Difference between revisions of "Echinococcus multilocularis"

Latest revision as of 15:00, 6 July 2012

Echinococcus multilocularis
Kingdom	Animalia
Phylum	Platyhelminthes
Class	Cestoda
Sub-class	Eucestoda
Order	Cyclophyllidea
Family	Taeniidae
Genus	Echinococcus
Species	E. multilocularis

Also known as: Dwarf fox tapeworm

Overview

Rat infected with E. multilocularis - Dr. I. Kagan

E. multilocularis is not present in the UK but is endemic in central Europe and North America. It is zoonotic and so presents a major health problem in Europe (including Switzerland where urban foxes are now infected) having spread from 4 countries in the 1980s to being found in 12 countries now. This has been attributed to the anti-rabies campaign which has increased the number of foxes which are commonly found as the definitive host. Humans can act as intermediate hosts if eggs are ingested causing the formation of hydatid cysts in the liver, these rapidly invade the liver and are inoperable.

Characteristics

E. mulitlocularis is a relatively small tapeworm between 2-4mm as an adult.
Scolex

2 rows of hooks
4 suckers

Proglottid

Between 3 - 5 segments in total
Terminal proglottid forms 1/2 the length of the mature worm
1 proglottid shed per week
Has single genital pore

Eggs

200-300 eggs per mature proglottid
30-40μm in diameter
Striated shell
Hooks visible on oncosphere

Life Cylce

E. multilocularis has a typical cestode life cycle involving the formation of a metacestode cyst in the intermediate host before developing to adulthood in the definitive host. The definitive host for E. multilocularis is most commonly the dog, though it has also been seen in the cat. Epidemiologically the most important definitive host in the spread of the disease is the fox. E. multilocularis mainly uses small rodents such as voles, mice and rats as an intermediate host, forming multilobular hydatid cysts in the liver of the host. The short life span of the intermediate host species is the reason for the rapid growth of the cyst, even in longer lived host like humans. This is the stage that generally causes pathology in the host animal and can be fatal.

Epidemiology

E. mulitilocularis is found throughout the northern hemisphere, originally its primary range was the tundra of northern Russia and eastern Europe. The prevalence of this worm is increasing to encompass many urban areas which increases the risk of zoonotic infection. The parasites definitive host in the wild is the red fox and the arctic fox. In North America and Europe there is an increasing presence of red foxes in urban and suburban areas, this increases the risk of infection of both humans and pets. The disease it causes is called Alveolar Hydatid Disaese.

Treatment and Control

Control involves treatment of definitive hosts, dogs and cats, with anthelmintics in order to remove adult worms from the host. The treatment of intermediate host pets (and humans) is not routine and can be dangerous as due to the infiltrative nature of the hydatid cyst and its metastatic ability. Surgical removal of the cyst is therefore not advisable.

Echinococcus multilocularis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Cestode Flashcards
Literature Search Search for recent publications via CAB Abstract (CABI log in required)	Echinococcus multilocularis publications since 2000

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-{{unfinished}}
+{{OpenPagesTop}}
+{{Taxobox
-{{toplink
+|kingdom            =Animalia
-|backcolour =
+|phylum             =Platyhelminthes
-|linkpage =Parasites
+|class              =[[:Category:Cestodes|Cestoda]]
-|linktext =PARASITES
+|sub-class          =Eucestoda
-|pagetype=Bugs
+|order              =[[:Category:Cyclophyllidea|Cyclophyllidea]]
-|sublink1=Taeniidae
+|super-family       =
-|subtext1=TAENIIDAE
+|family             =[[:Category:Taeniidae|Taeniidae]]
+|sub-family         =
+|genus              =Echinococcus
+|species            =''E. multilocularis''
 }}
-<br>
+Also known as: '''''Dwarf fox tapeworm
-== Hydatid Disease (''Echinococcus granulosus'') ==
+==Overview==
-[[Image:Echinococcus granulosus.jpg|thumb|right|150px|Echinococcus granulosus scolex - Wikimedia Commons]]
+[[Image:Rat infected with E. multilocularis.jpg|thumb|right|150px|Rat infected with ''E.  multilocularis'' - Dr. I. Kagan]]
-[[Image:E.granulosus life cycle.jpg|thumb|right|150px|E. granulosus life cycle - Wikimedia Commons]]
+''E. multilocularis'' is not present in the UK but is endemic in central Europe and North America. It is zoonotic and so presents a major health problem in Europe (including Switzerland where urban foxes are now infected) having spread from 4 countries in the 1980s to being found in 12 countries now. This has been attributed to the anti-rabies campaign which has increased the number of foxes which are commonly found as the definitive host. Humans can act as intermediate hosts if eggs are ingested causing the formation of hydatid cysts in the liver, these rapidly invade the liver and are inoperable.
-''Echinococcus granulosus'' is an important zoonosis as its metacestode, the hydatid cyst, can develop in humans, as well as in many other animals. The hydatid cyst can grow to the size of a ping-pong ball in sheep, a tennis ball in horses, and a football in man. The metacestode of the related ''Echinococcus multilocularis'' (the alveolar cyst) is even more dangerous, but fortunately does not occur in the UK.
+==Characteristics==
+''E. mulitlocularis'' is a relatively small tapeworm between 2-4mm as an adult.<br>
+'''Scolex'''
+*2 rows of hooks
+*4 suckers
+'''Proglottid'''
+*Between 3 - 5 segments in total
+*Terminal proglottid forms 1/2 the length of the mature worm
+*1 proglottid shed per week
+*Has single genital pore
+'''Eggs'''
+*200-300 eggs per mature proglottid
+*30-40μm in diameter
+*Striated shell
+*Hooks visible on oncosphere
-=== Life-Cycle ===
+==Life Cylce==
-The final host of ''E. granulosus'' is the dog, fox or other canid. There may be several thousand adult tapeworms in an infected animal. Each adult is less than 0.5cm long with only 3 or 4 segments. The scolex is deeply buried in an intestinal crypt, so microscopic inspection of a mucosal scraping is necessary to detect infection. The prepatent period of ''E. granulosus'' is 6-7weeks. No more than one gravid segment is passed by each tapeworm each week. This species therefore has a low biotic potential. The intermediate host is infected by swallowing the eggs. These are half the size of a strongyle egg, and are morphologically indistinguishable from other taeniid eggs.
+''E. multilocularis'' has a typical [[Cyclophyllidea Life-Cycle|cestode life cycle]] involving the formation of a metacestode cyst in the intermediate host before developing to adulthood in the definitive host. The definitive host for ''E. multilocularis'' is most commonly the dog, though it has also been seen in the cat. Epidemiologically the most important definitive host in the spread of the disease is the fox. ''E. multilocularis'' mainly uses small rodents such as voles, mice and rats as an intermediate host, forming multilobular hydatid cysts in the liver of the host. The short life span of the intermediate host species is the reason for the rapid growth of the cyst, even in longer lived host like humans. This is the stage that generally causes pathology in the host animal and can be fatal.
-The metacestode of ''E. granulosus'' is the hydatid cyst. These can develop anywhere in the body, but are most frequently found:
+==Epidemiology==
+''E. mulitilocularis'' is found throughout the northern hemisphere, originally its primary range was the tundra of northern Russia and eastern Europe. The prevalence of this worm is increasing to encompass many urban areas which increases the risk of zoonotic infection. The parasites definitive host in the wild is the red fox and the arctic fox. In North America and Europe there is an increasing presence of red foxes in urban and suburban areas, this increases the risk of infection of both humans and pets. The disease it causes is called Alveolar Hydatid Disaese.
-*sheep: liver and lungs
-*cattle: lungs
+==Treatment and Control==
+Control involves treatment of definitive hosts, dogs and cats, with anthelmintics in order to remove adult worms from the host. The treatment of intermediate host pets (and humans) is not routine and can be dangerous as due to the infiltrative nature of the hydatid cyst and its metastatic ability. Surgical removal of the cyst is therefore not advisable.
-*horse: liver
+{{Learning
+|flashcards = [[Cestodes_Flascards|Cestode Flashcards]]
-*human: 70% liver, 20% lungs, 10% other sites
+|literature search =[http://www.cabdirect.org/search.html?rowId=1&options1=AND&q1=%22Echinococcus+multilocularis%22&occuring1=title&rowId=2&options2=AND&q2=&occuring2=freetext&rowId=3&options3=AND&q3=&occuring3=freetext&publishedstart=2000&publishedend=yyyy&calendarInput=yyyy-mm-dd&la=any&it=any&show=all&x=43&y=8 ''Echinococcus multilocularis'' publications since 2000]
+}}
-=== Prevalence in the UK: ===
-*human: about 100 new cases of hydatidosis are diagnosed in Britain each year, with 5-10 fatalities occurring. Somw cases are contracted overseas, but endemic “hotspots” occur in Britain, particularly in parts of Wales and some Scottish islands.
-*sheep: there is great regional variation. Up to 98% of slaughtered ewes are infected in some localities.
-*horses and cattle: up to 10% are infected in some areas.
-=== Epidemiology ===
-''E. granulosus'' has a wide host range and displays great evolutionary plasticity – that is, strains with different biological properties develop readily, each adapted to a particular ecological niche. Extreme examples include dingo-wallaby, wolf-moose and hyena-human cycles. Two strains are recognised in Britain:
-) Dog-sheep strain: infective for cattle and human (not found in Ireland). Dogs become infected if a) fed infected offal, or b) by scavenging dead sheep in hills or on road-side. Sheep dogs are most likely to defaecate in fields around homestead – eggs deposited in faeces and spread across pasture by rain splash, insect activity etc. = sheep become infected when flock brought down for lambing, dipping etc. Humans are infected when eggs from dogs are accidentally ingested (this is normally the only route of infection for humans.
-) Dog-horse strain: more host-specific (in intermediate host) than sheep strain. The horse strain does occur in Ireland, but no human cases reported there – this provides circumstantial evidence that this strain may not be infective for humans. Hunt kennels have been particularly important in dissemination of the horse strain.
-=== Principles of Control ===
-''E. granulosus'' has been eradicated from New Zealand, but this took greater than 20years of intensive effort. Schemes are well advanced in several other countries, but not the UK. To make progress, the following steps must be implemented:
-) Define local epidemiology and collect base-line statistics
-) Registration of all dogs
-) Regular treatment of all dogs (initially at 6week intervals; praziquantel is currently the only suitable drug available – because it is the only drug that kills both adult and immature Echinococcus)
-) Intensive educational programme aimed at farmer and dog owner
-) Regular testing of all dogs to monitor progress and identify non-compliance (the old arecoline purge technique is being replaced by serology or copro-antigen detection)
-) Ensure dogs do not get access to raw offal: meat inspection; burial of carcasses
-) Boiling or freezing offal used for dog food
+{{review}}
-) Legislation to enforce compliance
-== Alveolar Hydatid Disease (''E. multilocularis'') ==
-[[Image:Rat infected with E. multilocularis.jpg|thumb|right|150px|Rat infected with ''E.  multilocularis'' - Dr. I. Kagan]]
-This parasite does not occur in the UK. It is largely restricted to forest areas of central Europe (including Switzerland where urban foxes are also infected) and North America. It is a significant public health problem and is spreading across Europe, where 12 countries are now affected compared with four in the 1980’s. The metacestode is the alveolar (or multilocular) cyst. Human infections are particularly dangerous as daughter cysts bud off externally as well as internally from the germinal layer so that the cyst rapidly infiltrates the liver like an invasive tumour, and is inoperable. Dogs, and to a lesser extent cats, can become infected with the adult tapeworm, but the main epidemiological cycle involves the fox as the final host and microtine rodents (particularly voles) as intermediate hosts. The latter have a very short life-span – hence the rapid growth-rate of the alveolar cyst in intermediate hosts, including humans. The anti-rabies campaign in Europe has led to a large increase in the number of foxes and, consequently, of infected rodents.
+{{OpenPages}}
+[[Category:Taeniidae]]
+[[Category:Zoonoses]]
-''Echinococcus granulosus'' in [[Peritoneal Cavity Parasitic - Pathology|Peritoneal Cavity Parasitic]] and [[Muscles Inflammatory - Pathology#Cestodes|muscles]]
+[[Category:Expert_Review]]
-[[Category:Cestodes]]