Coenurosis

Coenurosis.

Introduction

Coenurosis is a parasitic infection that results when humans accidently 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 disease rarely seen in humans, coenurosis. (7)

It is important to distinguish that there is a very significant difference between human tapeworm 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 CNS, muscle, and subcutaneous tissues of infected humans. People with coenurosis will never develop a tapeworm infection because the larvae of coenurosis-causing parasites cannot develop into worms inside of humans. Below is a picture of the larval cysts.

Agent (classification and taxonomy)

Common Name: Tapeworm larvae infection.

Kingdom: Animalia

Phylum: Platyhelminths

Class: Cestoda

Order: Cyclophyllidea

Family: Taeniidae

Genus: Taenia

Species: multiceps, serialis, brauni, glomerata

Synonyms

Sometimes referred to as Taenia multiceps, or any of the other species names.

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 (1):

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. (2) (4)

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. (3) (2)

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. (7)

When the cyst occurs in the spinal chord, 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. (3) (2)

Transmission

As I mentioned above, 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 infectedcanid. 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. (2)

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