Taenia pisiformis

Taenia pisiformis
File:Taenia scolex cropped.jpg
Taenia pisiformis scolex
Scientific classification
Kingdom:	Animalia
Phylum:	Platyhelminthes
Class:	Cestoda
Order:	Cyclophyllidea
Family:	Taeniidae
Genus:	Taenia
Species:	T. pisiformis
Binomial name
Taenia pisiformis Bloch 1780
Synonyms
Taenia novella Nuemann, 1896 Cysticercus pisiformis Zeder, 1803

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 instenstines 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.

Description

T. pisiformis typically infect dogs and other carnivores such as coyotes and foxes. Within rabbits, T. pisiformis larvae attach themselves to the liver and intestines, forming cysts 5–7 mm (0.20–0.28 in) in diameter. This is referred to as cysticercosis.

In adult T. pisiformis, the long hooks of the scolex are on average 239.9 µm (0.00944 in) and the short hooks are 140.1 µm (0.00552 in). The dimensions of the suckers are 322.3 µm × 288.1 µm (0.01269 in × 0.01134 in). They can have from 34 to 38 hooks which can be up to 234 µm (0.0092 in) in length. Adult T. pisiformis can grown between 0.5 to 2 m (20 to 79 in).

The intermediate host is represented by hares and rabbits, in which we find the mesacestoide (the larval stage) known as: cysticercus pisiformis. This is found in the peritoneum of the intermediate host and can be ingested by the definite host when the dog or cat feeds on the viscera of such an infected intermediate.

Life Cycle

Eggs are introduced into the environment through infected canine feces. In the feces are the gravid proglottids that house the T. pisiformis eggs that will eventually be released form the proglottid onto nearby vegetation. The eggs are then ingested by are rabbit or from any member of the Leporidae family. Once inside the rabbits gut the larva or oncosphere phase will then penetrate into the intestinal wall until they reach the blood stream. When the worm reaches the liver the larva transform into a cysticercus form. This cysticercus will stay in the liver for about 2 to 4 weeks and then move to the peritoneal cavity were it will wait for the definitive host to eat the rabbit. The definitive hosts are ether dogs or other members of the Canidae family. Once ingested the cysticercus find its way into the intestine and attached to the intestinal wall with hooks and suckers. After the worm has time to develop and grow in size the gravid proglottids will be released form the distal end of the parasite and passed in feces to start a new cycle.

Adult morphology

The adult stage consists of a scolex with four suckers and an armed rostellum, a short neck region, a series of immature proglottids with undeveloped reproductive organs, a series of mature proglottids with fully developed male and female reproductive organs, and a series of gravid proglottids with an expanded uterus filled with eggs.

Pathology

In rabbits there are not really defined clinical signs seen for any range of intensity expect when there is an externally high intensity. For this case rabbits will appear to look weak or ill. The major illness seen are signs of liver failure. In very few cases the cysts will migrate to the lungs or brain; these cases can cause breathing complication or seizures. In the most extreme cases the rabbit will have sudden death.

For dogs there are normally no clinical signs seen for low to moderate infections. For more highly infected cases the dog will experience blockage in the intestines. In all cases the proglottids will be seen in the feces.

Diagnostic

When looking for signs of infection in the intermediate host or definitive host the signs are not very external seen. For the intermediate host there will be pea-sized cysts can ranging form 2 to 20 cysts found inside the liver. The cysts that are found have one scolex inverted to the middle of the cyst and this shape is called a cysticercus that is part of the metacestodes stage of life. The ones found in the liver form these bladders that are specifically called Cysticercus pisiformis for T. pisiformis. These signs can only be seen when a necropsy is done to the rabbit. When looking for an infection in dogs there is a more strait forward method. There will be gravid proglottids with striated eggs seen in the feces. This can be found using a fecal float on a sample that can easily be done by a vet.

Treatment/Prevention

Taenis pisiformis infection is very hard to treat wild rabbits and canines form but it is easier to control pet infections. One easy way to stop the infection is to prevent dogs form eating wild rabbits or rodents. For is the infected rabbit is not eaten then the worm cant finish its life cycle. Household rabbits usually do not get infected if they are strictly indoor rabbits but infection can happen if they are let outside into open grasses.

If the infection is already present then use one of these drugs; Epsiprantel, Praziquantel, Mebendazole, Niclosamide, Bunamindine hydrochloride or Fenbendazole. This will kill the adult stage but not cyst or egg stage so several treatment times maybe needed. Daily Doses of Praziquantel for about 1 to 2 weeks’ time will be effective to larval cysticercosis in rabbits. While one dose of niclosamide or praziquantel can be very effective in dogs.

Gallery

• Taeniapisiformis.jpg

  Taenia pisiformis cross section.

• Taenia egg.JPG

  Taenia pisiformis egg

• Cysticercus pisiformis.jpg

  Cysticercus pisiformis The larva found in intermediate hosts

• TaeniaPisiformisLabeledProglottid.jpg

  Taenia pisiformis mature proglottid.