Amoebiasis

Amoebiasis Dr.T.V.Rao MD

ENTAMOEBA HISTOLYTICA
Entamoeba histolytica was first described by Lambl in 1859 and Losch established it pathogenic nature in 1875 in a dysenteric patient is St.Petersberg
Councilman and lafleur in 1981 described amoebic liver abscess.
Schauudinn ( 1903 ) differentiated pathogenic and nonpathogenic types of Amoebae

Amebiasis
Amebiasis (am-e-BI-a-sis) is a disease caused by a one-celled parasite called Entamoeba histolytica (ent-a-ME-ba his-to-LI-ti-ka) .
Although it is more common in people who live in tropical areas with poor sanitary conditions

Amoebiasis a Major Health Problem
Amoebiasis is estimated to cause 70,000 deaths per year world wide Symptoms can range from mild diarrhea to dysentery with blood and mucus in the stool. E. histolytica is usually a commensals organism. Severe Amoebiasis infections (known as invasive or fulminant amoebiasis) occur in two major forms. Invasion of the intestinal lining causes amoebic dysentery or amoebic colitis.

Trends of Amoebiasis

Transmission of Amebiasis
Amoebiasis is transmitted by fecal contamination of drinking water and foods, but also by direct contact with dirty hands or objects as well as by sexual contact. Additionally, geophagy is a common route of infection in certain cultures.
Doctortvrao’s ‘e’ learning series

Nature of the disease
Symptoms are usually gastrointestinal including diarrhoea, vomiting, abdominal pain or discomfort and fever. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Most infected people are asymptomatic but this disease has the potential to make the sufferer dangerously ill, especially if there is any suggestion of immunocompromised.

Events on Amoebiasis

Trophozoites of E.histolytica

Trophozoites and Cystic stages

Cystic stage - E.histolytica

Amoebiasis causes Epithelial damage

Numerous Eosinophilic spherical structure within necrotic area .

Tissue showing Amoebic infection
The spherical structure (Trophozoites) has one basophilic nuclei about the size of RBC’s. Note some RBC's are phagocytosed by the Trophozoites (erythrophagocytosis)

Virulence factors
Trophozoites of E.histolytica interact with host through a series of steps
1 Adhesion of target cell, phagocytosis and cytopathic effect
2 E.histolytica induces both Humoral and cell mediated immune responses.
3 Virulence factors – In many circumstances lumen dwelling Amoeba may be asymptomatic
4 Causes disease only when invade the Intestine
5 Virulence is associated with secretion of Cysteine proteniase which assists the organism in digesting the extracellular matrix and invading tissues

Cysteine proteinase - Complement factor C3
It is observed Cysteine proteinase produced by invasive strains of E.histolytica inactivates the complement factor C3 and are thus resistant to Complement mediated lysis.

Cysteine proteinase virulent factor
Cysteine proteinase is an important virulent factor
Its presence makes E.histolytica is resistant to complement mediated lysis
Can cleave the extracellular structural matrix and degrade fibronectin and laminin, as well as type I collagen.
In this process basement membrane is degraded and leads to invasion

Zymodeme
Lectin binding Zymodeme analysis, genome specific DNA analysis and staining with Monoclonal antibodies have been successfully used as markers to identify invasive strains of E.histolytica

Types of Zymodemes
Based on Electrophoretic mobility E.histolytica strains are classified into 22 Zymodemes
However only 9 are invasive

Invasive x Noninvasive strains
The invasive and non invasive strains may appear identical may represent two distinct species
1 Invasive strain – E.histolytica
2 Non invasive strains reclassified as E.dispar.

Host Factor Contributions
Several factors contribute to influence infection
1 Stress
2 Malnutrition
3 Alcoholism
4 Corticosteriod therapy
5 Immunodeficiency
6 Alternation of Bacterial flora

Risk Factors
People in developing countries that have poor sanitary conditions
Immigrants from developing countries
Travellers to developing countries
People who live in institutions that have poor sanitary conditions
HIV-positive patients
Men who have sex with men

No symptoms (in the majority of cases),
Vague gastrointestinal distress,
Dysentery (with blood and mucus).
Dysentery

How the Amebiasis Manifests
Most cases of amebiasis have very mild symptoms or none.
More severe infection may cause fever, profuse diarrhea, abdominal pain, jaundice, anorexia, and weight loss.
In severe cases, it can lead to development of abscesses (pockets of amoebae and inflammatory cells) in the liver or, more rarely, the brain.

Clinical symptoms are Vague
Wide spectrum, from asymptomatic infection ("luminal amebiasis"), to invasive intestinal amebiasis (dysentery, colitis, appendicitis, toxic mega colon, amebomas), to invasive extra intestinal amebiasis (liver abscess, peritonitis, pleuropulmonary abscess, cutaneous and genital amoebic lesions).

Diagnosis of Amebiasis

BASICS METHODS IN DIAGNOSIS
Fresh stool: wet mounts and permanently stained preparations (e.g., trichrome).
Concentrates from fresh stool: wet mounts, with or without iodine stain, and permanently stained preparations (e.g., trichrome). Concentration procedures, however, are not useful for demonstrating Trophozoites.

Diagnosis of Amebiasis
Diagnosis of amebiasis can be very difficult. One problem is that other parasites and cells can look very similar to E. histolytica when seen under a microscope. Therefore, sometimes people are told that they are infected with E. histolytica even though they are not. Entamoeba histolytica and another ameba, Entamoeba dispar , which is about 10 times more common, look the same when seen under a microscope

Microscopy
This is the traditional means of diagnosing the disease—one simply looks at a sample of stool under a microscope. Because E. histolytica is not always found in every stool sample, several samples from different days may be needed. Sometimes red blood cells that have been ingested by the parasite are visible.

Microscopic examination of Stool
A sample of freshly collected fecal specimen containing mucous and blood is transferred on a slightly warm slide and covered with cover slip and examined microscopically

E . histolytica / E. dispar cyst .

E. histolytica / E. dispar cysts stained with trichrome

Specific Diagnosis of active infection should demonstrate Trophozoites
Motile Trophozoites throwing pseudopodia and containing red blood cells found in large number
Endoplasm appear bluish or found glass in appearance and nucleus is not visible but faint outline may be observed

Charcot Leyden crystals in stool examination supports the Diagnosis ,
Cysts have smooth and thin cell wall and contain round, retractile chromotoid bars
Glycogen mass is not visible
RBC’s and pus cells are found in fair number
Charcot Leyden crystals, diamond shaped clear and retractile structures are present in faeces

IDOINE PREPARATION OF STOOL
Routinely not used
Trophozoites stains yellow to light brown,
Nucleus is clearly visible with central karyosome
Cysts shows a smooth and hyaline appearance, Nucleus is clearly seen and no more than 4 nuclei are present, Glycogen mass stains brown, while chromotoid bars are not stained.

Mucosal Scrapings
Mucosal scrapings can be obtained by sigmoidoscopy useful in atypical presentations and may serve as adjunct to conventional stool examination for Ova and cyst
Direct wet mount, a permanently stained smear and immuno stained smears are examined.

Extra intestinal Amoebiasis
The specimens are obtained from Liver, lung, or Brain biopsy samples and subjected to routine Histopathology ( H&E) sections
Giemsa stained touch preparations which will revel Trophozoites in extra intestinal lesions.

Amoebic Liver Abscess
The pus in liver abscess appear as red Anchovy sauce like appearance
The material aspirated is likely to contain Trophozoites and may be detected by direct microscopic examination

Serological Diagnosis
The serological become reactive in invasive Amoebiasis
1 Indirect Heamagglutination assay ( IHA )
2 ELISA
3 Latex agglutination test
4 gel diffusion
5 Counter current Imunoelectrphoresis
Serological tests remain positive for several years ever after successful treatment

Culture
Cultures are not done routinely
Boeck and Drbohlav’s medium modified by Laidlaw extensively used for isolation and maintenance of E.histolytica.
Diamonds axenic medium used in studies on Pathogenicty, antigenic characterization and drug sensitivity tests

Do we need culturing for Diagnosis ?
Trying to get the amoeba to grow outside the body is very difficult and unreliable, and is therefore not generally done

Immunity in Amoebiasis
Infection with invasive strains of E.histolytica induce both Humoral and cellular response.
Infection offers some degree of protection.

Immunological Tests are not confirmatory of Acute Infections
When the body is exposed to an infection, the immune system creates antibodies to fight it off. These can be detected with a blood test, and provide evidence that the person has been infected with E. histolytica . Unfortunately, this test does not distinguish between past and present infection

Emerging methods in Diagnosis
These are considered the most useful tests for detecting E. histolytica . They test directly for the parasite itself by exposing some stool to a strip of paper coated with antibodies. The parasites will stick to the antibodies on the paper. The test distinguishes E. histolytica from other parasites.

Treating Amebiasis .
Frequently, either metronidazole (Flagyl) or tinidazole (Fasigyn) are used to treat Amebiasis. If this does not work, Chloroquine, emetine, and dehydroemetine can be used. Eliminating cysts in carriers who do not have symptoms is accomplished with diloxanide furoate (Furamide ), iodoquinol (Yodoxin ), and paromomycin. Nitazoxanide is a newer drug that shows promise against not only E. histolytica but many other parasites as well.

Treating extra intestinal Amoebiasis
Amoebic abscess is treated similarly to dysentery, with antibiotics. Sometimes surgical drainage may be performed, but this is usually to rule out other (bacterial) causes of abscess. It is also performed if an abscess is about to, or has already ruptured.

Preventing Amoebiasis
Drink only bottled or boiled (for 1 minute) water, or carbonated (bubbly) drinks in cans or bottles. Fountain drinks and any drinks with ice cubes are not safe. Water can be made safe by filtering it through an "absolute 1 micron or less" filter and dissolving iodine tablets in the filtered water.
Avoid fresh fruit or vegetables that were peeled by someone else.
Avoid milk, cheese, or dairy products that may not have been pasteurized.
Avoid anything sold by street vendors.

Food safety
Thoroughly cook all raw foods.
* Thoroughly wash raw vegetables and fruits before eating.
* Reheat food until the internal temperature of the food reaches at least 167º Fahrenheit.
Wash your hands before preparing food, before eating, after going to the toilet or changing diapers, after smoking or after using a tissue or handkerchief.

Personal Hygiene
Wash hands thoroughly with soap and hot running water for at least 10 seconds after using the toilet or changing a baby's diaper.
Clean bathrooms and toilets often. Pay particular attention to toilet seats and taps.
Avoid sharing towels or face washers.

Vaccines
Vaccines are being developed and tested for the treatment of Amebiasis. The vaccine is a modified version of the proteins expressed on the surface of E. histolytica. A study in rodents found that the vaccine prevented the formation of liver abscesses, but much more research is needed to determine if these vaccines are useful and safe in humans

Created for Awareness for Medical and Paramedical workers in Developing World Dr.T.V.Rao MD Email [email_address]

Amoebiasis

by tumalapalli venkateswara rao on May 28, 2009

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Amoebiasis — Presentation Transcript