4/10 Parasitology and Travel Med I Flashcards
2 kinds of worms
- Roundworms (intestinal and tissue)
- Flatworms (tapeworms, flukes)
indication of worm infection?
eosinophilia
T/F worms multiply in hosts
mostly false. most do not multiply in hosts
in worm infections, what is disease state determined by?
disease is determined by infecting numbers
general life-cycle of roundworm
- All produce and release eggs; some eggs mature and are released as larvae
- Do not multiply in host (must ingest more eggs in order to get more worms)
standard trmt of roundworms?
Bendazole – inhibits microtubule function, immobilizes and kills worms
What is this?
Pinworm
Enterobius vermicularis
What is this?
Pinworm
Enterobius vermicularis
What is the life cycle of the pinworm?
- EGG ingestion –> intestines where larvae mature in into adults. Female pinworms migrate to anal verge to expel eggs via feces
- Eggs remain infectious in the environment for 2wks – requires repeated treatments
Where do pinworms occur?
Worldwide (
children (30%), adults (15%))
How are Enterobius vermicularis diagnosed?
EGG, clear scotch tape prep from perianal area
Enterobius vermicularis treatment?
Bendazole - treat entire family for 2 weeks due to high recurrence of infection
Strongyloides stercoralis general life cycle?
- LARVAE penetrates skin -> transported to the lungs where it penetrate alveolar spaces -> swallowed -> small intestines
- Adult F deposit their eggs into the intestinal mucosa, from which larvae hatch and migrate to the lumen (no eggs in stool!!)
- Larvae produced in small bowel can either be
- passed into stool as the non-infectious form
- become infectious and penetrate the intestinal mucosa, taking gram (-) bacteria with them, into the blood stream, resulting in a hyperinfection (+bacterial sepsis) where it goes on to reinfect the lungs, starting the cycle again
How long can Strongyloides stercoralis last in the body?
When is it usually reactivated?
Latent period (up to 30 years); can be reactivated by steroids -> hyperinfection
What is hyperfinection? What is it caused by?
Strongyloides stercoralis - occurs when it penetrates the intestinal mucosa, taking gram (-) bacteria with them, into the blood stream, resulting in a hyperinfection (+bacterial sepsis) where it goes on to reinfect the lungs, starting the cycle again
Where is Strongyloides stercoralis found?
Worldwide - warm, moist climates
symptoms of Strongyloides stercoralis?
- Asxs
- GI symptoms - nausea, diarrhea, cutaneous/pulmonary sx
- Hyperinfection – fever, pulm, sepsis
- Symptoms related to invasion (itchy rash)
what bug is this?
Strongyloides stercoralis
How is Strongyloides stercoralis diagnosed?
- LARVA (non-infectious; feces), serology
- Hyperinfection
- blood culture - gram (-) rods
- sputum exam with microscopic ring worm larvae
How is Strongyloides stercoralis treated?
- Bendazole (or Ivermectin)
- Wear shoes!
What worm is this?
Ascaris lumbricoides
Life-cycle of this bug?
- EGG ingestion > develops into larvae that penetrates the bowel wall > migrates to the lungs and break into alveoli space > coughed up and swallowed
- Mating occur in the small bowel g produces egg that are shed in feces (can contaminate agriculture)
Where does ascaris usually affect?
- SE USA
- Northeast pigs
- Tropics (haiti)
What are the symptoms of Ascaris?
- Light infection = Asxs; excreted into stool (usually freaks people out)
- Heavy infection > gut/bile obstruction, malabsorption
- Hemorrhagic pneumonitis (eosinophilic pneumonia) in lung
What is this? How is it diagnosed
ascaris lumbricoides
EGG (feces) – see lumpy bumpy coat
How do you treat Ascaris lumbricoides?
Piperazine – paralyzes the worm
What are the two types of Larva Migrans?
what is it also known as?
- Visceral Larva Migrans
- Ocular Larva Migrans
- aka Dog/cat Ascarid “Toxocariasis”
Life cycle of Visceral Larva migrans?
- EGG ingested from dog/cat feces in soil
- Eggs hatch > larvae penetrates the intestinal wall, travel with the blood stream to various organs ((liver, heart, lungs, brain, muscle, eyes) and cause local reactions
What are the dead end hosts for visceral larva? Why?
humans are dead-end, accidental hosts (it can infect but not mature/complete its life cycle in humans; ie no eggs in stool; usually completes its life cycle in dogs)
Who does visceral larva migrans affect?
Mostly kids
Clinical presentation of visceral larva migrans?
- Asxs that progresses to fever, hepatomegaly
- Retinoblastoma-like in eye (blood work shows eosinophilia compared to Rb)
How do you diagnose visceral larva migrans?
- Serology
- Tissue Bx - eosinophilic granuloma
What is this?
Visceral Larva Migrans
Treatment for Visceral Larva Migrans?
- Bendazole
- Diethylcarbamazine
two types of flatworms?
- Flukes – reproduce sexually in humans, asexually in snails
- Tapeworms – scolex/head, mucosal attachment by sucker/hooklets, proglttids produce eggs, distal most mature, absorb nutrients in intestine through entire length of body
What is this?
Schistosomiasis (Flukes)
S. mansoni (lateral spike)
What is this?
Schistosomiasis (Flukes)
S. hematobium (apical)
What is this?
Schistosomiasis (Flukes)
S. japonicum (smallest)
Jen remembers this one because it looks like the Japanese flag.
What is the general life cycle of Schistosomiasis (Flukes)?
- CERCARIA (released from snails) penetrates unbroken skin and enters circulatory system to reach the portal vein, where it mature into adults.
- Paired adult worms migrate to mesenteric/bladder veins and mature to adult form -> produce EGGS that
- burrow through the intestinal wall and shed in stool/urine, back to water to snails
- cause disease by circulating back to the liver
Why is it that there is no host immune reaction against Schistosomiasis (Flukes)?
Adults adopt host antigens, rapidly turnover their surface coat = NO host immune reaction!
Where does schistosomes usually occur?
Freshwater
Tropics
Egypt
symptoms of schistosomiasis??
- Early Sx: fever, eosinophilia
Liver – “pipestem fibrosis” = cirrhosis, portal HTN, ascites and esophageal varices- biosynthetic function is maintained eg. clotting factors and albumin levels are not markedly changed
- Egg granulomas in lung, brain, spinal cord
- Bladder: hematuria or SCC (due to chronic inflammation)
- Swimmer’s Itch – cercariae in skin
What worm causes Pipestem fibrosis?
What is the immune response like?
Schistosomiasis (Flukes) - acute TH1 response with IFNG and TNF, but as chronic disease supervenes, shift toward TH2 with eosinophilia, fibrosis
How do you diagnose Schistosomiasis (Flukes)?
- EGG (O&P of stool, biopsy)
- Rectal Biopsy – detect old infections
How is Schistosomiasis (Flukes) treated?
Praziquantel (does not work as prophylaxis)
