Parasitic Infections (1 of 14) 1 Patient presents w/ signs & symptoms suggestive of GI parasitic infection 2 DIAGNOSIS No ALTERNATIVE Is a GI parasitic infection DIAGNOSIS confi rmed? Yes Protozoal or helminthic infection? Protozoal Infection Helminthic Infection A Rehydration & nutrition B Prevention PHARMACOLOGICAL PHARMACOLOGICAL THERAPY FOR THERAPY FOR PROTOZOAL HELMINTHIC INFECTIONS INFECTIONS ©See page 3 MIMSSee page 3 B1 © MIMS 2019 Parasitic Infections (2 of 14) 1 SIGNS & SYMPTOMS OF GI PARASITIC INFECTIONS GI Symptoms • Abdominal pain, diarrhea, dysentery, fl atulence, malabsorption, symptoms of biliary obstruction Nonspecifi c Symptoms • Fever, malaise, fatigue, anorexia, sweating, wt loss, edema & pruritus • Some patients may be asymptomatic PARASITIC INFECTIONS PARASITIC 2 DIAGNOSIS Clinical History • Attempt to elicit a history of possible exposure, especially for helminthic infections, eg eating undercooked meat, source of drinking water, swimming in fresh water where certain parasites may be endemic • Knowledge of the geographic distribution of parasites is helpful in the diagnosis of patients Host Susceptibility Factors in GI Parasitic Infections • Nutritional status • Intercurrent disease • Pregnancy • Immunosuppressive drugs • Presence of a malignancy Physical Exam Findings • Pallor • Hepatomegaly • Ascites • Ileus • Rectal prolapse Lab Tests Microscopic Exam of Stools • Fundamental to the diagnosis of all GI infections - A minimum of 3 stool specimens, examined by trained personnel using a concentration & a permanent stain technique, should be used - e stool exam is used to detect protozoan cysts & trophozoites, helminth ova, proglottids, larvae or adult worms - A fecal sample must be mixed well before examination because eggs are never uniformly distributed in feces Other Lab Tests • e following are other tests that may be used to document a GI parasitic infection: - Duodenal aspirate - Biopsy - String capsule test - Immunofl uorescent antibody test - Enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR) - Cellophane tape test - Barium studies • Anemia & eosinophilia may be seen on the complete blood count (CBC) © MIMS B2 © MIMS 2019 Parasitic Infections (3 of 14) PROTOZOAL INFECTIONS C RECOMMENDED THERAPY FOR PROTOZOAN PARASITES Drug Pathogen PARASITIC INFECTIONS PARASITIC Preferred Agents Alternative Agents Cryptosporidium sp (Cryptosporidiosis) Nitazoxanide or - Paromomycin + Azithromycin Entamoeba histolytica (Amoebiasis) Iodoquinol or Paromomycin Diloxanide furoate or • Asymptomatic cyst passer Etofamide E histolytica (Amoebiasis) Metronidazole or Tinidazole Ornidazole or Secnidazole • Mild-moderate intestinal disease E histolytica (Amoebiasis) Metronidazole or Tinidazole Chloroquine or Secnidazole • Severe intestinal disease or liver abscess Giardia lamblia (Giardiasis) In most immunocompetent patients, giardiasis is self-limiting & does not require treatment. In nonendemic areas, asymptomatic carriers of giardiasis are treated Metronidazole Albendazole, Furazolidone, Nitazoxanide, Ornidazole, Paromomycin, Quinacrine, Secnidazole or Tinidazole HELMINTH INFECTIONS D RECOMMENDED THERAPY FOR HELMINTHS Drug Pathogen Preferred Agents Alternative Agents Cestodes (Tapeworms) Taenia saginata, Taenia solium, Praziquantel Niclosamide Diphyllobothrium caninum, Diphyllobothrium latum Nematodes (Roundworms) Ascaris lumbricoides (Ascariasis) Albendazole, Ivermectin, Levamisole, Piperazine or Mebendazole or Nitazoxanide Pyrantel pamoate Ancylostoma duodenale, Necator Albendazole, Mebendazole or Levamisole americanus (Ancylostomiasis) Pyrantel pamoate (Hookworms) Capillaria © philippinensis (Capillariasis) MIMS Mebendazole Albendazole Not all products are available or approved for above use in all countries. Specifi c prescribing information may be found in the latest MIMS. B3 © MIMS 2019 Parasitic Infections (4 of 14) HELMINTH INFECTIONS D RECOMMENDED THERAPY FOR HELMINTHS (CONT’D) Drug Pathogen PARASITIC INFECTIONS PARASITIC Preferred Agents Alternative Agents Nematodes (Roundworms) Enterobius vermicularis (Pinworm or Albendazole, Mebendazole or Piperazine readworm) Pyrantel pamoate Strongyloides stercoralis Albendazole, Ivermectin, - (Strongyloidiasis) Mebendazole or iabendazole Trichuris trichiura (Whipworm) Mebendazole Albendazole, Ivermectin or Nitazoxanide Trematodes (Flukes) Clonorchis sinensis (Oriental liver fl uke) Albendazole or Praziquantel - Fasciola hepatica (Fascioliasis) Bithionol or Triclabendazole Nitazoxanide Fasciolopsis buski, Heterophyes Praziquantel - heterophyes Metagonimus yokogawai (Intestinal fl ukes) Opisthorchis viverrini (Southeast Asian Albendazole or Praziquantel - liver fl uke) Paragonimus westermani (Lung fl ukes) Praziquantel Bithionol Schistosoma haematobium Praziquantel Metrifonate Schistosoma japonicum Praziquantel - Schistosoma mansoni Praziquantel Oxamniquine FOLLOWUP • Repeat lab exams to document eradication of parasite, if necessary A REHYDRATION & NUTRITION Adequate Hydration & Nutrition • Patients w/ parasitic infections frequently suff er from malabsorption, vomiting & diarrhea, resulting in malnutrition • Ensure that patient’s nutritional & hydration status are maintained at acceptable levels Replacement of Fluid & Electrolyte Losses • Vomiting & diarrhea result in fl uid & electrolyte losses, mainly Na & K Blood Transfusion & Treatment w/ FeSO • ese measures© may be necessary in hookwormMIMS infections which may cause severe anemia Not all products are available or approved for above use in all countries. Specifi c prescribing information may be found in the latest MIMS. B4 © MIMS 2019 Parasitic Infections (5 of 14) B PREVENTION • Health education regarding personal hygiene, routes of transmission & prevention of transmission • Handwashing to interrupt the fecal-oral or urinary-oral route of transmission of many parasites • Good food hygiene eg washing all vegetables & fruits before consumption to interrupt fecal-oral transmission - Kitchen utensils must be washed frequently - Meat & fi sh must be properly cooked • Use of footwear to inhibit the soil-to-skin route of infection PARASITIC INFECTIONS PARASITIC • Targeted chemotherapy may prevent infections, like treating family contacts of a patient w/ certain parasitic infections eg enterobiasis • Proper disposal of sewage & wastewater to avoid contamination of food crops or water supplies by fecal material • Compost of human waste to kill infective forms of parasites C TREATMENT FOR PROTOZOAL INFECTIONS Drugs for Treatment of Amoebiasis Luminal Amoebicides • Eg Diloxanide furoate, Iodoquinol, Paromomycin • ese agents are eff ective in treating organisms in the bowel lumen - May be used in patients w/ asymptomatic E histolytica infection • Recommended for asymptomatic cyst passers - To avoid the risk of developing invasive disease - To prevent secondary spread • When asymptomatic cyst carriage persists after treatment for amoebic dysentery or liver abscess, further treatment w/ a luminal amoebicide is mandatory, otherwise relapse is frequent • Paromomycin - Acts directly on amoeba w/ antibacterial activity against normal & pathogenic organisms in GI tract; binds to 30s ribosomal subunits interfering w/ bacterial protein synthesis - Temporarily eliminates diarrhea in human immunodefi ciency virus (HIV) patients who have cryptosporidiosis - May also be used in treatment of cryptosporidiosis & giardiasis Tissue Amoebicides • Eg Chloroquine & Nitroimidazole derivatives (Metronidazole, Nimorazole, Ornidazole, Secnidazole & Tinidazole) • ese agents are eff ective in treating invasive amoebiasis but are less eff ective in treating organisms in the bowel lumen • Chloroquine binds & inhibits DNA & RNA polymerase; it also raises parasite’s internal pH, restricting its growth • Nitroimidazole derivatives cause damage to parasite DNA helical structure resulting in strand breakage & impaired template function Other Antiprotozoan Drugs • Eg Furazolidone, Nitazoxanide, Quinacrine Furazolidone • Used for the treatment of giardiasis • Furazolidone is as eff ective as Metronidazole in the treatment of giardiasis • Action: Causes damage to intracellular components Nitazoxanide • Action: Inhibits growth of sporozoites & oocysts of Cryptosporidium sp & trophozoites of G lamblia Quinacrine (Mepacrine) • Action: Suggested action is binding to parasite DNA thereby inhibiting RNA transcription & protein translation© MIMS Not all products are available or approved for above use in all countries. Specifi c prescribing information may be found in the latest MIMS. B5 © MIMS 2019 Parasitic Infections (6 of 14) D TREATMENT FOR HELMINTHIC INFECTIONS Anthelminthic Drugs Albendazole • Has an exceptionally broad spectrum of antiparasitic activity • Widely used for intestinal nematode infections • Decreases ATP production in worms Bithionol PARASITIC INFECTIONS PARASITIC • Preferred agent for F hepatica • Release of worm antigens may cause reactions eg urticaria, photosensitivity reactions & GI symptoms Ivermectin • As eff ective as iabendazole against S stercoralis but has fewer untoward eff ects • Action: Causes hyperpolarization of muscle & nerve cells of parasite leading to paralysis Levamisole • Action: Causes muscle paralysis in susceptible worms Mebendazole • Widely used for treatment of intestinal nematodes • Poorly absorbed from the GI tract resulting in a low frequency of side eff ects • Action: Blocks glucose and nutrient uptake irreversibly in susceptible worms Metrifonate • Alternative to Praziquantel in the treatment of S haematobium