Common name. Dog tapeworm, cucumber tapeworm
Geographic distribution. A cosmopolitan parasite of dogs and cats. Human cases have been reported in the European, the Latin American, the East Asian, the South African countries, and in the United States.
Infection rate. D. caninum is common in dogs and cats, children are infected occasionally.
Life cycle. When the eggs are ingested by intermediate host-the larvae of the flea or the dog louse-the oncospheres hatch, penetrate into the gut, and develop into cysticercoids in about 2 weeks. When the infected flea or louse is ingested by a final host, i.e., dogs, foxes, jackals, hyenas, cats, and humans, the cysticercoids mature into adults in the small intestine in about 20 days. The eggs and gravid proglottids are expelled in the feces.
Morphology. Adult worms measure 10-70 cm in length, and 2-3 mm in width. The scolex has four suckers with 40-60 hooklets arranged in 3-5 rows around the rostellum. Immature proglottids are trapezoidal, become progressively long with rounded sides toward the posterior end. Mature proglottids contain two sets of reproductive organs with a genital pore on each lateral margin. In the gravid proglottid, eggs are enclosed by thin sacs to form egg-capsules or egg-ball. The eggs are spherical, measuring 40-50 ㎛ in diameter. The oncosphere is covered by a thin eggshell and an embryophore.
Pathology and clinical symptoms. Most infected persons are asymptomatic. Severe infection may cause indigestion, abdominal pain, diarrhea, anal pruritus, and nervous symptoms.
Diagnosis. Diagnosis depends on the recovery and identification of gravid proglottids or egg-balls in the stool.
Prevention. Pets should be kept free of the parasites. The insects should be adequately controlled. The children must be taken precautions.
Comments. Free eggs without sac should be differentiated from the eggs of Hymenolepis diminuta.
An egg ball(or egg sac) of Dipylidium caninum.
Tai Soon Yong
A mature proglottid of Dipylidium caninum contains bilaterally two sets of reproductive system. x100.