Deck #2: Parasitic Infection

Define Zoonosis.

seen in vertebrate, but can transmit to humans

Define Zoonanthroponosis.

humans are an essential link to the organism’s life cycle

Define Anthroponosis.

Spreads b/w:

• human to human

• human to animal

List the common ways Parasitic infection are transmitted.

1. Ingestion (e.g., poorly cooked pork)

2. Transcutaneous (it poops and we push it in)

3. Bites (mosquitos + flies)

4. Waterborne (major cause in CL)

5. Blood

6. Eggs

What Ig are produced in general parasitic infections?

IgG & IgM

What Ig are produced in protozoa parasitic infections?

IgA

What Ig are produced in helminths parasitic infections?

IgE

List 4 ways how we show host immunity.

1. Agglutination of parasites by IgM

2. Opsonization

3. Antibody dependent cell mediated cytotoxicity

4. Neutralizing toxins & enzymes via antibodies

Why is the body not as effective in eradicating parasitic disease compared to bacterial?

since these are eukaryotic cells, any drugs we do use, CAN’T differentiate b/w us and parasites

Compare the 2 life cycles of Acanthamoeba.

1) Vegetative trophozoite

• large

• eat bacteria, algae & yeasts

• replicate via binary fission

2) Dormant cyst

• small

• form “double-walled”cyst under harsh conditions

• don’t replicate

List the virulence factors of Acanthamoeba.

1. Mannose BP

2. Laminin BP

3. Toxins

4. Proteases

5. Phospholipases

6. Cyst formation (Resistance to chemotherapy)

List how Acanthamoeba is transmitted.

1. Inhalation

2. Inoculation

3. CL wear

4. Corneal trauma + contaminated water

What is the major source of infection for Acanthoamoeba?

Contact lens

List the 4 different infections caused by Acanthoamoeba.

1. Granulomatous amebic encephalitis (GAE)

   • fatal

   • involves brain + spinal cord

2. Amebic keratitis (AK)

   • healthy pt that wear CL

3. Cutaneous

   • occurs with or without CNS disease

4. Disseminated infection

   • can attack any organ

For Toxplasma gondii mention:

• type of parasite

• host (primary + intermediate)

• tranmission

-Obligate intracellular

1er Host: Felidae (cats)

Intermediate: Humans

Transmission

• Foodborne illness (improper pork, contaminated water)

• Zoonotic

• Contact with feces of infected animals (e.g., cat litter box)

• Transplacental (e.g., preggy woman)

Life cycle of Toxoplasma gondii.

1. Organism invades cat intestinal cells

2. Gametocytes formation → oocyst formation (asexual)

3. Oocysts excreted in feces and become infective ~1-5 days later

4. Cats eat the poop (normal)

Abnormal

1. Intermediate hosts (humans) eat the cysts → infection

2. Acute phase: tachyzoites eplicate fast → bradyzoites replicate slow to form cysts

3. Chronic phase: cyst formation in SM, heart, brains & eyes

For Plasmodium mention:

• type of parasite

• host (primary + intermediate)

• tranmission

Apicomplexan

1er host: Anophele mosquito (Africa, S. America, Asia)

Intermediate host: Primates

What is Mosquito phase of the Plasmodium life cycle?

1. Ingest merozoites from host → gametocytes → oocysts which form 100s of sporozoites

2. Oocyst ruptures releasing sporozoites into hemocoel of mosquito salivary glands → injected into veins of primate host

What is Human/primate phase of the Plasmodium life cycle?

1) Liver phase

1. Injected sporozoite cause infection in liver

2. Parasite matures in ~15 days

3. Lots of Merozoites produced in schizonts

2) Erythrocytic phase

1. Merozoites released from schizonts & invade RBC

2. Can be taken up by mosquito during feeding to start cycle over

What is #1 cause of parasitic induced death worldwide?

Malaria

How can Malaria manifest?

• Cyclical non-specific flu-like symptoms

  • Cold stage

  • Hot stage

  • Sweating stage

• Neurologic deficits

• Muscle coordination & speech problems, delirium, deafness

• Ocular manifestations: retinal changes, nystagmus, conjugate gaze palsies

• Kidney disease

• Splenomegaly

Fill in the blanks:

Trypanosoma cruzi is found in _____

Trypanosoma brucei gambiense is found in ______

Trypanosoma brucei rhodesiense is found in ______

Trypanosoma cruzi = USA

Trypanosoma brucei gambiense = Central + West Africa

Trypanosoma brucei rhodesiense = East Africa

For Trypanosoma mention:

• type of parasite

• host (primary + intermediate)

• tranmission

Flagellate organism

Host:

• Kissing bug – T. cruzi

• Tsetse fly – T. brucei (don’t wanna test bruce)

Transmission

• Kissing bug (reduviid/triatomine) bites or fecal exposure

• Congenital

• Blood transfusions, infected organ donation

• Lab accidents

• Ingestion of contaminated food &/or drinks

What is the life cycle of T.cruzi?

1. Kissing bug bites host

2. Trypomastigotes in bug’s feces is excreted on host skin

3. Parasite enters body via wound/intact mucous membranes

4. Convert into intracellular amastigotes → binary fusion → Trypomastigotes → enter circ

What is Chagas disease or America Trypanosomiasis?

Acute phase

• Chagoma - localized swelling at site of parasite entry

  • Romana’s sign: eyelid swelling on side of face of bite or fecal inoculation

• mild enlarge of liver, spleen or swollen glands

Chronic phase

• Cardiac & intestinal complications

How is African sleeping sickness or African trypanosomiasis different from the American one?

• Tsetse fly

• Doesn’t enter “into” host cells, it stays as the “trypanomastigote stage”

• Can cross BBB

For Toxocara mention:

• type of parasite

• host (primary + intermediate)

• tranmission

Ascarid nematode (roundworm) found worldwide

Definitive host: dogs

Aberrant host: humans (esp children, sandboxes, grass)

Transmission

• Ingestion of embryonated eggs

• Transplacental infection

What is the life cycle of Toxocara?

→ Ingestion of embryonated eggs by host

Definitive host (dogs):

• Eggs hatch to release larvae → penetrate small intestine → enter circulation → mature to adults (2-3 months) → mate → non-embryonated eggs excreted via defecation into environment → Embryonation occurs ~1 week after

• prevalent during hot temps

Aberrant host (humans)

• Same process BUT larvae never mature to adult forms + can’t replicate

• Remain in host for months to yrs

What 2 infections occur due to Toxocara?

Visceral larval migrans (VLM)

• affects major organs (fever, liver, spleen & lung)

• <5yrs children

Ocular larval migrans (OLM)

• eye & optic nerve

• 5-10 children

• Unilateral vision loss + strab

For Onchocerca volvulus mention:

• type of parasite

• host

• transmission

→ infection is from roundworm

Transmission: Vector bite of black fly

Definitive host: Humans

How is the Onchocerca transmitted?

1. Bite from blackfly transmits larvae to human host

2. Larvae invades cutaneous tissues to form nodules of adult nematodes

3. Travel in host via lymphatics (live for SO LONG)

What infection does Onchocerca volvulus cause?

River blindness

• round worm in eye

• found in Africa (fast moving waters)

• inflammation due to 1000s of dead/decaying roundworm

Cutaneous lesions

• leopard/lizard skin

For Loa loa mention:

• type of parasite

• host

• transmission

African eye worm

Transmission = Deer fly

Host: Humans

🌍 Africa, India

What is the life cycle of Loa Loa in the deer fly host vs human host?

Deerfly host

1. Deerfly ingests larvae from infected human host

2. Mature for 7-12 days → infect human host → move to mouthparts of fly

3. Fly bites another host & transmits disease

Human host

1. Larvae enter host & mature for ~5 months

2. Mature adults move to CT to reproduce (1000/day) → lymphatics → lungs

   • Live in host up to 17 yrs

What are the characteristics of Demodex?

• Mite that live in hair

  • part of normal microbiota → cause infestation when numerous

  • obligate human ecto-parasite

• Transmission = close contact

What is the Demodex life cycle?

Sexual replication cycle

• Female lays eggs in hair follicle + male leave hair at night

• Larvae hatch ~3-4 days

• Mature, take on adult form in ~7 days

Total life cycle ~14 days

List the infections Demodex can cause.

1. Blepharitis (in eyelash)

2. Rosacea

3. Alopecia

4. Non-specific dermatitis

What are the characteristics of Pediculosis?

• Phthirus pubis (pubic lice)

• Host = humans

• Transmission = sex, fomites (bedding)

What is the Pediculosis life cycle?

1. Females produce ~25 ova/day

2. Nits incubate for ~1 week

3. Become nymphs – mature into adults in over 2 weeks

Live ~2 weeks

How are Pediculosis different from Demodex?

• live longer

• make more eggs