What is Amebiasis?
Amebiasis, also known as amoebic dysentery, is a common infection caused by parasites called amoebas, particularly from the Entamoeba group. People with amebiasis might not notice any symptoms, while others may experience mild to severe symptoms like stomach pain, diarrhea, or bloody diarrhea. Serious complications can occur, such as inflammation and even a tear in your gut wall, leading to peritonitis, a serious infection of your abdomen. Amebiasis can also cause anemia, a condition where your body doesn’t have enough healthy red blood cells.
If the parasite makes its way into the bloodstream, it can spread throughout the body and land in the liver, leading to amoebic liver abscesses, which are pockets of pus. Interestingly, these abscesses can occur even without previous diarrhea. Diagnosis of amebiasis usually involves examining stool samples under a microscope. Increased white blood cell (WBC) count – our body’s defense mechanism against infections – may also signal amoebiasis. The most accurate test, however, is checking for specific antibodies – proteins our body produces in response to infections – in the blood.
Improving sanitation is the main way to prevent amebiasis. Treatment depends on where the infection is located. Infections in body tissues are treated with medications like metronidazole, tinidazole, nitazoxanide, dehydroemetine, or chloroquine, while infections in the intestine are treated with diloxanide furoate or iodoquinoline. Effective treatment might require a combination of these medications. Even if someone doesn’t show symptoms, they still need to be treated as they can pass the parasite to others.
Amebiasis can be found globally, claiming between 40,000 to 110,000 lives every year. E. histolytica, the primary amoeba behind amebiasis, is classified as a category B biodefense organism, which essentially means it’s a potential biological threat. This is due to its ability to survive in various environments, spread easily, resist chlorine treatment, and contaminate food. Apart from the digestive tract, E. histolytica can affect many organ systems in the body.
What Causes Amebiasis?
Amebiasis is a disease caused by a microscopic parasite called Entamoeba histolytica. There are three types of these parasites that can live in your intestines. Out of these, Entamoeba histolytica is the one that most often leads to illness.
The other two types, Entamoeba dispar and Entamoeba moshkovskii, are usually not harmful. However, we are still unsure about the harm caused by Entamoeba moshkovskii and more cases are being reported.
These parasites typically spread from person to person through shared food or water that has been contaminated with infected feces. In some rare instances, it can also spread through sexual activities.
Risk Factors and Frequency for Amebiasis
Amebiasis is a disease that affects people all around the world, but it’s more common in developing countries. This is typically due to poor sanitation and contaminated water. Every year, approximately 50 million people around the world get this infection, leading to over 100,000 deaths.
People usually get infected when they eat or drink something that has been contaminated with the parasite E. histolytica. This can commonly happen to travelers visiting regions where the disease is common. People who live in institutions or those with weakened immune systems are also more at risk.
The E. histolytica parasite can survive for a long time outside the body, waiting to infect a new host. It can also be spread via sexual contact or through the use of shared medical equipment. Despite the serious global impact of amebiasis, we don’t yet have any vaccines or preventative medications for this disease.
Signs and Symptoms of Amebiasis
Amebiasis is a medical condition that can often be symptomless, but can also lead to a wide variety of health issues. Symptoms typically develop between two to four weeks after exposure. Signs of this illness can range from mild, such as abdominal cramps and watery diarrhea, to severe issues like colitis that causes bloody diarrhea with mucus. Younger people and pregnant individuals tend to experience more severe symptoms. Other risk factors for amebiasis include the use of corticosteroids and poor nutrition. In extreme cases, a rare but very serious complication can occur known as toxic megacolon.
In some cases, amebiasis can also lead to health problems outside the intestines. The most common is an amoebic liver abscess, which affects less than 4% of patients and typically occurs within two to four weeks before the initial infection. Symptoms of a liver abscess include pain in the right upper abdomen, fever, and tenderness. In rare cases, the abscess may rupture into the lung cavity or sac around the heart, leading to pleural or pericardial effusion. Amebiasis can also rarely affect the heart, brain, kidneys, spleen, and skin. It can lead to conditions such as proctocolitis, toxic megacolon, peritonitis, brain abscess, and heart inflammation. As a result, amebiasis is one of the leading parasitic causes of death in humans.
- Abdominal cramps
- Watery diarrhea
- Colitis with bloody diarrhea and mucus
- Severe conditions mostly in young and pregnant people
- Toxic megacolon
- Amoebic liver abscess
- Pain in the right upper abdomen
- Fever
- Tenderness
- Pleural or pericardial effusion
- Proctocolitis
- Toxic megacolon
- Peritonitis
- Brain abscess
- Heart inflammation
Testing for Amebiasis
Amebiasis, an infection caused by a tiny organism, can be identified in several ways. Doctors often attempt to find the organism right in the stool or via a rectal swab. However, this method only works in about 30% of patients.
Testing for specific substances (antigens) that the organism produces using a method called an enzyme-linked immunosorbent assay or using a technique called polymerase chain reaction is another common approach. Yet, the most efficient detection technique appears to be the loop-mediated isothermal amplification assay. This method is rapid, straightforward to execute, and boasts high specificity and sensitivity.
In further cases, examining the patient through an ultrasound or CT scan can help determine if the amebiasis has affected parts of the body outside the intestines.
Other methods include culture tests using samples from fecal or rectal biopsies or liver aspirates. However, those tests are successful in picking up the infection about 60% of the time.
If a doctor suspects a liver abscess, they may take a CT-guided image and then perform a liver aspiration – a procedure to draw out fluid from the liver. This fluid often looks chocolate-like or is a thick, dark viscous fluid. A liver aspiration is usually performed if the abscess is large or is about to burst.
If stool tests are negative for amebiasis, a colonoscopy may be conducted. During a colonoscopy, doctors can take scrapings from the inside lining of the colon for examination.
Lastly, blood tests may show a variety of changes. These can include an increased number of white blood cells, an increase in certain types of white blood cells called eosinophils, elevated bilirubin and transaminase enzymes (indicating liver damage), mildly low red blood cell count or mild anemia, and an increased erythrocyte sedimentation rate (ESR) – a common marker for inflammation in the body.
In some cases, depending on the symptoms, an ultrasound or other imaging studies might be required. For instance, an ultrasound can help identify whether a liver abscess is present.
Treatment Options for Amebiasis
To treat the symptoms of amebiasis, which is an infection caused by a parasite called amoeba, the main treatments are keeping the patient hydrated and using certain medications. These meds include metronidazole and tinidazole, which are often used to treat a range of parasitic infections.
If the amoeba infection has led to an abscess in the liver, a procedure may be carried out to remove it. This involves using a CT scan to guide a needle into the abscess to drain it out, and is often combined with the use of the medication metronidazole as well.
Sometimes more invasive treatments such as surgery may be needed. Situations where this may be the case include severe bleeding in the digestive tract, a condition called toxic megacolon where the large intestine becomes rapidly enlarged, a perforated colon which is a hole in the colon, or liver abscesses that cannot be drained by a needle.
Other medications that can be used to treat amebiasis include paromomycin and diloxanide furoate. These work in the intestines to clear out the amoebas and stop the infection from returning.
What else can Amebiasis be?
- Colitis caused by bacteria like E. coli, Yersinia, or Campylobacter
- Pericarditis, an inflammation of the lining around the heart
- Perforated bowel, a hole in the wall of the intestine
- Diverticulitis, an inflammation or infection in one or more small pouches in the digestive tract
- Hepatitis A, a viral liver disease
- Cholecystitis, an inflammation of the gallbladder
- Shigellosis or Salmonellosis, both bacterial infections that can cause diarrhea
What to expect with Amebiasis
Amoebic infections, if not treated, can be very serious and even deadly. They are second only to malaria in terms of causing death. Certain groups of people are more likely to get severe amoebic infections:
* Women who are pregnant
* Women who have recently given birth
* Newborn babies
* People who do not get enough nutrition
* People who are taking corticosteroids, which are drugs that can weaken the immune system
* People with cancer
It’s good news, though, because when this condition is treated, the outlook is generally good. Still, re-infection is common in some parts of the world. After treatment, less than 1% of people die from this condition.
However, there can be complications. In 5% to 10% of cases, amoebic liver abscesses, which are pockets of pus in the liver caused by the infection, may burst and spread into the abdominal cavity, a situation which can potentially increase the death rate. Amoebic pericarditis (inflammation of the lining around the heart) and pulmonary amebiasis (acquisition of the infection in the lungs) can also be highly fatal, with the death rate exceeding 20%.
Nowadays, with effective treatment, less than 1% of people with uncomplicated amoebic disease die from it. However, the bursting of an infected amoebic liver abscess is a serious complication and can lead to high death rates.
Possible Complications When Diagnosed with Amebiasis
Complications that can occur from medical conditions include:
- Toxic megacolon — extreme dilation of the colon
- Fulminant necrotizing colitis — rapid inflammation and tissue death in the colon
- Rectovaginal fistula — an abnormal connection between the rectum and vagina
- Ameboma — accumulation of amebiasis in the digestive tract
- Intraperitoneal rupture of liver abscess — bursting of a pocket of pus in the liver
- Secondary bacterial infection — infection that occurs after the initial infection
- Extension of infection from the liver into the pericardium or pleura — spread of infection to the tissues around the heart or lungs
- Dissemination in the brain — spread of disease into the brain
- Bowel perforation — creation of a hole in the wall of the digestive tract
- Stricture of the colon — narrowing of the colon
- Gastrointestinal bleeding — internal bleeding in the digestive system
- Empyema — buildup of fluid and pus in the lining of the lungs
Preventing Amebiasis
* Steer clear of drinking water that could be contaminated.
* Opt for bottled water while traveling.
* Make water safe to drink by using a chemical called tetraglycine hydroperiodide.
* Try to avoid eating raw salads and fruits. If possible, remove the skin of the fruit before eating.
* Always wash all vegetables thoroughly before cooking them.
