Dipylidium caninum
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p680-682
2025-10-29
57
GENERAL CHARACTERISTICS
D. caninum, the cat or dog tapeworm (Figure 1), is a double-pored tapeworm consisting of many small proglottids. As the tapeworm matures, the proglottids separate and pass in the stool. They may be recognized on the basis of their characteristic “cucumber seed” appearance when they are wet, as well as their resemblance to a dried grain of rice. Adult tapeworms measure 10 to 70 cm in length. The scolex contains four suckers and an armed rostellum. Egg packets may also be found in the feces of the host.
Fig1. Dipylidium caninum tapeworm. (Courtesy Dr. Henry Travers, Sioux Falls, S.D.)
PATHOGENESIS AND SPECTRUM OF DISEASE
Ingestion of an infected flea may result in D. caninum infection. The flea is the intermediate host in which infective cysticercoids develop; humans, dogs, and cats are the reservoir hosts. The larval stage of the egg is ingested by a dog or cat and develops into cysticercoid larvae. The adult worm develops and matures within the reservoir host. An infected human host will usually pass proglottids in a bowel movement or they may stick to the skin around the anal area. Humans usually have very mild symptoms such as indigestion, appetite loss, weight loss, perianal itching, persistent diarrhea, and vague abdominal pain. The severity of the disease is dependent on the worm burden. Human infection is usually self-limited. LABORATORY DIAGNOSIS
Symptoms of Dipylidium infection are similar to those of pinworm infection; however, the treatments are very different. The laboratory should confirm suspected infections. Proglottids (8 to 23 µm) may be seen in the stool. D. caninum is also referred to as the “cucumber seed” tapeworm as previously described (see Figure 2). The first sign of infection may be the appearance of seedlike particles in the stool or undergarments of the patient. These particles are the egg-bearing segments of the tape worm. Groups of egg packets may be found in the stool (Figures 3 and 4). The adult worms have a scolex with four suckers and a conical/retractile rostellum armed with four to seven rows of small hooklets (Figure 5). Patients may also develop a moderately elevated eosinophilia.
Fig2. Proglottid demonstrating rosette-shaped uterus in D. latum. (Courtesy Dr. Henry Travers, Sioux Falls, S.D.)
Fig3. A, Taenia spp. egg. B, Diphyllobothrium latum egg. C, Hymenolepis diminuta egg. D, Hymenolepis nana egg. E, Dipylidium caninum egg packet.
Fig4. Dipylidium caninum egg packet. (Illustration by Nobuko Kitamura.)
Fig5. D. caninum scolex demonstrating the armed rostellum. (Courtesy Dr. Henry Travers, Sioux Falls, SD.)
ANTIPARASITIC SUSCEPTIBILITY TESTING AND THERAPY
D. caninum infection is usually asymptomatic and is self-limiting. When treated, praziquantel is typically effective. The medication causes the tapeworm to dissolve within the intestine. The drugs are generally well tolerated by the patient. Household pets should be treated simultaneously to prevent reinfection.
PREVENTION
To reduce the risk of infection, flea control of pets in the household will reduce exposure to humans via the inter mediate host. To limit the exposure to fleas by household cats, it is recommended to keep cats indoors to prevent infection.
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