Spirometra
Encyclopedia
Spirometra is a genus
of Pseudophyllid
cestode that reproduces in canines
and feline
s but which can cause pathology in humans. As an adult, this tapeworm lives in the small intestine
of its definitive host and produces eggs that pass with the animal's feces
. The eggs hatch into coracidia which are eaten by copepod
s which become infected themselves. In the copepod, the worm forms a procercoid, which is infective to vertebrate
s that ingest them. Often, because the copepods are so small, vertebrates ingest copepods accidentally by drinking them. In the vertebrate, the worms enter the plerocercoid
stage. The plerocercoids pass through several paratenic
hosts before reaching a suitable definitive host where it can mature. Once eaten by a canid or felid, the tapeworm matures and begins producing eggs. Theoretically, a canid or felid that ate an infected human could become infected.
In paratenic hosts (any vertebrate infected but a canid or felid), plerocercoids move to subcutaneous tissue
s and the eye
from the small intestine, causing pain, edema
, and inflammation
. A few humans have died from this kind of infection, called sparaganosis. The only way to treat this condition is with surgery.
Infection of humans may be prevented by avoiding uncooked meat
, infected water, and poultices. It is also known to infect rat
s.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of Pseudophyllid
Pseudophyllidea
Pseudophyllid cestodes are a kind of flatworm with multiple "segments" and two bothria or "sucking grooves" as adults...
cestode that reproduces in canines
Canidae
Canidae is the biological family of carnivorous and omnivorous mammals that includes wolves, foxes, jackals, coyotes, and domestic dogs. A member of this family is called a canid . The Canidae family is divided into two tribes: Canini and Vulpini...
and feline
Felidae
Felidae is the biological family of the cats; a member of this family is called a felid. Felids are the strictest carnivores of the thirteen terrestrial families in the order Carnivora, although the three families of marine mammals comprising the superfamily pinnipedia are as carnivorous as the...
s but which can cause pathology in humans. As an adult, this tapeworm lives in the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
of its definitive host and produces eggs that pass with the animal's feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
. The eggs hatch into coracidia which are eaten by copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s which become infected themselves. In the copepod, the worm forms a procercoid, which is infective to vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s that ingest them. Often, because the copepods are so small, vertebrates ingest copepods accidentally by drinking them. In the vertebrate, the worms enter the plerocercoid
Plerocercoid
Plerocercoid refers to last larval form found in the second intermediate host of many Cestoda with aquatic life cycles....
stage. The plerocercoids pass through several paratenic
Paratenic
In parasitology, the term paratenic describes a host which is not needed for the development of the parasite, but nonetheless serves to maintain the life cycle of the parasite. Alaria americana may serve as an example: the so-called mesocercarial stages of this parasite reside in tadpoles, which...
hosts before reaching a suitable definitive host where it can mature. Once eaten by a canid or felid, the tapeworm matures and begins producing eggs. Theoretically, a canid or felid that ate an infected human could become infected.
In paratenic hosts (any vertebrate infected but a canid or felid), plerocercoids move to subcutaneous tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
s and the eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
from the small intestine, causing pain, edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
, and inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
. A few humans have died from this kind of infection, called sparaganosis. The only way to treat this condition is with surgery.
Infection of humans may be prevented by avoiding uncooked meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...
, infected water, and poultices. It is also known to infect rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s.