Coenurosis

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Different forms of coenurus in sheep and rabbits and an adult worm Coenurus.jpg
Different forms of coenurus in sheep and rabbits and an adult worm

Coenurosis, also known as caenurosis, coenuriasis, gid or sturdy, is a parasitic infection that develops in the intermediate hosts of some tapeworm species (Taenia multiceps, [1] T. serialis, [2] T. brauni, or T. glomerata). It is caused by the coenurus, the larval stage of these tapeworms. The disease occurs mainly in sheep and other ungulates, [3] but it can also occur in humans by accidental ingestion of tapeworm eggs.

Contents

Adult worms of these species develop in the small intestine of the definitive hosts (dogs, foxes and other canids), causing a disease from the group of taeniasis. [4] Humans cannot be definitive hosts for these species of tapeworms.

History

The texts of Hippocrates describe a nervous disease of sheep consistent with the symptoms of gid, comparing its symptoms to epilepsy and describing the accumulation of bad-smelling fluid in the brain. [5] [6] However, it was only in the 1600s that clearer behavioural and necropsy descriptions were recorded, including the chacteristic brain cysts and early surgical methods of removal. [7] The cause of these cysts was identified as an animal parasite in 1780 by Nathanael Gottfried Leske and Johann August Ephraim Goeze. [6] [7] It was shown that the parasite could be transferred across species to and from dogs by Karl Theodor Ernst von Siebold and Friedrich Küchenmeister in the 1850s and the species was identified as Taenia multiceps (then called Coenurus cerebralis) in 1890. [7]

Coenurosis in humans is rare and was not diagnosed until the twentieth century, with the first recorded cases by each Taenia species being: T. multiceps in 1913, [8] T. glomerate in 1919, [9] T. serialis in 1933, [8] and T. brauni in 1956. [9]

Life cycle

The eggs of T.multiceps, T. glomerate, T. serialis, and T. brauni are shed in the feces of infected hosts into the environment. [10]   The eggs are then ingested by an intermediate host, where the eggs hatch in intestines and release oncospheres. [10] Oncospheres are the larval form of tapeworms that contain hooks for attaching to the host’s tissues. [11] The oncospheres continue to move through the bloodstream of the intermediate host until they find suitable organs to inhabit. [11] The oncospheres can bind to the eyes, the brain, skeletal muscle, and subcutaneous tissue. Once the oncospheres reach their destination, they take about three months to develop into coenuri. [10] Coenuri are white, fluid filled structures that are 3-10 centimeters in diameter. [12] Coenuri have a collapsed membrane and several protoscolices on the interior. [12] The coenuri cysts found in the central nervous system have multiple cavities, and those that are not have only one cavity. [12] The disease is transferred to the definitive host when the host digests the tissue of the intermediate host. Next, eggs hatch in the intestine of the definitive host and circulate in the bloodstream until they reach suitable organs. [10]

Symptoms and diagnosis

The symptoms for coenurosis vary depending on where the cyst is located.[ citation needed ]

Prevention and treatment

In sheep, the usual treatment is surgical trepanation to remove the brain cyst, one of the few economically viable surgeries in farm animals. [5] [13] The site of the cyst can usually be estimated based on the neurological symptoms and skull thinning. [5] Treated sheep typically regain sufficient function to rejoin the flock [5] and necropsy indicates that the site of the cyst collapses and scars, relieving pressure on the brain. [14]

In the rare cases where a human is infected, both surgical and pharmaceutical treatments are available. [15] Since the disease is so uncommon in humans, no vaccine has been developed for it. [15]

Epidemiology

Hosts

The definitive hosts for coenurosis are dogs, foxes, and other canids. [16] The intermediate hosts for coenurosis can vary depending on the Taenia spp. In T. multiceps, sheep are the intermediate hosts, but goats, cattle, horses, and antelopes are also common hosts. [16] T. multiceps can affect any tissue, but it normally targets the brain in animal hosts. In T. serialis, rabbits and rodents are the intermediate hosts. [16] T. serialis commonly targets subcutaneous and intramuscular tissue. In T. brauni and T. glomerata, gerbils are the intermediate host. T. brauni and T. glomerate larvae tend to inhabit the muscles. Intermediate hosts can be infected with either chronic or acute coenurosis. [16]   Chronic coenurosis is the more common form, and it occurs primarily in young sheep.[ citation needed ]

In wild animals

Although coenurosis is more commonly associated with domestic animals, it has also been documented in wildlife, such as in mountain ungulates in the French Alps. It is believed that the ungulates are being contaminated by infected sheep. Understanding how this disease is transmitted from sheep to wild animals is important in managing the spread of this potentially dangerous zoonotic disease. A potential management strategy would be for farmers to dispose of animal carcasses found on their land. In Ethiopia, gelada monkeys with coenurosis were found to have higher mortality and lower reproductive success. [17] [18]

See also

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<i>Taenia</i> (tapeworm) Genus of flatworms

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<i>Echinococcus multilocularis</i> Species of flatworm

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<span class="mw-page-title-main">Cestoda</span> Class of flatworms

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<span class="mw-page-title-main">Coenurosis in humans</span> Medical condition

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An oncosphere is the larval form of a tapeworm once it has been ingested by an intermediate host animal. The intermediate host must ingest the tapeworm's eggs either in food or water-- once this has happened, the eggs hatch and develop into oncospheres which will then burrow through the gut wall of the intermediate host in order to access the organs or tissues of that host where they will continue the next stage of their development as cysticerci or bladderworms. The bladderworm is a cyst created by the oncosphere. In order to become an adult tapeworm, a cysticercus must then be consumed by its definitive host and establish itself by anchoring in that host's digestive tract. From there, the worm will grow in length and eventually produce proglottids which will exit the intestinal tract with other waste material and then burst, releasing the worm's eggs and completing the cycle.

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<span class="mw-page-title-main">Cysticercus</span> Larval tapeworm

Cysticercus is a scientific name given to the young tapeworms (larvae) belonging to the genus Taenia. It is a small, sac-like vesicle resembling a bladder; hence, it is also known as bladder worm. It is filled with fluid, in which the main body of the larva, called scolex, resides. It normally develops from the eggs, which are ingested by the intermediate hosts, such as pigs and cattle. The tissue infection is called cysticercosis. Inside such hosts, they settle in the muscles. When humans eat raw or undercooked pork or beef that is contaminated with cysticerci, the larvae grow into adult worms inside the intestine. Under certain circumstances, specifically for the pork tapeworm, the eggs can be accidentally eaten by humans through contaminated foodstuffs. In such case, the eggs hatch inside the body, generally moving to muscles as well as inside the brain. Such brain infection can lead to a serious medical condition called neurocysticercosis. This disease is the leading cause of acquired epilepsy.

<i>Echinococcus vogeli</i> Species of flatworm

Echinococcus vogeli is a small cyclophyllid tapeworm found in Central and South America. E. vogeli, as well as other members of the genus Echinococcus, produce a disease called echinococcosis. Echinococcosis, also known has hydatidosis, is a result of ingesting the eggs of the genus Echinococcus. E. vogeli is similar to E. multilocularis in that both species produces many small cysts that spread throughout the internal organs of the infected animal. The ingestion of E. vogeli eggs, and the spreading of the cysts through infected host, will results in Polycystic Echinococcosis.

References

  1. University of Pennsylvania - Veterinary Medicine: Taenia multiceps Homepage Archived 2010-07-10 at the Wayback Machine
  2. University of Pennsylvania - Veterinary medicine: Taenia serialis Homepage Archived 2010-07-10 at the Wayback Machine
  3. Stanford University: Coenurosis - Hosts Archived 2012-10-23 at the Wayback Machine
  4. Stanford University: Taeniasis Archived 2013-07-09 at the Wayback Machine
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