What is amebiasis?

Amoebiasis is a disease caused by a one-celled parasite called Entamoeba histolytica (ent-a-ME-ba his-to-LI-ti-ka).

Amoebiasis or amoebic dysentery is a common parasitic enteral infection. It is caused by any of the amoebas of the Entamoeba group.

 

 

 

Amoebiasis may present with no symptoms or mild to severe symptoms, including abdominal pain, diarrhea, or bloody diarrhea. Severe complications may include inflammation and perforation, resulting in peritonitis. People affected may develop anemia.

If the parasite reaches the bloodstream, it can spread through the body and end up in the liver, causing amoebic liver abscesses.

Liver abscesses can occur without previous diarrhea. Diagnosis is typically by stool examination using a microscope. An increased WBC count may be present. The most accurate test is specific antibodies in the blood.

Prevention of amoebiasis is by improved sanitation. Two treatment options are possible, depending on the location. Amoebiasis in tissue is treated with metronidazole, tinidazole, nitazoxanide, dehydroemetine, or chloroquine.

A luminal infection is treated with diloxanide furoate or iodoquinoline. Effective treatment may require a combination of medications. Infections without symptoms require treatment, but infected individuals can spread the parasite to others.

Amoebiasis is present all over the world. Each year, about 40000 to 110000 people die from amoebiasis infection.

E. histolytica is classified as a category B biodefense organism because of its environmental stability, ease of dissemination, resistance to chlorine, and its ability to easily spread through contaminated food products. Besides the GI tract, E. histolytica can affect many organ systems.

Who is at risk for Amoebiasis ?

Although anyone can have this disease, it is most common in people who live in developing countries that have poor sanitary conditions. In the United States, amebiasis is most often foundin immigrants from developing countries.

It also is found in people who have traveled to developing countries and in people who live in institutions that have poor sanitary conditions. Men who have sex with men can become infected and can get sick from the infection, but they often do not have symptoms.

How can I become infected with E. histolytica?

• By putting anything into your mouth that has touched the stool of a person who is infected with E. histolytica.
• By swallowing something, such as water or food, that is contaminated with E. histolytica.
• By touching and bringing to your mouth cysts (eggs) picked up from surfaces that are contaminated with E. histolytica.

What are the symptoms of Amoebiasis

On average, about one in 10 people who are infected with E. histolytica becomes sick from the infection. The symptoms often are quite mild and can include loose stools, stomach pain, and stomach cramping. Amoebiasis dysentery is a severe form of amebiasis associated with stomach pain, bloody stools, and fever.

Rarely, E. histolytica invades the liver and forms an abscess. Even less commonly, it spreads to other parts of the body, such as the lungs or brain.

 

How is amebiasis diagnosed?

Your health care provider will ask you to submit stool samples. Because E. histolytica is not always found in every stool sample, you may be asked to submit several stool samples from several different days.

Diagnosis of Amoebiasis 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 peopleare told that they are infected with E. histolytica even though they are not. Entamoeba histolytica and another amoeba, Entamoeba dispar, which is about 10 times more common, look the same when seen under a microscope.

Unlike infection with E. histolytica, which sometimes makes people sick, infection with E. dispar never makes people sick and therefore does not needto be treated.

If you have been told that you are infected with E. histolytica but you are feeling fine, you might be infected with E. dispar instead.

Unfortunately, most laboratories do not yet have the tests that can tell whether a person is infected with E. histolytica or with E. dispar. Until these tests become more widely available, it usually is best to assume that the parasite is E. histolytica.

A blood test is also available. However, the test is recommended only when your health care provider thinks that your infection has invaded the wall of the intestine (gut) or some other organ of your body, such as the liver.

One problem is that the blood test may still be positive if you had amebiasis in the past, even if you are no longer infected now.

How is Amoebiasis treated?

Several Amoebiasis are available to treat amebiasis. Treatment must be prescribed by a physician. You will be treated with only one antibiotic if your E. histolytica infection has not made you sick.

You probably will be treated with two antibiotics (first one and then the other) if your infection has made you sick.

I am going to travel to a country that has poor sanitary conditions. What should I eat and drink there so I will NOT become infected with E. histolytica or other such germs?

• Drink only bottled or boiled (for 1 minute) water or carbonated (bubbly) drinks in cans or bottles. Do not drink fountain drinks or any drinks with ice cubes. Another way to make water safe is by filtering it through an “absolute 1 micron or less” filter and dissolving iodine tablets in the filtered water. “Absolute 1 micron” filters can be found in camping/outdoor supply stores.
• Do not eat fresh fruit or vegetables that you did not peel yourself.
• Do not eat or drink milk, cheese, or dairy products that may not have been pasteurized.
• Do not eat or drink anything sold by street vendors.

Should I be concerned about spreading infection to the rest of my household?

Yes. However, the risk of spreading infection is low if the infected person is treated with antibiotics and practices good personal hygiene.

This includes thorough hand washing with soap and water after using the toilet, after changing diapers, and before handling food.

Etiology

The protozoan Entamoeba histolytica causes amebiasis. There are three species of intestinal Amoebiasis . Entamoeba histolytica causes most symptomatic diseases.

Entamoeba dispar is nonpathogenic, and Entamoeba moshkovskii is reported increasingly, but its pathogenicity is unclear. These organisms are spread via the oral-fecal route. The infected cysts are often found in contaminated food and water. Rare cases of sexual spread have also been reported. Read more: Amoebiasis 

Epidemiology

Amoebiasis occurs worldwide but is predominantly seen in developing countries due to decreased sanitation and increased fecal contamination of water supplies. Globally, approximately 50 million people contract the infection, with over 100000 deaths due to amebiasis reported annually.

The principal source of infection is ingestion of water or food contaminated by feces containing E. histolytica cysts. Hence, travelers to developing countries can acquire amebiasis when visiting the endemic region. Those who are institutionalized or immunocompromised are also at risk.

The organism E. histolytica is viable for prolonged periods in the cystic form in the environment. It can also be acquired after direct inoculation of the rectum, from anal or oral sex, or from equipment used for colonic irrigation. Despite the global public health burden, there are no vaccines or prophylactic medications to prevent Amoebiasis.

Pathophysiology

E. histolytica is a pseudopod-forming, protozoal parasite that causes proteolysis and tissue lysis. Humans are the natural hosts. Amoebic infection occurs by the ingestion of mature cysts in fecally-contaminated food or water or from the hands.

Excystation of the mature cysts occurs in the small intestine, and trophozoites are released; the trophozoites then move to the large intestine. The trophozoites increase by binary fission and produce cysts.

Both stages pass in the feces. The cysts can survive days to weeks in the external environment because of the protection provided by the cyst wall. The cyst is responsible for further transmission of the parasite. Ingestion of only a small number of organisms can cause disease.

Histopathology

Histology of the intestinal infection is nonspecific. It usually reveals discrete ulcers, mucosal thickening, and edematous mucosa. Sometimes flask-shaped ulcers may be seen in the submucosal layers. In some patients, flask-shaped ulcers are seen.

History and Physical

Although most cases of amebiasis are asymptomatic, many patients with E. histolytica present with a spectrum of illness. The incubation period from Amoebiasis is between 2 to 4 weeks.

Symptoms range from mild abdominal cramps and watery diarrhea to severe colitis producing bloody diarrhea with mucus. Young people tend to have a more severe disease compared to older individuals.

Fulminant colitis can present with bloody diarrhea in some patients. Risk factors include the use of corticosteroids, poor nutrition, young age, and pregnancy. Toxic megacolon can be a complication and is associated with very high mortality.

A few patients may develop invasive extraintestinal disease. The most common extraintestinal manifestations are an amoebic liver abscess.

A liver abscess develops in less than 4% of patients and may occur within 2 to 4 weeks after the initial infection. Liver abscess usually presents with right upper quadrant pain, fever, and tenderness to palpation.

An Amoebiasis liver abscess may rupture into the pleural cavity or pericardium, presenting as pleural or pericardial effusion; however, this is a rare occurrence.

Rarely, amebiasis may affect the heart, brain, kidneys, spleen, and skin. One can also develop proctocolitis, toxic megacolon, peritonitis, brain abscess, and pericarditis. Hence, Amoebiasis is a leading parasitic cause of death in humans.

Evaluation

Amoebiasis can be diagnosed by a demonstration of the organism using direct microscopy of stools or rectal swabs. However, the organisms are seen in only 30% of patients.

Antigen detection using an enzyme-linked immunosorbent assay and polymerase chain reaction techniques is often done.

However, the most promising detection method is the loop-mediated isothermal amplification assay because of its rapidity, operational simplicity, high specificity, and sensitivity. An ultrasound or CT scan evaluates for extraintestinal Amoebiasis.

Cultures can be done from fecal or rectal biopsy specimens or liver aspirates. Cultures are not always positive, with a success rate of about 60%.

Liver aspiration using CT-guided imaging is often performed when there is a collection in the liver. The liver aspiration usually reveals a chocolate-like or thick, dark viscous fluid.

Liver aspiration is indicated when the abscess is large, or there is a threat of imminent rupture.

A colonoscopy is done to obtain scrapings of the mucosal surface. It is appropriate when the stool studies are negative for amebiasis.

Blood tests may reveal the following:

• Elevated WBC
• Eosinophilia
• Elevated bilirubin and transaminase enzymes
• Mild anemia
• Elevated ESR

Imaging studies may be required depending on the presentation. Ultrasound can identify a liver abscess.

Treatment / Management

The primary therapy for symptomatic amebiasis requires hydration and the use of metronidazole and/or tinidazole. These two agents are dosed as follows:

Metronidazole dosing for adults is 500 mg orally every 6 to 8 hours for 7 to 14 days.
Tinidazole adult dosing is 2 g orally each day for 3 days.

Luminal agents such as paromomycin and diloxanide furoate are also used. An amoebic liver abscess can be managed by aspiration using CT guidance in combination with metronidazole.

Surgery is sometimes required to treat massive gastrointestinal bleeding, toxic megacolon, perforated colon, or liver abscesses not amenable to percutaneous drainage. click here: Flagyl IV Infusion 100ml  & Nizonide Suspension 30ml

Differential Diagnosis

Colitis caused by E. coli, Yersinia, or Campylobacter
Pericarditis
Perforated bowel
Diverticulitis
Hepatitis A
Cholecystitis
Shigellosis/salmonellosis

 

 

Prognosis

If left untreated, amoebic infections have very high morbidity and mortality. In fact, mortality is second only to malaria. Amoebic infections tend to be most severe in the following populations:

• Pregnant women
• Postpartum women
• Neonates
• Malnourished individuals
• Individuals who are on corticosteroids
• Individuals with malignancies

When the condition is treated, the prognosis is good, but recurrent infections are common in some parts of the world.

The mortality rates after treatment are less than 1%. However, amoebic liver abscesses may be complicated by an intraperitoneal rupture in 5% to 10% of cases, potentially increasing the mortality rate. Amoebic pericarditis and pulmonary amebiasis have a high mortality rate exceeding 20%.

Today with effective treatment, mortality rates are less than 1% in patients with uncomplicated disease. However, rupture of an infected amebic liver abscess carries a high mortality.