Roundworms Flashcards
What is the most common intestinal helminth in humans?
Ascaris lumbricoides
30-70% of people who travel outside of US will get a GI infections
How to diagnosis parasites and helminths?
Usually stool cultures for ova and parasites (O and P)
only done when persistent or other risk factors like travel, occupational risks, well water, etc. are present
What are common characteristics within helminth populations?
Usually live in warm/tropical climates
Usually ingestion of egg/larvae via oral fecal rout (contaminated water)
No asexual reproduction
- exception is echinococcus species
Are all Extracellular organisms
- exception is trichinella
Are usually easier to treat until they invade tissues
Why is eosinophila most commonly seen in patients with parasitic helminths?
Immunity to parasites requires TH2, IgE and eosinophil heavy responses
- this is because parasites are usually too big and requires IgE to coat parasites in order to cause degranulation of eosinophils
What is larva migrans?
Is a symptom that arises in some helminths (especially hook worms)
Shows outlining of worms based on their migration pattern due to mass inflammation reactions to the worms
- looks like red worm patterns along the skin “trail of inflammation”
What are the three main classes of helminths?
Nematodes
Cestodes
Trematodes
Nematodes include what main types of helminths?
Pinworms
- enterobius species
Whipworms
Hookworms
Threadworms
Roundworms
- ascariasis species
Ascaris Lumbricoides
A giant roundworm
- 15-50cm long
Transmitted via fecal-oral route
also possible via ascaris suum subspecies seen in poorly cooked pork
Has eggs that look very prominent and “bumpy”
Adult worms can obstruct the small bowel, biliary system and/or ileocecal valve and ultimately perforation if not treated.
Pathogenesis of ascaris
1) eggs ingested from contaminated soil and food
2) hatch in duodenum
3) penetrate mucosa and migrate within the circulatory system
4) larvae lodge in lung capillaries
- they are so huge they get lodged here
5) penetrate alveoli and migrate up to the trachea and pharynx (causes coughing)
6) larvae are coughed up and reswallowed to mature into adults in the intestines
Enterobius vermicularis
Are nocturnal pinworms that induces anal pruritus in hosts
- eggs are laid around the perianal area by female worms who migrate down the colon at night
Eggs cause hypersensitivity reactions to eggs which leads to scratch and subsequent hand-mouth transmission
- this is especially true in children
diagnosed via the scotch tape method
Eggs are smooth football shaped and worms are 40-50um
Strongyloides stercoralis
Are the most known threadworms
Penetrate the skin from contaminated soil
- Cause auto-infection that is sustained for years. In situations where immunosuppression occurs, fatal hyper infections are known to produce*
- autoinfections occur when the larvae penetrate intestinal mucosa and migrate to other organs
Risk factors:
- military service in tropical areas
- immigrant populations
- organ transplant
- daycares
Diagnosis = size of rhabditiform larvae (250mu usually) in O and P
Clinical symptoms of Strongyloides stercoralis infections
Normal:
- severe diarrhea
- abdominal pain
- GI bleeding
- nausea/vomiting
Abnormal: (only seen in if they migrate via autoinfections)
- Lungs = dry cough /wheezing/hemoptysis
- sepsis/meningitis (worms bring enteric bacteria with them to the bloodstream and other organs producing sepsis)
- skin = rash, pruritus, larva currens
Anclystoma duodenale and necator americanus
Are hook worms
Attach to intestines via buccal teeth and are known for massive larva migrans hypersensitivity.
Produce “hookworm disease”
- migrate to intestines and produce abdominal discomfort and diarrhea
- also physical feed open tissue and blood = severe anemia and iron deficiency as well as fatigue
can also show unilateral subacute retinitis (worm in the eye)
Trichuris thrichiura
Are whipworms
- 30-50 mm long
Transmitted via fecal-oral route from contained food/soil
- wayyy more common in children
Often asymptomatic but if heavy worm burden is present, can present with:
- lower abdominal pain and distention
- diarrhea
- tenesmus and rectal prolapse
- *rarely appendicitis
Trichinella spiralis
Another hookworm
Almost always seen in raw/undercooked pork
Mature hookworms mate in the intestines of hosts and deposit eggs into intestinal walls
- Larva penetrate the intestinal lining upon hatching and move to skeletal muscles
Symptoms: (If symptoms are present, are infectious)
- periorbital edema* (most common)
- fever
- pulmonary discomfort
- myalgia
- nausea/vomiting
- pruritis
