Unit 3.1 Eukaryotic Pathogens

What are the four eukaryotic pathogens?

1. Fungi

2. Algae

3. Protozoa (single celled organisms)

4. Helminths (worms)

What are fungi’s defining characteristics?

• Cell walls contain chitin

• Cell membrane contains ergosterol

What are the two basic forms fungi can come in?

1. Yeasts: exists as single cells

2. Molds: exists as long threadlike structures called hyphae

How do yeasts produce asexually?

Yeasts produce asexually through budding

What is a tangled mass of hyphae called? (molds)

A tangled mass of hyphae is called mycelium

How do molds reproduce?

Molds reproduce through:

• Fragmentation: a piece of hypha breaks off, growing into a new fungus

• Spore production: hyphae produces spores that can grow into a new fungus

What are fungal infections called?

Fungal infections are called: Mycoses

What is Systemic Mycoses and an example of this?

Systemic Mycoses: deep within body

• example: Cryptococcosis

What is Subcutaneous mycoses?

Subcutaneous Mycoses: beneath the skin

What is Cutaneous Mycoses and an example of this

Cutaneous Mycoses: caused by fungi called dermatophytes

• example: Tinea pedis; athelete’s foot

What is Superficial Mycoses?

Superficial Mycoses: on hair and skin

What is Opportunistic Mycoses and an example of this?

Opportunistic Mycoses: caused by Candida in the mouth

• example: Candida albicans - Thrush

What does Ergot toxin cause?

Egort toxin causes ergotism which are seizures, hallucination, and restricted blood flow

What does Aflatoxin cause?

Aflatoxin is associated with the development of liver cancer

What is algae’s key characteristic?

Algae does not cause infections but it causes intoxications

What is the toxin name of Diatoms?

Diatoms toxin name: Domoic acid

What disease do Diatoms cause?

Diatom disease: Amnesiac shellfish poisoning

What is Dinoflagellates toxin name?

Dinoflagellates toxin name: Saxitoxins

What disease do Dinoflagellates cause?

Dinoflagellates disease: Paralytic Shellfish poisoning

What is protozoa’s main characteristics?

• No cell wall

• May form cysts

What is an example of a one host life cycle?

One host life cycle: Entamoeba histolytica

What is the definitive host?

The definitive host is the organism that hosts the sexual reproductive stage of a parasite

What is the intermediate host?

The intermediate host is the organism that hosts the asexual reproductive stage of a parasite

What is an example of the intermediate host?

Intermediate host examples: Plasmodium vivax, toxoplasma gondii

What is Amoebic dysentry?

Amoebic dystentry is a disease caused by entamoeba histolytica

What does dysentery mean?

Dysentery: nausea, vomiting, fever

Describe Malaria’s / plasmodium’s life cycle

1. Infected mosquito bites human, infecting them with plasmodium

2. Plasmodium infects human liver cells and reproduce asexually

3. Infected human is bitten by another mosquito, picking up Plasmodium

What is Toxoplasmosis’ definitive host?

Cat

How is Toxoplasmosis spread?

Cysts are shed in cat feces and picked up by intermediate hosts such as humans

How do Parasitic/Pathogenic Helminths reproduce?

• Monoecious: male and female reproductive systems in one animal

• Dioecious: male and female reproductive systems on separate animals

Describe the life cycle of a helminth

Intermediate host for larva and definitive host for adult helminth

Platyhelminthes vs. Nematodes

Platyhelminthes = flat worms

Nematodes = round worms

What are flukes?

Flukes are non segmented worms with an oral sucker

What disease does Fluke Schistosoma cause, its definitive host, and intermediate host?

• Causes Schistosomiasis

• Definitive host: human

• Intermediate host: snail

What is the life cycle of Schistosoma?

1. Eggs are passed out from infected human’s feces or urine

2. Eggs hatch and infect snails

3. Snails infect skin of human bathers

4. Snails enter blood vessels and mature into adults

Describe Tapeworms’ body structure

• Head/scolex: contains suckers and hooks to attach to definitive host

• Segments:

  • contains male and female reproductive organs

  • segment near the end contains a sac of fertilized eggs

Describe Tapeworm’s intermediate host life cycle

Intermediate host: consumes eggs which hatch into larvae and burrow into tissues to form cysticerci (causing cysticercosis)

Describe Tapeworm’s definitive host life cycle

Definitive host: consumes cysticerci and develops into adult tapeworms

What is Taeniasis?

Taeniasis: abdominal pain, weight loss, fatigue

Describe Amoebic Dystentry’s disease process

1. Cysts enter the body and become amoebas in the large intestine

2. Amoebas multiply in the large intestine, forming new cysts

3. Severe untreated infections can lead to death

How does Taenia solium occur?

Taenia solium occurs when humans ingests undercooked larvae infested meat (cysticerci)

Describe the life cycle of Taenia Solium when humans are definitive hosts

Pork Tapeworm - Human Definitive Host

1. Adult tapeworm grows in human intestine

2. Eggs from adult tapeworm are passed out in feces

3. Pigs eat grass with feces

4. Eggs hatch, forming cysticerci in the pigs

5. Humans eat the undercooked meat, infecting the human

Describe the life cycle of Taenia Solium when humans are intermediate hosts

Pork Tapeworm - Human Intermediate Host

1. Adult tapeworm grows in human intestine

2. Eggs from adult tapeworm are passed out in feces

3. Another human consumes the eggs

4. Eggs hatch and burrow into organs and brain of the human, forming cysts

Describe the life cycle of Enterobius vermicularis (Roundworm)

Enterobius vermicularis life cycle

1. Adult female lays eggs in the anus

2. Eggs are passed out in feces or fingernails (due to itching)

3. Human consumes eggs

4. Larvae hatch in small intestine

5. Adult male and female mate

6. Adult female migrates to anus, repeating the cycle

What are the symptoms of Enterobius vermicularis?

Symptoms: Itchy anus & abdominal discomfort