''Moniliformis moniliformis'' is a parasite of the
Acanthocephala
Acanthocephala (Greek , ', thorn + , ', head) is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to p ...
phylum in the family
Moniliformidae
Moniliformidae is a family of parasitic spiny-headed (or thorny-headed) worms. It is the only family in the Moniliformida order and contains three genera: ''Australiformis'' containing a single species, ''Moniliformis'' containing eighteen spec ...
. The adult worms are usually found in intestines of
rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s or
carnivore
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
s such as cats and dogs. The species can also infest humans, though this is rare.
Distribution
Infested rats have been found world-wide. Cases of human infestation by ''Moniliformis moniliformis'' have been reported in the United States, Iran, Iraq, and Nigeria.
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"Acanthocephalan Worms." Gideon. Gideon Informatics. Web.
Morphology
Acanthocephalans do not have
digestive tract
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 a ...
s and absorb nutrients through the
tegument, the external layer. The
scolex
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 ...
of this worm has a cylindrical
proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
and a multitude of curved hooks. The main parts of the worm body are the proboscis, neck, and trunk. Because of horizontal markings on the worm, there is the appearance of segmentation. Acanthocephalans are sexually dimorphic (
dioecious
Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...
) – adult males are generally 4 to 5 cm long while females are longer, ranging from lengths of 10 to 30 cm. Males also have
copulatory bursas, used to hold on to the female during copulation and
cement glands. Females have
floating ovaries
Floating may refer to:
* a type of dental work performed on horse teeth
* use of an isolation tank
* the guitar-playing technique where chords are sustained rather than scratched
* Floating (play), ''Floating'' (play), by Hugh Hughes
* Floating (p ...
within a
ligament sac where
fertilization of the eggs occurs.
"Phylum: Acanthocephala." Lecture. Animal Parasitology. Kansas State, 14 March 2005. Web. 23 February 2010. The eggs of this parasite are 90–125 μm long and 65 μm wide. They are oval in shape with a thick, clear outer coat.
Acanthocephaliasis. Parasites and Health. CDC, 20 July 2009. Web.
Reservoirs
Usually, the definitive hosts for ''M. moniliformis'' are
rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s,
cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s,
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s and
red fox
The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the Order (biology), order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe ...
es (in
Poland
Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populous ...
); human infestations are rare. The intermediate hosts are usually
beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s and
cockroach
Cockroaches (or roaches) are a paraphyletic group of insects belonging to Blattodea, containing all members of the group except termites. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known as ...
es.
Life cycle
In the life cycle of ''M. moniliformis'', the intermediate hosts ingest the eggs of the parasite. In the intermediate host, the acanthor, or the parasite in its first larval stage, morphs into the acanthella, the second larval stage. After 6–12 weeks in this stage, the acanthella becomes a cystacanth. The cystacanth, or infective acanthella, of ''M. moniliformis'' are cyst-shaped and encyst in the tissues of the intermediate hosts. However, most other acanthocephalans have infective larvae that more closely resemble underdeveloped adult worms. The definitive hosts consume the cystacanths upon feeding on infested intermediate hosts. These cystacanths mature and mate in the small intestine in 8–12 weeks. After this time, the eggs are excreted with the feces, to be ingested yet again by another intermediate host and renew this cycle.
The reproduction of the parasite only occurs in the definitive host. In acanthocephalans, adult males have cement glands in their posterior ends. The widely held theory is that the mucilaginous and proteinaceous substance that these glands secrete is used by males to seal up the females after copulation in order to prevent leakage of the inseminated sperm and further insemination by other males. It has also been found that these males may create this seal on other males in order to prevent them from copulating.
[Crompton, D.W.T. Reproduction. In Biology of the Acanthocephala (ed. Crompton, D. W. T. & Nickol, B. B.), pp. 213–271. Cambridge University Press, Cambridge. 1985] These seals, or copulatory caps, last for a week.
Behavioral changes in the intermediate host
In what is commonly known as "brain-jacking", the parasite induces a behavioral change in its intermediate host that increases the risk of predation for the host. It is thought that this behavioral change holds an evolutionary advantage for the parasite by increasing its chances of getting to its definitive host. When ''M. moniliformis'' infests its intermediate host, the cockroach species ''
Periplaneta americana
The american cockroach (''Periplaneta americana'') is the largest species of common cockroach, and often considered a pest. In certain regions of the U.S. it is colloquially known as the waterbug, though it is not a true waterbug since it is not ...
'', it changes the cockroach's escape response. In one study, it was concluded that cockroaches infected by ''M. moniliformis'' took longer to respond to wind stimuli simulating the approach of a potential predator and displayed fewer escape responses implying that the parasite infection renders its intermediate host more vulnerable to predation by hindering its ability to detect and escape from its predator. It is thought that serotonin plays a role in upending the communication between giant interneurons and the thoracic interneurons and in turn hampers the escape response of the cockroach.
In a similar study, the effects of parasitism on three ''
Periplaneta
''Periplaneta'' is a genus of cockroaches.
Selected species
Species include:
* '' Periplaneta aboriginea'' Roth, 1994
* ''Periplaneta americana'' (Linnaeus, 1758) – American cockroach
* '' Periplaneta australasiae'' (Fabricius, 1775) – Aust ...
'' species are studied. The results show that ''
Periplaneta australasiae
The Australian cockroach (''Periplaneta australasiae'') is a common species of tropical cockroach, with a length of .
It is brown overall, with the tegmina having a conspicuous lateral pale stripe or margin, and the pronotum (head shield) with a ...
'' uses substrates differently and moves around less when infected with ''Moniliformis moniliformis''.
Another study concludes an increased vulnerability of infected ''Periplaneta americana'' due to increased phototaxis, more time spent moving (due to slower movement) and movement in response to light (uninfected cockroaches hesitated before moving).
Human infection
As it requires consumption of raw infested beetles or cockroaches, human acanthocephaliasis is rare.
Clinical manifestations
In 1888 in Italy, infected himself by ingesting larvae, reported gastrointestinal disturbances, and then shed the eggs in two weeks. This was the first report of the clinical manifestations of an ''M. moniliformis'' infestation in humans.
Calandruccio provided the first description of the clinical manifestations of acanthocephaliasis and similar accounts are found in the few case studies since; many of the patients described were asymptomatic. When they showed symptoms, they normally experienced abdominal pain, diarrhea, dizziness, edema, and anorexia.
In some patients, giddiness has also been reported.
In rodents, acanthocephaliasis is fatal and manifests itself through hemorrhaging and gastrointestinal disturbance.
Diagnosis
The proper diagnosis of acanthocephaliasis in humans is made through fecal analysis, which, if the host is infested, should contain adult worms or eggs. To obtain the worms from the host,
piperazine citrate
Piperazine () is an organic compound that consists of a six-membered ring containing two nitrogen atoms at opposite positions in the ring. Piperazine exists as small alkaline deliquescent crystals with a saline taste.
The piperazines are a broad ...
,
levamisole
Levamisole, sold under the brand name Ergamisol among others, is a medication used to treat parasitic worm infections, specifically ascariasis and hookworm infections. It is taken by mouth.
Side effects may include abdominal pain, vomiting, ...
and
bithionol
Bithionol is an antibacterial, anthelmintic, and algaecide. It is used to treat '' Anoplocephala perfoliata'' (tapeworms) in horses and ''Fasciola hepatica'' (liver flukes).
__TOC__ Mechanism of action
Bithionol has been shown to be a potent in ...
can be administered to the patient.
Treatment
Acanthocephaliasis is treated with anti-helminthics. There is considerable debate over the efficacy of anti-helminth drugs on this parasite but, so far, the drugs seem to be working.
Pyrantel pamoate
Pyrantel is a medication used to treat a number of parasitic worm infections. This includes ascariasis, hookworm infections, enterobiasis (pinworm infection), trichostrongyliasis, and trichinellosis. It is taken by mouth.
Side effects include n ...
and
ivermectin
Ivermectin (, '' EYE-vər-MEK-tin'') is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, today it is used to treat inf ...
have been shown to be particularly effective in treating patients.
Mebendazole
Mebendazole (MBZ), sold under the brand name Vermox among others, is a medication used to treat a number of parasitic worm infestations. This includes ascariasis, pinworm infection, hookworm infections, guinea worm infections, hydatid disease, ...
and
thiabendazole
Tiabendazole (INN, BAN), also known as thiabendazole (AAN, USAN) or TBZ and the trade names Mintezol, Tresaderm, and Arbotect, is a preservative, an antifungal agent, and an antiparasitic agent.
Uses
Preservative
Tiabendazole is used primar ...
have also both been cited to work.
Prevention strategies
Because the only way of developing acanthocephaliasis is through ingesting the intermediate hosts, the most effective means of prevention is avoiding the consumption of uncooked beetles and cockroaches. This is especially difficult in children exhibiting pica and in areas with poor hygiene. Awareness campaigns on the risks of consuming infested beetles and cockroaches would be effective. Moreover, preventing entry of the intermediate hosts into the home, and especially the kitchen where it is at risk of getting into the food, would help curb the risk of becoming infested.
References
{{DEFAULTSORT:Moniliformis Moniliformis
Archiacanthocephala
Animals described in 1811