Parasites Flashcards
Organisms from what groups are considered “parasites?”
Protozoa and Animalia
Protozoa- amoeba, flagellates, ciliates and sporozoa pathogens
2 fungi sometimes listed as protozoa
Pneumocystis jirovicii (pneumonia in immunocompromised)
Microsporidia (spores of numerous fungal species associated with numerous different infections in immunocompromised)
Ectoparasites
near the skin surface (most arthropods)
Endoparasites
“inside” the body
Most GI and respiratory mucosal surfaces are still in contact with the external environment
Entamoeba histolytica
Asymptomatic or invasive intestinal amebiasis (bloody diarrhea, colitis, appendicitis) with possible extraintestinal amebiasis (liver abscess)
Free Living Amoeba
Acanthamoeba castellanii can cause keratitis in contact wearers
A. castellanii and Balamuthia mandrillaris cause granulomatous encephalitis
Naegleria fowleri can cause meningoencephalitis, usually via cribriform plate fracture
Dx – culture for amoeba
giardia lamblia
Causes diarrhea with “fatty” stools .
under microscope looks like kites with eyes
swallowed string test
Leishmania donovani, etc.
Vector is the sand fly
Cutaneas, visceral (=kala azar), and mucocutaneous exist.
promastigotes in sandfly and in culture
kinetoplastid amastigotes in macrophages in lesions of human tissues
Trypanosoma cruzi
Chagas disease = American trypanosomiasis
Vector is the kissing=reduviid=triatomine bug feces,
Romana sign– big swollen eye at the beginning of the infection
Kinetoplastid amastigotes in muscle tissue (heart, etc.)
Trypanosoma brucei
Sleeping sickness = African trypanosomiasis
Fulminant East African
chronic West African
Vector is tsetse fly
Parasite initially forms chancre, gets into blood evading host response via VSG glycoprotein gene rearrangements (recurrent fevers) and causes lymphadenopathy; later crosses into CNS (demyelinating panencephalitis) and can lead to coma and death if not treated
Trichomonas vaginalis
Sexually transmitted can be asymptomatic or cause urethritis in males or vaginitis in females
smells “fishy”
Plasmodium spp
Malaria
–> febrile hemolytic illness during merozoite release from RBCs that causes hemoglobinemia and hemoglobinuria (blackwater fever)
sometimes cerebral malaria = cerebral ischemia
Anopheles spp. mosquitoes is final host and humans the intermediate hosts of malaria
Vector (female mosquito) injects sporozoites
Sporozoites infect hepatocytes which reproduce asexually forming schizonts filled with merozoites
Merozoites infect RBCs forming ring forms that grow into trophozoites that can produce gametocytes
Mosquitos ingest male microgametocytes and female macrogametocytes from human blood
Dx – thick and thin blood smears
plasmodium spp. life cycle
mosquito takes up blood meal
pre-erythrocytic (exoerythrocytic) schizogony
Schizonts are filled with asexual haploid merozoites
dormant in hepatocytes (hypnozoites) –> recur years later
Erythrocytic schizogony (24-72 hours): immature trophozole (ring stage)–> mature–> schizont–> rupture–) immature trophozole
can continue from that phase to gametocytes
histology of plasmodium falciparum
1- Malaria has hemozoin (iron- brown pigment)
2- the falciparum gamteocyte is elongated/ banana shaped
treatment of malaria
Quinoline drugs (quinine, etc.) thought to inhibit heme transformation to hemozoin, which is required by the parasites as heme is toxic to the parasite
Different types of plasmodium spp
P. flaciparum- malignant tertian presentation. Crescent (banana) shape
P. vivax- benign tertian
P. malariae- Quartan
Toxoplasma gondii
Toxoplasmosis is usually asymptomatic with infectious cysts in meats or cat feces
worse in immunocompromised
TORCH syndrome with fetomaternal transmission
Definitive host is the cat
Cryptosporidium parvum
Cryptosporidiosis - watery diarrhea and gastroenteritis, especially in immunocompromised
Dx- stool exam w/ AFB stain
Cystoisopora belli
diarrhea, commonly in immunocompromised people
dx: acid-fast oocysts
Babesia spp.
hemolytic anemia; in immunocompromised can lead to DIC and death
Vector is Ixodes scapularis (blacklegged = deer tick)
** No hemozoin pigment
dx- ring forms (esp. tetrad maltese cross)
inflammatory response to helminths
Th2 –> cytokines –> eosinophils -> IgE
Platyhelminthes
blood flukes, lung fluke, sheep liver fluke, fish liver fluke, intestinal fluke
-Cestoda
various tapeworms
Schistosoma spp.= Blood Flukes
get it from the water
–> itchy rash
Chronically can lead to liver (pipe-stem fibrosis and ascites), intestinal (bloody diarrhea), pulmonary, bladder (hematuria) and CNS inflammation and fibrosis from misplaced eggs
S. haematobium involves urinary bladder and can lead to squamous cell carcinoma
dx- eggs in urine for H. haematobium, eggs in stool for others
different schistosoma by egg descriptions
lateral spine– mansoni
terminal spine- haematopium
no spine- japonicum
cercarial dermatitis
Cercaria intended for other species can cause an itchy rash (swimmer’s itch) which is self-limited as human is an incidental dead-end host
normal host is ducks
Paragonimus westermani, etc.
Lung Flukes
Causes paragonimiasis – asymptomatic to acute syndrome with cough, abdominal pain, and low-grade fever
Spread by consumption of undercooked shellfish, crabs and crayfish
Dx – eggs in sputum or lung biopsy;
Fasciola hepatica, etc
= Common/Sheep Liver Fluke
in undercooked sheep/goat liver
RUQ abdominal pain, cholecystitis, pancreatitis
not associated with liver cancer
Clonorchis sinensis
Chinese/Oriental Liver Fluke
undercooked fish–> travel to liver and feed on bile
–> RUQ abdominal pain
chronically can lea to biliary tract cholangiocarcinoma
Taenia spp.
Taenia solium from pork, Taenia saginata from beef
from ingestion of animal flesh with cysticercosis
cyticerci in undercooked flesh
mild GI symptoms
Ingestion of eggs in human fecal material from T. solium can cause cysticercosis
dx- imaging for cysts in neurocysticercosis
humans are final host
Scolex have little hooks to grab onto your intestine
Proglottid = eggs
Diphyllobothrium latum
Fish/Broad tapeworm
Asymptomatic to symptoms of intestinal obstruction or gallbladder disease
B12 deficiency
From raw/undercooked freshwater fish
humans are final host
Hymenolepis nana
= dwarf tapeworm
mild intestinal symptoms
world from ingestion of eggs in human feces or ingestion of infected microscopic crustaceans (copepods), beetles or mealworms
Echinococcus spp.
causes cysts within numerous organs (liver, lungs, CNS)
Cystic (hydatid) disease occurs from eggs obtained from dogs (definitive host) or larval stages from sheep
feels like hepatitis
Onchocerca volvulus
roundworm
Causes onchocerciasis (river blindness) – skin onchocercoma nodules corneal scarring
immature larvae introduced by blackfly
Loa loa
African Eye Worm
Causes loiasis - itching, localized (Calabar) skin swelling, joint pain, renal failure, ocular problems from migrating microfilariae and can occlude lymphatics
dx- midday blood smear examination
Dirofilaria immitis, etc.
granulomas in skin, lungs (asymptomatic, cough, pleural effusions,
human is incidental host bitten by infected mosquito; DOG is the main host
Wuchereria bancrofti/ Brugia malayi/B. timori
Cause lymphatic filariasis
can cause elephantiasis
dx- nocturnal blood smears
Gongylonema pulchrum
presenting as a moving “worm” in the oral cavity mucosae,
Infection is caused by ingestion larvae from intermediate hosts (cockroaches or dung beetles)
Trichinella spiralis
causes GI symptoms plus muscle pain
from larvae in undercooked meat
Trichuris trichiura
= Whipworm Infection
Soil transmitted helminth that causes trichuriasis – asymptomatic to frequent, painful defecation of watery stool with mucus and blood which can lead to rectal prolapse
from ingestion of human feces
barrel-shaped eggs with two polar caps
Dracunculus medinensis
Guinea Worm Disease
GI symptoms with diarrhea, boil with severe burning pain where adults exit skin
from ingestion of water containing larvae infected copepods (water fleas)
A. duodenale & N. americanus
= Hookworms
soil transmitted helminths Ancylostoma duodenale & Necator americanus cause hookworm infections worldwide– asymptomatic to GI symptoms with abdominal pain, diarrhea, and anemia
from touching infected human excrement
Ancylostoma braziliense
= Zoonotic Hookworms
cutaneous larva migrans with inflamed worm tunnels in the skin
Cat and dog feces may have Ancylostoma brazilense
Ascaris lumbricoides
= Giant Roundworm
#1 soil transmitted helminth and causes ascariasis worldwide – asymptomatic or GI symptoms (blockage); occasionally disseminates throughout the body (cough) Introduced by consuming human fecal material
Toxocara canis or T. cati
Ocular larva migrans when larvae migrate to the eye (ophthalmitis, retinal damage, blindness)
Visceral larva migrans when larvae migrate systemically (cough, fever, abdominal pain)
Humans are incidental hosts from ingesting eggs in cat or dog feces, or ingesting larvae in undercooked meat
Strongyloides stercoralis
= Threadworm
Worldwide soil-transmitted helminth
In HTLV-1 infected people, get severe disseminated strongyloidiasis
Larvae in fecal material enter through feet
may autoinfect via larvae exiting eggs and invading intestines or perianal skin and lead to hyperinfection
Trichostrongylus spp.
GI symtoms (pain diarrhea), from feces from an herbivorous host
Enterobius vermicularis
1 worm infection in U.S. - live in large intestine and females migrating and laying eggs at anus may cause itching at night
= Pinworm Infection
dx- cellophane tape test
Copepods (Microscopic)
microscopic little arthropods
Transmit Diphyllobothrium latum (fish/broad tapeworm), Dracunculus medinensis (dracunculiasis = Guinea worm),
Decapods
(Lobster, Crabs, Etc.)
Transmit Paragonimus spp. (lung flukes)
scorpions
venemous sting
occasionally cause death via action of toxins on numerous different ion channels
spiders
venemous bites causing necrosis (brown recluse) or neurotoxicity (black widow)
ticks
bites can cause tick paralysis via toxin
soft ticks transmit borrelia –> tick-borne relapsing fever
hard ticks transmit a variety of diseases
stuff transmitted by rocky mtn wood tick
tularemia, rocky mountain spotted fever, colorado tick fever, tick paralysis
stuff transmitted by blacklegged (deer) tick
anaplasmosis, babesiosis, lyme disease, febrile illness, powassan disease
stuff transmitted by itch mite (sarcoptes scabiei)
scabies “itch”, mange
stuff transmitted by follicle mites (demodex follicularum & D. brevis)
Folliculitis, blepharitis, rosacea
Dermatitis
Anoplura
(Sucking Lice)
Body louse transmits Rickettsia prowazekii (epidemic typhus) Bartonella quintana (trench fever) Borrelia recurrentis (louse-borne relapsing fever)
Pediculosis capitis
Head lice infestation
Pediculosis corporis
Pediculosis pubis (crabs)
Siphonaptera
= fleas
transmit cat scratch disease, plague, rickettsia typhi
Hemiptera
bed bugs
Kissing (reduviid bug) transmits American typanosomiasis = Chagas disease
Diptera- flies
flies
Flies bite and larvae infest human flesh (myasis, botfly
Transmit typhoid, paratyphoid, cholera, bacillary and amebic dysentery, giardiasis, helminths, trachoma, conjunctivitis, yaws, anthrax, tularemia, African sleeping sickness, leishmaniasis, onchocerciasis, loiasis, bartonellosis, and sandfly fever
diptera- mosquitos & midges
aedes- chikungunya, yellow fever, zika
culex- west nile
anapholes- malaria, west nile
hymenoptera (bees, ants, etc.)
sting
cockroaches
can trigger asthma via droppings
Coleoptera (Beetles)
Can be flour/grain beetles can be intermediate hosts for thorny headed worms or rat tapeworm
blister beetles - cause blistering via cantharidin
Lepidoptera (Moths, Etc.)
some caterpillars can cause chemical burns
centipedes
can have a venemous bite
milipedes
can exude vesicating venom
