Hymenolepis nana (dwarf tapeworm)
Jump to navigation
Jump to search
Epidemiology
- world-wide distribution
- most frequently recovered cestode species in USA
- common parasite in mice
- humans may acquire infection by ingestion of
- infectious eggs
- intermediate hosts (generally grain beetles) containing infectious cysticercoid larva
- fleas can also serve as intermediate hosts[3]
Pathology
- ingested eggs hatch in intestine
- embryos penetrate the mucosa where they mature as cysticercoid larva
- cysticercoid emerge from the mucosa, attach to the intestinal wall & develop into adult tapeworms in 2-3 weeks
- adults may attain length of 4 cm
- scolex has armed rostellum
- proglottids have genital pores on the same side of strobila
- autoinfection may occur in some individuals
Clinical manifestations
- may be asymptomatic
- abdominal pain, diarrhea, anorexia, irritability may develop in patients with large tapeworm loads
Laboratory
- diagnosis is made by recovery of eggs in the feces
- oval, thin-shelled & colorless
- 30-47 um in diameter
- contain a centrally located 6-hooked embryo (oncosphere) separated from the outer shell by a clear space
- embryo displays 2 polar thickenings from which thin filaments arise & extend into the clear space between the embryo & the outer shell
- strobila may occasionally be recovered from feces
Complications
- malignant transformation of H nana invading human host as metastatic cancer in an HIV1 infected patient[4]
Management
- praziquantel 25 mg/kg PO once
- treatment of choice
- active against both adult worm & cysticercoids in intestinal villi
- niclosamide
- 2 g PO day 1, then 1 g PO QD for 6 days
- active against both adult worm; ineffective against cysticercoids
- personal hygiene & improved sanitation
More general terms
Additional terms
- cysticercoid
- flea (Siphonaptera)-borne infection
- hexacanth (oncosphere)
- proglottid
- rostellum
- scolex
- strobila
References
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 1288-89
- ↑ Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 933
- ↑ 3.0 3.1 Wkipedii: Hymenolepis nana http://en.wikipedia.org/wiki/Hymenolepis_nana
- ↑ 4.0 4.1 Muehlenbachs A et al Malignant Transformation of Hymenolepis nana in a Human Host. N Engl J Med 2015; 373:1845-1852. November 5, 2015 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/26535513 <Internet> http://www.nejm.org/doi/full/10.1056/NEJMoa1505892
- ↑ Grimm L What's Eating You: 12 Common Intestinal Parasites. Medscape. November 25, 2019 https://reference.medscape.com/slideshow/intestinal-parasites-6010996