Hydatid Disease – Echinococcosis or Hydatidosis

Hydatid disease is also known as hydatidosis or echinococcosis. It occurs due to Echinococcus granulosus and Echinococcus Multilocularis.

Hydatid disease is parasitic disease caused by cysts containing the larval stages of the Echinococcus granulosus tapeworm (Dog Tapeworm).

Echinococcosis is a caused by infection with tapeworms of the genus Echinocococcus. Echinococcosis is classified as two main types of the disease are cystic echinococcosis and alveolar echinococcosis.

The two major species of Echinococcus are- 

Echinococcus granulosus and Echinococcus multilocularis.

Echinococcus granulosus which cause cystic echinococcosis (CE) and Echinococcus multilocularis which cause alveolar echinococcosis (AE). Hydatid cysts of Echinococcus granulosus develop in internal organs site mainly the liver and lungs of humans.

Adult Echinococcus tapeworms infect dogs and the tapeworm eggs are shed in faeces of dogs, that infect the other animals and humans. People become infected by ingesting the tapeworm eggs via hand-to-mouth transfer after handling dogs or objects contaminated with tapeworm eggs, or from consuming contaminated food or water.

Cystic Echinocccosis

Cystic echinocccosis (CE), also known as hydatid disease. Hydatid cysts is caused by infection with the larval stage of Echinococcus granulosus.

Cystic echinocccosis causes slowly enlarging cysts in the liver, lungs, and other organs.

Persons with cystic echinococcosis often remain asymptomatic and cysts grow over the several years. Appearance of symptoms depends on the location of the cyst. The hydatid cysts containing the larval parasites grow large enough to cause discomfort, nausea pain, and vomiting.

The hydatid cysts are mainly found in the liver and lungs and also appear in kidneys, heart, spleen, bone, and central nervous system, including the brain and eyes.

If cyst rupture, most frequently caused by trauma and may cause mild to severe anaphylactic reactions, result of the release of cystic fluid.

Alveolar echinococcosis

Alveolar echinococcosis (AE) disease is caused by infection with the larval stage of Echinococcus multilocularis, causing parasitic tumors that can form in the liver, brain, lungs, and other organs. 

Alveolar echinococcosis (AE), in humans characterized by parasitic tumors in the liver, can cause liver failure and may spread to lungs and other organs, rarely the brain

Larval forms of E. multilocularis invade and destroy surrounding tissues and cause discomfort, pain, vomiting, weight loss, and malaise. 

Epidemiological Triad

Agent – The causative agent is the larval stage of  Echinococcus granulosus (dog tapeworm) tapeworm of dog/sheep.

Host – People involved in raising sheep, sheep farming

Humans can only be infected by swallowing eggs passed by an infected dog.

Children young age are particularly at risk of becoming infected with the tapeworm eggs.

Environment – Infection with the tapeworm eggs contaminated faeces. Ingestion of water or food contaminated with tapeworm eggs. Rainy season and the high humidity of the soil.

Mode of Transmission

1. Environment (dust, grass or dirt) to hands to person mouth (feco-oral route).

2. From dog hairs to hand

3. Hand-to-mouth transfer of tapeworm eggs from dog faeces.

4. Environmental contamination by faeces of tapeworm-infected dog/sheep.

5. Accidental ingesting of soil, water, or food that had contaminated by the fecal matter of an infected dog.

Incubation Period

Cystic echinococcosis is characterized by an asymptomatic incubation period of 12 months to years.

Alveolar echinococcosis is characterized by an asymptomatic incubation period range of 5–15 years.

Clinical Manifestation

The clinical features depend upon –

1. Organ involved

2. Site of organ involved

3. Stage of cyst development

5. Viability of cyst content

The symptoms of hydatid disease depend on which organs are affected. The most commonly affected vital organ is the liver. The kidneys, brain and lungs are also affected.

In rare cases, hydatid cysts may form in the heart or thyroid gland or within bone.

Symptoms may include-

1. Stomach upset

2. Swollen abdomen

3. Unexplained weight loss – weakness and fatigue

4. Diarrhoea

5. Anaemia

6. Cough – blood or the fluid from a ruptured cyst; may be coughed up

7. Jaundice – due to pressure from enlarging cyst can cause jaundice.

8. Cyst may rupture and can cause a life-threatening allergic reaction (anaphylaxis) and heavily infested organ may fail.

Symptoms are disease related to mass pressure on structure, infection and rupture of cyst content into surrounding body cavities.

Pressure symptoms of large cyst in Liver are- 

1. Liver cyst usually presents in right upper quadrants with dull ache or a feeling of abdominal pain and distention.

2. On clinical examination, enlargement liver with a rounded mass is felt on surface.

2. A large cyst in the hilar region compresses the common hepatic duct cause cholestasis (obstruction of bile flow).

3. Hepatic vein (veins that drain the liver) compression, inferior vena cava compression can cause (occlusion or stenosis)  of hepatic veins and/or inferior vena cava; Budd-chiari syndrome.

4. Clinical features of Infected hydatid has liver abscess.

Mass Pressure symptoms of large cyst in lungs are-

1. Cough

2. Hemoptysis- blood in cough/sputum; originated in the lungs or bronchial tubes.

3. Chest pain

4. Dyspnea

5. Rupture of cyst content in pleural cavity may cause allergic reactions ; anaphylaxis, pleural effusion and empyema; collection of pus in pleural space (space between lung and inner surface of chest wall).

Involvement of other organ causes-

1. Soft tissue swelling (muscle cyst)

2. Raised intracranial pressure and focal epilepsy (when an epileptic seizure starts in one side of the brain) in case of cerebral cysts.

3. Segment portal hypertension in case of Splenic cyst.

4. Bone pain, swelling and pathological fractures (bone cyst)

5. Pericardial effusion and Cardiac tamponade; pressure on the heart (cardiac cyst)

6. Loin pain (kidney); continuous dull ache –haematuria; blood in the urine (kidney cyst)

7. In orbital cyst – Unilateral exophthalmos and blindness.

Lab Investigation

1. CT scan- to detect cysts

2. MRI scan- to detect cysts

3. Ultrasound – to detect cysts

4. X-ray examination- to detect cysts

5. Serological test

6. If a burst hydatid cyst is suspected, examination of blood, urine, sputum, faeces or other bodily fluids

7. Blood tests for antibodies to the cysts

How Echinococcosis Occurs?

1. Dogs get infected from parasite when they ingest the organs of other animals that contain hydatid cysts. The hydatid cysts develop into adult tapeworms in the dog. Infected dogs shed tapeworm eggs in their feces which contaminate the ground or soil.

2. Sheep, goats, cattle, and pigs ingest tapeworm eggs in the contaminated soil or ground; once ingested, eggs hatch and developed and turn into cysts in the internal organs.

3. In humans usually mode of transmission to is by accidental swallowing of soil, water, or food that are contaminated by the fecal matter with tapeworm eggs of an infected dog.  Echinococcus eggs that had deposited in soil can stay viable for up to a year.

4. The eggs travel through the bloodstream, lodge in internal organs and form watery hydatid cysts full of tapeworm heads  known as hydatid disease or echinococcosis.

5. The larval form of the tapeworm may lodge in various internal organ sites where they form a fluid-filled sac (hydatid cyst). The cysts contain immature forms of tapeworm. Cysts also contain ‘daughter cysts’ when it released, may migrate to other areas of the body site.

6. Hydatid cysts are most commonly found in the liver and lungs organ, and may also occur in other organs, bones and muscles.

Treatment of Hydatid Disease

1.Drugs

Choice of drug– Albendazole

Other drugs used –  mebendazole and praziquantel

2. Used percutaneous drainage of hepatic hydatid cyst

3. Cyst puncture Chemotherapy, and PAIR Technique(percutaneous aspiration, injection of chemicals and reaspiration) effective treatments for cystic echinococcosis.

3. Surgery is the most effective treatment to remove the hydatid cyst and can lead to a complete cure.

The treatment of alveolar echinococcosis is difficult than cystic echinococcosis disease and usually requires long-term chemotherapy or radical surgery, or both.

Prevention and Control

1. Deworming all dogs/sheeps

2. Control tapeworm infection in domestic dogs – treatment with anti-tapeworm medication.

3. Wash hands with soap before eating, drinking after gardening or handling or playing with dogs or other animals

4. Proper disposal of dead sheep and viscera to preventing transmission of the parasite.

5. Do not consume any food or water that are contaminated by fecal matter from dogs.

6. Control the stary dog- make sure dogs don’t defecate in and around children play areas.

Taeniasis is also parasitic infection, caused by the tapeworm Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm).