Parasitic worms that infest the intestines are a common problem. Most of us know of parasites like the pork or beef tapeworms that live in the intestines where they feed and grow within the bowels for years or even decades. Some lesser known tapeworm infestations can be much more serious and deadly within months of consuming contaminated food or water and it my be transmitted by animals that people come into contact with, like dogs and foxes.
What is the Echinococcus parasite?
The Echinococcus parasite is a tapeworm that belongs to the Cestode family of helminths (worms) like the pork and beef tapeworm. Infection with the Echinococcus worms is known as echinococcosis and it is uncommon when compared to taeniasis (pork or beef tapeworm infection). The Echinococcus tapeworm mainly grows in the liver but can also form in the lungs, bones, brain, kidneys, spleen and even the muscles.
It causes the formation of a growth (tumor) that may at times be mistaken for a malignant growth (cancer). The Echinococcus growth is a cyst, also known as a hydatid cyst, and not cancer. Although uncommon in the United States, echinococcosis is more often seen in parts of Africa, Asia, South America and Europe. Travelers to these areas that consume contaminated food or water can also be at risk.
Read more on tapeworm infection.
Types and Spread
There are broadly two types of echinococcosis:
- Cystic echinococcosis which is caused by Echinococcus granulosus, also sometimes referred to as the dog tapeworm.
- Alveolar echinococcosis which is caused by Echinococcus multilocularis, also sometimes referred to as the fox tapeworm.
Cystic echinococcosis (CE) is transmitted to humans by dogs. It is more likely to occur in dogs that eat the offals of livestock (pigs, goats, cattle and sheep) which were infected and had cysts in their organs. The tapeworms mature into the adult form within the dog and its eggs are passed out in the dog feces. Soil, water or even food contaminated with the dog’s feces may be ingested by humans who then become infected.
Cystic echinococcosis is caused by Echinococcus granulosus. It is found in Africa, Asia, Europe, the Middle East, Central and South America. It takes several years for the cyst to reach full maturity in the human body. The hydatid cyst may be found in several organs but the liver and lungs are the more common locations. Sometimes Echinococcus granulosus cysts may be found in the heart, kidneys, spleen, bones, brain and/or eyes.
Alveolar echinococcosis is also spread to humans by dogs but also by foxes, wolves and coyotes. In some countries cats may also be involved as well. Foxes appear to be the main host. As with cystic echinococcus, these animals pass out the tapeworm eggs in its feces. The livestock mentioned above can be intermediate hosts but it appears that most of the time these animals ingest the tapeworm cysts from rodents that they may feed on.
Alveolar echinococcosis is caused by Echinococcus multilocularis. This parasite is found throughout the world with it being more common in parts of Asia, northern Europe and North America. Echinococcus multilocularis does not mature into cysts in the human body like Echinococcus granulosus. Instead it forms vesicles in the organs where it destroys health tissue. The liver is more commonly infected but the lungs and/or brain may also be involved.
Read more on the brain tapeworm.
Signs and Symptoms
Echinococcus infection usually does not present with any symptoms for years and even decades. Signs and symptoms only become apparent when the cyst grows large or vesicles destroy significant areas of healthy tissue. However, the symptoms at this point are non-specific and may be initially mistaken for a host of other conditions. Signs and symptoms of echinococcosis includes:
- Discomfort and pain (located in the area of the infected organ)
- Fever and chills
- Nausea and vomiting (mainly in cystic echinococcosis)
- Malaiase and weight loss (mainly in alveolar echinococcosis)
- Coughing and bloody sputum
- Chest pain
- Jaundice (yellowing of the skin and eyes)
- Itchy skin (usually severe)
- Enlarged liver (hepatomegaly)
The collection of symptoms present and its severity depend on a host of factors, like where the cyst or vesicles develop. For example, an enlarged liver may occur without any other symptoms. Given some of these symptoms it is not uncommon for other conditiosn like tuberculosis (TB) or metastatic cancer to be suspected.
Treatment of Echinococcus
Cystic echinococcosis is more common and usually not as severe as alveolar echinococcosis. However, both infections can be deadly if not diagnosed and treated promptly. Treatment mainly involves the use of medication:
- Anthelmintic drugs (antiparasite drugs) like mebendazole and albendazole.
- Antibiotics and antifungal agents for secondary infection with bacteria or fungi respectively.
Surgey is the other option for treating echinococcosis. Sometimes this may be the first treatment option of choice where an entire cyst can be removed. Other invasive procedures include cyst punch and PAIR (percutaneous aspiration, injection of chemicals and reaspiration). Surgey for alveolar echinococcosis is difficult and involves removing part of the infected organ. Sometimes a liver transplant is required in severe cases.
Prevention of Echinococcosis
Prevention should always be a key focus among high risk individuals. For example, people living, working or travelling through areas where there is possible contact with wild animals like foxes or wolves are at a greater risk, as are people who may come into contact with dogs that feed on livestock offals. Livestock farm workers, dog handlers especially in rural areas, professional hunters or fur trappers may therefore be considered to be high risk individuals.
Prevention strategies may include:
- Wash hands thoroughly with soap and water after handling soil in high risk areas or when making contact with dogs and wild animals.
- Avoid contact with wild animals such as foxes, wolves and coyotes as far as possible. Remember the soil and natural water sources in the area may be contaminated.
- Do not feed livestock offals or rodents to dogs. This applies to sheep in particular. Ideally home slaughter of sheep should be avoided as far as possible.
- Ensure that animals do not come in close contact with food and water for human consumption. If in doubt, it is better to discard the food and water.