Hydatidosis

Overview

A parasitic infection caused by a tapeworm larva called echinococci. The type and severity of symptoms is determined by the location of the infestation - the most common site for the larval cysts is the liver. The most common symptoms are due to compression of nearby organs or blood vessels due to increasing size of the cyst. The larva may incubate for months or even years

Symptoms

Depending on the location of the cyst in the body, the patient could be asymptomatic even though the cysts have grown to be very large or be symptomatic even if the cysts are absolutely tiny. If the patient is symptomatic, the symptoms that an infected patient exhibits will also depend largely on where the cysts are located. For instance, if the patient has cysts in the lungs and is symptomatic, they will have a cough, shortness of breath and/or pain in the chest. On the other hand, if the patient has cysts in the liver and is symptomatic, they will suffer from abdominal pain, abnormal abdominal tenderness, hepatomegaly with an abdominal mass, jaundice, fever and/or anaphylactic reaction. In addition, if the cysts were to rupture while in the body, whether during surgical extraction of the cysts or by some kind of trauma to the body, the patient would most likely go into anaphylactic shock and suffer from high fever, pruritus (itching), edema (swelling) of the lips and eyelids, dyspnea, stridor and rhinorrhea.

Unlike intermediate hosts, definitive hosts are usually not hurt very much by the infection. Sometimes, a lack of certain vitamins and minerals can be caused in the host by the very high demand of the parasite.

source: wikipedia

Causes

Echinococcosis, which is often times referred to as hydatid disease or echinococcal disease, is a parasitic disease that affects both humans and other mammals, such as sheep, dogs, rodents and horses. There are three different forms of echinococcosis found in humans, each of which is caused by the larval stages of different species of the tapeworm of genus Echinococcus. The first of the three and also the most common form found in humans is cystic echinococcosis (also known as unilocular echinococcosis), which is caused by Echinococcus granulosus. The second is alveolar echinococcosis (also known as alveolar colloid of the liver, alveolar hydatid disease, alveolococcosis, multilocular echinococcosis, “small fox tapeworm”), which is caused by Echinococcus multilocularis and the third is polycystic echinococcosis (also known as human polycystic hydatid disease, neotropical echinococcosis), which is caused by Echinococcus vogeli and very rarely, Echinococcus oligarthus. Although alveolar and polycystic echinococcosis are rarely diagnosed in humans and are not as widespread as cystic echinococcosis, it is important to also take them into consideration since polycystic echinococcosis is relatively new on the medical scene and is often left out of conversations dealing with echinococcosis, and because alveolar echinococcosis is a serious disease that not only has a significantly high fatality rate but also has the potential to become an emerging disease in many countries.

source: wikipedia

Prevention

As one can see from the life cycles illustrated above, all disease-causing species of Echinococcus are transmitted to intermediate hosts via the ingestion of eggs and are transmitted to definitive hosts by means of eating infected, cyst-containing organs. When thinking about transmission, it is important to remember that humans are accidental intermediate hosts that become infected by handling soil, dirt or animal hair that contains eggs. It's possible to prevent and control the spread of the disease by a health education programs, an improved water sanitation, improved hygiene and de-worming of hosts (like the red foxes for the Alveolar Echinococcosis case).

source: wikipedia

Diagnosis

Cystic Echinococcosis

In order to formally diagnose a patient with any type of echinococcosis, one must use a combination of tools that involve imaging techniques, histopathology and/or nucleic acid detection and serology. For cystic echinococcosis, imaging is the main method that is relied on for diagnosis while serology tests (such as indirect hemogglutination, ELISA (enzyme linked immunosorbent assay), immunoblots or latex agglutination) that use antigens specific for E. granulosus are used to verify the imaging results. The imaging technique of choice for cystic echinococcosis is ultrasonography since it is not only able to visualize the cysts in the body’s organs but it is also inexpensive, non-invasive and gives instant results. In addition to ultrasonography, both MRI and CT scans can and are often used although an MRI is often preferred to CT scans when diagnosing cystic echinococcosis since it gives better visualization of liquid areas within the tissue.

Alveolar Echinococcosis

As with cystic echinococcosis, ultrasonography is the imaging technique of choice for alveolar echinococcosis and is usually complemented by CT scans since CT scans are able to detect the largest number of lesions and calcifications that are characteristic of alveolar echinococcosis. MRIs are also used in combination with ultrasonography though CT scans are preferred. Like cystic echinococcosis, imaging is the major method used for the diagnosis of alveolar echinococcosis while the same types of serologic tests (except now specific for E. multilocularis antigens) are used to verify the imaging results. It is also important to note that serologic tests are more valuable for the diagnosis of alveolar echinococcosis than for cystic echinococcosis since they tend to be more reliable for alveolar echinococcosis since more antigens specific for E. multilocularis are available. In addition to imaging and serology, identification of E. multilocularis infection via PCR or a histological examination of a tissue biopsy from the patient is another way to diagnose alveolar echinococcosis.

Polycystic Echinococcosis

Similar to the diagnosis of alveolar echinococcosis and cystic echinococcosis, the diagnosis of polycystic echinococcosis uses imaging techniques, in particular ultrasonography and CT scans, to detect polycystic structures within the patient’s body. However, imaging is not the preferred method of diagnosis since the method that is currently considered the standard is the isolation of protoscoleces during surgery or after the patient’s death and the identification of definitive features of E. oligarthus and E. vogeli in these isolated protoscoleces. Although this is the main way in which PE is diagnosed, there are current studies that have shown that PCR may be used to identify E. oligarthus and E. vogeli in patients’ tissues. The only drawback of using PCR to diagnose polycystic echinococcosis is that there aren’t many genetic sequences that can be used for PCR that are specific only to E. oligarthus or E. vogeli.

source: wikipedia

Treatment

In the human manifestation of the disease, E. granulosus, E. multilocularis, E. oligarthus and E. vogeli are localized in the liver (in 75% of cases), the lungs (in 5-15% of cases) and other organs in the body such as the spleen, brain, heart and kidneys (in 10-20% of cases). In the patients that are infected with E. granulosus and therefore have cystic echinococcosis, the disease develops as a slow-growing mass in the body. These slow-growing masses, often called cysts, are also found in patients that are infected with alveolar and polycystic echinococcosis.

Cystic Echinococcosis

For simple cases of cystic echinococcosis, the most common form of treatment is surgical removal of the cysts combined with chemotherapy using albendazole and/or mebendazole before and after surgery. However, if there are cysts in multiple organs or tissues, or the cysts are in risky locations, surgery becomes impractical. For inoperable cases such as these, chemotherapy and/or PAIR (puncture-aspiration-injection-reaspiration) become alternative options of treatment.

Alveolar Echinococcosis

For alveolar echinococcosis, surgical removal of cysts combined with chemotherapy (using albendazole and/or mebendazole) for up to two years after surgery is the only sure way to completely cure the disease. However, in inoperable cases, chemotherapy by itself can also be used.

Polycystic Echinococcosis

Since polycystic echinococcosis is constrained to such a particular area of the world and is not well described or found in many people, treatment of polycystic echinococcosis is less defined than that of cystic and alveolar echinococcosis. While surgical removal of cysts was the treatment of choice for the previous two types of echinococcosis, chemotherapy is the recommended treatment approach for polycystic echinococcosis. While albendazole is the preferred drug, mebendazole can also be used if the treatment is to be for an extended period of time. Only if chemotherapy fails or if the lesions are very small is surgery advised.