Echinococcosis

Echinococcosis Echinococcosis, also called hydatid disease, hydatidosis, or echinococcal disease, is a parasitic disease of tapeworms of the Echinococcus type. The two main types of the disease are  cystic echinococcosis and alveolar echinococcosis Less common forms include polycystic echinococcosis and unicystic echinococcosis. The disease often starts without symptoms and this may last for years. The symptoms and signs that occur depend on the cyst's location and size. Alveolar disease usually begins in the liver but can spread to other parts of the body, such as the lungs or brain. When the liver is affected the person may have abdominal pain, weight loss, and turn slightly yellow from jaundice. Lung disease may cause pain in the chest, shortness of breath and coughing.

Classification Echinococcosis is a parasitic diseases, commonly referred to as tapeworms. Which classified as following: Phylum (Platyhelminthes) (flatworms) Class (Cestoda) Order Cyclophyllidea Family (Taeniidae) Genus (Echinococcus)

Echinococcus Species Three known species of Echinococcus are medically important: Echinococcus granulosus Echinococcus multilocularis Echinococcus vogeli Larval forms capable of developing in humans resulting in ‘hydatidosis Echinococcus granulosus - has carnivores, especially dogs and other canines as definitive hosts 

A zoonotic infestation by a tapeworm causing hydatid disease Echinococcus granulosus: Cystic echinococcosis Produces cystic lesions Echinococcus multilocularis: Alveolar echinococcosis Invasive solid lesions of firm consistency

Echinococcus granulosus Echinococcus granulosus, also called the Hydatid worm or Hyper Tape-worm or Dog Tapeworm. It is a cyclophyllid cestode that parasitizes the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes hydatid disease.

Morphology Egg: Found in dog feces Infective stage These eggs are virtually indistinguishable from other closely related species of tapeworms such as Taenia 

Morphology Adults: 3-6 mm long when mature Consists of: Head – Scolex Short neck - Strobila  Usually 3 proglottids: Immature, mature, gravid 

Scolex has non-retractable rostellum armed with double crown of 28-50 hooks

Lifecycle Dogs are the definitive hosts. Adult worm develops in the small intestine, Eggs are voided in the feces of the dogs. Sheep and other herbivores are intermediate hosts. Humans are accidental intermediate hosts Larval form develops mainly in the liver and lungs The cycle is completed when a dog eats a cyst-infested liver or lungs

Human Host Each egg contains an embryo (oncosphere). Eggs hatch in the human stomach and release the oncosphere . The oncosphere penetrate the intestinal lining and enter the blood stream. Travel to any organ, usually lung and liver, and a cyst develops.

The Hydatid Cyst The cyst is lined by a multilayer parasite tissue with the innermost layer being the germinal layer. GL can spawn the formation of “brood capsules” which are themselves lined by GL. The daughter cysts (the encircled body) into the center of the fluid-filled cyst. They will develop into tapeworms should this be eaten by a definitive or final host such as a canine 

Pathogenesis Echinococcus' main method of harming the host comes from the cysts formed by the larvae form, not by the pathogen itself. The cysts, if developed enough, will swell and put pressure on the surrounding tissues, causing eventual blood vessel obstruction and necrosis of the tissue. Additional harm may be inflicted upon rupture of the cysts can cause an allergic reaction and possible anaphylactic shock if the fluid from the cysts spreads via the blood stream to other parts of the body. These ruptures are normally caused by trauma or medical treatment 

Immunity Virulence factor (Antigen B) has also been found to alter dendritic cell maturation, skewing DC development and creating DC's that signal to CD4 T-cells to differentiate into T-helper II cells. Antigen B also alters a DC's cytokine production, decreasing the synthesis of IL-12 and TNF-α, which blocks T-helper I differentiation in favor of T-helper II.

Clinical signs After infection, an individual can be asymptomatic for several years until the hydatid cysts become large enough to trigger symptoms.  The symptoms, depend upon the location of the cyst. Large abdominal cysts produce increasing discomfort. Liver cysts cause obstructive jaundice. Peribronchial cysts may produce pulmonary abscesses. Brain cysts produce intracranial pressure and Jacksonian epilepsy. Kidney cysts cause renal dysfunction. The contents of a cyst may produce anaphylactic responses.

Leakage of fluid from the cyst (hyatid sand) causes eosinophilia.  Rupture of a hydatid cysts as a consequence of trauma or surgery is very dangerous because it can cause anaphylactic shock, Possible allergic reaction, and risk spreading hydatid sand which can give rise to new cysts throughout the body.

Diagnosis Diagnosis is usually based on results from ultrasonography imaging, validated by computed tornography or magnetic resonance imaging (MRI) scans. Biopsies can provide differential diagnosis of cysts from tumors 

Treatment 1-Treatment involves surgical removal of cyst 2-inactivation of hydatid sand by injecting the cyst with 10% formalin and its removal within few (4-5) minutes. 3-Prazequantel has been shown to be effective in many cases. 4- Albendazole, in high doses, is an alternative.  

Prevention Periodic deworming of dogs, improved hygiene in livestock slaughtering, and public education campaigns about human hygiene have been found to greatly reduce transmission and infection rates.

Echinococcus multilocularis This is a tapeworm, similar to E. granulosus, that also causes hydatid in northern parts of Asia and North America. It has a very similar morphology and life cycle except that rodents are its intermediate host. Humans, when infected with this worm, also develop hydatid cysts which produce symptoms similar to those caused by E. granulosus. However, the cysts are multilocular (many chambers).

The organism is resistant to praziquantel; high doses of Albendazole has some anti-parasitic effect. Surgery is the means of removing the cyst. Rodent control is the means of prevention