Parasitology Pt 1 Flashcards
Characteristics of Protozoa
Unicellular eukaryotes
- Protists
- Bigger than bacteria (eat bacteria)
Usually motile
1. Cilia
2. Flagella
3. Pseudopodia
4. Polar filaments
Most often reproduce by asexual fission
Love wet environments
Essential decomposers
- NOT photosynthetic
Protozoa Habitats
- Marine
- Freshwater
- Terrestrial
Role of Protozoa in Food Chain
- Eat bacteria
- Food for larger species
- Maintain ecological balance in soil
- Decrease sewage solids
Protozoa Cell Structure
Membrane-bound nucleus & organelles
Specialized structures for movement
NO cell wall
- Food, water, O2 diffuse through membrane
- Pinocytosis & phagocytosis
Protozoa Reproduction
Complex life cycles
- Require more than 1 host/habitat
Polymorphic
(distinct morphological forms at different stages)
- Trophozoite = vegetative/feeding form
- Cyst = resting/infectious form (withstands)
Asexual &/or sexual reproduction
1. Binary fission
- DNA replication + division into 2 cells
- Longitudinal division = flagellates
- Transverse division = ciliates
- Multiple fissions (schizogony)
- Multiple DNA divisions
- Cell contains may single-celled infectious organisms
- Parasite released at regular intervals
Protozoa Phyla
- Phylum Sarcomastigophora
(Subphylums Mastigophora & Sarcodina) - Phylum Ciliophora
- Phylum Apicomplexa
- Phylum Microspora
Subphylum Mastigophora
Flagella
- Giardia lamblia
- Leishmania species
- Trichomonas vaginalis
- Trypanosoma brucei rhodesiense
- Trypanosoma brucei gambiense
- Trypanosoma cruzi
Subphylum Sarcodina
Pseudopodia
Entamoeba histolytica (disease in humans)
Phylum Ciliphora
Cilia
Balantidium coli (ulcers in large intestine)
Phylum Apicomplexa (Sporozoa)
Flagella
- Plasmodium species (malaria)
- Toxoplasma gondii (toxoplasmosis)
- Cryptosporidium parvum (cryptosporidiosis)
Phylum Microspora
Polar filament
Microsporidium (diarrhea, immunocompromised)
Leishmaniasis
Zoonotic protozoa
Carried by: rodents, dogs, & foxes
Transmitted to humans by bite of sandfly
Promastigote
- Flagellated motile form
- Invades phagocytic cells & transforms into amastigote
Amastigote
- Nonmotile form
- Multiplies in phagocytic cells of reticuloendothelial system
(lymph node, spleen, liver, bone marrow)
Cutaneous Leishmaniasis
L. tropica & L. mexicana
Skin ulcer develops at site of bite
Nodular lesions diffuse across body (inactive CMI response)
Untreated infections can last for years
(NOT normally fatal)
Mucocutaneous Leishmaniasis
L. braziliensis
Initial dermal ulceration heals
Ulcers appear in mucous membranes of nose & mouth
May erode nasal septum, soft palate, & lips if left untreated
(NOT normally fatal)
Visceral Leishmaniasis
L. donovani
Common in young/malnourished children
Fever, anorexia, weight loss, & abdominal swelling (hepatomegaly & splenomegaly)
Often fatal
Leishmania:
Life Cycle
- Sandfly takes blood meal
- Injects promastigote into human skin - Macrophages phagocytose promastigotes
- Promastigotes transform into amastigotes
- Amastigotes multiply in cells of various tissues
- Sandfly takes blood meal
- Ingests macrophages infected with amastigotes - Amastigotes transform into promastigotes in midgut
- Promastigotes divide & migrate to proboscis
African Sleeping Sickness
Trypanosoma brucei
Tsetse fly bite spreads tryptomastigote via blood stream to CNS & lymph nodes
Initial painful skin ulcer heals within 2 weeks
Fever, headache, dizziness, lymph node swelling
CNS symptoms (daytime drowsiness, slurred speech, problems walking, coma, death)
West African Sleeping Sickness
Trypanosoma brucei gambiense
Slowly progressing symptoms
East African Sleeping Sickness
Trypanosoma brucei rhodesiense
More severe
Death occurs within weeks
Trypanosoma brucei:
Life Cycle
- Tsetse fly takes blood meal
- Injects metacyclic tryptomastigotes - Metacyclic tryptomastigotes transform into bloodstream tryptomastigotes
- Tryptomastigotes multiply by binary fission in bodily fluids
- Blood, lymph, spinal fluid - Tsetse fly takes blood meal
- Ingests tryptomastigotes - Bloodstream tryptomastigotes transform into procyclic tryptomastigotes in midgut
- Multiply by binary fission - Procyclic tryptomastigotes leave midguit & transform into epimastigotes
- Epimastigotes multiply in salivary gland
- Transform into metacyclic tryptomastigotes
Chaga’s Disease
Trypanosoma cruzi
Spread by triatomine bug feces (travels through blood to distant organs)
Tryptomastigotes tunnel into human host & transform into amastigote
Amastigote invades:
- skin
- macrophages
- lymph nodes
Hard/red area develops at entry site
Systemic spread: fever, malaise, & swollen lymph nodes
Infects heart & CNS
Chaga’s disease: Acute Phase
Resolves in ~month
Symptoms:
- Fever
- Malaise
- Swollen lymph nodes
- Meningoencephalitis
- Acute myocarditis
Chaga’s disease: Intermediate Phase
Low levels of parasites in blood
Positive antibody response against T. cruzi
NO symptoms
Chaga’s disease: Chronic Phase
Organs primarily affected:
- Heart
- Colon
- Esophagus
Symptoms:
- Dementia
- Megaesophagus
- Heart damage
- Heart failure
Trypanosoma cruzi:
Life Cycle
- Triatomine bug takes blood meal
- Passes metacyclic tryptomastigotes in feces
- Enter bite wound or mucous membranes - Metacyclic tryptomastigotes penetrate cells at wound site
- Transform into amastigotes - Amastigotes multiply by binary fission
(in cells of infected tissue) - Intracellular amastigotes transform into tryptomastigotes
- Burst out of cells & enter bloodstream
- Infect other cells - Triatomine bug takes blood meal
- Ingests tryptomastigotes - Tryptomastigotes transform into epimastigotes in midgut
- Epimastigotes multiply in midgut
- Epimastigotes transform into metacyclic tryptomastigotes in hindgut
Plasmodium species
Malaria
Periodic episodes of high fever & shaking chills (paroxysms)
Followed by periods of profuse sweating
RBCs burst & release merozoites
Tertian malaria
P. vivax & P.ovale
Every 48 hours
Quartan malaria
P. malaria
Every 72 hours
P. falciparum
Most common & deadly malaria
Irregular episodes
Short liver stage
Plasmodium species:
Life Cycle
- Mosquito takes blood meal
- Injects sporozoites - Sporozoites travel to liver & multiply (schizogony)
- Merozoites released from liver cells & invade RBCs
- Erythrocytic cycle
(immature - mature trophozoite - schizont) - Gametocytes differentiate from some merozoites
- Mosquito takes blood meal
- Ingests gametocytes - Gametocytes multiply (sporogonic cycle)
- Microgametocytes (male)
- Macrogamtocytes (female) - Zygote
- Ookinete
- Oocyst
- Ruptures & releases sporozoites - Sporozoites travel to salivary glands
Toxoplasmosis
Toxoplasma gondii
Transmission via oocysts (cat feces) or bradyzoites (raw/undercooked meals)
Transplacental transmission possible
Problems in immunocompromised individuals (toxoplasma encephalitis)
Toxoplasma gondii:
Life Cycle
- Human ingests oocysts or bradyzoites
- Cat = fecal oocysts (intestinal phase)
- Other animals = tissue cysts (extraintestinal phase) - Transform into tachyzoites
- Tachyzoites localize in neural & muscle tissue
- Develop into cyst bradyzoites
- Tachyzoites can infect fetus via bloodstream (pregnant)
Blood & Tissue Protozoa
- Leishmania
- Trypanosoma brucei
- Trypanosoma cruzi
- Plasmodium species
- Toxoplasma gondii
Intestinal & Luminal Protozoa
- Giardia lamblia
- Cryptosporidium parvum/hominis
- Entamoeba histolytica
Giardiasis
Giardia lamblia (Mastigora)
Tranmitted via ingestion of cyst
(fecally contaminated food/water, streams, day cares, mental hospitals)
Chlorination doesn’t kill cysts
(boiling & filtration works)
Trophozoite adheres to small intestinal wall (sucking disk) & interferes with fat absorption
Non-bloody, foul-smelling diarrhea
Cryptosporidium parvum/hominis
Transmitted via ingestion of oocysts
(fecally contaminated water, agricultural runoff - zoonosis)
Short-term/mild diarrhea
Chronic/watery diarrhea in immunocompromised
Opportunistic infection
Common in US
Entamoeba histolytica
Amoebiasis (amoebic dysentery)
- Diarrhea
(mild asymptomatic disease to severe dysentery)
May invade intestinal mucosa
(causing erosions)
May penetrate portal blood circulation
(forming abscesses in liver & lung; often resulting in death)
Entamoeba histolytica:
Life Cycle
- Human ingests fecal cyst
- Cyst transforms into trophozoites in small intestine
- Trophozoites reproduce by simple division
- May invade lining of large intestine - Cysts passed in feces
- Extra-intestinal amoebiasis
- Trophozoites invade blood vessels of large intestines
- Transported to other organs (brain, liver, lungs)
Trichomaniasis
Trichomonas vaginalis
Sexually transmitted via trophozite
(NO cyst stages)
Most males asymptomatic
Often asymptomatic in women
Heavy infection symptoms:
- Itching
- Burning on urination
- White/frothy/malodorous discharge from genital tract (trophozoites visible)
Treat males to prevent re-infection of female partner
Free-living Meningitis-causing Amoebas
- Naegleria fowleri
- Acanthamoeba
Naegleria fowleri
“Brain-eating” amoeba
Enters body through nose
- Contaminated water gets high up in nasal passages
Travels to brain & spinal cord (destroys tissue)
Primary amebic meningoencephalitis (PAM)
- Brain inflammation (fatal within week)
Symptoms:
- Fever
- Headache
- Stiff neck
- Nausea & vom
Acanthamoeba
Humans acquire from:
- Swimming in contaminated water
- HVAC systems
- Shower heads
- Taps
Acanthamoeba keratinitis
- Local infection of eye (healthy individuals)
- Can lead to permanent visual impairment/blindness
Granulomatous Amebic Encephalitis (GAE)
- Serious infection of brain & spinal cord (immunocompromised individuals)
Disseminated infection
- Widespread infection (immunocompromised individuals)
- Can affect: skin, sinuses, lungs, & other organs
Mechanical vector
Mechanically transporting microbe from 1 place to another
Ex: microbe carried on fly’s leg
Biological vector
Essential part of life cycle
Pathogen multiplies with vector
Ex: growth of Leishmania & Plasmodium inside sandfly & anopheles mosquito (respectively)
Mosquitoes as vectors
Insert feeding tube into host skin
- Ingests blood (can pick up infectious agent & transfer to next host)
Transmit:
1. Malaria
2. Yellow fever
3. Dengue fever
4. West Nile encephalitis
Fleas as vectors
Yersinia pestis
- Causes plague
- Picks up when biting host
- Bacterium multiplies/blocks digestive tract
- Starving fleas repeatedly bite & pass bacteria
Lice as vectors
Suck blood through skin
- Appendages adapted for attachment
Spread by direct contact with person or personal items
Head lice does NOT transmit disease
Body lice transmits bacterial diseases:
1. Trench fever (Bartonella quintana)
2. Epidemic typhus (Rickettsia prowazekki)
3. Relapsing fever (Borrelia recurrentis)
Ticks as vectors
Arachnids
- NO wings or antennae
- 4 pairs legs
- fused thorax & abdomen
Live in low vegetation
Burrow into skin with mouthparts
- Feed continually
Wood tick (Dermacentor anderson)
- Rocky Mountain spotted fever (Rickettsia rickettsii)
Ixodes scapularis
- Lymes disease (Borrelia burgdorferi)
Mites
Live on outer surfaces of plants/animals
Microscopic Demodoex mites
- Hair follicles/oil-producing glands
Do NOT transmit disease
Chiggers (larvae)
- Attach/feed on fluid within skin cells
- Intense itching
Sarcoptes scabei mites
- Transmitted via personal contact
- Cause scabies (itchy skin rash)
