Raillietina echinobothrida
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''Raillietina echinobothrida'' is a parasitic tapeworm belonging to the
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...
Cestoda. It is the most prevalent and pathogenic helminth parasite in
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
, particularly in domestic fowl, '' Gallus domesticus'' Linnaeus,
1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of Systema Naturae, 10th edition of ''Systema Naturae'', the sta ...
. It requires two
hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...
, birds and ants, for completion of its life cycle. It is a
hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...
worm having both the male and female reproductive organs in its body. The parasite is responsible for 'nodular tapeworm disease' in poultry.


Description

The body of an adult ''R. echinobothrida'' is a characteristic tapeworm structure, composed of a series of ribbon-like body segments, gradually enlarging from the anterior end towards the posterior. It is whitish in colour, highly elongated,
dorsoventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
ly flattened, and entirely covered with a
tegument Tegument may refer to: * Integumentary system, a protective organ system forming the outermost layer of an animal's body * Tegument (helminth) Tegument is a term in helminthology for the outer body covering of members of the phylum Platyhelminthe ...
. The body can be as long as 25 cm, and generally 1–1.5 cm broad. The body is divisible into the head region called ' scolex', followed by an unsegmented 'neck', and then by highly segmented body proper called ' strobila'. The scolex bears four suckers and a rostellum, which are the organs of attachment to the host. Individual segments in the strobila are called '
proglottids Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of man ...
' and are entirely covered with hair-like ' microtriches'. These microtriches are the absorptive structures for feeding, and there are no
digestive organs The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...
. A number of testes and a pair ovaries are present in each proglottid. Each mature body segment contains 8-12 egg capsules.


Life cycle

It completes its life cycle in two different hosts. The adult life is spent in the
intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...
of fowl, which is the definitive host, and
juvenile Juvenile may refer to: *Juvenile status, or minor (law), prior to adulthood *Juvenile (organism) *Juvenile (rapper) (born 1975), American rapper * ''Juvenile'' (2000 film), Japanese film * ''Juvenile'' (2017 film) *Juvenile (greyhounds), a greyho ...
period is in ant, particularly the species of '' Tetramorium'', which is the intermediate host.
Gravid proglottid Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of man ...
s containing a large number of egg capsules are passed out to the exterior with the
feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
of infested chicken. Each egg capsule in turn contains 3 to 8 eggs. The larvae called onchospheres are
ingest Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms ingesti ...
ed by ants, and enters the
alimentary canal The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...
, from where they migrate into the abdominal cavity of the insect and develop into mature cysticercoids, the infective larvae to birds.


Pathogenicity and pathology

The adult parasite infects the small intestine of fowl, from where it obtains nutrition from the digested food of the host. The tapeworm is responsible for stunted growth of young chicken, emaciation of adult and decreased egg production of hen. In general the tapeworm does not cause gross pathological damages on well-nourished chicken, but do compete for food when they grow to excessive number. In such situation, severe lesions on the intestinal walls and diarrhoea could arise, which ostensibly resulted in ill health. Under heavy infestation, ''R. echinobothrida'' is listed as one of the most pathogenic tapeworms, causing conspicuous intestinal
nodules Nodule may refer to: *Nodule (geology), a small rock or mineral cluster *Manganese nodule, a metallic concretion found on the seafloor *Nodule (medicine), a small aggregation of cells *Root nodule Root nodules are found on the roots of plants, p ...
in chicken, with characteristic hyperplastic enteritis associated with the formation of
granuloma A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious ...
. The symptom is termed “nodular tapeworm disease” in poultry. Intestinal nodules often result in degeneration and
necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
of intestinal villi, accompanied by anaemia with a significant increase of total
leukocyte White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...
counts and decrease of total
serum Serum may refer to: *Serum (blood), plasma from which the clotting proteins have been removed **Antiserum, blood serum with specific antibodies for passive immunity * Serous fluid, any clear bodily fluid * Truth serum, a drug that is likely to mak ...
protein. The nodules can measure up to 6 mm in diameter, which can be seen as rugged swellings on autopsy, and often cause
catarrh Catarrh is an exudate of inflamed mucous membranes in one of the airways or cavities of the body, usually with reference to the throat and paranasal sinuses. It can result in a thick exudate of mucus and white blood cells caused by the swelling o ...
and enteritis.


Treatment

There is no prescription drug for the parasite. Naturally infected hens were dewormed completely in 24 hours using mebendazole orally at doses 25 mg/kg body weight and higher, without apparent
sideeffect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
. Albendazole was shown to be highly effective and is advocated as the drug of choice.


References


External links


BioLibZipcodeZooAustralian Faunal DirectoryGalapagos Species ChecklistClassification on Encyclopedia of LifeFauna Europaea
{{Taxonbar, from=Q7284031 Cestoda Animals described in 1880 Parasites of birds