Echinococcosis Clinical Presentation

Updated: Apr 06, 2015
  • Author: Dominique A Vuitton, MD, PhD; Chief Editor: Burke A Cunha, MD  more...
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Presentation

History

The presenting symptoms below are from two series of patients diagnosed in the same hospital in eastern France in the 1970s and 1980s. Other series confirm these figures.

Vague abdominal (right upper quadrant) pain is the most common presenting symptom (30%) and can last for years before lesions develop.

Jaundice, which was the most common presenting symptom before the 1980s, is observed in 25% of cases. Progressive gradual cancerlike onset of jaundice is observed in most cases that involve symptomatic cholestasis. Intermittent jaundice may also be associated with acute right upper quadrant pain when parasitic material migrates through the common bile duct.

Hepatomegaly is observed in 16% of cases.

In the presence of bacterial superinfection, fever and chills may accompany gallstonelike symptoms. Fever and chills may also evoke liver abscess due to superinfection in the central periparasitic necrosis.

Various symptoms, ranging from dyspnea and bile sputum to seizures and stroke, as well as bone pain or skin tumor, may be the presenting symptoms of a secondary location or metastasis of the parasitic lesions (approximately 10% of cases).

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Physical

The most frequent clinical finding is hepatomegaly, which may be found in patients who are otherwise asymptomatic. An enlarged left liver lobe due to liver regeneration in the course of a lesion on the right lobe may be found only during palpation of the epigastrium.

Splenomegaly is present only in cases complicated by portal hypertension or those that involve spleen metastasis.

Ascites and dilated periumbilical veins are rare.

Caval collateral circulation between the inferior and superior vena cava may develop on the abdominal and thoracic skin in cases in which the hepatic veins and vena cava are obstructed.

Other physical symptoms are dictated by the location of metastatic lesions.

A significant number of patients undergoing diagnostic analysis are asymptomatic. Patients may present by chance (eg, at surgery, during ultrasonographic examination for another reason) or during mass screening performed in an endemic area.

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Causes

Alveolar echinococcosis is a zoonosis. In nature, humans and other animals share the infection, which results in various factors that allow the parasite to complete its life cycle. Contact with the infectious form of the cestode (ie, oncosphere or egg) depends on human behavior and cultural habits. This explains why the disease is encountered in limited geographic areas. Changes in the environment, possibly related to economic or political decisions, and changes in behavior may be partially responsible for changes in the potential for humans to be exposed to the parasite. In general, humans are not susceptible hosts for infection with E multilocularis. In fact, genetic and immunologic aspects are also involved and may modify the overall prevalence of the disease in humans of a given endemic area.

Geographic factors

Prevalence rates vary enormously (between 1 per 100,000 and 1 per 10 population) within the recognized distribution range of E multilocularis. [5]

In most regions, environmental features that favor the parasite cycle include hilly landscapes, cool and rainy climates, and pastures for cattle breeding. [5]

One factor that is key to the presence of the parasite is the abundance of suitable intermediate hosts. The occurrence and population size of these species depends on the presence of unplowed grassland (eg, pastures, meadows), which is the type of landscape most typical in mountainous regions with a cool climate where intensive agriculture is not feasible.

A correlation between E multilocularis prevalence in foxes and population densities of rodent species (suitable intermediate hosts) has been demonstrated in France and between the prevalence in dogs and population densities of rodent or small lagomorph species in China. In addition, the number of human cases correlates well with the existence of a cyclic pattern of high densities of rodents. In Europe, high rodent population densities appear to occur only in areas without plowed fields and with permanent meadows or pastures for cow breeding.

The appearance of infected foxes in large cities, the overall increase in infected foxes in Europe and northern Japan, and the transport of infected foxes to new areas in the United States also increase the risk of human infection.

Although rodents, especially voles (see image below), or small lagomorphs (eg, Ochotona species) are the normal intermediate hosts of E multilocularis in nature, various accidental hosts with a larval disease similar to that observed in humans have been described in cattle, pigs, boars, hares, horses, monkeys, and apes.


Microtus larvalis (common vole) is one of the mos Microtus larvalis (common vole) is one of the most common intermediate hosts of Echinococcus multilocularis in Europe. Courtesy of Patrick Giraudoux, PhD.

Political factors

The European Economic Community agricultural policies that favored cow breeding for cheese-making on middle-altitude plateaus of the Jura and Alps mountain ranges since the 1960s may have led to particular changes of the landscape that are more favorable to alveolar echinococcosis development.

Similar landscape changes in central China (eg, deforestation) have led to high rodent population densities and an increase in cases of alveolar echinococcosis. In addition, on the Tibetan plateau, changes in land use, especially by fencing common pastures, may have increased the contamination risk by increasing the population of a small mammal, Ochotona curzoniae, which serves as intermediate host in this area.

Alveolar echinococcosis epidemiology is a striking example of unexpected public health consequences resulting from political or economic environmental decisions.

Human behavioral factors

Regional cultural behaviors, such as collecting wild berries or vegetables and harvesting vegetables from open kitchen gardens, put rural populations at risk. In Asia, closer contact with dogs may be responsible for the higher prevalence in women.

Other behaviors that promote infection in human populations include hiking, hunting, and consumption of organic food.

Genetic factors

A multicenter study of the HLA groups of patients with alveolar echinococcosis in France, Germany, and Switzerland suggests that HLA DR 11 is associated with protection against E multilocularis infection in humans, HLA DP 0401 is associated with susceptibility, and HLA B8, DR3, and DQ2 are associated with severe forms of infection. TAP polymorphism is also associated with alveolar echinococcosis occurrence and severity.

Similar results involving other HLA groups (because of ethnic differences) have also been observed in China.

Risk factors for alveolar echinococcosis include an agricultural occupation and a prolonged stay in an endemic area. Family cases are uncommon; however, a cluster of family cases was discovered in central China and may be due to common exposure combined with genetic characteristics of these families.

Minor genetic differences between strains within the species E multilocularis may be recognized using mitochondrial and nuclear DNA sequencing. However, these genetic differences do not seem to greatly influence infectious and growth potential of the larva.

Immunologic factors

Various states of immunosuppression (eg, HIV infection, organ transplantation, chronic autoimmune or malignant disease treated with immunosuppressive drugs, pregnancy) are associated with a faster progression of alveolar echinococcosis.

Because these immunosuppressed populations are increasing, especially the patient population treated with immunosuppressants, echinococcosis is currently observed more and more frequently as an opportunistic disease.

A recent AE registry-based analysis shows that the number of AE cases associated with therapeutic immune suppression (chemotherapy and/or biotherapeutic agents, especially anti–tumor necrosis factor [TNF]) is increasing in Europe in patients with malignant and/or chronic inflammatory diseases. AE diagnosis is problematic in such patients because of unusual presentation and imaging features, possible negative serology results, and confusion with signs and symptoms of the associated disease. [6]

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