Viral and parasitic gastroenteritis
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Viral and Parasitic Gastroenteritis. Viral Gastroenteritis. Inflammation of the stomach and intestines caused by viruses, which is also known as the stomach flu This highly contagious illness spreads through close contact with people who are infected contaminated food or water

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Viral and parasitic gastroenteritis

Viral and Parasitic Gastroenteritis


Viral gastroenteritis

Viral Gastroenteritis

  • Inflammation of the stomach and intestines caused by viruses, which is also known as the stomach flu

  • This highly contagious illness spreads through

    • close contact with people who are infected

    • contaminated food or water

  • It can easily spread in close quarters

    • childcare facilities

    • Schools

    • nursing homes

    • cruise ships


Viral and parasitic gastroenteritis

  • Viruses are responsible for up to ¾ of all infective diarrhoeas

  • Viral gastroenteritis is the second most common viral illness after upper respiratory tract infection

  • In developing countries, viral gastroenteritis is a major killer of infants who are undernourished

  • Rotaviruses are responsible for half a million deaths a year


Hepatitis

HEPATITIS

  • Hepatitis is inflammation of the liver

  • The disease can be caused by infections from parasites, bacteria, or viruses

  • Liver damage can also result from alcohol, drugs, or poisonous mushrooms

  • Hepatitis A, B, and C are clinically the most important forms of viral liver disease


Viral and parasitic gastroenteritis

  • Persons at risk of hepatitis B infection include

    • 1) individuals with multiple sex partners

    • 2) men who have sex with men

    • 3) sex contacts of infected persons

    • 4) injection drug users

    • 5) household contacts of chronically infected persons

    • Death from chronic hepatitis B occurs in 15 to 25 percent of chronically infected persons


Viral and parasitic gastroenteritis

  • Most hepatitis C infections result from illegal injection drug use

  • Transfusion-associated cases occurred prior to blood donor screening

    • now the incidence is less than 1 per 2 million transfused blood units

  • Fifty percent of those with hepatitis C go on to have

    • chronic liver disease

    • liver failure (cirrhosis)

    • liver cancer

  • Hepatitis C is the number one reason for receiving a liver transplant in the United States


Viral and parasitic gastroenteritis

Classification of hepatitis viruses based on mode of transmission

Classification of major viral agents causing hepatitis


Hepatitis a virus structure and classification

Hepatitis A Virus: Structure and Classification

  • Virus classification

    • Group:Group IV ((+)ssRNA)

    • Family:Picornaviridae

    • Genus:Hepatovirus

    • Species:Hepatitis A virus

  • Separate genus because ofdifferences with other enteroviruses

  • Naked icosahedral capsid

  • SS RNA (740 nucleotides)

  • Single serotype worldwide

  • Humans only reservoir

Electron micrograph of hepatitis A virions


Hepatitis a virus transmission

Hepatitis A Virus Transmission

  • Fecal-oral

  • Close personal contact

    • e.g., household contact, sex contact, child day care centers

  • Contaminated food, water

    • e.g., infected food handlers

  • Blood exposure

    • rare


Viral and parasitic gastroenteritis

Estimated prevalence of hepatitis A virus


Hepatitis a pathogenesis

Hepatitis A: Pathogenesis

  • Incubation 4 weeks (range 2-6 weeks)

  • Oral cavity GI tract liver via blood

  • Replicates in hepatocytes (little damage to cells) released via bile to intestines 7-10 days prior to clinical symptoms

  • Liver damage and clinical syndrome result of immune response and not direct effect of virus


Hepatitis a clinical features

Hepatitis A: Clinical Features

  • An acute illness with

    • discrete onset of symptoms

      • e.g. fatigue, abdominal pain, loss of appetite, nausea, vomiting

    • Jaundice

      • elevated serum aminotransferase levels, dark urine, light stool

    • Adults are usually more symptomatic

    • Patients are infective while they are shedding the virus in the stool- usually before the onset of symptoms

    • Most cases resolve spontaneously in 2-4 weeks

    • Complete recovery 99%


Hepatitis a diagnosis

Hepatitis A - Diagnosis

  • Detection of IgM antibody

  • IgG positive 1-3 weeks later; suggests prior infection or vaccination


Hepatitis a treatment

Hepatitis A - Treatment

  • Supportive: no specific role of antiviral therapy

  • Lifelong immunity likely after infection or vaccination


Preventing hepatitis a

PREVENTING HEPATITIS A

  • Hygiene

    • e.g., hand washing

  • Sanitation

    • e.g., clean water sources

  • Hepatitis A vaccine

    • pre-exposure


Hepatitis a vaccines

HEPATITIS A VACCINES

  • Inactivated vaccine

  • Highly immunogenic

    • 97%-100% of children, adolescents, and adults have protective levels of antibody within 1 month of receiving first dose

    • essentially 100% have protective levels after second dose

  • Highly efficacious

    • In published studies, 94%-100% of children protected against clinical hepatitis A after equivalent of one dose


Hepatitis a vaccines1

HEPATITIS A VACCINES

  • 1st dose at time 0

  • 2nd dose 6-12 months afterwards


Post vaccination testing

POST-VACCINATION TESTING

  • Not recommended

  • High response rate among vaccinees

  • Commercially available assay not sensitive enough to detect lower (protective) levels of vaccine-induced antibody


Duration of protection after vaccination

DURATION OF PROTECTION AFTER VACCINATION

  • Protection begins 4 weeks after vaccine

  • Persistence of antibody

    • At least 5-8 years among adults and children

  • Efficacy

    • No cases in vaccinated children at 5-6 years

  • Mathematical models of antibody decline suggest protective antibody levels persist for at least 20 years

  • Other mechanisms, such as cellular memory, may contribute


Hepatitis a vaccine

Hepatitis A Vaccine

  • Pre-exposure Vaccination

    • Persons at increased risk for infection

      • travelers to intermediate and high HAV-endemic countries

      • MSM (Men who have sex with men)

      • Drug users

      • Persons who have clotting factor disorders

      • persons with chronic liver disease

    • Communities with historically high rates of hepatitis A -routine childhood vaccination


Hepatitis a vaccine immunogenicity side effects

Hepatitis A Vaccine Immunogenicity, Side Effects

  • Immunogenicity in children, adolescents, adults

    • 94-100% positive 1 month after dose 1

    • 99-100% positive after dose 2

  • Most common side effects

    • Sore injection site (50%), headache (15%), malaise (7%)

    • No severe reactions known

    • Safety in pregnancy unknown (risk likely is low)

  • Currently licensed for aged 1 year and older


Hepatitis b

Hepatitis B


Hepatitis b structure

Hepatitis B: Structure

  • Member of the hepadnavirus group

  • Virionalso referred to as Dane particle

  • 42nm enveloped virus

  • Core antigens located in the center (nucleocapsid)


Structure and replication

Structure and Replication

  • Circular partially double stranded DNA of virus

  • Initial replication to complete circular DNA with subsequent transcription to make several mRNAs some of which are translated into viral proteins

  • One of the mRNAs is replicated with a reverse transcriptase making the DNA that will eventually be the core of the progeny virion

  • Some DNA integrates into host genome causing carrier state

  • Virus stable and resist many stresses making them more infectious


Hepatitis b virus

Hepatitis B Virus

TEM micrograph showing hepatitis B viruses

The structure of hepatitis B virus


Viral and parasitic gastroenteritis

Prevalence of chronic infection with hepatitis B virus, 2006


Global patterns of chronic hbv infection

Global Patterns of Chronic HBV Infection

  • High (>8%): 45% of global population

    • lifetime risk of infection >60%

    • early childhood infections common

  • Intermediate (2%-7%): 43% of global population

    • lifetime risk of infection 20%-60%

    • infections occur in all age groups

  • Low (<2%): 12% of global population

    • lifetime risk of infection <20%

    • most infections occur in adult risk groups


Possible outcomes of hbv infection

Possible Outcomes of HBV Infection

Acute hepatitis B infection

95% of infant-acquired infections

3-5% of adult-acquired infections

Chronic HBV infection

Chronic hepatitis

12-25% in 5 years

Cirrhosis

20-23% in 5 years

6-15% in 5 years

Hepatocellular carcinoma

Liver failure

Liver transplant

Death

Death


Outcome of hepatitis b virus infection by age at infection

100

100

80

80

60

60

Chronic Infection

40

40

20

20

Symptomatic Infection

0

0

Birth

1-4 yrs

1-6 mos

7-12 mos

Older Children

and Adults

Outcome of Hepatitis B Virus Infection by Age at Infection

Chronic Infection (%)

Symptomatic Infection (%)


Hbv modes of transmission

HBV Modes of Transmission

  • Sexual

  • Parenteral

  • Perinatal


Concentration of hbv in various body fluids

Low/Not

High

Moderate

Detectable

blood

semen

urine

serum

vaginal fluid

feces

wound exudates

saliva

sweat

tears

breast milk

Concentration of HBV in Various Body Fluids


Hepatitis b symptoms

Hepatitis B Symptoms

  • About 50%-60% of adults with HBV infection have no signs or symptoms

  • Those who do have symptoms might experience:

    • Jaundice

    • Fatigue

    • Abdominal pain

    • Loss of appetite

    • Nausea, vomiting

    • Joint pain


Hbv pathogenesis

HBV Pathogenesis

  • Virus enters hepatocytes via blood

  • Immune response (cytotoxic T cell) to viral antigens expressed on hepatocyte cell surface responsible for clinical syndrome

  • 5 % become chronic carriers (HBsAg> 6 months)

  • Higher rate of hepatocellular in chronic carriers, especially those who are “e” antigen positive

  • Hepatitis B surface antibody likely confers lifelong immunity

  • Hepatitis B Ab indicates low transmissibility


Elimination of hbv transmission

Elimination of HBV Transmission

  • Prevent perinatal HBV transmission

  • Routine vaccination of all infants

  • Vaccination of children in high-risk groups

  • Vaccination of adolescents

    • all children up through age 18

  • Vaccination of adults in high-risk groups


Hepatitis b vaccine

Hepatitis B Vaccine

  • Licensed in 1982

  • 3 dose series, typical schedule 0, 1-2, 4-6 months

    • 2 dose series (adult dose)

  • Protection ~30-50% dose 1; 75% - 2; 96% - 3

    • lower in older, immunosuppressive illnesses

      • e.g., HIV, chronic liver diseases, diabetes, obese, smokers


Hepatitis b vaccine safety

Hepatitis B Vaccine Safety

  • Side effects rare

  • Anaphylaxis estimated to occur in 1/600,000 doses given

  • No scientific data to link hepatitis B vaccine with multiple sclerosis (MS), other autoimmune diseases, autism


Hepatitis b vaccination

Hepatitis B Vaccination

  • Routine infant

  • Ages 11-15 and through age 18

  • Over 18 – high risk

    • Occupational risk

    • Hemodyalisis patients

    • All STD clinic clients

    • Multiple sex partners or prior STD

    • Inmates in Correctional settings

    • MSM

    • IDU

    • Institution for developmental disability


Hepatitis c virus

Hepatitis C Virus


Hepatitis c structure and classification

Hepatitis C Structure and Classification

  • Member of the flavivirusfamily

  • Enveloped single stranded RNA virus

  • Humans and chimpanzees only known reservoirs

  • 6 serotypes (genotypes) and multiple subtypes

    • based on high variability of envelope glycoproteins


Occupational transmission of hcv

Occupational Transmission of HCV

  • Inefficient by occupational exposures

  • Average incidence 1.8% following needle stick from HCV-positive source

  • Case reports of transmission from blood splash to eye

  • Prevalence 1-2% among health care workers


Perinatal transmission of hcv

Perinatal Transmission of HCV

  • Transmission only from women HCV-RNA positive at delivery

    • Average rate of infection 6%

    • Higher (17%) if woman co-infected with HIV

  • No association with

    • Delivery method

    • Breastfeeding

  • Infected infants do well

    • Severe hepatitis is rare


Sexual transmission of hcv

Sexual Transmission of HCV

  • Occurs, but efficiency is low

    • Rare between long-term steady partners

    • Factors that facilitate transmission between partners unknown

  • Accounts for 15-20% of acute and chronic infections in the United States Partner studies


Household transmission of hcv

Household Transmission of HCV

  • Rare but not absent

  • Could occur through percutaneous/mucosal exposures to blood

    • Contaminated equipment used for home therapies

    • Through sharing of contaminated personal material (razors, toothbrushes)


Other potential exposures to blood

Other Potential Exposures to Blood

  • No or insufficient data showing increased risk

    • intranasal cocaine use, tattooing, body piercing, acupuncture, military service


Hepatitis c clinical features

Hepatitis C: Clinical Features

  • Acute infection asymptomatic in over 80% of patients, when present, acute illness usually mild

    • Acute symptoms include jaundice, nausea, abdominal pain, loss of appetite, dark urine


Chronic hepatitis c factors promoting progression or severity

Chronic Hepatitis C Factors Promoting Progression or Severity

  • Increased alcohol intake

  • Age > 40 years at time of infection

  • HIV co-infection

  • Other

    • Male gender

    • Chronic HBV co-infection


Hepatitis c diagnosis

Hepatitis C: Diagnosis

  • ELISA

    • usually positive within 2-5 months after infection

  • PCR

    • positive 1-2 weeks post infection


Hepatitis d

Hepatitis D

  • Defective virus that requires co-infection with hepatitis B for replication

  • Enveloped with SS RNA genome

  • Only antigen encoded in the delta antigen


Hepatitis d virus modes of transmission

Hepatitis D Virus Modes of Transmission

  • Percutaneous exposures

    • injecting drug use

  • Permucosalexposures

    • sex contact


Viral and parasitic gastroenteritis

Geographic Distribution of HDV Infection

Taiwan

Pacific Islands

HDV Prevalence

High

Intermediate

Low

Very Low

No Data


Hepatitis d pathogenesis

Hepatitis DPathogenesis

  • Pathogenesis

    • Immune mediated

    • Co-infection

      • infection with B at the same time (more severe)

    • Superinfection

      • acquisition of Hep D in chronically Hep B


Hepatitis d clinical features

Hepatitis D - Clinical Features

  • Coinfection

    • severe acute diseaselow risk of chronic infection

  • Superinfection

    • usually develop chronic HDV infection

    • high risk of severe chronic liver disease


Hepatitis e virus

Hepatitis E Virus


Viral and parasitic gastroenteritis

TEM micrograph of hepatitis E virions.


Hepatitis e

Hepatitis E

  • Non-enveloped single stranded RNA virus

  • Resembles calicivirus or Norwalk agent

  • Similar illness to Hep A except high mortality in pregnant women


Hepatitis e epidemiologic features

Hepatitis E - Epidemiologic Features

  • Most outbreaks associated with fecallycontaminated drinking water

  • Minimal person-to-person transmission

  • U.S. cases usually have history of travel to HEV-endemic areas


Hepatitis e clinical features

Hepatitis E - Clinical Features

  • Incubation periodAverage 40 days

    Range 15-60 days

  • Case-fatality rateOverall, 1%-3%Pregnant women, 15%-25%

  • Illness severityIncreased with age

  • Chronic sequelaeNone identified


Prevention and control measures for travelers to hev endemic regions

Prevention and Control Measuresfor Travelers to HEV-Endemic Regions

  • Avoid drinking water (and beverages with ice) of unknown purity, uncooked shellfish, and uncooked fruit/vegetables not peeled or prepared by traveler


Rotavirus

Rotavirus

  • Rotaviruses, found in many mammalian species

  • Rotaviruses have a characteristic morphology that distinguishes them from other reoviruses


A epidemiology

A. Epidemiology

  • Rotaviruses are divided into seven serogroups (A through G)

    • Group A is the most important cause of outbreaks diseases in humans

  • Transmission of rotaviruses is via the fecal–oral route

  • Seasonal incidence is associated with rotavirus infections

    • January through March

  • Infectious particles are relatively stable

    • can survive for extended periods on various surfaces

  • Account for about 50% of severe diarrhea in infants and young children (up to age 2 years)


B clinical significance

B. Clinical significance

  • Following ingestion, rotaviruses infect the epithelial cells of the small intestine

    • primarily the jejunum

  • Rotaviruses are able to reach the small intestine because they are resistant to the acid pH of the stomach

  • The incubation period is usually 48 hours or less

  • Infection can be subclinical or may result in symptoms

    • ranging from mild diarrhea and vomiting to severe, nonbloody, watery diarrhea with dehydration and loss of electrolytes


Viral and parasitic gastroenteritis

  • Although rotavirus infections are probably equally widespread around the world

    • the outcomes of infection vary significantly in different regions

    • malnutrition dramatically increases the severity of the infection

  • Infection results in some degree of lifelong immunity with reinfected adults suffering a much milder illness

  • Infants who are breastfed also suffer milder disease manifestations

  • In developing countries and areas where medical facilities or personnel may be lacking, the mortality is significant

    • An estimated 1 million deaths per year worldwide result from rotavirus infection


C laboratory identification

C. Laboratory identification

  • Severe diarrhea, dehydration, and electrolyte loss can be due to a variety of causes

    • definitive diagnosis cannot be made on clinical grounds alone

  • Identification can be made by detection of viral capsid antigens in stool samples using ELISA

  • An increase in the titer of antiviral antibody in a patient’s serum can also be diagnostic


E treatment and prevention

E. Treatment and prevention

  • There is no specific antiviral drug appropriate for treatment of rotavirus infections

  • The most important clinical intervention is the rapid and efficient replacement of fluids and electrolytes, usually intravenously

  • Prevention of rotavirus infections requires improved sanitation measures


Adenoviridae

ADENOVIRIDAE

  • Adenoviruses are

    • Nonenveloped

    • Icosahedral

    • Double-stranded linear DNA

  • They commonly cause diseases such as

    • Respiratory tract infections

    • Gastroenteritis

    • Conjunctivitis


Viral and parasitic gastroenteritis

  • Commonly infecting humans, other mammals, and birds

  • Over fifty serotypes of human adenoviruses are known

    • most individuals have been infected by several different types by adulthood

  • Have not been associated with human malignancies


A epidemiology and pathogenesis

A. Epidemiology and pathogenesis

  • The site of the clinical syndrome is generally related to the mode of transmission

    • most adenoviruses are primarily agents of respiratory disease

  • Most adenoviruses also replicate efficiently and symptomatically in the intestine

    • can be isolated from

      • stool well after respiratory disease symptoms have ended

      • from the stools of healthy persons

  • Ocular infections are transmitted by

    • direct inoculation of the eye by virus-contaminated hands

    • ophthalmologic instruments

    • children swim together


B structure and replication

B. Structure and replication

  • The adenovirus capsid is composed of hexoncapsomers

  • Replication of adenoviruses essentially follows the general model for DNA viruses

  • Attachment to a host cell receptor occurs via knobs on the tips of the viral fibers

  • The viral genome is then progressively uncoated while it is transported to the nucleus


Viral and parasitic gastroenteritis

The structure of adenovirus

1 = penton capsomeres

2 = hexoncapsomeres

3 = viral genome (linear dsDNA)


C clinical significance

C. Clinical significance

  • Adenoviruses all replicate well in epithelial cells

  • The observed disease symptoms are related primarily to the killing of these cells, and systemic infections are rare

  • Most adenovirus infections are asymptomatic, but certain types are more commonly associated with disease than others

  • These diseases can be conveniently grouped into those affecting the

    • 1) respiratory tract

    • 2) eye

    • 3) gastrointestinal (GI) tract

    • 4) other tissues, including the urinary tract and heart


Gastrointestinal diseases

Gastrointestinal diseases

  • Most human adenoviruses multiply in the GI tract and can be found in stools

    • generally asymptomatic infections

  • Two serotypes have been associated specifically with infantile gastroenteritis

  • Adenovirus infections have been estimated to account for 5 to 15 % of all viral diarrheal disease in children


D laboratory identification

D. Laboratory identification

  • Isolation of virus for identification desirable in cases of

    • epidemic disease

    • nosocomial outbreak, especially in the nursery

  • The virus is more commonly detected by direct test of stool specimens by ELISA


E treatment and prevention1

E. Treatment and prevention

  • No antiviral agents are currently available

  • Prevention of epidemic respiratory disease by immunization has been used

    • only for protection of the military population

  • This vaccine contains live, unattenuatedadenovirus


Caliciviruses formerly known as norwalk like virus

Caliciviruses(formerly known as Norwalk-like virus)

  • Norovirus replicates in the GI tract and is shed in the stool

  • Infection is by

    • fecal–oral route following ingestion of contaminated food or water

    • person-to-person contact

    • contact with contaminated surfaces

  • Major cause of epidemic acute gastroenteritis

  • It affects primarily adults and school-age children

    • but not infants

  • The clinical presentation is characterized by nausea, vomiting, and diarrhea


Viral and parasitic gastroenteritis

  • Symptoms last 24 to 48 hours, and the disease is self-limited

  • Radioimmunoassays and ELISA tests are available for the detection of antiviral antibodies

  • No specific antiviral treatment is available

  • Careful attention to hand washing and measures to prevent contamination of food and water supplies should reduce the incidence of these infections


Gastrointestinal system infection protozoa and parasitic worm helminth

Gastrointestinal System InfectionProtozoa and Parasitic worm (Helminth)


Leishmania donovani visceral leishmaniasis k ala azar

Leishmania donovani Visceral leishmaniasis (kala-azar)

  • In the visceral disease, the parasite initially infects macrophages, which, in turn, migrate to the spleen, liver, and bone marrow, where the parasite rapidly multiplies

  • Symptoms include

    • intermittent fevers

    • weight loss

    • spleen and liver enlarge

    • jaundice may develop

  • Mortality is nearly 100% within 2 years if the disease is untreated

  • In some cases, complications resulting from secondary infection and emaciation result in death


Viral and parasitic gastroenteritis

Leishmania donovani in bone marrow cell


Echinococcus granulosus dog tapeworm

Echinococcus granulosus (dog tapeworm)

  • Infection produces large, hydatidcysts in liver, lung, and brain

  • Anaphylactic reaction to worm antigens can occur if the cyst ruptures

  • The disease follows ingestion of eggs in dog feces

  • Sheep often serve as an intermediate host

  • Echinococcosisis diagnosed by CT scan or biopsy of infected tissue and is treated with albendazoleand surgical excision of intact cysts


Viral and parasitic gastroenteritis

E. granulosus scolex

E. granulosus life cycle


Schistosoma mansoni

Schistosoma mansoni

  • The primary site of infection is the gastrointestinal tract

  • Damage to the intestinal wall is caused by the host’s inflammatory response to eggs deposited at that site

  • The eggs also secrete proteolytic enzymes that further damage the tissue

  • Clinical presentation includes GI bleeding, diarrhea, and liver damage


Viral and parasitic gastroenteritis

  • Periportal fibrosis leads to portal hypertension and massive splenomegaly

  • The disease is transmitted by direct skin penetration

  • This form of schistosomiasis is diagnosed by identification of characteristic eggs in the stool


Viral and parasitic gastroenteritis

Schistosomesencopula

A Schistosoma mansoni egg with the characteristic lateral spine


Entamoeba histolytica amebic dysentery

Entamoeba histolytica (Amebic dysentery)

  • A world wide in distribution

  • More often in tropical countries with poor sanitary conditions

  • A commensal protozoa when human has a normal immune function

  • Invading host tissues and causing amoebiasis when human has a lower immune function


Morphology

Morphology

  • Trophozoite

    • No regular in shape, 20~60μm in size

    • An active-moving trophozoiteproduce pseudopods (organelle)

    • A spherical central nucleus

    • Peripheral chromatin

    • Erythrophagocytosis


Viral and parasitic gastroenteritis

  • Cyst

    • Spherical in shape & 10~20μm in diameter. 1~4 nuclei (similar to that of the trophozoite)

    • Immature cyst (1 or 2 nuclei) has the glycogen vacuole & chromatoidbody

    • No inclusions, disappear in mature cyst (4 nuclei)

    • Infective stage


Viral and parasitic gastroenteritis

Entamoeba histolytica cyst

Life-cycle of Entamoeba histolytica


Life cycle

Life cycle

  • Basic model: cyst → trophozoite → cyst

  • Parasitic location: large intestine (common); intestinal tissue or other tissues (occasional)

  • Infective stage: mature cyst

  • Trophozoitein diarrhea or pus; Cyst in formed feces

  • Infection: by ingestion of mature cyst


Clinical classification

Clinical classification

  • 90% persons infected are carriers

  • Intestinal amoebiasis

    • Acute intestinal amoebiasis

      • amoebic dysentery (bloody, mucus-containing diarrhea) + lower abdominal discomfort + tenesmus

    • Chronic intestinal amoebiasis

      • dyspepsia + weight loss + asthenia (common) / diarrhea


Viral and parasitic gastroenteritis

  • Extraintestinal amoebiasis

    • Liver : amoebic hepatitis + amoebic liver abscess --- pain in right-upper-quadrant + fever + marked tenderness of liver

    • Lung: amoebic pulmonary abscess --- pain in chest + cough + fever

      • Sometimes, it can be carried to other organs

        • Brain, skin


Laboratory diagnosis

Laboratory diagnosis

  • Fecal examination

    • Wet mounts

      • Trophozoitesin diarrhea feces

    • Wet mounts stained with iodine

      • Cyst in formed feces

  • Pus examination

    • Trophozoitesin aspirate pus from abscesses


Giardia lamblia giardiasis

Giardia lamblia(Giardiasis)

  • Giardiasis is the most commonly diagnosed parasitic intestinal disease in the United States

  • Ingested cysts form trophozoitesin the duodenum, where they attach to the wall but do not invade

  • Giardia infections are often clinically mild, although in some individuals, massive infection may damage the duodenal mucosa


Viral and parasitic gastroenteritis

  • Because the Giardia parasite preferentially inhabits the duodenum, fecal examination may be negative

  • A commercial enzyme-linked immunosorbent assay to measure Giardia antigen in fecal material has proven useful

  • Metronidazole is an effective treatment

  • G. lamblia cysts are resistant to chlorine concentrations used in most water treatment facilities


Viral and parasitic gastroenteritis

Giardia cell, SEM

Life cycle of Giardia lamblia


Ascaris lumbricoides ascariasis roundworm disease

Ascaris lumbricoidesAscariasis(roundworm disease)

  • It is second only to pinworms as the most prevalent multicellular parasite in the United States

  • Approximately one third of the world’s population is infected with this worm

  • The disease is transmitted by ingestion of soil containing the organism’s eggs

  • Humans are the sole host


Viral and parasitic gastroenteritis

  • Larvae grow in the intestine, causing abdominal symptoms, including intestinal obstruction

  • Roundworms may pass to the blood and through the lungs

  • Roundworm disease is diagnosed by detection of characteristic eggs in the stool

  • It is treated with pyrantelpamoateor mebendazole


Viral and parasitic gastroenteritis

An adult female Ascaris worm.

Fertile egg in human faeces (detail)


Ancylostoma duodenale hookworm disease

Ancylostomaduodenale(Hookworm disease)

  • The worm attaches to the intestinal mucosa causing

    • anorexia

    • ulcer-like symptoms

    • chronic intestinal blood loss, leading to anemia

  • The disease is transmitted through direct skin penetration by larvae found in soil

  • Hookworm disease is diagnosed by identification of characteristic eggs in the stool

  • It is treated with pyrantelpamoateor mebendazole


Strongyloides stercoralis strongyloidiasis threadworm disease

StrongyloidesstercoralisStrongyloidiasis (threadworm disease)

  • It is relatively uncommon compared with infections by other intestinal nematodes

  • It is a relatively benign disease in healthy individuals but can progress to a fatal outcome in immunocompromised patients because of dissemination to the CNS or other deep organs in certain immunocompromised Patients

  • The disease is transmitted through direct skin penetration by larvae found in soil

  • Threadworm disease is diagnosed by identifying larvae in the stool

  • It is treated with thiabendazole, albendazole or ivermectin


Viral and parasitic gastroenteritis

First stage larva (L1) of S. stercoralis


Trichuris trichiura trichuriasis whipworm disease

TrichuristrichiuraTrichuriasis (whipworm disease)

  • The infection is usually asymptomatic; however, abdominal pain, diarrhea, flatulence, and rectal prolapse can occur

  • The disease is transmitted by ingestion of soil containing the organism’s eggs

  • Whipworm disease is diagnosed by identifying characteristic eggs in the stool

  • It is treated with mebendazole


Viral and parasitic gastroenteritis

Egg of Trichurisvulpis


Taenia saginata taeniasis

Taenia saginata (Taeniasis)

  • This form of the disease is caused by the larval form of Taenia saginata (beef tapeworm)

  • The organism primarily infects the intestines and does not produce cysticerci

  • Most infected individuals are asymptomatic

  • The disease is transmitted by larvae in undercooked or raw beef

  • Taeniasisis diagnosed by detection of proglottidsin the stool


Viral and parasitic gastroenteritis

Taenia saginata proglottid stained to show uterine branches. The pore on the side identifies T. saginata as a cyclophyllidcestode.


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