Page 139 - Medical Parasitology_ A Textbook ( PDFDrive )

132 11 Cestodes: Tapeworms

(4) Human can also acquire infection by ingesting embryonated eggs from contami-
nated food, water, or via contaminated hands. (5) The egg hatches and releases
oncosphere which develops into cysticercoid in the intestinal villus. (6–7) The larva
breaks out of the villus in the lumen of the small intestine and grows into an adult
worm. The scolex of the adult worm attaches to the ileal portion of the small intes-
tine. (8) Eggs are released by the gravid proglottids and are passed out in faeces.

Pathogenesis and Clinical Features
Hymenolepiasis is usually asymptomatic but in heavy infections, patients may pres-
ent with nausea, anorexia, abdominal pain, diarrhoea and irritability. Anal pruritus
may be due to an allergic response.

Diagnosis
1. Microscopic examination
Detection of characteristic eggs in faeces.

Treatment
Praziquantel (25 mg/kg in a single-dose therapy) is the drug of choice. It acts both
against the adult worms and the cysticercoids in the intestinal villi. Alternative drug
is nitazoxanide.

Prevention and Control
1. Personal hygiene
2. Proper sanitation
3. Avoid consumption of contaminated food and water by flea or beetles
4. Rodent control

Hymenolepis diminuta

Its common name is rat tapeworm and is a common parasite of rats and mice. It
measures 10–60 cm in length. Its eggs are bigger than that of H. nana and it has no
polar filaments. Its life cycle is similar to that of the murine strain of H. nana.
Human infection follows accidental ingestion of infected rat fleas. Most infections
are asymptomatic. Occasionally, patients may complain of mild gastrointestinal
symptoms.

Dipylidium caninum

Distribution
This common double-pore tapeworm of dogs and cats may cause human infection,
mainly in children. It is distributed globally.