Parasites Flashcards
What group of unicellular organisms has been the cause of more disease and death than any other group historically?
Protozoa (malaria, african sleeping sickness)
What is giardiasis?
caused by Giardia lamblia, a flagellate. Infects duodenum and jejunum of humans by ingestion of fecally contaminated water or food containing giardia cysts.
What is the pathophysiology of giardiasis?
Parasites attached to the bowel wall cause irritation and low-grade inflammation of the duodenal or jejunal mucosa. As the parasites pass into the colon, they typically encyst. Cysts are found in the stool in enormous numbers.
What are the symptoms of giardiasis?
diarrhea, malaise, steatorrhea, abdominal cramps, bloating, flatulence, nausea, weight loss, and vomiting. chronic infection leads to major weight loss, malabsorption, and depression. Stools are watery, greasy, foul-smelling.
How is giardiasis diagnosed?
STOOL Sample-fecal smear or ELISA to look for distinctive cysts. Examination of the duodenal contents as cyst production may be sporadic and not found in smear examination
What is the treatment for giardiasis?
Metronidazole (Flagyl) 250mg twice daily for 5 days. Oral quinacrine hydrochloride (Atabrine) and furazolidone (Furoxone) are alternatives
What is amoebiasis?
caused by Entamoeba histolytica or Dientamoeba fragilis in the large intestines. mostly a disease of travelers.
What is the pathophysiology of amoebiasis?
The cyst is ingested. The trophozoite emerges from the ingested cyst in the stomach and duodenum. Divides then passes to the cecum and produces a population of lumen-dwelling trophozoites. Trophozoites invade intestinal epithelium causing ulcers
What are possible complications of amoebiasis?
may undermine large areas of the mucosal surface. perforation into the peritoneal cavity. Secondary bacterial invasion, and accumulation of neutrophilic leukocytes. amoebic hepatitis or liver abscess
What are the symptoms of amoebiasis?
abdominal tenderness, Fulminating dysentery and dehydration. less acute: Episodic diarrhea, n/v, and urgent desire to defecate. weeks of cramps, loss of appetite, weight loss and malaise
How is amoebiasis diagnosed?
Stool Specimens or enzyme immnoassay
What is the treatment for amoebiasis?
Asymptomatic: Paromomycin and diloxanide furoate 500 mg tid x 10 days. Symptomatic: Metronidazole 750 mg tid for 5-10 days followed by diloxanide
What are the four species of plasmodium responsible for human malaria?
Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, Plasmodium falciparum (very lethal)
What are the symptoms of malaria?
Chills, Night sweats, Fever, Headache, Muscle pain, Cough and chest pain, Splenomegaly, hepatomegaly
What is congenital malaria?
should be considered in febrile newborns/infants who could have been infected by mother. can occur if the mother became infected during her pregnancy or from an infection acquired months or years before.
What is prophylaxis for malaria?
Chloroquine phosphate 500 mg weekly, continue 6 weeks after leaving area (add Fansidar in area w/cholorquine resistance). Or Primiquine phosphate 26.3 mg daily, start 1-2 days before travel and continue 7 days after leaving area
What is treatment options for malaria?
Chloroquine (most strains of Plasmodium show resistance). Atovaquone & proguanil (Malarone). Hydroxychloroquine(Plaquenil). Doxycycline. Mefloquine(Larium)
What is cryptosporidiosis?
caused by protozoan parasite Cryptosporidium hominis. one of the most common causes of water bourne illness in US
What is the pathogenesis of cryptosporidiosis?
found under the outer membrane of the cells lining the stomach or intestine. Oocysts, passed into feces are the infective agents.
What are the symptoms of cryptosporidium?
Stomach cramps, watery diarrhea, dehydration, weight loss, vomiting, fever, severe malabsorption, electrolyte imbalance
What is toxoplasmosis?
caused by a coccidian protozoa toxoplasma gondii. Hosts are cat species. Many ppl infected but very few immunocompetent patients have symptoms
What is the pathogenesis of toxoplasmosis?
Oocysts develop in the cat GI tract, and pass out via the feces. the oocyst opens in the human’s duodenum and releases the sporozoites that pass through the gut wall, and invade macrophages. They penetrate nerve cells, where they multiply to form tissue cysts, initiating the chronic stage of disease.
What are symptoms of toxoplasmosis in an immune compromised patient?
hepatitis, pneumonia, blindness, and severe neurological disorders
What are symptoms of toxoplasmosis in an immunocompetent patient?
Body aches, Swollen lymph nodes, Headache, Fever, Fatigue, Occasionally, a sore throat
What is toxoplasmosis congenital infection occur?
Develops only when non-immune mothers are infected during pregnancy. Leads to stillbirths and is a major cause of blindness and other congenital defects
How is toxoplasmosis diagnosed?
detection of Toxoplasma specific antibodies in blood is primary method. can also use other body fluids/biopsies.
What is the treatment of toxoplasmosis?
Acute infections: pyrimethamine 50-75 mg orally once a day with 1-4 g of a sulfonamide for 1-3 weeks. For pregnancy spiramycin (Rovamycine) 1-2 grams BID until delivery
Describe a pinworm infection
caused by enterobius vermicularis. Fecal- Oral route. Worms resides in cecum, colon, crawl out of anus at night. Symptoms: ITCHY BUTT! Squirming when sitting
How is a pinworm infection diagnosed?
Cellophane Tape Test-Wrap a piece of tape around a glass slide (sticky side out). Touch the slide to the patient’s perianal skin in four quadrants. Examine it under a microscope to find pinworm eggs. The best sample is collected either in the early morning before bathing or several hours after going to bed
What is the treatment for a pinworm infection?
Pyrantel pamoate (Pin X) 11 mg/kg once. Repeat dose in 2 weeks. Or Mebendazole (Vermox) 100 mg as a single dose; may repeat in 2-3 weeks. Treat the whole family
What is ascariasis?
caused by ascaris lumbricoides (round worms).
What is the pathogenesis of ascariasis (roundworm infection)?
Humans are infected by ingesting worm eggs.
The eggs hatch in the small intestine, and the larvae migrate through the gut wall into the bloodstream and then to the lungs. They enter the alveoli, pass up the bronchi and trachea with coughing, and are swallowed. Within the small intestine, they become adults
Where does the major damage from a roundworm infection occur?
during larval migration. principal sites of tissue reaction are the lungs, where inflammation with an eosinophilic exudate occurs in response to larval antigens. Large infestations may cause intestinal obstruction
How is ascariasis (round worm infection) diagnosed?
detection of oval egg w/irregular surface in the stool. occasionally see adult worms in stool
What is the treatment of ascariasis (round worms)?
Mebendazole 100 mg BID for 3 days or 500 mg as a single dose, and pyrantel 11 mg/kg administered as a single dose
What is the pathogenesis of necator americanus (hookworm)?
filariform larvae in moist soil penetrate the skin, usually of the feet or legs. They are carried by the blood to the lungs, migrate into the alveoli and up the bronchi and trachea, and then are swallowed. They develop into adults in the small intestine, attaching to the wall with cutting plates (hooks).
Where does the major damage occur due to necator americanus (hookworm)?
loss of blood at the site of attachment in the small intestine because they feed on blood from the capillaries of the intestinal villi
What are symptoms of necator americanus (hookworm)?
Weakness and pallor, microcytic anemia, bloody stools, Pneumonia with eosinophilia,
How is a necator americanus (hookworm) infection diagnosed?
observation of eggs in the stool. eosinophilia
What is treatment of necator americanus (hookworm)?
mebendazole and pyrantel pamoate
What is trichinosis?
Caused by trichinella spiralis. Pigs are major reservoirs and humans are infected by eating raw or undercooked meat containing larvae
What is the pathogenesis of trichinosis?
The larvae excyst and mature into adults within the mucosa of the small intestine. Eggs hatch within the adult females, and larvae are released and develop only in striated muscle cells. Within these “nurse cells,” they encyst within a fibrous capsule and can remain viable for several years but eventually calcify
What are symptoms of trichinosis?
fever, muscle pain, periorbital edema, eosinophilia, subconjunctival hemorrhages, cardiac and CNS disease
How is trichinosis diagnosed?
Muscle biopsy reveals larvae within striated muscle, bentonite flocculation test positive after 3 wks
What is the treatment for trichinosis?
There is no treatment. for severe symptoms, steroids plus mebendazole can be tried. Thiabendazole is effective against the adult intestinal worms early in infection.
What is toxocara (dog worm)?
caused by toxocara canis. Infected dogs pass eggs in the feces. Humans ingest contaminated soil and hatch into larvae in the small intestines. The larvae migrate, are encapsulated, and die
What are the clinical findings of toxocara (dog worm)?
Results in two syndromes: Visceralis larva migrans and Occular larva migrans. granulomas form around the dead larvae. Fever, hepatomegaly, and eosinophilia are common.
What are common symptoms of occular larva migrans.
unilateral visual impairment causing failing vision and subsequent strabismus. The typical lesion is a whitish elevated granuloma
How is toxocara (dogworm) diagnosed?
visualization of larvae in tissue. hypergammaglobulinemia and eosinophila support diagnosis
What is the treatment of toxocara (dog worm)?
albendazole 400 mg orally BID for 5-20 days or mebendazole100 to 200 mg orally BID for 5 days
What is anisakiasis?
caused by Anisakis simplex. the larvae are ingested in raw seafood and can penetrate stomach or intestinal submucosa
What are symptoms of anisakiasis?
Gastroenteritis, abdominal pain, eosinophilia, and bloody stool. Acute infection can resemble appendicitis, and chronic infection can resemble gastrointestinal cancer
How is anisakiasis diagnosed?
endoscopically or lapratotomy. Microbiologic and serologic tests are not helpful in the diagnosis
What is the treatment for anisakiasis?
no effective drugs. Surgical removal may be necessary
What causes tapeworm (Cestode) infections?
Taenia solium (pork tapeworm) or taenia saginata (beef tapeworm)
What are symptoms of a tapeworm (Cestode) infection?
asymptomatic, but malaise and mild cramps can occur. In some, proglottids(segment or joint of tapeworm) appear in the stools and may even protrude from the anus.
How is a tapeworm (Cestode) infection diagnosed?
gravid proglottids with 15–20 uterine branches in the stools. Eggs are found in the stools less often than are the proglottids
What is the treatment for a tapeworm (cestode) infection?
Praziquantel (Biltricide) 5-10 mg/kg orally one time
What is filiariasis?
caused by filarial nematodes Wuchereria bancrofti and Brugia malayi. Spread by mosquitoes. Causes lymphatic filariasis (elephantiasis)
What are symptoms of filiariasis?
Asymptomatic: patients have hidden damage to the lymphatic system and kidneys. Acute: attacks of ‘filarial fever’ (pain and inflammation of lymph nodes and ducts, fever, n/v). Chronic: elephantiasis and hydrocoele in males or enlarged breasts in females
how is filiariasis diagnosed?
identification of microfilariae in the blood by microscopic examination. microfilariae circulate nocturnally, making blood collection an issue. A “card test” for parasite antigens requires only a small amount of blood
What are treatment options for filiariasis?
Diethylcarbamazine (DEC) 6 mg/kg/day PO x 14d. Albendazole 400 mg orally BID for 10 days. Ivermectin 0.2 mg/kg orally once
