Parasites Flashcards
Giardia lamblia: pathogenesis
- inhabits duodenum, upper jejunum
- Forms: trophozoite (cannot survive in stool), cyst
trophozoite adheres to intestinal epithelium by sucking disc–> brush border injury –> stunting and shortening of villi
Giardia lamblia: clinical features
diarrhea, fat malabsorption, dull epigastric pain, flatulence, stool with mucus and fat (steatorrhea)
- can lead to chronic diarrhea, malabsorption, fat, vit A , weight loss
Giardia lamblia: lab diagnosis and treatment
detection of cysts and trophozoites in stool
metronidazole / tinidazole
Entamoeba histolytica
intestinal and extra-intestinal amebiasis
forms: trophozoite (present in diarrhea) , cyst (only in lumen of colon and formed stool)
oral fecal route
Entamoeba histolytica: Intestinal amebiasis pathogenesis
- amebic colitis (mucosa invaded, trophozoite penetration aided by histolysin into epithelial cell –> damages mucosal epithelium –> necrosis -> ulcers)
- flask shaped amebic ulcers (multiple ulcers forming large necrotic lesion)
Entamoeba histolytica: intestinal amebiasis clinical features
- diarrhea, abdominal symptoms, dysentery
ameboma: granulomatous pseudotumoural growth –> develops from chronic ulcer
- necrosis, inflammation, edema of mucosa and submucosa of colon
Entamoeba histolytica: Extraintestinal amebiasis pathogenesis
hematogenous spread of trophozoites –> amebic abscesses extraintestinal sites
esp liver –> lysosomal damage and cytokines from inflammatory cells –> liver damage
Liver - thick pus in centre of abscess, trophozoite in abscess, abscess may rupture into lungs and pericardium
Entamoeba histolytica: lab diagnosis
trophozoite and cyst in stool
trophozoite in tissue (in pus, in liver biopsy)
serological tests for antigen/antibody
Entamoeba histolytica: treatment
luminal amebicides:
Tetracycline
Tissue amebicides: chloroquine
both luminal and tissue: metronidazole
Blastocystis hominis
- large intestine
Forms:
1. vacuolated form: large central vacuole, cytoplasm and nuclei pushed to periphery
2. ameboid form: polymorphous, larger than vacuolated form
3. granular form
4. cystic form: thick multilayered cyst wall
oral fecal route
Blastocystis hominis: patho and clinical features
-diarrhea, abdominal pain, abdominal distention, nausea, vomiting
- mostly asymptomatic, mostly immunologically compromised
Blastocystis hominis: lab diagnosis and treatment
- vacuolar form in stool
PCR test
Treatment: metronidazole
Hookworm: patho and clinical features
Ancyclostoma duodenale
Necator americanus
filariform larva penetrates skin –> ground itch, erythematous papular rash, Loeffler’s syndrome (cough, dyspnea, hyper-eosinophilia), black stool
Chronically: leads to iron deficiency microcytic hypochromic anemia
Hookworm: Lab diagnosis and treatment
- microsopy, stool culture , morphology
Mebendazole/ albendazole, iron supplement
Trichuris trichiura: patho
whipworm in large intestine (cecum and ascending colon)
anterior portion - thin and thread-like (straight tip if female, rounded tip if male)
posterior portion – thick and fleshy
Anterior part embeds into mucosa of large intestine
egg: barrel-shaped, bipolar plugs, unsegmented ovum
oral fecal route
Trichuris trichiuria: clinical features
usually asymptomatic
anemia, malnutrition
mucus diarrhea, chronic dysentery, abd pain, rectal prolapse (young children)
Trichuris trichiuria: lab diagnosis, prevention and treatment
barrel shaped egg, bipolar plug in stool
adult worms in mucosa
prevention: good hygiene
Mebendazole, Albendazole, Ivermectin
Ascaris lumbricoides
- small intestine
- has three prominent lips
- male is bigger than female
Ascaris lumbricoides: larval migration phase
infiltration of eosinophils and macrophages
loeffler’s syndrome: low grade fever, cough, wheezing, dyspnea, transient eosinophilia, lung infiltration
Ascaris lumbricoides: intestinal phase of adult worms
usually asymptomatic, can cause intestinal obstruction/ malnutrition
Ectopic migration to
- blocks pancreatic ducts : pancreatitis
- liver parenchyma -> liver abscess
- up oesophagus, leaves through mouth/ nose
- obstructs appendix –> appendicitis
- perforates intestines –> peritonitis
Ascaris lumbricoides: lab diagnosis, prevention and treatment
detection of eggs in stool
adult worms in feces/ vomit
larvae in sputum/ gastric aspirate
prevention: good hygiene
treatment: pyrantel pamoate
Enterobius vermicularis:
pinworm –> enterobiasis
Adults usually in cecum and appendix
egg: D shaped, flattened on one side
oral fecal route
Enterobius vermicularis: patho, clinical features
eggs: sticky and sticks to perianal skin
ectopic migration:
1. vulva and vagina : irritation and inflammation
2. uterus and fallopian tubes: cervicitis and chronic salpinitis
retroinfection: eggs laid on perianal skin hatch into infective stage larva–> migrates through anus, develops into worms at colon
Enterobius vermicularis: lab diagnosis and treatment
cellophane tape/ scotch tape method
Mebendazole, Albendazole, Piperazine, Pyrantel
Schistosomiasis patho and clinical features
snail fever, water borne
Schistosoma japonicum, mansoni, haematobium
- penetrates skin
- local cercarial dermatitis (swimmer’s itch)
- itching and petechial lesions - acute schistosomiasis (Katayama fever)
- hypersensitivity reaction (fever, cough, abd pain, diarrhea, hepatosplenomegaly, eosinophilia) - oviposition of S. haematobium
- painless terminal haematuria,
could lead to squamous cell carcinoma of bladder
eggs: carried to liver –> hepatosplenomegaly, periportal fibrosis, portal hypertension
S. mansoni, S. japonicum eggs
- inflammatory reaction (granulomas, hyperplasia, fibrosis)
Schistosomiasis: lab diagnosis and treatment
eggs in feces/ urine
- praziquantel
Taenia saginata (beef), Taenia solium (pork)
flat segmented worms
adult worms: head (scolex attaches to intestine), neck, chain of segments
T saginata, T solium: patho and clinical features
mostly asymptomatic
- vague abd discomfort, indigestion, nausea, diarrhea, weight loss
- acute intestinal obstruction, acute appendicitis
Cysticercosis
- seizures, muscle/ eye damage
- development of larva (cysticercus cellulosae)
- eggs –> larvae–> migrate to organ/ tissue: subcutaneous tissues, brain, eye
- neurocysticercosis (brain): headache, seizures due to reaction to dead worms
