mod 4

• Giardia lamblia
• Endemic in tropics and subtropics with poor sanitation
• Visitors to such areas develop traveler's diarrhea
• Global distribution
• Exists in 2 forms: Trophozoite and Cyst
• Habitat: lives in the duodenum and upper jejunum
• Trophozoite:

  • Pyriform in shape, rounded anteriorly and pointed posteriorly
  • Measures 15 μm × 9 μm
  • Dorsally convex, ventrally has a concave sucking disc for attachment to intestinal mucosa
  • Bilaterally symmetrical, possesses 2 nuclei, 4 pairs of flagella, 1 pair of axostyles, and 2 parabasal or median bodies
• Cyst:

  • Oval in shape, measuring 12 μm × 8 μm
  • A young cyst contains 2 nuclei, a mature cyst contains 4 nuclei
  • The axostyle lies diagonally
  • Remnants of flagella may be seen in the cyst
• Life Cycle:

  • Cysts passed out in stool of infected human
  • Infective cysts ingested
  • Cyst excysts to release trophozoite in small intestine
  • Trophozoites multiply by binary fission
  • Trophozoite encysts to become cyst passed out in stool
  • Trophozoites passed in loose stools
  • Giardia completes its life cycle in 1 host
  • Infective stage is the mature cyst
  • Human acquires infection by ingestion of cysts in contaminated water and food
  • Direct person to person transmission may occur
• Pathogenesis and Clinical Features:

  • Trophozoite adheres to intestinal epithelium causing stunting and shortening of villi
  • Patients usually asymptomatic, but may experience diarrhea, fat malabsorption, epigastric pain, and flatulence
  • Stool contains excess mucus and fat
  • Children may develop chronic diarrhea, malabsorption of fat and vitamin A, and weight loss
  • Incubation period is about 2 weeks
• Diagnosis:

  • Microscopic examination for cysts and trophozoites in stools
  • Use of concentration techniques like formal ether
  • Enterotest (String test) for obtaining duodenal specimen
  • Molecular diagnosis with PCR on stool specimen
• Treatment:

  • Metronidazole or tinidazole is the drug of choice
  • Paromomycin for symptomatic pregnant women
• Prevention and Control:

  • Proper fecal disposal
  • Personal hygiene
  • Boiling and filtration of drinking water
  • Washing fruits and vegetables before eating
  • Health education
• Trichomonas vaginalis
• Distributed worldwide
• Habitat: In females, mainly in vagina and cervix; in males, mainly in anterior urethra
• Exists only in trophozoite stage
• Trophozoite:

  • Pear-shaped or ovoid, measures 10-30 μm in length and 5-10 μm in breadth
  • Has 4 anterior flagella and a fifth along the undulating membrane
  • Prominent axostyle runs throughout the body and projects posteriorly
• Life Cycle:

  • Trophozoites live in the vagina, cervix, urethra, and urinary bladder
  • Multiply by longitudinal binary fission
  • Transmission is direct person to person, often sexually
  • Babies may acquire infection during birth
  • Fomites like towels implicated in transmission
• Pathogenesis and Clinical Features:

  • Disrupts glycogen levels and lowers pH of vaginal fluid
  • Does not invade vaginal mucosa
  • Infection ranges from mild irritation to severe inflammation
  • Often asymptomatic, but may cause urethritis, epididymitis, prostatitis, itching, discharge, dysuria, and more
• Diagnosis:

  • Microscopic examination of vaginal or urethral discharge for characteristic motility
  • Culture in Johnson’s and Trussel’s medium
  • Molecular diagnosis with PCR on clinical specimens
• Other Supportive Tests:

  • Raised vaginal pH
  • Positive whiff test
• Treatment:

  • Metronidazole or tinidazole
• Prevention and Control:

  • Personal hygiene
  • Boiling and filtration of drinking water
  • Washing fruits and vegetables before eating
• In bacterial vaginosis, the vaginal pH is raised
• In vaginal candidiasis, the vaginal pH is not raised
• Positive whiff test:

  • Fishy odor is accentuated when a drop of 10% KOH is added to vaginal discharge due to production of amine
  • The test is positive in more than 75% of cases
  • It is also positive in bacterial vaginosis
• Excess of polymorphonuclear neutrophils on wet mount is seen in more than 75% of cases
• Treatment:

  • Treatment of both sexual partners is recommended
  • Metronidazole is the drug of choice (250 mg 3 times daily for 10 days)
  • In pregnancy, metronidazole is safe to be given in the second and third trimesters
• Prevention and Control:

  1. Treatment of sexual partner

  2. Patients should be advised to abstain from sexual intercourse until they and their partners have completed treatment and follow-up