What are the three categories of helminths that are pathogenic to humans
Cestodes (tapeworms)
Trematodes (flukes)
Nematodes (roundworms)
What are helminths
macroscopic, eukaryotic, multicellular worms
can the larvae of helminths typically support themselves?
no, they typically need support from intermediate hosts
What does it mean that helminths can be dioecious or monoecious?
Dioecious means that there are male and female worms that need to “get together” to reproduce
monoecious means that the worm has both male and female sex organs
What types of helminths are dioecious
blood flukes and nematodes
What types of helminths are monecious
all helminths except blood flukes and nematodes
Cestodes and trematodes are both platyhelminths, what does that mean
that they are flatworms
how long do helminth infections last
usually years
What is the immune response generated by helminths
a TH-2 immune response with eosinophilia, mucosal mastocytosis, and elevated IgE
How well does the immune system work against helminths
it struggles to completely eliminate the helminths, and reinfections are common, but the parasite load does decrease over time reflecting partial immunity
What are the two different places you find helminths in the body, and what are the problems they cause
Intestinal helminths = anemia from chronic blood loss
Systemic helminths = organ damage from inflammatory responses to eggs or worms
What are some of the larger problems caused by helminths
liver failure
epilepsy
elephantitis
do helminths generally replicate in mammalian hosts?
nope, passage through intermediate hosts of through soil and water is required
do helminth infections have a high morbidity rate
yes
What are the three ways helminths can enter the body
through the mouth
bite of insect vector
penetration (burrowing through skin)
Where in the body do helminths localize
liver, lungs, intestines, CNS Dermal and lymph tissue Blood vessels (around intestine and bladder)
What are the two ways helminths directly cause damage
They cause cysts to grow in organs which damages them by putting pressure on them
they physically block intestines
What is the beef tapeworm
taenia sangiata
what is the pork tapeworm
taenia solium
Which humans have the high incidence of infection with Taenia
those working in close proximity to livestock (cows and pigs)
How do the cattle and swine get infected with taenia
by eating contaminated vegitation
What is Cysticerci
the larvae of helminths in meat
What are the body parts of Cestodes (tapeworms - taenia)
Scolex - point of attachment chain of proglottids Those near the scolex are immature those near the middle are mature those near the end are gravid (full of fertilized eggs)
What happens with the gravid proglottids (gravid meaning full of fertilized eggs)
they are released into the feces
How many proglottids can a mature T. sanginita worm have, and how many eggs does each have
they can have 1-2000 proglottids, each of those having about 100,000 eggs.
how many proglottids do infected humans pass per day
6
Where do the taenia attach
the intestinal epithelium
do most humans infected with taenia have symptoms
nope, they just shed proglottids (they only have symptoms if the worm gets large enough to block the intestines)
How do you prevent taenia infection
thoroughly cooking or freezing meat
How large can taenia sanginita become
10 meters long
does the scolex of taenia sanginita have hooks
nope
what happens to the proglottids of taenia sanginitia
they are relesed into feces, then the eggs develop into onchospheres, which leave animal intestines and encyst into animal tissues. They develop there into cysticerci, which are ingested, then develop into adult worms
What is the treatment for taenia sanginata
niclosamide or PTZ
Can humans become the intermediate host of taenia solium
yes, but this is rare because the cysticerci develop in the human muscle, but this is a dead end for the taenia solium because the human tissue doesn’t get eaten
can cysticerci in humans be pathogenic
yep, it can develop in the eye, CNS, and the heart
What can cysticerci in the CNS (neurocysticerosis) cause
epilepsy, meningitis, and encephalitis
how can neurocysticerosis be diagnosed
biopsy, CAT scan, MRI, look for subcutaneous cysticericosis first
how are cysticercosis treated
phenothiazine (PTZ)
corticosteroids
surgery
What are echinococcus granulosus
tapeworms of canines
how many proglottids do echinococcus granulosus have
3, one immature, one mature, and one gravid (each time the neck forms a new proglottid the gravid one falls off)
how are canines infected by echinococcus granulosus
by eating cysticerci in various herbivore hosts
what happens to humans with echinococcus granulosus
they can become accidental intermediate hosts if they ingest something contaminated with dog feces. they get Hydatid Disease
What is hydatid disease
an infection of echinococcus granulosus cysticerci. those cysticerci can grow and form hydatid cysts, this can cause tissue disfunction and if there are large numbers, death
What are trematodes
flukes, flat and leaf-shaped worms
what are the suckers like on trematodes
there are oral and ventral suckers that allow for attachment and nutrient obtaining
are trematodes dioecious or monoecious
they can be either
What is the most important trematode infector of humans
Schistosoma
how does a human infection of Schistosoma occur
motile cercariae in contanimated fresh water penetrate intact skin with the proteases stored in their head. Then they lose their tails and migrate via the circulation to the liver
where do Schistosoma mature
in the liver
do Schistosoma multiply in the host
nope, they do release eggs however
what do the eggs of Schistosoma elicit from the immune system
a granulomatous inflammatory response
What is another name for schistosoma
blood flukes
are blood flukes dioecious or monoecious
dioecious
What disease do blood flukes cause
schistosomiasis
What are the three species of Schistosoma
Schistosoma mansonii
Schistosoma haemotobium
Schistosoma Japonicum
does anything occur where a cercariae enters the skin
sometimes dermatitis
how serious can blood flukes be
they can become chronic and fatal
how do you prevent blood flukes
improved sanitation and avoiding contact with contaminated water
how do Schistosoma worms evade the immune system
by absorbing host complement regulatory proteins onto their surface
What is acuter Schistosomiasis
(katayama fever)
What does an early immune response to Schistosoma demonstrate
Th1
What is the overall immune response to Schistosoma
Th2, eosinophilia, elevated IgE, type 2 granulomas surrounding the eggs
What characterized a type 2 granuloma
TH2 cells, eosinophilias, macrophages, and fibroblasts
What can the type 2 granulomas caused by blood flukes do the tissue in which they are
they are in the liver, and they can block the liver sinusoids and impede blood flow. this can eventually lead to Cirrhosis
What are nematodes
long cylindrical worms with tapered ends, and complete digestive tracts
are nematodes dioecious or monoecious
dioecious
What are the reproductive strategies of nematodes
- shed eggs into lumen of the intestine (fecal-oral transmission)
- shed eggs into the soil (larvae penetrate skin)
- encyst in muscle tissue (eaten if undercooked)
- mosquitos
Which nematode infection is the most common and which nematode is the largest to infect humans
Ascaris lumbricoides (both most common and largest)
where do in Ascaris lumbricoides an endemic
the SE US
where do Ascaris lumbricoides reproduce
the small intestine
what happens to ingested Ascaris lumbricoides
the larvae enter the blood, go to the lungs, get coughed up and swollowed, mature in intestine
What happens when Ascaris lumbridoides migrate through the lung
you get loefflers sydrome = eosinophilic pneumonitis
What happens when Ascaris lumbricoides live in the GI
pain, diarrhea, intestinal obstruction
what happens when Ascaris lumbricoides live in the pancreatic liver or ducts
it is life threatening
What are the problems with Ascaris lumbricoides
the migrating larvae (int - blood - lungs - sto - int) - potent allergies - ascaris pneumonia - asthma Undernourishment abdominal pain, eye pain, asthma, insomnia death (if they block the intestines) penitration to peritoneum wandering worms
what causes Ascaris lumbricoides to wander
the female wants to burrow in the male, if it can’t find one the female begins to borrow
Where can Ascaris lumbricoides worms end up
intestines liver lungs in feces stomatch (puked out) esophagus, trachea
how is a Ascaris lumbrcoides infection diagnosed
barium enema
juveniles in sputum
how is an Ascaris lumbricoides infection treated
Mebendazole
What is the sceintific name for the whip worm
Thrichuris trichuria
What is the cycle of a whip worm infection
eggs to soil to mouth, hatching to adults in intestine, thread through the mucosa
How does thrichuris trichuria cause pathologies
due to the worm burden, more than 100 worms
What are the problem a whip worm infection can cause
death (if the worm burden is high) dysentery anemia growth retardation tenesmus prolapsed rectum
What is the second most common nematode infection
hook worms
what are the two types of hookworms that infect humans
ancylostoma duodenale
necator americanus
what is the infectious life cycle of hookworms
larvae in soil
burrow through skin
carried in blood to heart and lungs
in lungs they burrow in the mucosa and migrate up and get swallowed
in the intestines the attach, feed on blood, mature and mate
how is a hookworm infection treated
albendazole
how is a hookworm infection prevented
by wearing shoes
What is the common name for enterobius vermicularis
the pinworm
what is the most common parasitic worm in the US
the pinworm (humans are the only host for the enterobius)
where do female pinworms lay their eggs
around the anus
what is the main symptom caused by pinworms
intense perianal intching
how are pinworm infections prevented
preventing fecal oral spread (itching of the anus - worms under fingerails)
what is the scotch tape diagnosis for
enterobius vermincularis
What is the causitive agent of filariasis
wuchereria bancrofti
Where do the wuchereria bancrofti typically infect
lymph tissue and subcutaneous tissue
How is wuchereria bancrofti transmitted
female mosquitoes of some sort, they get the immature forms from one human, then pass them to another in its next form
What are the initial symptoms of lymphatic filariasis
it is typically initially asymptomatic
what is the end result of lymphatic filariasis
elephatiasis
what is elephantiasis
when lymph becomes blocked and pools up in the cutaneious and subcutaneous areas, they get swollen and hardened
how do you prevent wuchereria bancrofti infection
avoiding infected mosquitoes
