Parasitology - Lecture 4

How many hosts are in a parasite?

Depends on the parasite?

What does Monoxenous mean?

One host

What does Heteroxenous mean?

2 or more hosts e.g vector or food borne

What are the types of hosts?

Definitive Host and Intermediate Host

What is a definitive host?

Where parasites multiply or reach sexual maturity

What is an intermediate host?

Carries infective stages, e.g., cysts, larvae

What types of parasites are we learning?

Protozoa (Unicellular) and Helminths (worms)

What are protists?

Kingdom of single-celled eukaryotes (including algae)

What are organelles that Protozoa have that most eukaryotes have?

No cell wall or chloroplast

What is the trophozoite stage of a protozoa?

Motile, feeding, and growing form

What is the cyst or oocyst stage of a protozoa?

Nonmotile and infectious and dormant, the stage humans pick up

How does Gastrointestinal Protozoa get into the human body?

Humans ingest infective form which is a cyst

What is a Gastrointestinal Protozoa cyst?

Dormant, resistant stage passed in feces after infection

What happens after Gastrointestinal Protozoa cyst is ingested?

Trophozoite burst out cyst walls

Does the trophozoite or cyst form cause disease?

Trophozoite form causes

How do Humans acquire Gastrointestinal Protozoa?

Fecal-oral transmission

What is the life cycle of Entamoeba histolytica?

Ingest cyst → Trophozoite released in large intestine → Primary ulcer forms → Trophozoite destroys epithelial cells, which progresses into dysentery

What is the inflammatory response to Entamoeba histolytica?

Copious bloody diarrhea with mucus

What is passed in the feces during an Entamoeba histolytica infection?

Infectious cysts passed in feces

If the trophozoite form is in diarrhea during an Entamoeba histolytica infection, is it infectious?

Trophozoite in diarrhea is not infectious

When do symptoms of Entamoeba histolytica, amoebic dysentery, appear?

1-4 weeks after cyst is ingested food

How long do symptoms do Entamoeba histolytica, amoebic dysentery last?

3-8 days

What is the diagnosis of symptoms of Entamoeba histolytica, amoebic dysentery?

Cyst or Trophozoite in feces

What is the difference between Entamoeba coli and Entamoeba histolytica?

Entamoeba coli is a commensal and has an off-center karysome

Entamoeba histolytica is a pathogen and has a central karysome

What is a karyosome?

Condensed DNA

How many nuclei are in the cyst form of Entamoeba histolytica?

Up to 4 nuclei

How many nuclei are in the cyst form of Entamoeba coli?

Up to 8 nuclei

Is this Entamoeba coli or Entamoeba histolytica?

Entamoeba coli

Is this Entamoeba coli or Entamoeba histolytica?

Entamoeba histolytica

What is the life cycle and disease of Giardia lamblia (beaver fever)?

Ingest cyst from contaminated food, water, and trophozoites released in small intestine

What does Giardia lamblia look like in the Trophozoite stage?

Tear-shaped with flagella

What does the Trophozoite form of Giardia lamblia do?

Attach to small intestine mucosa with sucking disk

What is passed in the feces during an Giardiasis infection?

Infectious cysts

If the trophozoite form is in diarrhea during an Giardiasis infection, is it infectious?

Not infectious

When do symptoms show up after a Giardia lamblia cyst is ingested?

7 days after the cyst was ingested

What are symptoms of Giardia lamblia infection?

Malabsorption in small intestine, mucus-filled, oatmeal-like diarrhea (not invasive, no blood) but its chronic

What causes mucus-filled, oatmeal-like diarrhea in Giardiasis?

Undigested food in colon = cramps + flatulence

What happens when you can’t absorb digested nutrients during a Giardiasis infection?

Weight loss, malnutrition

What is the diagnosis of Giardiasis?

Trophozoite in diarrhea

Is the Trophozoite or Cyst infectious in diarrhea in a Giardiasis infection?

Cyst in old or solid feces are infectious; Trophozoite in feces is not infectious

What is the life cycle of Trichomonas vaginalis?

Flagellated trophozoite only (no cyst stage)

Where does Trichomonas vaginalis infect?

Genital tracts of male and female (humans only)

Where do you get Trichomonas vaginalis?

Direct contact with trophozoite during sexual intercourse

What is the pathology of Trichomonas vaginalis in women?

Symptomatic Vaginitis: fishy, frothy, purulent discharge (yellow-green colored); abdominal pain

What is the pathology of Trichomonas vaginalis in men?

Usually asymptomatic carrier but can have prostatitis, urethritis

What is the diagnosis of Trichomonas vaginalis?

Vaginal smear/wet mount: Swimming throphozoites, Multiple anterior flagella

What protozoa is this?

Giardia lamblia

What protozoa is this?

Trichomonas vaginalis

Do you have to treat both partners or just the person infected with Trichomonas vaginalis?

Treat both partners

What is a vector-borne disease?

Transmitted to bloodstream → Disseminate to body

What are the Heteroxenous life cycles of vector-borne disease?

Infective stage to insect: picked up during blood feeling

Infective stage to human: transmitted during blood feeding

What is the biology of Trypanosoma cruzi?

Flagellated trophozoites live in gut of kissing bug

How is Trypanosoma cruzi transmitted?

Bug bites → Defecate on skin → rubbed into wound or mucus membranes → enters cells (lose flagella) → Replicate and release more trypomastigotes

What are the reservoirs of Trypanosoma cruzi?

Humans, rodents, armadillos, dogs, racoons

What happens after a bite by kissing bug?

Acute phase of American trypanosomiasis/Chagas disease

What is the sign during the acute phase of American trypanosomiasis/Chagas disease?

Chagoma or Promana’s sign—inflammation at site of bite

What are the symptoms of the acute phase of American trypanosomiasis/Chagas disease?

Flu like symptoms

Can you treat the acute or chronic phase of American trypanosomiasis/Chagas disease?

Acute phase, blood stages

What happens in the chronic phase of American trypanosomiasis/Chagas disease?

Blood form infects heart (flabby heart), colon (mega colon), esophagus

How to diagnose American trypanosomiasis/Chagas disease?

Trypomastigotes (trophozoites) in blood smear: slender with undulating flagella for length of body and large dark-staining kinetoplast