestinal tract & feces

transmission: ingestion of eggs from air / undercooked beef (intermediate host) with cyst

opportunistic to fetuses

• early pregnancy → miscarriage

• late pregnancy → developmental disability, deafness, blindness, seizures, microcephaly (underdeveloped brain & head)

Plasmodium

causes malaria

Life cycle:

1. sporozoites: infective stage, present in Anopheles mosquito (definitive host) salivary glands

2. transmission: enters bloodstream of human (intermediate host) through bite

3. enter liver & undergo schizomony (asexual reproduction) → enter circulation again

4. merozoite (ring stage): present in each RBC & asexually reproduce until RBC bursts & releases merozoites

5. some merozoites → gametes → ingested by next mosquito to bite → form zygote in digestive tract → spirozoites

symptoms: vomiting, headache, fever, & chills every 2-3 days when RBCs rupture & release merozoites; enlarged spleen, black urine

pathogen changes antigens frequently → difficult to find cure

male mosquito sterilization by radiation

Cryptosporidium

causes severe diarrheal infection, ~10 days

Life cycle:

1. found in dogs, rodents, cows (definitive) intestinal tract & feces

2. transmission: ingestion of contaminated water

3. sporozoites attach to epithelial lining of intestines in humans (intermediate)

opportunistically fatal in AIDS PTs

Euglenozoa

also algae

hemoflagellates: cause blood infection

Trypanosoma brucei gambiense

Euglenozoa

causes African Sleeping Sickness (Trypanosomiasis)

carried by Tse Tse fly

enters bloodstream → liver, spleen, CNS (encephalitis) via bite

symptoms appear within a week & can last years, fatal if left untreated

symptoms: chronic bouts of fever, headache, wasting away, changed personality (brain damage), difficulty concentrating, lose ability to eat + walk, falling asleep at random times, coma

Trypanosoma cruzi

Euglenozoa

causes American Sleeping Sickness (Chagas’ disease)

carried by kissing bug

feces enters bloodstream via bite

cardiovascular effects (heart failure), spread to brain → can affect all body system nerves

Leishmaniasis tropica

carried by sandflies

causes cutaneous Leishmaniasis

• lesion/sore at site of bite (usually face)

• ulcerates, takes a long time to heal

• permanently scars

Leishmaniasis braziliensis

carried by sandflies

causes mucocutaneous Leishmaniasis

• destruction of tissue in nose, mouth, upper throat → disfigurement

Leishmaniasis donovani

carried by sandflies

causes visceral Leishmaniasis

• fatal if left untreated — kidney failure within a few years

• resembles chills, fever, & enlarged liver/spleen of malaria

Naegleria fowleri

causes ameobic meningoencephalitis

found in tap water

transmission: enters through nasal cavity (not ingested)

causes hemorrhage & necrosis of brain

Alexandrium

produce sacitoxin

causes Paralytic Shellfish Poisoning → respiratory paralysis

Karenia brevis

produces neurotoxin, paralyzes gills of fish → suffocation

Phytophthora infestans

Irish potato blight