1. MGH Tropical Medicine Unit
Echinococcosis
Rocío Hurtado, M.D., D.T.M & H.
MGH Tropical Medicine Unit
2015

2. Human Echinococcal (Hydatid) Disease
Caused by the larval stages of the cestode of the genus Echinococcus
CYSTIC Echinococcal disease:
E. granulosus, E. vogeli and oligoarthrus
ALVEOLAR Echinococcal disease: E. multilocularis

3. Epidemiology E. granulosus - rural grazing areas worldwide
Middle East, Mediterranean countries, Russia, China, Northern Africa and South America.
U.S. : CA, AZ, NM, UT and AK
E. multilocularis – Northern hemisphere only
E. vogeli, E. oligoarthrus – Central and South America
One of the most neglected tropical diseases, associated with >1 million disability-adjusted life years – based on DALYS should receive 1.2 million dollors in funding annually
Dark – cervid
Light – sheep and other pastoral strains

4. CYSTIC HYDATID DISEASE
E. granulosus
E. vogeli
E. oligoarthrus
The eggs can survive at least a year in the environment as they are highly resistant to environmental stress.  The eggs are vulnerable to high temperatures and desiccation however, dying in two hours under these conditions.  Egg survival time is increased in damp and cool (the eggs can survive freezing) conditions (for example near watering holes).  Once passed in the feces the eggs can be transported by the wind, water, and insects (flies).  Egg shedding in the definitive host may be cyclical and each worm can produce by sexual means up to 1000 eggs every 10 days for up to 2 years.  Each egg contains an embryo or onchosphere that serves as the infective stage.  When the eggs are voided from the canid definitive host they contaminate vegetation and are accidentally ingested by the cervid intermediate host.  Humans can be infected by ingestion of eggs acquired from contaminated food or water, from handling live canids or pelts from dead canids, or by handling canid fecal material.
In the cervid intermediate host, the eggs hatch and release tiny hooked embryos (oncospheres or larvae) once they reach the small intestine.  The embryo burrows through the wall of the intestine and enters the bloodstream, eventually lodging in an organ (liver, lungs, kidneys, brain, or bone marrow) with the lungs being the most common site. In humans the egg hatches in the duodenum, the hooked embryo penetrates the intestinal wall and is carried via the bloodstream to various organs (liver, lungs, brain, skeletal muscle, and eye) with the liver being the most common site.
In the intermediate host, once the larvae reach the organ of choice they form a metacestode or hydatid cyst.  This larval cyst is unilocular, subspherical in shape and fluid-filled, lined with an inner germinal membrane that produces brood capsules.  On the inner wall of the brood capsules, an asexual budding process which enhances infectivity and compensates for low sexual egg production occurs that produces thousands of larval tapeworms or protoscolices.  The cysts are thick walled, fluid-filled, and range in size from 2 to 30 cm in diameter.  Development of these cysts is slow as the parasite is adapted to the long-lived intermediate hosts with protoscolices developing in 1 to 2 years.
The canid definitive host is infected by eating the intermediate host organ that contains the hydatid cyst which contains the protoscolices which has the ability to grow into an adult worm.  One small cyst may contain hundreds of protoscolices and one large cyst may contain tens of thousands of protoscolices.  Following ingestion, the protoscolices develop into adult tapeworms which eventually produce eggs to complete the life cycle.

5. The hydatid cyst is usually filled with fluid (table 2)
The hydatid cyst is usually filled with fluid (table 2). The inner layer is the germinative layer that gives rise to the hydatid fluid and small secondary cysts (brood capsules), which bud internally from this layer. Fragmentation of the germinative layer and brood capsules gives rise to daughter cysts. These may develop within the original cyst or separately.
After at least 10 to 12 months following infection, protoscolices are produced within the brood capsules. Cysts may contain liters of fluid and thousands of protoscolices. Cysts containing protoscolices are fertile and can produce daughter cysts, whereas cysts without protoscolices are sterile.
External to the germinative layer is an acellular, laminated membrane of variable thickness. A host granulomatous reaction occurs around this membrane; the resulting parenchyma and fibrous tissue reaction is known as the pericyst.
The pathology resulting from E. granulosus infection varies in different geographic regions and among different populations. Among patients in Turkana, Kenya, for example, many cysts are large, unilocular, and fertile [13]. In contrast, cysts among individuals in the northern hemisphere tend to be calcified, small, and infertile [1]. Such variations could depend upon a number of factors: the time between infection and diagnosis, intraspecies variation of the parasite, and host differences (immunologic, genetic, and/or nutritional) [1].
Immunity — Intermediate and incidental hosts mount both humoral and cellular immune responses to the organism. The initial immune response occurs against the oncospheres that penetrate the gastrointestinal mucosa. Subsequently, the host mounts an immune response against the metacestode (hydatid cyst). Metacestodes have developed highly effective mechanisms for evading host defenses. The membranes and host capsule surrounding the cyst protect the E. granulosus parasite from immune destruction [14].
Other less well-defined mechanisms, including parasite-derived modulating substances such as an anticomplement factor, may also dampen the host immune response [14]. Studies have suggested that Th1 cell activation is crucial for protective immunity, whereas Th2 cell activation is associated with susceptibility to progressive hydatid disease [15].

6. The Parasite: E. granulosus
Cystic hydatid disease:
Zoonosis produced by the larval stage of the tapeworm E. granulosus
Definitive hosts: dogs and other canines
Eggs passed in feces
Ingested by suitable intermediate host (herbivores: sheep, cattle, goats, pigs, horses or camels)
Eggs hatch in their intesting, spread through portal circulation, lodge in tissues – develop into cystic metacestodes with infective protoscolices
Dog ingests viscera – infective protoscolices mature into adult tapeworms
Humans: accidental intermediate hosts
Ingesting eggs – develop into cysts years after infection
E.g. children & dogs
CE is caused by the metacestode stage
of various strains of E. granulosus, which is a cystic structure
typically filled with a clear fluid (hydatid fluid). About 5 days
after ingestion of eggs, the metacestode is a small vesicle (60 to
70 m in diameter) consisting of an internal cellular layer
(germinal layer) and an outer acellular, laminated layer. This
cyst (endocyst) gradually expands and induces a granulomatous
host reaction, followed by a fibrous tissue reaction and the
formation of a connective tissue layer (pericyst). The size of
cysts in the human body is highly variable and usually ranges
between 1 and 15 cm, but much larger cysts (20 cm in diameter)
may also occur (3, 148, 184) (Fig. 2). The exact time
required for the development of protoscoleces within cysts in
the human host is not known, but it thought to be more than 10
months postinfection. Protoscoleces can already be formed in
cysts of 5 to 20 mm in diameter (149); on the other hand, a
proportion of cysts do not produce protoscoleces and remain
“sterile.” Most of the cysts are univesicular (i.e., unilocular),
but in some of them, smaller daughter cysts are formed within
larger mother cysts. Mixed infections with metacestodes of E.
granulosus and E. multilocularis are rare,
Santivanez S, Garcia HH. Curr Opin Pulm Med 2010; 16:

7. The prevalence of Echinococcus granulosus in dogs in the Turkana District of Kenya was 39.4% of 695 examined. Of these, 98 (35.8%) had heavy Echinococcus worm burdens (10(3)-5 X 10(4) ), while 54 (19.7%) and 122 (44.5%) had medium ( ) and light (1-200) burdens. The possible sources of these infections are discussed. The prevalence rate differed in various parts of the district, ranging from 63.5% in the northwest, where the highest incidence of human hydatidosis also occurs, to nil along the shores of Lake Turkana. Infection rates of 32.0% and 16.7% were recorded at Lokitaung (north-east) and Lodwar (central), while in the south 48.9% of dogs harboured Echinococcus. This latter figure is surprising as the area has a low incidence of human hydatidosis. The Turkana keep a large number of dogs, and the reasons for this and the social role of the dog in the district is discussed. No difference in susceptibility was found between Turkana-type dogs and those of mixed breeds from Nairobi when they were experimentally infected with hydatid protoscolices from man, camels, cattle, sheep and goats. However, it proved difficult to infect the Turkana-type of dogs with viable protoscolices of cattle origin. The reasons for this and its epidemiological implications remain unclear. It is suggested that droughts, which affect Turkana every six to ten years, may play an important role in the perpetuation of hydatid disease in the area.
Eckert and Deplazes CMR 2004

8. Diversity of Strains of E. granulosus
Eckert and Deplazes, CMR 2004

9. Clinical presentation
Up to 30-60% cases asymptomatic
Clinical presentation occurs in 2 settings:
allergic/immunological phenomenon
anaphylaxis, shock
mechanical factors
impingement of vital structures
communication between cysts and organs
Laboratory findings:
dependent on site of involvement
only 15% with underlying eosinophilia

10. Clinical presentation
Incubation period - months to years
36-60% cases remain asymptomatic
Cyst growth: 1 to 5 mm per year
50% may have no change in cyst size
85-90% single organ
> 70% single cyst
Average age at presentation 36 years
Mortality 2 to 4%

11. Organ localization Liver 70% Lung 20% Bone 1% CNS 1% Cardiac 1%
Spleen %
Retroperitoneum 1%
Renal %

12. Hepatic cysts Clinical features: RUQ pain, nausea/vomiting jaundice
Complications:
biliary obstruction
Budd-Chiari
cyst rupture
secondary bacterial infection
Lung involvement in up to 25% pts

13. Biliary Complications
2 types of biliary-tree communications:
Simple communication
Frank intrabiliary rupture
Usually symptomatic
Intermittent/complete obstruction of bile duct
Obstructive jaundice, cholangitis or cholangiolytic abscesses

14. Pulmonary Hydatosis Predilection for right lung
More common in children (60%)
May be multiple and/or bilateral in 30%
Most sxs: d/t mass effect
Hemoptysis, cough, dyspnea
Complications:
cystobronchial fistulae - “salty-water, grape skin” expectoration
bronchopleural fistulae, pneumothorax, effusions or empyemas; lung abscess
direct extension through the diaphragm
bacterial superinfection

15. Pulmonary Hydatidosis - CXR
In chest radiographs, cysts
are well defined as a rounded mass of uniform density that
occupies a part of one hemithorax or both (Fig. 3). When a
cyst is broken, endocyst detachment is seen as floating
membranes within the cyst. This ‘water-lily’ or ‘meniscus’
sign denoting the entrance of air between the laminated
membrane and the pericyst through a bronchiopericystic
fistula is observed as a thin, radiolucent crescent in the
upper part of the cyst on plain radiography (Fig. 3).
Santivanez S, Garcia HH. Curr Opin Pulm Med 2010; 16:

16. Pulmonary Hydatidosis: CT
Santivanez S, Garcia HH. Curr Opin Pulm Med 2010; 16:

17. Pulmonary Disease: Dx and Rx
Diagnosis based on Radiography
CXR, CT
U/S less useful
Serology:
Decreased sensitivity unless cyst rupture
Management:
Primarily Surgical:
Parenchyma-sparing: cystostomy, intact cyst enucleation
Pneumonectomy or segmentectomy only in large, abscessed cyst
Fistula closure
Most common complication: pleural infection and prolonged air leak
Mortality 1-2%
Preop chemotherapy and consideration of postop rx:
Decreased seeding and recurrence
Surgery may involve excision of the cyst or resection
of the cyst and the immediate surrounding parenchyma.
Despite the lack of consensus, the currently most
accepted surgical treatment for pulmonary cystic echinococcosis
is complete excision using parenchymapreserving
methods, such as cystostomy, intact cyst
enucleation, or removal after needle aspiration preserving
as much lung parenchyma as possible [18,19].
Resection techniques such as pneumonectomy and segmentectomy
should be reserved for cysts involving the
whole hemithorax or the whole segment, respectively,
and lobectomy should be performed only in large
abscessed cysts. The use of presurgical chemotherapy
reduces the chances of seeding and recurrence [10].
Most surgeons use pads soaked in hypertonic saline to
protect the operatory field from spillage and subsequent
seeding of new cysts.
After removal of the cyst, the cavity should be managed
by closure of fistulas either by marsupialization or by
leaving a drain in situ to allow re-expansion of the lung
and, thus, cavity obliteration. Available data suggest that
marsupialization results in lower frequency of residual
abscesses.

18. Other sites Bone: axial pelvic pathological fractures
neurological impingement
JACCC 2014
RESULTS: We retrieved 200 publications based upon single case reports or case series, mostly from resource-poor settings. Among the 721 rural patients (22% females; median age 37 years), 60% of all reported cases were from the Mediterranean region and almost all patients were immune competent. Echinococcus granulosus was identified as the most frequent species. Most infections involved a single bone (602/721; 83%) and often the spine (321 cases; 45%). In eight cases (8/702; 1%), a secondary bacterial surgical site infection was reported. Surgical intervention was performed in 702 cases (97%), with single intervention in 687 episodes (95%). Complete excision of the lesion was possible in only 117 episodes (16%). Albendazole was by far the most frequently used agent in monotherapy with various dosages, while mebendazole in monotherapy was less frequent (32 cases). The median duration of antihelminthic therapy was 6 months (range months). There were 124 recurrences (17%) after a median delay of 2 years (range years). In multivariate analysis, the presence of visceral organ involvement increased the odds of recurrence by 5.4 (95% CI ), whereas the number of surgical interventions, the duration of antihelminthic therapy or the use of hypertonic saline did not influence recurrence.

19. Other Sites Central Nervous System: seizures, allergic reactions
present earlier in life
serology is less sensitive (+ in 20% only)
preferred rx is surgical
Central nervous system hydatid cyst disease presents with different clinical pictures depending on the involvement of cerebral and spinal structures. The majority of cerebral echinococcosis cases are in the pediatric age group, mostly involving the white matter, and their treatment is mainly surgical. Complications of this entity depend on several factors including the location, size, and multiplicity of the cysts, as well as the presence of contamination. The most common complication is a rupture of the cyst into the subarachnoid space which leads to widespread dissemination followed by severe inflammatory or anaphylactic response. However, vertebral lesions are usually invasive and cause neurological symptoms due to compression. Almost all patients complain of radicular pain and motor deficits; and up to one half of patients present with paraparesis.
The clinical findings were mostly atypical, and it was interesting that 4 patients were described as having cerebrovascular occlusive disease and 3 as having symptoms of movement disorders. Computed tomography and/or MRI techniques were extremely useful, both in reaching the correct diagnosis and for proper surgical management of hydatid disease, because of the absence of a pathognomonic clinical picture of this disease. The treatment of choice for hydatid disease of the CNS and its coverings was complete intact removal of the cyst. In contrast to that in intracranial hydatid cysts, however, surgical intervention was palliative, not curative, in almost all cases of intraspinal hydatidosis. According to this critical review of the literature, CNS hydatidosis is therefore still a life-threatening condition, in spite of all the advances in imaging techniques and therapeutic methods. The most important factors in prognosis are the localization of the focus of infection, rupture and of the cyst and dissemination of its content, and treatment modality. At present, surgical intervention preceded by careful neuroradiological evaluation remains the best surgical therapy, and this plus adjuvant chemotherapy is advocated in some cases as the gold standard for therapy.
Intracranial hydatid cysts are parasitic
infections caused by the larval stage of
Echinococcus granulosus (41) (Fig
14). The cysts preferentially affect the
liver but may also involve the lungs,
bone, and brain. Cerebral hydatid
cysts are rare, seen in only 2% of
cases (41,43). The most common location
for intracranial hydatid cysts is
the hemispheric parenchyma, particularly
in the perfusion territory of the
middle cerebral artery (41,44). The
subarachnoid spaces are another common
site of involvement.
Hydatid cysts are usually spherical,
solitary, and unilocular. They grow
slowly and are typically large, averaging
4–10 cm in diameter (45). The cysts
contain translucent fluid and may also
contain daughter cysts with an appearance
resembling small white grapes.
Protoscolices within cysts form a granular
deposit known as hydatid sand (44).
Imaging
The best diagnostic clue of a hydatid
cyst is a single, large, thin-walled,
spherical, nonenhancing CSF-attenuation
cyst in the parietal region of the
brain. Perilesional edema is usually absent.
The two visible imaging components
are the cyst and the pericyst. The
pericyst is a peripheral capsule of the
cyst. While MR imaging is more sensitive
in demonstrating the pericyst, CT is
more sensitive in depicting cyst calcification
(43). Multilocular or multiple lesions
occur but are rare (43).

20. Orbital disease
Can J Ophthalmol 2014

21. Spinal Disease Neural compression syndromes
Rx: surgical and postop medical rx
Higher rates of recurrence
Complications:
neuro & avascular necrosis
In this report, a 35-year-old male patient,
who underwent surgical and antihelmintic medical treatment
2 years previously, had a leaking cyst without neurologic
symptoms. The patient underwent excision of
multiple parasacral cysts from a posterior approach. Medical
antihelmintic treatment was used after surgery.
Results. The postoperative period was uneventful. Follow-
up MRI scans were performed at 6, 12, and 18 months
after surgery. The few residual anterior perisacral cysts
had, in fact, become smaller.
Conclusion. The recurrence period of spinal hydatid
disease may be silent without any neurologic deficits or
pain; the only clinical manifestation may be leakage from
a cyst. Curative therapies remain unlikely, but periodic
follow-up MR images are advisable for early diagnosis of
recurrence in order to obtain effective treatment.
Spine :E269–E271

22. Other sites Cardiac: 20% risk of sudden death Treatment is surgical
IVS involved in 2-9%
conduction abnormalities.
Obstructive sxs TR
ischemic syndromes
pericardial involvement
systemic rupture
20% risk of sudden death
Treatment is surgical
Ozdemir, Heart 1997; Hall, NEJM 1995; Bashour, Am Heart J 1996

24. Hall, NEJM 1995

25. Diffuse abdominal hydatid dz – middle aged woman with abdominal pain and intraabdominal mass

26. Diagnostic Studies - Radiology
1) Ultrasound % sensitive
WHO criteria
unilocular anechoic lesions with clear laminated membrane or snow like inclusions
multivesicular or multiseptated cysts with wheel-like appearance
unilocular cysts with daughter cysts
cysts with floating laminated membranes (may also contain daughter cysts)
2) CT

27. Am. J. Trop. Med. Hyg., 79(3), 2008, pp. 301–311

28. Diagnosis of Cystic Hydatid Disease
In RLS: symptomatic or complications
Usually suggested by radiographic findings
Cornerstone in endemic areas:
U/S for hepatic disease
CXR for pulmonary disease
Serological diagnosis:
Supportive
Beware of cross-reactivity and lowered sensitivity in single lesions and/or extrahepatic/pulmonary sites
The diagnosis of CE in individual patients is
based on identification of cyst structures by imaging techniques,
predominantly ultrasonography, computed tomography,
X-ray examinations, and confirmation by detection of
specific serum antibodies by immunodiagnostic tests (28, 84,
90, 114, 149, 192). For clinical practice it should be noted that
the enzyme-linked immunosorbent assay (ELISA) using crude
hydatid cyst fluid has a high sensitivity (over 95%) but its
specificity is often unsatisfactory. If purified antigens (e.g.,
antigen B) or other techniques (immunoblot analysis, detection
of immunoglobulin G4 (IgG4) antibodies, immunoelectropheresis,
etc.) are used, specificity is improved but average
sensitivity is much lower (Table 4). Furthermore, it should be
remembered that approximately 10 to 20% of patients with
hepatic cysts and about 40% with pulmonary cysts do not
produce detectable specific serum antibodies (IgG) and therefore
give false-negative results (3, 149). Cysts in the brain,
bone, or eye and calcified cysts often induce no or low antibody
responses (3).

29. Diagnostic Studies - Serology
IgG ELISA assay
sensitivity 60-94%
specificity of 90-99%
Immunoblot assay
91% sensitive
94-97% specific
Cross-reactivity - (incl. neurocysticercosis, onchocercosis, strongyloidiasis, ascariasis), malignancy and autoimmune dz
Does not distinguish between viable vs non-viable cysts

30. Management Depends on: Site Extent
Complications (eg fistula, super-infection)
Main modalities of management:
Chemotherapy
Surgery
PAIR
(ERCP)

31. Chemotherapy Response rates for med mgmt alone: 30%
Indications for medical therapy
Inoperable disease
Multiple or disseminated cysts
Peritoneal cysts
Incomplete surgery or relapse
Prevention of spread after rupture or cyst aspiration
Adjunct to invasive interventions
Agents:
Albendazole – 1st line
Praziquantel – peritoneal spillage

32. Surgery Indications for Surgery: Cure rates up to 90%
Large cysts (>10cm)
Cysts communicating with the biliary tree
Cysts near adjacent vital structures
Lung, brain, kidney, bone involvement
Cure rates up to 90%
Peri-operative mortality 2-4%
Complication rates of 2.5 to >50%
Chemotherapy at least four days pre-op, at least one month post-op 
Recurrence of liver cysts 4.5 to 25%,
Recurrence of lung disease 1.9%

33. PAIR P ercutaneous puncture with sonographic guidance
A spiration of contents
I njection with protoscolicidal agent
R easpiration
Adjunctive chemotherapy routinely administered
Indicated for approachable, uncomplicated cysts
Thus far, performed on cysts involving liver, abdominal cavity, spleen, kidney
Cure rates (usually defined radiographically) up to 75-90%
Recurrence rates - 3-4% yet limited long term f/u
Long-term outcome is not as well established given the relatively recent introduction of this procedure
Comparative trials with surgery
Smego et al. CID 37;
Khuroo et al NEJM 1997;337:881-7

34. Role of ERCP Diagnostic tool Management tool:
Obstructive jaundice or cholangitis
Minor communications vs hydatid membranes in the duodenum or impacted in the papilla of Vater
Management tool:
Sphincterotomy with cyst/membrane removal
Nasobiliary drain for acute cholangitis
Don’t forget to examine biliary fluid
Post-operative role: esp with external biliary fistula, sphincter of Oddi stenosis and sclerosing cholangitis

35. NEOTROPICAL Echinococcosis
E. vogeli & E. oligoarthrus: Central & South America
Wild felids (D.H.) &
pacas (I.H.)
E. vogeli is perpetuated in a life cycle with the bush dog
(Spoethos venaticus) as the natural definitive host and pacas
(Cuniculus papca) and agoutis (Dasyprocta spp.) as intermediate
hosts (Fig. 10). Adult cestodes have also been found in one
naturally infected domestic dog, and dogs could be experimentally
infected (158). Intestinal stages of E. vogeli apparently do
not develop in cats or in other felids.

36. Polycystic Echinococcosis
In addition to endogenous proliferation – E. vogeli has capacity for exogenous proliferation
E. oligoarthrus: only endogenous proliferation
Diagnosis: radiographic and serological
Management:
surgery reserved for smaller lesions
Biliary drainage
After failure of chemotherapy
Prolonged chemotherapy used
After growth and proliferation in the liver,
cysts may penetrate the liver capsule and continue exogenous
proliferation in the peritoneal cavity, eventually affecting various
abdominal and chest organs such as the omentum, spleen,
pancreas, diaphragm, intercostal muscles, pericardium, and
lungs (32, 157). Penetration of the diaphragm, with subsequent
cyst development in the pleural cavity and in the lungs, has
been observed in experimentally infected gerbils (157). The
exogenous proliferation of the E. vogli metacestode accounts
for its considerable pathogenicity in other hosts than natural
intermediate hosts, including humans and nonhuman primates
(157). Single cysts usually vary in diameter between 0.5 and 6
cm, but larger cysts (15 cm) may also occur (146). Cyst
aggregates can attain much larger dimensions: in one case, a
total of 2 kg of cysts was surgically excised (32). Caseous
degeneration, partial necrosis, and calcifications of cyst masses
have been observed in several patients (32).
Treatment. Because of the high risk of surgical intervention
in advanced cases of PE (see above), it has been recommended
to consider chemotherapy with albendazole as the first treatment
option. Surgery should be performed when the lesions
are small, when biliary drainage is required, or when chemotherapy
has failed (32). Experience with albendazole treatment
of PE is limited but has shown some promising results. In one
study, six patients were treated with 10 mg/kg of body weight
per day, either continuously for 3 to 8 months or in several
cycles. Reduction in cyst size or disappearance and clinical
improvement were observed in four patients and clinical improvement
alone was observed in two patients after a follow-up
period of 10 to 30 months. Side effects were generally minor
(32, 139). Studies of inoperable cases of AE have shown that
long-term treatment over several years or life-long with mebendazole
(or albendazole) is needed to achieve improvement
or stabilization of the disease in the majority of cases (4).
Knapp et al EID 2009

37. Alveolar Echinococcosis
E. multilocularis: 5 segments
Transmission: sylvatic cycle
Foxes (artic and red); wolves, wild canids: definitive hosts
Intermediate hosts: rodents (voles, lemmings, gerbils
Humans: acquire by ingesting eggs via contaminated food or water
E.g. poorly washed strawberries
Incbation:
5-15 years
Liver Involvement: >90% cases
Metacestode stage: alveolar structure with several small vesicles
Exogenous tumor-like proliferation
No pericystic membrane
The cyst of E. multilocularis differs from that of E. granulosus in that it grows by external budding of the germinal membrane with progressive infiltration of the surrounding tissue. This growth gives rise to an amorphous multicystic or semisolid structure that has been described as either multilocular or alveolar

38. Alveolar Echinococcosis
Infiltrative disease
Presentation:
Abd pain, fever, weight loss
Advanced stage: hepatic dysfunction & portal hypertension
Mortality 90% if untreated
Diagnosis: radiographic, serologic, histopath
Treatment: radical surgical resection – early
Chemotherapy >2 yrs to lifelong
Success rates: 55-74%
(i) Surgery. The first-choice treatment in all operable cases
is radical resection of the entire parasite lesion(s) from the
liver and other affected organs by using procedures of radical
tumour surgery (3, 113, 149, 221). Radical surgery is possible in
virtually all cases diagnosed in an early stage but in only 20 to
40% of the advanced cases (3, 113, 178, 221). It may lead to
complete cure, but resection is often incomplete because of
diffuse and undetected parasite infiltration into host tissues.
Therefore, according to WHO recommendations, postsurgical
chemotherapy should be carried out for at least 2 years
Recurrence can occur out to 15 yrs

39. Control of Hydatid Disease
Cystic Disease:
Control in domestic canids can be accomplished by preventing the availability of hydatid-infected offal:
do not feed dogs carcasses or allow them to scavenge
regular worming regiment with Praziquantel
Alveolar echinococcosis:
Parasite control by substantially reducing intermediate
host density (rodents) or by large-scale fox culling
Anthelminthic baits for foxes: monthly praziquantel
Longer lasting control
Control of the parasite in wild canids is not feasible.  Control in domestic canids can be accomplished by preventing the availability of hydatid-infected offal (do not feed dogs carcasses or allow them to scavenge) and a regular worming regiment with Praziquantel or Arecoline.  A vaccine has not been developed for canids
Control of the parasite in livestock is possible through the use of a vaccine that has been developed utilizing a protein contained within the parasite's egg.  The vaccine has not been successful in cervids
Prevention of E. granulosus in humans can be accomplished primarily through education and proper hygiene.  Eggs can be ingested either from handling a canid (either alive or dead) that may have eggs on its fur or by handling canid fecal material.  Examination procedures of either animals or fecal material poses a risk of infection and potentially fatal disease to humans but this can be minimized by appropriate safety measures.  Laboratory materials should be frozen at -80 degrees C for 48 hours.  A disposable face mask, gloves, and coveralls should be worn whenever handling animals or fecal material.  Contaminated material must be destroyed by heat as chemical disinfection is not reliable. 
There are no precautions that need to be taken when handling tissue of the intermediate hosts as the lung cysts are not infective to humans. 

40. Summary
CYSTIC:
Hydatid disease occurs world-wide, in particular among rural communities
Sheep-dog (herbivore – canid cycle)
Liver > lung – beware of complications
Diagnosis: clinical/radiographic/serologic
Management depends on site, extent of disease and complications
ALVEOLAR:
Infiltrative, tumor-like
Surgical resection & prolonged chemotherapy