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Cestodes - Segmented Flat Worms
Terms in this set (54)
Tapeworms are flat worms that are segmented. They consist of a head (called the scolex), neck, and then a number of segments. The head usually has suckers or muscular grooves that enable the tapeworm to attach itself to the animal's intestine. Each tapeworm segment has its own reproductive organs. New segments are continually formed in the neck region of the worm while those at the end of the tapeworm are cast off as they mature. These mature segments contain large numbers of eggs which are often grouped into packets. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. When the segment drops off, it is basically just a sac of tapeworm eggs.
The segments may often be seen near the anus of the cat or dog. These segments may move if recently passed, or if dried, they look like grains of uncooked rice or cucumber seeds. Tapeworm infections are usually diagnosed by finding these segments on the animal. Tapeworms of cats and dogs all have life cycles that include an intermediate host. These hosts include fleas, fish, and domestic animals such as sheep and pigs. All of the adult forms of these tapeworms live in the cat or dog's digestive system. It is interesting that tapeworms have no digestive systems themselves, but absorb nutrients through their skin. The tapeworm absorbs nutrients as the food being digested by the host flows past it.
Most Common Tapeworms that Infect Cats and Dogs
• Dipylidium caninum
• Taenia species
• Echinococcus granulosus
AKA Flea Tapeworm or Cucumber Seed Tapeworm
Segmented worm. Egg packet segments break off and found in feces or anal area (grains of rice). The entire tapeworm is usually 6 inches or more long, but can be up to 20 inches long.
Fleas - esssential. May also be lice.
Egg packets get passed in feces. Flea larva eats egg, which develops into an immature form in the insect, and dog eats flea. PP. 14-21 days.
Oral ingestion of fleas or lice containing the tape worm larva. Mature tapeworms produce segments containing large numbers of eggs which are often grouped into packets. The packet breaks and tapeworm eggs are released in the environment. These eggs are not infectious to mammals. The tapeworm must reach a specific stage of development in a flea or louse before it is infectious to a mammal.
Clinical Signs in Dogs
None to slight signs - mild weight loss, diarrhea, vague abdominal pain. Possible perianal pruritus with segments visible - "rice grains". The active segments around the anal area may cause an animal to lick or 'scoot' on the floor.
Clinical Signs in Humans
Usually it is children who become infected with this tapeworm by ingesting flea larvae or adult lice. In general, we rarely see symptoms in humans. In severe infections, abdominal discomfort, diarrhea and pruritus (itching) in the perianal area may be present.
Look at segments the owner has found. Egg packets under microscope. gravid proglottids
Analysis of proglottids (often referred to incorrectly as "segments") that are shed from the tapeworm, and these have a characteristic size and shape (more like rice grains than cucumber seeds). Diagnosis of this species depends on finding proglottids or "egg packets" in the feces. Cannot use a fecal float for diagnosis.
Drontal, Fenbendazole, pyrantel pamoate; The most common treatment is praziquantel which is found in Droncit.
Flea prevention and specific deworming that treats tapeworms.
Yes. Have to eat fleas.
Very good probability the pet also has fleas.
Flat segmented worm, passes egg packet segments. Segments are squarish. Tapeworms can grow to be over 6 feet long.
Dog and Cat
Mouse, rabbit, sheep, bird, slug - must have intermediate host.
Egg packets passed - eaten by intermediate host, then host eaten by dog or cat. PP 36-42 days. The intermediate host ingests the eggs which are immediately infective. In the intermediate host, the embryo is released in the small intestine and the immature form migrates through the body to various organs, depending on the species of Taenia. The immature form develops a small fluid-filled sac, called a bladder, which surrounds it and provides nourishment. When the 'bladder' is ingested by the definitive host, the head of the tapeworm is released, attaches itself to the intestinal wall, grows and segments.
Eating intermediate host.
Even in severe infections, there is little evidence of infection other than pruritus around the anal area and finding the segments attached to the animal's fur.
Segments under microscope.
Taenia spp. are more susceptible to antihelmintics than other tapeworms. Effective treatments include Droncit and Cestex.
Deworming. Don't let pets eat raw meats or prey on wild animals.
Humans can get Taenia spp from eating infected pork; not from pets.
Hydatidosis, Hydatid Disease
Echinococcus spp. of tapeworms (Cestodes)
Canid wild animals, domestic dogs and cats. Domestic dogs and cats can become infected with the adult tapeworm when they eat infected wild rodents. Domestic hunting dogs are also definitive hosts, and serve as an important source of human infection.
Dogs & cats serve as the definitive hosts of Echinococcus. Humans can also serve as aberrant intermediate hosts for species of Echinococcus. The infection in humans causes a severe, sometimes fatal disease called 'hydatid disease' or echinococcosis.
An intermediate host (commonly sheep & rodents ) ingests the Echinococcus eggs which are passed in the feces of the definitive host. The eggs hatch and the immature forms penetrate the intestinal wall of the intermediate host and migrate to various organs, usually the lung and liver. Large cysts, 2-5 inches in diameter, develop and contain thousands of infective forms, called 'hydatid sand'. When the cysts are ingested by a definitive host, each of the infective forms contained in the cyst can develop into an adult tapeworm which are usually less than 7 mm long. The adult worms attach themselves to the small intestine and may live there up to two years.
Ingestion of eggs - passed in dog feces. Human infection occurs when eggs passed in dog feces are accidentally swallowed. Eggs are free in feces, not in "egg packets" like the other tapeworm species. This can occur through eating contaminated vegetation such as nuts, berries and herbs. Hands could become contaminated by gardening or otherwise working in soil contaminated with dog, cat, fox or other canid feces.
Forms cysts in body, or affects liver (severe disease). Can remain asymptomatic for 10-20 years.
As with Taenia tapeworms, the definitive hosts rarely show signs of disease unless the tapeworms are present in high numbers. Usually the intermediate hosts do not show signs of infection either. Organs affected: Liver Cyst, Pulmonary Cysts, Brain Cysts, Bone Marrow Cysts. If these cystic structures in a human rupture, anaphylactic shock may occur. The cyst consists of layers and many immature forms which are often called "hydatid sand."
Checking for antigens - looking for cysts - U/S, MRI, etc. The tapeworm eggs are not normally found in fecal floats.
Surgical removal of cysts in humans. Praziquantel (Droncit) in pet infections.
Cysts - 15% of untreated patients eventually die. Alveolar - 90% of untreated die.
Deworm dogs in endemic areas. Good hygiene. Preventing pets from eating intermediate hosts.
How do Humans become Infected with Echinococcus?
Humans become accidentally infected by ingesting food items contaminated with the eggs of Echinococcus. This can occur through eating contaminated vegetation such as nuts, berries, and herbs. Hands could become contaminated by gardening or otherwise working in soil contaminated with cat, dog, fox, or other canid feces. Be sure to wash all fruits and vegetables and wash hands thoroughly with soap and water as well. Signs of infection may not be evident until years after ingestion of the eggs.
What are the Signs of Disease in Humans Infected with Echinococcus?
Humans, unlike animals, often show signs of infection with Echinococcus, and the signs vary depending on the organs infected. Parasitic tumors may develop in the brain, heart, lungs, and liver. If these cystic tumors in a human would rupture, anaphylactic shock may occur. Surgery is often the treatment of choice in humans infected with Echinococcus.
The diagnosis of hydatid disease in humans is often made through sophisticated testing using CAT scans and MRI. Serologic tests are also available.
THIS SET IS OFTEN IN FOLDERS WITH...
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