Echinococcus

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Code: p2
Latin name: Echinococcus spp.
Family: Taeniidae
Common names: Echinococcus, Hydatidosis, Echinococcosis, Hydatid disease, Cystic Hydatid disease, Alveolar Hydatid disease, Polycystic Hydatid disease
Four species of Echinococcus are generally known as parasites of man:
  • Echinococcus granulosus - Causing Cystic Hydatid disease
  • Echinococcus multilocularis - Causing Alveolar Hydatid disease
  • Echinococcus vogeli - Causing Cystic or Polycystic Hydatid disease
  • Echinococcus oligarthus - Causing Cystic or Polycystic Hydatid disease
A number of subspecies exists, each with particular preferences for the mammals it parasitises.
 
Parasite
A parasite, which may cause severe reactions in susceptible individuals.

Allergen Exposure

Geographical distribution
Echinococcus is a genus of parasitic tapeworm whose larvae infect mammals. The parasites can form large, spherical cysts (or, in the "Alveolar" forms of the disease, lesions), which cause serious or even fatal disease. Species of this tapeworm are found throughout the world, even in arctic regions. The eggs can survive freezing and drying on the ground for up to a year. The classic transmitters are dogs and other canids. The intermediate hosts, in whom cysts and lesions develop, include humans. Hydatid disease, caused by Echinococcus granulosus, is especially common in Mediterranean regions, and is severely endemic in Greece.
 
The adult parasites are tapeworms measuring between 3 and 9 mm in length and usually consisting of only 3 proglottids: an immature, a mature, and a gravid proglottid. The scolex is globular in shape, and has a prominent rostellum, armed with a double row of between 30 and 36 hooks. The eggs measure between 30 and 40µm in diameter. In the intermediate host, cysts or lesions develop during the larval stage in the internal organs, causing functional impairment which can lead to the death of the host. The rupture of a cyst can lead to severe reactions from the highly allergenic “Hydatid fluid” released.
 
Environment
The egg enters the host through the mouth, typically through the ingestion of the carrion of a previous host or grass contaminated with faeces, or in the case of humans through poor hygiene or an accident such as a dog licking the face. The eggs then hatch in the intestine, penetrate the gut wall, and travel via the lymphatic or blood system throughout the body and lodge within the body’s tissues. The cysts may develop anywhere within the body, but most commonly it is the liver. Development of the cysts to produce thousands of infective protoscolices takes approximately 1 to 2 years.
 
Cell-mediated immunity (CMI) may play a large role in suppression of larval growth (1). Sometimes the infection is asymptomatic, the only evidence being the presence of calcified cysts on autopsy after death due to an unrelated cause. Sometimes symptoms include abdominal pain in the upper right quadrant, severe itching of the skin, cough, bloody sputum, chest pain or fever. The major pathology is due to the size of the cyst (with a volume up to several litres), giving rise to pressure-related injury. A complication may arise if the cyst is ruptured due to a blow to the body, muscular strain, an operation or some other cause. In this case the contents of the hydatid are released into the body's circulatory system, and the liberated protoscolices may give rise to numerous secondary cysts throughout the body. Rupture of a hydatid cyst also commonly gives rise to anaphylactic shock.
 
Unexpected exposure
Exposure to this allergen is almost universally unexpected.
 
Allergens
No allergens from this parasite have yet been fully characterised. A protein identical to E. granulosus cyclophilin has been isolated and named EA21, and has close homology with Malassezia furfur cyclophilin allergen (Mal f 6) and with human cyclophilin. Of the 58 sera from patients with cystic echinococcosis (CE), 29 (50%) were IgE-positive to EA21, whereas, despite the high sequence homology, none were IgE-positive to Mal f 6 or human cyclophilin. Only 26 of the 58 patients (45%) had IgG that was specific to EA21, whereas all patients (100%) had IgG specific to Mal f 6 and human cyclophilin. Overall, these findings suggest that E. granulosus cyclophilin is a conserved, constitutive parasite protein that does not cross-react with cyclophilins from other organisms and is involved in the allergic symptoms related to CE (2).
 
Serum IgE-binding reactivity to Echinococcus granulosus elongation factor-1 beta/delta (EgEF-1 beta/delta) has been demonstrated by immunoblotting analysis, and was shown to differ significantly between patients with and without allergic reactions (38 of 42, or 90%, vs. 31 of 56, or 56%). EgEF-1 beta/delta induced a proliferative response in 14 of 19 (74%) patients' peripheral blood mononuclear cells (PBMC), irrespective of the allergic manifestations, and skewed Th1/Th2 cytokine activation towards a preferentially Th2 polarisation. An immunodominant epitope of 18 residues with 78% identity and 89% similarity with an IgE-immunoreactive Strongyloides stercoralis antigen was identified by epitope mapping. These findings suggest that EgEF-1 beta/delta is an allergenic molecule that may be a general marker of the intensity of CE immune response (3).

Potential Cross-Reactivity

A protein identical to E. granulosus cyclophilin has been isolated and named named EA21, and has close homology with Malassezia furfur cyclophilin allergen (Mal f 6) and with human cyclophilin. In sera from patients with cystic echinococcosis, 50% were IgE-positive to EA21, whereas, despite the high sequence homology, none were IgE positive to Mal f 6 or human cyclophilin. These findings suggest that E. granulosus cyclophilin is a conserved, constitutive parasite protein that does not cross-react with cyclophilins from other organisms (2).
 
In a study, cross-reactive specific IgE against Ascaris lumbricoides and Echinococcus granulosus could be detected, but the clinical relevance of this finding was not elucidated (4).

Clinical Experience

IgE-mediated reactions
Echinococcus infection may uncommonly induce allergy symptoms, and may commonly induce severe allergy symptoms in the event of the rupture of a cyst. Echinococcus may result in hypersensitivity as a result of delayed hypersensitivity mechanisms: therefore delayed-hypersensitivity skin tests may help in evaluating the activity of Echinococcus granulosus cysts (5).
 
A woman suffering from cystic echinococcosis of the liver consequently developed urticaria and acute generalised exanthematous pustolosis. Serum immunoglobulin (Ig)E and IgG4 specific to Echinococcus granulosus antigens were detected by immunoblotting (6).
 
A 66-year-old woman developed anaphylactic shock due to traumatic rupture of a hydatid liver cyst. This study emphasises that Echinococcus liver cysts should be suspected in cases of anaphylaxis of uncertain etiology in individuals living in Echinococcus-endemic areas (7).
 
A 25-year-old was admitted to hospital with acute right upper quadrant abdominal pain, vertigo, dyspnea, generalised urticaria and shock several minutes after eating an instant soup. Abdominal ultrasound scan revealed a multivesicular septated cystic space-occupying lesion of the right liver lobe. The study concluded that in patients from echinococcosis-endemic regions who develop an anaphylactic reaction, a ruptured Echinococcus granulosus cyst should be considered in the differential diagnosis (8).
 
During the excision of a cystic tumour of the left proximal thigh under general anaesthesia, a severe anaphylactic shock was observed in a patient (9).
 
Another case was presented of a 2-year history of recurrent anaphylactic shock, including allergic pneumonia, due to small, incomplete ruptures of hydatid cyst. The case demonstrates the potentially life-saving importance of early diagnosis of hydatid cyst (10).
 
Compiled by Dr Harris Steinman, harris@zingsolutions.com

References

  1. Playford MC, Kamiya M. Immune response to Echinococcus multilocularis infection in the mouse model: a review. Jpn J Vet Res. 1992 Sep;40(2-3):113-30
  2. Ortona E, Vaccari S, Margutti P, Delunardo F, Rigano R, Profumo E, Buttari B, Rasool O, Teggi A, Siracusano A. Immunological characterization of Echinococcus granulosus cyclophilin, an allergen reactive with IgE and IgG4 from patients with cystic echinococcosis. Clin Exp Immunol. 2002;128(1):124-30
  3. Ortona E, Margutti P, Vaccari S, Rigano R, Profumo E, Buttari B, Chersi A, Teggi A, Siracusano A. Elongation factor 1 beta/delta of Echinococcus granulosus and allergic manifestations in human cystic echinococcosis. Clin Exp Immunol. 2001;125(1):110-6
  4. Daschner A, Alonso-Gomez A, Lopez Serrano C. What does Anisakis simplex parasitism in gastro-allergic anisakiasis teach us about interpreting specific and total IgE values? Allergol Immunopathol (Madr). 2000;28(2):67-70
  5. Kacprzak E, Stefaniak J. Evaluating the activity of liver cystic echinococcosis using the delayed-hypersensitivity skin reaction to common antigens. Ann Trop Med Parasitol 1995;89(1):25-9
  6. Cannistraci C, Parola IL, RiganO R, Bassetti F, Ortona E, Santucci B, Picardo M, Siracusano S. Acute generalized exanthematous pustulosis in cystic echinococcosis: immunological characterization. Br J Dermatol. 2003;148(6):1245-9
  7. Ruiz-Castro M, Vidal-Marcos A, de Frutos S, Infante B, Ramos-Lopez MA, Sanz-Garcia M. Anaphylactic shock caused by the rupture of an unknown hepatic hydatid cyst. [Spanish] Rev Esp Anestesiol Reanim. 1997;44(8):321-3
  8. Koppen S, Wejda B, Dormann A, Seesko H, Huchzermeyer H, Junghanss T. Anaphylactic shock caused by rupture of an echinococcal cyst in a 25-year-old asylum seeker from Georgia. [German] Dtsch Med Wochenschr. 2003;128(13):663-6
  9. Heinze J, Junginger W, Muller G, Gaebel G. Anaphylactic shock during excision of an intraosseous Echinococcus granulosus cyst. [German] Anaesthesist. 1987;36(11):659-61
  10. Giulekas D, Papacosta D, Papaconstantinou C, Barbarousis D, Angel J. Recurrent anaphylactic shock as a manifestation of echinococcosis. Report of a case. Scand J Thorac Cardiovasc Surg. 1986;20(2):175-7

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.