MICR 420

Emerging and Re-EmergingInfectious Diseases

Lecture 9:Cryptosporidium, Schistosoma

Dr. Nancy McQueen & Dr. Edith Porter

Cryptosporidium

Cryptosporidium Protozoa

Apicomplexa Sporozoa

Currently 20 species recognized

Reservoir Mammals, birds, reptiles

Waterborne infection Affects primarily

intestinal tract

Oocysts Sporozoites

Water

Sporozoites

Invade intestinal epithelial cell

Life Cycle of Cryptosporidium

http://www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis.htm

Cryptosporidiosis: Pathogenesis

Formation of a unique intracellular compartment in the apical region of the host cell

Involves rearrangement of the host cell cytoskeleton in intestinal epithelial cell

Incorporates host cell actin and alpha-actinin into a host-parasite junctional complex

Cryptosporidiosis: Disease Infectious dose ~ 10 oocysts

Autoinfection Incubation time 2 – 10 days Massive diarrhea

Malnourished children and immunocompromised Up to 25 bowel movements

Millions of oocysts are shed Up to 17 liters fluid loss/day Accompanied by fever

Last about for 1-2 weeks Life threatening for immunocomprised patients

Some may not develop symptoms Genetic association with certain MHC II types

Cryptosporidiosis: Diagnosis

Modified acid fast stain from stool sample (Kinyoun)

ELISA testing for Cryptosporidium antigen in stool samples

IFA Molecular (PCR)

60-kDa glycoprotein gene (gp60)

http://www.stanford.edu/class/humbio103/ParaSites2006/Cryptosporidiosis/Images/acid-fast%20crypto%20(2).jpg

5 m

http://www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis.htm

Cryptosporidiosis: Therapy

Nitazoxanide in otherwise healthy patients Nitrothiazole benzamide Blocks anaerobic metabolism Inhibition of the ferredoxine reductase Is effective if immune system is functional Also used in worm infections, some anaerobic

bacterial infections Symptomatic Improve immune system

Anti-retroviral therapy for AIDS patients

Cryptosporidiosis: Prevention

Problem: resistance to common disinfectants Requires special water treatment in municipal

systems Routine chlorine does not inactivate oocysts Small size allows penetration through routine filter

Home filtration Reverse osmosis 1 micron filters

Threats by Cryptosporidium 1993 Milwaukee outbreak

Contamination of the municipal water system C. parvum

100 deaths and 400,000 illnesses Critical Biological Agent for Public Health

Preparedness Category B Some potential for large-scale dissemination, but generally

cause less-severe illness than those in Category A Could be used to contaminate food or water sources, and

many of them are relatively easy to obtain. Difficult to detect, high dose in fecal movements and

low infectious dose

The worms crawls in,

the worms crawl out,

in your belly,

and out your snout.ANONYMOUS

Overview

Schistosoma Helminths Morphology Life cycles Vector Pathogenesis Diseases Diagnosis Therapy Prevention Threats

Helminths: Classification

Phylum: Platyhelminthes (flatworms) Class: Cestodes

(tapeworms) Class: Trematodes

(flukes) E.g., Schistosoma

Phylum: Nematodes (roundworms) E.g., Filaria

Animalia Multicellular Organs and biological

systems* Circulatory Nervous Reproductive

Hermaphrodites Dioecious

Digestive Excretory

* Depending on species some systems may be lacking or rudimentary

Trematodes Flukes Oral sucker: food uptake

Incomplete digestive tract Ventral Sucker: Attachment Mostly hermaphroditic

(monoecious)

"Copyright Dennis Kunkel Microscopy, Inc. (www.denniskunkel.com)"

Schistosoma

Schistosoma japonicum Schistosoma mansoni Schistosoma haematobium

Adults Females size 7 to 20 mm Males slightly smaller

Schistosoma: Life Cycle (1) Infection from contaminated fresh

water in which certain types of snails that carry schistosomes are living

Schistosoma can penetrate the skin

Within several weeks, worms grow inside the blood vessels of the body and produce eggs.

Some of these eggs travel to the bladder or intestines and are passed in the urine or stool

Schistosoma eggs gain access to fresh water when infected people urinate or defecate in the water. Eggs

Miracidia

Sporocysts

Cercariae

Adults

Snail

Human

Schistosoma: Life Cycle (2)

Developmental Stages of Schistosoma

Cercariapenetrating skin

Adult male and femaleworms

Egg Miracidia

Borowski et al. 2008, Trends in Parasitology Vol.24 No.11

The Apical Complex (ac) of Cryptosporidia

Secretory organelles multiple micronemes (mn)

Selection of host cells Gliding motility

single rhoptry (r) Parasitrophus vacuole

formation dense granules (dg)

Modification of host cell

Zoite pellicle (p) Cryptosporidium receptors

involved in host-cell invasion

Borowski et al. 2008, Trends in Parasitology Vol.24 No.11

(a) Ingested oocysts adhere to ileal mucus via surface lectins.(b) Oocysts excyst and release four sporozoites. (c) Sporozoites express mucin-like surface receptors, which mediate attachment to the ileal mucus lining. (d) Sporozoites discharge enzymes to degrade intestinal mucus. The penetration of mucus is thus

facilitated. (e) Sporozoites penetrate the mucus lining and establish host-cell contact via specific receptor–ligand

interactions.

Sporozoites of C. parvum have to penetrate intestinal mucus to establish host-cell contact

Borowski et al. 2008, Trends in Parasitology Vol.24 No.11

Schistosoma and Affected Organs

S. japonicum

S. mansoni

S. haematobium

superior mesenteric veins of small intestine

superior mesenteric veins draining of large intestine

venous plexus of bladder

Schistosoma: Virulence Factors

Tegument Unique double membrane structure dynamic host-interactive layer involved in nutrition, immune evasion

and modulation, excretion, osmoregulation, sensory reception and signal transduction

single syncytium that covers the entire body Soluble hypersensitivity antigen released by miracidia within

the eggs. Local inflammation

Glycan rich surface Antioxidant enzymes Elastase-like IgE protease Excretory/secretory (ES) molecules from cercariae down-

regulate the host's immune response Bind host defense molecules on their surface

S. mansoni eggs in liver

Schistosoma: Diseases Bilharzia Often asymptomatic Acute schistosomiasis (Katayama's fever)

May occur weeks after the initial infection S. mansoni and S. japonicum Fever, cough, abdominal pain, diarrhea, hepatospenomegaly, and

eosinophilia Occasionally central nervous system lesions occur

granulomatous lesions around ectopic eggs Brain, spinal cord

Chronic infection Granulomatous reactions and fibrosis in the affected organs Colonic polyposis with bloody diarrhea (Schistosoma mansoni mostly) Portal hypertension with hematemesis and splenomegaly (S. mansoni, S.

japonicum) Cystitis and ureteritis (S. haematobium) with hematuria, which can progress

to bladder cancer;

Schistosoma and Cancer

General: Chronic inflammation with chronic phagocytes at the

inflammatory site Release reactive oxygen radicals and reactive nitrogen

radicals Chronic inflammation leads to repeated cycles of cell

damage and compensatory cell proliferation Promoting neoplasia

Schistosoma specific Adult schistosomes liberate carcinogenic amines in urine Increased beta-glucuronidase levels originating from

miracidia enclosed in the eggs

Khurana S et al. (2005) Indian J Med Microbiol. 2005 Apr;23(2):74-9.

Squamous Bladder Cancer Induced by Schistosoma

Normal epithelium Squamous bladder cancer

Schistosoma: Diagnosis

Microscopy Antibody detection

ELISA and immunoblot Schistosomal adult microsomal antigen indicative only of schistosome infection at some

time cannot be correlated with clinical status, worm

burden, egg production, or prognosis

Schistosoma: Identification of Eggs

S. mansoni S. japonicum

Spine

S. haematobium

In Feces In Urine

Schistosoma: Therapy

Praziquantel for all species

Schistosoma: Prevention No vaccine Avoid wading, swimming or other fresh-water

contact in endemic countries Avoid untreated piped water coming directly from

canals, lakes, rivers, streams or springs that may contain cercariae

Heating bathing water to 50°C (122°F) for 5 minutes or filtering water with fine-mesh filters

Allow bathing water to stand for 2 days because cercariae rarely remain infective longer than 24 h

Schistosoma: Epidemiology

200 million people infected world wide in over 70 countries

50% endemic among the local population in high infested areas

South America Caribbean Africa Middle East Far East

Depends on species

Schistosoma: Endemic Areas

Threats by Schistosoma

Mainly threat to population in endemic areas and to travelers

Resistance against praziquantel

Resources

The Microbial Challenge, by Krasner, ASM Press, Washington DC, 2002. Brock Biology of Microorganisms, by Madigan and Martinko, Pearson Prentice Hall,

Upper Saddle River, NJ, 11th ed, 2006. Microbiology: An Introduction, by Tortora, Funke and Case; Pearson Prentice Hall;

9th ed, 2007. www.asnom.org/.../nodule_oncho.jpg http://www.icp.ucl.ac.be/~opperd/parasites/images/man.jpg http://www.the-travel-doctor.com/filari9.gif http://www.payer.de/entwicklung/entw2029.gif http://emu.arsusda.gov/typesof/images/onchyo.jpg http://www.denniskunkel.com/product_info.php?products_id=1089 http://www.denniskunkel.com/product_info.php?products_id=592 http://www.cdc.gov/ncidod/dpd/parasites/schistosomiasis/default.htm http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis&obj=schisto.htm http://education.vetmed.vt.edu/curriculum/VM8054/Labs/Lab4/IMAGES/SIMPL

%20COLM%202%20GALL.JPG http://www.pathguy.com/lectures/bladder_cis.jpg http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Schistosomiasis_il.htm Bayne 2009, Molecular & Biochemical Parasitology 165 (2009) 8–18