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| ==Causes, incidence, and risk factors==
| | #redirect[[Hymenolepis infection]] |
| [[Image:H nana LifeCycle.gif|right|thumb|Life cycle of ''H. nana.'' Click to enlarge.]] | |
| ''Hymenolepis'' worms live in warm climates and are common in the southern [[USA]]. The eggs of these worms are ingested by [[insects]], and mature into a life form referred to as a "[[cysticercoid]]" in the insect. In ''H. nana,'' the insect is always a beetle.
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| Humans and other animals become infected when they intentionally or unintentionally eat material contaminated by insects. In an infected person, it is possible for the worm's entire life-cycle to be completed in the bowel, so infection can persist for years.
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| ''Hymenolepis nana'' infections are much more common than ''Hymenolepis diminuta'' infections in humans because, in addition to being spread by insects, the disease can be spread directly from person to person by eggs in feces. When this happens, ''H. nana'' [[oncosphere]] larvae encyst in the intestinal wall and develop into cysticercoids and then adults. These infections were previously common in the southeastern USA, and have been described in crowded environments and individuals confined to institutions. However, the disease occurs throughout the world. ''H. nana'' infections can grow worse over time because, unlike in most tapeworms, ''H. nana'' eggs can hatch and develop without ever leaving the [[definitive host]].
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| A study in [[Connecticut]] found that one third of [[rat]]s sold in pet stores were infected with ''H. nana'' and concluded that these and other rodents sold in pet stores pose a potential threat to public health.
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| == Screening for activity against H. nana==
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| H. nana in mice
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| Used because
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| - Human infection—easily maintained in mice
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| - Armed scolex similar to other pathogenic tapeworms
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| - Corresponds to other tapeworms in its sensitivity to standard anthelmintics
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| Methods
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| Mature worms collected from infected mice
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| Terminal gravid proglottids removed, crushed under coverslip—eggs removed
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| Eggs containing hooklets (mature) counted
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| 0.2 ml stock soln. containing 1000 eggs/ml given to each mouse.
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| Adult worm develops- 15-17 days.
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| Test drug given orally – autopsied on 3rd day
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| Std. drug given
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| Intestine examined under dissecting microscope for worms/ scolex
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| Response – no. of mice cleared.
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| ==Symptoms==
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| It is not clear that hymenolepiasis necessarily have any symptoms. The symptoms of hymenolepiasis are traditionally described as abdominal pain, loss of appetite ([[anorexia (symptom)|anorexia]]), itching around the anus, irritability and [[diarrhea]]. However, in one study of 25 patients conducted in Peru, successful treatment of the infection made no significant difference to symptoms.<ref name="Chero2007">{{cite journal | author=Chero JC, Saito M, Bustos JA, ''et al.'' | title=''Hymenolepis nana'' infection: symptoms and response to nitazoxanide in field conditions. | journal=Trans R Soc Trop Med Hyg | year=2007 | volume=101 | issue=2 | pages=203–5 | doi=10.1016/j.trstmh.2006.04.004 }}</ref> Some authorities report that heavily infected cases are more likely to be symptomatic.<ref>{{cite journal | author=Chitchang S, Plamjinda T, Yodmani B, Radomyos P. | year=1985 | title=Relationship between severity of the symptom and the number of ''Hymenolepis nana'' after treatment. | journal=J Med Assoc Thai | volume=68 | pages=423–26 }}</ref><ref>{{cite journal | author=Schantz PM. | year=1996 | title=Tapeworm (cestodiasis). | journal=Gastroenterol Clin North Am | volume=25 | pages=637–53 }}</ref>
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| ==Signs and tests==
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| Examination of the stool for eggs and parasites confirms the diagnosis. The eggs and [[proglottid]]s of ''H. nana'' are smaller than ''H. diminuta.'' Proglottids of both are relatively wide and have three [[testes]]. Identifying the parasites to the species level is often unnecessary from a medical perspective, as the treatment is the same for both.
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| ==Treatment==
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| [[Praziquantel]] as a single dose (25 mg/kg) is the current treatment of choice for hymenolepiasis and has an efficacy of 96%. Single dose [[albendazole]] (400 mg) is also very efficacious (>95%). [[Niclosamide]] has also been used.
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| A three-day course of [[nitazoxanide]] is 75–93% efficacious. The dose is 1g daily for adults and children over 12; 400mg daily for children aged 4 to 11 years; and 200mg daily for children aged 3 years or younger.<ref name="Chero2007"/><ref>{{cite journal | author=Ortiz JJ, Favennec L, Chegne NL, Gargala G. | year=2002 | title=Comparative clinical studis of nitazoxanide, albendazole and praziquantel in the treatment of ascariasis, trichuriasis, and hymenolepiasis in children from Peru | journal=Trans R Soc Trop med Hyg | volume=96 | pages=193–96 | id=PMID 12055813 }}</ref><ref>{{cite journal | author=Reomero-Cabello R, Guerro LR, Munez-Gracia MR, Geyne Cruz A. | year=1997 | title=Nitazoxanide for the treatment of intestinal protozoan and helminthic infections in México. | journal=Trans R Soc Trop Med Hyg | volume=91 | pages=701–3 }}</ref>
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| ==Prognosis==
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| Cure rates are extremely good with modern treatments, but it is unclear that successful cure results in any symptomatic benefit to patients.<ref name="Chero2007"/>
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| ==Complications==
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| * [[abdominal discomfort]]
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| * [[dehydration]] from prolonged diarrhea
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| ==Prevention ==
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| Good hygiene, public health and sanitation programs, and elimination of rats help prevent the spread of hymenolepiasis.
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| ==Source==
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| * [http://www.nlm.nih.gov/medlineplus/ency/article/001378.htm Hymenolepiasis]. Medline Plus.
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| ==References==
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| <references/>
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| {{Helminthiases}}
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| [[Category:Parasitic diseases]]
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| [[fr:Hymenolepis nana]]
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| [[it:Hymenolepis nana]]
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| [[pl:Hymenolepioza]]
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| {{WikiDoc Sources}}
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