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Transmission

Transmission. Giardiasis is caused by the ingestion of infective cysts. Modes of transmission : - Person-to-person, Water-borne, and Venereal. Person-to-person transmission is usually associated with poor hygiene and sanitation.

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Transmission

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  1. Transmission Giardiasis is caused by the ingestion of infective cysts. Modes of transmission : - • Person-to-person, • Water-borne, and • Venereal. • Person-to-person transmission is usually associated with poor hygiene and sanitation. • Water-borne transmission is common with the ingestion of unfiltered water (contaminated). • Venereal transmission happens through fecal-oral contamination. • Food-borne epidemics of Giardia developed through the contamination of food by infected food-handlers. Incubation Period • 1 to 2 weeks (average 7 days) after an individual becomes infected.

  2. Morphology Cysts • cysts are non-motile and egg-shaped. • cysts are the infective form of the parasite and each cyst gives rise to two trophozoites. TrophozoitesTrophozoites are motile and non-infectious because they cannot survive long outside the host body.

  3. Life Cycle of Giardia • Step 1 in life cycle: • The life cycle of Giardia alternates between the cyst and the trophozoite forms, and both forms are found in faeces. • Cysts are more often found in non-diarrheal feces, and they are the infectious stage of the parasite. • The cysts are hardy and they can persist for several months in cold, moist environment. • Step 2 in life cycle: • Infection begins when a new host ingests cysts in contaminated food, water, fomites or fecal-orally. • Mature cysts are able to survive the acidic environment of the stomach and migrate to the small intestine of the host.

  4. Cont .. • Step 3 in life cycle: • Exposure to stomach acid triggers a process called excystation, during which trophozoites are released from cysts. • Each cyst gives rise to two binuclear trophozoites.

  5. Cont.. • Step 4 in life cycle: • Trophozoites are the disease causing stage of the parasite and they colonize the small intestine by attaching to the intestinal mucosa using the ventral sucking disks. • Trophozoites are largely noninvasive and do not invade other organs; however, at times they might penetrate down into the secretary tubules of the mucosa and be found in gallbladder and the biliary drainage.

  6. Cont .. • Step 5 in life cycle: • As trophozoites migrate toward the large intestine, they retreat into the cyst form in a process called encystation. • Bile salts and intestinal mucous were found to enhance trophozoite multiplication and encystations. • Trophozoites, if excreted in feces, cannot survive long in the environment and are therefore noninfectious. • The cysts in excrements will quickly become infectious and will begin a new cycle of infection if ingested

  7. Symptoms • Gastrointestinal :- • an sudden onset of abdominal cramps, explosive, watery diarrhea, vomiting, and fever which may last for 3-4 days. • In both the acute and insidious onsets of symptoms, stools become greasy but do not contain blood or pus. • Watery diarrhea may cycle with soft stools and constipation. • Upper GI symptoms including : - • nausea, early satiety, substernal burning, egg-smelling halitosis.

  8. Constitutional: • anorexia, malaise, and fatigue. • Weight loss affects more than 50% of patients. • Adults with long lasting malabsorption syndrome and children with failure to thrive Physical: • Abdominal examination : - nonspecific tenderness • Rectal examination :- heme-negative stools and • Severe cases, evidence of dehydration.

  9. Lab Diagnosis • Diagnostic Tests • Stool examination • 3 stools taken at 2-day intervals are examined for ova and parasites. • The cysts are detected 50-70% of the time in the first stool specimen examined, and 90% of the time the cysts are detected after 3 stool specimen examinations. • Trophozoites disintegrate rapidly outside of the body but may be found in fresh, watery stools. • Cysts are found in soft and (semi)formed stools. • Cyst passage may fall behind the onset of symptoms by a week • Trichrome stain is useful for finding the cysts and trophozoites.

  10. Stool antigen detection • Immunofluorescent antibody (IFA) assay or • Enzyme-linked immunosorbent assay (ELISA) against cyst or trophozoite antigens. • These have a sensitivity of 85-98% and a specificity of 90-100%. Stool culture • Not useful for diagnosing giardiasis because the organism cannot be grown from patient samples

  11. String test • String test (entero-test) involves a gelatin capsule connected to a weighted nylon string. • Patient tapes one end of the string to his cheek and then swallows the capsule. • After the gelatin is dissolved in the stomach, the weight carries the string into the duodenum. • The string is left there for 4-6 hours or overnight • After removal, the string is examined for bilious staining, which identifies successful passage into the duodenum. • The mucus from the string is examined for trophozoites in iodine or saline.

  12. Treatment First line of treatment • Metronidazole (Flagyl) • Adult dosage: 250 mg three times a day for 5 days. • Pediatric dosage: 15 mg per kilogram of body weight per dose, 3 times per day, for 5 days. • Side effects: • Include unpleasant metallic taste • GI discomfort such as vomiting, nausea, diarrhea, abdominal cramps, • Contraindication: • Avoid alcohol while taking metronidazole. • Metronidazole causes severe vomiting, headache, and GI discomfort by inhibiting aldehyde dehydrogenase, which breaks down alcohol.

  13. Tinidazole - Adult dosage: 2 g once • Pediatric dosage: 50 mg per kilogram of body weight once (max. 2 g) • Side effects: • Side effects similar to metronidazole • Common side effects include bitter taste, vertigo, and GI discomfort. • The drug should be taken with food to minimize side effects.

  14. Alternative Treatment • Paramomycin • Adult dosage: • 25-35 mg per kilogram of body weight per dose, 3 doses per day for 7 days • Pediatric dosage: • 25-35 mg per kilogram of body weight per dose, 3 doses per day for 7 days • Side effects: • ototoxicity and nephrotoxicity with systemic administration • Contraindication: • Patients with impaired kidney function should use paramomycin with caution

  15. Albendazole (Albenza) • Adult dosage: 400 mg once a day for 5 days • Pediatric dosage: 15 mg per kilogram of body weight per day for 5 to 7 days (max. 400 mg) Mebendazole (Vermox) • Adult dosage: 200-400 mg per day for 5 to 10 days • Side effects for Albendazole and Mebendazole: • common side effects include anorexia and constipation.

  16. Treating Drug-Resistant Patients • developed resistance to all of the common anti-giardial drugs, such as metronidazole, and albendazole. • treating with the original drug for a longer period of time or at higher doses; • using a drug from a different class to treat the resistant infection • using a combination of different classes of drugs, such as metronidazole-albendazole and metronidazole-quinacrine.

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