Transcript Protozoan Diseases of Lower Digestive System

Hepatitis
• Inflammation of liver
• Autoimmune disease, alcohol/drug abuse,
genetic disorders, viral infection
• Five viruses cause hepatitis
– Hepatitis A virus (HAV); HBV, HCV, HDV, HEV
• HAV
– Infectious hepatitis
• HBV
– Serum hepatitis
• HCV
– Chronic hepatitis
• HDV
– Requires co-infection with HVB
• HEV
– Enteric hepatitis
• Signs and symptoms:
– Jaundice, nausea, vomiting, fatigue, fever, weight loss
• Complications from chronic infection:
– Cirrhosis; liver failure, liver cancer and death
– Most damage is caused by host defenses
• Transmission
– contaminated food or water; fomites and sexual contact
• Treatment
– Supportive care for symptom
– Anti-virals or interferon may help against HVB or HVC
– Passive immunotherapy
• Prevention
– Avoiding exposure by practicing good hygiene and
protected sex or abstinence
– Vaccines are available against HAV and HBV
Protozoal Diseases of GI Tract
• Most significant human pathogens worldwide
• Few are intestinal pathogens
• Transmitted by fecal to oral route
– Fecal contaminated water
– May be zoonotic
Giardiasis
• Causative agent
– Giardia intestinalis
• Flagellated, pear shaped
• Two nuclei
• Exists in two forms
– Feeding trophozoite
– Dormant cyst
» Tough chitin shell
• Signs & Symptoms
– Range from mild to severe
• Indigestion, nausea, vomiting, malnutrition and
weight loss, severe greasy, frothy diarrhea with
“rotten egg” odor and excess gas (H2S)
– Symptoms usually disappear within 4 weeks
• Some cases become chronic
• Animals tend to be asymptomatic reservoirs
– Cyst infective stage
• Resists stomach acid
• Two trophozoits per cyst
– Trophozoits attach to epithelium of small intestine with
adhesive disk
– In severe cases, may cover entire intestinal surface
• Epidemiology
– Transmission usually fecal-oral route
– May be zoonotic
• Beavers, raccoons, muskrats, dogs, cats
– Single stool can carry 300 million cysts
• Cysts can survive in cold water up to 2 months
• Chlorination often ineffective against cysts
– Diagnosed by cysts or trophozoites in stool
• Prevention
– Filtration or boiling of water
– Good hygiene practices
– Sanitary disposal of feces
– Safe sex
• Treatment
– Fluid and electrolyte replacement
– Metronidazole or quinocrine
Cryptosporidiosis
• Causative agent
– Cryptosporidium parvum
• Multiplies cells of small
intestine
• Apicomplexan
• Exists in two forms
– Acid fast oocyst
– Sporozoite
• Signs & Symptoms
– Fever, headache, loss of appetite, nausea,
abdominal cramps and profuse watery diarrhea
– Can last for months
– May be life threatening in immunocompromised
individuals
• Hepatatis, pancreatitis
– Oocyst releases 4 bannana shaped sporozoites
into small intestine
– Sporozoites invade epithelium
• Cause deformity in cells and villi
• Initiates inflammatory response
– Water secretion increases & nutrient absorption
decreases
• Epidemiology
– Oocysts eliminated in feces
• Individuals can expel organisms for up to 2 weeks
after diarrhea ceases
– Person-to-person spread occurs
– Cysts can survive long periods in food and water
• Resistant to chlorination but to small for most filters
– Zoonotic with a wide host range
– Diagnosed by oocysts in stool
• Prevention
– Careful monitoring of municipal water supplies
– Pasteurization of drinks
– Sanitary disposal of feces
– Immunodeficient should avoid contact with
animals and recreational water activities
• Treatment
– Replacement of water and electrolytes
Amebiasis
• Causative agent: Entamoeba histolytica
– Exists in two forms
– Feeding trophozoite
– Dormant cyst
• 3 forms of Amebiasis:
– Luminal –asymptomatic
– Amebic dysentery – more severe; dysentery, colitis and
ulceration of mucosal lining
– Invasive extra-intestinal –necrotic lesions form in liver,
lungs, spleen, kidneys and brain
• Epidemiology
– Transmission usually fecal-oral route
• Cysts survive 1-2 weeks in environment
– No animal reservoir
• 10% of global population are carriers
– 3rd leading cause of parasitic death
• 50 million cases and 100,00 deaths annually
– Diagnosed by cysts or trophozoites in stool
• Prevention
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Disinfection, filtration and boiling of water
Sanitary disposal of feces
Good hygiene practices
Safe sex
• Treatment
– Oral rehydration
– Metronidazole or iodoquinol
Helminthic Infestations
• Macroscopic, multi-cellular parasitic worms
• Cestodes
– Flat, segmented, monoecious
– Intestinal parasites that lack complete digestive system
• Nematodes
– Round, un-segmented, diecious, sexually dimorphic
– Complete digestive system and protective cuticle
• Tapeworm Infestations
– Cestodes
• Taenia saginata – beef tapeworm
• Taenia solium – pork tapeworm
– Signs and symptoms
• Usually asymptomatic
• nausea, abdominal pain, weight loss, and diarrhea
may occur
• Worm may cause intestinal blockage
Scolex used for attachment
Monoecious proglottids may be motile
Complex life cycle divided between
definitive and intermediate hosts
– Epidemiology
• Highest incidence poor rural areas
• Inadequate sewage treatment
• Humans live in close contact with livestock
– Diagnosed by presence of proglottids in feces
• Prevention
– Relies on thorough cooking of meats and sewage
treatment
• Treatment
– Niclosamide or praziquantel
– May require surgical removal of worm
• Pinworm Infestations
– Nematode
• Enterobius vermicularis
• Sexually dimorphic
– Signs and symptoms
• perianal itching, irritability,
decreased appetite
– Epidemiology
• Infections commonly occur in children
• Most common parasitic worm in the US
– Diagnosis based on microscopic id of eggs or
presence of adult pinworms
• Prevention
– Requires strict personal hygiene
• Treatment
– Pyrantel pamoate or mebendazole