Parasitic Worms Flashcards
Geohelminths
Soil transmitted nematodes
Biggest issue is poor water sanitation
Do the adults multiply inside you with helminths?
No, that’s different from parasitic protozoa
How do you get infected with geohelminths
Ingestion of eggs containing infective larvae = ascaris and whipworms
Infective larvae penetrate skin (typically feet) = hookworm and strongyloides
Key to diagnosis of geohelminths
Eggs or larvae in stools
Geohelminth infections most common in ___
Young children
Ascaris
- Lives in small intestine
- Produces eggs — comes out in soil
- You eat it, you get infected –> bloodstream –> lungs –> crawl up trachea and you swallow them
You get symptoms of PNA
Prevention: sanitation, drug treatment every 6 months
How long can eggs survive in soil?
10 years
2,000 eggs per female per day
Whipworm (Trichuriasis)
- Large intestine
- Inserts into mucosa and damages mucosa –> produce eggs –> you pick up the eggs
Light infections = no symptoms
Heavy infections = painful stool… can get rectal prolapse
Kids can get severely anemic (growth retardation and impaired cognitive development)
Hookworms
Most serious of pathogenesis
- small, living in small intestine
- infection occurs when larvae penetrate the skin - latch on to mucosa of small intestine
- muscles of pharynx pump blood out of your body, so degree of anemia depends upon # of these guys you have
- Heavy infection: abdominal pain, diarrhea, loss of appetite, weight loss, fatigue, anemia
Control measures for hookworms
- Latrines
- Shoes
- Carbon tetrachloride (treated people with cleaning fluid)
Strongyloidiasis
- Caused by strongyloides stercoralis
- Considered a neglected disease in the US
- Key to this is that it can cause autoinfection
- Small intestine
- larvae hatch out in small intestine, end up in stools and can infect others. These larvae can reinfect the individual = autoinfection.
- Same anemia and other symptoms as hookworms.
How are geohelminth infections diagnosed?
Based upon larvae in stools.
Pin worm
- Large bowel
- Life span of 11-35 days
- Gravid females migrate to perianal region at night and lay eggs –> infective within 6 hours
- Fecal oral transmission. Can auto-infect self. Very contaminative.
Symptoms: perianal pruritis so kids cant sleep.
How long are pin worm eggs infective?
20 days
How do you diagnose pin worm infection?
Scotch tape across butt at night, then on a slide.
Lymphatic Filariasis
Key: Adults live 10-15 years in the lymphatics. Cause blockage of drainage of lymphatics –> swelling in legs (elephantiasis)
- Infection by mosquito
- Does not build up overnight.
Larval stage of lymphatic filariasis
Called microfilaria - circulates in blood at night so that it can be picked up by mosquito.
River blindness
Onchocerciasis
- 2nd leading cause of blindness
- blackfly bites -> larvae don’t move, they grow into adults and become a nodule.
Heavy infections will have one or more of 3 conditions:
- skin rash
- eye disease
- nodules under skin
Does blindness come from adults or larvae in river blindness?
Larvae migrating across the skin.
Control of river blindness
Ivermectin treatment
Trichinosis (trichinella spiralis)
- from eating uncooked pork
- domestic infection through pigs has become rare in US and Europe
- larvae that you eat encyst in muscles, which is how you get the symptoms.
- maintained in the wild in bears etc.
- Death is rare but is due to myocarditis encephalitis and PNA
Most common cases of trichinosis come from wild meat, jerky or homemade sausage.
Larval migrans (Toxocariasis)
- neglected in US
- Dog and cat infection… humans are accidental human hosts
- Roundworms
- Once they start migration in you, they realize that they don’t have the right signals and end up going everywhere randomly.
- Never reach sexual maturity in us, so we can’t spread it.
Schistosomiasis
- in the mesentery and bladder
- Adults do not cause the pathology - the eggs produced do.
- Blood flukes (flatworms)
- Live 10-20 years producing eggs that cause pathology
- Very associated with water and snails.
- Males and females live in copulo for life.
Classic Symptoms of Schisto
- Rash or itchy skin early
- 1-2 months = chills, fever, cough, muscle aches
- Later infection = anemia, malnutrition, hepatosplenomegaly
Symptoms of Chronic schisto
- abdominal pain
- hepatosplenomegaly
- Blood in stool or urine
- Increased risk of bladder cancer
S. haematobium , japonicum and mansoni locations
S. haematobium = mesenteric blood vessels of bladder
S. Japonicum = mesenteric blood vessels of intestine
S. mansoni = mesenteric blood vessels of intestine
Pathogenesis of schisto
Egg deposition leads to granulomas. These can get out through the urine (via damage to the bladder wall) or feces
Tapeworms
Infected typically do not have symptoms
- Can get from inadequately cooked meat that contains infective larval stages
- Diagnose from eggs in stool, or segments of worm in stool.
- Not usually serious.
Cysticercosis
= Pork tapeworm. beef guy doesn’t do this.
- If you eat it, you can get larval stage… can end up in liver, brain, eyes, etc.
- Most common cause of symptomatic epilepsy
Diagnosis = symptoms, biopsy, radiological tests, antibodies or PCR.
Hydatid DIsease
= Echinococcosis
Big cysts
From eggs of canines
Fish tapeworm
- Adults compete for Vit B12 = anemia
- Larvae found in salmon, trout, perch, white fish, eel, perch
- Gefilte fish, ceviche, sushi,
- In small intestine, shed up to a million eggs per day
- Embyronate in water and go through 2 intermediate hosts and stages (crustacean and then a fish)
- Little or no symptoms
Hygeine Hypothesis
Increase in diagnosis of autoimmune diseases and allergies over 2nd half of 20th century
- prevalence is higher in urban than rural
- Environmental factors can be important but do not have consistent association with allergies and autoimmunities
- Childhood infections show strong negative correlation with both autoimmune disease and allergies.
