Coenurosis
Encyclopedia
Coenurosis is a parasitic
infection
that results when humans ingest the eggs of dog tapeworm
species Taenia multiceps, T. serialis, T. brauni, or T. glomerata. There are many different tapeworm species belonging to the genus Taenia
, but these four in particular are responsible for the rare human disease, coenurosis.
It is important to distinguish that there is a very significant difference between human tapeworm infection
and human coenurosis. Humans are the definitive hosts for some tapeworm species, the most common being T. saginata and T. solium (pork and beef tapeworms). This means that these species can develop into full grown, reproductively capable adult worms within the human body. People infected with these species have a tapeworm infection. In contrast, the four species that cause human coenurosis can only grow into mature, reproductively capable worms inside their definitive hosts, canids such as dogs, wolves, foxes and coyotes. Humans who ingest eggs from any of these four species of Taenia become intermediate hosts, or places where the eggs can mature into larvae but not into adult worms. When humans ingest these eggs, the eggs develop into tapeworm larvae that group within cysts known as coenuri, which can be seen in the central nervous system
, muscle
s, and subcutaneous tissues of infected humans. People with coenurosis do not develop a tapeworm infection because the larvae of coenurosis-causing parasites cannot develop into worms inside of humans.
When the cyst occurs in the brain, as it often does, the infected individual may experience headaches, seizures, vomiting, paralysis affecting one side of the body (hemiplegia), paralysis involving one limb (monoplegia), and loss of ability to coordinate muscles and muscle movements. Many of these symptoms are due to the buildup of inter-cranial pressure from the growing cyst or from the cyst pressing on other parts of brain.
When the cyst occurs in the spinal cord, it can cause severe pain and inflammation, and loss of feeling in some nerves.
When the cyst occurs in the eyes, it causes decreased vision and headaches.
In the muscular and subcutaneous tissues, the cyst causes disfiguring nodules that can protrude out of the body. These nodules can be painful, uncomfortable, and can cause loss of muscle function.
In 1983, a 4 year old girl in the USA was admitted to the hospital with progressive, generalized muscle weakness, inability to walk, rash, abdominal pain and deteriorating neurological ability. When the doctors did a CT scan, they saw fluid filled lumps in her brain and decided to operate. While operating, coenuri were found and the patient was immediately given chemotherapy with praziquantel. Unfortunately, the coenurosis had already done too much damage in the CNS and the little girl did not survive.
The most recent North American case took place in 1994 in Los Angeles, Ca when a 39 year old man presented an enlarging mass on his back. When doctors tried to operate a large intramuscular capsule was found. The surgery was terminated and a fine needle aspiration test revealed muscular coenurosis. The man was treated with praziquantel. The drug successfully killed the larvae and his infection never returned. The cyst removed from this man is shown in the picture.
The most recent case on record to date took place in Israel in 2006. A 4 year old girl had T. multiceps in her subcutaneous tissue. She received proper treatment and made a full recovery. In all of these recent cases, the infected individuals had been exposed to wild dogs in regions where canid tapeworm is considered endemic, and probably ingested the parasite accidentally through contact with contaminated food or water.
Where are the pictures?
An important consideration in diagnosing coenurosis properly is learning about the infected person’s exposure history. If the person presenting symptoms lives in an area with poor sanitation, high wild dog population, or known endemic tapeworm, his chance of having coenurosis is much higher. Also, this disease is seen more often in children than adults because children spend time outside in the mud and generally are more likely than adults to come into contact with canid feces.
and Albendazole
. Praziquantel causes cell membranes of worms to become permeable. In this way the worm loses intracellular calcium. This in turn causes the worm to become paralyzed. Albendazole causes the worm to produce less ATP eventually leading to its death. Glucocorticoids can be used to help subdue the inflammatory symptoms of the disease.
Preventative measures can (and definitely should) be taken at community and individual levels. Communities and governments can make sure their water supply remains sanitary and free of dog feces. Communities can control wild dog populations and vaccinate dogs for tapeworm infection, thus preventing infection of the definitive host. Individuals should wash all fruits and vegetables thoroughly before eating and make sure their dogs are not infected with tapeworm.
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
that results when humans ingest the eggs of dog tapeworm
Cestoda
This article describes the flatworm. For the medical condition, see Tapeworm infection.Cestoda is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies...
species Taenia multiceps, T. serialis, T. brauni, or T. glomerata. There are many different tapeworm species belonging to the genus Taenia
Taenia (tapeworm)
Taenia is a genus of tapeworm that includes some important parasites of livestock. Members of the genus are responsible for taeniasis and cysticercosis in humans. There are more than 100 species recorded...
, but these four in particular are responsible for the rare human disease, coenurosis.
It is important to distinguish that there is a very significant difference between human tapeworm infection
Tapeworm infection
Tapeworm infestation is the infection of the digestive tract by adult parasitic flatworms called cestodes or tapeworms. Live tapeworm larvae are sometimes ingested by consuming undercooked food. Once inside the digestive tract, a larva can grow into a very large adult tapeworm. Additionally,...
and human coenurosis. Humans are the definitive hosts for some tapeworm species, the most common being T. saginata and T. solium (pork and beef tapeworms). This means that these species can develop into full grown, reproductively capable adult worms within the human body. People infected with these species have a tapeworm infection. In contrast, the four species that cause human coenurosis can only grow into mature, reproductively capable worms inside their definitive hosts, canids such as dogs, wolves, foxes and coyotes. Humans who ingest eggs from any of these four species of Taenia become intermediate hosts, or places where the eggs can mature into larvae but not into adult worms. When humans ingest these eggs, the eggs develop into tapeworm larvae that group within cysts known as coenuri, which can be seen in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s, and subcutaneous tissues of infected humans. People with coenurosis do not develop a tapeworm infection because the larvae of coenurosis-causing parasites cannot develop into worms inside of humans.
Classification and taxonomy
- Common Name: Tapeworm larvae infection.
- Kingdom: Animalia
- Phylum: Platyhelminths
- Class: CestodaCestodaThis article describes the flatworm. For the medical condition, see Tapeworm infection.Cestoda is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies...
- Order: CyclophyllideaCyclophyllideaTapeworms of the order Cyclophyllidea are the most important cestode parasites of humans and domesticated animals. All have multiple proglottid "segments," and all have four suckers on their scolex , though some may have other structures as well...
- Family: TaeniidaeTaeniidaeTaeniidae is a family of flatworms. It includes many tapeworms of medical and veterinary importance, as Taenia solium and Taenia saginata ....
- Genus: TaeniaTaeniaTaenia can refer to:* Taenia of Doric columnsIn medicine and anatomy* Taenia coli of the large intestine* Taenia thalami of the mammal brain* Taenia of fourth ventricle of the mammal brain...
- Species: multiceps, serialis, brauni, glomerata
History of Discovery
Because this disease so rarely occurs in humans, it took a long time for it to become recognized within the population, and species differentiation among the four different types is still somewhat difficult. Many cases of coenurosis probably existed years before it was recognized or discovered, but the first cases to be diagnosed were as follows:- T. multiceps: Diagnosed for the first time in 1913 in Paris, when a man presented symptoms of CNS nerve degeneration. He had convulsions and trouble speaking/ understanding speech. During his autopsy, two coenuri were found in his brain.
- T. serialis: In 1933 a French woman was proven to have coenurosis when the cyst that had been growing under her skin was extracted from her subcutaneous tissue and fed to a dog, who later developed tapeworm infection due to T. serialis.
- T. brauni is endemic only in Africa, and the first reported case of African coenurosis (which was probably this particular species) was discovered by Fain and colleagues in 1956.
- T. glomerata: Even now, it is unclear whether this species is responsible for coenurosis in parts of Africa, but it is thought to be. The first reported case caused by this species occurred in Nigeria in 1919.
Clinical Presentation in Humans
In humans, this parasitic infection causes a variety of symptoms, depending on where the cyst occurs. The tapeworm larvae group together to form fluid filled cysts in various body tissues. These cysts start out small, but as the larvae grow, the cyst can reach the size of an egg. The cysts of T. multiceps are usually between 2 and 6 cm in diameter and are most commonly found in the CNS and can contain anywhere from a few to over a hundred worm larvae within them. T serialis and T. glomerata cysts present in the CNS, muscles, or subcutaneous tissue, and T. brauni cysts occupy these same areas but occur in the eye more frequently than the other three species.When the cyst occurs in the brain, as it often does, the infected individual may experience headaches, seizures, vomiting, paralysis affecting one side of the body (hemiplegia), paralysis involving one limb (monoplegia), and loss of ability to coordinate muscles and muscle movements. Many of these symptoms are due to the buildup of inter-cranial pressure from the growing cyst or from the cyst pressing on other parts of brain.
When the cyst occurs in the spinal cord, it can cause severe pain and inflammation, and loss of feeling in some nerves.
When the cyst occurs in the eyes, it causes decreased vision and headaches.
In the muscular and subcutaneous tissues, the cyst causes disfiguring nodules that can protrude out of the body. These nodules can be painful, uncomfortable, and can cause loss of muscle function.
Transmission
The definitive hosts for these Taenia species are canids. The adult tapeworms live in the intestines of animals like dogs, foxes, and coyotes. Intermediate hosts such as rabbits, goats, sheep, horses, cattle and sometimes humans get the disease by inadvertently ingesting tapeworm eggs (gravid proglottids) that have been passed in the feces of an infected canid. This can happen from ingesting food, water or soil that has been contaminated by dog feces. The disease cannot be transmitted from one intermediate host to another, but it is still not a good idea to eat meat that presents with cystic nodules from coenurosis.Prevalence/ Endemic Regions
This disease is very rare in humans and only about 100 cases have ever been recorded. It is a more common problem in sheep and cattle and can be problematic for farmers in endemic regions of the world. Most human cases occur in developing countries such as India and Sub Saharan Africa where the dog population is not controlled or vaccinated for tapeworm, and in areas lacking proper sanitation. T. multiceps has been reported in regions all over the world (both human and animal infections) and is the most common coenurosis causing species. T. serialis has been seen in North America, Europe and Africa, and T. brauni and T. glomerata have only been seen in Africa. This disease still occurs, even in developed countries. Some of the most recent reported cases occurred in France, Italy, Israel, Canada and the United States. Some experts suspect under reporting of this disease, especially in impoverished and developing countries where reporting technologies are more difficult to obtain. The global prevalence might be much higher than present data suggest.Recent Cases
Recently (within the last 25 years), human cases have been recorded in Uganda, Kenya, Ghana, South Africa, Rwanda, Nigeria, Italy, Israel, Mexico, Canada and the United States, and animal cases have been found in many other countries as well. (9)In 1983, a 4 year old girl in the USA was admitted to the hospital with progressive, generalized muscle weakness, inability to walk, rash, abdominal pain and deteriorating neurological ability. When the doctors did a CT scan, they saw fluid filled lumps in her brain and decided to operate. While operating, coenuri were found and the patient was immediately given chemotherapy with praziquantel. Unfortunately, the coenurosis had already done too much damage in the CNS and the little girl did not survive.
The most recent North American case took place in 1994 in Los Angeles, Ca when a 39 year old man presented an enlarging mass on his back. When doctors tried to operate a large intramuscular capsule was found. The surgery was terminated and a fine needle aspiration test revealed muscular coenurosis. The man was treated with praziquantel. The drug successfully killed the larvae and his infection never returned. The cyst removed from this man is shown in the picture.
The most recent case on record to date took place in Israel in 2006. A 4 year old girl had T. multiceps in her subcutaneous tissue. She received proper treatment and made a full recovery. In all of these recent cases, the infected individuals had been exposed to wild dogs in regions where canid tapeworm is considered endemic, and probably ingested the parasite accidentally through contact with contaminated food or water.
Incubation Period
Cysts can present in humans anywhere from a few months to a few years after ingestion. Once the cyst develops, symptoms associated with the cyst develop rapidly.Morphology
The following are pictures of coenurosis cysts, some which have been surgically removed from humans and others that have been removed from animals after death.Where are the pictures?
Life cycle
The lifecycle of coenurosis goes something like this: Eggs and gravid proglottids are shed in feces into the environment by infected definitive hosts (canids). Many animals may serve as intermediate hosts, including rodents, rabbits, cattle, sheep, goats and humans. These intermediate hosts ingest the eggs. Once ingested, the eggs hatch in the intestine, releasing oncospheres. These oncospheres circulate in the blood until they lodge in suitable organs (skeletal muscle, eyes, brain, muscles or subcutaneous tissue). After about three months or so, the oncospheres develop into cystic like larvae balls called coenuri. The cycle perpetuates when a canid (definitive host) ingests the tissue of an infected imtermediate host. When this happens, the maturing larvae reside in the small intestine of the definitive host until they mature into adult worms and begin producing eggs (which will eventually be passed through feces into the environment once again).Diagnostic Tests
Because this disease is so rare in humans, accurate diagnostic techniques have not been developed. CT scans and MRI’s are useful for detecting fluid filled cysts in all areas of the body, and some serological and microscopic tests can confirm the presence of Taenia larvae once surgery has taken place and a portion of the cyst can be removed to undergo examination and biopsy. Because of the lack of specificity in diagnostic technique, coenurosis can be misdiagnosed as neurocysticercosis or echinococcosis, other parasitic diseases affecting nervous system tissue.An important consideration in diagnosing coenurosis properly is learning about the infected person’s exposure history. If the person presenting symptoms lives in an area with poor sanitation, high wild dog population, or known endemic tapeworm, his chance of having coenurosis is much higher. Also, this disease is seen more often in children than adults because children spend time outside in the mud and generally are more likely than adults to come into contact with canid feces.
Management and Therapy
The disease is more complicated and severe when the oncospheres settle in the CNS tissue. This makes operating more difficult than when the disease presents in the muscles or subcutaneous tissues. The most common and widely recognized treatment for this disease is surgical removal of the cysts. However, this is not always possible. Other treatments that have seen positive results are PraziquantelPraziquantel
Praziquantel is an anthelmintic effective against flatworms. Praziquantel is not licensed for use in humans in the UK; it is, however, available as a veterinary anthelmintic, and is available for use in humans on a named-patient basis....
and Albendazole
Albendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
. Praziquantel causes cell membranes of worms to become permeable. In this way the worm loses intracellular calcium. This in turn causes the worm to become paralyzed. Albendazole causes the worm to produce less ATP eventually leading to its death. Glucocorticoids can be used to help subdue the inflammatory symptoms of the disease.
Public Health and Prevention Strategies/Vaccines
This disease has no vaccination.Preventative measures can (and definitely should) be taken at community and individual levels. Communities and governments can make sure their water supply remains sanitary and free of dog feces. Communities can control wild dog populations and vaccinate dogs for tapeworm infection, thus preventing infection of the definitive host. Individuals should wash all fruits and vegetables thoroughly before eating and make sure their dogs are not infected with tapeworm.
External links
- ParaSites2005: Coenurosis, stanford.edu
- Coenurosis, Division of Parasitic Diseases, Centers for Disease Control & Prevention