Parasitic Infections Flashcards
Amoebiasis?
Entamoeba histolytica: cysts that are viable in the soil and water for wks to mnths
how are amoebia cysts transmitted?
fecal to oral, fly droppings, or human to human contact; humans are the only hosts
what is the pathophys behind amoebiasis?
- cysts pass through to the intestines where they hatch
- trophozites invade the mucosa and induce necrosis
where are amebic ulcers most likely to be found?
mebic ulcers are typically flask shaped and occur anywhere in the large bowel or termical ileum
how deep do amebic ulcers go?
typically limited to the muscularis, but can penetrate the serosa
what are complications of amebic ulcers?
if they penetrate the serosa, may cause perforation, abscess, or peritonitis
what are some clinical finding of an amebic infection?
- intestinal
- colits
- extratestinal dz
what are sx of intestinal dz?
often asx
what are sx of amebic colitis?
-mild to moderate (few seimformed stools w/o blood) or SEVERE DYSENTERY (greater number of liquid stolls streaked with blood ro bits of necrotic tissues
what are some pt complaints in an amebic colitis? severe dz?
- cramps, fatigue, weight loss, increased flatulence
- cycles of remission and recurrence are tyical
-severe: prostrate and toxic with fever, colic, tenesmus, and vomiting
what may physical exam reveal in amebic infxn? (colitis)
distention, hyperperistalsis, generalized abdominal tendernes
what are some complications of amebic colitis?
appendicitis, bowel perforation, fulminant colitis, massive mucosal sloughing, hemorrhage
what do localized ulcerative lesions of the colon and localized granulomatous lesions of colon potentially cause?
pain, intestinal obstruction, hemorrhage
what is an ameboma?
a localized granulomatous lesions of the colon
what must amebomas be differentiated from?
colon cancer, TB, or lymphogranuloma venereum (via bx that will reveal granulation tissue)
what can extraintestinal amebic dz cause?
hepatic amebiasis and amebic liver asscess:
can be asx or result in sx either suddenly or gradually over days to months
what are findings of a extraintestinal amebic dz?
fever, pain, tender hepatomegaly, malaise, prostration, sweating, chills anorexia and weight loss
what other signs may pts with EI amebic dz present with?
think LUNG
coughing and right lower lung findings: if abscess is in the superior liver
what is a complication of amebic abscess?
can rupture and spill into the pleural, peritoneal, or pericardial space which can be fatal
where else and amebiasis present? (rare)
metastasize to lungs, brain, or genitalia
diagnostic studes for amebic dz?
- stool specimens
- sigmoidoscopy, colonoscopy, rectal biopsy
- serology
- CBC
- US, CT, MRI
what will stool specimens reveal in amebic dz
reveal cysts or trophozoites
what will scopies and bxo of rectum reveal?
ulcers; if collection of exudates found need to be examined for trophozoites
what will serology show in amebic dz?
-can detect antiboides of up to 10 years after infection, so can’t be used to differenctiate past from prsent infxn
what will a CBC show in amebic dz?
elevated WBC w/o eosinophilia
why get a US,CT, radioisotope or MRI in amebic dz
see size and location of abscess
how is an asymptomatic infection treated?
with luminal amebicide (diloxanide furoate, iodoquinol, or paromomycin)
what are ADRs of paromomycine?
N, D, abdominal crampsI
how are mild to mod infcts of amebic dz treated?
with tinidazole or metronidazole + luminal amebicide
alternatives: tetracycline + luminal amebicide followed by chloroquine
what else needs to be done in severe amebid dz infections?
- supportive care
- electrolyte replacement
- opioids to control bowel motility
*decrease risk of toxic megacolon
how are hepatic abscesses treated?
tinidazole or metronidazole plus a luminal amebicided followed by chloroquine
*if no response to tx w/in 3 days abscess should be drained
what are some complications of hepatic abscesses?
bacterial infxn, bleeding, peritoneal spillage
when is the recommended follow up time after amebic treament?
- at least 3 stool exams at 2-3 days intervals starting 2-4 wks after the end of tx
- colonoscopy can also be used to confirm
what is postdysenteric colitis?
may occur after severe amebic infection, but is usally self-limited, but may be a trigger for ulcerative colitis
where are hookworms endemic to?
moist tropics and subtropics
- southeastern US
- humans are the only host
how are hookworms transmitted?
eggs are passed in the stool and hatched in moist soil
how long do the hookworm larvae last?
- hours to weks
- penetrate skin and migrate int the bloodstream to the pulmonary capilliaries, where they destroy alveoli and are carried by cilia to the mouth
-
what happens once hookwork larvae are swallowed
the larvae attach to the samll bowel mucosa and suck blood
-once mature they release eggs to continue the cycle
what is a light infection defined by? hookworm
1000 eggs/g feces
what is a moderate hookworm infection?
2000-8000 eggs/g feces
what are some clinical findings in a hookworm infections?
-site of penetration is pruritic
what kind of rash is seen at the site of a hookworm penetrations?
erythematous dermatitis with maculopapular or vesicular eruption
-scratching can cause secondary bacterial infections
what are clinical features of the pulmonary stage of hookworm infexn?
-cough, wheeze, blood-tinged sputum, low grade fever
what are clinical fx of the intestinal stage if light hookworm infxn and adequate iron intact?
heavy infections?
- asx
- anorexia, D, vague pain, ulcer-like epigastric sx
- severe infxn: anemia, protein loss, and malabsroption
why do hookworms cause anemia?
they cause the laceration of capillaries and ingest extravasated blood
what may lead you to think a pt is infected with a parasite?
eosinophilia that is unexplained most likely due to the attachment of adult worms to the intestinal mucosa
-rupture RBC and degrae the Hb (why you see a hypochromic anemia)
dx of hook worm
eggs can be seen in stool examination, coupled with clinical manifestation and good history
- eosinophilia
- hypochromic microcytic anemia
tx of hook worm
albendazole
alternative: mebendazole or pyrantel
what are ADRs of albendazole? mebendazole?
abdominal pain, D, rash, uticaria,
rare: seizure, hepatitis, increased LFT
mebendazole: monitor liver fxn and CBC-neutropenia and agranulocytosis
what antihelminth drug should not be given to kids younger than 5?
pyrantel
what does supportive hookworm tx include?
high-protein diet, vitamines, and ferrous sulfate
what is cysticercosis
pork tapeworm that can infect brain
how is cysticercosis tx?
praziquantel that affects parasite cell membrane permeabilty
how does mebendazole and abendazole work?
by inhibiting formation of worm microtubules that prevents the uptake of glucose necessary for parasitic metabolism
what are pinworm?
enterobiasis ( Enterobius vermicularis
what are the only host for pinworms?
humans!
children are often more affected than adults
what is the life cycle of a pinworm?
adult worms are loosely attached to tthe mucosa, primarily in the cecum
- gravid F pass through the anus to lay eggs on the perianal skin (can lay a SHIT TON OF EGGS)
- this usually occurs at night
how long are the pinworm eggs viable for outside the host?
- 2-3 wks
how are pinworms spread?
via hands, food, drink, and fomites
- eggs swallowed and hatch in the duodenum,
- larvae pass to the cecum and mature in 3-4 wks
what is the lifspan of a pinworm?
30-45 days
clinical findings in a pinworm infxn?
- most asx
- perianal pruritus (crawling sensation worse at night)
- insomnia, weight loss, enuresis, and irritability
what may a PE show in a pt affected w/ pinworms?
reveal worms in the anus or stool
what are complications of scratching?
excoriations and secondary skin infections like impetigo
what are complications of untreated pinworm?
-vuvlvovaginitis, diverticulitis, appendicities, cystitis, and granulomatous rxns
how is pin worm dx?
pinworm paddle test: piece of cellophagne tape over the perianal skin, three tries over 3 consecutive nights yields a 90% sucess rate
what is a common adr of metronidazole?
GI upset
dysgeusia
black hairy tongue
tx of pinworm
albendazole, mebendazole or pyrantel given in a single dose and then repeated 2-4 weeks later
**hand washing and linen washing!!!!!
malaria vector?
anopheles mosquitoes
- eradicated in US, but about 1500 imported cases each year
- may cause local outbreaks bc of this
what are the common malaria causes? (species)
plasmodium vivax, plasmodium malariae,
plasmodium ovale, plasmodium faciparum
what bacteria cuases the highest mortality rate after infection?
p. falciparum due to “clustering” of infected cells in brain causing cerebral malaria
what is the life cycle/transmission of the malaria causing parasite?
1) the mosquito ingests the parasite, and sporozoites mature and get transferred to humans via saliva
2) the sporozoites invade the hepatocytes and mature as tissue schizonts. the schizonts escape the liver and invade RBC, where they multiply and cause rupture of the cell w/in 48 hours
3) the cycle of invasion, multiplication and RBC rupture continues
what is the incubation period for p. facipram
7-30 days, which can be very prolonged when on antimalarials
what is a delayed illness malaria?
This can happen particularly with P. vivax and P. ovale, both of which can produce dormant liver stage parasites; the liver stages may reactivate and cause disease months after the infective mosquito bite.)
what is the typical malarial attack?
lasts 6-10 hours:
a cold stage (sensation of cold, shivering)
a hot stage (fever, headaches, vomiting; seizures in young children)
and finally a sweating stage (sweats, return to normal temperature, tiredness)
*rarely seen
what contributes to the clinical presentation of malaria?
release of tissue necrosis factors and cytokines leads to fatiuge, HA, dizzy, GI coplaints, maylagia, arthralgias, backache and dry cough
what PE may been seen if sx last longer than 4 days?
liver and spleen enlargement
what are sx of infection with P. falciparum?
cerebral malaria, hyperpyrexia, hemolytic anemia, noncardiogenic pulmonary edem, actue tubular necrosis , adrenal insufficiency, cardiac dysrhythmias,
ARDS
*caused by RBC adhering to small blood vessels (cytoadherence) and causin small infarcts, capillary leakage, and organ dysfunction
what are clinical features of P. falciparum infxn?
pallor, petechiae, jaundic, hepatomegaly, and or splenomegaly
dx for malaria?
-blood films
‘-CBC
antibodies
what will you seen on blood films positive for malaria?
Blood smear with Geimsa stain or Wright stane
Thick and thin preparations
Gold standard, but requires reagents & experience interpreting
Also need specimen during acute infection or may get negative smear
what may be the percentage of infected RBC? 5-20%
can you look at antibodies for malaria?
not really,
antibodies will apper 8-10 days later, but that is too late for diagnostic benefit
antibodies also persist for 10 years, making the distinction btw old and new infection difficult
tx of malaria
chloroquine atovaquone-proguanil (Malarone®) artemether-lumefantrine (Coartem®) mefloquine (Lariam®) quinine quinidine doxycycline (used in combination with quinine) clindamycin (used in combination with quinine)
what can you sues in areas where chloroquine is resistant?
use mefloquine
what are side effects of chloroquine?
GI sx, HA, PRURITIS, dizziness, blurred vision, malaise, urticaria
what is the best medicine for malaria?
prevention!!!!
What must you check before starting someone on primaquine?
if they have G6PD deficiency
