parasites Flashcards
what is a parasite
animal or plant living in or on another and drawing nourishment from it
diagnosis of parasitic disease involves exposure history, clinical pattern of illness, ID in stool, blood, tissues, indirect evidence (serology, detection or parasitic antigens, DNA
what is a helminth
WORM
reproduce SEXUALLY usually within the host
pre-adult stage = OVA and LARVAE that live within or external to the host
what are protozoa
SMALL, UNICELLULAR organisms
have a nucleus and functioning organelles
reproduce quickly and ASEXUALLY in the host
have have a sexual phase in another host or vector
sub groups are based on motility (i.e amoeba, flagellates, ciliates, sporozoa/amicomplexa)
some protozoa have life stages alternating between proliferative stages (trophozoites) and dormant cysts
what are protozoa cysts
dormant phase
can survive in harsh conditions
allow the parasitic special to survive without a host
allow for transmission
what are protozoa trophozoites
actively feeding METABOLIC form of the protozoa
what are ectoparasites
insects
list the 3 classes of parasites
- protozoa (one celled organisms)
- helminths (worms)
- ectoparasites (insects)
list the 3 classes of helminth
- cestodes (tapeworms)
- nematodes (roundworms)
- trematodes (flatworms/flukes)
list the 4 classes of protozoa
- amoeba
- ciliates
- flagellates
- sporozoans
what is a definitive host
host of a parasite where SEXUAL reproduction of the parasite occurs
what is an intermediate host
animal essential to the COMPLETION of the LIFE CYCLE of the parasite
transmission requires a reservoir and route of infection
nematode body
UNsegmented
bilateral symmetry
fully functional digestive tract
long and cylindrical
male and female worms
nematode sexes
separate
have male and female worms
nematode infection/transmission
eggs/larvae ingestion, skin penetration, arthropod vector
nematode lifecycle
eggs –> several larvae stages –> adult stage
list 7 nematodes
- necator americanus (hookworm)
- Loa Loa (filaria)
- Wucheria bancroft (filaria)
- onchocerciasis
- ascaris lumbricoides
- strongyloides stertocalis
- enterobius vermicularis
hookworm
nematode
necator americanus
LARVAL stage of worm penetrates SKIN –> usually through FOOT causing infection in the foot
once it penetrates the skin, it is carried through teh blood vessels
heavy infections can result in childhood anemia
SOIL TRANSMITTED helminth
Loa Loa (filaria)
nematode
EYE worm
adult conjunctiva migration
transient calabar swellings
diagnosis via serology, microfilaria on BLOOD SMEAR
transmitted via CHRYSOPS fly
Wucheria bancroft (filaria)
nematode
ELEPHANTITIS
very common in some tropical zones
early symptoms = fever, lymphadenitis, transient edema
late obstruction = chronic edema and skin changes caused by blocked lymphatics
transmitted via MOSQUITO
onchoceriasis (filaria)
nematode
RIVER BLINDNESS
NO blood invasion
major cause of blindness–> skin disease in Africa and Yemen
diagnosis based on serology, skin snip, nodule biopsy
transmitted with SIMULIAN fly
Ascaris lumbricoides
nematode
prototypical roundworm
notable for LUNG MIGRATION phase–> larvae are coughed up, swallowed and mature in gut
excreted eggs need to embryonate in specific environmental conditions in soil before becoming infective–> therefore direct person to person transmission is not possible
heavy infection may result in bowel obstruction
Strongyloides stertocalis
nematode
MINUTE roundworm
can replicate and completed ENTIRE LIFECYCLE within a HUMAN
infection can persist for a human lifetime
SOIL TRANSMITTED helminth and is often acquired from skin penetration
Enterobius vermicularis
nematode
PINWORM
very common–> causes PRUTITUS ANI in kids
fecal-oral transmission
persists due to poor hygiene
eggs can persist in local environment
cestode body
are TAPEWORMS
large, can be up to meters long
live attached to MUCOSA in SMALL INTESTINE of host
use SCOLEX to attach which is an attachment organ with 4 ventral suckers with or without hooks
structure = chain of segments (proglottids) + neck + scolex
cestode sexes
hemaphroditic
cestode infection/transmission
can live for decades
infection is via egg/larvae ingestion
name a cestode
taenia solium (pork tapeworm)
taenia saginatum is cow tapeworm
dipnyllobotherium latum is from uncooked fish
echinococcus is from sheep
taenia solium
cestode
pork tapeworm
causes NEUROCYSTOCERCOSIS
most medically important tapeworm infection worldwide
most common parasite of CNS
most preventable cause of EPILEPSY
results from undercooked PORK–> humans eat adult tapeworm from pork–> human excretes eggs–> if another human ingests the eggs, eggs hatch and turn into CYSTECERCI in tissues, including in the brain
parenchymal disease (cysts–> degeneration–> calcification–> seizures)
extraparenchymal disease (sub-arachnoid space, ventricles, spine)
most important clinical goal is to CONTROL INFLAMMATION
trematode body
flatworms/flukes
first intermediate host is SOIL
second intermediate host is FISH/SHELLFISH
dorso-ventrally flattened, unsegmented, leaf-like or cynindrical structure
trematode sexes
hermaphroditic
trematode infection/transmission
require 1 or more intermediate hosts
infect through skin penetration or larvae ingestion
name 2 trematodes
- paragonimus westermani
2. schistosomiasis
paragonimus westermani
trematode
LUNG fluke
reservoir = wild and domestic carnivores
usually asymptomatic–> can have COUGH (often confused with TB, lung cancer)
rare cerebral disease
diagnosis through serology, sputum (eggs), eosinophilia
infection through LARVAE INGESTION
schistosomiasis
trematode
BLOOD fluke
cause of morbidity in Sub-Saharan Africa
acquired by swimming in freshwater lake or rivers
microscopic CERCARIAE burrow through skin and migrate to blood vessels surrounding target organs –> females lay eggs–> eggs penetrate into tissue through vessel walls –> eggs propelled into lumen –> pass in urine or stool
urogenital = S. haematobium intestinal/hepatic = S. mansoni, S. japonicum
acute infection is usually 4 weeks post-exposure and involves fever, diarrhea, eosinophilia
continued egg-laying leads to chronic inflammation and then to cancers, cirrhosis
list 5 ectoparasites
- scabies
- head lice
- body louse
- trench fever (body louse)
- bot fly (Dermatobium hominis)
which type of protozoa are intestinal protozoa
FLAGELLATE
i.e GIARDIA lamblia (“beaver fever”)
which type of protozoa are extraintestinal protozoa
PLASMODIUM (malaria)
list 3 diseases caused by protozoa
- malaria
- leishmania
- giardia lamblia
malaria vector
FEMALE ANOPHELES night-biting MOSQUITO
transmits through BITE
malaria species
P. falciparum P. vivax P. ovale P. malariae P. knowlesi
50% = falciparum
malaria reproduction
asexual cycle in RBCs (SHIZOGANY)
sexual reproduction in female anopheles mosquito (SPOROGANY)
malaria diagnosis method
thick and thin BLOOD SMEAR –> can determine species of plasmodium as well as % RBCs infected (parasitemia)
rapid antigen tests
what is the most important parasitic disease
malaria–> #1 cause of fever in returning travellers
symptoms of uncomplicated malaria
fevers rigors headaches diarrhea nausea
may be mistaken for viral infection
symptoms of complicated malaria
from P. FALCIPARUM
evidence of end-organ dysfunction (coma, renal failure)
mortality is 10-20% with Tx
P. falciparum
infection is a medical emergency
endemic in sub saharan africa
parasites induces formation of sticky “KNOBS” on RBCs which clog small vessels in brain and lungs
P. falciparum versus P. vivax
- dormant liver stage?
- disease severity?
- relapse?
- asymptomatic carriage?
- Tx
- P. falciparum NO; P. vivax YES
- P. falciparum 5% = severe; P. vivax risk of severe disease is not established
- P. falciparum NO; P. vivax YES
- P. falciparum = common; P. vivax very common
- P. falciparum = arteminisin combo therapy; P. vivax = chloroquine + 14 days primaquine
Leishmania vector
sandfly
Leishmania species
L. donovani
L. infantum
L. chagasi (chagas disease)
Leishmania diagnosis
skin biopsy
serology
Leishmania Tx
amphotericin B
topical ketoconazole
Leishmania clinical presentation
cause of ulcerated papule
subclinical infection is most common
HIV coinfection = reactivation
fever, lymphadenopathy, hepatomegaly, progressive MASSIVE SPLENOMEGALY
giardia lamblia
intestinal protozoa (flagellate)
most common GI intestinal protozoal infection in world
fecal oral transmission
may be asymptomatic
causes GI symptoms by EFFACEMENT OF VILLI via inciting inflammation at the intestinal brush border
this means that dietary FATS are absorbed poorly and result in “GREASY” STOOLS that FLOAT in the toilet
NEVER INVASIVE on its own, and will NOT cause bloody diarrhea
