Echinococcus granulosus

People who accidentally swallow the eggs of the Echinococcus granulosus tapeworm are at risk for infection. Dogs that eat home-slaughtered sheep and other livestock become infected with the tapeworm Echinococcus granulosus and the tapeworm eggs can be found in their stool. Direct contact with infected dogs, particularly intimate contact between children and their pet dogs, may lead to human infection. Ingestion of soil, water and vegetables contaminated with infected dog feces may also lead to infections. Echinococcus granulosus eggs can survive snow and freezing conditions.

Humans can be exposed to these eggs by “hand-to-mouth” transfer or contamination.

• By ingesting food, water or soil contaminated with stool from infected dogs. This might include grass, herbs, greens, or berries gathered from fields.
• By petting or handling dogs infected with the Echinococcus granulosus tapeworm. These dogs may shed the tapeworm eggs in their stool, and their fur may be contaminated.

Where is cystic echinococcosis (CE) found?

CE is found in Africa, Europe, Asia, the Middle East, and Central and South America. Highest prevalence is found in populations that raise sheep. In North America, Echinococcus granulosus is rarely reported in Canada and Alaska, and a few human cases have also been reported in Arizona and New Mexico in sheep-raising areas. In the United States, most infections are diagnosed in immigrants from counties where CE is endemic. Risk factors for human infection include uncontrolled dogs living closely with people, uncontrolled slaughter of livestock, and unsanitary living conditions.

What are the symptoms of cystic echinococcosis (CE)?

CE is caused by cyst-like tapeworm larvae growing in the body. CE usually involves the liver or the lungs, but can also be found in other organs of the body. Because the cysts are slow-growing, infection with CE may not produce any symptoms for many years. Pain or discomfort in the upper abdominal region or chest, nausea, vomiting, or coughing may occur as a result of the growing cysts. Rupture of cyst fluid can lead to allergic reactions or even death.

What should I do if I think I have cystic echinococcosis (CE)?

See your health care provider if you think you may have cystic echinococcosis. CE can be diagnosed with imaging studies such as X-rays or MRI scans, which are helpful to see the cysts in most organs. Blood tests are available to help diagnose an infection, but may not always be accurate. If surgery is necessary, confirmation of the diagnosis can be made by the laboratory.

How is cystic echinococcosis (CE) treated?

Until recently, surgery was the only option for treatment of CE. However, now medication and a modified surgical procedure (aspiration) are increasingly used and can replace the need for surgical removal of the hydatid cysts. Even so, surgery may be necessary in certain circumstances. After surgery, medication may be needed to keep the cyst from growing back.

Can cystic echinococcosis (CE) be prevented?

If you live in an area where Echinococcus granulosus is found in sheep or cattle, take the following precautions to avoid infection:

• Wash your hands with soap and warm water after handling dogs, and before handling food.
• Teach children the importance of washing hands to prevent infection.
• Avoid ingestion of food, water or soil contaminated with stool from dogs. This might include grass, herbs, greens, or berries gathered from fields.
• Don’t allow your dogs to wander freely or to capture and eat raw meat from sheep, cattle, pigs, and goats.
• Don’t home slaughter sheep and other livestock.
• If you think your pet may have eaten infected meat, consult your veterinarian about the possible need for preventive treatments.

More on: Handwashing

This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.

Echinococcus is an infection caused by a parasitic tapeworm from the Echinococcus genus. A few different types of tapeworms can cause echinococcus in humans, including: E. granulosus, E. multilocularis, and E. vogeli. In some cases, the organs affected depend on which type of tapeworm has caused your infection.

The infection is rare in the United States. It occurs more often in the Mediterranean, Middle East, Africa, and Central Asia. If left untreated, it can be fatal. With treatment, your outlook may be good.

Your symptoms will vary depending on which organs are affected. According to Stanford University:

The infection affects the liver in about 75 percent of people who contract it. Symptoms may include pain in your abdomen and the formation of cysts on your liver.

The infection affects the lungs in about 22 percent of people who contract it. Respiratory symptoms may include chest pain and coughing up bloody mucus.

Other areas of your body can also be affected, including your skin, spleen, or kidneys.

If a parasitic tapeworm infects you, echinococcus will develop. The parasite enters a host, which is usually an animal, such as a dog, sheep, or goat. The worm lives in the bowels of the animal and releases its eggs into the animal’s feces.

You’re most likely to contract the infection when you eat food that has been contaminated with animal feces. After eating contaminated food, the incubation period is usually a few months long.

This means it takes a few months before symptoms appear. Certain strains of the parasite can have a longer incubation period that may last up to a few years.

One risk factor for contracting the parasite is exposure to the feces of dogs, cattle, pigs, or sheep. For example, if you work on a farm with these animals, you may be at higher risk.

Cases of the infection have been reported in the United States, but the risk is higher in countries where the parasite is more common.

Another risk factor is taking in food or water contaminated with the tapeworm eggs.

Your doctor may ask you about your symptoms and perform medical tests to diagnose your infection. For example, they may use a chest X-ray to rule out other types of infection. Your doctor may also use an abdominal MRI or CT scan to make their diagnosis.

Because the incubation period can be long, echinococcus parasites may be discovered while your doctor is performing medical tests for other reasons.

Certain medications can destroy the parasite. In some cases, your doctor may also recommend surgery. Your specific treatment plan will depend on the severity of your symptoms, as well as the organs affected.

Medication

Medication is almost always used to treat echinococcus. For example, your doctor may prescribe mebendazole or albendazole.

They may also recommend taking anti-inflammatory medication to treat inflammation of your organs caused by the parasite. Sometimes chemotherapy medications can be used to treat organ cysts caused by the parasite.

Surgery

In some instances, your doctor may recommend surgery to treat cysts caused by the infection. If the infection has affected your brain and fluid has accumulated there, your doctor may also recommend surgery to install a shunt. This device is used to drain fluid from your brain.

Your outlook depends on the extent of your infection and the organs affected. In some instances, cysts may rupture, which can be life threatening. But if your doctor is able to effectively treat the cysts, your outlook may be good.

There are several different steps you can take to prevent an echinococcus infection. In areas of the world where the parasite is common, education can help.

Removing the worms from dogs can help stop the spread of infection. Correct disposal of animal feces can reduce exposure to tapeworm eggs.

Proper handling of cattle at farms and slaughterhouses is also essential. This includes enforcing meat inspection procedures. Avoiding undercooked or raw beef, pork, and fish can also help you avoid echinococcus.

Washing fruits and vegetables, especially in areas where the tapeworm is common, may help prevent infection.

Echinococcus granulosus is a parasitic worm which belongs to the family Taeniidae under order Cyclophyllidea of class Cestoda. It is also known as Dog tapeworm, Hydatid worm or Hyper-tape worm. It is found all over the world. The larval form causes hydatid disease in man. This disease is also known as human echinococcosis or hydatidosis. At present, it causes major health problems in many countries.

Systematic Position

• Phylum:Platyhelminthes
• Class: Cestoda
• Order: Clyclophyllidea
• Family: Taeniidae
• Genus:Echinococcus
• Species:Echinococcus granulosus

• Definitive Host: Dog, wolf, fox and jackel
• Intermediate Host: Sheep, cattle, pig, human
• Stage found in human: Larval stage.

Morphology of Echinococcus granulosus

Adult Worm

Echinococcus granulosus is a small tapeworm which can grow 3 to 6 mm in length. It comprises of a scolex, neck and 3 or 4 segments. The scolex has 4 suckers and a rostellum with two rows of 30 to 36 hooks. The neck is short and thick.

The anterior first segment is immature, the second segment is mature and third segment or fourth segment (when present) is a gravid segment. Each gravid proglottid contains an average number of 823 eggs. The terminal segment is the longest and broadest.

Eggs are spherical in shape and resemble the egg of Taenia solium and Teania saginata. It contains a hexacanth embryo with 3 pairs of hooks. The egg is infective to human, cattle, sheep and other herbivorous animals.

Larval Forms

Larval forms are found within the hydatid cyst. It is the scolex of the future adult worm.

Life Cycle of Echinococcus granulosus

The eggs are discharged with the feces of the definitive hosts such as Dog, wolf, fox and jackel. An itermidiate host such as Sheep, cattle, pig, etc swallow the eggs while grazing in the field and human particularly children swallow the eggs due to intimate handling of infected dogs or other definitive hosts.

In the duodenum, hexacanth embryos are hatched out. About eight hours after infestation, the embryo penetrates through the mucous of the intestine and enters the tributaries of portal vein. It is carried to the liver and may be arrested (liver acts as the first filter). Some embryos may pass the liver, enter the pulmonary circulation and filter out lungs (the second filter). A few embryos may enter the systemic circulation and are trapped in various organs.

Whenever the embryos settles, it forms a hydatid cyst. From the inner surface of the cyst, brood capsules with a number of scolices develop. A definitive host such as dog becomes infected by ingestion of the larva with the infected viscera of an intermediate host such as cattle. The scolex becomes evaginated and develops into an adult worm in 6 to 7 weeks, Thus the cycle is repeated.

Hydatid Cyst

A hydatid cyst may be 1 to 20 cm in diameter. The cyst wall is secreted by the embryo. The cyst wall consists of the following 2 layers:

Outer or circular layer (Ectocyst): It is a laminated hyaline membrane of 1 mm thickness. It is the protective layer.

Inner or germinal layer (endocyst): It is a cellular layer consisting of a protoplasmic mass containing a number of neucei. This vital layer forms (a) brood capsules with scolices(b) daughter cysts (c) hydatid fluid and (d) outer layer.

(a) Brood capsules and scolices: Brood capsules sprout from the germinal layer and consist of only germinal layer. The scolices ( 5 to 20 or more) develop on the inner surface of brood capsules. The fully developed scolices have invaginated sucker and a circle of hooklets. The brood capsules may detach from the cyst wall and then may disintegrate liberating free scolices to form the grains of hydatid sand.

(b) Daughter Cyst: Daughter cysts develop inside the mother cyst. It consists of an outer laminated and inner germinative layer from which brood capsules and scolices develop and also grand-daughter cysts may develop. The daughter cysts mostly grow inwards and are called endogenous daughter cysts. Exogenous cysts may be formed , e.g. in the bone. If the cyst ruptures within the host, the scolices may develop into daughter cysts at different parts of the body.

Hydatid Fluid: It shows the following characteristics-

• Hydatid sand is the sediment of hydatid fluid. It consists of liberated brood capsules, free scolices and loose hooklets.
• If the antigen is released due to rupture or absorption then there may occur anaphylactic symptoms. The antigen is used for immunological tests.
• Clear, colorless with specific gravity of 1005-1010 and pH of 6.7.

Acephalocysts: These are the cysts where brood capsules are not developed or are developed without any scolices.

Pathogenesis

The following symptoms are expressed when hydatid disease/ echinococcosis or hydatidosis occur in man:

• Abdominal pain;
• Nausea;
• Vomiting;
• Chronic cough;
• Chest pain;
• Shortness of breath;
• Anorexia;
• Weight loss;
• Weakness;
• General malaise;
• Hepatic failure, etc.

Diagnosis

• Ultrasonography imaging is the best technique to diagnose of both cystic and alveolar echinococcosis.
• Different serological tests are also effective to detect specific antibodies.
• The best available technique is the ELISA which is suitable for the detection of antigens in feces.
• PCR (polymerase chain reaction) is also employed to detect the parasite from DNA isolated from feces or eggs.
• X-rays, CAT scans etc. can also be done to diagnose the echinococcosis.

Treatment

The treatment for echinococcosis is often expensive and complicated. In many cases, it requires extensive surgery and need prolonged drug therapy. Besides these, the following treatment methods should be applied: