Parasites Flashcards
Entamoeba histolytica
- Two stages, motile ameba and nonmotile cyst
- Colonize the cecum and colon
- Can leave “flask shaped” ulcerations of the intestinal mucosa
- Can have acute amebiasis with dysentery (bloody, mucous containg diarrhea)
- Diagnosed by its nucleus and the size of its cyst
Giardia intestinalis
- Most commonly diagnosed intestinal parasitic infection in the US and Canada
- Get it by ingesting inadequately treated water, contaminated uncooked vegitables and fruits, or person to person spread
- IgA deficiency is predisposing factor for symptomatic infection
- Has two forms with pear-shaped trophozoite or free-living stage with four pairs of flagella, binucleated (face-like image)
- Initially have watery stool that later becomes greasy, foul-smelling, and may float
Cryptosporidium
- Can undergo sexual or asexual reproduction
- Transmitted via fecal-oral route
- Produces watery diarrhea
- Generally self limiting to 1-2 weeks
- Diagnosed via acid-fast staining in stool or direct immunoflourescent stains
- Healthy individuals usually don’t require therapy
Cyclospora
- Prevalent in tropical and sub-tropical regions
- Profuse watery diarrhea
- Diagnosed via oocysts fluorescent under UV light, acid fast resistant; PCR
Enterobius vermicularis
- Roundworm, most common helminthic infection in US
- Acquired by ingestion of worm eggs
- Perianal itching, teeth grinding, insomnia, appendicitis, infection of female genital tract
- Diagnosed by looking for worms in the perianal region 2-3 hours after sleeping
Whipworm - Trichuris trichiura
- Roundworm, mostly found in tropical and in souther US
- Heavy worm burden leads to bloody, painful, mucus containing diarrhea, rectal prolapse in children, growth retardation, impaired cognitive development, and anemia in children
Scaris lumbricoides
- Largest of the intestinal roundworms - live and mate in the lumen of the small intestine, specifically the jejunum
- Most common worm infection of humans
- Transmission via fertilized egg that needs to develp in the soil
- Heavy infection leads to intestinal blockage, abdominal pain, indigestion, vomiting, diarrhea
- impaired growth, cough, inflammation of lungs due to eosinophil response to the larval antigens - mild cough to pneumonitis
Hookworms
- Necator americanus and Ancylostoma duodenale are major cause of iron-deficiency anemia in children and pregnant women
- Necator americanus found in southeast US
- Transmission via larvae from fecal contaminated soil penetrate intact skin
- Feed on blood from the capillaries of the intestinal villi
- In children, development of anemia and protein deficiency
- Koilonychias (brittle, spoon shaped nails), pale sclera, heart murmurs
- Prevention involves wearing shoes
Strongyloides stercoralis
- Smallest of all intestinal round worms (nematodes)
- Found in Southeastern US and Appalachia
- Can multiply in the host and the environment
- Transmission via penetration of skin by infectious larvae
- Hyperinfection can develop into disseminated infection that spreads everywhere (CNS, liver, kidney, etc)
- Symptoms will mimic peptic ulcers in addition to peripheral eosinophilia
Taeniasis
- Tapeworm that infects when human’s ingest raw or undercooked beef or pork containing larvae
- Can lead to cysticercosis (seizure causing disease)
- Beef tapeworm infected individuals usually have more symptoms
- Will note active passing of proglottids in the feces
Cysticercosis
Major cause of adult onset seizure in most low income countries
Ingestion of Taenia solium eggs found in feces of infected person, do not get from ingesting undercooked pork
Diagnosis requires MRI or CT brain scans
Fish tapeworm - Diphyllobothrium latum
Largest tapeworm infecting humans
Infected fish can be found in fresh water lakes of Minnesota, Michigan, Florida, and California
Ingestion of raw or undercooked fish
Major symptom includes Vitamin B12 deficiency
Fasciolopsis buski
Largest intestinal fluke at 1-3 inches
Found in South and Southeast Asia
Acquire by ingesting frest water aquatic plants
Attachment to the intestinal wall can cause inflammation, ulceration, and hemorrhage
Heavy infection leads to abdominal discomfort and continuous diarrhea
Marked eosinophilia
Diagnosis by the presence of eggs in stool - large, golden, bile-stained
Fasciola hepatica
Liver fluke
Parasite of sheep, cattle, and humans
Migration through liver may induce liver tenderness and hepatomegaly
Fasciola often infects the bile ducts and liver
Opisthorchis sinensin
Chinese liver flukes
Endemic throughout Asia with 25% of chinese immigrants to the US infected
Aquired by ingesting under prepared freshwater fish
Diagnosed with eosinophilia and elevated serum alkaline phosphatase levels
