Dipylidium caninum

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Dipylidium caninum
Dipyl can worm1.JPG
Adult Dipylidium caninum. The scolex of the worm is very narrow and the proglottids get larger as they mature
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestoda
Order: Cyclophyllidea
Family: Dipylidiidae
Genus: Dipylidium
Species:
D. caninum
Binomial name
Dipylidium caninum
(Linnaeus, 1758)
Synonyms
  • Dipylidium carracidoiLopez-Neyra, 1929
  • Taenia caninaLinnaeus, 1758
  • Taenia cucumerinaBloch, 1782
Dipylidium life cycle Dipylidium LifeCycle.png
Dipylidium life cycle

Dipylidium caninum, also called the flea tapeworm , double-pored tapeworm, or cucumber tapeworm (in reference to the shape of its cucumber-seed-like proglottids, though these also resemble grains of rice or sesame seeds) is a cyclophyllid cestode that infects organisms afflicted with fleas and canine chewing lice, including dogs, cats, and sometimes human pet-owners, especially children.

Contents

Adult morphology

The adult worm is about 18 inches (46 cm) long. Gravid proglottids containing the worm's microscopic eggs are either passed in the definitive host's feces or may leave their host spontaneously and are then ingested by microscopic flea larvae (the intermediate hosts) in the surrounding environment. As in all members of family Dipylidiidae, proglottids of the adult worm have genital pores on both sides (hence the name double-pore tapeworm). Each side has a set of male and female reproductive organs. The uterus is paired with 16 to 20 radial branches each. The scolex has a retractable rostellum with four rows of hooks, along with the four suckers that all cyclophyllid cestodes have. Adult worm scolex is rhomboidal in shape with a transverse diameter of 250-500um.

Life cycle

The definitive host within this life cycle is primarily canines, and occasionally felines, and in rare cases young children. The intermediate hosts include fleas (Ctenocephalides spp.) and chewing lice. The first stage in the life cycle is when the gravid proglottids are either passed out through faecal matter, or actively crawl out of the anus of the host. The gravid proglottids once out of the definitive host release eggs. Then, an intermediate host (the larval stage of a flea or chewing louse) will ingest an egg, which develops into a cysticercoid larva. The cysticercoid larva remains viable, but is not infective to carnivores until the flea hatches to an adult and begins feeding on a host (e.g. a dog). Approximately 36 hours after the flea has consumed a blood meal, the infective metacestode develops inside the flea. The metacestode larva must be ingested in a flea by the dog or cat during grooming in order to develop. Humans can also become infected by D. caninum by accidentally ingesting an infected flea. In the small intestine of the definitive host, the metacestode develops into an adult tapeworm, which reaches maturity 4–6 weeks after ingestion. This adult tapeworm produces proglottids, and over time, the proglottids mature and become gravid and eventually detach from the tapeworm and the life cycle starts all over again. [1]

Geographic distribution

This parasite occurs worldwide in animals, such as dogs and cats, as well as in humans, though to a significantly lesser degree. It is the most common tapeworm of dogs and is relatively common in cats. Despite human diplydiasis being rare, instances have been reported from every inhabited continent. [2]

Human instances of diplydiasis are reported globally, and unsurprisingly roughly one third of the cases occur in children less than 6 months of age. The most at-risk age group is those that range from 2 months to 4 years old.   [3]

Pet infections

Tapeworm infection usually does not cause pathology in the dog or cat, and most pets show no adverse reaction to infection other than increased appetite. The bulk of infections are asymptomatic and the infections that do result in symptoms are generally mildly so. Pets behavior may reflect the presence of anal discomfort and itching, or pruritus. This could result in the ‘butt-scooching” across the floor, grass or carpeting. It may be accompanied by slight gastrointestinal disturbances, as this is the region where the worms inhabit. Though not a pathology of the diplydiasis, the most unnerving sign of the infection is the presence of proglottids in the animals, or child's, feces.  These proglottids can also be found near the perianal region, in the feces, and in diapers (children). The motile proglottids can actively crawl out of the anus of the infected animal/person and migrate small distances, thus potentially covering this array of neighboring surfaces.  It is from these locations that the larval stage of the flea will come along and ingest them. Then the metacestode stage, a cysticercoid, develops in the coelomic cavity (abdominal cavity; main body cavity) of the flea larvae and remains there as the flea matures into an adult. These freshly passed proglottids are motile, allowing them to also be found on the floor and furniture, from a migration out of a pets anus and could be compared to resembling fly larvae, or maggots. [2] [4]

The other tapeworm infecting cats is Taenia taeniaeformis , though this form is much less commonly encountered than D. caninum.

A recent (2018) study using genetical analysis and experimental infections and life-cycles showed that two different distinct genotypes of D. caninum occur respectively in dogs and in cats, and suggested that two different species might be involved. [5] [6]

Human infections

A human infection with D. caninum is rare, but if an infection does occur, it is more likely to occur in young children. As of the early 1960s, the number of cases of D. caninum in the U.S. was a mere 21. Therefore, human infection of Dipylidium caninum, or diplydiasis, is a rare occasion. It is largely agreed across the parasitology community that despite the reports of this disease occurring, there are very likely numerous cases that have gone unnoticed and unreported because of its subtle and minor pathology in humans, in addition to its scarceness in clinical records. The adult tapeworm grows within the host for 3–4 weeks after initial infection.  The number of parasites the host is initially infected with is directly related to the number of cysticercoid juveniles present in the fleas coelom. The load of parasites present in the humans is lower, luckily, as the life cycle is not occurring in the ideal conditions or species as humans are not the definitive host. [7]

Many cases have an unexciting course of infection, as can be depicted in two cases occurring in the 1960s. The first case occurred in a 9-month-old female. Mother found motile proglottids the child's diaper, later identified as D. caninum. The child had no apparent signs or symptoms. The presumed source of infections was one of the family's  four Labrador retrievers, two of which were found to already have been infected with D. caninum. The second additional case occurred in an 18-month-old male. Mother found motile proglottids in the child's diaper and again, the child was symptom-free.  A puppy in the household was found to be infected and thus was the source of the child infection. [8] Young children and toddlers are at a greater risk of infection because of how they interact with their pets. A human may attain an infection by accidentally ingesting an infected flea through food contamination or through the saliva of pets. Most infections are asymptomatic, but sometimes these symptoms may be identified in an infected individual: mild diarrhea, abdominal colic, anorexia, restlessness, constipation, rectal itching, and pain due to emerging proglottids through the anal cavity. [9]

Treatment and prevention

As with most tapeworm infections, the drugs of choice to kill adult tapeworms are praziquantel or niclosamide. Pets can be prevented from becoming infested with tapeworm if they are treated prophylactically with a product which kills the intermediate host (the flea) before the infective metacestode can develop. Some isoxazoline products are registered to prevent flea tapeworm infestations using this method.

Related Research Articles

<span class="mw-page-title-main">Hymenolepiasis</span> Medical condition

Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease.

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

Taenia is the type genus of the Taeniidae family of tapeworms. It includes some important parasites of livestock. Members of the genus are responsible for taeniasis and cysticercosis in humans, which are types of helminthiasis belonging to the group of neglected tropical diseases. More than 100 species are recorded. They are morphologically characterized by a ribbon-like body composed of a series of segments called proglottids; hence the name Taenia. The anterior end of the body is the scolex. Some members of the genus Taenia have an armed scolex ; of the two major human parasites, Taenia saginata has an unarmed scolex, while Taenia solium has an armed scolex.

<i>Taenia saginata</i> Species of flatworm

Taenia saginata, commonly known as the beef tapeworm, is a zoonotic tapeworm belonging to the order Cyclophyllidea and genus Taenia. It is an intestinal parasite in humans causing taeniasis and cysticercosis in cattle. Cattle are the intermediate hosts, where larval development occurs, while humans are definitive hosts harbouring the adult worms. It is found globally and most prevalently where cattle are raised and beef is consumed. It is relatively common in Africa, Europe, Southeast Asia, South Asia, and Latin America. Humans are generally infected as a result of eating raw or undercooked beef which contains the infective larvae, called cysticerci. As hermaphrodites, each body segment called proglottid has complete sets of both male and female reproductive systems. Thus, reproduction is by self-fertilisation. From humans, embryonated eggs, called oncospheres, are released with faeces and are transmitted to cattle through contaminated fodder. Oncospheres develop inside muscle, liver, and lungs of cattle into infective cysticerci.

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

Echinococcus granulosus, also called the hydatid worm or dog tapeworm, is a cyclophyllid cestode that dwells in the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes cystic echinococcosis, also known as hydatid disease. The adult tapeworm ranges in length from 3 mm to 6 mm and has three proglottids ("segments") when intact—an immature proglottid, mature proglottid and a gravid proglottid. The average number of eggs per gravid proglottid is 823. Like all cyclophyllideans, E. granulosus has four suckers on its scolex ("head"), and E. granulosus also has a rostellum with hooks. Several strains of E. granulosus have been identified, and all but two are noted to be infective in humans.

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

Echinococcus multilocularis, the fox tapeworm, is a small cyclophyllid tapeworm found extensively in the northern hemisphere. E. multilocularis, along with other members of the Echinococcus genus, produce diseases known as echinococcosis. Unlike E. granulosus,E. multilocularis produces many small cysts that spread throughout the internal organs of the infected animal. The resultant disease is called alveolar echinococcosis, and is caused by ingesting the eggs of E. multilocularis.

<i>Hymenolepis nana</i> Species of flatworm

Dwarf tapeworm is a cosmopolitan species though most common in temperate zones, and is one of the most common cestodes infecting humans, especially children.

<i>Hymenolepis diminuta</i> Species of flatworm

Hymenolepis diminuta, also known as rat tapeworm, is a species of Hymenolepis tapeworm that causes hymenolepiasis. It has slightly bigger eggs and proglottids than H. nana and infects mammals using insects as intermediate hosts. The adult structure is 20 to 60 cm long and the mature proglottid is similar to that of H. nana, except it is larger.

<i>Taenia pisiformis</i> Species of flatworm

Taenia pisiformis, commonly called the rabbit tapeworm, is an endoparasitic tapeworm which causes infection in lagomorphs, rodents, and carnivores. Adult T. pisiformis typically occur within the small intestines of the definitive hosts, the carnivores. Lagomorphs, the intermediate hosts, are infected by fecal contamination of grasses and other food sources by the definitive hosts. The larval stage is often referred to as Cysticercus pisiformis and is found on the livers and peritoneal cavities of the intermediate hosts. T. pisiformis can be found worldwide.

<span class="mw-page-title-main">Eucestoda</span> Subclass of flatworms

Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda. Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodaria. All tapeworms are endoparasites of vertebrates, living in the digestive tract or related ducts. Examples are the pork tapeworm with a human definitive host, and pigs as the secondary host, and Moniezia expansa, the definitive hosts of which are ruminants.

Spirometra erinaceieuropaei is a parasitic tapeworm that infects domestic animals and humans. The medical term for this infection in humans and other animals is sparganosis. Morphologically, these worms are similar to other worms in the genus Spirometra. They have a long body consisting of three sections: the scolex, the neck, and the strobilia. They have a complex life cycle that consists of three hosts, and can live in varying environments and bodily tissues. Humans can contract this parasite in three main ways. Historically, humans are considered a paratenic host; however, the first case of an adult S. erinaceieuropaei infection in humans was reported in 2017. Spirometra tapeworms exist worldwide and infection is common in animals, but S. erinaceieuropaei infections are rare in humans. Treatment for infection typically includes surgical removal and anti-worm medication.

<i>Hymenolepis</i> (flatworm) Genus of worms

Hymenolepis is a genus of cyclophyllid tapeworms that cause hymenolepiasis. They parasitise mammals, including humans. Some notable species are:

<i>Toxascaris leonina</i> Species of roundworm

Toxascaris leonina is a common parasitic roundworm found in dogs, cats, foxes, and related host species. T. leonina is an ascarid nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts of T. leonina include canids and felines (cats), while the intermediate hosts are usually rodents, such as mice or rats. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.

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

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 many similar units known as proglottids—essentially packages of eggs which are regularly shed into the environment to infect other organisms. Species of the other subclass, Cestodaria, are mainly fish infecting parasites.

Diphyllobothrium mansonoides is a species of tapeworm (cestodes) that is endemic to North America. Infection with D. mansonoides in humans can result in sparganosis. Justus F. Mueller first reported this organism in 1935. D. mansonoides is similar to D. latum and Spirometra erinacei. When the organism was discovered, scientist did not know if D. mansonoides and S. erinacei were separate species. PCR analysis of the two worms has shown the two to be separate but closely related organisms.

<i>Taenia taeniaeformis</i> Species of flatworm

Taenia taeniaeformis is a parasitic tapeworm, with cats as the primary definitive hosts. Sometime dogs can also be the definitive host. The intermediate hosts are rodents and less frequently lagomorphs (rabbits). The definitive host must ingest the liver of the intermediate host in order to acquire infection. The worm tends to be white, thick bodied, and around 15 to 60 cm in length. This species of tape worm is much less frequently encountered than Dipylidium caninum, which has fleas as its intermediate host rather than rodents but exhibits most of the same physical characteristics and is treated with the same medications.

Bertielliasis is the infection of Bertiella, a cestode tapeworm parasite that primarily infects nonhuman primates, rodents and Australian marsupials. Occasionally, human infections have been documented by one of two species: Bertiella studeri, or Bertiella mucronata. Of 29 different Bertiella species, only these two can infect humans.

<i>Taenia hydatigena</i> Species of flatworm

Taenia hydatigena is one of the adult forms of the canine and feline tapeworm. This infection has a worldwide geographic distribution. Humans with taeniasis can infect other humans or animal intermediate hosts by eggs and gravid proglottids passed in the feces.

<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 result in polycystic echinococcosis.

Joyeuxiella pasquale is a species of flatworm, belonging to the family Dipylidiidae. The species uses coprophagous beetles and reptiles as transportation hosts with dogs, cats, and other wild carnivores being their final carrier for reproduction.

<span class="mw-page-title-main">Cat worm infections</span> Worm infections in cats

Cat worm infections, the infection of cats (Felidae) with parasitic worms, occur frequently. Most worm species occur worldwide in both domestic and other cats, but there are regional, species and lifestyle differences in the frequency of infestation. According to the classification of the corresponding parasites in the zoological system, infections can be divided into those caused by nematode and flatworms - in the case of the latter, mainly cestoda and trematoda - while other strains are of no veterinary significance. While threadworms usually do not require an intermediate host for their reproduction, the development cycle of flatworms always proceeds via alternate hosts.

References

  1. ↑ "Dipylidium caninum Infection". Centers for Disease Control and Prevention. Retrieved 24 April 2015.
  2. 1 2 "CDC - DPDx - Dipylidium caninum". www.cdc.gov. 2019-07-10. Retrieved 2020-05-07.
  3. ↑ Neira O, Patricia; Jofré M, Leonor; Muñoz S, Nelson (December 2008). "Infección por Dipylidium caninum en un preescolar: Presentación del caso y revisión de la literatura". Revista chilena de infectología. 25 (6). doi: 10.4067/S0716-10182008000600010 . ISSN   0716-1018.
  4. ↑ Prevention, CDC-Centers for Disease Control and (31 May 2023). "CDC - Dipylidium". www.cdc.gov. Retrieved 18 August 2023.
  5. ↑ Labuschagne, Michel; Beugnet, Frédéric; Rehbein, Steffen; Guillot, Jacques; Fourie, Josephus; Crafford, Dionne (2018). "Analysis of Dipylidium caninum tapeworms from dogs and cats, or their respective fleas. Part 1. Molecular characterization of Dipylidium caninum: genetic analysis supporting two distinct species adapted to dogs and cats". Parasite. 25: 30. doi:10.1051/parasite/2018028. PMC   6013089 . PMID   29806592. Open Access logo PLoS transparent.svg
  6. ↑ Beugnet, Frédéric; Labuschagne, Michel; Vos, Christa de; Crafford, Dionne; Fourie, Josephus (2018). "Analysis of Dipylidium caninum tapeworms from dogs and cats, or their respective fleas. Part 2. Distinct canine and feline host association with two different Dipylidium caninum genotypes". Parasite. 25: 31. doi:10.1051/parasite/2018029. PMC   6013090 . PMID   29806593. Open Access logo PLoS transparent.svg
  7. ↑ Bowman DD. Georgis‘Parasitology for Veterinarians. Sixth edition Philadelphia. PA: Saunders Company; 1995:145–6
  8. ↑ Thompson, James H. (1963). "Human Dipylidium caninum Infection". The Journal of Parasitology. 49 (3): 402. doi:10.2307/3275807. ISSN   0022-3395. JSTOR   3275807.
  9. ↑ Garcia-Martos, Pedro; Garcia-Agudo, Lidia; Rodriguez-Iglesias, Manuel (26 May 2014). "Dipylidium caninum infection in an infant: a rare case report and literature review" (PDF). Asian Pacific Journal of Tropical Biomedicine. 4 (2): S565–S567. doi: 10.12980/APJTB.4.2014APJTB-2014-0034 . Archived from the original on 18 May 2015. Retrieved 20 September 2016.{{cite journal}}: CS1 maint: bot: original URL status unknown (link)
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