Parasitic Infestations Basim Asmar, M.D. Wayne State University School of Medicine Children’s Hospital of Michigan Divi

1. Parasitic Infestations Basim Asmar, M.D. Wayne State University School of Medicine Children’s Hospital of Michigan Division of Infectious Diseases

2. Parasitic Infestations Parasitic diseases: Caused by protozoa or helminths Parasitic protozoa & helminths: Referred to as animal parasites to distinguish them from bacteria, fungi & viruses Endoparasitic protozoa: A diverse group of >10,000 eukayotic unicellular animals Endoparasitic helminths of humans: Two phyla – (1) Platyheminths (flatworms) (2) Nematoda (round-worms)

3. Intestinal Parasitic InfestationsProtozoa Giardia lamblia (Giardiasis) • A flagellated protozoan • Infects the duodenum and upper part of the small intestine • Infection is often asymptometic but can be associated with a variety of intestinal manifestations

4. Giardia lamblia

5. Giardia lamblia

6. Giardia lamblia - Life Cycle • Infection occurs by the ingestion of cysts in contaminated water or food. • In the small intestine, excystation releases trophozoites that multiply by longitudinal binary fission. • The trophozoites remain in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk. • Encystation occurs when the parasites transit toward the colon, and cysts are the stage found in normal (non diarrheal) feces. • The cysts are hardy, can survive several months in cold water, and are responsible for transmission. • Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. • While animals are infected with Giardia, their importance as a reservoir is unclear.

7. Giardia lamblia

8. In wet mounts, cysts show the typical ovoid ellipsoid shape measuring from 8-19 mm (range 11-14 mm)

9. Giardia trophozoite (Trichrome stain x 1000)

10. Giardia lamblia • 10-25 cysts sufficient to initiate infection • Colonization  morphologic damage to intestinal epihelial cells and brush border may result in normal microvilli or subtotal atrophy • Disaccharidase deficiencies (usually lactase) • Malabsorption affecting protein & fat-soluble vitamines • Decreased intestinal absorption of antibiotics

11. Giardia lamblia • Cysts viable for 3 months in water at 4o C • Freezing does not eliminate infectivity completely • Heating, drying and sea water are likely to do so • Human milk is lethal to Giardia trophozoites through the action of fatty acids • Duodenal fluid is also lethal to Giardia • Survival in hostile environment is attributed to the protective effect of human mucus

12. Giardia lamblia • Anti-Giardia IgG is found in >80% of patients during symptomatic infection • Anti-Giardia IgG tends to persist, thus limiting usefulness in distinguishing current from past infection • Serum anti-Giardia IgM antibodies increase early in infection and decrease rapidly after 2-3 weeks • Human milk protection against Giardia correlates with anti-Giardia serum IgA

13. GiardiasisEpidemiology • Occurs worldwide • Age-specific prevalence: • Highest in children 0-5 years • Followed by 31-40 years old • Most cases reported in late summer and early fall • Transmission is common in certain high risk populations: • Children and employees in DCC’s • Consumers of contaminated water • Travelers to certain areas of the world • Those exposed to domestic and wild animals (dogs, cats, cattle deer, and beaver)

14. GiardiasisEpidemiology • Major reservoir/vehicle for spread: Water contaminated with cysts • Major risk for hikers: Drinking untreated mountain stream water • Person-to-person spread: Frequent in areas of low hygienic standards/crowding • Person-to-person spread occurs in: • Childcare centers • Families of children with diarrhea

15. Giardiasis Clinical Manifestations SymptomPercent Diarrhea 64-100 Malaise. Weakness 72-97 Abdominal distension 42-97 Flatulance 35-97 Abdominal cramps 44-81 Nausea 14-79 Foul-smelling, greasy stools 15-79 Anorexia 41-73 Weight loss 53-73 Vomiting 14-35 Fever 0-28 Constipation 0-17

16. Giardiasis Clinical Manifestations • Symptoms vary with age • Profuse watery stools  greasy, foul smelling, buoyant • Blood, mucus & fecal leukocyte are absent • Varying degrees of malabsorption can occur • Abnormal stool patterns can alternate with constipation and normal bowel movements • Infrequent associations: reactive arthritis, urticaria

17. Giardiasis Clinical Manifestations • Asymptomatic carriers in USA: 3%-7% (up to 20% in southern regions) • Prevalence studies in DCC children <36 months: 21% • Asymptomatic infection is well tolerated • Testing of case contacts/treatment of asymptomatically infected individuals is NOT indicated routinely • Humoral immunodeficienies (hypo-, agammaglobulinemia) predispose to chronic symptomatic giardiasis

18. GiardiasisDiagnosis Definitive Diagnosis: Detection of trophzoites, cysts or antigens in stool or duodenalfluid • Stool specimens: Examined within 1 hour after being passed or should be stored in vials containing polyvinyl alcohol (PVA) or 10% formalin • Trophozoites are more likely to be found in unformed stools (rapid transit time) • Cysts, but not trophozoites, are stable outside the GI tract • Duodenal Specimens: Aspirate/Biopsy  Trophozoites can be seen on direct wet mount

19. Giardiasis Diagnosis Microscopy: Diagnostic: 70% of patients with single exam 85% with a second exam Antigen Detection: (Polyclonal antisera or monoclonal antibodies) EIA: 87%-100% sensitivity / 100% specificity DFA: 100% sensitivity/specificity Giardiasis is NOT associated with eosinophilia

20. Giardiasis Treatment Oral Antimicrobial Therapy for Giardiasis AgentPediatric Dose Adult Dose Metronidazole 15 mg/k/d divided in 3 doses X 5d 250 mg tid X 5d (Flagyl) Furazolidone 6 mg/k/d divided in 3-4 doses X 10d 100 mg tid X 10d (Furoxone) Albendazole 400 mg/day X 5d 400 mg/day X 5d (Albenza) Quinacrine 6 mg/k/d divided in 3 doses X 5d 100 mg tid X 5d (Atabrine) Nitazoxanide 12-47 mo: 100 mg bid X 3d N/A (Alinia) 4-11 yrs: 200 mg bid X 3d (100 mg/5 ml)

21. Giardiasis Prevention • Strict hand washing after contact with feces • Purification of public water supplies • Chlorination • Sedimentation • Filtration • Avoid swallowing: recreational water, water from shallow wells, lakes, rivers, streams, ponds & springs • Travelers to endemic areas: avoid drinking untreated water & uncooked foods that have been grown, washed or prepared in potentially contaminated water • Purification of drinking water: Heating (55o C X 5 min) or use filter (pore size < 1 um)

22. Cryptosporidium parvum • Human disease caused by Cryptosporidiun wasfirst described in 1976 • The AIDS epidemic fueled interest in cryptosporidiosis • Improved detection of oocysts in feces  infection is common cause of diarrhea in immunocompetent & immunocompromised hosts • 2- to 6-um coccidian parasite that infects the epithelial cells lining the digestive and respiratory tract of vertebrates (fish, reptiles, and mamals, & humans)

23. Life cycle of Cryptosporidium parvum • Sporulated oocysts, containing 4 sporozoites, areexcreted by the infected host through feces (1). Transmission of Cryptosporidium parvum occurs mainly through contact with contaminated water (e.g., drinking or recreational water) (2). Occasionally food sources, such as chicken salad, may serve as vehicles for transmission. Many outbreaks in the United States have occurred in waterparks, community swimming pools, and day care centers. • Zoonotic and anthroponotic transmission of C. parvum occur through exposure to infected animals or exposure to water contaminated by feces of infected animals . • Following ingestion (and possibly inhalation) by a suitable host (3), excystation occurs (a). The sporozoites are released and parasitize epithelial cells (b,c) of the gastrointestinal tract or other tissues such as the respiratory tract. In these cells, the parasites undergo asexual multiplication (schizogony or merogony) (d, e, f) and then sexual multiplication (gametogony) producing microgamonts (male) (g) and macrogamonts (female) (h). Upon fertilization of the macrogamonts by the microgametes (i), oocysts (j, k) develop that sporulate in the infected host. Two different types of oocysts are produced, the thick-walled, which is commonly excreted from the host (j), and the thin-walled oocyst (k), which is primarily involved in autoinfection. • Oocysts are infective upon excretion, thus permitting direct& immediate fecal-oral transmission.

24. Cryptosporidium parvum

25. Cryptosporidium parvumEpidemiology Crptosporidiosis is associated with diarrheal illness worldwide Transmission to humans: • Close association with infected animals (calves, rodents, puppies, kittens) • Person-to-person (DCC, Traveler’s diarrhea) • Environmentally contaminated water ~130 oocysts can cause infection in immunocompetent

27. Cryptosporidium parvumEpidemiology • Outbreaks have been associated with contaminated community water supplies • Waterborne outbreak in Milwaukee, WI (1985): 403,000 cases of diarrhea 4400 were hospitalized Total cost: $96.2 million • Swimming pool water & water from decorative fountains have been linked with outbreaks of crptosporodiosis

28. CryptosporidiosisEpidemiology • More prevalent in underdeveloped countries & in children <2 years of age • Most cases are not recognized • Infection rates surveys in selected populations: • Developed countries: 0.6%-20% • Underdeveloped countries: up to 32% • Difference is due to: • Poor sanitation, lack of clean water, crowded living conditions, close association with animals

29. CryptosporidiosisClinical Manifestations • Incubation period: 2-14 days • Diarrhea: Profuse watery diarrhea + mucus Rarely contains WBC’s or RBC’s • Crampy abdominal pain, nausea, vomiting (50%) • Fever is uncommon • Infection may be asymptomtic, self-limited or protracted

30. CryptosporidiosisClinical Manifestations • Severity is linked with immunosuppression • Most immunocompetent hosts: self-limited illness (10-14 days) • Immunocompromised (HIV, malignancy): prolonged debilitating disease • Oocysts shedding: up to 2 weeks after clinical improvement • Biliary tract disease may occur in immunocompromised hosts (15%): • Fever • RUQ pain • N,V,D • Jaundice & elevated LFT’s can occur

31. CryptosporidiosisLaboratory Diagnosis • Identification of oocysts in • (1) stools or • (2) along epithelial surface of biopsy tissue • Highest concentration in jejunum • Histology: villous atrophy, blunting, epithelial flattening • Stool specimens for oocysts identification: • Put in fixative (to prevent infection in lab workers) • 3 specimens in immunocompetent • 2 specimens in immunocompromised • Auramine & rhodamine stain – most sensitive/expensive • Acid fast stain – commonly used • Not detected by routine O & P

32. Cryptosporidiosis Cryptosporidia are usually identified in stool specimens by a modified acid-fast stain. The left panel shows numerous red staining oocysts. In more difficult cases, a biopsy of small bowel or colon leads to the diagnosis. In the right panel, numerous basophilic cryptosporidia stud the surface of the enterocytes. Note the lack of inflammation.

33. Cryptosporidiosis – Small spherical organisms (red arrow) attached to the brush border of absorptive intestinal epithelial cells

34. Oocysts of Cryptosporidiumvisualized with Acid-fast stain

35. Oocysts of Cryptosporidium parvum

36. CryptosporidiosisTreatment • In most immunocompetent: Self-limited; no therapy except adequate hydration • In severe cases/immunocompromised hosts: A variety of agents have been used without consistent results • Until recently the mainstay of treatment was supportive care • Newly effective/FDA-approved agent: Nitazoxanide (Alinia): 12-47 mo: 100 mg bid X 3d 4-11 yrs: 200 mg bid X 3d (Concentration: 100 mg/5 ml)

37. CryptosporidiosisPrevention • Hand washing: prevent person-to-person transmission • Enteric precautions for hospitalized patients • Cohort infected patients in hospital • Immunocompromised hosts should take special precautions around animals • Avoid swallowing recreational water • Avoid drinking water from shallow wells, lakes, rivers, streams, ponds and springs

39. Amebiasis Entamoeba histolytica • Pseudopod-forming, non-flagellated protzoa • Most invasive parasite of the Entamoeba group • Only member that causes: Amebic colitis & liver abscess • Life Cycle consists of: (1) Infectious cyst (2) Invasive trophzoite Trophozoites adhere to colonic mucin and epithelial cells  kill host epithelial & immune cells  tissue destruction

40. Entamoeba histolytica trophozoite Entamoeba histolytica mature cyst Amebiasis

41. Amebiasis Cysts are passed in feces(1). Infection by Entamoeba histolytica occurs by ingestion of mature cysts in fecally contaminated food, water, or hands (2). Excystation occurs in the small intestine(3)  trophozoites released  migrate to the large intestine (4). Trophozoites multiply by binary fission and produce cysts (5) passed in the feces.  Cysts (protected by their cell walls) can survive days to weeks in the external environment and are responsible for transmission.  In many cases, trophozoites remain confined to the intestinal lumen (noninvasive infection) of individuals who are asymptomatic carriers, passing cysts in their stool. In some patients trophozoites invade the intestinal mucosa (intestinal disease), or, through the bloodstream, extraintestinal sites such as the liver, brain, and lungs (extraintestinal disease), with resultant pathologic manifestations. Invasive and noninvasive forms represent two separate species (E. histolytica & E. dispar respectively), however not all persons infected with E. histolytica will have invasive disease.  These two species are morphologically indistinguishable. Transmission can also occur through fecal exposure during sexual contact (cysts, & also trophozoites could prove infective).

42. Trophozoites of Entamoeba histolytica (Trichrome stain).Two diagnostic characteristics:Two of the trophozoites have ingested erythrocytes, and the nuclei have typically a small, centrally located karyosome, as well as thin, uniform peripheral chromatin.

43. Entamoeba histolyticaEpidemiology • Greatest morbidity/mortality in the developing countries of Central & South America, Africa, and India • Disease more severe in: The very young Elderly Pregnant women • Worldwide: 40-50 million symptomatic infections/year 100,000 deaths annually • In Dhaka, Bangladesh, 50% of children have serologic evidence of E. histolytica infection by 5 years • Groups at increased risk of amebiasis in developed nations: • Immigrants from endemic areas • Long-term visitors to endemic areas • Institutionalized individuals

44. Entamoeba histolyticaClinical Manifestations Amebic colitis Sign or Symptom% of Patients Affected Symptoms > 1 wk Most patients Diarrhea 94-100 Dysentery 94-100 Abdominal pain 12-80 Weight loss 44 Fever >38oC 10 Heme (+) stool 100 Immigrant from or traveler to endemic area >50 Prevalence (male/female) 50/50

45. Entamoeba histolyticaClinical Manifestations Amebic colitis Patients with chronic, non-dysenteric intestinal amebiasis may complain for months to years of abdominal pain, flatulence, intermittent diarrhea, mucus in the stools, and weight loss Chronic non-dysenteric intestinal amebiasis has been mistakinly diagnosed as ulcerative colitis

46. Amebic Colitis:Severe dysentery with multiple ulcers in the large bowel, and a bloody diarrhea

47. Entamoeba histolytica trophozoites in section of intestine (H&E) 

48. Entamoeba histolyticaClinical Manifestations Acute Fulminant or NecrotizingColitis • Unusual (about 0.5% of cases) • A complication that occurs more frequently in patients inappropriately treated with corticosteroid • Abdominal pain, distension, and rebound tenderness are present in most patients • Indications for surgery: • Failure of response to anti-amebic drugs after intestinal perforation/abscess formation • Persistence of abdominal distention after institution of anti-amebic Rx • Toxic megacolon

49. Histopathology of a typical flask-shaped ulcer of intestinal amebiasis

50. Entamoeba histolyticaClinical Manifestations Ameboma • Segmented mass of granulation tissue in the cecum or ascending colon • Occurs in 0.5% to 1.5% of patients with intestinal amebiasis • Tender palpable abdominal mass • Concuurent amebic dysentery present in 2/3 of patients • “Apple-core” lesions on barium enema study • Lesions resolve with anti-amebic chemotherapy • Intestinal constriction occurs in the colon in <1% of patients